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Sample records for broadband time-resolved spectroscopy

  1. Broadband THz waveguiding and high-precision broadband time-resolved spectroscopy

    DEFF Research Database (Denmark)

    Cooke, David; Iwaszczuk, Krzysztof; Nielsen, Kristian

    2009-01-01

    , have tailored dispersion and may be bent into sharp bends. Due to the confinement of the THz field in the core of the fibers they are ideal for stable guiding of THz light in confined environments, and may serve as a useful basis for a wealth of fiber-based photonic components in the THz range......We demonstrate optical fibers designed for the THz frequency range, fabricated in a low-loss polymer. The polymer fibers display a broadband loss of 0.4 dB/cm over the 0.1-1 THz range, with a minimum loss of 0.1 dB/cm in the region near 500 GHz. The fibers, based on endlessly single-mode design......, particularly in spectroscopic applications where tight confinement of the THz field is required. We further demonstrate a new spectroscopic technique for ultrafast time-resolved THz time-domain spectroscopy which simultaneously acquires both reference and sample data. By using this scheme we show...

  2. Broad-band time-resolved near infrared spectroscopy in the TJ-II stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, M.C.; Pastor, I.; Cal, E. de la; McCarthy, K.J. [Laboratorio Nacional de Fusion, CIEMAT, Madrid (Spain); Diaz, D. [Universidad Autonoma de Madrid, Dept Quimica Fisica Aplicada, Madrid (Spain)

    2014-11-15

    First experimental results on broad-band, time-resolved Near Infrared (NIR;here loosely defined as covering from 750 to 1650 nm) passive spectroscopy using a high sensitivity InGaAs detector are reported for the TJ-II Stellarator. Experimental set-up is described together with its main characteristics, the most remarkable ones being its enhanced NIR response, broadband spectrum acquisition in a single shot, and time-resolved measurements with up to 1.8 kHz spectral rate. Prospects for future work and more extended physics studies in this newly open spectral region in TJ-II are discussed. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

    Energy Technology Data Exchange (ETDEWEB)

    Sheps, Leonid; Chandler, David W.

    2013-04-01

    Experimental measurements of elementary reaction rate coefficients and product branching ratios are essential to our understanding of many fundamentally important processes in Combustion Chemistry. However, such measurements are often impossible because of a lack of adequate detection techniques. Some of the largest gaps in our knowledge concern some of the most important radical species, because their short lifetimes and low steady-state concentrations make them particularly difficult to detect. To address this challenge, we propose a novel general detection method for gas-phase chemical kinetics: time-resolved broadband cavity-enhanced absorption spectroscopy (TR-BB-CEAS). This all-optical, non-intrusive, multiplexed method enables sensitive direct probing of transient reaction intermediates in a simple, inexpensive, and robust experimental package.

  4. Time-resolved vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tokmakoff, Andrei [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Champion, Paul [Northeastern Univ., Boston, MA (United States); Heilweil, Edwin J. [National Inst. of Standards and Technology (NIST), Boulder, CO (United States); Nelson, Keith A. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Ziegler, Larry [Boston Univ., MA (United States)

    2009-05-14

    This document contains the Proceedings from the 14th International Conference on Time-Resolved Vibrational Spectroscopy, which was held in Meredith, NH from May 9-14, 2009. The study of molecular dynamics in chemical reaction and biological processes using time-resolved spectroscopy plays an important role in our understanding of energy conversion, storage, and utilization problems. Fundamental studies of chemical reactivity, molecular rearrangements, and charge transport are broadly supported by the DOE's Office of Science because of their role in the development of alternative energy sources, the understanding of biological energy conversion processes, the efficient utilization of existing energy resources, and the mitigation of reactive intermediates in radiation chemistry. In addition, time-resolved spectroscopy is central to all fiveof DOE's grand challenges for fundamental energy science. The Time-Resolved Vibrational Spectroscopy conference is organized biennially to bring the leaders in this field from around the globe together with young scientists to discuss the most recent scientific and technological advances. The latest technology in ultrafast infrared, Raman, and terahertz spectroscopy and the scientific advances that these methods enable were covered. Particular emphasis was placed on new experimental methods used to probe molecular dynamics in liquids, solids, interfaces, nanostructured materials, and biomolecules.

  5. Time resolved spectroscopy of shock compressed liquids

    Science.gov (United States)

    Ogilvie, K.; Duvall, G. E.

    1982-04-01

    An experimental procedure has been developed for using a rotating mirror camera to record time-resolved absorption spectra of liquids undergoing shock compression. Experimental records have been obtained for cells containing liquid carbon disulfide shocked, through reverberation, to peak pressures of 55, 80, 100 and 120 kbar. Experiments have been performed using both reflected and transmitted light. Time and spectral resolution were limited to approximately 30 nsec and 30 Å; spectral range was from 4000 to 2500 Å. This initial work on carbon disulfide shows it to become highly absorptive when shocked to low pressures of 8 to 14 kbar, and to progressively become a better broadband reflector as the pressure in a thin layer rings up to the final value. A decay in the reflectivity after reaching peak pressure in the 120 kbar experiment may indicate chemical decomposition. This is in accord with earlier results of S. A. Sheffield based on measurement of flow parameters.

  6. Time Resolved Broadband Terahertz Relaxation Dynamics of Electron in Water

    DEFF Research Database (Denmark)

    Wang, Tianwu; Iwaszczuk, Krzysztof; Cooke, David G.

    We investigated the transient response of the solvated electron in water ejected by photodetachment from potassium ferrocyanide using time resolved terahertz spectroscopy (TSTS). Ultrabroadband THz transients are generated and detected by a two-color femtosecond-induced air plasma and air biased...... coherent detection, respectively. We find that the measured frequency dependent conductivity can be well described by a Drude-Smith model, supplemented by a Lorentz model oscillating near 5 THz....

  7. Mobile charge generation dynamics in P3HT: PCBM observed by time-resolved terahertz spectroscopy

    DEFF Research Database (Denmark)

    Cooke, D. G.; Krebs, Frederik C; Jepsen, Peter Uhd

    2012-01-01

    Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale.......Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale....

  8. Thymine Dimer Formation probed by Time-Resolved Vibrational Spectroscopy

    Science.gov (United States)

    Schreier, Wolfgang J.; Schrader, Tobias E.; Roller, Florian O.; Gilch, Peter; Zinth, Wolfgang; Kohler, Bern

    Cyclobutane pyrimidine dimers are the major photoproducts formed when DNA is exposed to UV light. Femtosecond time-resolved vibrational spectroscopy reveals that thymine dimers are formed in thymidine oligonucleotides in an ultrafast photoreaction.

  9. Time-resolved terahertz spectroscopy in a parallel-plate waveguide

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    Time-resolved THz spectroscopy is a powerful tool to investigate photoconductivity dynamics in a wide variety of materials with sub-picosecond resolution, all without applying contacts to the material. This technique uses coherently detected and broadband pulses of far-infrared light, known as TH...

  10. Seventh international conference on time-resolved vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, R.B.; Martinez, M.A.D.; Shreve, A.; Woodruff, W.H. [comps.

    1997-04-01

    The International Conference on Time-Resolved Vibrational Spectroscopy (TRVS) is widely recognized as the major international forum for the discussion of advances in this rapidly growing field. The 1995 conference was the seventh in a series that began at Lake Placid, New York, 1982. Santa Fe, New Mexico, was the site of the Seventh International Conference on Time-Resolved Vibrational Spectroscopy, held from June 11 to 16, 1995. TRVS-7 was attended by 157 participants from 16 countries and 85 institutions, and research ranging across the full breadth of the field of time-resolved vibrational spectroscopy was presented. Advances in both experimental capabilities for time-resolved vibrational measurements and in theoretical descriptions of time-resolved vibrational methods continue to occur, and several sessions of the conference were devoted to discussion of these advances and the associated new directions in TRVS. Continuing the interdisciplinary tradition of the TRVS meetings, applications of time-resolved vibrational methods to problems in physics, biology, materials science, and chemistry comprised a large portion of the papers presented at the conference.

  11. Time-Resolved Spectroscopy in Complex Liquids An Experimental Perspective

    CERN Document Server

    Torre, Renato

    2007-01-01

    Time-Resolved Spectroscopy in Complex Liquids introduces current state-of-the-art techniques in the study of complex dynamical problems in liquid phases. With a unique focus on the experimental aspects applied to complex liquids, this volume provides an excellent overview into the quickly emerging field of soft-matter science. Researchers and engineers will find a comprehensive review of current non-linear spectroscopic and optical Kerr effect techniques, in addition to an in-depth look into relaxation dynamics in complex liquids. This volume offers current experimental findings in transient grating spectroscopy and their application to viscoelastic phenomena in glass-formers, dynamics of confined liquid-crystals, and a time-resolved analysis of the host-quest interactions of dye molecules in liquid-crystal matter. Time-Resolved Spectroscopy in Complex Liquids provides a cohesive introduction suitable for individuals involved in this emerging field, complete with the latest experimental procedures of complex ...

  12. Time-resolved THz spectroscopy in a parallel plate waveguide

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    We demonstrate time-resolved terahertz spectroscopy inside a novel parallel plate waveguide where one of the metallic plates is replaced by a transparent conducting oxide. Considerable improvements to the waveguide loss coefficient are shown, with a power absorption coefficient of 4cm-1 at 0.5 THz...

  13. Time-resolved terahertz spectroscopy of semiconductor nanostructures

    DEFF Research Database (Denmark)

    Porte, Henrik

    This thesis describes time-resolved terahertz spectroscopy measurements on various semiconductor nanostructures. The aim is to study the carrier dynamics in these nanostructures on a picosecond timescale. In a typical experiment carriers are excited with a visible or near-infrared pulse and by me......This thesis describes time-resolved terahertz spectroscopy measurements on various semiconductor nanostructures. The aim is to study the carrier dynamics in these nanostructures on a picosecond timescale. In a typical experiment carriers are excited with a visible or near-infrared pulse...... and by measuring the transmission of a terahertz probe pulse, the photoconductivity of the excited sample can be obtained. By changing the relative arrival time at the sample between the pump and the probe pulse, the photoconductivity dynamics can be studied on a picosecond timescale. The rst studied semiconductor...... be signicantly reduced. Besides time-resolved terahertz spectroscopy measurement, optical transmission, Raman spectroscopy, scanning electron microscope, energy dispersive X-ray, and X-ray diffraction spectroscopy experiments on black silicon are presented....

  14. Time resolved spectroscopy of GRB 030501 using INTEGRAL

    DEFF Research Database (Denmark)

    Beckmann, V.; Borkowski, J.; Courvoisier, T.J.L.

    2003-01-01

    The gamma-ray instruments on-board INTEGRAL offer an unique opportunity to perform time resolved analysis on GRBs. The imager IBIS allows accurate positioning of GRBs and broad band spectral analysis, while SPI provides high resolution spectroscopy. GRB 030501 was discovered by the INTEGRAL Burst...... Alert System in the ISGRI field of view. Although the burst was fairly weak (fluence F20-200 keV similar or equal to 3.5x10(-6) erg cm(-2)) it was possible to perform time resolved spectroscopy with a resolution of a few seconds. The GRB shows a spectrum in the 20-400 keV range which is consistent...

  15. Time-resolved Raman spectroscopy for in situ planetary mineralogy.

    Science.gov (United States)

    Blacksberg, Jordana; Rossman, George R; Gleckler, Anthony

    2010-09-10

    Planetary mineralogy can be revealed through a variety of remote sensing and in situ investigations that precede any plans for eventual sample return. We briefly review those techniques and focus on the capabilities for on-surface in situ examination of Mars, Venus, the Moon, asteroids, and other bodies. Over the past decade, Raman spectroscopy has continued to develop as a prime candidate for the next generation of in situ planetary instruments, as it provides definitive structural and compositional information of minerals in their natural geological context. Traditional continuous-wave Raman spectroscopy using a green laser suffers from fluorescence interference, which can be large (sometimes saturating the detector), particularly in altered minerals, which are of the greatest geophysical interest. Taking advantage of the fact that fluorescence occurs at a later time than the instantaneous Raman signal, we have developed a time-resolved Raman spectrometer that uses a streak camera and pulsed miniature microchip laser to provide picosecond time resolution. Our ability to observe the complete time evolution of Raman and fluorescence spectra in minerals makes this technique ideal for exploration of diverse planetary environments, some of which are expected to contain strong, if not overwhelming, fluorescence signatures. We discuss performance capability and present time-resolved pulsed Raman spectra collected from several highly fluorescent and Mars-relevant minerals. In particular, we have found that conventional Raman spectra from fine grained clays, sulfates, and phosphates exhibited large fluorescent signatures, but high quality spectra could be obtained using our time-resolved approach.

  16. Time-resolved photoluminescence spectroscopy of organic-plasmonic hybrids

    DEFF Research Database (Denmark)

    Leißner, Till; Brewer, Jonathan R.; Fiutowski, Jacek

    We study the optical properties of organic thin films and crystalline organic nanofibers as well as their interaction with plasmonic materials by means of laser-scanning fluorescence lifetime imaging microscopy (FLIM) and time-resolved photoluminescence spectroscopy (TR-PLS). The aim of our...... research is to understand and developed organic-plasmonic hybrid systems with tailored optical and plasmonic properties such as wave-guiding, enhance second-harmonic response and lasing. We are able to image, gather information about the fundamental coupling mechanism, as well as study charge...

  17. Examining Electron-Boson Coupling Using Time-Resolved Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sentef, Michael; Kemper, Alexander F.; Moritz, Brian; Freericks, James K.; Shen, Zhi-Xun; Devereaux, Thomas P.

    2013-12-26

    Nonequilibrium pump-probe time-domain spectroscopies can become an important tool to disentangle degrees of freedom whose coupling leads to broad structures in the frequency domain. Here, using the time-resolved solution of a model photoexcited electron-phonon system, we show that the relaxational dynamics are directly governed by the equilibrium self-energy so that the phonon frequency sets a window for “slow” versus “fast” recovery. The overall temporal structure of this relaxation spectroscopy allows for a reliable and quantitative extraction of the electron-phonon coupling strength without requiring an effective temperature model or making strong assumptions about the underlying bare electronic band dispersion.

  18. Time-resolved vibrational spectroscopy of a molecular shuttle.

    Science.gov (United States)

    Panman, Matthijs R; Bodis, Pavol; Shaw, Danny J; Bakker, Bert H; Newton, Arthur C; Kay, Euan R; Leigh, David A; Buma, Wybren Jan; Brouwer, Albert M; Woutersen, Sander

    2012-02-14

    Time-resolved vibrational spectroscopy is used to investigate the inter-component motion of an ultraviolet-triggered two-station molecular shuttle. The operation cycle of this molecular shuttle involves several intermediate species, which are observable in the amide I and amide II regions of the mid-IR spectrum. Using ab initio calculations on specific parts of the rotaxane, and by comparing the transient spectra of the normal rotaxane with that of the N-deuterated version, we can assign the observed vibrational modes of each species occurring during the shuttling cycle in an unambiguous way. The complete time- and frequency-dependent data set is analyzed using singular value decomposition (SVD). Using a kinetic model to describe the time-dependent concentrations of the transient species, we derive the absorption spectra associated with each stage in the operation cycle of the molecular shuttle, including the recombination of the charged species.

  19. Time resolved spectroscopy and lifetime measurements of single semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Robert; Krasselt, Cornelius; Borczyskowski, Christian von [TU Chemnitz (DE). Institute of Physics, Department of Optical Spectroscopy and Molecular Physics (OSMP), NanoMA

    2010-07-01

    The photoluminescence of single emitters like semiconductor quantum dots (QDs) shows intermittency, called blinking, which divides the intensity time traces into bright ''on''-, dark ''off''-and intermediate-states. The distribution of ''off''-times shows power law behavior with an exponential decay. While the power law behavior of ''off''-times is well understood, it is less evident for ''on''-times. We investigate the blinking-dynamics of CdSe/ZnS-nanocrystals using time resolved confocal microscopy, spectroscopy and lifetime measurements. The intensity time traces are analysed with special focus on intermediate intensities, by varying the threshold separating the on- and off- from intermediate-states. Further the intensity time traces are compared with spectral- and lifetime- time traces in order to obtain correlations between intensities, lifetimes and spectral positions. We report new insights into the intrinsic dynamics of QD.

  20. Time-resolved diffuse optical spectroscopy of small tissue samples

    Science.gov (United States)

    Taroni, Paola; Comelli, Daniela; Farina, Andrea; Pifferi, Antonio; Kienle, Alwin

    2007-07-01

    Time-resolved transmittance measurements were performed in the wavelength range of 610 or 700 to 1050 nm on phantom slabs and bone tissue cubes of different sizes. The data were best fitted with solutions of the diffusion equation for an infinite slab and for a parallelepiped to investigate how size and optical properties of the samples affect the results obtained with the two models. When small samples are considered, the slab model overestimates both optical coefficients, especially the absorption. The parallelepiped model largely compensates for the small sample size and performs much better also when the absorption spectra are interpreted with the Beer's law to estimate bone tissue composition.

  1. Time-resolved reflectance spectroscopy for nondestructive assessment of fruit and vegetable quality

    Science.gov (United States)

    Torricelli, Alessandro; Spinelli, Lorenzo; Vanoli, Maristella; Rizzolo, Anna; Eccher Zerbini, Paola

    2007-09-01

    In the majority of food and feed, due to the microscopic spatial changes in the refractive index, visible (VIS) and near infrared (NIR) light undergoes multiple scattering events and the overall light distribution is determined more by scattering rather than absorption. Conventional steady state VIS/NIR reflectance spectroscopy can provide information on light attenuation, which depends both on light absorption and light scattering, but cannot discriminate these two effects. On the contrary, time-resolved reflectance spectroscopy (TRS) provides a complete optical characterisation of diffusive media in terms of their absorption coefficient and reduced scattering coefficient. From the assessment of the absorption and reduced scattering coefficients, information can then be derived on the composition and internal structure of the medium. Main advantages of the technique are the absolute non-invasiveness, the potentiality for non-contact measurements, and the capacity to probe internal properties with no influence from the skin. In this work we review the physical and technical issues related to the use of TRS for nondestructive quality assessment of fruit and vegetable. A laboratory system for broadband TRS, based on tunable mode-locked lasers and fast microchannel plate photomultiplier, and a portable setup for TRS measurements, based on pulsed diode lasers and compact metal-channel photomultiplier, will be described. Results on broadband optical characterisation of fruits and applications of TRS to the detection of internal defects in pears and to maturity assessment in nectarines will be presented.

  2. Time-resolved terahertz spectroscopy of charge carrier dynamics in the chalcogenide glass As30Se30Te40 [Invited

    DEFF Research Database (Denmark)

    Wang, Tianwu; Romanova, Elena A.; Abdel-Moneim, Nabil

    2016-01-01

    Broadband (1.6-18 THz) terahertz time-domain spectroscopy (THz-TDS) and time-resolved terahertz spectroscopy (TRTS) were performed on a 54 mu m thick chalcogenide glass (As30Se30Te40) sample with a two-color laser-induced air plasma THz system in transmission and reflection modes, respectively. Two...... by the Drude-Smith conductivity model with a carrier scattering time of 12-17 fs, and we observe significant carrier localization effects. A fast refractive index change was observed 100 fs before the conductivity reached its maximum, with 2 orders of magnitude larger amplitude than expected for the optically...

  3. A high accuracy broadband measurement system for time resolved complex bioimpedance measurements.

    Science.gov (United States)

    Kaufmann, S; Malhotra, A; Ardelt, G; Ryschka, M

    2014-06-01

    Bioimpedance measurements are useful tools in biomedical engineering and life science. Bioimpedance is the electrical impedance of living tissue and can be used in the analysis of various physiological parameters. Bioimpedance is commonly measured by injecting a small well known alternating current via surface electrodes into an object under test and measuring the resultant surface voltages. It is non-invasive, painless and has no known hazards. This work presents a field programmable gate array based high accuracy broadband bioimpedance measurement system for time resolved bioimpedance measurements. The system is able to measure magnitude and phase of complex impedances under test in a frequency range of about 10-500 kHz with excitation currents from 10 µA to 5 mA. The overall measurement uncertainties stay below 1% for the impedance magnitude and below 0.5° for the phase in most measurement ranges. Furthermore, the described system has a sample rate of up to 3840 impedance spectra per second. The performance of the bioimpedance measurement system is demonstrated with a resistor based system calibration and with measurements on biological samples.

  4. Time-resolved photoelectron spectroscopy and ab initio multiple spawning studies of hexamethylcyclopentadiene

    DEFF Research Database (Denmark)

    Wolf, T. J. A.; Kuhlman, Thomas Scheby; Schalk, O.

    2014-01-01

    Time-resolved photoelectron spectroscopy and ab initio multiple spawning were applied to the ultrafast non-adiabatic dynamics of hexamethylcyclopentadiene. The high level of agreement between experiment and theory associates wavepacket motion with a distinct degree of freedom.......Time-resolved photoelectron spectroscopy and ab initio multiple spawning were applied to the ultrafast non-adiabatic dynamics of hexamethylcyclopentadiene. The high level of agreement between experiment and theory associates wavepacket motion with a distinct degree of freedom....

  5. Time-resolved spectroscopy of low-pressure discharges

    Energy Technology Data Exchange (ETDEWEB)

    Huldt, S; Lennartsson, T [Lund Observatory, Lund University, Box 43, SE-221 00 Lund (Sweden)], E-mail: Sven.huldt@astro.lu.se

    2008-10-15

    Optical emission spectroscopy is used to investigate the excitation mechanisms in fluorescent tube plasmas. The temporal evolution of the intensities in the non-equilibrium parts of a pulse-excited rare gas - Hg mixture is recorded. Different transitions in a specific atomic system, as well as transitions from upper level of comparable excitation energy in different species, show distinctly different intensity build-up at the onset of the excitation, as well as varying decay characteristics in the afterglow after turning the excitation off. This implies different mechanisms for populating the excited level. The work of modelling the observations is in progress but hampered by the lack of adequate data for many of the important processes.

  6. Time-resolved spectroscopy of low-pressure discharges

    Science.gov (United States)

    Huldt, S.; Lennartsson, T.

    2008-10-01

    Optical emission spectroscopy is used to investigate the excitation mechanisms in fluorescent tube plasmas. The temporal evolution of the intensities in the non-equilibrium parts of a pulse-excited rare gas - Hg mixture is recorded. Different transitions in a specific atomic system, as well as transitions from upper level of comparable excitation energy in different species, show distinctly different intensity build-up at the onset of the excitation, as well as varying decay characteristics in the afterglow after turning the excitation off. This implies different mechanisms for populating the excited level. The work of modelling the observations is in progress but hampered by the lack of adequate data for many of the important processes.

  7. Time-resolved photoelectron spectroscopy using synchrotron radiation time structure.

    Science.gov (United States)

    Bergeard, N; Silly, M G; Krizmancic, D; Chauvet, C; Guzzo, M; Ricaud, J P; Izquierdo, M; Stebel, L; Pittana, P; Sergo, R; Cautero, G; Dufour, G; Rochet, F; Sirotti, F

    2011-03-01

    Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera-based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photoemitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station.

  8. Time-resolved products observed from high pressure deflagrating energetic materials using femtosecond IR spectroscopy

    Science.gov (United States)

    Zaug, J. M.; Glascoe, E. A.; Crowhurst, J. C.; Fried, L. E.; Armstrong, M. R.; Grant, C. D.

    2007-06-01

    What transient chemical species occur on the nanosecond to microsecond time-scale after an energetic material begins to deflagrate under Chapman-Jouguet conditions? What are the molecular lifetimes of transient species under similar conditions? Using ultrafast infrared spectroscopy to study the transient chemical phenomena of materials encapsulated in high-pressure diamond anvils cells (DACs), these and related questions can be addressed. Here we present a broadband time-resolved IR (TRIR) absorption technique applied to high-pressure deflagrating energetic materials. A 10 nanosecond laser pulse is introduced onto the surface of a high-pressure energetic material. After an induction period of approximately one microsecond the energetic material begins to deflagrate (1500+K) at subsonic velocities radially away from the laser ignited region. A mid-IR femtosecond laser pulse (pulse-gated, 2-10 micron tunable range) is transmitted through the deflagration front. The single-shot mid-IR absorbance is used to detect transient species. Our measurements provide a rigorous test of computational chemistry models.

  9. Time-resolved terahertz spectroscopy of conjugated polymer/CdSe nanorod composites

    DEFF Research Database (Denmark)

    Cooke, David; Lek, Jun Y.; Krebs, Frederik C

    2010-01-01

    report ultrafast carrier dynamics in hybrid CdSe nanorod / poly(3-hexythiophene) (P3HT) bulk heterojunction films measured by time-resolved terahertz spectroscopy, and compare to the well studied P3HT/phenyl-C61-butyric acid methyl ester (PCBM) blend. Both films show an improved peak photoconduct......report ultrafast carrier dynamics in hybrid CdSe nanorod / poly(3-hexythiophene) (P3HT) bulk heterojunction films measured by time-resolved terahertz spectroscopy, and compare to the well studied P3HT/phenyl-C61-butyric acid methyl ester (PCBM) blend. Both films show an improved peak...

  10. [A method for time-resolved laser-induced breakdown spectroscopy measurement].

    Science.gov (United States)

    Pan, Cong-Yuan; Han, Zhen-Yu; Li, Chao-Yang; Yu, Yun-Si; Wang, Sheng-Bo; Wang, Qiu-Ping

    2014-04-01

    Laser-Induced Breakdown Spectroscopy (LIBS) is strongly time related. Time-resolved LIBS measurement is an important technique for the research on laser induced plasma evolution and self-absorption of the emission lines. Concerning the temporal characteristics of LIBS spectrum, a method is proposed in the present paper which can achieve micros-scale time-resolved LIBS measurement by using general ms-scale detector. By setting different integration delay time of the ms-scale spectrum detector, a series of spectrum are recorded. And the integration delay time interval should be longer than the worst temporal precision. After baseline correction and spectrum fitting, the intensity of the character line was obtained. Calculating this intensity with differential method at a certain time interval and then the difference value is the time-resolved line intensity. Setting the plasma duration time as X-axis and the time-resolved line intensity as Y-axis, the evolution curve of the character line intensity can be plotted. Character line with overlap-free and smooth background should be a priority to be chosen for analysis. Using spectrometer with ms-scale integration time and a control system with temporal accuracy is 0.021 micros, experiments carried out. The results validate that this method can be used to characterize the evolution of LIBS characteristic lines and can reduce the cost of the time-resolved LIBS measurement system. This method makes high time-resolved LIBS spectrum measurement possible with cheaper system.

  11. Chilling injury in stored nectarines and its detection by time-resolved reflectance spectroscopy

    NARCIS (Netherlands)

    Lurie, S.; Vanoli, M.; Dagar, A.; Weksler, A.; Eccher Zerbini, P.C.; Spinelli, L.; Torricelli, A.; Lovati, F.; Feng, R.; Rizzolo, A.

    2011-01-01

    Nectarine fruit after cold storage soften normally, but become dry instead of juicy and can develop flesh browning, bleeding and a gel-like or glassy formation of the flesh near the pit. An experiment was conducted to see if time-resolved reflectance spectroscopy could distinguish these internal

  12. Simultaneous reference and differential waveform acquisition in time-resolved terahertz spectroscopy

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Cooke, David; Fujiwara, Masazumi

    2009-01-01

    We present a new method for data acquisition in time-resolved terahertz spectroscopy experiments. Our approach is based on simultaneous collection of reference and differential THz scans. Both the optical THz generation beam and the pump beam are modulated at two different frequencies that are no...

  13. Time-resolved VUV spectroscopy in the EXTRAP-T2 reversed field pinch

    Science.gov (United States)

    Hedqvist, Anders; Rachlew-Källne, Elisabeth

    1998-09-01

    Time-resolved VUV spectroscopy has been used to investigate the effects of impurities in a reversed field pinch operating with a resistive shell. Results of electron temperature, impurity ion densities, particle confinement time and 0741-3335/40/9/004/img1 together with a description of the interpretation and the equipment are presented.

  14. Hexamethylcyclopentadiene: time-resolved photoelectron spectroscopy and ab initio multiple spawning simulations

    DEFF Research Database (Denmark)

    Wolf, T. J. A.; Kuhlman, Thomas Scheby; Schalk, O.

    2014-01-01

    comparing time-resolved photoelectron spectroscopy (TRPES) with ab initio multiple spawning (AIMS) simulations on the MS-MR-CASPT2 level of theory. We disentangle the relationship between two phenomena that dominate the immediate molecular response upon light absorption: a spectrally dependent delay...

  15. Time resolved X-ray absorption spectroscopy in condensed matter: A road map to the future

    Energy Technology Data Exchange (ETDEWEB)

    Dell’Angela, Martina [Elettra-Sincrotrone Trieste S.C.p.A., Trieste (Italy); Parmigiani, Fulvio [Elettra-Sincrotrone Trieste S.C.p.A., Trieste (Italy); Department of Physics, University of Trieste, Trieste (Italy); Institute of Physics II, University of Cologne, Cologne (Germany); Malvestuto, Marco, E-mail: marco.malvestuto@elettra.eu [Elettra-Sincrotrone Trieste S.C.p.A., Trieste (Italy)

    2015-04-15

    Highlights: • We provide perspectives in the field Time resolved XAS in condensed matter. • A look at the new technological innovations that are shaping the field of pulsed X-ray sources are introduced. • New experimental schemes for tr-XAS are illustrated. - Abstract: Nowadays cutting edge femtosecond EUV and soft X-rays radiation sources are the driving force of groundbreaking time resolved X-ray spectroscopies. These new light sources are allowing pioneering experiments in the field of ultrafast phenomena and disclosing new insights about the physics of the out-of-equilibrium matter. Here we report an introductory and concise outlook about some possible perspectives in this field.

  16. Broadband Rotational Spectroscopy

    Science.gov (United States)

    Pate, Brooks

    2014-06-01

    The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De

  17. Time-resolved detection of temperature, concentration, and pressure in a shock tube by intracavity absorption spectroscopy

    Science.gov (United States)

    Fjodorow, Peter; Fikri, Mustapha; Schulz, Christof; Hellmig, Ortwin; Baev, Valery M.

    2016-06-01

    In this paper, we demonstrate the first application of intracavity absorption spectroscopy (ICAS) for monitoring species concentration, total pressure, and temperature in shock-tube experiments. ICAS with a broadband Er3+-doped fiber laser is applied to time-resolved measurements of absorption spectra of shock-heated C2H2. The measurements are performed in a spectral range between 6512 and 6542 cm-1, including many absorption lines of C2H2, with a time resolution of 100 µs and an effective absorption path length of 15 m. Up to 18-times increase of the total pressure and a temperature rise of up to 1200 K have been monitored. Due to the ability of simultaneously recording many absorption lines in a broad spectral range, the presented technique can also be applied to multi-component analysis of transient single-shot processes in reactive gas mixtures in shock tubes, pulse detonation engines, or explosions.

  18. Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes

    Science.gov (United States)

    Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng

    2016-09-01

    Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ˜400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.

  19. Probing interfacial electron dynamics with time-resolved X-ray spectroscopy

    Science.gov (United States)

    Neppl, Stefan

    2015-05-01

    Time-resolved core-level spectroscopy techniques using laser pulses to initiate and short X-ray pulses to probe photo-induced processes have the potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics at complex interfaces. We describe the implementation of femto- and picosecond time-resolved photoelectron spectroscopy at the Linac Coherent Light Source (LCLS) and at the Advanced Light Source (ALS) in order to follow light-driven electron dynamics at dye-semiconductor interfaces on femto- to nanosecond timescales, and from the perspective of individual atomic sites. A distinct transient binding-energy shift of the Ru3d photoemission lines originating from the metal centers of N3 dye-molecules adsorbed on nanoporous ZnO is observed 500 fs after resonant HOMO-LUMO excitation with a visible laser pulse. This dynamical chemical shift is accompanied by a characteristic surface photo-voltage response of the semiconductor substrate. The two phenomena and their correlation will be discussed in the context of electronic bottlenecks for efficient interfacial charge-transfer and possible charge recombination and relaxation pathways leading to the neutralization of the transiently oxidized dye following ultrafast electron injection. First steps towards in operando time-resolved X-ray absorption spectroscopy techniques to monitor interfacial chemical dynamics will be presented.

  20. Photoemission with high-order harmonics: A tool for time-resolved core-level spectroscopy

    DEFF Research Database (Denmark)

    Christensen, Bjarke Holl; Raarup, Merete Krog; Balling, Peter

    2010-01-01

    A setup for femtosecond time-resolved photoelectron spectroscopy of solid surfaces is presented. The photon energies for core-level spectroscopy experiments are created by high-order harmonic generation from infrared 120-femtosecond laser pulses focused in a Ne gas jet. The present experimental...... realization allows the sample, located in an ultrahigh-vacuum chamber, to be illuminated by 106 65-eV photons per laser pulse at a 10 Hz repetition rate. The spectral width of a single harmonic is 0.77 eV (FWHM), and a few harmonics are selected by specially designed Mo/Si multi-layer mirrors. Photoelectrons...

  1. Broadband transmission EPR spectroscopy.

    Directory of Open Access Journals (Sweden)

    Wilfred R Hagen

    Full Text Available EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9-10 GHz range. Most (biomolecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin - nuclear spin interactions and electron spin - electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8-2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

  2. A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics

    Energy Technology Data Exchange (ETDEWEB)

    Boschini, F.; Hedayat, H.; Piovera, C.; Dallera, C. [Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy); Gupta, A. [Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Carpene, E., E-mail: ettore.carpene@polimi.it [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy)

    2015-01-15

    A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO{sub 2} single crystals as a benchmark.

  3. The analysis of time-resolved optical waveguide absorption spectroscopy based on positive matrix factorization.

    Science.gov (United States)

    Liu, Ping; Li, Zhu; Li, Bo; Shi, Guolong; Li, Minqiang; Yu, Daoyang; Liu, Jinhuai

    2013-08-01

    Time-resolved optical waveguide absorption spectroscopy (OWAS) makes use of an evanescent field to detect the polarized absorption spectra of sub-monomolecular adlayers. This technique is suitable for the investigation of kinetics at the solid/liquid interface of dyes, pigments, fluorescent molecules, quantum dots, metallic nanoparticles, and proteins with chromophores. In this work, we demonstrate the application of positive matrix factorization (PMF) to analyze time-resolved OWAS for the first time. Meanwhile, PCA is researched to compare with PMF. The absorption/desorption kinetics of Rhodamine 6G (R6G) onto a hydrophilic glass surface and the dynamic process of Meisenheimer complex between Cysteine and TNT are selected as samples to verify experimental system and analytical methods. The results are shown that time-resolved OWAS can well record the absorption/desorption of R6G onto a hydrophilic glass surface and the dynamic formation process of Meisenheimer complexes. The feature of OWAS extracted by PMF is dynamic and consistent with the results analyzed by the traditional function of time/wavelength-absorbance. Moreover, PMF prevents the negative factors from occurring, avoids contradicting physical reality, and makes factors more easily interpretable. Therefore, we believe that PMF will provide a valuable analysis route to allow processing of increasingly large and complex data sets. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Broadband Transmission EPR Spectroscopy

    Science.gov (United States)

    Hagen, Wilfred R.

    2013-01-01

    EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9–10 GHz range. Most (bio)molecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin – nuclear spin interactions and electron spin – electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8–2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed. PMID:23555819

  5. Ultrafast Time-Resolved Hard X-Ray Emission Spectroscopy on a Tabletop

    Directory of Open Access Journals (Sweden)

    Luis Miaja-Avila

    2016-09-01

    Full Text Available Experimental tools capable of monitoring both atomic and electronic structure on ultrafast (femtosecond to picosecond time scales are needed for investigating photophysical processes fundamental to light harvesting, photocatalysis, energy and data storage, and optical display technologies. Time-resolved hard x-ray (>3  keV spectroscopies have proven valuable for these measurements due to their elemental specificity and sensitivity to geometric and electronic structures. Here, we present the first tabletop apparatus capable of performing time-resolved x-ray emission spectroscopy. The time resolution of the apparatus is better than 6 ps. By combining a compact laser-driven plasma source with a highly efficient array of microcalorimeter x-ray detectors, we are able to observe photoinduced spin changes in an archetypal polypyridyl iron complex [Fe(2,2^{′}-bipyridine_{3}]^{2+} and accurately measure the lifetime of the quintet spin state. Our results demonstrate that ultrafast hard x-ray emission spectroscopy is no longer confined to large facilities and now can be performed in conventional laboratories with 10 times better time resolution than at synchrotrons. Our results are enabled, in part, by a 100- to 1000-fold increase in x-ray collection efficiency compared to current techniques.

  6. Hole emission from Ge/Si quantum dots studied by time-resolved capacitance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kapteyn, C.M.A.; Lion, M.; Heitz, R.; Bimberg, D. [Technische Univ. Berlin (Germany). Inst. fuer Festkoerperphysik; Miesner, C.; Asperger, T.; Brunner, K.; Abstreiter, G. [Technische Univ. Muenchen, Garching (Germany). Walter-Schottky-Inst. fuer Physikalische Grundlagen der Halbleiterelektronik

    2001-03-01

    Emission of holes from self-organized Ge quantum dots (QDs) embedded in Si Schottky diodes is studied by time-resolved capacitance spectroscopy (DLTS). The DLTS signal is rather broad and depends strongly on the filling and detection bias conditions. The observed dependence is interpreted in terms of carrier emission from many-hole states of the QDs. The activation energies obtained from the DLTS measurements are a function of the amount of stored charge and the position of the Fermi level in the QDs. (orig.)

  7. Efficiency estimates and practical aspects of an optical Kerr gate for time-resolved luminescence spectroscopy

    Science.gov (United States)

    Dmitruk, I.; Shynkarenko, Ye; Dmytruk, A.; Aleksiuk, D.; Kadan, V.; Korenyuk, P.; Zubrilin, N.; Blonskiy, I.

    2016-12-01

    We report experience of assembling an optical Kerr gate setup at the Femtosecond Laser Center for collective use at the Institute of Physics of the National Academy of Sciences of Ukraine. This offers an inexpensive solution to the problem of time-resolved luminescence spectroscopy. Practical aspects of its design and alignment are discussed and its main characteristics are evaluated. Theoretical analysis and numerical estimates are performed to evaluate the efficiency and the response time of an optical Kerr gate setup for fluorescence spectroscopy with subpicosecond time resolution. The theoretically calculated efficiency is compared with the experimentally measured one of ~12% for Crown 5 glass and ~2% for fused silica. Other characteristics of the Kerr gate are analyzed and ways to improve them are discussed. A method of compensation for the refractive index dispersion in a Kerr gate medium is suggested. Examples of the application of the optical Kerr gate setup for measurements of the time-resolved luminescence of Astra Phloxine and Coumarin 30 dyes and both linear and nonlinear chirp parameters of a supercontinuum are presented.

  8. Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements.

    Science.gov (United States)

    Votava, Ondrej; Mašát, Milan; Parker, Alexander E; Jain, Chaithania; Fittschen, Christa

    2012-04-01

    We present in this work a new tracking servoloop electronics for continuous wave cavity-ringdown absorption spectroscopy (cw-CRDS) and its application to time resolved cw-CRDS measurements by coupling the system with a pulsed laser photolysis set-up. The tracking unit significantly increases the repetition rate of the CRDS events and thus improves effective time resolution (and/or the signal-to-noise ratio) in kinetics studies with cw-CRDS in given data acquisition time. The tracking servoloop uses novel strategy to track the cavity resonances that result in a fast relocking (few ms) after the loss of tracking due to an external disturbance. The microcontroller based design is highly flexible and thus advanced tracking strategies are easy to implement by the firmware modification without the need to modify the hardware. We believe that the performance of many existing cw-CRDS experiments, not only time-resolved, can be improved with such tracking unit without any additional modification to the experiment. © 2012 American Institute of Physics

  9. Time-resolved emission spectroscopy for the combustion analysis of series production engines

    Science.gov (United States)

    Block, Bernd; Moeser, Petra; Hentschel, Werner

    1997-04-01

    This paper presents a device that detects light emerging from the combustion inside a series production automotive engine. Simultaneous time and wavelength resolution is achieved by this system and it can be applied in a simple manner to either diesel or spark ignition (SI) engines without any geometrical modification or the combustion chamber. An optical probe is inserted into spark plug or glow plug. A fiber is connected to the probe and leads the light to a spectrograph, which provides spectral analysis in the UV and visible wavelength ranges. An intensified streak camera with time resolution in the microsecond range completes the detection unit. This measuring system enables time-resolved emission spectroscopy applied to the light emitted during the combustion in a series production engine. Time-resolved emission spectra are presented from both a diesel and an SI engine. The time behavior of the internal temperature in a diesel engine combustion chamber and its dependence on engine speed and load are measured with this setup using a multiple two-color method. In an SI engine, the time behavior of the emissions of specific molecules or radicals is detected. Thus, differences in the combustion process are demonstrated to be caused by operation with different fuels.

  10. Conventional and Ultrafast Pump-Probe Time-Resolved Raman Spectroscopy of Strongly Correlated Systems

    Science.gov (United States)

    Yang, Jhih-An

    Raman scattering has become an invaluable tool for the study of strongly-correlated systems because it can directly probe phonons, magnetic excitations, and electronic excitations. The extension of Raman scattering to the time domain by using the pump-probe technique allows us to study the femtosecond dynamics under a non-equilibrium condition. Time-resolved Raman scattering thus is able to disentangle different fundamental interactions that are difficult to distinguish in the energy domain by their different temporal evolution. In this thesis we show the development of time-resolved Raman spectroscopy and its applications to investigate non-equilibrium dynamics in novel materials. The first part of this thesis is devoted to using large-shift Raman spectroscopy to study the electronic structure of Sr2IrO4, a spin-orbit-induced Mott insulator. We found two high-energy excitations of the d-shell multiplet at 690 meV and 680 meV with A1g and B1g symmetry respectively. We show that both pseudospin-flip and non-pseudosin-flip dd electronic transitions are Raman active, but only the latter are observed. The second part is devoted to the study of the time dynamics of electron-hole excitations as well as the G-phonon in graphite after an excitation by an intense laser pulse. We found that the increase of the G-phonon population occurs with a delay of ˜65 fs in contradiction with the two-temperature model. This time-delay is also evidenced by the absence of the so-called self-pumping for G phonons. It decreases with increased pump fluence. We show that these observations imply a new relaxation pathway: Instead of hot carriers transferring energy to G-phonons directly, the energy is first transferred to optical phonons near the zone boundary K-points, which then decay into G-phonons via phonon-phonon scattering. In the third part we study magnetic dynamics in insulating YBa2 Cu3O6+x using time-resolved Raman spectroscopy. We observed ultrafast melting of the magnetic order

  11. Optical properties of drying wood studied by time-resolved near-infrared spectroscopy.

    Science.gov (United States)

    Konagaya, Keiji; Inagaki, Tetsuya; Kitamura, Ryunosuke; Tsuchikawa, Satoru

    2016-05-02

    We measured the optical properties of drying wood with the moisture contents ranging from 10% to 200%. By using time-resolved near-infrared spectroscopy, the reduced scattering coefficient μs' and absorption coefficient μa were determined independent of each other, providing information on the chemical and structural changes, respectively, of wood on the nanometer scale. Scattering from dry pores dominated, which allowed us to determine the drying process of large pores during the period of constant drying rate, and the drying process of smaller pores during the period of decreasing drying rate. The surface layer and interior of the wood exhibit different moisture states, which affect the scattering properties of the wood.

  12. Pseudo-bimolecular [2+2] cycloaddition studied by time-resolved photoelectron spectroscopy

    DEFF Research Database (Denmark)

    Brogaard, Rasmus Y; Boguslavskiy, Andrey E; Schalk, Oliver

    2011-01-01

    The first study of pseudo-bimolecular cycloaddition reaction dynamics in the gas phase is presented. We used femtosecond time-resolved photoelectron spectroscopy (TRPES) to study the [2+2] photocycloaddition in the model system pseudo-gem-divinyl[2.2]paracyclophane. From X-ray crystal diffraction...... measurements we found that the ground-state molecule can exist in two conformers; a reactive one in which the vinyl groups are immediately situated for [2+2] cycloaddition and a nonreactive conformer in which they point in opposite directions. From the measured S(1) lifetimes we assigned a clear relation...... between the conformation and the excited-state reactivity; the reactive conformer has a lifetime of 13 ps, populating the ground state through a conical intersection leading to [2+2] cycloaddition, whereas the nonreactive conformer has a lifetime of 400 ps. Ab initio calculations were performed to locate...

  13. Electron Temperature Measurement of Buried Layer Targets Using Time Resolved K-shell Spectroscopy

    Science.gov (United States)

    Marley, Edward; Foord, M. E.; Shepherd, R.; Beiersdorfer, P.; Brown, G.; Chen, H.; Emig, J.; Schneider, M.; Widmann, K.; Scott, H.; London, R.; Martin, M.; Wilson, B.; Iglesias, C.; Mauche, C.; Whitley, H.; Nilsen, J.; Hoarty, D.; James, S.; Brown, C. R. D.; Hill, M.; Allan, P.; Hobbs, L.

    2016-10-01

    Short pulse laser-heated buried layer experiments have been performed with the goal of creating plasmas with mass densities >= 1 g/cm3 and electron temperatures >= 500 eV. The buried layer geometry has the advantage of rapid energy deposition before significant hydrodynamic expansion occurs. For brief periods (< 40 ps) this provides a low gradient, high density platform for studying emission characteristics under extreme plasma conditions. A study of plasma conditions achievable using the Orion laser facility has been performed. Time resolved K-shell spectroscopy was used to determine the temperature evolution of buried layer aluminum foil targets. The measured evolution is compared to a 2-D PIC simulation done using LSP, which shows late time heating from the non-thermal electron population. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. Femtosecond time-resolved impulsive stimulated Raman spectroscopy using sub-7-fs pulses: Apparatus and applications

    Energy Technology Data Exchange (ETDEWEB)

    Kuramochi, Hikaru [Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198 (Japan); Takeuchi, Satoshi; Tahara, Tahei, E-mail: tahei@riken.jp [Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198 (Japan); Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako 351-0198 (Japan)

    2016-04-15

    We describe details of the setup for time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS). In this method, snapshot molecular vibrational spectra of the photoreaction transients are captured via time-domain Raman probing using ultrashort pulses. Our instrument features transform-limited sub-7-fs pulses to impulsively excite and probe coherent nuclear wavepacket motions, allowing us to observe vibrational fingerprints of transient species from the terahertz to 3000-cm{sup −1} region with high sensitivity. Key optical components for the best spectroscopic performance are discussed. The TR-ISRS measurements for the excited states of diphenylacetylene in cyclohexane are demonstrated, highlighting the capability of our setup to track femtosecond dynamics of all the Raman-active fundamental molecular vibrations.

  15. Development of in situ time-resolved Raman spectroscopy facility for dynamic shock loading in materials

    Science.gov (United States)

    Chaurasia, S.; Rastogi, V.; Rao, U.; Sijoy, C. D.; Mishra, V.; Deo, M. N.

    2017-11-01

    The transient state of excitation and relaxation processes in materials under shock compression can be investigated by coupling the laser driven shock facility with Raman spectroscopy. For this purpose, a time resolved Raman spectroscopy setup has been developed to monitor the physical and the chemical changes such as phase transitions, chemical reactions, molecular kinetics etc., under shock compression with nanosecond time resolution. This system consist of mainly three parts, a 2 J/8 ns Nd:YAG laser system used for generation of pump and probe beams, a Raman spectrometer with temporal and spectral resolution of 1.2 ns and 3 cm‑1 respectively and a target holder in confinement geometry assembly. Detailed simulation for the optimization of confinement geometry targets is performed. Time resolved measurement of polytetrafluoroethylene (PTFE) targets at focused laser intensity of 2.2 GW/cm2 has been done. The corresponding pressure in the Aluminum and PTFE are 3.6 and 1.7 GPa respectively. At 1.7 GPa in PTFE, a red shift of 5 cm‑1 is observed for the CF2 twisting mode (291 cm‑1). Shock velocity in PTFE is calculated by measuring rate of change of ratios of the intensity of Raman lines scattered from shocked volume to total volume of sample in the laser focal spot along the laser axis. The calculated shock velocity in PTFE is found to be 1.64 ± 0.16 km/s at shock pressure of 1.7 GPa, for present experimental conditions.

  16. Design and evaluation of a device for fast multispectral time-resolved fluorescence spectroscopy and imaging

    Energy Technology Data Exchange (ETDEWEB)

    Yankelevich, Diego R. [Department of Electrical and Computer Engineering, University of California, 3101 Kemper Hall, Davis, California 95616 (United States); Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616 (United States); Ma, Dinglong; Liu, Jing; Sun, Yang; Sun, Yinghua; Bec, Julien; Marcu, Laura, E-mail: lmarcu@ucdavis.edu [Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616 (United States); Elson, Daniel S. [Hamlyn Centre for Robotic Surgery, Department of Surgery and Cancer, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)

    2014-03-15

    The application of time-resolved fluorescence spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.8–7 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral time-resolved fluorescence

  17. Toward broadband mechanical spectroscopy

    DEFF Research Database (Denmark)

    Hecksher, Tina; Torchinsky, Darius; Klieber, Christoph

    2017-01-01

    Diverse material classes exhibit qualitatively similar behavior when made viscous upon cooling toward the glass transition, suggesting a common theoretical basis. We used seven different measurement methods to determine the mechanical relaxation kinetics of a prototype molecular glass former over...... a temporal range of 13 decades and over a temperature range spanning liquid to glassy states. The data conform to time–temperature superposition for the main (alpha) process and to a scaling relation of schematic mode-coupling theory. The broadband mechanical measurements demonstrated have fundamental...

  18. Studies of Minerals, Organic and Biogenic Materials through Time-Resolved Raman Spectroscopy

    Science.gov (United States)

    Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Nyugen, Trac; Elsayed-Ali, hani

    2009-01-01

    A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized including marble, which contain CaCO3. Analysis of the results reveals the short (approx.10-13 s) lifetime of the Raman process, and shows that Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. Moreover, it was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due the presence of very strong short-lived fluorescence.

  19. Time-Resolved Kinetic Chirped-Pulse Rotational Spectroscopy in a Room-Temperature Flow Reactor.

    Science.gov (United States)

    Zaleski, Daniel P; Harding, Lawrence B; Klippenstein, Stephen J; Ruscic, Branko; Prozument, Kirill

    2017-12-11

    Chirped-pulse Fourier transform millimeter-wave spectroscopy is a potentially powerful tool for studying chemical reaction dynamics and kinetics. Branching ratios of multiple reaction products and intermediates can be measured with unprecedented chemical specificity; molecular isomers, conformers, and vibrational states have distinct rotational spectra. Here we demonstrate chirped-pulse spectroscopy of vinyl cyanide photoproducts in a flow tube reactor at ambient temperature of 295 K and pressures of 1-10 μbar. This in situ and time-resolved experiment illustrates the utility of this novel approach to investigating chemical reaction dynamics and kinetics. Following 193 nm photodissociation of CH2CHCN, we observe rotational relaxation of energized HCN, HNC, and HCCCN photoproducts with 10 μs time resolution and sample the vibrational population distribution of HCCCN. The experimental branching ratio HCN/HCCCN is compared with a model based on RRKM theory using high-level ab initio calculations, which were in turn validated by comparisons to Active Thermochemical Tables enthalpies.

  20. Cyclohexene Photo-oxidation over Vanadia Catalyst Analyzed by Time Resolved ATR-FT-IR Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Frei, Heinz; Mul, Guido; Wasylenko, Walter; Hamdy, M. Sameh; Frei, Heinz

    2008-06-04

    Vanadia was incorporated in the 3-dimensional mesoporous material TUD-1 with a loading of 2percent w/w vanadia. The performance in the selective photo-oxidation of liquid cyclohexene was investigated using ATR-FT-IR spectroscopy. Under continuous illumination at 458 nm a significant amount of product, i.e. cyclohexenone, was identified. This demonstrates for the first time that hydroxylated vanadia centers in mesoporous materials can be activated by visible light to induce oxidation reactions. Using the rapid scan method, a strong perturbation of the vanadyl environment could be observed in the selective oxidation process induced by a 458 nm laser pulse of 480 ms duration. This is proposed to be caused by interaction of the catalytic centre with a cyclohexenyl hydroperoxide intermediate. The restoration of the vanadyl environment could be kinetically correlated to the rate of formation of cyclohexenone, and is explained by molecular rearrangement and dissociation of the peroxide to ketone and water. The ketone diffuses away from the active center and ATR infrared probing zone, resulting in a decreasing ketone signal on the tens of seconds time scale after initiation of the photoreaction. This study demonstrates the high potential of time resolved ATR FT-IR spectroscopy for mechanistic studies of liquid phase reactions by monitoring not only intermediates and products, but by correlating the temporal behavior of these species to molecular changes of the vanadyl catalytic site.

  1. Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics.

    Science.gov (United States)

    Davis, Caitlin M; Reddish, Michael J; Dyer, R Brian

    2017-05-05

    Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of jump induced difference spectrum from 50ns to 0.5ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Prion protein alpha-to-beta transition monitored by time-resolved Fourier transform infrared spectroscopy.

    Science.gov (United States)

    Ollesch, Julian; Künnemann, Eva; Glockshuber, Rudi; Gerwert, Klaus

    2007-10-01

    The conformational change of the recombinant, murine prion protein (PrP) from an alpha-helical to a beta-sheet enriched state was monitored by time-resolved Fourier transform infrared (FT-IR) spectroscopy. The alpha-to-beta transition is induced by reduction of the single disulfide bond in PrP. This transition is believed to generate the scrapie form PrP(Sc), the supposed infectious agent of transmissible spongiform encephalopathies. We followed the kinetics of this conformational change using a novel method for amide I band analysis of the infrared (IR) spectra. The amide I analysis provides the secondary structure. The amide I decomposition was calibrated with the three dimensional structure of cellular PrP solved by nuclear magnetic resonance (NMR). The novel secondary structure analysis provides a root mean squared deviation (RMSD) of only 3% as compared to the NMR structure. Reduction of alpha-helical PrP caused the transient accumulation of a partially unfolded intermediate, followed by formation of a state with higher beta-sheet than alpha-helical structure contents. The novel approach allows us to now determine the secondary structure of the beta-sheet conformation. This was not determined by either NMR or X-ray. The experiments were performed in a double-sealed security cuvette developed for IR analysis of potentially infectious PrP samples outside the biosafety laboratory.

  3. Characterization of powellite-based solid solutions by site-selective time resolved laser fluorescence spectroscopy.

    Science.gov (United States)

    Schmidt, Moritz; Heck, Stephanie; Bosbach, Dirk; Ganschow, Steffen; Walther, Clemens; Stumpf, Thorsten

    2013-06-21

    We present a comprehensive study of the solid solution system Ca2(MoO4)2-NaGd(MoO4)2 on the molecular scale, by means of site-selective time resolved laser fluorescence spectroscopy (TRLFS). Eu(3+) is used as a trace fluorescent probe, homogeneously substituting for Gd(3+) in the solid solution crystal structure. Site-selective TRLFS of a series of polycrystalline samples covering the whole composition range of the solid solution series from 10% substitution of Ca(2+) to the NaGd end-member reveals it to be homogeneous throughout the whole range. The trivalent ions are incorporated into the powellite structure in only one coordination environment, which exhibits a very strong ligand-metal interaction. Polarization-dependent measurements of a single crystal of NaGd(Eu)(MoO4)2 identify the coordination geometry to be of C2v point symmetry. The S4 symmetry of the Ca site within the powellite lattice can be transformed into C2v assuming minor motion in the first coordination sphere.

  4. Time-resolved four-wave-mixing spectroscopy for inner-valence transitions

    CERN Document Server

    Ding, Thomas; Kaldun, Andreas; Blättermann, Alexander; Meyer, Kristina; Stooß, Veit; Rebholz, Marc; Birk, Paul; Hartmann, Maximilian; Brown, Andrew; Van Der Hart, Hugo; Pfeifer, Thomas

    2015-01-01

    Non-collinear four-wave mixing (FWM) techniques at near-infrared (NIR), visible, and ultraviolet frequencies have been widely used to map vibrational and electronic couplings, typically in complex molecules. However, correlations between spatially localized inner-valence transitions among different sites of a molecule in the extreme ultraviolet (XUV) spectral range have not been observed yet. As an experimental step towards this goal we perform time-resolved FWM spectroscopy with femtosecond NIR and attosecond XUV pulses. The first two pulses (XUV-NIR) coincide in time and act as coherent excitation fields, while the third pulse (NIR) acts as a probe. As a first application we show how coupling dynamics between odd- and even-parity inner-valence excited states of neon can be revealed using a two-dimensional spectral representation. Experimentally obtained results are found to be in good agreement with ab initio time-dependent R-matrix calculations providing the full description of multi-electron interactions,...

  5. Characterization of normal breast tissue heterogeneity using time-resolved near-infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, Tomas [Department of Physics, Lund Institute of Technology, Box 118, SE-221 00 Lund (Sweden); Swartling, Johannes [Department of Physics, Lund Institute of Technology, Box 118, SE-221 00 Lund (Sweden); Taroni, Paola [Politecnico di Milano, Piazza Leonardo da Vinci 32, I-210 33 Milan (Italy); Torricelli, Alessandro [Politecnico di Milano, Piazza Leonardo da Vinci 32, I-210 33 Milan (Italy); Lindblom, Pia [Department of Surgery, Lund University Hospital, SE-221 85 Lund (Sweden); Ingvar, Christian [Department of Surgery, Lund University Hospital, SE-221 85 Lund (Sweden); Andersson-Engels, Stefan [Department of Physics, Lund Institute of Technology, Box 118, SE-221 00 Lund (Sweden)

    2005-06-07

    In recent years, extensive efforts have been made in developing near-infrared optical techniques to be used in detection and diagnosis of breast cancer. Variations in optical properties of normal breast tissue set limits to the performance of such techniques and must therefore be thoroughly examined. In this paper, we present intra- and intersubject as well as contralateral variations of optical and physiological properties in breast tissue as measured by using four-wavelength time-resolved spectroscopy (at 660, 786, 916 and 974 nm). In total, 36 volunteers were examined at five regions at each breast. Optical properties (absorption, {mu}{sub a}, and reduced scattering, {mu}'{sub s}) are derived by employing diffusion theory. The use of four wavelengths enables determination of main tissue chromophores (haemoglobin, water and lipids) as well as haemoglobin oxygenation. Variations in all evaluated properties seen over the entire breast are approximately twice those for small-scale heterogeneity (millimetre scale). Intrasubject variations in optical properties are almost in all cases below 20% for {mu}'{sub s}, and 40% for {mu}{sub a}. Overall variations in water, lipid and haemoglobin concentrations are all in the order of 20%. Oxygenation is the least variable of the quantities evaluated, overall intrasubject variations being 6% on average. Extracted physiological properties confirm differences between pre- and post-menopausal breast tissue. Results do not indicate systematic differences between left and right breast000.

  6. Monitoring brain temperature by time-resolved near-infrared spectroscopy: pilot study

    Science.gov (United States)

    Bakhsheshi, Mohammad Fazel; Diop, Mamadou; St. Lawrence, Keith; Lee, Ting-Yim

    2014-05-01

    Mild hypothermia (HT) is an effective neuroprotective strategy for a variety of acute brain injuries. However, the wide clinical adaptation of HT has been hampered by the lack of a reliable noninvasive method for measuring brain temperature, since core measurements have been shown to not always reflect brain temperature. The goal of this work was to develop a noninvasive optical technique for measuring brain temperature that exploits both the temperature dependency of water absorption and the high concentration of water in brain (80%-90%). Specifically, we demonstrate the potential of time-resolved near-infrared spectroscopy (TR-NIRS) to measure temperature in tissue-mimicking phantoms (in vitro) and deep brain tissue (in vivo) during heating and cooling, respectively. For deep brain tissue temperature monitoring, experiments were conducted on newborn piglets wherein hypothermia was induced by gradual whole body cooling. Brain temperature was concomitantly measured by TR-NIRS and a thermocouple probe implanted in the brain. Our proposed TR-NIRS method was able to measure the temperature of tissue-mimicking phantoms and brain tissues with a correlation of 0.82 and 0.66 to temperature measured with a thermometer, respectively. The mean difference between the TR-NIRS and thermometer measurements was 0.15°C±1.1°C for the in vitro experiments and 0.5°C±1.6°C for the in vivo measurements.

  7. Noninvasive evaluation of tissue-engineered cartilage with time-resolved laser-induced fluorescence spectroscopy.

    Science.gov (United States)

    Kutsuna, Toshiharu; Sato, Masato; Ishihara, Miya; Furukawa, Katsuko S; Nagai, Toshihiro; Kikuchi, Makoto; Ushida, Takashi; Mochida, Joji

    2010-06-01

    Regenerative medicine requires noninvasive evaluation. Our objective is to investigate the application of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) using a nano-second-pulsed laser for evaluation of tissue-engineered cartilage (TEC). To prepare scaffold-free TEC, articular chondrocytes from 4-week-old Japanese white rabbits were harvested, and were inoculated at a high density in a mold. Cells were cultured for 5 weeks by rotating culture (RC) or static culture (SC). The RC group and SC group at each week (n = 5), as well as normal articular cartilage and purified collagen type II (as controls), were analyzed by TR-LIFS. The peak wavelength was compared with those of type II collagen immunostaining and type II collagen quantification by enzyme-linked immunosorbent assay and tensile testing. The fluorescence peak wavelength of the TEC analyzed by this method shifted significantly in the RC group at 3 weeks, and in the SC group at 5 weeks (p TEC.

  8. Conductivity of ZnO nanowires, nanoparticles, and thin films using time-resolved terahertz spectroscopy.

    Science.gov (United States)

    Baxter, Jason B; Schmuttenmaer, Charles A

    2006-12-21

    The terahertz absorption coefficient, index of refraction, and conductivity of nanostructured ZnO have been determined using time-resolved terahertz spectroscopy, a noncontact optical probe. ZnO properties were measured directly for thin films and were extracted from measurements of nanowire arrays and mesoporous nanoparticle films by applying Bruggeman effective medium theory to the composite samples. Annealing significantly reduces the intrinsic carrier concentration in the ZnO films and nanowires, which were grown by chemical bath deposition. The complex-valued, frequency-dependent photoconductivities for all morphologies were found to be similar at short pump-probe delay times. Fits using the Drude-Smith model show that films have the highest mobility, followed by nanowires and then nanoparticles, and that annealing the ZnO increases its mobility. Time constants for decay of photoinjected electron density in films are twice as long as those in nanowires and more than 5 times those for nanoparticles due to increased electron interaction with interfaces and grain boundaries in the smaller-grained materials. Implications for electron transport in dye-sensitized solar cells are discussed.

  9. Improved Fast, Deep Record Length, Time-Resolved Visible Spectroscopy of Plasmas Using Fiber Grids

    Science.gov (United States)

    Brockington, S.; Case, A.; Cruz, E.; Williams, A.; Witherspoon, F. D.; Horton, R.; Klauser, R.; Hwang, D.

    2017-10-01

    HyperV Technologies is developing a fiber-coupled, deep record-length, low-light camera head for performing high time resolution spectroscopy on visible emission from plasma events. By coupling the output of a spectrometer to an imaging fiber bundle connected to a bank of amplified silicon photomultipliers, time-resolved spectroscopic imagers of 100 to 1,000 pixels can be constructed. A second generation prototype 32-pixel spectroscopic imager employing this technique was constructed and successfully tested at the University of California at Davis Compact Toroid Injection Experiment (CTIX). Pixel performance of 10 Megaframes/sec with record lengths of up to 256,000 frames ( 25.6 milliseconds) were achieved. Pixel resolution was 12 bits. Pixel pitch can be refined by using grids of 100 μm to 1000 μm diameter fibers. Experimental results will be discussed, along with future plans for this diagnostic. Work supported by USDOE SBIR Grant DE-SC0013801.

  10. Time-resolved X-ray Absorption Spectroscopy for Electron Transport Study in Warm Dense Gold

    Science.gov (United States)

    Lee, Jong-Won; Bae, Leejin; Engelhorn, Kyle; Heimann, Philip; Ping, Yuan; Barbrel, Ben; Fernandez, Amalia; Beckwith, Martha Anne; Cho, Byoung-Ick; GIST Team; IBS Team; LBNL Collaboration; SLAC Collaboration; LLNL Collaboration

    2015-11-01

    The warm dense Matter represents states of which the temperature is comparable to Fermi energy and ions are strongly coupled. One of the experimental techniques to create such state in the laboratory condition is the isochoric heating of thin metal foil with femtosecond laser pulses. This concept largely relies on the ballistic transport of electrons near the Fermi-level, which were mainly studied for the metals in ambient conditions. However, they were barely investigated in warm dense conditions. We present a time-resolved x-ray absorption spectroscopy measured for the Au/Cu dual layered sample. The front Au layer was isochorically heated with a femtosecond laser pulse, and the x-ray absorption changes around L-edge of Cu, which was attached on the backside of Au, was measured with a picosecond resolution. Time delays between the heating of the `front surface' of Au layer and the alternation of x-ray spectrum of Cu attached on the `rear surface' of Au indicate the energetic electron transport mechanism through Au in the warm dense conditions. IBS (IBS-R012-D1) and the NRF (No. 2013R1A1A1007084) of Korea.

  11. Noninvasive detection of concealed explosives: depth profiling through opaque plastics by time-resolved Raman spectroscopy.

    Science.gov (United States)

    Petterson, Ingeborg E Iping; López-López, María; García-Ruiz, Carmen; Gooijer, Cees; Buijs, Joost B; Ariese, Freek

    2011-11-15

    The detection of explosives concealed behind opaque, diffusely scattering materials is a challenge that requires noninvasive analytical techniques for identification without having to manipulate the package. In this context, this study focuses on the application of time-resolved Raman spectroscopy (TRRS) with a picosecond pulsed laser and an intensified charge-coupled device (ICCD) detector for the noninvasive identification of explosive materials through several millimeters of opaque polymers or plastic packaging materials. By means of a short (250 ps) gate which can be delayed several hundred picoseconds after the laser pulse, the ICCD detector allows for the temporal discrimination between photons from the surface of a sample and those from deeper layers. TRRS was applied for the detection of the two main isomers of dinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene as well as for various other components of explosive mixtures, including akardite II, diphenylamine, and ethyl centralite. Spectra were obtained through different diffuse scattering white polymer materials: polytetrafluoroethylene (PTFE), polyoxymethylene (POM), and polyethylene (PE). Common packaging materials of various thicknesses were also selected, including polystyrene (PS) and polyvinyl chloride (PVC). With the demonstration of the ability to detect concealed, explosives-related compounds through an opaque first layer, this study may have important applications in the security and forensic fields.

  12. Transient photoconductivity in InGaN/GaN multiple quantum wells, measured by time-resolved terahertz spectroscopy

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Cooke, David

    2009-01-01

    Terahertz conductivity of InGaN/GaN MQWs was studied by time-resolved terahertz spectroscopy. Restoration of the built-in piezoelectric field leads to a nonexponential carrier density decay. Terahertz conductivity spectrum is described by the Drude-Smith......Terahertz conductivity of InGaN/GaN MQWs was studied by time-resolved terahertz spectroscopy. Restoration of the built-in piezoelectric field leads to a nonexponential carrier density decay. Terahertz conductivity spectrum is described by the Drude-Smith...

  13. Identifying Fossil Biosignatures and Minerals in Mars Analog Materials Using Time-Resolved Raman Spectroscopy

    Science.gov (United States)

    Shkolyar, S.; Farmer, J.; Alerstam, E.; Maruyama, Y.; Blacksberg, J.

    2013-12-01

    Mars sample return has been identified as a top priority in the planetary science decadal survey. A Mars sample selection and caching mission would be the likely first step in this endeavor. Such a mission would aim to select and prioritize for return to Earth aqueously formed geological samples present at a selected site on Mars, based upon their potential for biosignature capture and preservation. If evidence of past life exists and is found, it is likely to come via the identification of fossilized carbonaceous matter of biological origin (kerogen) found in the selected samples analyzed in laboratories after return to Earth. Raman spectroscopy is considered one of the primary techniques for analyzing materials in situ and selecting the most promising samples for Earth return. We have previously performed a pilot study to better understand the complexities of identifying kerogen using Raman spectroscopy. For the study, we examined a variety of Mars analog materials representing a broad range of mineral compositions and kerogen maturities. The study revealed that kerogen identification in many of the most promising lithologies is often impeded by background fluorescence that originates from long (>10 ns to ms) and short (organic matter in the samples. This work explores the potential for time-gated Raman spectroscopy to enable clear kerogen and mineral identifications in such samples. The JPL time-resolved Raman system uses time gating to reduce background fluorescence. It uses a custom-built SPAD (single photon avalanche diode) detector, featuring a 1-ns time-gate, and electronically variable gate delay. Results for a range of fluorescent samples show that the JPL system reduces fluorescence, allowing the identification of both kerogen and mineral components more successfully than with conventional Raman systems. In some of the most challenging samples, the detection of organic matter is hindered by a combination of short lifetime fluorescence and weak Raman

  14. Vibrational cooling dynamics of a [FeFe]-hydrogenase mimic probed by time-resolved infrared spectroscopy.

    Science.gov (United States)

    Caplins, Benjamin W; Lomont, Justin P; Nguyen, Son C; Harris, Charles B

    2014-12-11

    Picosecond time-resolved infrared spectroscopy (TRIR) was performed for the first time on a dithiolate bridged binuclear iron(I) hexacarbonyl complex ([Fe₂(μ-bdt)(CO)₆], bdt = benzene-1,2-dithiolate) which is a structural mimic of the active site of the [FeFe]-hydrogenase enzyme. As these model active sites are increasingly being studied for their potential in photocatalytic systems for hydrogen production, understanding their excited and ground state dynamics is critical. In n-heptane, absorption of 400 nm light causes carbonyl loss with low quantum yield (<10%), while the majority (ca. 90%) of the parent complex is regenerated with biexponential kinetics (τ₁ = 21 ps and τ₂ = 134 ps). In order to understand the mechanism of picosecond bleach recovery, a series of UV-pump TRIR experiments were performed in different solvents. The long time decay (τ₂) of the transient spectra is seen to change substantially as a function of solvent, from 95 ps in THF to 262 ps in CCl₄. Broadband IR-pump TRIR experiments were performed for comparison. The measured vibrational lifetimes (T₁(avg)) of the carbonyl stretches were found to be in excellent correspondence to the observed τ₂ decays in the UV-pump experiments, signifying that vibrationally excited carbonyl stretches are responsible for the observed longtime decays. The fast spectral evolution (τ₁) was determined to be due to vibrational cooling of low frequency modes anharmonically coupled to the carbonyl stretches that were excited after electronic internal conversion. The results show that cooling of both low and high frequency vibrational modes on the electronic ground state give rise to the observed picosecond TRIR transient spectra of this compound, without the need to invoke electronically excited states.

  15. Investigations of suspension stability of iron oxide nanoparticles using time-resolved UV-visible spectroscopy

    Science.gov (United States)

    Vikram, S.; Vasanthakumari, R.; Tsuzuki, Takuya; Rangarajan, Murali

    2016-09-01

    This study examines the suspension stability of iron oxide nanoparticles of different sizes, magnetic susceptibility, and saturation magnetization over long time scales in dilute systems using time-resolved UV-visible spectroscopy. The effects of citric acid as a chelating agent and applied external magnetic field are also studied. UV-visible spectra are obtained at different times for citric-acid-stabilized nanoparticles dispersed in water, and the peak absorbance is tracked with time, in the presence and absence of external magnetic fields. It is seen that the nanoparticles sediment slowly even in the absence of chain formation, with the phenomenon occurring in two-to-three regimes for the systems studied. Sedimentation exhibits either exponential or power-law behavior of maximum absorbance with time. In the dilute dispersions studied, thermal dispersion is about two orders of magnitude stronger than van der Waals interactions, and chain formation is not easy. Yet, it is likely that local anisotropic structures of the nanoparticles form, through which the attractive interactions result in sedimentation. Citric acid gradually stabilizes the aggregating particles; after an initial faster sedimentation, electrostatic repulsion causes the particles to segregate, as observed by a linear increase in the concentration of the nanoparticles at long times. In the presence of magnetic field, stabilization effects are significantly reduced. It is seen that though the attractive force between the nanoparticles and the external field is smaller than Brownian forces, together with van der Waals interactions, these attractive forces likely act as directing agents facilitating sedimentation. This study demonstrates that aggregation-induced sedimentation of magnetic nanoparticles is likely to play a significant role in magnetic drug targeting even when the particles are stabilized with chelating agents.

  16. Investigations of suspension stability of iron oxide nanoparticles using time-resolved UV–visible spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vikram, S.; Vasanthakumari, R. [B. S. Abdur Rahman University, Polymer Nanotechnology Centre (India); Tsuzuki, Takuya [Australian National University, Research School of Engineering, College of Engineering and Computer Science (Australia); Rangarajan, Murali, E-mail: r-murali@cb.amrita.edu [Amrita University, Center of Excellence in Advanced Materials and Green Technologies, Amrita School of Engineering Coimbatore (India)

    2016-09-15

    This study examines the suspension stability of iron oxide nanoparticles of different sizes, magnetic susceptibility, and saturation magnetization over long time scales in dilute systems using time-resolved UV–visible spectroscopy. The effects of citric acid as a chelating agent and applied external magnetic field are also studied. UV–visible spectra are obtained at different times for citric-acid-stabilized nanoparticles dispersed in water, and the peak absorbance is tracked with time, in the presence and absence of external magnetic fields. It is seen that the nanoparticles sediment slowly even in the absence of chain formation, with the phenomenon occurring in two-to-three regimes for the systems studied. Sedimentation exhibits either exponential or power-law behavior of maximum absorbance with time. In the dilute dispersions studied, thermal dispersion is about two orders of magnitude stronger than van der Waals interactions, and chain formation is not easy. Yet, it is likely that local anisotropic structures of the nanoparticles form, through which the attractive interactions result in sedimentation. Citric acid gradually stabilizes the aggregating particles; after an initial faster sedimentation, electrostatic repulsion causes the particles to segregate, as observed by a linear increase in the concentration of the nanoparticles at long times. In the presence of magnetic field, stabilization effects are significantly reduced. It is seen that though the attractive force between the nanoparticles and the external field is smaller than Brownian forces, together with van der Waals interactions, these attractive forces likely act as directing agents facilitating sedimentation. This study demonstrates that aggregation-induced sedimentation of magnetic nanoparticles is likely to play a significant role in magnetic drug targeting even when the particles are stabilized with chelating agents.Graphical abstract.

  17. Time Resolved Spectroscopy of SGR J1550-5418 Bursts Detected with Fermi/Gamma-Ray Burst Monitor

    NARCIS (Netherlands)

    Younes, G.; Kouveliotou, C.; van der Horst, A.J.; Baring, M.G.; Granot, J.; Watts, A.L.; Bhat, P.N.; Collazzi, A.; Gehrels, N.; Gorgone, N.; Göğüş, E.; Gruber, D.; Grunblatt, S.; Huppenkothen, D.; Kaneko, Y.; von Kienlin, A.; van der Klis, M.; Lin, L.; Mcenery, J.; van Putten, T.; Wijers, R.A.M.J.

    2014-01-01

    We report on a time-resolved spectroscopy of the 63 brightest bursts of SGR J1550-5418, detected with the Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms timescales to characterize the spectral evolution of the bursts. Using a

  18. Time-resolved photoluminescence spectroscopy of semiconductors for optical applications beyond the visible spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Chernikov, Alexey A.

    2011-07-01

    The work discussed in this thesis is focused on the experimental studies regarding these three steps: (1) investigation of the fundamental effects, (2) characterization of new material systems, and (3) optimization of the semiconductor devices. In all three cases, the experimental technique of choice is photoluminescence (PL) spectroscopy. The thesis is organized as follows. Chapter 2 gives a summary of the PL properties of semiconductors relevant for this work. The first section deals with the intrinsic processes in an ideal direct band gap material, starting with a brief summary of the theoretical background followed by the overview of a typical PL scenario. In the second part of the chapter, the role of the lattice-vibrations, the internal electric fields as well as the influence of the band-structure and the dielectric environment are discussed. Finally, extrinsic PL properties are presented in the third section, focusing on defects and disorder in real materials. In chapter 3, the experimental realization of the spectroscopic studies is discussed. The time-resolved photoluminescence (TRPL) setup is presented, focusing on the applied excitation source, non-linear frequency mixing, and the operation of the streak camera used for the detection. In addition, linear spectroscopy setup for continous-wave (CW) PL and absorption measurements is illustrated. Chapter 4 aims at the study of the interactions between electrons and lattice-vibrations in semiconductor crystals relevant for the proper description of carrier dynamics as well as the heat-transfer processes. The presented discussion covers the experimental studies of many-body effects in phonon-assisted emission of semiconductors due to the carriercarrier Coulomb-interaction. The corresponding theoretical background is discussed in detail in chapter 2. The investigations are focused on the two main questions regarding electron-hole plasma contributions to the phonon-assisted light-matter interaction as well as

  19. Detection of rhodopsin dimerization in situ by PIE-FCCS, a time-resolved fluorescence spectroscopy.

    Science.gov (United States)

    Smith, Adam W

    2015-01-01

    Rhodopsin self-associates in the plasma membrane. At low concentrations, the interactions are consistent with a monomer-dimer equilibrium (Comar et al., J Am Chem Soc 136(23):8342-8349, 2014). At high concentrations in native tissue, higher-order clusters have been observed (Fotiadis et al., Nature 421:127-128, 2003). The physiological role of rhodopsin dimerization is still being investigated, but it is clear that a quantitative assessment is essential to determining the function of rhodopsin clusters in vision. To quantify rhodopsin interactions, I will outline the theory and methodology of a specialized time-resolved fluorescence spectroscopy for measuring membrane protein-protein interactions called pulsed-interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). The strength of this technique is its ability to quantify rhodopsin interactions in situ (i.e., a live cell plasma membrane). There are two reasons for restricting the scope to live cell membranes. First, the compositional heterogeneity of the plasma membrane creates a complex milieu with thousands of lipid, protein, and carbohydrate species. This makes it difficult to infer quaternary interactions from detergent solubilized samples or construct a model phospholipid bilayer that recapitulates all of the interactions present in native membranes. Second, organizational structure and dynamics is a key feature of the plasma membrane, and fixation techniques like formaldehyde cross-linking and vitrification will modulate the interactions. PIE-FCCS is based on two-color fluorescence imaging with time-correlated single-photon counting (TCSPC) (Becker et al., Rev Sci Instrum 70:1835-1841, 1999). By time-tagging every detected photon, the data can be analyzed as a fluorescence intensity distribution, fluorescence lifetime histogram, or fluorescence (cross-)correlation spectra (FCS/FCCS) (Becker, Advanced time-correlated single-photon counting techniques, Springer, Berlin, 2005). These

  20. Quantifying the cerebral metabolic rate of oxygen by combining diffuse correlation spectroscopy and time-resolved near-infrared spectroscopy.

    Science.gov (United States)

    Verdecchia, Kyle; Diop, Mamadou; Lee, Ting-Yim; St Lawrence, Keith

    2013-02-01

    Preterm infants are highly susceptible to ischemic brain injury; consequently, continuous bedside monitoring to detect ischemia before irreversible damage occurs would improve patient outcome. In addition to monitoring cerebral blood flow (CBF), assessing the cerebral metabolic rate of oxygen (CMRO2) would be beneficial considering that metabolic thresholds can be used to evaluate tissue viability. The purpose of this study was to demonstrate that changes in absolute CMRO2 could be measured by combining diffuse correlation spectroscopy (DCS) with time-resolved near-infrared spectroscopy (TR-NIRS). Absolute CBF was determined using bolus-tracking TR-NIRS to calibrate the DCS measurements. Cerebral venous blood oxygenation (SvO2) was determined by multiwavelength TR-NIRS measurements, the accuracy of which was assessed by directly measuring the oxygenation of sagittal sinus blood. In eight newborn piglets, CMRO2 was manipulated by varying the anesthetics and by injecting sodium cyanide. No significant differences were found between the two sets of SvO2 measurements obtained by TR-NIRS or sagittal sinus blood samples and the corresponding CMRO2 measurements. Bland-Altman analysis showed a mean CMRO2 difference of 0.0268 ± 0.8340 mLO2/100 g/min between the two techniques over a range from 0.3 to 4 mL O2/100 g/min.

  1. Light harvesting, light adaptation and photoprotection in aquatic photosynthesis studies by time-resolved fluorescence spectroscopy

    OpenAIRE

    Chukhutsina, V.

    2015-01-01

    Summary Aquatic photosynthetic organisms unavoidably experience light fluctuations that vary in amplitude, duration and origin, compromising their photosynthetic efficiency. Weather conditions and underwater flow cause continuous changes in irradiance to which the organisms have to adapt. Many light-adaptation strategies of photosynthetic organisms, such as light acclimation, photoprotection and state transitions are still not well understood. In this thesis, time-resolved fluorescence s...

  2. Time-resolved Spectroscopy of a Sheared Flow Stabilized Z-pinch Plasma

    Science.gov (United States)

    Forbes, Eleanor

    2016-10-01

    The ZaP Flow Z-pinch Project investigates the use of sheared-axial flows to stabilize an otherwise unstable plasma configuration. Diagnostics with sub-microsecond resolution are required to obtain accurate time-resolved data since the plasma pulse is approximately 100 μs. Analyzing the Doppler shift of impurity line radiation from the pinch provides a measure of the velocity profile and is a reliable method of determining the plasma sheared flow. The velocity profile is spatially resolved through the use of a 20-chord fiber bundle. The ZaP-HD experiment has used a PI-MAX intensified CCD array to record a single time-resolved spectrum per plasma pulse. Obtaining the evolution of the velocity profile using this method required spectra acquired over hundreds of pulses with identical initial parameters and varying acquisition times. The use of a Kirana 05M ultra-fast framing camera is investigated for recording time-resolved velocity profiles during a single pulse. The Kirana utilizes an ultraviolet intensifier to record 180 frames of UV light at up to 2 million frames per second. An ultraviolet optics system is designed to couple the exit port of an Acton SP-500i spectrometer to the Kirana UV intensifier and focus spectra at the camera detector plane. This work is supported by US DoE FES, NNSA, and ARPA-E ALPHA.

  3. Ultrafast optical responses of {beta}-carotene and lycopene probed by sub-20-fs time-resolved coherent spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, M.; Sugisaki, M. [CREST-JST and Department of Physics, Osaka City University, Osaka 558-8585 (Japan); Gall, A.; Robert, B. [CEA, Institut de Biologie et Technologies de Saclay, and CNRS, Gif-sur-Yvette F-91191 (France); Cogdell, R.J. [IBLS, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom); Hashimoto, H., E-mail: hassy@sci.osaka-cu.ac.j [CREST-JST and Department of Physics, Osaka City University, Osaka 558-8585 (Japan)

    2009-12-15

    We investigate how structural distortions in carotenoid cause decoherences of its high-frequency vibrational modes by applying the sub-20-fs time-resolved transient grating spectroscopy to {beta}-carotene and lycopene. The results indicate that the C=C central stretching mode shows significant loss of coherence under the effects of the steric hindrance between {beta}-ionone ring and polyene backbone, whereas the other high-frequency modes do not show such dependency on the structural distortions.

  4. Quantification of joint inflammation in rheumatoid arthritis by time-resolved diffuse optical spectroscopy and tracer kinetic modeling

    Science.gov (United States)

    Ioussoufovitch, Seva; Morrison, Laura B.; Lee, Ting-Yim; St. Lawrence, Keith; Diop, Mamadou

    2015-03-01

    Rheumatoid arthritis (RA) is characterized by chronic synovial inflammation, which can cause progressive joint damage and disability. Diffuse optical spectroscopy (DOS) and imaging have the potential to become potent monitoring tools for RA. We devised a method that combined time-resolved DOS and tracer kinetics modeling to rapidly and reliably quantify blood flow in the joint. Preliminary results obtained from two animals show that the technique can detect joint inflammation as early as 5 days after onset.

  5. System for time-resolved laser absorption spectroscopy and its application to high-power impulse magnetron sputtering

    Czech Academy of Sciences Publication Activity Database

    Adámek, Petr; Olejníček, Jiří; Hubička, Zdeněk; Čada, Martin; Kment, Štěpán; Kohout, Michal; Do, H.T.

    2017-01-01

    Roč. 88, č. 2 (2017), 1-8, č. článku 023105. ISSN 0034-6748 R&D Projects: GA TA ČR(CZ) TF01000084; GA ČR(CZ) GA15-00863S Institutional support: RVO:68378271 Keywords : plasma diagnostics * HiPIMS * time resolved measurement * laser absorption spectroscopy Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.515, year: 2016

  6. Broadband time-resolved diffuse optical spectrometer for clinical diagnostics: characterization and in-vivo measurements in the 600-1350 nm spectral range

    Science.gov (United States)

    Konugolu Venkata Sekar, Sanathana; Farina, Andrea; Martinenghi, Edoardo; Dalla Mora, Alberto; Taroni, Paola; Pifferi, Antonio; Durduran, Turgut; Pagliazzi, Marco; Lindner, Claus; Farzam, Parisa; Mora, Mireia; Squarcia, Mattia; Urbano-Ispizua, A.

    2015-07-01

    We report on the design, performance assessment, and first in vivo measurement of a Time-Resolved Diffuse Optical system for broadband (600-1350 nm) nm measurement of absorption and scattering spectra of biological tissues for non-invasive clinical diagnostics. Two strategies to reduce drift and enhance responsivity are adopted. The system was enrolled in a first in vivo test phase on healthy volunteers, carrying out non-invasive, in vivo quantification of key tissue constituents (oxy- and deoxy-hemoglobin, water, lipids, collagen) and tissue micro-structure (scatterer size and density).

  7. Use of time-resolved spectroscopy as a method to monitor carotenoids present in tomato extract obtained using ultrasound treatment.

    Science.gov (United States)

    Bot, Francesca; Anese, Monica; Lemos, M Adília; Hungerford, Graham

    2016-01-01

    Compounds exhibiting antioxidant activity have received much interest in the food industry because of their potential health benefits. Carotenoids such as lycopene, which in the human diet mainly derives from tomatoes (Solanum lycopersicum), have attracted much attention in this aspect and the study of their extraction, processing and storage procedures is of importance. Optical techniques potentially offer advantageous non-invasive and specific methods to monitor them. To obtain both fluorescence and Raman information to ascertain if ultrasound assisted extraction from tomato pulp has a detrimental effect on lycopene. Use of time-resolved fluorescence spectroscopy to monitor carotenoids in a hexane extract obtained from tomato pulp with application of ultrasound treatment (583 kHz). The resultant spectra were a combination of scattering and fluorescence. Because of their different timescales, decay associated spectra could be used to separate fluorescence and Raman information. This simultaneous acquisition of two complementary techniques was coupled with a very high time-resolution fluorescence lifetime measurement of the lycopene. Spectroscopic data showed the presence of phytofluene and chlorophyll in addition to lycopene in the tomato extract. The time-resolved spectral measurement containing both fluorescence and Raman data, coupled with high resolution time-resolved measurements, where a lifetime of ~5 ps was attributed to lycopene, indicated lycopene appeared unaltered by ultrasound treatment. Detrimental changes were, however, observed in both chlorophyll and phytofluene contributions. Extracted lycopene appeared unaffected by ultrasound treatment, while other constituents (chlorophyll and phytofluene) were degraded. Copyright © 2015 John Wiley & Sons, Ltd.

  8. Time-resolved photoelectron spectroscopy of polyatomic molecules using 42-nm vacuum ultraviolet laser based on high harmonics generation

    Science.gov (United States)

    Nishitani, Junichi; West, Christopher W.; Higashimura, Chika; Suzuki, Toshinori

    2017-09-01

    Time-resolved photoelectron spectroscopy (TRPES) of gaseous polyatomic molecules using 266-nm (4.7 eV) pump and 42-nm (29.5 eV) probe pulses is presented. A 1-kHz Ti:sapphire laser with a 35 fs pulse duration is employed to generate high harmonics in Kr gas, and the 19th harmonic (42-nm) was selected using two SiC/Mg mirrors. Clear observation of the ultrafast electronic dephasing in pyrazine and photoisomerization of 1,3-cyclohexadiene demonstrates the feasibility of TRPES with the UV pump and VUV probe pulses under weak excitation conditions in the perturbation regime.

  9. Time resolved and label free monitoring of extracellular metabolites by surface enhanced Raman spectroscopy.

    Directory of Open Access Journals (Sweden)

    Victoria Shalabaeva

    Full Text Available Metabolomics is an emerging field of cell biology that aims at the comprehensive identification of metabolite levels in biological fluids or cells in a specific functional state. Currently, the major tools for determining metabolite concentrations are mass spectrometry coupled with chromatographic techniques and nuclear magnetic resonance, which are expensive, time consuming and destructive for the samples. Here, we report a time resolved approach to monitor metabolite dynamics in cell cultures, based on Surface Enhanced Raman Scattering (SERS. This method is label-free, easy to use and provides the opportunity to simultaneously study a broad range of molecules, without the need to process the biological samples. As proof of concept, NIH/3T3 cells were cultured in vitro, and the extracellular medium was collected at different time points to be analyzed with our engineered SERS substrates. By identifying individual peaks of the Raman spectra, we showed the simultaneous detection of several components of the conditioned medium, such as L-tyrosine, L-tryptophan, glycine, L-phenylalanine, L-histidine and fetal bovine serum proteins, as well as their intensity changes during time. Furthermore, analyzing the whole Raman data set with the Principal Component Analysis (PCA, we demonstrated that the Raman spectra collected at different days of culture and clustered by similarity, described a well-defined trajectory in the principal component plot. This approach was then utilized to determine indirectly the functional state of the macrophage cell line Raw 264.7, stimulated with the lipopolysaccharide (LPS for 24 hours. The collected spectra at different time points, clustered by the PCA analysis, followed a well-defined trajectory, corresponding to the functional change of cells toward the activated pro-inflammatory state induced by the LPS. This study suggests that our engineered SERS surfaces can be used as a versatile tool both for the characterization

  10. Cyclohexene photo-oxidation over vanadia catalyst analyzed by time resolvedATR-FT-IT spectroscopy

    NARCIS (Netherlands)

    Mul, Guido; Wasylenko, W.; Sameh Hamdy, M.; Frei, H.

    2008-01-01

    Vanadia was incorporated in the 3-D mesoporous material TUD-1 with a loading of 2% w/w vanadia. The performance in the selective photo-oxidation of liquid cyclohexene was investigated using ATR-FT-IR spectroscopy. Under continuous illumination at 458 nm a significant amount of product,

  11. Ultrabroadband time-resolved THz spectroscopy of polymer-based solar cells

    DEFF Research Database (Denmark)

    Cooke, David G.; Krebs, Frederik C; Jepsen, Peter Uhd

    2011-01-01

    We have developed ultrabroadband THz spectroscopy in reflection mode for characterization of conductivity dynamics in conductive polymer samples used in organic solar cells. The spectrometer is designed to have a time resolution limited only by the duration of the optical pump pulse, thus enabling...... the investigation of charge generation processes on the sub-100-fs time scale....

  12. Temperature Measurements in Reacting Flows Using Time-Resolved Femtosecond Coherent Anti-Stokes Raman Scattering (fs-CARS) Spectroscopy (Postprint)

    National Research Council Canada - National Science Library

    Roy, Sukesh; Kinnius, Paul J; Lucht, Robert P; Gord, James R

    2007-01-01

    Time-resolved femtosecond coherent anti-Stokes Raman scattering (fs-CARS) spectroscopy of the nitrogen molecule is used for the measurement of temperature in atmospheric-pressure, near-adiabatic, hydrogen-air diffusion flames...

  13. Time-resolved and steady-state fluorescence spectroscopy for the assessment of skin photoaging process

    Science.gov (United States)

    D´Almeida, Camila de Paula; Campos, Carolina; Saito Nogueira, Marcelo; Pratavieira, Sebastião.; Kurachi, Cristina

    2015-06-01

    pathology. The optical properties of these intrinsic fluorophores respond to the microenvironment and the metabolic status, thus making fluorescence spectroscopy a valuable tool to study the conditions of biological tissues. The purpose of this study is to investigate the hairless mice skin metabolic changes during the photoaging process through lifetime and fluorescence measurements targeting NADH and FAD. Two lasers centered at 378 nm and 445 nm, respectively, perform excitation of NADH and FAD. The fluorescence acquisition is carried out at mice dorsal and ventral regions throughout the photoaging protocol and aging process. Differences in fluorescence and lifetime data between young and photoaged mice measurements were observed. The endogenous fluorescence spectrum of photoaged dorsal skin showed an increase compared to young and aged skin. Lifetime of bound NADH and free FAD presented an increase in the first week that continued until the end of the protocol. Aging process is being investigated to complement the information obtained from fluorescence data and lifetime of photoaging process.

  14. Time-resolved ultrafast spectroscopy of wide-gap II-VI semiconductor quantum wells

    CERN Document Server

    Brown, G

    2001-01-01

    proposal is supported through the development of a phenomenological model describing the dynamic evolution of exciton spin populations. The inclusion of higher order Coulomb interaction terms within current many-body theory is limited by the analytical complexity This work provides valuable experimental observations, which invite further theoretical endeavour within this field. Ultrafast spectroscopic techniques have been used out to investigate both coherent and incoherent exciton dynamics within zinc selenide-based multiple quantum wells. Time-integrated four-wave-mixing experiments were carried out to investigate exciton dephasing due to exciton-phonon scattering. In particular experiments on multiple quantum well structures with a range of well widths demonstrated that exciton-acoustic phonon scattering was found to reach a maximum when the quantum confinement within the well was also maximised. The technique of pump-continuum probe spectroscopy has been enhanced giving improved resolution of absorption d...

  15. The study of polyplex formation and stability by time-resolved fluorescence spectroscopy of SYBR Green I-stained DNA.

    Science.gov (United States)

    D'Andrea, Cosimo; Pezzoli, Daniele; Malloggi, Chiara; Candeo, Alessia; Capelli, Giulio; Bassi, Andrea; Volonterio, Alessandro; Taroni, Paola; Candiani, Gabriele

    2014-12-01

    Polyplexes are nanoparticles formed by the self-assembly of DNA/RNA and cationic polymers specifically designed to deliver exogenous genetic material to cells by a process called transfection. There is a general consensus that a subtle balance between sufficient extracellular protection and intracellular release of nucleic acids is a key factor for successful gene delivery. Therefore, there is a strong need to develop suitable tools and techniques for enabling the monitoring of the stability of polyplexes in the biological environment they face during transfection. In this work we propose time-resolved fluorescence spectroscopy in combination with SYBR Green I-DNA dye as a reliable tool for the in-depth characterization of the DNA/vector complexation state. As a proof of concept, we provide essential information on the assembly and disassembly of complexes formed between DNA and each of three cationic polymers, namely a novel promising chitosan-graft-branched polyethylenimine copolymer (Chi-g-bPEI), one of its building block 2 kDa bPEI and the gold standard transfectant 25 kDa bPEI. Our results highlight the higher information content provided by the time-resolved studies of SYBR Green I/DNA, as compared to conventional steady state measurements of ethidium bromide/DNA that enabled us to draw relationships among fluorescence lifetime, polyplex structural changes and transfection efficiency.

  16. Variation in LOV Photoreceptor Activation Dynamics Probed by Time Resolved Infrared Spectroscopy

    KAUST Repository

    Iuliano, James N.

    2017-12-14

    The light, oxygen, voltage (LOV) domain proteins are blue light photoreceptors that utilize a non-covalently bound flavin mononucleotide (FMN) cofactor as the chromophore. The modular nature of these proteins has led to their wide adoption in the emerging fields of optogenetics and optobiology, where the LOV domain has been fused to a variety of output domains leading to novel light-controlled applications. In the present work, we extend our studies of the sub-picosecond to several hundred microsecond transient infrared spectroscopy of the isolated LOV domain AsLOV2 to three full-length photoreceptors in which the LOV domain is fused to an output domain: the LOV-STAS protein, YtvA, the LOV-HTH transcription factor, EL222, and the LOV-histidine kinase, LovK. Despite differences in tertiary structure, the overall pathway leading to cysteine adduct formation from the FMN triplet state is highly conserved, although there are slight variations in rate. However significant differences are observed in the vibrational spectra and kinetics after adduct formation, which are directly linked to the specific output function of the LOV domain. While the rate of adduct formation varies by only 3.6-fold amongst the proteins, the subsequent large-scale structural changes in the full-length LOV photoreceptors occur over the micro- to sub-millisecond timescales and vary by orders of magnitude depending on the different output function of each LOV domain.

  17. Time-Resolved Spectroscopy Diagnostic of Laser-Induced Optical Breakdown

    Directory of Open Access Journals (Sweden)

    Christian G. Parigger

    2010-01-01

    Full Text Available Transient laser plasma is generated in laser-induced optical breakdown (LIOB. Here we report experiments conducted with 10.6-micron CO2 laser radiation, and with 1.064-micron fundamental, 0.532-micron frequency-doubled, 0.355-micron frequency-tripled Nd:YAG laser radiation. Characterization of laser induced plasma utilizes laser-induced breakdown spectroscopy (LIBS techniques. Atomic hydrogen Balmer series emissions show electron number density of 1017 cm−3 measured approximately 10 μs and 1 μs after optical breakdown for CO2 and Nd:YAG laser radiation, respectively. Recorded molecular recombination emission spectra of CN and C2 Swan bands indicate an equilibrium temperature in excess of 7000 Kelvin, inferred for these diatomic molecules. Reported are also graphite ablation experiments where we use unfocused laser radiation that is favorable for observation of neutral C3 emission due to reduced C3 cation formation. Our analysis is based on computation of diatomic molecular spectra that includes accurate determination of rotational line strengths, or Hönl-London factors.

  18. Time-resolved x-ray absorption spectroscopy: Watching atoms dance

    Energy Technology Data Exchange (ETDEWEB)

    Milne, Chris J; Pham, Van-Thai; Veen, Renske M van der; El Nahhas, Amal; Lima, Frederico; Vithanage, Dimali A; Chergui, Majed [Laboratoire de Spectroscopie Ultrarapide, Ecole Polytechnique Federale de Lausanne (Switzerland); Gawelda, Wojciech [Laser Processing Group, Instituto de Optica, CSIC (Spain); Johnson, Steven L; Beaud, Paul; Ingold, Gerhard; Grolimund, Daniel; Borca, Camelia; Kaiser, Maik; Abela, Rafael [Swiss Light Source, Paul Scherrer Institut (Switzerland); Benfatto, Maurizio [Laboratori Nazionali di Frascati, INFN (Italy); Hauser, Andreas [Departement de Chimie Physique, Universite de Geneve (Switzerland); Bressler, Christian, E-mail: majed.chergui@epfl.c, E-mail: chris.milne@psi.c [European XFEL Project Team, Deutsches Elektronen Synchrotron (Germany)

    2009-11-15

    The introduction of pump-probe techniques to the field of x-ray absorption spectroscopy (XAS) has allowed the monitoring of both structural and electronic dynamics of disordered systems in the condensed phase with unprecedented accuracy, both in time and in space. We present results on the electronically excited high-spin state structure of an Fe(II) molecular species, [Fe{sup II}(bpy){sub 3}]{sup 2+}, in aqueous solution, resolving the Fe-N bond distance elongation as 0.2 A. In addition an analysis technique using the reduced {chi}{sup 2} goodness of fit between FEFF EXAFS simulations and the experimental transient absorption signal in energy space has been successfully tested as a function of excited state population and chemical shift, demonstrating its applicability in situations where the fractional excited state population cannot be determined through other measurements. Finally by using a novel ultrafast hard x-ray 'slicing' source the question of how the molecule relaxes after optical excitation has been successfully resolved using femtosecond XANES.

  19. Characterization of human immunodeficiency virus-1 (HIV-1) rev by (time-resolved) fluorescence spectroscopy.

    Science.gov (United States)

    Kungl, A J; Seidel, C; Schilk, A; Daly, T J; Kauffmann, H F; Auer, M

    1994-12-01

    Fluorescence spectroscopy has been applied to the single tryptophan-containing regulatory protein Rev of human immunodeficiency virus (HIV-1). The fluorescence emission was found to have a maximum at 336 nm which refers to a surrounding of the chromophore of intermediate polarity. Fluorescence transients recorded at the maximum of fluorescence were found to decay nonexponentially. A bimodal lifetime distribution is obtained from exponential series analysis (ESM) with centers at 1.7 and 4.5 ns. Two microenvironments for tryptophan are suggested to be responsible for the two lifetime distributions. No innerfilter effect occurred in a Rev solution up to a concentration of 40 μM. A data quality study of ESM analysis as function of collected counts in the peak channel maximum (CIM) showed that, for reliable reconvolution, at least 15,000 CIM are necessary. The widths of the two distributions are shown to be temperature dependent. The broadening of the lifetime distributions when the temperature is raised to 50°C is interpreted as extension of the number of conformational substates which do not interconvert on the fluorescence time scale. The thermal deactivation (temperature quenching) is reflected in a constant decrease in the center of the short-lived lifetime distribution.

  20. Structural dynamics of membrane proteins - time-resolved and surface-enhanced IR spectroscopy

    Science.gov (United States)

    Heberle, Joachim

    2013-03-01

    Membrane proteins are the target of more than 50% of all drugs and are encoded by about 30% of the human genome. Electrophysiological techniques, like patch-clamp, unravelled many functional aspects of membrane proteins but suffer from structural sensitivity. We have developed Surface Enhanced Infrared Difference Absorption Spectroscopy (SEIDAS) to probe potential-induced structural changes of a protein on the level of a monolayer. A novel concept is introduced to incorporate membrane proteins into solid supported lipid bilayers in an orientated manner via the affinity of the His-tag to the Ni-NTA terminated gold surface. General applicability of the methodological approach is shown by tethering photosystem II to the gold surface. In conjunction with hydrogenase, the basis is set towards a biomimetic system for hydrogen production. Recently, we succeeded to record IR difference spectra of a monolayer of sensory rhodopsin II under voltage-clamp conditions. This approach opens an avenue towards mechanistic studies of voltage-gated ion channels with unprecedented structural and temporal sensitivity. Initial vibrational studies on the novel light-gated channelrhodopsin-2 (ChR2) will be presented. ChR2 represents a versatile tool in the new field of optogenetics where physiological reactions are controlled by light.

  1. TIME-RESOLVED ULTRAVIOLET SPECTROSCOPY OF THE M-DWARF GJ 876 EXOPLANETARY SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    France, Kevin; Froning, Cynthia S. [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Linsky, Jeffrey L. [JILA, University of Colorado and NIST, 440 UCB, Boulder, CO 80309 (United States); Tian, Feng [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309 (United States); Roberge, Aki, E-mail: kevin.france@colorado.edu [Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2012-05-10

    Extrasolar planets orbiting M-stars may represent our best chance to discover habitable worlds in the coming decade. The ultraviolet spectrum incident upon both Earth-like and Jovian planets is critically important for proper modeling of their atmospheric heating and chemistry. In order to provide more realistic inputs for atmospheric models of planets orbiting low-mass stars, we present new near- and far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet host GJ 876 (M4V). Using the COS and STIS spectrographs on board the Hubble Space Telescope, we have measured the 1150-3140 A spectrum of GJ 876. We have reconstructed the stellar H I Ly{alpha} emission line profile, and find that the integrated Ly{alpha} flux is roughly equal to the rest of the integrated flux (1150-1210 A + 1220-3140 A) in the entire ultraviolet bandpass (F(Ly{alpha})/F(FUV+NUV) Almost-Equal-To 0.7). This ratio is {approx}2500 Multiplication-Sign greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H{sub 2} (T(H{sub 2}) > 2000 K). We show the light curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/quiescent flux ratios {>=}10. The strong FUV radiation field of an M-star (and specifically Ly{alpha}) is important for determining the abundance of O{sub 2}-and the formation of biomarkers-in the lower atmospheres of Earth-like planets in the habitable zones of low-mass stars.

  2. Time-Resolved Ultraviolet Spectroscopy of The M-Dwarf GJ 876 Exoplanetary System

    Science.gov (United States)

    France, Kevin; Linsky, Jeffrey L.; Tian, Feng; Froning, Cynthia S.; Roberge, Aki

    2012-01-01

    Extrasolar planets orbiting M-stars may represent our best chance to discover habitable worlds in the coming decade. The ultraviolet spectrum incident upon both Earth-like and Jovian planets is critically important for proper modeling of their atmospheric heating and chemistry. In order to provide more realistic inputs for atmospheric models of planets orbiting low-mass stars, we present new near- and far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet host GJ 876 (M4V). Using the COS and STIS spectrographs on board the Hubble Space Telescope, we have measured the 1150-3140 A spectrum of GJ 876. We have reconstructed the stellar H1 Ly alpha emission line profile, and find that the integrated Ly alpha flux is roughly equal to the rest of the integrated flux (1150-1210 A + 1220-3140 A) in the entire ultraviolet bandpass (F(Ly alpha)/F(FUV+NUV) equals approximately 0.7). This ratio is approximately 2500x greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H2 (T(H2) greater than 2000 K). We show the light curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/quiescent flux ratios greater than or equal to 10. The strong FUV radiation field of an M-star (and specifically Ly alpha) is important for determining the abundance of O2--and the formation of biomarkers-in the lower atmospheres of Earth-like planets in the habitable zones of low-mass stars.

  3. Time-resolved photoluminescence spectroscopy and imaging: new approaches to the analysis of cultural heritage and its degradation.

    Science.gov (United States)

    Nevin, Austin; Cesaratto, Anna; Bellei, Sara; D'Andrea, Cosimo; Toniolo, Lucia; Valentini, Gianluca; Comelli, Daniela

    2014-04-02

    Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested.

  4. On the intrinsic photophysics of indigo: a time-resolved photoelectron spectroscopy study of the indigo carmine dianion.

    Science.gov (United States)

    Chatterley, Adam S; Horke, Daniel A; Verlet, Jan R R

    2012-12-14

    The intrinsic photophysics of indigo has been studied using gas-phase time-resolved photoelectron imaging of the indigo carmine dianion (InC(2-)). The action spectrum reveals that the gas-phase absorption spectrum arising from the S(1) indigo. Femtosecond spectroscopy shows that the S(1) state decays on a 1.4 ps timescale. Through isotopic substitution, the primary mechanism on the S(1) excited state can be assigned to an intra-molecular proton transfer, which is the same as that which has been observed in solution. However, the excited state lifetime is significantly shorter in vacuum. These similarities and differences are discussed in terms of recent theoretical investigations of the S(1) excited state of indigo.

  5. In situ characterization of ZnTe epilayer irradiation via time-resolved and power-density-dependent Raman spectroscopy

    Science.gov (United States)

    Wiedemeier, V.; Berth, G.; Zrenner, A.; Larramendi, E. M.; Woggon, U.; Lischka, K.; Schikora, D.

    2011-10-01

    Laser irradiation damage in ZnTe epilayers was analyzed in situ by power-density-dependent and time-resolved micro-Raman spectroscopy. Damage by ablation or compound decomposition on the sample surface was revealed by the decrease of the ZnTe-nLO mode intensity with the increase of laser power density. The appearance of the peaks associated with the stronger crystalline-tellurium modes, tellurium aggregates and second-order Raman scattering at room temperature μ-Raman spectra was observed for higher power densities than 4.4 × 105 W cm-2. The Raman signal time transients of ZnTe-nLO and crystalline-tellurium modes reveal an exponential evolution of the laser irradiation damage and a fast formation of crystalline tellurium aggregates on the layer surface.

  6. Time-Resolved Fluorescence Spectroscopy and Fluorescence Lifetime Imaging Microscopy for Characterization of Dendritic Polymer Nanoparticles and Applications in Nanomedicine.

    Science.gov (United States)

    Boreham, Alexander; Brodwolf, Robert; Walker, Karolina; Haag, Rainer; Alexiev, Ulrike

    2016-12-24

    The emerging field of nanomedicine provides new approaches for the diagnosis and treatment of diseases, for symptom relief and for monitoring of disease progression. One route of realizing this approach is through carefully constructed nanoparticles. Due to the small size inherent to the nanoparticles a proper characterization is not trivial. This review highlights the application of time-resolved fluorescence spectroscopy and fluorescence lifetime imaging microscopy (FLIM) for the analysis of nanoparticles, covering aspects ranging from molecular properties to particle detection in tissue samples. The latter technique is particularly important as FLIM allows for distinguishing of target molecules from the autofluorescent background and, due to the environmental sensitivity of the fluorescence lifetime, also offers insights into the local environment of the nanoparticle or its interactions with other biomolecules. Thus, these techniques offer highly suitable tools in the fields of particle development, such as organic chemistry, and in the fields of particle application, such as in experimental dermatology or pharmaceutical research.

  7. Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

    Energy Technology Data Exchange (ETDEWEB)

    Radu, L. [Department of Molecular Genetics and Radiobiology, Babes National Institute, Bucharest (Romania)], E-mail: lilianajradu@yahoo.fr; Mihailescu, I. [Department of Lasers, Laser, Plasma and Radiation Physics Institute, Bucharest (Romania); Radu, S. [Department of Computer Science, Polytechnics University, Bucharest (Romania); Gazdaru, D. [Department of Biophysics, Bucharest University (Romania)

    2007-09-21

    The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m{sup 2} was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy.

  8. Time-Resolved Photoluminescence Spectroscopy and Imaging: New Approaches to the Analysis of Cultural Heritage and Its Degradation

    Directory of Open Access Journals (Sweden)

    Austin Nevin

    2014-04-01

    Full Text Available Applications of time-resolved photoluminescence spectroscopy (TRPL and fluorescence lifetime imaging (FLIM to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested.

  9. Time-Resolved Fluorescence Spectroscopy and Fluorescence Lifetime Imaging Microscopy for Characterization of Dendritic Polymer Nanoparticles and Applications in Nanomedicine

    Directory of Open Access Journals (Sweden)

    Alexander Boreham

    2016-12-01

    Full Text Available The emerging field of nanomedicine provides new approaches for the diagnosis and treatment of diseases, for symptom relief and for monitoring of disease progression. One route of realizing this approach is through carefully constructed nanoparticles. Due to the small size inherent to the nanoparticles a proper characterization is not trivial. This review highlights the application of time-resolved fluorescence spectroscopy and fluorescence lifetime imaging microscopy (FLIM for the analysis of nanoparticles, covering aspects ranging from molecular properties to particle detection in tissue samples. The latter technique is particularly important as FLIM allows for distinguishing of target molecules from the autofluorescent background and, due to the environmental sensitivity of the fluorescence lifetime, also offers insights into the local environment of the nanoparticle or its interactions with other biomolecules. Thus, these techniques offer highly suitable tools in the fields of particle development, such as organic chemistry, and in the fields of particle application, such as in experimental dermatology or pharmaceutical research.

  10. Modified diglycol-amides for actinide separation: solvent extraction and time-resolved laser fluorescence spectroscopy complexation studies

    Energy Technology Data Exchange (ETDEWEB)

    Wilden, A.; Modolo, G.; Lange, S.; Sadowski, F.; Bosbach, D. [Foschungszentrum Juelich GmbH, IEK-6, Juelich (Germany); Beele, B.B.; Panak, P.J. [Ruprecht-Karls-Universitaet Heidelberg, Physikalisch Chemisces Institut - PCI, Heidelberg (Germany); Karlsruher Institut fuer Technologie - INE, Karlsruhe (Germany); Skerencak-Frech, A.; Geist, A. [Karlsruher Institut fuer Technologie - INE, Karlsruhe (Germany); Iqbal, M. [University of Twente, Laboratory of Molecular Nanofabrication, Enschede (Netherlands); Department of Chemistry, University of Sargodha, Sargodha 40100 (Pakistan); Verboom, W. [University of Twente, Laboratory of Molecular Nanofabrication, Enschede (Netherlands)

    2013-07-01

    In this work, the back-bone of the diglycolamide-structure of the TODGA extractant was modified by adding one or two methyl groups to the central methylene carbon-atoms. The influence of these structural modifications on the extraction behavior of trivalent actinides and lanthanides and other fission products was studied in solvent extraction experiments. The addition of methyl groups to the central methylene carbon atoms leads to reduced distribution ratios, also for Sr(II). This reduced extraction efficiency for Sr(II) is beneficial for process applications, as the co-extraction of Sr(II) can be avoided, resulting in an easier process design. The use of these modified diglycol-amides in solvent extraction processes is discussed. Furthermore, the complexation of Cm(III) and Eu(III) to the ligands was studied using Time-Resolved-Laser-Fluorescence-Spectroscopy (TRLFS). The complexes were characterized by slope analysis and conditional stability constants were determined.

  11. Effects of Cosmetic Therapy on Cognitive Function in Elderly Women Evaluated by Time-Resolved Spectroscopy Study.

    Science.gov (United States)

    Machida, A; Shirato, M; Tanida, M; Kanemaru, C; Nagai, S; Sakatani, K

    2016-01-01

    With the rapid increase in dementia in developed countries, it is important to establish methods for maintaining or improving cognitive function in elderly people. To resolve such problems, we have been developing a cosmetic therapy (CT) program for elderly women. However, the mechanism and limitations of CT are not yet clear. In order to clarify these issues, we employed time-resolved spectroscopy (TRS) to evaluate the effect of CT on prefrontal cortex (PFC) activity in elderly females with various levels of cognitive impairment. Based on the Mini-Mental State Examination (MMSE) score, the subjects were classified into mild (mean MMSE score: 24.1±3.8) and moderate (mean MMSE score: 10.3±5.8) cognitive impairment (CI) groups (p0.05). These results suggest that CT affects cognitive function by altering PFC activity in elderly women with mild CI, but not moderate CI.

  12. Wide-field time-resolved luminescence imaging and spectroscopy to decipher obliterated documents in forensic science

    Science.gov (United States)

    Suzuki, Mototsugu; Akiba, Norimitsu; Kurosawa, Kenji; Kuroki, Kenro; Akao, Yoshinori; Higashikawa, Yoshiyasu

    2016-01-01

    We applied a wide-field time-resolved luminescence (TRL) method with a pulsed laser and a gated intensified charge coupled device (ICCD) for deciphering obliterated documents for use in forensic science. The TRL method can nondestructively measure the dynamics of luminescence, including fluorescence and phosphorescence lifetimes, which prove to be useful parameters for image detection. First, we measured the TRL spectra of four brands of black porous-tip pen inks on paper to estimate their luminescence lifetimes. Next, we acquired the TRL images of 12 obliterated documents at various delay times and gate times of the ICCD. The obliterated contents were revealed in the TRL images because of the difference in the luminescence lifetimes of the inks. This method requires no pretreatment, is nondestructive, and has the advantage of wide-field imaging, which makes it is easy to control the gate timing. This demonstration proves that TRL imaging and spectroscopy are powerful tools for forensic document examination.

  13. Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Guorong [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Neville, Simon P.; Worth, Graham A., E-mail: g.a.worth@bham.ac.uk [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Schalk, Oliver [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 109 61 Stockholm (Sweden); Sekikawa, Taro [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Ashfold, Michael N. R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Stolow, Albert, E-mail: astolow@uottawa.ca [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Departments of Chemistry and Physics, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada)

    2015-02-21

    The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole’s electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A{sub 2}(πσ{sup ∗}) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A{sub 1}(ππ{sup ∗}) and B{sub 2}(ππ{sup ∗}) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole’s electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B{sub 1}(πσ{sup ∗}) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B{sub 1}(πσ{sup ∗}) state is found to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A{sub 2}(πσ{sup ∗}) state.

  14. Dynamic Time-Resolved Chirped-Pulse Rotational Spectroscopy of Vinyl Cyanide Photoproducts in a Room Temperature Flow Reactor

    Science.gov (United States)

    Zaleski, Daniel P.; Prozument, Kirill

    2017-06-01

    Chirped-pulsed (CP) Fourier transform rotational spectroscopy invented by Brooks Pate and coworkers a decade ago is an attractive tool for gas phase chemical dynamics and kinetics studies. A good reactor for such a purpose would have well-defined (and variable) temperature and pressure conditions to be amenable to accurate kinetic modeling. Furthermore, in low pressure samples with large enough number of molecular emitters, reaction dynamics can be observable directly, rather than mediated by supersonic expansion. In the present work, we are evaluating feasibility of in situ time-resolved CP spectroscopy in a room temperature flow tube reactor. Vinyl cyanide (CH_2CHCN), neat or mixed with inert gasses, flows through the reactor at pressures 1-50 μbar (0.76-38 mTorr) where it is photodissociated by a 193 nm laser. Millimeter-wave beam of the CP spectrometer co-propagates with the laser beam along the reactor tube and interacts with nascent photoproducts. Rotational transitions of HCN, HNC, and HCCCN are detected, with ≥10 μs time-steps for 500 ms following photolysis of CH_2CHCN. The post-photolysis evolution of the photoproducts' rotational line intensities is investigated for the effects of rotational and vibrational thermalization of energized photoproducts. Possible contributions from bimolecular and wall-mediated chemistry are evaluated as well.

  15. Probing the hydrogen-bond network of water via time-resolved soft x-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huse, Nils; Wen, Haidan; Nordlund, Dennis; Szilagyi, Erzsi; Daranciang, Dan; Miller, Timothy A.; Nilsson, Anders; Schoenlein, Robert W.; Lindenberg, Aaron M.

    2009-04-24

    We report time-resolved studies of hydrogen bonding in liquid H2O, in response to direct excitation of the O-H stretch mode at 3 mu m, probed via soft x-ray absorption spectroscopy at the oxygen K-edge. This approach employs a newly developed nanofluidic cell for transient soft x-ray spectroscopy in liquid phase. Distinct changes in the near-edge spectral region (XANES) are observed, and are indicative of a transient temperature rise of 10K following transient laser excitation and rapid thermalization of vibrational energy. The rapid heating occurs at constant volume and the associated increase in internal pressure, estimated to be 8MPa, is manifest by distinct spectral changes that differ from those induced by temperature alone. We conclude that the near-edge spectral shape of the oxygen K-edge is a sensitive probe of internal pressure, opening new possibilities for testing the validity of water models and providing new insight into the nature of hydrogen bonding in water.

  16. Photophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fission

    KAUST Repository

    Dean, Jacob C.

    2017-08-18

    Quantitative singlet fission has been observed for a variety of acene derivatives such as tetracene and pentacene, and efforts to extend the library of singlet fission compounds is of current interest. Preliminary calculations suggest anthradithiophenes exhibit significant exothermicity between the first optically-allowed singlet state, S1, and 2 × T1 with an energy difference of >5000 cm−1. Given the fulfillment of this ingredient for singlet fission, here we investigate the singlet fission capability of a difluorinated anthradithiophene dimer (2ADT) covalently linked by a (dimethylsilyl)ethane bridge and derivatized by triisobutylsilylethynyl (TIBS) groups. Photophysical characterization of 2ADT and the single functionalized ADT monomer were carried out in toluene and acetone solution via absorption and fluorescence spectroscopy, and their photo-initiated dynamics were investigated with time-resolved fluorescence (TRF) and transient absorption (TA) spectroscopy. In accordance with computational predictions, two conformers of 2ADT were observed via fluorescence spectroscopy and were assigned to structures with the ADT cores trans or cis to one another about the covalent bridge. The two conformers exhibited markedly different excited state deactivation mechanisms, with the minor trans population being representative of the ADT monomer showing primarily radiative decay, while the dominant cis population underwent relaxation into an excimer geometry before internally converting to the ground state. The excimer formation kinetics were found to be solvent dependent, yielding time constants of ∼1.75 ns in toluene, and ∼600 ps in acetone. While the difference in rates elicits a role for the solvent in stabilizing the excimer structure, the rate is still decidedly long compared to most singlet fission rates of analogous dimers, suggesting that the excimer is neither a kinetic nor a thermodynamic trap, yet singlet fission was still not observed. The result

  17. Sol-to-Gel Transition in Fast Evaporating Systems Observed by in Situ Time-Resolved Infrared Spectroscopy.

    Science.gov (United States)

    Innocenzi, Plinio; Malfatti, Luca; Carboni, Davide; Takahashi, Masahide

    2015-06-22

    The in situ observation of a sol-to-gel transition in fast evaporating systems is a challenging task and the lack of a suitable experimental design, which includes the chemistry and the analytical method, has limited the observations. We synthesise an acidic sol, employing only tetraethylorthosilicate, SiCl4 as catalyst and deuterated water; the absence of water added to the sol allows us to follow the absorption from the external environment and the evaporation of deuterated water. The time-resolved data, obtained by attenuated total reflection infrared spectroscopy on an evaporating droplet, enables us to identify four different stages during evaporation. They are linked to specific hydrolysis and condensation rates that affect the uptake of water from external environment. The second stage is characterized by a decrease in hydroxyl content, a fast rise of condensation rate and an almost stationary absorption of water. This stage has been associated with the sol-to-gel transition. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. The primary photophysics of the Avena sativa phototropin 1 LOV2 domain observed with time-resolved emission spectroscopy.

    Science.gov (United States)

    van Stokkum, Ivo H M; Gauden, Magdalena; Crosson, Sean; van Grondelle, Rienk; Moffat, Keith; Kennis, John T M

    2011-01-01

    The phototropins are blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine in light, oxygen or voltage (LOV) domains. The primary reactions of the Avena sativa phototropin 1 LOV2 domain were investigated by means of time-resolved and low-temperature fluorescence spectroscopy. Synchroscan streak camera experiments revealed a fluorescence lifetime of 2.2 ns in LOV2. A weak long-lived component with emission intensity from 600 to 650 nm was assigned to phosphorescence from the reactive FMN triplet state. This observation allowed determination of the LOV2 triplet state energy level at physiological temperature at 16600 cm(-1). FMN dissolved in aqueous solution showed pH-dependent fluorescence lifetimes of 2.7 ns at pH 2 and 3.9-4.1 ns at pH 3-8. Here, too, a weak phosphorescence band was observed. The fluorescence quantum yield of LOV2 increased from 0.13 to 0.41 upon cooling the sample from 293 to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K in the steady-state emission. © 2011 The Authors. Photochemistry and Photobiology © 2011 The American Society of Photobiology.

  19. Excited state non-adiabatic dynamics of N-methylpyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Guorong [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Neville, Simon P. [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Schalk, Oliver [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 106 91 Stockholm (Sweden); Sekikawa, Taro [Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Ashfold, Michael N. R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Worth, Graham A. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Stolow, Albert, E-mail: astolow@uottawa.ca [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)

    2016-01-07

    The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A{sub 2}(πσ{sup ∗}) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B{sub 1}(π3p{sub y}) Rydberg state, followed by prompt internal conversion to the A{sub 2}(πσ{sup ∗}) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A{sub 2}(πσ{sup ∗}) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A{sub 2}(πσ{sup ∗}) state, facilitating wavepacket motion around the potential barrier in the N–CH{sub 3} dissociation coordinate.

  20. Single-shot Raman spectroscopy and time-resolved reflectivity of a shocked TATB-based explosive

    Science.gov (United States)

    Hebert, Philippe; Saint-Amans, Charles; Doucet, Michel; de Resseguier, Thibaut

    2015-06-01

    Single-shot Raman spectroscopy experiments under shockwave loading were performed in order to get information on the initiation mechanisms that can lead to sustained detonation of a TATB-based explosive. Shocks up to 30 GPa were generated using a two-stage laser-driven flyer plate generator. The samples were confined by an optical window and shock pressure was maintained for at least 30 ns. Photon Doppler Velocimetry measurements were performed at the explosive/window interface to determine the shock pressure profile. Raman spectra were recorded as a function of shock pressure and the shifts of the principal modes were compared to static high-pressure measurements performed in a diamond anvil cell. Our shock data indicate the role of temperature effects on the H-bonding network present in TATB. Our Raman spectra also show a progressive extinction of the signal which disappears around 9 GPa. High-speed photography images reveal a simultaneous progressive darkening of the sample surface up to total opacity at 9 GPa. Time-resolved reflectivity measurements under shock compression seem to indicate that this opacity is due to a broadening of the absorption spectrum over the entire visible region.

  1. Communication: Ultrafast time-resolved ion photofragmentation spectroscopy of photoionization-induced proton transfer in phenol-ammonia complex

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Ching-Chi; Tsai, Tsung-Ting; Ho, Jr-Wei; Chen, Yi-Wei; Cheng, Po-Yuan, E-mail: pycheng@mx.nthu.edu.tw [Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan (China)

    2014-11-07

    Photoionization-induced proton transfer (PT) in phenol-ammonia (PhOH-NH{sub 3}) complex has been studied using ultrafast time-resolved ion photofragmentation spectroscopy. Neutral PhOH-NH{sub 3} complexes prepared in a free jet are photoionized by femtosecond [1+1] resonance-enhanced multiphoton ionization via the S{sub 1} state, and the subsequent dynamics occurring in the cations is probed by delayed pulses that result in ion fragmentation. The observed temporal evolutions of the photofragmentation spectra are consistent with an intracomplex PT reaction. The experiments revealed that PT in [PhOH-NH{sub 3}]{sup +} cation proceeds in two distinct steps: an initial impulsive wave-packet motion in ∼70 fs followed by a slower relaxation of about 1 ps that stabilizes the system into the final PT configuration. These results indicate that for a barrierless PT system, even though the initial PT motions are impulsive and ultrafast, the reaction may take a much longer time scale to complete.

  2. Interaction of europium and nickel with calcite studied by Rutherford Backscattering Spectrometry and Time-Resolved Laser Fluorescence Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sabau, A. [Agence Nationale pour la gestion des Déchets RAdioactifs, 1-7 rue J. Monnet, Parc de la Croix Blanche, 92298 Châtenay-Malabry Cedex (France); Université de Nice Sophia Antipolis, Ecosystèmes Côtiers Marins et Réponses aux Stress (ECOMERS), 28 avenue Valrose, 06108 Nice Cedex 2 (France); Pipon, Y., E-mail: pipon@ipnl.in2p3.fr [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); Institut Universitaire de Technologie (IUT) Lyon-1, Université Claude Bernard Lyon 1, 69 622 Villeurbanne Cedex (France); Toulhoat, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); CEA/DEN, Saclay, 91191 Gif sur Yvette (France); Lomenech, C. [Université de Nice Sophia Antipolis, Ecosystèmes Côtiers Marins et Réponses aux Stress (ECOMERS), 28 avenue Valrose, 06108 Nice Cedex 2 (France); Jordan, N. [Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology (IRE) (Germany); Moncoffre, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); Barkleit, A. [Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology (IRE) (Germany); and others

    2014-08-01

    This study aims at elucidating the mechanisms regulating the interaction of Eu and Ni with calcite (CaCO{sub 3}). Calcite powders or single crystals (some mm sized) were put into contact with Eu or Ni solutions at concentrations ranging from 10{sup −3} to 10{sup −5} mol L{sup −1} for Eu and 10{sup −3} mol L{sup −1} for Ni. The sorption durations ranged from 1 week to 1 month. Rutherford Backscattering Spectrometry (RBS) well adapted to discriminate incorporation processes such as: (i) adsorption or co precipitation at the mineral surfaces or, (ii) incorporation into the mineral structure (through diffusion for instance), has been carried out. Moreover, using the fluorescence properties of europium, the results have been compared to those obtained by Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) on calcite powders. For the single crystals, complementary SEM observations of the mineral surfaces at low voltage were also performed. Results showed that Ni accumulates at the calcite surface whereas Eu is also incorporated at a greater depth. Eu seems therefore to be incorporated into two different states in calcite: (i) heterogeneous surface accumulation and (ii) incorporation at depth greater than 160 nm after 1 month of sorption. Ni was found to accumulate at the surface of calcite without incorporation.

  3. Time-resolved spectroscopy of excitons and carriers in GaN and InGaN

    CERN Document Server

    Kyhm, K

    2001-01-01

    delocalised electron-hole pairs from the lowest confined level are responsible for the gain in our sample. The polarization dependence of biexcitonic signals and quantum beats between A-excitons (X sub A) and A-biexcitons (X sub A X sub A) in a high-quality GaN epilayer are measured by spectrally-resolved and time-integrated four-wave mixing measurements. We also measured the polarization dependent B-biexciton (X sub B X sub B) signal. The emission mechanisms in GaN and ln sub x Ga sub 1 sub - sub x N is systematically studied to investigate carrier and exciton dynamics. Reflectance, time-integrated luminescence, and time-resolved reflectance spectroscopy are used to study exciton transitions in GaN, and the saturation of the exciton resonances with increasing carrier density has been measured in the case of resonant and non-resonant excitations. The coincidence between the density for the onset of the stimulated emission and the Mott density leads us to the conclusion that the stimulated emission mechanism i...

  4. Time-resolved X-Ray Absorption Spectroscopy of a Cobalt-Based Hydrogen Evolution System for Artificial Photosynthesis

    Science.gov (United States)

    Moonshiram, Dooshaye; Gimbert, Carolina; Lehmann, Carl; Southworth, Stephen; Llobet, Antoni; Argonne National Laboratory Team; Institut Català d'Investigació Química Collaboration

    2015-03-01

    Production of cost-effective hydrogen gas through solar power is an important challenge of the Department of Energy among other global industry initiatives. In natural photosynthesis, the oxygen evolving complex(OEC) can carry out four-electron water splitting to hydrogen with an efficiency of around 60%. Although, much progress has been carried out in determining mechanistic pathways of the OEC, biomimetic approaches have not duplicated Nature's efficiency in function. Over the past years, we have witnessed progress in developments of light harvesting modules, so called chromophore/catalytic assemblies. In spite of reportedly high catalytic activity of these systems, quantum yields of hydrogen production are below 40 % when using monochromatic light. Proper understanding of kinetics and bond making/breaking steps has to be achieved to improve efficiency of hydrogen evolution systems. This project shows the timing implementation of ultrafast X-ray absorption spectroscopy to visualize in ``real time'' the photo-induced kinetics accompanying a sequence of redox reactions in a cobalt-based molecular photocatalytic system. Formation of a Co(I) species followed by a Co(III) hydride species all the way towards hydrogen evolution is shown through time-resolved XANES.

  5. Quinones in the A1 binding site in photosystem I studied using time-resolved FTIR difference spectroscopy.

    Science.gov (United States)

    Makita, Hiroki; Rohani, Leyla; Zhao, Nan; Hastings, Gary

    2017-09-01

    Time-resolved step-scan FTIR difference spectroscopy at low temperature (77 K) has been used to study photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthaquinone) and menadione (2-methyl-1,4-naphthaquinone) incorporated into the A1 binding site. By subtracting spectra for PSI with phylloquinone incorporated from spectra for PSI with menadione incorporated a (menadione - phylloquinone) double difference spectrum was constructed. In the double difference spectrum bands associated with protein vibrational modes effectively cancel, and the bands in the spectrum are primarily associated with the neutral and reduced states of the two quinones in the A1 binding site. To aid in the assignment of bands in the experimental double difference spectrum, a double difference spectrum was calculated using three-layer ONIOM methods. The calculated and experimental spectra agree well, allowing unambiguous band assignments to be made. The ONIOM calculations show that both quinones in the A1 binding site are similarly oriented, with only a single hydrogen bond between the C4=O quinone carbonyl group and the backbone NH group of a leucine residue. For the semi-quinone species, but not for the neutral species, this hydrogen bond appears to be very strong. Finally, we have for the first time been able to unmask and identify infrared difference bands associated with neutral naphthoquinone species occupying the A1 binding site in PSI. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Femtosecond time-resolved X-ray absorption spectroscopy of anatase TiO2 nanoparticles using XFEL

    Directory of Open Access Journals (Sweden)

    Yuki Obara

    2017-07-01

    Full Text Available The charge-carrier dynamics of anatase TiO2 nanoparticles in an aqueous solution were studied by femtosecond time-resolved X-ray absorption spectroscopy using an X-ray free electron laser in combination with a synchronized ultraviolet femtosecond laser (268 nm. Using an arrival time monitor for the X-ray pulses, we obtained a temporal resolution of 170 fs. The transient X-ray absorption spectra revealed an ultrafast Ti K-edge shift and a subsequent growth of a pre-edge structure. The edge shift occurred in ca. 100 fs and is ascribed to reduction of Ti by localization of generated conduction band electrons into shallow traps of self-trapped polarons or deep traps at penta-coordinate Ti sites. Growth of the pre-edge feature and reduction of the above-edge peak intensity occur with similar time constants of 300–400 fs, which we assign to the structural distortion dynamics near the surface.

  7. Time-resolved terahertz spectroscopy of electrically conductive metal-organic frameworks doped with redox active species

    Science.gov (United States)

    Alberding, Brian G.; Heilweil, Edwin J.

    2015-09-01

    Metal-Organic Frameworks (MOFs) are three-dimensional coordination polymers that are well known for large pore surface area and their ability to adsorb molecules from both the gaseous and solution phases. In general, MOFs are electrically insulating, but promising opportunities for tuning the electronic structure exist because MOFs possess synthetic versatility; the metal and organic ligand subunits can be exchanged or dopant molecules can be introduced into the pore space. Two such MOFs with demonstrated electrical conductivity are Cu3(1,3,5-benzenetricarboxylate)2, a.k.a HKUST-1, and Cu[Ni(pyrazine-2,3-dithiolate)2]. Herein, these two MOFs have been infiltrated with the redox active species 7,7,8,8-tetracyanoquinodimethane (TCNQ) and iodine under solution phase conditions and shown to produce redox products within the MOF pore space. Vibrational bands assignable to TCNQ anion and triiodide anion have been observed in the Mid-IR and Terahertz ranges using FTIR Spectroscopy. The MOF samples have been further investigated by Time-Resolved Terehertz Spectroscopy (TRTS). Using this technique, the charge mobility, separation, and recombination dynamics have been followed on the picosecond time scale following photoexcitation with visible radiation. The preliminary results show that the MOF samples have small inherent photoconductivity with charge separation lifetimes on the order of a few picoseconds. In the case of HKUST-1, the MOF can also be supported by a TiO2 film and initial results show that charge injection into the TiO2 layer occurs with a comparable efficiency to the dye sensitizer N3, [cis-Bis(isothiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylato ruthenium(II)], and therefore this MOF has potential as a new light absorbing and charge conducting material in photovoltaic devices.

  8. Time-resolved and steady-state studies of biologically and chemically relevant systems using laser, absorption, and fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Charles Ashley [Iowa State Univ., Ames, IA (United States)

    2014-12-20

    In Chapter 2 several experimental and data analysis methods used in this thesis are described. In Chapter 3 steady-state fluorescence spectroscopy was used to determine the concentration of the efflux pump inhibitors (EPIs), pheophorbide a and pyropheophorbide a, in the feces of animals and it was found that their levels far exceed those reported to be inhibitory to efflux pumps. In Chapter 4 the solvation dynamics of 6-Propionyl-2-(N,Ndimethyl) aminonaphthalene (PRODAN) was studied in reverse micelles. The two fluorescent states of PRODAN solvate on different time scales and as such care must be exercised in solvation dynamic studies involving it and its analogs. In Chapter 5 we studied the experimental and theoretical solvation dynamics of coumarin 153 (C153) in wild-type (WT) and modified myoglobins. Based on the nuclear magnetic resonance (NMR) spectroscopy and time-resolved fluorescence studies, we have concluded that it is important to thoroughly characterize the structure of a protein and probe system before comparing the theoretical and experimental results. In Chapter 6 the photophysical and spectral properties of a derivative of the medically relevant compound curcumin called cyclocurcumin was studied. Based on NMR, fluorescence, and absorption studies, the ground- and excited-states of cyclocurcumin are complicated by the existence of multiple structural isomers. In Chapter 7 the hydrolysis of cellulose by a pure form of cellulase in an ionic liquid, HEMA, and its aqueous mixtures at various temperatures were studied with the goal of increasing the cellulose to glucose conversion for biofuel production. It was found that HEMA imparts an additional stability to cellulase and can allow for faster conversion of cellulose to glucose using a pre-treatment step in comparison to only buffer.

  9. Site-selective time resolved laser fluorescence spectroscopy of Eu and Cm doped LaPO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Holliday, K.S.; Walther, C. [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Nukleare Entsorgung; Babelot, C.; Neumeier, S.; Bosbach, D. [Forschungszentrum Juelich GmbH (DE). Inst. fuer Energie und Klimaforschung (IEK), Nukleare Entsorgung und Reaktorsicherheit (IEK-6); Stumpf, T. [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Nukleare Entsorgung; Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Anorganische Chemie

    2012-07-01

    Samples of LaPO{sub 4} doped with Eu{sup 3+} or Cm{sup 3+} were synthesized by a hydrothermal process which resulted in a solid solution at temperatures less than conventional processing. Time resolved laser fluorescence spectroscopy was used to probe the incorporated Eu{sup 3+} or Cm{sup 3+} in order to gain structural information on its local environment. This revealed that Eu{sup 3+} and Cm{sup 3+} incorporate on the La site as expected. The emission spectrum of Eu{sup 3+} resolves the fully degenerate 5-fold splitting of the peaks in the F{sub 2} transition due to the low symmetry of the site, confirming previous calculations. A minor site in the Eu{sup 3+} doped sample is identified as coordinated with hydroxide contamination. Direct excitation of Cm{sup 3+} doped samples show the presence of 'satellite' species. Although these spectral features have been observed in Cm{sup 3+} doped LuPO{sub 4} and YPO{sub 4}, this is the first time that these satellites are resolved into their individual species. These are hypothesized to be due to a disturbance in the ideal structure which creates a break in the equivalence of the four lanthanum sites within a unit cell. The 4-fold ground state splitting of all species is identical, although slightly shifted, indicating similar environments. The fluorescence lifetimes were long (1.2 ms for Cm and 3.6 ms for Eu) indicating an absence of water in the immediate coordination sphere due to the incorporation of the doping ion. (orig.)

  10. Nondestructive assessment of fruit biological age in Brazilian mangoes by time-resolved reflectance spectroscopy in the 540-900 nm spectral range

    NARCIS (Netherlands)

    Spinelli, L.; Rizzolo, A.; Vanoli, M.; Grassi, M.; Eccher Zerbini, P.C.; Meirelles de Azevedo Pementel, A.; Torricelli, A.

    2013-01-01

    Time-resolved Reflectance Spectroscopy (TRS) in the 540–900 nm spectral range has been tested in order to assess nondestructively the biological age of Brazilian mangoes. To this purpose a TRS set-up has been used to measure absorption and scattering coefficients of 60 intact mango fruits (cultivar

  11. Time-resolved FTIR spectroscopy for monitoring protein dynamics exemplified by functional studies of Ras protein bound to a lipid bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Koetting, Carsten, E-mail: carsten.koetting@rub.de [Lehrstuhl fuer Biophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Gueldenhaupt, Joern [Lehrstuhl fuer Biophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Gerwert, Klaus, E-mail: gerwert@bph.rub.de [Lehrstuhl fuer Biophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

    2012-03-02

    Graphical abstract: The first time resolved FTIR investigation of a GTPase reaction of a protein anchored at a single lipid bilayer. Display Omitted Highlights: Black-Right-Pointing-Pointer FTIR difference spectroscopy monitors protein dynamics with atomic detail. Black-Right-Pointing-Pointer ATR-FTIR allows the measurement of a monolayer sample. Black-Right-Pointing-Pointer Membrane proteins can be investigated near physiological conditions. Black-Right-Pointing-Pointer The hydrolysis reaction of Ras was investigated in this condition for the first time. - Abstract: Time-resolved Fourier transform infrared (FTIR) difference spectroscopy is a valuable tool for monitoring the dynamics of protein reactions and interactions. Absorbance changes can be monitored with time resolutions down to nanoseconds and followed for time periods that range over nine orders of magnitude. Membrane proteins bound to solid supported lipid bilayers can be investigated in near physiological conditions with the attenuated total reflection (ATR) technique. Here, we review the basics of time-resolved FTIR with a focus on Ras, a GTPase that is mutated in 25% of human tumors. We show the first time-resolved measurements of membrane anchored Ras and observed the switching between its activated and its inactivated state. We compared those measurements with measurements of the truncated Ras in solution. We found that both the kinetics and the functional groups involved were very similar. This suggested that the membrane did not have a major influence on the hydrolysis reaction.

  12. Non-invasive measurement of blood glucose level by time-resolved transmission spectroscopy: A feasibility study

    Science.gov (United States)

    Sun, Meixiu; Chen, Nanguang

    2012-03-01

    An optical spectroscopic method is investigated theoretically for in vivo measurement of blood glucose concentration. This method is based on dynamic dual wavelength (610 nm and 810 nm) time-resolved measurements under a condition of artificial blood flow kinetics in a human finger. The influence of glucose concentration on absorption and reduced scattering coefficients of the whole blood is simulated using the T-matrix method. The scattering centers, RBC aggregation, under the artificial — kinetics condition are modeled as spheroid. The modified parametric slopes were derived from the Laplace transformed data of the time-resolved transmittance. The results show that an appropriate selection of the Laplace parameter can lead to enhanced sensitivity for glucose measurement.

  13. Determination of blood oxygenation in the brain by time-resolved reflectance spectroscopy: influence of the skin, skull, and meninges

    Science.gov (United States)

    Hielscher, Andreas H.; Liu, Hanli; Wang, Lihong; Tittel, Frank K.; Chance, Britton; Jacques, Steven L.

    1994-07-01

    Near infrared light has been used for the determination of blood oxygenation in the brain but little attention has been paid to the fact that the states of blood oxygenation in arteries, veins, and capillaries differ substantially. In this study, Monte Carlo simulations for a heterogeneous system were conducted, and near infrared time-resolved reflectance measurements were performed on a heterogeneous tissue phantom model. The model was made of a solid polyester resin, which simulates the tissue background. A network of tubes was distributed uniformly through the resin to simulate the blood vessels. The time-resolved reflectance spectra were taken with different absorbing solutions filled in the network. Based on the simulation and experimental results, we investigated the dependence of the absorption coefficient obtained from the heterogeneous system on the absorption of the actual absorbing solution filled in the tubes. We show that light absorption by the brain should result from the combination of blood and blood-free tissue background.

  14. Guest–Host Interactions Investigated by Time-Resolved X-ray Spectroscopies and Scattering at MHz Rates

    DEFF Research Database (Denmark)

    Haldrup, Martin Kristoffer; Vanko, G.; Gawelda, W.

    2012-01-01

    We have studied the photoinduced low spin (LS) to high spin (HS) conversion of [Fe(bipy)3]2+ in aqueous solution. In a laser pump/X-ray probe synchrotron setup permitting simultaneous, time-resolved X-ray diffuse scattering (XDS) and X-ray spectroscopic measurements at a 3.26 MHz repetition rate,...... of the caging solvent, in particular, a decrease in the number of water molecules in the first solvation shell is inferred, as predicted by recent theoretical work....

  15. Probing organometallic reactions by time-resolved infrared spectroscopy in solution and in the solid state using quantum cascade lasers.

    Science.gov (United States)

    Calladine, James A; Horvath, Raphael; Davies, Andrew J; Wriglesworth, Alisdair; Sun, Xue-Zhong; George, Michael W

    2015-05-01

    The photochemistry and photophysics of metal carbonyl compounds (W(CO)6, Cp*Rh(CO)2 (Cp* = η(5)-C5Me5), and fac-[Re(CO)3(4,4'-bpy)2Br] [bpy = bipyridine]) have been examined on the nanosecond timescale using a time-resolved infrared spectrometer with an external cavity quantum cascade laser (QCL) as the infrared source. We show the photochemistry of W(CO)6 in alkane solution is easily monitored, and very sensitive measurements are possible with this approach, meaning it can monitor small transients with absorbance changes less than 10(-6) ΔOD. The C-H activation of Cp*Rh(CO)(C6H12) to form Cp*Rh(CO)(C6H11)H occurs within the first few tens of nanoseconds following photolysis, and we demonstrate that kinetics obtained following deconvolution are in excellent agreement with those measured using an ultrafast laser-based spectrometer. We also show that the high flux and tunability of QCLs makes them suited for solid-state and time-resolved measurements.

  16. Mapping of calf muscle oxygenation and haemoglobin content during dynamic plantar flexion exercise by multi-channel time-resolved near-infrared spectroscopy.

    Science.gov (United States)

    Torricelli, Alessandro; Quaresima, Valentina; Pifferi, Antonio; Biscotti, Giovanni; Spinelli, Lorenzo; Taroni, Paola; Ferrari, Marco; Cubeddu, Rinaldo

    2004-03-07

    A compact and fast multi-channel time-resolved near-infrared spectroscopy system for tissue oximetry was developed. It employs semiconductor laser and fibre optics for delivery of optical signals. Photons are collected by eight 1 mm fibres and detected by a multianode photomultiplier. A time-correlated single photon counting board is used for the parallel acquisition of time-resolved reflectance curves. Estimate of the reduced scattering coefficient is achieved by fitting with a standard model of diffusion theory, while the modified Lambert-Beer law is used to assess the absorption coefficient. In vivo measurements were performed on five healthy volunteers to monitor spatial changes in calf muscle (medial and lateral gastrocnemius; MG, LG) oxygen saturation (SmO2) and total haemoglobin concentration (tHb) during dynamic plantar flexion exercise performed at 50% of the maximal voluntary contraction. At rest SmO2 was 73.0 +/- 0.9 and 70.5 +/- 1.7% in MG and LG, respectively (P = 0.045). At the end of the exercise, SmO2 decreased (69.1 +/- 1.8 and 63.8 +/- 2.1% in MG and LG, respectively; P < 0.01). The LG desaturation was greater than the MG desaturation (P < 0.02). These results strengthen the role of time-resolved near-infrared spectroscopy as a powerful tool for investigating the spatial and temporal features of muscle SmO2 and tHb.

  17. Effect of ouabain on metabolic oxidative state in living cardiomyocytes evaluated by time-resolved spectroscopy of endogenous NAD(P)H fluorescence

    Science.gov (United States)

    Chorvatova, Alzbeta; Elzwiei, Fathia; Mateasik, Anton; Chorvat, Dusan

    2012-10-01

    Time-resolved spectrometry of endogenous nicotinamide dinucleotide phosphate [NAD(P)H] fluorescence is a useful method to evaluate metabolic oxidative state in living cells. Ouabain is a well-known pharmaceutical drug used in the treatment of cardiovascular disease, the effects of which on myocardial metabolism were recently demonstrated. Mechanisms implicated in these actions are still poorly understood. We investigate the effect of ouabain on the metabolic oxidative state of living cardiac cells identified by time-resolved fluorescence spectroscopy of mitochondrial NAD(P)H. Spectral unmixing is used to resolve individual NAD(P)H fluorescence components. Ouabain decreased the integral intensity of NAD(P)H fluorescence, leading to a reduced component amplitudes ratio corresponding to a change in metabolic state. We also noted that lactate/pyruvate, affecting the cytosolic NADH gradient, increased the effect of ouabain on the component amplitudes ratio. Cell oxidation levels, evaluated as the percentage of oxidized NAD(P)H, decreased exponentially with rising concentrations of the cardiac glycoside. Ouabain also stimulated the mitochondrial NADH production. Our study sheds a new light on the role that ouabain plays in the regulation of metabolic state, and presents perspective on a noninvasive, pharmaceutical approach for testing the effect of drugs on the mitochondrial metabolism by means of time-resolved fluorescence spectroscopy in living cells.

  18. Direct probing of charge carrier behavior in multilayered organic light-emitting diode devices by time-resolved electric-field-induced sum-frequency generation spectroscopy

    Science.gov (United States)

    Miyamae, Takayuki; Takada, Noriyuki; Ohata, Hiroshi; Tsutsui, Tetsuo

    2017-10-01

    Time-resolved electric-field-induced sum-frequency generation (EFI-SFG) spectroscopy was employed to study the charge behavior of multilayer organic light-emitting diodes (OLEDs). Through application of the square wave pulse bias to the OLEDs, compensation for the polarization charges in the electron transport layer and the generation of 4,4‧-bis[N-(1-naphthyl-N-phenylamino)-biphenyl] (α-NPD) cations were observed. When the pulse voltage was turned off, the α-NPD cations immediately disappeared, confirming that charge recombination occurs at the interfaces. We therefore concluded that time-resolved EFI-SFG is useful for directly probing the carrier behavior in OLEDs in addition to identifying the origin of the charge carriers present in OLEDs.

  19. Gauge invariance in the theoretical description of time-resolved angle-resolved pump/probe photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Freericks, J. K.; Krishnamurthy, H. R.; Sentef, M. A.; Devereaux, T. P.

    2015-10-01

    Nonequilibrium calculations in the presence of an electric field are usually performed in a gauge, and need to be transformed to reveal the gauge-invariant observables. In this work, we discuss the issue of gauge invariance in the context of time-resolved angle-resolved pump/probe photoemission. If the probe is applied while the pump is still on, one must ensure that the calculations of the observed photocurrent are gauge invariant. We also discuss the requirement of the photoemission signal to be positive and the relationship of this constraint to gauge invariance. We end by discussing some technical details related to the perturbative derivation of the photoemission spectra, which involve processes where the pump pulse photoexcites electrons due to nonequilibrium effects.

  20. Charge Carriers Modulate the Bonding of Semiconductor Nanoparticle Dopants As Revealed by Time-Resolved X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Asra; Zhang, Xiaoyi; Liu, Xiaohan; Rowland, Clare E. [Department; Jawaid, Ali M.; Chattopadhyay, Soma; Gulec, Ahmet; Shamirian, Armen; Zuo, Xiaobing; Klie, Robert F.; Schaller, Richard D. [Department; Snee, Preston T.

    2017-08-31

    Understanding the electronic structure of doped semiconductors is essential to realize advancements in electronics and in the rational design of nanoscale devices. Reported here are the results of time-resolved X-ray absorption studies on copper-doped cadmium sulfide nanoparticles that provide an explicit description of the electronic dynamics of the dopants. The interaction of a dopant ion and an excess charge carrier is unambiguously observed via monitoring the oxidation state. The experimental data combined with DFT calculations demonstrate that dopant bonding to the host matrix is modulated by its interaction with charge carriers. Furthermore, the transient photoluminescence and the kinetics of dopant oxidation reveal the presence of two types of surface-bound ions that create mid-gap states.

  1. Time-resolved soft X-ray absorption spectroscopy in transmission mode on liquids at MHz repetition rates

    Directory of Open Access Journals (Sweden)

    Mattis Fondell

    2017-09-01

    Full Text Available We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime. In combination with the wavelength tunability of the laser system, the set-up opens up opportunities to study the photochemistry of many systems at low concentrations, relevant to materials sciences, chemistry, and biology.

  2. Investigation of verbal and visual working memory by multi-channel time-resolved functional near-infrared spectroscopy

    Science.gov (United States)

    Contini, D.; Caffini, M.; Re, R.; Zucchelli, L.; Spinelli, L.; Basso Moro, S.; Bisconti, S.; Ferrari, M.; Quaresima, V.; Cutini, S.; Torricelli, A.

    2013-03-01

    Working memory (WM) is fundamental for a number of cognitive processes, such as comprehension, reasoning and learning. WM allows the short-term maintenance and manipulation of the information selected by attentional processes. The goal of this study was to examine by time-resolved fNIRS neural correlates of the verbal and visual WM during forward and backward digit span (DF and DB, respectively) tasks, and symbol span (SS) task. A neural dissociation was hypothesised between the maintenance and manipulation processes. In particular, a dorsolateral/ventrolateral prefrontal cortex (DLPFC/VLPFC) recruitment was expected during the DB task, whilst a lateralised involvement of Brodmann Area (BA) 10 was expected during the execution of the DF task. Thirteen subjects were monitored by a multi-channel, dual-wavelength (690 and 829 nm) time-resolved fNIRS system during 3 minutes long DF and DB tasks and 4 minutes long SS task. The participants' mean memory span was calculated for each task: DF: 6.46+/-1.05 digits; DB: 5.62+/-1.26 digits; SS: 4.69+/-1.32 symbols. No correlation was found between the span level and the heart rate data (measured by pulse oximeter). As expected, DB elicited a broad activated area, in the bilateral VLPFC and the right DLPFC, whereas a more localised activation was observed over the right hemisphere during either DF (BA 10) or SS (BA 10 and 44). The robust involvement of the DLPFC during DB, compared to DF, is compatible with previous findings and with the key role of the central executive subserving in manipulating processes.

  3. Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

    Science.gov (United States)

    Kang, Zhitao; Banishev, Alexandr A.; Lee, Gyuhyon; Scripka, David A.; Breidenich, Jennifer; Xiao, Pan; Christensen, James; Zhou, Min; Summers, Christopher J.; Dlott, Dana D.; Thadhani, Naresh N.

    2016-07-01

    The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersed in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.

  4. Time-resolved multi-mass ion imaging: Femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera

    Science.gov (United States)

    Forbes, Ruaridh; Makhija, Varun; Veyrinas, Kévin; Stolow, Albert; Lee, Jason W. L.; Burt, Michael; Brouard, Mark; Vallance, Claire; Wilkinson, Iain; Lausten, Rune; Hockett, Paul

    2017-07-01

    The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the particle time-of-flight is recorded along with (x, y) position. Coupling the PImMS camera to an ultrafast pump-probe velocity-map imaging spectroscopy apparatus therefore provides a route to time-resolved multi-mass ion imaging, with both high count rates and large dynamic range, thus allowing for rapid measurements of complex photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet wavelengths for the probe pulse allows for an enhanced observation window for the study of excited state molecular dynamics in small polyatomic molecules having relatively high ionization potentials. Herein, preliminary time-resolved multi-mass imaging results from C2F3I photolysis are presented. The experiments utilized femtosecond VUV and UV (160.8 nm and 267 nm) pump and probe laser pulses in order to demonstrate and explore this new time-resolved experimental ion imaging configuration. The data indicate the depth and power of this measurement modality, with a range of photofragments readily observed, and many indications of complex underlying wavepacket dynamics on the excited state(s) prepared.

  5. Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Zhitao [Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, Georgia 30332-0826 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Banishev, Alexandr A.; Christensen, James; Dlott, Dana D. [School of Chemical Sciences and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Lee, Gyuhyon; Scripka, David A.; Breidenich, Jennifer; Summers, Christopher J.; Thadhani, Naresh N., E-mail: naresh.thadhani@mse.gatech.edu [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Xiao, Pan [LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); Zhou, Min [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States)

    2016-07-28

    The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersed in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.

  6. Time-Resolved FT-IR Spectroscopy of CO Hydrogenation overSupported Ru Catalyst at 700K

    Energy Technology Data Exchange (ETDEWEB)

    Wasylenko, Walter; Frei, Heinz

    2006-02-13

    Time-resolved FT-IR spectra of carbon monoxide hydrogenation over alumina-supported ruthenium were recorded on the millisecond timescale at 703 K using various H{sub 2} concentrations (1 atm total pressure). Adsorbed carbon monoxide was detected along with gas phase products methane (3016 and 1306 cm{sup -1}), water (sharp bands from 1900 - 1300 cm{sup -1}), and carbon dioxide (2348 cm{sup -1}). No other surface species were detected other than adsorbed carbon monoxide. The rate of formation of methane (2.5 {+-} 0.4 s{sup -1}) coincides with the rate of formation of carbon dioxide (3.4 {+-} 0.6 s{sup -1}), and bands due to water are observed to grow in over time. These results establish that methane and carbon dioxide originate from the same intermediate. The adsorbed carbon monoxide band is broad and unsymmetrical with a maximum at 2010 cm{sup -1} in spectra observed at 36 ms that shifts over 3000 ms to 1960 cm{sup -1} due to decreasing amounts of adsorbed carbon monoxide. Kinetic analysis of the adsorbed carbon monoxide band reveals that only a portion of the band can be temporally linked to gas phase products that we observe over the first 1000 ms of catalysis. This result suggests that we are observing dispersive kinetics, which is most likely due to heterogeneity of the surface environment.

  7. Real-time baseline correction technique for MWIR and LWIR time-resolved photoluminescence spectroscopy (Presentation Recording)

    Science.gov (United States)

    Lin, Zhi-Yuan; Zhang, Yong-Hang

    2015-08-01

    The time-resolved photoluminescence (TRPL) measurement provides rich information about carrier dynamics and recombination mechanisms. However, TRPL measurements are quite challenging in mid-wave infrared (MWIR) and long-wave infrared (LWIR) regimes due to noise in photodetectors and data acquisition systems. Our analysis and experimental results show that the noise in a conventional TRPL system using a traditional averaging method is dominated by 1/f noise from 10 Hz to 3 kHz. The signal is also mixed with sub-Hertz noise associated with the boxcar baseline oscillation, commonly known as the "baseline drift" issue which results from numerous fluctuations in the system. A real-time baseline correction method is proposed and demonstrated to suppress these low frequency noise sources. The real-time baseline correction method is realized by modulating the signal. The modulation can be achieved by either electrical, mechanical, or optical approaches. Analysis indicates that the noise of this method is proportional to the noise spectral density at the modulation frequency, this argument is confirmed by the simulation results. The simulated noise achieved by the real-time baseline correction method is much lower than the traditional method. Experimental results show that the low frequency baseline oscillations associated with the traditional TRPL experiments are absent using the real-time baseline correction technique, and the noise of the measurement is significantly reduced. This work establishes a more efficient experimental method for TRPL measurements on weak MWIR and LWIR PL signals, such as the InAs/InAsSb type-II superlattice samples which are used here to demonstrate the proposed method.

  8. Mapping of calf muscle oxygenation and haemoglobin content during dynamic plantar flexion exercise by multi-channel time-resolved near-infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Torricelli, Alessandro [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Quaresima, Valentina [Department of Biomedical Sciences and Technologies, University of L' Aquila, I-67100 L' Aquila (Italy); Pifferi, Antonio [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Biscotti, Giovanni [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Spinelli, Lorenzo [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Taroni, Paola [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Ferrari, Marco [Department of Biomedical Sciences and Technologies, University of L' Aquila, I-67100 L' Aquila (Italy); Cubeddu, Rinaldo [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy)

    2004-03-07

    A compact and fast multi-channel time-resolved near-infrared spectroscopy system for tissue oximetry was developed. It employs semiconductor laser and fibre optics for delivery of optical signals. Photons are collected by eight 1 mm fibres and detected by a multianode photomultiplier. A time-correlated single photon counting board is used for the parallel acquisition of time-resolved reflectance curves. Estimate of the reduced scattering coefficient is achieved by fitting with a standard model of diffusion theory, while the modified Lambert-Beer law is used to assess the absorption coefficient. In vivo measurements were performed on five healthy volunteers to monitor spatial changes in calf muscle (medial and lateral gastrocnemius; MG, LG) oxygen saturation (SmO{sub 2}) and total haemoglobin concentration (tHb) during dynamic plantar flexion exercise performed at 50% of the maximal voluntary contraction. At rest SmO{sub 2} was 73.0 {+-} 0.9 and 70.5 {+-} 1.7% in MG and LG, respectively (P = 0.045). At the end of the exercise, SmO{sub 2} decreased (69.1 {+-} 1.8 and 63.8 {+-} 2.1% in MG and LG, respectively; P < 0.01). The LG desaturation was greater than the MG desaturation (P < 0.02). These results strengthen the role of time-resolved near-infrared spectroscopy as a powerful tool for investigating the spatial and temporal features of muscle SmO{sub 2} and tHb.

  9. Electronic resonances in broadband stimulated Raman spectroscopy

    Science.gov (United States)

    Batignani, G.; Pontecorvo, E.; Giovannetti, G.; Ferrante, C.; Fumero, G.; Scopigno, T.

    2016-01-01

    Spontaneous Raman spectroscopy is a formidable tool to probe molecular vibrations. Under electronic resonance conditions, the cross section can be selectively enhanced enabling structural sensitivity to specific chromophores and reaction centers. The addition of an ultrashort, broadband femtosecond pulse to the excitation field allows for coherent stimulation of diverse molecular vibrations. Within such a scheme, vibrational spectra are engraved onto a highly directional field, and can be heterodyne detected overwhelming fluorescence and other incoherent signals. At variance with spontaneous resonance Raman, however, interpreting the spectral information is not straightforward, due to the manifold of field interactions concurring to the third order nonlinear response. Taking as an example vibrational spectra of heme proteins excited in the Soret band, we introduce a general approach to extract the stimulated Raman excitation profiles from complex spectral lineshapes. Specifically, by a quantum treatment of the matter through density matrix description of the third order nonlinear polarization, we identify the contributions which generate the Raman bands, by taking into account for the cross section of each process.

  10. Hollow plasmonic antennas for broadband SERS spectroscopy

    Directory of Open Access Journals (Sweden)

    Gabriele C. Messina

    2015-02-01

    Full Text Available The chemical environment of cells is an extremely complex and multifaceted system that includes many types of proteins, lipids, nucleic acids and various other components. With the final aim of studying these components in detail, we have developed multiband plasmonic antennas, which are suitable for highly sensitive surface enhanced Raman spectroscopy (SERS and are activated by a wide range of excitation wavelengths. The three-dimensional hollow nanoantennas were produced on an optical resist by a secondary electron lithography approach, generated by fast ion-beam milling on the polymer and then covered with silver in order to obtain plasmonic functionalities. The optical properties of these structures have been studied through finite element analysis simulations that demonstrated the presence of broadband absorption and multiband enhancement due to the unusual geometry of the antennas. The enhancement was confirmed by SERS measurements, which showed a large enhancement of the vibrational features both in the case of resonant excitation and out-of-resonance excitation. Such characteristics indicate that these structures are potential candidates for plasmonic enhancers in multifunctional opto-electronic biosensors.

  11. Ionomer Dynamics: Insights from Broadband Dielectric Spectroscopy

    Science.gov (United States)

    Runt, James

    2015-03-01

    Ionomers (polymers containing ionic functionality) have been traditionally used as packaging materials and in molding applications, and are now of increasing interest as candidate single ion conductors for energy storage devices, in energy conversion, and for other electroactive materials applications. The focus of this presentation is on the insight that broadband dielectric (impedance) spectroscopy brings to our understanding of ion and polymer dynamics of this family of materials. As an example of our recent work on relatively conductive ionomers, the first portion of the presentation will focus on anion conducting polyphosphazene ionomers, in which polymer bound cations are quaternized with either short alkyl or short ether oxygen chains. The low Tg, amorphous nature, and cation-solvating backbone distinguish polyphosphazenes as promising materials for ion conduction, the iodide variants being of particular interest in solar cells. In the second part of this overview, the first findings on the molecular dynamics of linear precise polyethylene-based ionomers containing 1-methylimidazolium bromide pendants on exactly every 9th, 15th, or 21st carbon atom will be summarized. In order to develop a robust interpretation of the dynamics of these materials, it is imperative to develop a thorough understanding of microphase separation (e.g. ion aggregation), and each of the above studies is complimented by multiangle X-ray scattering experiments. Supported by the NSF Polymers Program and DOE Basic Energy Sciences.

  12. Time-resolved photoemission spectroscopy of electronic cooling and localization in CH3NH3PbI3 crystals

    Science.gov (United States)

    Chen, Zhesheng; Lee, Min-i.; Zhang, Zailan; Diab, Hiba; Garrot, Damien; Lédée, Ferdinand; Fertey, Pierre; Papalazarou, Evangelos; Marsi, Marino; Ponseca, Carlito; Deleporte, Emmanuelle; Tejeda, Antonio; Perfetti, Luca

    2017-09-01

    We measure the surface of CH3NH3PbI3 single crystals by making use of two-photon photoemission spectroscopy. Our method monitors the electronic distribution of photoexcited electrons, explicitly discriminating the initial thermalization from slower dynamical processes. The reported results disclose the fast-dissipation channels of hot carriers (0.25 ps), set an upper bound to the surface-induced recombination velocity (solar cells to the theoretical limit.

  13. Time-resolved characterization of a filamentary argon discharge at atmospheric pressure in a capillary using emission and absorption spectroscopy

    Science.gov (United States)

    Schröter, Sandra; Pothiraja, Ramasamy; Awakowicz, Peter; Bibinov, Nikita; Böke, Marc; Niermann, Benedikt; Winter, Jörg

    2013-11-01

    An argon/nitrogen (0.999/0.001) filamentary pulsed discharge operated at atmospheric pressure in a quartz tube is characterized using voltage-current measurements, microphotography, optical emission spectroscopy (OES) and absorption spectroscopy. Nitrogen is applied as a sensor gas for the purpose of OES diagnostic. The density of argon metastable atoms Ar(3P2) is determined using tunable diode laser absorption spectroscopy (TDLAS). Using a plasma chemical model the measured OES data are applied for the characterization of the plasma conditions. Between intense positive pulses the discharge current oscillates with a damped amplitude. It is established that an electric current flows in this discharge not only through a thin plasma filament that is observed in the discharge image but also through the whole cross section of the quartz tube. A diffuse plasma fills the quartz tube during a time between intense current pulses. Ionization waves are propagating in this plasma between the spike and the grounded area of the tube producing thin plasma channels. The diameter of these channels increases during the pause between the propagation of ionization waves probably because of thermal expansion and diffusion. Inside the channels electron densities of ˜2 × 1013 cm-3, argon metastable densities ˜1014 cm-3 and a reduced electric field about 10 Td are determined.

  14. Kinetics of the laser-induced solid phase crystallization of amorphous silicon-Time-resolved Raman spectroscopy and computer simulations

    Science.gov (United States)

    Očenášek, J.; Novák, P.; Prušáková, L.

    2017-01-01

    This study demonstrates that a laser-induced crystallization instrumented with Raman spectroscopy is, in general, an effective tool to study the thermally activated crystallization kinetics. It is shown, for the solid phase crystallization of an amorphous silicon thin film, that the integral intensity of Raman spectra corresponding to the crystalline phase grows linearly in the time-logarithmic scale. A mathematical model, which assumes random nucleation and crystal growth, was designed to simulate the crystallization process in the non-uniform temperature field induced by laser. The model is based on solving the Eikonal equation and the Arhenius temperature dependence of the crystal nucleation and the growth rate. These computer simulations successfully approximate the crystallization process kinetics and suggest that laser-induced crystallization is primarily thermally activated.

  15. Review of the theoretical description of time-resolved angle-resolved photoemission spectroscopy in electron-phonon mediated superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kemper, A.F. [Department of Physics, North Carolina State University, Raleigh, NC (United States); Sentef, M.A. [Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Hamburg (Germany); Moritz, B. [Stanford Institute for Materials and Energy Sciences (SIMES), SLAC National Accelerator Laboratory, Menlo Park, CA (United States); Devereaux, T.P. [Stanford Institute for Materials and Energy Sciences (SIMES), SLAC National Accelerator Laboratory, Menlo Park, CA (United States); Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA (United States); Freericks, J.K. [Department of Physics, Georgetown University, Washington, DC (United States)

    2017-09-15

    We review recent work on the theory for pump/probe photoemission spectroscopy of electron-phonon mediated superconductors in both the normal and the superconducting states. We describe the formal developments that allow one to solve the Migdal-Eliashberg theory in nonequilibrium for an ultrashort laser pumping field, and explore the solutions which illustrate the relaxation as energy is transferred from electrons to phonons. We focus on exact results emanating from sum rules and approximate numerical results which describe rules of thumb for relaxation processes. In addition, in the superconducting state, we describe how Anderson-Higgs oscillations can be excited due to the nonlinear coupling with the electric field and describe mechanisms where pumping the system enhances superconductivity. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Hilbert-space treatment of incoherent, time-resolved spectroscopy. I. Formalism, a tensorial classification of high-order orientational gratings and generalized MUPPETS "echoes".

    Science.gov (United States)

    Berg, Mark A

    2010-04-14

    Time-resolved spectroscopy that uses more than one incoherent excitation, and thus has multiple periods of time evolution, is becoming more common. A recent example is multiple population-period transient spectroscopy (MUPPETS), which is implemented as a high-order transient grating. In this paper, a formalism is developed to treat these types of incoherent spectroscopy in a manner that parallels the Liouville-pathway formalism used to treat multidimensional coherent spectroscopy. A Hilbert space of incoherent (population) states is defined and general expressions for transition and time-evolution operators acting on these states are derived from the corresponding quantum operators. This formalism describes incoherent experiments that involve an arbitrary number of temporal dimensions in terms of pathways through the Hilbert space. Each pathway is associated with a multiple-time rate-correlation function. Previous work has shown that these multiple-time correlation functions can measure heterogeneity in electronic-relaxation rates. Thus, they are an analog of coherent "echo" experiments, which measure heterogeneity in frequencies. We show that similar "MUPPETS echo" experiments can be done on any incoherent variable. For a dilute molecular solute, the Hilbert-space method leads to a systematic treatment of multidimensional transient gratings. The extension of irreducible-tensor methods to the incoherent Hilbert space results in a classification of orientational gratings of arbitrary order. The general methods developed in this paper are applied more specifically to single-photon, dipole transitions in the following paper.

  17. Time-resolved granular dynamics of a rotating drum in a slumping regime as revealed by speckle visibility spectroscopy

    Directory of Open Access Journals (Sweden)

    Zivkovic V.

    2017-01-01

    Full Text Available Granular materials in rotating drums are of wide interest not only because of their extensive use in the industrial contexts, but also as model systems in the study of natural disasters, such as avalanches or landslides. Most of available experimental methods are restricted to surface layer flows and dilute systems whilst the remainder can only resolve the granular dynamics to a fine scale with relatively poor temporal resolution or vice versa. In contrast, speckle visibility spectroscopy (SVS is able to resolve the average of the three components of motion of grains in dense systems in small volume of granular media several layer deep with spatio-temporal resolutions that allow the probing of the granular micro-dynamics. We have used this technique to study granular dynamics of surface avalanche flow in the slumping regime using both spherical glass and irregular sand particles. Although results are very similar, we determined that visually observed compaction at the beginning of avalanche process for irregular sand particles influence time evolution of the particle fluctuation velocity during avalanches.

  18. Kinetics of the laser-induced solid phase crystallization of amorphous silicon—Time-resolved Raman spectroscopy and computer simulations

    Energy Technology Data Exchange (ETDEWEB)

    Očenášek, J., E-mail: ocenasek@ntc.zcu.cz; Novák, P.; Prušáková, L.

    2017-01-15

    Highlights: • Mathematical model for crystallization in a non-uniform temp. field was designed. • Quantitative analyses of Raman spectra are presented. • Analyses of the crystallization kinetics using laser irradiation are introduced. • Laser-induced crystallization kinetics of a-Si thin film was analyzed in detail. - Abstract: This study demonstrates that a laser-induced crystallization instrumented with Raman spectroscopy is, in general, an effective tool to study the thermally activated crystallization kinetics. It is shown, for the solid phase crystallization of an amorphous silicon thin film, that the integral intensity of Raman spectra corresponding to the crystalline phase grows linearly in the time-logarithmic scale. A mathematical model, which assumes random nucleation and crystal growth, was designed to simulate the crystallization process in the non-uniform temperature field induced by laser. The model is based on solving the Eikonal equation and the Arhenius temperature dependence of the crystal nucleation and the growth rate. These computer simulations successfully approximate the crystallization process kinetics and suggest that laser-induced crystallization is primarily thermally activated.

  19. Time-resolved granular dynamics of a rotating drum in a slumping regime as revealed by speckle visibility spectroscopy

    Science.gov (United States)

    Zivkovic, V.; Yang, H.; Zheng, G.; Biggs, M.

    2017-06-01

    Granular materials in rotating drums are of wide interest not only because of their extensive use in the industrial contexts, but also as model systems in the study of natural disasters, such as avalanches or landslides. Most of available experimental methods are restricted to surface layer flows and dilute systems whilst the remainder can only resolve the granular dynamics to a fine scale with relatively poor temporal resolution or vice versa. In contrast, speckle visibility spectroscopy (SVS) is able to resolve the average of the three components of motion of grains in dense systems in small volume of granular media several layer deep with spatio-temporal resolutions that allow the probing of the granular micro-dynamics. We have used this technique to study granular dynamics of surface avalanche flow in the slumping regime using both spherical glass and irregular sand particles. Although results are very similar, we determined that visually observed compaction at the beginning of avalanche process for irregular sand particles influence time evolution of the particle fluctuation velocity during avalanches.

  20. Sub-picosecond time resolved infrared spectroscopy of high-spin state formation in Fe(II) spin crossover complexes

    DEFF Research Database (Denmark)

    Døssing, Anders Rørbæk; Wolf, Matthias M. N.; Gross, Ruth

    2008-01-01

      The photoinduced low-spin (S = 0) to high-spin (S = 2) transition of the iron(II) spin-crossover systems [Fe(btpa)](PF6)2 and [Fe(b(bdpa))](PF6)2 in solution have been studied for the first time by means of ultrafast transient infrared spectroscopy at room temperature. Negative and positive...... infrared difference bands between 1000 and 1065 cm-1 that appear within the instrumental system response time of 350 fs after excitation at 387 nm display the formation of the vibrationally unrelaxed and hot high-spin 5T2 state. Vibrational relaxation is observed and characterized by the time constants 9.......4 ± 0.7 ps for [Fe(btpa)](PF6)2/acetone and 12.7 ± 0.7 ps for both [Fe(btpa)](PF6)2/acetonitrile and [Fe(b(bdpa)](PF6)2/acetonitrile. Vibrational analysis has been performed via DFT calculations of the low-spin and high-spin state normal modes of both compounds as well as their respective infrared...

  1. Photoexcitation Dynamics of Thymine in Acetonitrile and an Ionic Liquid Probed by Time-resolved Infrared Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Arpan; Park, Seongchul; Lee, Taegon; Lim, Manho [Pusan National University, Busan(Korea, Republic of)

    2016-07-15

    Femtosecond transient IR absorption spectroscopy was used to probe the decay mechanism of electronically excited thymine (a naturally occurring pyrimidine base in DNA) dissolved in an ionic liquid ([Bmim][BF{sub 4}]) or CD{sub 3}CN after the absorption of UV light (267 nm). In both solvents, an absorption band grew on a picosecond timescale, along with decaying bleach and evolving red-shifted absorption signals. A population analysis of the observed kinetic data suggested that most of the photoexcited thymine underwent a sub-picosecond non-radiative relaxation to the vibrationally hot ground electronic state. About 4% (16%) of the excited thymine in the ionic liquid (CD{sub 3}CN) relaxed to an intermediate electronic state, which relaxed into a low-lying triplet state by intersystem crossing (ISC) (ISC did not relax to the ground electronic state within the experimental period (1 ns)). The low ISC yield for thymine in an ionic liquid was correlated with molecular properties of the solvent. This observation is significant because the ISC to triplet state transition for excited thymine has been considered as a precursor to cyclobutane-pyrimidine dimer formation, which led to functional damage of the base after UV absorption. This finding may shed light on the photostability of DNA in ionic liquids.

  2. Femtosecond dynamics of electronic states in the Mott insulator 1T-TaS{sub 2} by time resolved photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Perfetti, L; Loukakos, P A; Lisowski, M; Bovensiepen, U; Wolf, M [Fachbereich Physik, Freie Universitaet Berlin, Arnimallee 14, 14195 Berlin (Germany); Berger, H [Institut de Physique de la Matiere Complexe, EPFL, CH-1015 Lausanne (Switzerland); Biermann, S; Georges, A [Centre de Physique Theorique, Ecole Polytechnique, 91128 Palaiseau Cedex (France)], E-mail: perfetti@physik.fu-berlin.de

    2008-05-15

    Photoexcitation of the Mott insulator 1T-TaS{sub 2} by an intense laser pulse leads to an ultrafast transition toward a gapless phase. Besides the collapse of the electronic gap, the sudden excitation of the charge density wave (CDW) mode results in periodic oscillations of the electronic states. We employ time resolved photoelectron spectroscopy to monitor the rich dynamics of electrons and phonons during the relaxation toward equilibrium. The qualitative difference between the oscillatory dynamics of the CDW and the monotonic recovery of the electronic gap proves that 1T-TaS{sub 2} is indeed a Mott insulator. Moreover the quasi-instantaneous build-up of mid gap states is in contrast with the retarded response expected from a Peierls insulating phase. Interestingly, the photoinduced electronic states in the midgap spectral region display a weak resonance that is reminiscent of a quasiparticle peak.

  3. Time-resolved soft-x-ray spectroscopy of a magnetic octupole transition in nickel-like xenon, cesium, and barium ions

    Energy Technology Data Exchange (ETDEWEB)

    Trabert, E; Beiersdorfer, P; Brown, G V; Boyce, K; Kelley, R L; Kilbourne, C A; Porter, F S; Szymkowiak, A

    2005-11-11

    A microcalorimeter with event mode capability for time-resolved soft-x-ray spectroscopy, and a high-resolution flat-field EUV spectrometer have been employed at the Livermore EBIT-I electron beam ion trap for observations and wavelength measurements of M1, E2, and M3 decays of long-lived levels in the Ni-like ions Xe{sup 26+}, Cs{sup 27+}, and Ba{sup 28+}. Of particular interest is the lowest excited level, 3d{sup 9}4s {sup 3}D{sub 3}, which can only decay via a magnetic octupole (M3) transition. For this level in Xe an excitation energy of (590.40 {+-} 0.03eV) and a level lifetime of (11.5 {+-} 0.5 ms) have been determined.

  4. Static and time-resolved mid-infrared spectroscopy of Hg0.95Cd0.05Cr2Se4 spinel

    Science.gov (United States)

    Barsaume, S.; Telegin, A. V.; Sukhorukov, Yu P.; Stavrias, N.; Fedorov, V. A.; Menshchikova, T. K.; Kimel, A. V.

    2017-08-01

    Static and time-resolved mid-infrared spectroscopy of ferromagnetic single crystal Hg0.95Cd0.05Cr2Se4 was performed below the absorption edge, in order to reveal the origin of the electronic transitions contributing to the magneto-optical properties of this material. The mid-infrared spectroscopy reveals a strong absorption peak around 0.236 eV which formerly was assigned to a transition within the selenide-chromium complexes (ν Se-Cr2+). To reveal the sensitivity of the transition to the magnetic order, we performed the studies in a temperature range across the Curie temperature and magnetic fields across the value at which the saturation of ferromagnetic magnetization occurs. Despite the fact that the Curie temperature of this ferromagnetic semiconductor is around 107 K, the intensity of the mid-infrared transition reduces substantially increasing the temperature, so that already at 70 K the absorption peak is hardly visible. Such a dramatic decrease of the oscillator strength is observed simultaneously with the strong red-shift of the absorption edge in the magnetic semiconductor. Employing a time-resolved pump-and-probe technique enabled us to determine the lifetime of the electrons in the excited state of this optical transition. In the temperature range from 7 K to 80 K, the lifetime changes from 3 ps to 6 ps. This behavior agrees with the phenomenon of giant oscillator strength described earlier for weakly bound excitons in nonmagnetic semiconductors.

  5. Comparison of TiO₂ and ZnO solar cells sensitized with an indoline dye: time-resolved laser spectroscopy studies of partial charge separation processes.

    Science.gov (United States)

    Sobuś, Jan; Burdziński, Gotard; Karolczak, Jerzy; Idígoras, Jesús; Anta, Juan A; Ziółek, Marcin

    2014-03-11

    Time-resolved laser spectroscopy techniques in the time range from femtoseconds to seconds were applied to investigate the charge separation processes in complete dye-sensitized solar cells (DSC) made with iodide/iodine liquid electrolyte and indoline dye D149 interacting with TiO2 or ZnO nanoparticles. The aim of the studies was to explain the differences in the photocurrents of the cells (3-4 times higher for TiO2 than for ZnO ones). Electrochemical impedance spectroscopy and nanosecond flash photolysis studies revealed that the better performance of TiO2 samples is not due to the charge collection and dye regeneration processes. Femtosecond transient absorption results indicated that after first 100 ps the number of photoinduced electrons in the semiconductor is 3 times higher for TiO2 than for ZnO solar cells. Picosecond emission studies showed that the lifetime of the D149 excited state is about 3 times longer for ZnO than for TiO2 samples. Therefore, the results indicate that lower performance of ZnO solar cells is likely due to slower electron injection. The studies show how to correlate the laser spectroscopy methodology with global parameters of the solar cells and should help in better understanding of the behavior of alternative materials for porous electrodes for DSC and related devices.

  6. Graphical programming for broadband pulse NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Belmonte, S.B. [Universidade do Estado (UERJ), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Eletronica; Oliveira, I.S.; Guimaraes, A.P. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1997-12-31

    In a broadband pulsed nuclear magnetic resonance (NMR) spectrometer we often need to sweep the excitation frequency over a wide range, and acquire the spin echo components in quadrature for further spectral analysis. Computer languages such as C or Pascal have been traditionally applied to the development of software control of laboratory equipment, and consequently, the automatization of NMR experiments. However, the use of graphical languages have proved to be a flexible and convenient way for experiment and data acquisition control. In our application we use the graphical language Labview for the automatic control of a broadband pulse NMR spectrometer, dedicated to the study of magnetic metal systems. (author) 2 refs., 2 figs.

  7. Study on the interaction of phthalate esters to human serum albumin by steady-state and time-resolved fluorescence and circular dichroism spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xiaoyun [National Key Laboratory of Organic Chemistry, Lanzhou University, Lanzhou 730000 (China); College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000 (China); Wang, Zhaowei [College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000 (China); Zhou, Ximin; Wang, Xiaoru [National Key Laboratory of Organic Chemistry, Lanzhou University, Lanzhou 730000 (China); Chen, Xingguo, E-mail: chenxg@lzu.edu.cn [National Key Laboratory of Organic Chemistry, Lanzhou University, Lanzhou 730000 (China); Department of Chemistry, Lanzhou University, Lanzhou 730000 (China)

    2011-09-15

    Highlights: {center_dot} Molecular docking revealed PAEs to be located in the hydrophobic pocket of HSA. {center_dot} HSA-DMP had one class of binding sites while HSA-BBP and HSA-DEHP had two types. {center_dot} Hydrophobic and hydrogen interactions dominated in the association of HSA-PAEs. {center_dot} The lifetime of Trp residue of HSA decreased after the addition of PAEs. {center_dot} The presences of PAEs could alter the second structure of HSA. - Abstract: Phthalate esters (PAEs) are globally pervasive contaminants that are considered to be endocrine disruptor chemicals and toxic environmental priority pollutants. In this paper, the interactions between PAEs and human serum albumin (HSA) were examined by molecular modelling, steady state and time-resolved fluorescence, ultraviolet-visible spectroscopy (UV-vis) and circular dichroism spectroscopy (CD). The association constants between PAEs and HSA were determined using the Stern-Volmer and Scatchard equations. The binding of dimethyl phthalate (DMP) to HSA has a single class of binding site and its binding constants (K) are 4.08 x 10{sup 3}, 3.97 x 10{sup 3}, 3.45 x 10{sup 3}, and 3.20 x 10{sup 3} L mol{sup -1} at 289, 296, 303, and 310 K, respectively. The Stern-Volmer and Scatchard plots both had two regression curves for HSA-butylbenzyl phthalate (BBP) and HSA-di-2-ethylhexyl phthalate (DEHP), which indicated that these bindings were via two types of binding sites: the numbers of binding site for the first type were lower than for the second type. The binding constants of the first type binding site were higher than those of the second type binding site at corresponding temperatures, the results suggesting that the first type of binding site had high affinity and the second binding site involved other sites with lower binding affinity and selectivity. The thermodynamic parameters of the binding reactions ({Delta}G{sup o}, {Delta}H{sup o} and {Delta}S{sup o}) were measured, and they indicated the presences

  8. Diffusion and molecular interactions in a methanol/polyimide system probed by coupling time-resolved FTIR spectroscopy with gravimetric measurements.

    Science.gov (United States)

    Musto, Pellegrino; Galizia, Michele; La Manna, Pietro; Pannico, Marianna; Mensitieri, Giuseppe

    2014-01-01

    In this contribution the diffusion of methanol in a commercial polyimide (PMDA-ODA) is studied by coupling gravimetric measurements with in-situ, time-resolved FTIR spectroscopy. The spectroscopic data have been treated with two complementary techniques, i.e., difference spectroscopy (DS) and least-squares curve fitting (LSCF). These approaches provided information about the overall diffusivity, the nature of the molecular interactions among the system components and the dynamics of the various molecular species. Additional spectroscopic measurements on thin film samples (about 2 μm) allowed us to identify the interaction site on the polymer backbone and to propose likely structures for the H-bonding aggregates. Molar absorptivity values from a previous literature report allowed us to estimate the population of first-shell and second-shell layers of methanol in the polymer matrix. In terms of diffusion kinetics, the gravimetric and spectroscopic estimates of the diffusion coefficients were found to be in good agreement with each other and with previous literature reports. A Fickian behavior was observed throughout, with diffusivity values markedly affected by the total concentration of sorbed methanol.

  9. Lifetime, mobility, and diffusion of photoexcited carriers in ligand-exchanged lead selenide nanocrystal films measured by time-resolved terahertz spectroscopy.

    Science.gov (United States)

    Guglietta, Glenn W; Diroll, Benjamin T; Gaulding, E Ashley; Fordham, Julia L; Li, Siming; Murray, Christopher B; Baxter, Jason B

    2015-02-24

    Colloidal semiconductor nanocrystals have been used as building blocks for electronic and optoelectronic devices ranging from field-effect transistors to solar cells. Properties of the nanocrystal films depend sensitively on the choice of capping ligand to replace the insulating synthesis ligands. Thus far, ligands leading to the best performance in transistors result in poor solar cell performance, and vice versa. To gain insight into the nature of this dichotomy, we used time-resolved terahertz spectroscopy measurements to study the mobility and lifetime of PbSe nanocrystal films prepared with five common ligand-exchange reagents. Noncontact terahertz spectroscopy measurements of conductivity were corroborated by contacted van der Pauw measurements of the same samples. The films treated with different displacing ligands show more than an order of magnitude difference in the peak conductivities and a bifurcation of time dynamics. Inorganic chalcogenide ligand exchanges with sodium sulfide (Na2S) or ammonium thiocyanate (NH4SCN) show high mobilities but nearly complete decay of transient photocurrent in 1.4 ns. In contrast, ligand exchanges with 1,2-ethylenediamine (EDA), 1,2-ethanedithiol (EDT), and tetrabutylammonium iodide (TBAI) show lower mobilities but longer carrier lifetimes, resulting in longer diffusion lengths. This bifurcated behavior may explain the divergent performance of field-effect transistors and photovoltaics constructed from nanocrystal building blocks with different ligand exchanges.

  10. Probing the influence of X-rays on aqueous copper solutions using time-resolved in situ combined video/X-ray absorption near-edge/ultraviolet-visible spectroscopy

    NARCIS (Netherlands)

    Mesu, J. Gerbrand; Beale, Andrew M.|info:eu-repo/dai/nl/325802068; de Groot, Frank M. F.|info:eu-repo/dai/nl/08747610X; Weckhuysen, Bert M.|info:eu-repo/dai/nl/285484397

    2006-01-01

    Time-resolved in situ video monitoring and ultraviolet-visible spectroscopy in combination with X-ray absorption near-edge spectroscopy (XANES) have been used for the first time in a combined manner to study the effect of synchrotron radiation on a series of homogeneous aqueous copper solutions in a

  11. Spectral characterization of crude oil using fluorescence (synchronous and time-resolved) and NIR (Near Infrared Spectroscopy); Caracterizacao espectral do petroleo utilizando fluorescencia (sincronizada e resolvida no tempo) e NIR (Near Infrared Spectroscopy)

    Energy Technology Data Exchange (ETDEWEB)

    Falla Sotelo, F.; Araujo Pantoja, P.; Lopez-Gejo, J.; Le Roux, G.A.C.; Nascimento, C.A.O. [Universidade de Sao Paulo (USP), SP (Brazil). Dept. de Engenharia Quimica. Lab. de Simulacao e Controle de Processos; Quina, F.H. [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Quimica. Centro de Capacitacao e Pesquisa em Meio Ambiente (CEPEMA)

    2008-07-01

    The objective of the present work is to evaluate the performance of two spectroscopic techniques employed in the crude oil characterization: NIR spectroscopy and fluorescence spectroscopy (Synchronous fluorescence - SF and Time Resolved Fluorescence - TRF) for the development of correlation models between spectral profiles of crude oil samples and both physical properties (viscosity and API density) and physico-chemical properties (SARA analysis: Saturated, Aromatic, Resins and Asphaltenes). The better results for viscosity and density were obtained using NIR whose prediction capacity was good (1.5 cP and 0.5 deg API, respectively). For SARA analysis, fluorescence spectroscopy revealed its potential in the model calibration showing good results (R2 coefficients greater than 0.85). TRF spectroscopy had better performance than SF spectroscopy. (author)

  12. Time-resolved photoluminescence and photoreflectance spectroscopy of GaN layers grown on SiN-treated sapphire substrate: Optical properties evolution at different growth stages

    Science.gov (United States)

    Bouzidi, M.; Soltani, S.; Chine, Z.; Rebey, A.; Shakfa, M. K.

    2017-11-01

    In this paper, we present a systematic study of the optical properties evolution of GaN films during the complete growth process on SiN-treated sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy. The growth process was monitored using in-situ laser reflectometry and was interrupted at different stages to obtain the studied samples. The obtained samples were ex-situ characterized by means of photoluminescence (PL), photoreflectance (PR) and time-resolved PL (TRPL) spectroscopies. The PL emission from the samples of the initial growth stages originates from nano-crystallite and defect states due to the 3D growth mode. However, with increasing layer thickness, the 2D growth mode is established, and the PL spectrum is dominated by free-exciton emission. The electric field extracted by applying the Franz-Keldysh oscillation (FKO) theory on the PR spectra shows a trend to decrease as the GaN layer thickness is increased. For fully coalesced layers, the FKO totally disappears, and the PR spectrum is dominated by free-exciton transitions. TRPL measurements demonstrate the contribution of two processes to the PL decay, i.e., fast and slow components. While the slow decay time reveals the same sensitivity to different types of dislocations (twist and tilt mosaics), the fast decay time is more affected by the twist mosaic than by the tilt one.

  13. Surface speciation of Eu3+ adsorbed on kaolinite by time-resolved laser fluorescence spectroscopy (TRLFS) and parallel factor analysis (PARAFAC).

    Science.gov (United States)

    Ishida, Keisuke; Saito, Takumi; Aoyagi, Noboru; Kimura, Takaumi; Nagaishi, Ryuji; Nagasaki, Shinya; Tanaka, Satoru

    2012-05-15

    Time-resolved laser fluorescence spectroscopy (TRLFS) is an effective speciation technique for fluorescent metal ions and can be further extended by the parallel factor analysis (PARAFAC). The adsorption of Eu(3+) on kaolinite as well as gibbsite as a reference mineral was investigated by TRLFS together with batch adsorption measurements. The PAFAFAC modeling provided the fluorescence spectra, decay lifetimes, and relative intensity profiles of three Eu(3+) surface complexes with kaolinite; an outer-sphere (factor A) complex and two inner-sphere (factors B and C) complexes. Their intensity profiles qualitatively explained the measured adsorption of Eu(3+). Based on the TRLFS results in varied H(2)O/D(2)O media, it was shown that the outer-sphere complex exhibited more rapid fluorescence decay than Eu(3+) aquo ion, because of the energy transfer to the surface. Factor B was an inner-sphere complex, which became dominant at relatively high pH, high salt concentration and low Eu(3+) concentration. Its spectrum and lifetime were similar to those of Eu(3+) adsorbed on gibbsite, suggesting its occurrence on the edge face of the gibbsite layer of kaolinite. From the comparison with the spectra and lifetimes of crystalline or aqueous Eu(OH)(3), factor C was considered as a poly-nuclear surface complex of Eu(3+) formed at relatively high Eu(3+) concentration. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Conformation transition in silk protein films monitored by time-resolved Fourier transform infrared spectroscopy: effect of potassium ions on Nephila spidroin films.

    Science.gov (United States)

    Chen, Xin; Knight, David P; Shao, Zhengzhong; Vollrath, Fritz

    2002-12-17

    We used time-resolved Fourier transform infrared spectroscopy (FTIR) to follow a conformation transition in Nephila spidroin film from random coil and/or helical structures to beta-sheet induced by the addition of KCl from 0.01 to 1.0 mol/L in D(2)O. Time series difference spectra showed parallel increases in absorption at 1620 and 1691 cm(-)(1), indicating formation of beta-sheet, together with a coincident loss of intensity of approximately 1650 cm(-)(1), indicating decrease of random coil and/or helical structures. Increase in KCl concentration produced an increased rate of the conformation transition that may attributable to weakening of hydrogen bonds within spidroin macromolecules. The conformation transition was a biphasic process with [KCl] > or = 0.3 mol/L but monophasic with [KCl] < or = 0.1 mol/L. This suggests that, at high KCl concentrations, segments of the molecular chain are adjusted first and then the whole molecule undergoes rearrangement. We discuss the possible significance of these findings to an understanding of the way that spiders spin silk.

  15. Vibrational Spectrum of an Excited State and Huang-Rhys Factors by Coherent Wave Packets in Time-Resolved Fluorescence Spectroscopy.

    Science.gov (United States)

    Lee, Gyeongjin; Kim, Junwoo; Kim, So Young; Kim, Dong Eon; Joo, Taiha

    2017-03-17

    Coherent nuclear wave packet motions in an electronic excited state of a molecule are measured directly by time-resolved spontaneous fluorescence spectroscopy with an unprecedented time resolution by using two-photon absorption excitation and fluorescence upconversion by noncollinear sum frequency generation. With an estimated time resolution of approximately 25 fs, wave packet motions of vibrational modes up to 1600 cm(-1) are recorded for coumarin 153 in ethanol. Two-color transient absorption at 13 fs time resolution are measured to confirm the result. Vibrational displacements between the ground and excited states and Huang-Rhys factors (HRFs) are calculated by quantum mechanical methods and are compared with the experimental results. HRFs calculated by density functional theory (DFT) and time-dependent DFT reproduce the experiment adequately. This fluorescence-based method provides a unique and direct way to obtain the vibrational spectrum of a molecule in an electronic excited state and the HRFs, as well as the dynamics of excited states, and it might provide information on the structure of an excited state through the HRFs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Analysis of time resolved femtosecond and femtosecond/picosecond coherent anti-Stokes Raman spectroscopy: Application to toluene and Rhodamine 6G

    Science.gov (United States)

    Niu, Kai; Lee, Soo-Y.

    2012-02-01

    The third-order polarization for coherent anti-Stokes Raman scattering (CARS) from a pure state is described by 48 terms in perturbation theory, but only 4 terms satisfy the rotating wave approximation. They are represented by Feynman dual time-line diagrams and four-wave mixing energy level diagrams. In time-resolved (tr) fs and fs/ps CARS from the ground vibrational state, one resonant diagram, which is the typical CARS term, with three field interactions—pump, Stokes, followed by probe—on the ket is dominant. Using the separable, displaced harmonic oscillators approximation, an analytic result is obtained for the four-time correlation function in the CARS third-order polarization. Dlott's phenomenological expression for off-resonance CARS from the ground vibrational state is derived using a three-state model. We calculated the tr fs and fs/ps CARS for toluene and Rhodamine 6G (R6G), initially in the ground vibrational state, to compare with experimental results. The observed vibrational features and major peaks for both tr fs and fs/ps CARS, from off-resonance (for toluene) to resonance (for R6G) pump wavelengths, can be well reproduced by the calculations. The connections between fs/ps CARS, fs stimulated Raman spectroscopy, and impulsive stimulated scattering for toluene and R6G are discussed.

  17. Fulvic acid complexation of Eu(III) and Cm(III) at elevated temperatures studied by time-resolved laser fluorescence spectroscopy.

    Science.gov (United States)

    Fröhlich, Daniel R; Skerencak-Frech, Andrej; Gast, Michael; Panak, Petra J

    2014-11-07

    The interaction of Eu(III) and Cm(III) with three different aquatic fulvic acids (FA) was studied as a function of the temperature (T = 20-80 °C) in 0.1 M NaCl solution by time-resolved laser fluorescence spectroscopy. The speciation of both trivalent metal ions was determined by peak deconvolution of the recorded fluorescence spectra. For each studied metal ion-FA system only one complexed species is formed under the given experimental conditions. The stability constants at 20, 40, 60 and 80 °C (log β'(T)) were determined according to the charge neutralization model. The log β' (20 °C) for the different FAs show similar values (log β(20 °C) = 5.60-6.29). The stability constants increase continuously with increasing temperature by approximately 0.3-1.0 orders of magnitude. The reaction enthalpies and entropies are derived from the integrated Van't Hoff equation. The results show that all investigated complexation reactions are endothermic and entropy-driven.

  18. Photo-Induced Spin-State Conversion in Solvated Transition Metal Complexes Probed via Time-Resolved Soft X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huse, Nils; Kim, Tae Kyu; Jamula, Lindsey; McCusker, James K.; de Groot, Frank M. F.; Schoenlein, Robert W.

    2010-04-30

    Solution-phase photoinduced low-spin to high-spin conversion in the FeII polypyridyl complex [Fe(tren(py)3)]2+ (where tren(py)3 is tris(2-pyridylmethyliminoethyl)amine) has been studied via picosecond soft X-ray spectroscopy. Following 1A1 --> 1MLCT (metal-to-ligand charge transfer) excitation at 560 nm, changes in the iron L2- and L3-edges were observed concomitant with formation of the transient high-spin 5T2 state. Charge-transfer multiplet calculations coupled with data acquired on low-spin and high-spin model complexes revealed a reduction in ligand field splitting of 1 eV in the high-spin state relative to the singlet ground state. A significant reduction in orbital overlap between the central Fe-3d and the ligand N-2p orbitals was directly observed, consistent with the expected ca. 0.2 Angstrom increase in Fe-N bond length upon formation of the high-spin state. The overall occupancy of the Fe-3d orbitals remains constant upon spin crossover, suggesting that the reduction in sigma-donation is compensated by significant attenuation of pi-back-bonding in the metal-ligand interactions. These results demonstrate the feasibility and unique potential of time-resolved soft X-ray absorption spectroscopy to study ultrafast reactions in the liquid phase by directly probing the valence orbitals of first-row metals as well as lighter elements during the course of photochemical transformations.

  19. Reduction of V̇O2 slow component by priming exercise: novel mechanistic insights from time-resolved near-infrared spectroscopy.

    Science.gov (United States)

    Fukuoka, Yoshiyuki; Poole, David C; Barstow, Thomas J; Kondo, Narihiko; Nishiwaki, Masato; Okushima, Dai; Koga, Shunsaku

    2015-06-01

    Novel time-resolved near-infrared spectroscopy (TR-NIRS), with adipose tissue thickness correction, was used to test the hypotheses that heavy priming exercise reduces the V̇O2 slow component (V̇O2SC) (1) by elevating microvascular [Hb] volume at multiple sites within the quadriceps femoris (2) rather than reducing the heterogeneity of muscle deoxygenation kinetics. Twelve subjects completed two 6-min bouts of heavy work rate exercise, separated by 6 min of unloaded cycling. Priming exercise induced faster overall V̇O2 kinetics consequent to a substantial reduction in the V̇O2SC (0.27 ± 0.12 vs. 0.11 ± 0.09 L·min(-1), P primed bout [total (Hb + Mb)] (197.5 ± 21.6 vs. 210.7 ± 22.5 μmol L(-1), P multiple sites within the quadriceps femoris, priming exercise reduced the baseline and slowed the increase in [deoxy (Hb + Mb)]. Changes in the intersite coefficient of variation in the time delay and time constant of [deoxy (Hb + Mb)] during the second bout were not correlated with the V̇O2SC reduction. These results support a mechanistic link between priming exercise-induced increase in muscle [Hb] volume and the reduced V̇O2SC that serves to speed overall V̇O2 kinetics. However, reduction in the heterogeneity of muscle deoxygenation kinetics does not appear to be an obligatory feature of the priming response. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

  20. Time-resolved photoelectron spectroscopy of a dinuclear Pt(II) complex: Tunneling autodetachment from both singlet and triplet excited states of a molecular dianion

    Energy Technology Data Exchange (ETDEWEB)

    Winghart, Marc-Oliver, E-mail: marc-oliver.winghart@kit.edu; Unterreiner, Andreas-Neil [Institute of Physical Chemistry, Karlsruhe Institute of Technology, P.O. Box 6980, 76049 Karlsruhe (Germany); Yang, Ji-Ping [Institute of Physical Chemistry, Karlsruhe Institute of Technology, P.O. Box 6980, 76049 Karlsruhe (Germany); School of Sciences, Hefei University of Technology, Hefei 230009 (China); Vonderach, Matthias [Centre for Proteome Research, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB (United Kingdom); Huang, Dao-Ling; Wang, Lai-Sheng [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Kruppa, Sebastian; Riehn, Christoph [Fachbereich Chemie und Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 52–54, 67663 Kaiserslautern (Germany); Kappes, Manfred M., E-mail: manfred.kappes@kit.edu [Institute of Physical Chemistry, Karlsruhe Institute of Technology, P.O. Box 6980, 76049 Karlsruhe (Germany); Institute of Nanotechnology, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe (Germany)

    2016-02-07

    Time-resolved pump-probe photoelectron spectroscopy has been used to study the relaxation dynamics of gaseous [Pt{sub 2}(μ-P{sub 2}O{sub 5}H{sub 2}){sub 4} + 2H]{sup 2−} after population of its first singlet excited state by 388 nm femtosecond laser irradiation. In contrast to the fluorescence and phosphorescence observed in condensed phase, a significant fraction of the photoexcited isolated dianions decays by electron loss to form the corresponding monoanions. Our transient photoelectron data reveal an ultrafast decay of the initially excited singlet {sup 1}A{sub 2u} state and concomitant rise in population of the triplet {sup 3}A{sub 2u} state, via sub-picosecond intersystem crossing (ISC). We find that both of the electronically excited states are metastably bound behind a repulsive Coulomb barrier and can decay via delayed autodetachment to yield electrons with characteristic kinetic energies. While excited state tunneling detachment (ESETD) from the singlet {sup 1}A{sub 2u} state takes only a few picoseconds, ESETD from the triplet {sup 3}A{sub 2u} state is much slower and proceeds on a time scale of hundreds of nanoseconds. The ISC rate in the gas phase is significantly higher than in solution, which can be rationalized in terms of changes to the energy dissipation mechanism in the absence of solvent molecules. [Pt{sub 2}(μ-P{sub 2}O{sub 5}H{sub 2}){sub 4} + 2H]{sup 2−} is the first example of a photoexcited multianion for which ESETD has been observed following ISC.

  1. Hilbert-space treatment of incoherent, time-resolved spectroscopy. II. Pathway description of optical multiple population-period transient spectroscopy.

    Science.gov (United States)

    Berg, Mark A

    2010-04-14

    This paper applies the general methods developed in the previous paper (Paper I) to the case of one-photon, dipole transitions of a molecular solute. The results generalize transient-grating spectroscopy to an arbitrarily number of dimensions. Transition and detection operators are derived, and their matrix elements are calculated in the complex-valued basis set developed in Paper I. Selection rules make it possible to analyze which incoherent pathways, and thus which correlation functions, contribute to an N-dimensional multiple population-period transient spectroscopy experiment. Irreducible-tensor methods allow the amplitudes of the contributing orientational-correlation functions to be calculated for arbitrary polarization conditions. A second-rank polarization tensor is used to describe the polarization of the pair of beams creating or detecting a grating. Several known results for one-dimensional experiments are rederived in this formalism to provide examples of its use.

  2. Broadband infrared vibrational nano-spectroscopy using thermal blackbody radiation.

    Science.gov (United States)

    O'Callahan, Brian T; Lewis, William E; Möbius, Silke; Stanley, Jared C; Muller, Eric A; Raschke, Markus B

    2015-12-14

    Infrared vibrational nano-spectroscopy based on scattering scanning near-field optical microscopy (s-SNOM) provides intrinsic chemical specificity with nanometer spatial resolution. Here we use incoherent infrared radiation from a 1400 K thermal blackbody emitter for broadband infrared (IR) nano-spectroscopy. With optimized interferometric heterodyne signal amplification we achieve few-monolayer sensitivity in phonon polariton spectroscopy and attomolar molecular vibrational spectroscopy. Near-field localization and nanoscale spatial resolution is demonstrated in imaging flakes of hexagonal boron nitride (hBN) and determination of its phonon polariton dispersion relation. The signal-to-noise ratio calculations and analysis for different samples and illumination sources provide a reference for irradiance requirements and the attainable near-field signal levels in s-SNOM in general. The use of a thermal emitter as an IR source thus opens s-SNOM for routine chemical FTIR nano-spectroscopy.

  3. Folding dynamics of the Trp-cage miniprotein: evidence for a native-like intermediate from combined time-resolved vibrational spectroscopy and molecular dynamics simulations.

    Science.gov (United States)

    Meuzelaar, Heleen; Marino, Kristen A; Huerta-Viga, Adriana; Panman, Matthijs R; Smeenk, Linde E J; Kettelarij, Albert J; van Maarseveen, Jan H; Timmerman, Peter; Bolhuis, Peter G; Woutersen, Sander

    2013-10-03

    Trp-cage is a synthetic 20-residue miniprotein which folds rapidly and spontaneously to a well-defined globular structure more typical of larger proteins. Due to its small size and fast folding, it is an ideal model system for experimental and theoretical investigations of protein folding mechanisms. However, Trp-cage's exact folding mechanism is still a matter of debate. Here we investigate Trp-cage's relaxation dynamics in the amide I' spectral region (1530-1700 cm(-1)) using time-resolved infrared spectroscopy. Residue-specific information was obtained by incorporating an isotopic label ((13)C═(18)O) into the amide carbonyl group of residue Gly11, thereby spectrally isolating an individual 310-helical residue. The folding-unfolding equilibrium is perturbed using a nanosecond temperature-jump (T-jump), and the subsequent re-equilibration is probed by observing the time-dependent vibrational response in the amide I' region. We observe bimodal relaxation kinetics with time constants of 100 ± 10 and 770 ± 40 ns at 322 K, suggesting that the folding involves an intermediate state, the character of which can be determined from the time- and frequency-resolved data. We find that the relaxation dynamics close to the melting temperature involve fast fluctuations in the polyproline II region, whereas the slower process can be attributed to conformational rearrangements due to the global (un)folding transition of the protein. Combined analysis of our T-jump data and molecular dynamics simulations indicates that the formation of a well-defined α-helix precedes the rapid formation of the hydrophobic cage structure, implying a native-like folding intermediate, that mainly differs from the folded conformation in the orientation of the C-terminal polyproline II helix relative to the N-terminal part of the backbone. We find that the main free-energy barrier is positioned between the folding intermediate and the unfolded state ensemble, and that it involves the formation of

  4. Structural differences in the two agonist binding sites of the Torpedo nicotinic acetylcholine receptor revealed by time-resolved fluorescence spectroscopy

    DEFF Research Database (Denmark)

    Martinez, K. L.; Corringer, P. J.; Edelstein, S. J.

    2000-01-01

    The nicotinic acetylcholine receptor (nAChR) from Torpedo marmorata carries two nonequivalent agonist binding sites at the αδ and αγ subunit interfaces. These sites have been characterized by time-resolved fluorescence with the partial nicotinic agonist dansyl-C6-choline (Dnscho). When bound...

  5. Single-shot spectroscopy of broadband Yb fiber laser

    Science.gov (United States)

    Suzuki, Masayuki; Yoneya, Shin; Kuroda, Hiroto

    2017-02-01

    We have experimentally reported on a real-time single-shot spectroscopy of a broadband Yb-doped fiber (YDF) laser which based on a nonlinear polarization evolution by using a time-stretched dispersive Fourier transformation technique. We have measured an 8000 consecutive single-shot spectra of mode locking and noise-like pulse (NLP), because our developed broadband YDF oscillator can individually operate the mode locking and NLP by controlling a pump LD power and angle of waveplates. A shot-to-shot spectral fluctuation was observed in NLP. For the investigation of pulse formation dynamics, we have measured the spectral evolution in an initial fluctuations of mode locked broadband YDF laser at an intracavity dispersion of 1500 and 6200 fs2 for the first time. In both case, a build-up time between cw and steady-state mode locking was estimated to be 50 us, the dynamics of spectral evolution between cw and mode locking, however, was completely different. A shot-to-shot strong spectral fluctuation, as can be seen in NLP spectra, was observed in the initial timescale of 20 us at the intracavity dispersion of 1500 fs2. These new findings would impact on understanding the birth of the broadband spectral formation in fiber laser oscillator.

  6. Extracting Time-Resolved Information from Time-Integrated Laser-Induced Breakdown Spectra

    Directory of Open Access Journals (Sweden)

    Emanuela Grifoni

    2014-01-01

    Full Text Available Laser-induced breakdown spectroscopy (LIBS data are characterized by a strong dependence on the acquisition time after the onset of the laser plasma. However, time-resolved broadband spectrometers are expensive and often not suitable for being used in portable LIBS instruments. In this paper we will show how the analysis of a series of LIBS spectra, taken at different delays after the laser pulse, allows the recovery of time-resolved spectral information. The comparison of such spectra is presented for the analysis of an aluminium alloy. The plasma parameters (electron temperature and number density are evaluated, starting from the time-integrated and time-resolved spectra, respectively. The results are compared and discussed.

  7. All electrical propagating spin wave spectroscopy with broadband wavevector capability

    Energy Technology Data Exchange (ETDEWEB)

    Ciubotaru, F., E-mail: Florin.Ciubotaru@imec.be [imec, Kapeldreef 75, B-3001 Leuven (Belgium); KU Leuven, Departement Electrotechniek (ESAT), Kasteelpark Arenberg 10, B-3001 Leuven (Belgium); Devolder, T. [Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France); Manfrini, M.; Adelmann, C.; Radu, I. P. [imec, Kapeldreef 75, B-3001 Leuven (Belgium)

    2016-07-04

    We developed an all electrical experiment to perform the broadband phase-resolved spectroscopy of propagating spin waves in micrometer sized thin magnetic stripes. The magnetostatic surface spin waves are excited and detected by scaled down to 125 nm wide inductive antennas, which award ultra broadband wavevector capability. The wavevector selection can be done by applying an excitation frequency above the ferromagnetic resonance. Wavevector demultiplexing is done at the spin wave detector thanks to the rotation of the spin wave phase upon propagation. A simple model accounts for the main features of the apparatus transfer functions. Our approach opens an avenue for the all electrical study of wavevector-dependent spin wave properties including dispersion spectra or non-reciprocal propagation.

  8. "Structure and dynamics in complex chemical systems: Gaining new insights through recent advances in time-resolved spectroscopies.” ACS Division of Physical Chemistry Symposium presented at the Fall National ACS Meeting in Boston, MA, August 2015

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Daniel [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2016-09-26

    8-Session Symposium on STRUCTURE AND DYNAMICS IN COMPLEX CHEMICAL SYSTEMS: GAINING NEW INSIGHTS THROUGH RECENT ADVANCES IN TIME-RESOLVED SPECTROSCOPIES. The intricacy of most chemical, biochemical, and material processes and their applications are underscored by the complex nature of the environments in which they occur. Substantial challenges for building a global understanding of a heterogeneous system include (1) identifying unique signatures associated with specific structural motifs within the heterogeneous distribution, and (2) resolving the significance of each of multiple time scales involved in both small- and large-scale nuclear reorganization. This symposium focuses on the progress in our understanding of dynamics in complex systems driven by recent innovations in time-resolved spectroscopies and theoretical developments. Such advancement is critical for driving discovery at the molecular level facilitating new applications. Broad areas of interest include: Structural relaxation and the impact of structure on dynamics in liquids, interfaces, biochemical systems, materials, and other heterogeneous environments.

  9. Gain-assisted broadband ring cavity enhanced spectroscopy

    Science.gov (United States)

    Selim, Mahmoud A.; Adib, George A.; Sabry, Yasser M.; Khalil, Diaa

    2017-02-01

    Incoherent broadband cavity enhanced spectroscopy can significantly increase the effective path length of light-matter interaction to detect weak absorption lines over broad spectral range, for instance to detect gases in confined environments. Broadband cavity enhancement can be based on the decay time or the intensity drop technique. Decay time measurement is based on using tunable laser source that is expensive and suffers from long scan time. Intensity dependent measurement is usually reported based on broadband source using Fabry-Perot cavity, enabling short measurement time but suffers from the alignment tolerance of the cavity and the cavity insertion loss. In this work we overcome these challenges by using an alignment-free ring cavity made of an optical fiber loop and a directional coupler, while having a gain medium pumped below the lasing threshold to improve the finesse and reduce the insertion loss. Acetylene (C2H2) gas absorption is measured around 1535 nm wavelength using a semiconductor optical amplifier (SOA) gain medium. The system is analyzed for different ring resonator forward coupling coefficient and loses, including the 3-cm long gas cell insertion loss and fiber connector losses used in the experimental verification. The experimental results are obtained for a coupler ratio of 90/10 and a fiber length of 4 m. The broadband source is the amplified spontaneous emission of another SOA and the output is measured using a 70pm-resolution optical spectrum analyzer. The absorption depth and the effective interaction length are improved about an order of magnitude compared to the direct absorption of the gas cell. The presented technique provides an engineering method to improve the finesse and, consequently the effective length, while relaxing the technological constraints on the high reflectivity mirrors and free-space cavity alignment.

  10. Photoelectron spectroscopy at a free-electron laser. Investigation of space-charge effects in angle-resolved and core-level spectroscopy and realizaton of a time-resolved core-level photoemission experiment

    Energy Technology Data Exchange (ETDEWEB)

    Marczynski-Buehlow, Martin

    2012-01-30

    The free-electron laser (FEL) in Hamburg (FLASH) is a very interesting light source with which to perform photoelectron spectroscopy (PES) experiments. Its special characteristics include highly intense photon pulses (up to 100 J/pulse), a photon energy range of 30 eV to 1500 eV, transverse coherence as well as pulse durations of some ten femtoseconds. Especially in terms of time-resolved PES (TRPES), the deeper lying core levels can be reached with photon energies up to 1500 eV with acceptable intensity now and, therefore, element-specific, time-resolved core-level PES (XPS) is feasible at FLASH. During the work of this thesis various experimental setups were constructed in order to realize angle-resolved (ARPES), core-level (XPS) as well as time-resolved PES experiments at the plane grating monochromator beamline PG2 at FLASH. Existing as well as newly developed systems for online monitoring of FEL pulse intensities and generating spatial and temporal overlap of FEL and optical laser pulses for time-resolved experiments are successfully integrated into the experimental setup for PES. In order to understand space-charge effects (SCEs) in PES and, therefore, being able to handle those effects in future experiments using highly intense and pulsed photon sources, the origin of energetic broadenings and shifts in photoelectron spectra are studied by means of a molecular dynamic N-body simulation using a modified Treecode Algorithm for sufficiently fast and accurate calculations. It turned out that the most influencing parameter is the ''linear electron density'' - the ratio of the number of photoelectrons to the diameter of the illuminated spot on the sample. Furthermore, the simulations could reproduce the observations described in the literature fairly well. Some rules of thumb for XPS and ARPES measurements could be deduced from the simulations. Experimentally, SCEs are investigated by means of ARPES as well as XPS measurements as a function of

  11. Time-Resolved Study of Nanomorphology and Nanomechanic Change of Early-Stage Mineralized Electrospun Poly(lactic acid) Fiber by Scanning Electron Microscopy, Raman Spectroscopy and Atomic Force Microscopy.

    Science.gov (United States)

    Wang, Mengmeng; Cai, Yin; Zhao, Bo; Zhu, Peizhi

    2017-08-17

    In this study, scanning electron microscopy (SEM), Raman spectroscopy and high-resolution atomic force microscopy (AFM) were used to reveal the early-stage change of nanomorphology and nanomechanical properties of poly(lactic acid) (PLA) fibers in a time-resolved manner during the mineralization process. Electrospun PLA nanofibers were soaked in simulated body fluid (SBF) for different periods of time (0, 1, 3, 5, 7 and 21 days) at 10 °C, much lower than the conventional 37 °C, to simulate the slow biomineralization process. Time-resolved Raman spectroscopy analysis can confirm that apatites were deposited on PLA nanofibers after 21 days of mineralization. However, there is no significant signal change among several Raman spectra before 21 days. SEM images can reveal the mineral deposit on PLA nanofibers during the process of mineralization. In this work, for the first time, time-resolved AFM was used to monitor early-stage nanomorphology and nanomechanical changes of PLA nanofibers. The Surface Roughness and Young's Modulus of the PLA nanofiber quantitatively increased with the time of mineralization. The electrospun PLA nanofibers with delicate porous structure could mimic the extracellular matrix (ECM) and serve as a model to study the early-stage mineralization. Tested by the mode of PLA nanofibers, we demonstrated that AFM technique could be developed as a potential diagnostic tool to monitor the early onset of pathologic mineralization of soft tissues.

  12. Magnetism and magneto-transport in the chiral helimagnet Cr1/3NbS2: Microscopic insights from angle-resolved photoemission and time-resolved optical spectroscopy

    Science.gov (United States)

    Sirica, Nicholas; Vilmercati, Paolo; Koehler, Michael; Sopkota, Deepak; Mandrus, David; Mannella, Norman; Bondino, Federica; Pis, Igor; Nappini, Silvia; Das, Pranab; Vobornik, Ivana; Fujii, Jun; Hedayat, Hamoon; Bugini, Davide; Dellera, Claudia; Carpene, Ettore; Mo, Sung-Kwan; Parker, David

    The recent discovery of the soliton lattice, and the intriguing interplay between magnetic and transport degrees of freedom, make the chiral helimagnet Cr1/3NbS2 a very promising material both for technological applications, and for elucidating the connection between non-trivial spin textures and the microscopic interactions allowed in a crystalline lattice lacking in inversion symmetry. In this talk, we present recent results of photoemission and time-resolved optical spectroscopy on Cr1/3NbS2. Most notably, the data reveal that the Fermi surface is partially composed of Cr states, and that such states may give rise to a possible half metallicity as suggested by the characteristically long demagnetization dynamic measured from time-resolved magneto-optical Kerr effect (MOKE). Finally, it will be discussed how these findings are inconsistent with a description of magnetism and magnetotransport in this material based solely on spin ordering arguments.

  13. Amine-functionalized lanthanide-doped zirconia nanoparticles: optical spectroscopy, time-resolved fluorescence resonance energy transfer biodetection, and targeted imaging.

    Science.gov (United States)

    Liu, Yongsheng; Zhou, Shanyong; Tu, Datao; Chen, Zhuo; Huang, Mingdong; Zhu, Haomiao; Ma, En; Chen, Xueyuan

    2012-09-12

    Ultrasmall inorganic oxide nanoparticles doped with trivalent lanthanide ions (Ln(3+)), a new and huge family of luminescent bioprobes, remain nearly untouched. Currently it is a challenge to synthesize biocompatible ultrasmall oxide bioprobes. Herein, we report a new inorganic oxide bioprobe based on sub-5 nm amine-functionalized tetragonal ZrO(2)-Ln(3+) nanoparticles synthesized via a facile solvothermal method and ligand exchange. By utilizing the long-lived luminescence of Ln(3+), we demonstrate its application as a sensitive time-resolved fluorescence resonance energy transfer (FRET) bioprobe to detect avidin with a record-low detection limit of 3.0 nM. The oxide nanoparticles also exhibit specific recognition of cancer cells overexpressed with urokinase plasminogen activator receptor (uPAR, an important marker of tumor biology and metastasis) and thus may have great potentials in targeted bioimaging.

  14. Time-resolved spark-source mass spectroscopy: the effect of spark duration on relative sensitivity factors, ion intensity and precision of analysis

    Energy Technology Data Exchange (ETDEWEB)

    Franklin, James Curry [Univ. of Tennessee, Knoxville, TN (United States)

    1971-01-29

    A radio-frequency, high-voltage spark ion source in conjunction with a double-focusing mass spectrometer has been used to measure the relative sensitivity factors for several elements in matrices of tin, iron, beryllium oxide, uranium, and steels. The sensitivity factors were examined for concentration and matrix effects. No significant variations were found for the concentration ranges studied, but there were very large sensitivity variations with changes in the matrix type. In order to accomplish this study, circuits were designed and installed to synchronize the ion-beam chopping circuits with the radio-frequency spark pulses so that time-resolved spectra were obtained at different periods in the spark pulse.

  15. Acetylene weak bands at 2.5 μm from intracavity Cr:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy.

    Science.gov (United States)

    Girard, Véronique; Farrenq, Robert; Sorokin, Evgeni; Sorokina, Irina T; Guelachvili, Guy; Picqué, Nathalie

    2006-02-26

    The spectral dynamics of a mid-infrared multimode Cr(2+):ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C(2)H(2) in natural isotopic abundance are recorded around 4000 cm(-1) with kilometric absorption path lengths and sensitivities better than 3 10(-8) cm(-1). Two cold bands are newly identified and assigned to the ν(1)+ν(4) (1) and ν(3)+ν(5) (1) transitions of (12)C(13)CH(2). The ν(1)+ν(5) (1) band of (12)C(2)HD and fourteen (12)C(2)H(2) bands are observed, among which for the first time ν(2)+2ν(4) (2)+ν(5) (-1).

  16. Acetylene weak bands at 2.5 μm from intracavity Cr2+:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy

    Science.gov (United States)

    Girard, Véronique; Farrenq, Robert; Sorokin, Evgeni; Sorokina, Irina T.; Guelachvili, Guy; Picqué, Nathalie

    2010-01-01

    The spectral dynamics of a mid-infrared multimode Cr2+:ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C2H2 in natural isotopic abundance are recorded around 4000 cm−1 with kilometric absorption path lengths and sensitivities better than 3 10−8 cm−1. Two cold bands are newly identified and assigned to the ν1+ν41 and ν3+ν51 transitions of 12C13CH2. The ν1+ν51 band of 12C2HD and fourteen 12C2H2 bands are observed, among which for the first time ν2+2ν42+ν5−1. PMID:21151826

  17. Type I photosensitized reactions of oxopurines. Kinetics and thermodynamics of the reaction with triplet benzophenone by time-resolved photoacoustic spectroscopy

    Science.gov (United States)

    Murgida, Daniel H.; Erra Balsells, Rosa; Crippa, Pier Raimondo; Viappiani, Cristiano

    1998-09-01

    Benzophenone photosensitized reactions of caffeine, theophylline and theobromine were investigated in acetonitrile by time-resolved laser-induced photoacoustics. In the three cases global quenching rate constants of triplet benzophenone were measured as a function of temperature and it was observed that this is a non-activated process. Besides, for theobromine and theophylline heats for NH hydrogen abstraction reactions were determined. In agreement with semiempirical calculation predictions, hydrogen abstraction is thermodynamically more favorable and faster for theophylline (Δ H=-265 kJ mol -1, kr=9.6×10 8 M -1 s -1) than for theobromine (Δ H=-168 kJ mol -1, kr=3.7×10 8 M -1 s -1).

  18. Characterization of Large Water Clusters by Broadband Rotational Spectroscopy

    Science.gov (United States)

    Perez, Cristobal; Zaleski, Daniel P.; Seifert, Nathan A.; Pate, Brooks H.; Kisiel, Zbigniew; Temelso, Berhane; Shields, George C.; Shipman, Steven T.; Finnerman, Ian

    2013-06-01

    Most theoretical water models match with experimental result reasonably well up to n=10. For clusters larger than the decamer there is no clear consensus in the global minimum geometries, as the low-energy landscape for a given cluster size changes considerably depending on the model applied. However, there is agreement in considering the undecamer regime as one of the richer pure water cluster regimes, with a large number (>50) of isomers within 1 kcal/mol of the global minimum. Using broadband chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy operating in the 2-8 GHz frequency range, seven low-energy isomers of the water undecamer have been identified in a pulsed molecular beam. The observed water cluster structures have been identified as belonging to four families on basis to their rotational constants according to their different oxygen atom frameworks. These families can be explained by building up the structures from smaller water cluster subunits. Rotational spectra consistent with theoretical predictions for two isomers of (H_{2}O)_{13} and one of (H_{2}O)_{15} have also been identified. Due to the high density of lines observed in the broadband spectrum, the traditional method of pattern recognition using ab-initio calculations was replaced with a new approach combining high-level ab-initio calculations with automatic fitting tools. These autofitting routines were tested on these systems and are also briefly described.

  19. Femtosecond time-resolved absorption spectroscopy of main-form and high-salt peridinin-chlorophyll a-proteins at low temperatures.

    Science.gov (United States)

    Ilagan, Robielyn P; Koscielecki, Jeremy F; Hiller, Roger G; Sharples, Frank P; Gibson, George N; Birge, Robert R; Frank, Harry A

    2006-11-28

    Steady-state and femtosecond time-resolved optical methods have been used to compare the spectroscopic features and energy transfer dynamics of two systematically different light-harvesting complexes from the dinoflagellate Amphidinium carterae: main-form (MFPCP) and high-salt (HSPCP) peridinin-chlorophyll a-proteins. Pigment analysis and X-ray diffraction structure determinations [Hofmann, E., Wrench, P. M., Sharples, F. P., Hiller, R. G., Welte, W., Diederichs, K. (1996) Science 272, 1788-1791; T. Schulte, F. P. Sharples, R. G. Hiller, and E. Hofmann, unpublished results] have revealed the composition and geometric arrangements of the protein-bound chromophores. The MFPCP contains eight peridinins and two chlorophyll (Chl) a, whereas the HSPCP has six peridinins and two Chl a, but both have very similar pigment orientations. Analysis of the absorption spectra has shown that the peridinins and Chls absorb at different wavelengths in the two complexes. Also, in the HSPCP complex, the Qy transitions of the Chls are split into two well-resolved bands. Quantum computations by modified neglect of differential overlap with partial single and double configuration interaction (MNDO-PSDCI) methods have revealed that charged amino acid residues within 8 A of the pigment molecules are responsible for the observed spectral shifts. Femtosecond time-resolved optical spectroscopic kinetic data from both complexes show ultrafast (<130 fs) and slower (approximately 2 ps) pathways for energy transfer from the peridinin excited singlet states to Chl. The Chl-to-Chl energy transfer rate constant for both complexes was measured and is discussed in terms of the Förster mechanism. It was found that, upon direct Chl excitation, the Chl-to-Chl energy transfer rate constant for MFPCP was a factor of 4.2 larger than for HSPCP. It is suggested that this difference arises from a combination of factors including distance between Chls, spectral overlap, and the presence of two additional

  20. Time-resolved spectral characterization of ring cavity surface emitting and ridge-type distributed feedback quantum cascade lasers by step-scan FT-IR spectroscopy.

    Science.gov (United States)

    Brandstetter, Markus; Genner, Andreas; Schwarzer, Clemens; Mujagic, Elvis; Strasser, Gottfried; Lendl, Bernhard

    2014-02-10

    We present the time-resolved comparison of pulsed 2nd order ring cavity surface emitting (RCSE) quantum cascade lasers (QCLs) and pulsed 1st order ridge-type distributed feedback (DFB) QCLs using a step-scan Fourier transform infrared (FT-IR) spectrometer. Laser devices were part of QCL arrays and fabricated from the same laser material. Required grating periods were adjusted to account for the grating order. The step-scan technique provided a spectral resolution of 0.1 cm(-1) and a time resolution of 2 ns. As a result, it was possible to gain information about the tuning behavior and potential mode-hops of the investigated lasers. Different cavity-lengths were compared, including 0.9 mm and 3.2 mm long ridge-type and 0.97 mm (circumference) ring-type cavities. RCSE QCLs were found to have improved emission properties in terms of line-stability, tuning rate and maximum emission time compared to ridge-type lasers.

  1. Analysis of the optical properties of Er{sup 3+}-doped strontium barium niobate nanocrystals using time-resolved laser spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kowalska, D.; Haro-Gonzalez, P. [Universidad de La Laguna, Departamento de Fisica Fundamental, Experimental, Electronica y Sistemas, La Laguna, Tenerife (Spain); Martin, I.R. [Universidad de La Laguna, Departamento de Fisica Fundamental, Experimental, Electronica y Sistemas, La Laguna, Tenerife (Spain); Malta Consolider Team, La Laguna, Tenerife (Spain); Caceres, J.M. [Universidad de La Laguna, Departamento de Edafologia y Geologia, La Laguna, Tenerife (Spain)

    2010-06-15

    This paper reports the results obtained in strontium barium niobate (SBN) nanocrystals in glasses doped with 1, 2.5 and 5 mol% of Er{sup 3+} ions. The melt-quenching method was applied to fabricate the glasses with composition SrO-BaO-Nb{sub 2}O{sub 5}-B{sub 2}O{sub 3} and further thermal treatment was used to obtain glass ceramic samples from the glass precursor. X-ray diffraction patterns confirmed the formation of SBN nanocrystals with an average size of about 50 nm in diameter. Time-resolved fluorescence spectra for the emission of Er{sup 3+} ions at 1550 nm have been analyzed in order to confirm the incorporation of the Er{sup 3+} ions into the nanocrystals. Green frequency upconversion emission under excitation at 975 nm coming from the ions in the nanocrystals has been obtained. This intense upconversion is about a factor of 500 higher than that obtained from the ions which reside in the glassy phase. Moreover, temporal evolution studies have been carried out with the purpose of determining the involved upconversion mechanism and the importance of these processes as a source of losses for the optical amplification at 1550 nm. (orig.)

  2. Time-resolved UV-IR pump-stimulated emission pump spectroscopy to probe collisional relaxation of $8p\\,^2P_{3/2}$ Cs I

    CERN Document Server

    Salahuddin, Mohammed; McFarland, Jacob; Bayram, S Burcin

    2015-01-01

    We describe and use a time-resolved pump-stimulated emission pump spectroscopic technique to measure collisional relaxation in a high-lying energy level of atomic cesium. Aligned $8p\\,^2P_{3/2}$ cesium atoms were produced by a pump laser. A second laser, the stimulated emission pump, promoted the population exclusively to the $5d\\,^2D_{5/2}$ level. The intensity of the $5d\\,^2D_{5/2}\\rightarrow6s\\,^2S_{1/2}$ cascade fluorescence at 852.12 nm was monitored. The linear polarization dependence of the $6s\\,^2S_{1/2}\\rightarrow8p\\,^2P_{3/2}\\rightarrow5d\\,^2S_{5/2}$ transition was measured in the presence of argon gas at various pressures. From the measurement, we obtained the disalignment cross section value for the $8p\\,^2P_{3/2}$ level due to collisions with ground-level argon atoms.

  3. Impulse-induced compression rheo-optics study of polymers using attenuated total reflection based step-scan Fourier transform infrared time-resolved spectroscopy.

    Science.gov (United States)

    Nishikawa, Yuji; Nakano, Tatsuhiko; Noda, Isao

    2008-09-01

    An impulse-induced attenuated total reflection (ATR) based dynamic compression step-scan time-resolved Fourier transform rheo-optical system has been developed. This system was used to observe different viscoelastic properties of poly(ethylene terephthalate) (PET), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx), and carbon-black-filled polyester-polyamide blend. In the case of PET, almost no viscoelastic response extending beyond 15 ms was observed in the dynamic absorbance difference time domain spectrum. In contrast, PHBHx showed apparently different viscoelastic responses in the dynamic absorbance difference spectrum, especially in the C=O stretching band region. A long relaxation tail of the 1723 cm(-1) band lasting about 2.7 milliseconds was clearly seen. The tail corresponds to the structural or morphological reorganization of a less ordered crystalline form (Type II) under compressive perturbation. The carbon-black-filled polyester-polyamide blend film also shows different viscoelastic response tails. In this case, the amide C=O stretching vibration band does not show distinct viscoelastic responses, suggesting that the polyamide component does not contribute much to the viscoelastic properties. The present method shows promise for characterizing a wide variety of viscoelastic materials, including polymer alloys, blends, composites, copolymers, and semicrystalline polymers.

  4. A study of relaxation mechanisms in the A{sup 2}{Sigma}{sup +} state of nitric oxide by time resolved double resonant polarization spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stampanoni-Panariello, A.; Bombach, R.; Hemmerling, B.; Hubschmid, W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Double resonant polarization labeling spectroscopy is applied to detect nitric oxide in flames and to characterize rotational energy transfer and orientation changing collisions in its first excited electronic state. (author) 4 figs., 3 refs.

  5. Time resolved infrared spectroscopy of femtosecond proton dynamics in the liquid phase; Spectroscopie infrarouge resolue en temps pour l'etude de la dynamique femtoseconde du proton en phase liquide

    Energy Technology Data Exchange (ETDEWEB)

    Amir, W

    2003-12-15

    This work of thesis aims to understand the strong mobility of protons in water. Water is fundamental to life and mediates many chemical and biological processes. However this liquid is poorly understood at the molecular level. The richness of interdisciplinary sciences allows us to study the properties which make it so unique. The technique used for this study was the femtosecond time resolved vibrational spectroscopy. Several experiments were carried out to characterize the femtosecond proton dynamics in water. The visualization of the rotation of water molecules obtained by anisotropy measurements will be presented. This experiment is carried out in isotopic water HDO/D{sub 2}O for reasons of experimental and theoretical suitability. However this is not water. Pure water H{sub 2}O was also studied without thermal effects across vibrations modes. An intermolecular energy resonant transfer was observed. Finally the localized structure of the proton in water (called Eigen form) was clearly experimentally observed. This molecule is implicated in the abnormal mobility of the proton in water (Grotthuss mechanism). (author)

  6. Scanning, non-contact, hybrid broadband diffuse optical spectroscopy and diffuse correlation spectroscopy system.

    Science.gov (United States)

    Johansson, Johannes D; Mireles, Miguel; Morales-Dalmau, Jordi; Farzam, Parisa; Martínez-Lozano, Mar; Casanovas, Oriol; Durduran, Turgut

    2016-02-01

    A scanning system for small animal imaging using non-contact, hybrid broadband diffuse optical spectroscopy (ncDOS) and diffuse correlation spectroscopy (ncDCS) is presented. The ncDOS uses a two-dimensional spectrophotometer retrieving broadband (610-900 nm) spectral information from up to fifty-seven source-detector distances between 2 and 5 mm. The ncDCS data is simultaneously acquired from four source-detector pairs. The sample is scanned in two dimensions while tracking variations in height. The system has been validated with liquid phantoms, demonstrated in vivo on a human fingertip during an arm cuff occlusion and on a group of mice with xenoimplanted renal cell carcinoma.

  7. Soft X-ray Laser Microscopy of Lipid Rafts towards GPCR-Based Drug Discovery Using Time-Resolved FRET Spectroscopy

    Directory of Open Access Journals (Sweden)

    Tatsuhiko Kodama

    2011-03-01

    Full Text Available Many signaling molecules involved in G protein-mediated signal transduction, which are present in the lipid rafts and believed to be controlled spatially and temporally, influence the potency and efficacy of neurotransmitter receptors and transporters. This has focus interest on lipid rafts and the notion that these microdomains acts as a kind of signaling platform and thus have an important role in the expression of membrane receptor-mediated signal transduction, cancer, immune responses, neurotransmission, viral infections and various other phenomena due to specific and efficient signaling according to extracellular stimuli. However, the real structure of lipid rafts has not been observed so far due to its small size and a lack of sufficiently sophisticated observation systems. A soft X-ray microscope using a coherent soft X-ray laser in the water window region (2.3–4.4 nm should prove to be a most powerful tool to observe the dynamic structure of lipid rafts of several tens of nanometers in size in living cells. We have developed for the X-ray microscope a new compact soft X-ray laser using strongly induced plasma high harmonic resonance. We have also developed a time-resolved highly sensitive fluorescence resonance energy transfer (FRET system and confirmed protein-protein interactions coupled with ligands. The simultaneous use of these new tools for observation of localization of G-protein coupled receptors (GPCRs in rafts has become an important and optimum tool system to analyze the dynamics of signal transduction through rafts as signaling platform. New technology to visualize rafts is expected to lead to the understanding of those dynamics and innovative development of drug discovery that targets GPCRs localized in lipid rafts.

  8. Direct Observation of the Kinetically Relevant Site of CO Hydrogenation on Supported Ru Catalyst at 700 K by Time-Resolved FT-IR Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Frei, Heinz; Wasylenko, Walter; Frei, Heinz

    2008-06-04

    Time-resolved FT-IR spectra of carbon monoxide hydrogenation over alumina-supported ruthenium particles were recorded on themillisecond time scale at 700 K using pulsed release of CO and a continuous flow of H2/N2 (ratio 0.067 or 0.15, 1 atm total pressure). Adsorbed carbon monoxide was detected along with gas phase products methane (3016 and 1306 cm-1), water (1900 +- 1300 cm-1), and carbon dioxide (2348 cm-1). Aside from adsorbed CO, no other surface species were observed. The rate of formation of methane is 2.5 +- 0.4 s-1 and coincides with the rate of carbon dioxide growth (3.4 +- 0.6 s-1), thus indicating that CH4 and CO2 originate from a common intermediate. The broad band of adsorbed carbon monoxide has a maximum at 2010 cm-1 at early times (36 ms) that shifts gradually to 1960 cm-1 over a period of 3 s as a result of the decreasing surface concentration of CO. Kinetic analysis of the adsorbed carbon monoxide reveals that surface sites absorbing at the high frequency end of the infrared band are temporally linked to gas phase product growth. Specifically, a (linear) CO site at 2026 cm-1 decays with a rate constant of 2.9 +- 0.1 s-1, which coincides with the rise constant of CH4. This demonstrates that the linear CO site at 2026 cm-1 is the kinetically most relevant one for the rate-determining CO dissociation step under reaction conditions at 700 K.

  9. Time-resolved terahertz spectroscopy reveals the influence of charged sensitizing quantum dots on the electron dynamics in ZnO

    Czech Academy of Sciences Publication Activity Database

    Bamini, S.N.; Němec, Hynek; Žídek, Karel; Abdellah, M.; Al-Marri, M.J.; Chábera, P.; Ponseca, C.; Zheng, K.; Pullerits, T.

    2017-01-01

    Roč. 19, č. 8 (2017), s. 6006-6012 ISSN 1463-9076 R&D Projects: GA ČR GA17-03662S Institutional support: RVO:68378271 ; RVO:61389021 Keywords : sensitized semiconductors * ultrafast dynamics * terahertz spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.123, year: 2016

  10. Time-resolved quantitative phosphoproteomics

    DEFF Research Database (Denmark)

    Verano-Braga, Thiago; Schwämmle, Veit; Sylvester, Marc

    2012-01-01

    proteins involved in the Ang-(1-7) signaling, we performed a mass spectrometry-based time-resolved quantitative phosphoproteome study of human aortic endothelial cells (HAEC) treated with Ang-(1-7). We identified 1288 unique phosphosites on 699 different proteins with 99% certainty of correct peptide...

  11. Folding of a Zinc-Finger ββα-Motif Investigated Using Two-Dimensional and Time-Resolved Vibrational Spectroscopy.

    Science.gov (United States)

    Meuzelaar, Heleen; Panman, Matthijs R; van Dijk, Chris N; Woutersen, Sander

    2016-11-03

    Small proteins provide good model systems for studying the fundamental forces that control protein folding. Here, we investigate the folding dynamics of the 28-residue zinc-finger mutant FSD-1, which is designed to form a metal-independent folded ββα-motif, and which provides a testing ground for proteins containing a mixed α/β fold. Although the folding of FSD-1 has been actively studied, the folding mechanism remains largely unclear. In particular, it is unclear in what stage of folding the α-helix is formed. To address this issue we investigate the folding mechanism of FSD-1 using a combination of temperature-dependent UV circular dichroism (UV-CD), Fourier transform infrared (FTIR) spectroscopy, two-dimensional infrared (2D-IR) spectroscopy, and temperature-jump (T-jump) transient-IR spectroscopy. Our UV-CD and FTIR data show different thermal melting transitions, indicating multistate folding behavior. Temperature-dependent 2D-IR spectra indicate that the α-helix is the most stable structural element of FSD-1. To investigate the folding/unfolding re-equilibration dynamics of FSD-1, the conformational changes induced by a nanosecond T-jump are probed with transient-IR and transient dispersed-pump-probe (DPP) IR spectroscopy. We observe biexponential T-jump relaxation kinetics (with time constants of 80 ± 13 ns and 1300 ± 100 ns at 322 K), confirming that the folding involves an intermediate state. The IR and dispersed-pump-probe IR spectra associated with the two kinetic components suggest that the folding of FSD-1 involves early formation of the α-helix, followed by the formation of the β-hairpin and hydrophobic contacts.

  12. Time resolved fluorescence of naproxen in organogel medium

    Science.gov (United States)

    Burguete, M. Isabel; Izquierdo, M. Angeles; Galindo, Francisco; Luis, Santiago V.

    2008-07-01

    The interaction between non-steroidal anti-inflammatory drug naproxen and the self assembled fibrillar network created by a low molecular weight organogelator has been probed by means of time resolved fluorescence spectroscopy.

  13. Possible observation of parametrically amplified coherent phasons in K0.3MoO3 using time-resolved extreme-ultraviolet angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Liu, H. Y.; Gierz, I.; Petersen, J. C.; Kaiser, S.; Simoncig, A.; Cavalieri, A. L.; Cacho, C.; Turcu, I. C. E.; Springate, E.; Frassetto, F.; Poletto, L.; Dhesi, S. S.; Xu, Z.-A.; Cuk, T.; Merlin, R.; Cavalleri, A.

    2013-07-01

    We use time- and angle-resolved photoemission spectroscopy in the extreme ultraviolet to measure the time- and momentum-dependent electronic structures of photoexcited K0.3MoO3. Prompt depletion of the charge-density wave condensate launches coherent oscillations of the amplitude mode, observed as a 1.7-THz-frequency modulation of the bonding band position. In contrast, the antibonding band oscillates at about half this frequency. We attribute these oscillations to coherent excitation of phasons via parametric amplification of phase fluctuations.

  14. Combined time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure spectroscopy study on the complexation of trivalent actinides with chloride at T = 25-200 °C.

    Science.gov (United States)

    Skerencak-Frech, Andrej; Fröhlich, Daniel R; Rothe, Jörg; Dardenne, Kathy; Panak, Petra J

    2014-01-21

    The complexation of trivalent actinides (An(III)) with chloride is studied in the temperature range from 25 to 200 °C by spectroscopic methods. Time-resolved laser fluorescence spectroscopy (TRLFS) is applied to determine the thermodynamic data of Cm(III)-Cl(-) complexes, while extended X-ray absorption fine structure spectroscopy (EXAFS) is used to determine the structural data of the respective Am(III) complexes. The experiments are performed in a custom-built high-temperature cell which is modified for the respective spectroscopic technique. The TRLFS results show that at 25 °C the speciation is dominated mainly by the Cm(3+) aquo ion. Only a minor fraction of the CmCl(2+) complex is present in solution. As the temperature increases, the fraction of this species decreases further. Simultaneously, the fraction of the CmCl2(+) complex increases strongly with the temperature. Also, the CmCl3 complex is formed to a minor extent at T > 160 °C. The conditional stability constant log β'2 is determined as a function of the temperature and extrapolated to zero ionic strength with the specific ion interaction theory approach. The log β°2(T) values increase by more than 3 orders of magnitude in the studied temperature range. The temperature dependency of log β°2 is fitted by the extended van't Hoff equation to determine ΔrH°m, ΔrS°m, and ΔrC°p,m. The EXAFS results support these findings. The results confirm the absence of americium(III) chloride complexes at T = 25 and 90 °C ([Am(III)] = 10(-3) m, [Cl(-)] = 3.0 m), and the spectra are described by 9-10 oxygen atoms at a distance of 2.44-2.48 Å. At T = 200 °C two chloride ligands are present in the inner coordination sphere of Am(III) at a distance of 2.78 Å.

  15. Application of time-of-flight near-infrared spectroscopy to fruits: analysis of absorption and scattering conditions of near-infrared radiation using cross-correlation of the time-resolved profile.

    Science.gov (United States)

    Kurata, Yohei; Tsuchikawa, Satoru

    2009-03-01

    The absorption and scattering conditions of near-infrared radiation in a grapefruit, a popular thick-peeled fruit, were investigated by time-of-flight near-infrared spectroscopy (TOF-NIRS). The cross-correlation function was introduced to obtain fine spectroscopic information from the time-resolved profile. Variation of the optical parameters in both the time-resolved profile and the cross-correlation function showed that the NIR radiation was largely absorbed in the peel and considerably scattered in the flesh of the fruit. It also reflected the straightness of the input pulsed laser. The substantial optical path length of the grapefruit estimated from the cross-correlation function was approximately 4 to 5 times as long as the nominal optical path length (NOPL). The cross-correlation function was an effective tool to analyze the absorption/scattering conditions of NIR radiation in a sample where an unstable light source such as a Nd:YAG laser with high output energy was employed.

  16. Optimal multisine excitation design for broadband electrical impedance spectroscopy

    Science.gov (United States)

    Sanchez, B.; Vandersteen, G.; Bragos, R.; Schoukens, J.

    2011-11-01

    Electrical impedance spectroscopy (EIS) can be used to characterize biological materials in applications ranging from cell culture to body composition, including tissue and organ state. The emergence of cell therapy and tissue engineering opens up a new and promising field of application. While in most cases classical measurement techniques based on a frequency sweep can be used, EIS based on broadband excitations enables dynamic biological systems to be characterized when the measuring time and injected energy are a constraint. Myocardial regeneration, cell characterization in micro-fluidic systems and dynamic electrical impedance tomography are all examples of such applications. The weakness of such types of fast EIS measuring techniques resides in their intrinsic loss of accuracy. However, since most of the practical applications have no restriction over the excitation used, the input power spectrum can be appropriately designed to maximize the accuracy obtained from the measurements. This paper deals with the problem of designing the optimal multisine excitation for electrical bioimpedance measurements. The optimal multisine is obtained by the minimization of the Cramer-Rao lower bound, or what is the same, by maximizing the accuracy obtained from the measurements. Furthermore, because no analytical solution exists for global optimization involving time and frequency domains jointly, this paper presents the multisine optimization approach partially in both domains and then combines the results. As regards the frequency domain approach, a novel contribution is made for the multisine amplitude power spectrum. In the time domain, multisine is optimized by reducing its crest factor. Moreover, the impact on the information and accuracy of the impedance spectrum obtained from using different multisine amplitude power spectra is discussed, as well as the number of frequencies and frequency distributions. The theory is supported by a set of validation measurements when

  17. Changing Hydrogen-Bond Structure during an Aqueous Liquid-Liquid Transition Investigated with Time-Resolved and Two-Dimensional Vibrational Spectroscopy.

    Science.gov (United States)

    Bruijn, Jeroen R; van der Loop, Tibert H; Woutersen, Sander

    2016-03-03

    We investigate the putative liquid-liquid phase transition in aqueous glycerol solution, using the OD-stretch mode in dilute OD/OH isotopic mixtures to probe the hydrogen-bond structure. The conversion exhibits Avrami kinetics with an exponent of n = 2.9 ± 0.1 (as opposed to n = 1.7 observed upon inducing ice nucleation and growth in the same sample), which indicates a transition from one liquid phase to another. Two-dimensional infrared (2D-IR) spectroscopy shows that the initial and final phases have different hydrogen-bond structures: the former has a single Gaussian distribution of hydrogen-bond lengths, whereas the latter has a bimodal distribution consisting of a broad distribution and a narrower, ice-like distribution. The 2D-IR spectrum of the final phase is identical to that of ice/glycerol at the same temperature. Combined with the kinetic data this suggests that the liquid-liquid transformation is immediately followed by a rapid formation of small (probably nanometer-sized) ice crystals.

  18. Time-Resolved Quantitative Measurement of OH HO2 and CH2O in Fuel Oxidation Reactions by High Resolution IR Absorption Spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Haifeng; Rotavera, Brandon; Taatjes, Craig A.

    2014-08-01

    Combined with a Herriott-type multi-pass slow flow reactor, high-resolution differential direct absorption spectroscopy has been used to probe, in situ and quantitatively, hydroxyl (OH), hydroperoxy (HO 2 ) and formaldehyde (CH 2 O) molecules in fuel oxidation reactions in the reactor, with a time resolution of about 1 micro-second. While OH and CH 2 O are probed in the mid-infrared (MIR) region near 2870nm and 3574nm respectively, HO 2 can be probed in both regions: near-infrared (NIR) at 1509nm and MIR at 2870nm. Typical sensitivities are on the order of 10 10 - 10 11 molecule cm -3 for OH at 2870nm, 10 11 molecule cm -3 for HO 2 at 1509nm, and 10 11 molecule cm -3 for CH 2 O at 3574nm. Measurements of multiple important intermediates (OH and HO 2 ) and product (CH 2 O) facilitate to understand and further validate chemical mechanisms of fuel oxidation chemistry.

  19. Multimode Surface Functional Group Determination: Combining Steady-State and Time-Resolved Fluorescence with X-ray Photoelectron Spectroscopy and Absorption Measurements for Absolute Quantification.

    Science.gov (United States)

    Fischer, Tobias; Dietrich, Paul M; Unger, Wolfgang E S; Rurack, Knut

    2016-01-19

    The quantitative determination of surface functional groups is approached in a straightforward laboratory-based method with high reliability. The application of a multimode BODIPY-type fluorescence, photometry, and X-ray photoelectron spectroscopy (XPS) label allows estimation of the labeling ratio, i.e., the ratio of functional groups carrying a label after reaction, from the elemental ratios of nitrogen and fluorine. The amount of label on the surface is quantified with UV/vis spectrophotometry based on the molar absorption coefficient as molecular property. The investigated surfaces with varying density are prepared by codeposition of 3-(aminopropyl)triethoxysilane (APTES) and cyanoethyltriethoxysilane (CETES) from vapor. These surfaces show high functional group densities that result in significant fluorescence quenching of surface-bound labels. Since alternative quantification of the label on the surface is available through XPS and photometry, a novel method to quantitatively account for fluorescence quenching based on fluorescence lifetime (τ) measurements is shown. Due to the complex distribution of τ on high-density surfaces, the stretched exponential (or Kohlrausch) function is required to determine representative mean lifetimes. The approach is extended to a commercial Rhodamine B isothiocyanate (RITC) label, clearly revealing the problems that arise from such charged labels used in conjunction with silane surfaces.

  20. Proton transfer and protein conformation dynamics in photosensitive proteins by time-resolved step-scan Fourier-transform infrared spectroscopy.

    Science.gov (United States)

    Lórenz-Fonfría, Víctor A; Heberle, Joachim

    2014-06-27

    Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards understanding its mechanism. Protonation and conformational changes affect the vibration pattern of amino acid side chains and of the peptide bond, respectively, both of which can be probed by infrared (IR) difference spectroscopy. For proteins whose function can be repetitively and reproducibly triggered by light, it is possible to obtain infrared difference spectra with (sub)microsecond resolution over a broad spectral range using the step-scan Fourier transform infrared technique. With -10(2)-10(3) repetitions of the photoreaction, the minimum number to complete a scan at reasonable spectral resolution and bandwidth, the noise level in the absorption difference spectra can be as low as -10(-) (4), sufficient to follow the kinetics of protonation changes from a single amino acid. Lower noise levels can be accomplished by more data averaging and/or mathematical processing. The amount of protein required for optimal results is between 5-100 µg, depending on the sampling technique used. Regarding additional requirements, the protein needs to be first concentrated in a low ionic strength buffer and then dried to form a film. The protein film is hydrated prior to the experiment, either with little droplets of water or under controlled atmospheric humidity. The attained hydration level (g of water / g of protein) is gauged from an IR absorption spectrum. To showcase the technique, we studied the photocycle of the light-driven proton-pump bacteriorhodopsin in its native purple membrane environment, and of the light-gated ion channel channelrhodopsin-2 solubilized in detergent.

  1. Probing of the local environment and calculation of J.O. parameters for Eu{sup 3+} CMPO functionalized pillararene complexes by time resolved fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, Arijit, E-mail: arijita@barc.gov.in [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Fang, Yuyu; Yuan, Xiangyang; Yuan, Lihua [Key Laboratory for Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, College of Chemistry, Sichuan University, Chengdu 610064 (China)

    2015-10-15

    An attempt was made to understand the complexation of Eu{sup 3+} with structurally modified CMPO-functionalized pillararenes by luminescence spectroscopy. Formation of single species with different numbers of inner sphere water molecules was found to be present for all the complexes. On increasing spacer length between ligating moieties and supramolecular pillararenes, the stereo-chemical crowding around ligating oxygen decreased. Therefore, strong covalent metal–oxygen bond was formed which was reflected in the increasing trend of the computed Ω{sub 2} values (Judd–Offelt parameter): LI (4.66×10{sup −20})LII (3.19 ms)>LIII (2.94 ms) while the branching ratio values for all three complexes followed the same trend as β{sub 2}>β{sub 4}>β{sub 1}. The other photo-physical constants like asymmetric factor, quantum efficiency, magnetic and electric dipole transition probabilities were also computed. - Highlights: • Probing of the local environment of Eu{sup 3+} complex with three structurally modified CMPO functionalized pillararenes. • J.O. parameter Ω{sub 2} followed the trend: LI (4.66E−20)

  2. Characterization of Microsolvated Crown Ethers from Broadband Rotational Spectroscopy

    Science.gov (United States)

    Perez, Cristobal; Schnell, Melanie; Blanco, Susana; Lopez, Juan Carlos

    2016-06-01

    Since they were first synthetized, crown ethers have been extensively used in organometallic chemistry due to their unparalleled binding selectivity with alkali metal cations. From a structural point of view, crown ethers are heterocycles containing oxygen and/or other heteroatoms, although the most common ones are formed from ethylene oxide unit. Crown ethers are conventionally seen as being hydrophilic inside and hydrophobic outside when the structures found for the metal cation complexes are considered. However, crown ethers are extremely flexible and in isolation may present a variety of stable conformations so that their structure may be easily adapted in presence of a strong ligand as an alkali metal cation minimize the energy of the resulting complex. Water can be considered a soft ligand which interacts with crown ethers through moderate hydrogen bonds. It is thus interesting to investigate which conformers are selected by water to form complexes, the preferred interaction sites and the possible conformational changes due to the presence of one or more water molecules. Previous studies identified microsolvated crown ethers but in all cases with a chromophore group attached to the structure. Here we present a broadband rotational spectroscopy study of microsolvated crown ethers produced in a pulsed molecular jet expansion. Several 1:1 and 1:2 crown ether:water aggregates are presented for 12-crown-4, 15-crown-5 and 18-crown-6. Unambiguous identification of the structures has been achieved using isotopic substitution within the water unit. The subtle changes induced in the structures of the crown ether monomer upon complexation and the hydrogen-bonding network that hold them together will be also discussed. F. Gámez, B. Martínez-Haya, S. Blanco,J. C. López and J. L. Alonso, Phys. Chem. Chem. Phys. 2014, 14 12912-12918 V. A. Shubert, C.W. Müller and T. Zwier, J. Phys. Chem. A 2009, 113 8067-8079

  3. Probing the Aggregation Behavior of Neat Imidazolium-Based Alkyl Sulfate (Alkyl = Ethyl, Butyl, Hexyl, and Octyl) Ionic Liquids through Time Resolved Florescence Anisotropy and NMR and Fluorescence Correlation Spectroscopy Study.

    Science.gov (United States)

    Majhi, Debashis; Pabbathi, Ashok; Sarkar, Moloy

    2016-01-14

    Aggregation behavior of a series of neat 1-ethyl 3-methylimidazolium alkyl sulfate (alkyl = ethyl, butyl, hexyl, and octyl) ionic liquids has been investigated through combined time-resolved fluorescence spectroscopy, 1-D and 2-D NMR spectroscopy, and fluorescence correlation spectroscopy (FCS). Interestingly, experimentally measured rotational relaxation times (τr) for ethyl, butyl, hexyl and octyl systems are measured to be 2.25, 1.64, 1.36, and 1.32 times higher than the estimated (from Stokes-Einstein-Debye theory) values for the same respective systems. This indicates that the emitting species is not the monomeric imidazolium moiety rather an associated species, and volume of the rotating fluorescing species decreases even though the length of the alkyl moiety on the anions is increased. The shift in the (1)H proton signal as well as a change in the width of the same signal upon dilution of the neat ionic liquids indicates that ionic liquids exist in the aggregated form. Further investigation through the 2D-ROESY experiment shows that interaction between imidazolium and sulfate is relatively stronger in the ethyl system than that of the longer octyl system. FCS measurements independently show that the hydrodynamic volume decreases with an increase in the anion chain length. The NMR and FCS results are consistent with the findings of the fluorescence anisotropy study.

  4. Time Resolved Spectroscopy of Cepheid Variable Stars

    Science.gov (United States)

    Hartman, Katherine; Beaton, Rachael L.; SDSS-IV APOGEE-2 Team

    2018-01-01

    Galactic Cepheid variable stars have been used for over a century as standard candles and as the first rung of the cosmic distance ladder, integral to the calculation of the Hubble constant. However, it is challenging to observe Cepheids within the Milky Way Galaxy because of extinction, and there are still uncertainties in the Cepheid period-luminosity relation (or Leavitt Law) that affect these important distance calculations. The Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey has provided spectra for a large sample of Galactic Cepheids, but the standard chemical abundance pipeline (ASPCAP) processing is not well-suited to pulsational variables, preventing us from using them to study metallicity effect in the Leavitt Law with standard processing. Using a standalone version of the ASPCAP pipeline, we present an analysis of individual visit spectra from a test sample of nine APOGEE Cepheids, and we compare its output to the stars’ literature abundance values. Based on the results of this comparison, we will be able to improve the standard analysis and process the entirety of APOGEE’s Cepheid catalogue to improve its abundance measurements. The resulting abundance data will allow us to constrain the effect of metallicity on the Leavitt Law and thus allow for more accurate Cepheid distance measurements for the determination of the Hubble constant.

  5. Ultrafast broadband Fourier-transform CARS spectroscopy operating at 50,000 spectra/second

    Science.gov (United States)

    Tamamitsu, Miu; Sakaki, Yusuke; Nakamura, Tasuku; Podagatlapalli, G. Krishna; Ideguchi, Takuro; Goda, Keisuke

    2017-02-01

    We present a coherent Raman scattering (CRS) spectroscopy technique achieving a CRS spectral acquisition rate of 50,000 spectra/second over a Raman spectral region of 200 - 1430 cm-1 with a resolution of 4.2 cm-1. This ultrafast, broadband and high-resolution CRS spectroscopic performance is realized by a polygonal Fourier-domain delay line serving as an ultra-rapid optical-path-length scanner in a broadband Fourier-transform coherent anti-Stokes Raman scattering (CARS) spectroscopy platform. We present a theoretical description of the technique and demonstrate continuous, ultrafast, broadband, and high-resolution CARS spectroscopy on a liquid toluene sample using our proof-of-concept setup.

  6. Time-Resolved Laser Fluorescence Spectroscopy Study of the Coordination Chemistry of a Hydrophilic CHON [1,2,3-Triazol-4-yl]pyridine Ligand with Cm(III) and Eu(III).

    Science.gov (United States)

    Wagner, Christoph; Mossini, Eros; Macerata, Elena; Mariani, Mario; Arduini, Arturo; Casnati, Alessandro; Geist, Andreas; Panak, Petra J

    2017-02-20

    The complexation of Cm(III) and Eu(III) with the novel i-SANEX complexing agent 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PTD) was studied by time-resolved laser fluorescence spectroscopy (TRLFS). The formation of 1:3, 1:2, and 1:1 metal/ligand complexes was identified upon increasing PTD concentration in 10(-3) mol/L HClO4 and in 0.44 mol/L HNO3 solutions. For all these complexes, stability constants were determined at different acid concentrations. Though under the extraction conditions proposed for an An/Ln separation process, that is, for 0.08 mol/L PTD in 0.44 mol/L HNO3, 1:3 complexes represent the major species, a significant fraction of 1:2 complexes was found. This is caused by ligand protonation, and results in lower Eu(III)/Am(III) separation factors compared to SO3-Ph-BTP, until now considered the i-SANEX reference ligand. Focused extraction studies performed at lower proton concentration, where the 1:3 complex is formed exclusively, confirm this assumption.

  7. Uptake Of Trivalent Actinides (Cm(III)) And Lanthanides (Eu(III)) By Cement-Type Minerals: A Wet Chemistry And Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) Study

    Energy Technology Data Exchange (ETDEWEB)

    Tits, J.; Stumpf, T; Wieland, E.; Fanghaenel, T

    2003-03-01

    The interaction of the two chemical homologues Cm (III) and Eu(III) with calcium silicate hydrates at pH 13.3 has been investigated in batch-type sorption studies using Eu(III), and complemented with time-resolved laser fluorescence spectroscopy using Cm(III). The sorption data for Eu(III) reveal fast sorption kinetics, and a strong uptake by CSH phases, with distribution ratios of 6({+-}3)*105 L kg-1. Three different types of sorbed Cm(III) species have been identified: a non-fluorescing species, which was identified as Cm cluster present either as surface precipitate or as Cm(III) colloid in solution, and two sorbed fluorescing species. The sorbed fluorescing species have characteristic emission spectra (main peak maxima at 618.9 nm and 620.9 nm) and fluorescence emission lifetimes (289 {+-} 11 ms and 1482{+-} 200 ms). From the fluorescence lifetimes, it appears that the two fluorescing Cm(III) species have, respectively, one to two or no water molecules left in their first coordination sphere, suggesting that these species are incorporated into the CSH structure. A structural model for Cm(III) and Eu(III) incorporation into CSH phases is proposed based on the substitution of Ca at two different types of sites in the CSH structure. (author)

  8. The Time-resolved and Extreme-conditions XAS (TEXAS) facility at the European Synchrotron Radiation Facility: the energy-dispersive X-ray absorption spectroscopy beamline ID24

    Science.gov (United States)

    Pascarelli, S.; Mathon, O.; Mairs, T.; Kantor, I.; Agostini, G.; Strohm, C.; Pasternak, S.; Perrin, F.; Berruyer, G.; Chappelet, P.; Clavel, C.; Dominguez, M. C.

    2016-01-01

    The European Synchrotron Radiation Facility has recently made available to the user community a facility totally dedicated to Time-resolved and Extreme-conditions X-ray Absorption Spectroscopy – TEXAS. Based on an upgrade of the former energy-dispersive XAS beamline ID24, it provides a unique experimental tool combining unprecedented brilliance (up to 1014 photons s−1 on a 4 µm × 4 µm FWHM spot) and detection speed for a full EXAFS spectrum (100 ps per spectrum). The science mission includes studies of processes down to the nanosecond timescale, and investigations of matter at extreme pressure (500 GPa), temperature (10000 K) and magnetic field (30 T). The core activities of the beamline are centered on new experiments dedicated to the investigation of extreme states of matter that can be maintained only for very short periods of time. Here the infrastructure, optical scheme, detection systems and sample environments used to enable the mission-critical performance are described, and examples of first results on the investigation of the electronic and local structure in melts at pressure and temperature conditions relevant to the Earth’s interior and in laser-shocked matter are given. PMID:26698085

  9. Changes of evoked cerebral blood oxygenation and optical pathlength in the frontal lobe during language tasks: a study by multi-channel, time-resolved near-infrared spectroscopy and functional MRI.

    Science.gov (United States)

    Murata, Yoshihiro; Sakatani, Kaoru; Hoshino, Tatsuya; Fujiwara, Norio; Katayama, Yoichi; Yamashita, Daisuke; Yamanaka, Takeshi; Oda, Motoki; Yamashita, Yutaka

    2010-01-01

    To determine the alterations in optical characteristics and cerebral blood oxygenation (CBO) in the frontal lobe during language tasks, we evaluated the changes in mean optical pathlength (MOP) and CBO induced by a verbal fluency task (VFT) in the right and left frontal lobes in normal adults (n = 9, mean age = 29.6 +/- 4.8 years). We employed a newly developed 8-channel time-resolved near-infrared spectroscopy (TRS) instrument. The results demonstrated differences in MOP in the fronto-temporal areas with subject and wavelength; however, there was no significant difference between the right and left sides (p > 0.05). Also, the VFT did not affect the MOP significantly as compared to that before the tasks (p > 0.05). In all of the recording regions, the VFT caused increases in concentration of oxyhemoglobin and total hemoglobin associated with a decrease in deoxyhemoglobin concentration, indicating that these cortical areas were activated by the VFT. However, the mean concentration changes of oxyhemoglobin and total hemoglobin on the left side were larger than those on the right side. In addition, functional MRI demonstrated that the inferior frontal gyrus on the left side was activated in the subjects who exhibited increases in oxyhemoglobin concentration in these areas. These results suggest that TRS may be useful to study language function and to assess hemispheric dominance for language.

  10. The Time-resolved and Extreme-conditions XAS (TEXAS) facility at the European Synchrotron Radiation Facility: the energy-dispersive X-ray absorption spectroscopy beamline ID24.

    Science.gov (United States)

    Pascarelli, S; Mathon, O; Mairs, T; Kantor, I; Agostini, G; Strohm, C; Pasternak, S; Perrin, F; Berruyer, G; Chappelet, P; Clavel, C; Dominguez, M C

    2016-01-01

    The European Synchrotron Radiation Facility has recently made available to the user community a facility totally dedicated to Time-resolved and Extreme-conditions X-ray Absorption Spectroscopy--TEXAS. Based on an upgrade of the former energy-dispersive XAS beamline ID24, it provides a unique experimental tool combining unprecedented brilliance (up to 10(14) photons s(-1) on a 4 µm × 4 µm FWHM spot) and detection speed for a full EXAFS spectrum (100 ps per spectrum). The science mission includes studies of processes down to the nanosecond timescale, and investigations of matter at extreme pressure (500 GPa), temperature (10000 K) and magnetic field (30 T). The core activities of the beamline are centered on new experiments dedicated to the investigation of extreme states of matter that can be maintained only for very short periods of time. Here the infrastructure, optical scheme, detection systems and sample environments used to enable the mission-critical performance are described, and examples of first results on the investigation of the electronic and local structure in melts at pressure and temperature conditions relevant to the Earth's interior and in laser-shocked matter are given.

  11. Ultra-Broadband Dielectric THz Spectroscopy with Air-Biased-Coherent-Detection

    DEFF Research Database (Denmark)

    D'Angelo, Francesco; Bonn, Mischa; Turchinovich, Dmitry

    2013-01-01

    We present results on ultra-broadband THz-TDS on silicon using air biased coherent detection (ABCD) technique. We find that the positioning of the sample in the spectrometer, leading to the spatial shift of THz focus, is crucial for accurate spectroscopy results....

  12. Monitoring Network and Interfacial Healing Processes by Broadband Dielectric Spectroscopy: : A Case Study on Natural Rubber

    NARCIS (Netherlands)

    Hernandez Santana, M.; Grande, A.M.; van der Zwaag, S.; Garcia Espallargas, Santiago J.

    2016-01-01

    Broadband dielectric spectroscopy (BDS) is introduced as a new and powerful technique to monitor network and macroscale damage healing in an elastomer. For the proof of concept, a partially cured sulfur-cured natural rubber (NR) containing reversible disulfides as the healing moiety was employed.

  13. Completely background free broadband coherent anti-Stokes Raman scattering spectroscopy

    DEFF Research Database (Denmark)

    Liu, Xing; Niu, Hanben; Liu, Wei

    2013-01-01

    For the first time it was proposed a numerical approach to obtain non-NRB time-frequency coherent anti-Stokes Raman scattering (CARS) spectrograms. In order to evaluate the validity of the CARS spectrogram for background free broadband CARS spectroscopy, the authors numerically constructed a CARS...

  14. Synthesis and characterization of Ag doped ZnS quantum dots for enhanced photocatalysis of Strychnine asa poison: Charge transfer behavior study by electrochemical impedance and time-resolved photoluminescence spectroscopy.

    Science.gov (United States)

    Gupta, Vinod Kumar; Fakhri, Ali; Azad, Mona; Agarwal, Shilpi

    2018-01-15

    In this study, the photocatalytic degradation of Strychnine was investigated by ZnS quantum dots and doped with silver in UV systems. ZnS and Ag-ZnS quantum dots were synthesized by chemical method and characterized by powder X-ray diffraction, transmission electron microscopy, UV-vis spectra and photoluminescence. The charge transfer process on the semicon-ductor/electrolyte interface was investigated via electrochemical impedance spectroscopy (EIS) and time-resolved photoluminescence. The average diameters of ZnS and Ag doped ZnS QDs were 3.0-5.0nm and 3.0-5.3nm, respectively. The band gap of ZnS and Ag-ZnS QDs was computed as 3.47 and 3.1eV, respectively. The surface area values of ZnS and Ag-ZnS QDs have been found as 78.25 and 89.54m2/g, respectively. The influences of key operating parameters such as initial pH, catalyst dosage, UV radiation intensity, reaction time as well as the effect of initial Strychnine concentration on mineralization extents were studied. The results of the study showed that the maximum removal efficiency of Strychnine had been achieved by un-doped and Ag-doped ZnS QDs at radiation intensity of 100W/m2, at time of 60min, pH of 3 and initial Strychnine concentration of 20mg/ml. Also the observations clearly showed that the photocatalysis process with Ag doped ZnS QDs are more effective than un-doped ZnS QDs. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Determination of high-molecular weight polycyclic aromatic hydrocarbons in high performance liquid chromatography fractions of coal tar standard reference material 1597a via solid-phase nanoextraction and laser-excited time-resolved Shpol'skii spectroscopy.

    Science.gov (United States)

    Wilson, Walter B; Alfarhani, Bassam; Moore, Anthony F T; Bisson, Cristina; Wise, Stephen A; Campiglia, Andres D

    2016-02-01

    This article presents an alternative approach for the analysis of high molecular weight - polycyclic aromatic hydrocarbons (HMW-PAHs) with molecular mass 302 Da in complex environmental samples. This is not a trivial task due to the large number of molecular mass 302 Da isomers with very similar chromatographic elution times and similar, possibly even virtually identical, mass fragmentation patterns. The method presented here is based on 4.2K laser-excited time-resolved Shpol'skii spectroscopy, a high resolution spectroscopic technique with the appropriate selectivity for the unambiguous determination of PAHs with the same molecular mass. The potential of this approach is demonstrated here with the analysis of a coal tar standard reference material (SRM) 1597a. Liquid chromatography fractions were submitted to the spectroscopic analysis of five targeted isomers, namely dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene, naphtho[2,3-a]pyrene and dibenzo[a,h]pyrene. Prior to analyte determination, the liquid chromatographic fractions were pre-concentrated with gold nanoparticles. Complete analysis was possible with microliters of chromatographic fractions and organic solvents. The limits of detection varied from 0.05 (dibenzo[a,l]pyrene) to 0.24 µg L(-1) (dibenzo[a,e]pyrene). The excellent analytical figures of merit associated to its non-destructive nature, which provides ample opportunity for further analysis with other instrumental methods, makes this approach an attractive alternative for the determination of PAH isomers in complex environmental samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Ultraviolet photochemical reaction of [Fe(III(C2O43]3− in aqueous solutions studied by femtosecond time-resolved X-ray absorption spectroscopy using an X-ray free electron laser

    Directory of Open Access Journals (Sweden)

    Y. Ogi

    2015-05-01

    Full Text Available Time-resolved X-ray absorption spectroscopy was performed for aqueous ammonium iron(III oxalate trihydrate solutions using an X-ray free electron laser and a synchronized ultraviolet laser. The spectral and time resolutions of the experiment were 1.3 eV and 200 fs, respectively. A femtosecond 268 nm pulse was employed to excite [Fe(III(C2O43]3− in solution from the high-spin ground electronic state to ligand-to-metal charge transfer state(s, and the subsequent dynamics were studied by observing the time-evolution of the X-ray absorption spectrum near the Fe K-edge. Upon 268 nm photoexcitation, the Fe K-edge underwent a red-shift by more than 4 eV within 140 fs; however, the magnitude of the redshift subsequently diminished within 3 ps. The Fe K-edge of the photoproduct remained lower in energy than that of [Fe(III(C2O43]3−. The observed red-shift of the Fe K-edge and the spectral feature of the product indicate that Fe(III is upon excitation immediately photoreduced to Fe(II, followed by ligand dissociation from Fe(II. Based on a comparison of the X-ray absorption spectra with density functional theory calculations, we propose that the dissociation proceeds in two steps, forming first [(CO2•Fe(II(C2O42]3− and subsequently [Fe(II(C2O42]2−.

  17. Broadband mid-IR subharmonic OPOs for molecular spectroscopy

    Science.gov (United States)

    Leindecker, Nick; Marandi, Alireza; Vodopyanov, Konstantin L.; Byer, Robert L.

    2012-02-01

    We generate broadband mid-infrared frequency combs via degenerate optical parametric oscillation in a subharmonic OPO. This technique efficiently transfers the desirable properties of shorter wavelength mode-locked sources to the mid- IR. Our OPO resonator is a 3m or 4m ring cavity composed of one pair of concave mirrors with R=50mm and four flat mirrors, all but one of which are gold coated with > 99% reflection. A single dielectric mirror is used to introduce the pump (2.05 micron from IMRA America, 75 MHz, 80 fs, 600mW or 1.55 micron from Menlo Systems C-fiber, 100 MHz, 70 fs, 350 mW or 1.56 micron from Toptica Photonics FemtoFiber Pro, 80 MHz, 85 fs, 380 mW). The dielectric mirror is transmissive for the pump and reflective in a 2.5- 4 micron or 3- 6 micron (for 2 micron pump) range. Broadband parametric gain around the 3.1-micron subharmonic is provided by short (0.2-0.5mm) periodically poled lithium niobate (MgO:PPLN) at Brewster angle. Crystals were cut from Crystal Technology Inc. material having QPM period of 34.8 microns for type 0 (e=e+e) phase matching at t=32 deg. C. With the 2-micron pump, orientation patterned gallium arsenide from BAE systems is used as the non-linear material In both systems, the enormous acceptance bandwidth at degeneracy, typical for OPOs with type 0 (or type I) phase-matching, gives broad bandwidth and makes temperature tuning insignificant. Broadband oscillation is achieved when signal/idler are brought into degenerate resonance by fine-tuning the cavity length with a mirror on a piezo stage. Using an 8% reflective pellicle, we outcouple a frequency comb of more than 1000nm bandwidth, centered around 3.1 microns from the Er/PPLN system. A 1mm or 2.5mm thick ZnSe plate at Brewster angle provides 2nd-order group velocity dispersion compensation, improving the OPO bandwidth. The OPO threshold was measured to be < 30mW. When locked, the OPO outputs 60 mW of average power centered at 3.1 microns. With the Tm/OP-GaAs system we

  18. Commissioning of a UV/time-resolved-FTIR beamline at the Duke FEL laboratory

    CERN Document Server

    Hutson, M S; Chang, M S; Gillikin, A; Litvinenko, V N; Edwards, G

    2002-01-01

    We describe the commissioning of a novel two-color beamline at the Duke Free Electron Laser Laboratory, designed to perform time-resolved FTIR spectroscopy in a pump-probe scheme with sub-nanosecond resolution to measure dynamical processes with durations as long as 10 ns. The UV pump pulses are produced by the tunable (193-700 nm) output of the OK-4 Storage-Ring FEL. The broadband, infrared probe pulses are generated as synchrotron radiation in a bending magnet downstream of the OK-4 wiggler. The repetition rate of the light source (2.79 MHz) is ideal for operating the interferometer in the rapid-scan, asynchronous sampling mode. An investigation of DNA photolyase is proposed.

  19. Electronic nose to detect volatile compound profile and quality changes in 'spring Belle' peach (Prunus persica L.) during cold storage in relation to fruit optical properties measured by time-resolved reflectance spectroscopy.

    Science.gov (United States)

    Rizzolo, Anna; Bianchi, Giulia; Vanoli, Maristella; Lurie, Susan; Spinelli, Lorenzo; Torricelli, Alessandro

    2013-02-27

    The aim of this research was to study the relationships between electronic nose (E-nose) pattern, maturity class of peaches assessed at harvest by means of absorption coefficient at 670 nm (μ(a)670) measured in fruit pulp by time-resolved reflectance spectroscopy (TRS), and quality evolution during a 4 week cold storage. 'Spring Belle' peaches were measured for μ(a)670 by TRS, ranked according to decreasing μ(a)670 value, divided into three TRS maturity classes (less (LeM), medium (MeM), and more (MoM) mature), and randomized into 9 samples of 30 fruit each, so that fruits from the whole μ(a)670 range were present in each sample. At harvest and after 1, 2, 3, and 4 weeks of storage at 0 and 4 °C, fruits of each sample were evaluated for firmness, expressible juice, μ(a)670, and ethylene production. LeM and MoM peaches of each sample were analyzed for aroma pattern by a commercial electronic nose and by static HS-GC and for sugar (glucose, fructose, sucrose, and sorbitol) and organic acid (quinic, malic, and citric acids) compositions by HPLC. Principal component analysis (PCA) of electronic nose data emphasized the ability of the E-nose to assess the ripening stage of fruit associated with maturity class, storage time, and storage temperature. The sensors having the highest influence on the pattern were W5S in PC-1, W1S in PC-2, and W2S in PC-3. From linear correlation analysis between PCs and firmness, flavor, and volatile compounds, it was found that PC-1 was related to ethylene production and volatile compounds (mainly acetate esters and ethanol); the highest PC-1 scores were found for fruit belonging to the MoM class after 2 weeks of storage at 4 °C, which showed the rise in ethylene production coupled with the highest total volatile production and sugar and acid composition of ripe peach fruits. PC-2 correlated with hexanal, ethyl acetate, and sugar composition, and PC-3 was mainly related to flavor compounds; both functions significantly changed with

  20. Ultra-broadband THz time-domain spectroscopy of energetic materials

    DEFF Research Database (Denmark)

    Kaltenecker, Korbinian J.; Zhou, Binbin; Engelbrecht, Sebastian

    2017-01-01

    Ultra-broadband THz spectroscopy based on photomixing in air plasma allows to exploit an extended frequency range, up to 20 THz and beyond. In this work, we investigate the potential of this technique for chemical recognition of illicit substances like explosives and compare the experimental spec...... spectra with ab-inition DFT simulation results to get deeper insight to the physical nature of the observed spectral features....

  1. Ultrafast relaxation dynamics of nitric oxide synthase studied by visible broadband transient absorption spectroscopy

    Science.gov (United States)

    Hung, Chih-Chang; Yabushita, Atsushi; Kobayashi, Takayoshi; Chen, Pei-Feng; Liang, Keng S.

    2017-09-01

    Ultrafast dynamics of endothelial nitric oxide synthase (eNOS) oxygenase domain was studied by transient absorption spectroscopy pumping at Soret band. The broadband visible probe spectrum has visualized the relaxation dynamics from the Soret band to Q-band and charge transfer (CT) band. Supported by two-dimensional correlation spectroscopy, global fitting analysis has successfully concluded the relaxation dynamics from the Soret band to be (1) electronic transition to Q-band (0.16 ps), (2) ligand dissociation and CT (0.94 ps), (3) relaxation of the CT state (4.0 ps), and (4) ligand rebinding (59 ps).

  2. Study of the interaction of trivalent actinide and lanthanide ions with human serum transferrin by means of time-resolved laser-fluorescence spectroscopy; Untersuchung der Wechselwirkung trivalenter Actinid- und Lanthanidionen mit humanem Serumtransferrin mittels zeitaufgeloester Laserfluoreszenzspektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Nicole

    2015-04-27

    In the present work the complexation of Cm(III), Eu(III) and Am(III) with human serum transferrin is studied. The aim of this work was the identification and the spectroscopic and thermodynamic characterization of An(III) and Ln(III) transferrin complex species. Different speciation methods, such as time-resolved laser fluorescence spectroscopy (TRLFS), luminescence spectroscopy and EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy were applied. Using TRLFS two unambiguously different Cm(III) transferrin species were identified for the first time. In the pH range from 3.5 to 9.7 the Cm(III) transferrin species I is formed revealing complexation of the metal ion at a nonspecific site of the protein surface. In case of the Cm(III) transferrin species II Cm(III) is bound at the Fe(III) binding site of the protein resulting in a 4-fold coordination via amino acid groups of the protein (His, Asp, 2 x Tyr) and coordination of two water molecules and three additional ligands, e.g. OH{sup -} or CO{sub 3}{sup 2-}. Due to the kinetic and thermodynamic differences of the binding sites of the N- and C-lobe, the experimental conditions ensure exclusive coordination of Cm(III) at the C-terminal binding site. In addition to the complexation studies of Cm(III) with transferrin, the interaction with the recombinant N-lobe of human serum transferrin (hTf/2N) as a model component for the transferrin N-lobe was investigated. At pH≥7.4 a Cm(III) hTf/2N species with Cm(III) bound at the Fe(III) binding site is formed which is comparable to the Cm(III) transferrin species II. An increase of the temperature from room temperature (T=296 K) to physiological temperature (T=310 K) favors the complexation of Cm(III) with both transferrin and hTf/2N. The complexation of Cm(III) with transferrin was investigated at three different carbonate concentrations (c(carbonate){sub tot}=0 mM, 0,23 mM und 25 mM (physiological carbonate concentration)). An increase of the total carbonate

  3. Compact, high-repetition-rate source for broadband sum-frequency generation spectroscopy

    Science.gov (United States)

    Heiner, Zsuzsanna; Petrov, Valentin; Mero, Mark

    2017-06-01

    We present a high-efficiency optical parametric source for broadband vibrational sum-frequency generation (BB-VSFG) for the chemically important mid-infrared spectral range at 2800-3600 cm-1 to study hydrogen bonding interactions affecting the structural organization of biomolecules at water interfaces. The source consists of a supercontinuum-seeded, dual-beam optical parametric amplifier with two broadband infrared output beams and a chirped sum-frequency mixing stage providing narrowband visible pulses with adjustable bandwidth. Utilizing a pulse energy of only 60 μJ from a turn-key, 1.03-μm pump laser operating at a repetition rate of 100 kHz, the source delivers 6-cycle infrared pulses at 1.5 and 3.2 μm with pulse energies of 4.6 and 1.8 μJ, respectively, and narrowband pulses at 0.515 μm with a pulse energy of 5.0 μJ. The 3.2-μm pulses are passively carrier envelope phase stabilized with fluctuations at the 180-mrad level over a 10-s time period. The 1.5-μm beamline can be exploited to deliver pump pulses for time-resolved studies after suitable frequency up-conversion. The high efficiency, stability, and two orders of magnitude higher repetition rate of the source compared to typically employed systems offer great potential for providing a boost in sensitivity in BB-VSFG experiments at a reduced cost.

  4. Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics

    DEFF Research Database (Denmark)

    D’Angelo, Francesco; Mics, Zoltán; Bonn, Mischa

    2014-01-01

    index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6......Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time......-domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive...

  5. Rapid, broadband spectroscopic temperature measurement of CO2 using VIPA spectroscopy

    CERN Document Server

    Klose, Andrew; Cruz, Flavio C; Maser, Daniel L; Diddams, Scott A

    2016-01-01

    Time-resolved spectroscopic temperature measurements of a sealed carbon dioxide sample cell were realized with an optical frequency comb combined with a two-dimensional dispersive spectrometer. A supercontinuum laser source based on an erbium fiber mode-locked laser was employed to generate coherent light around 2000 nm (5000 cm-1). The laser was passed through a 12-cm long cell containing CO2, and the transmitted light was analyzed in a virtually imaged phased array- (VIPA-) based spectrometer. Broadband spectra spanning more than 100 cm-1 with a spectral resolution of roughly 0.075 cm-1 (2.2 GHz) were acquired with an integration period of 2 ms. The temperature of the CO2 sample was deduced from fitting a modeled spectrum to the line intensities of the experimentally acquired spectrum. Temperature dynamics on the time scale of milliseconds were observed with a temperature resolution of 2.6 K. The spectroscopically-deduced temperatures agreed with temperatures of the sample cell measured with a thermistor. P...

  6. Broadband x-ray imaging and spectroscopy of the crab nebula and pulsar with NuSTAR

    DEFF Research Database (Denmark)

    Madsen, Kristin K.; Reynolds, Stephen; Harrison, Fiona

    2015-01-01

    We present broadband (3-78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power law in this energy band, spatially resolved spectroscopy of the nebula finds a break at ~9 ke...

  7. A broadband x-ray imaging spectroscopy with high-angular resolution: the FORCE mission

    Science.gov (United States)

    Mori, Koji; Tsuru, Takeshi Go; Nakazawa, Kazuhiro; Ueda, Yoshihiro; Okajima, Takashi; Murakami, Hiroshi; Awaki, Hisamitsu; Matsumoto, Hironori; Fukazawa, Yasushi; Tsunemi, Hiroshi; Takahashi, Tadayuki; Zhang, William W.

    2016-07-01

    We are proposing FORCE (Focusing On Relativistic universe and Cosmic Evolution) as a future Japan-lead Xray observatory to be launched in the mid 2020s. Hitomi (ASTRO-H) possesses a suite of sensitive instruments enabling the highest energy-resolution spectroscopy in soft X-ray band, a broadband X-ray imaging spectroscopy in soft and hard X-ray bands, and further high energy coverage up to soft gamma-ray band. FORCE is the direct successor to the broadband X-ray imaging spectroscopy aspect of Hitomi (ASTRO-H) with significantly higher angular resolution. The current design of FORCE defines energy band pass of 1-80 keV with angular resolution of black holes" in various mass-scales: "buried supermassive black holes (SMBHs)" (> 104 M⊙) residing in the center of galaxies in a cosmological distance, "intermediate-mass black holes" (102-104 M⊙) acting as the possible seeds from which SMBHs grow, and "orphan stellar-mass black holes" (< 102 M⊙) without companion in our Galaxy. In addition to these missing BHs, hunting for the nature of relativistic particles at various astrophysical shocks is also in our scope, utilizing the broadband X-ray coverage with high angular-resolution. FORCE are going to open a new era in these fields. The satellite is proposed to be launched with the Epsilon vehicle that is a Japanese current solid-fuel rocket. FORCE carries three identical pairs of Super-mirror and wide-band X-ray detector. The focal length is currently planned to be 10 m. The silicon mirror with multi-layer coating is our primary choice to achieve lightweight, good angular optics. The detector is a descendant of hard X-ray imager onboard Hitomi (ASTRO-H) replacing its silicon strip detector with SOI-CMOS silicon pixel detector, allowing an extension of the low energy threshold down to 1 keV or even less.

  8. Accurate optical parameter extraction procedure for broadband near-infrared spectroscopy of brain matter

    Science.gov (United States)

    Sultan, Ebraheem; Najafizadeh, Laleh; Gandjbakhche, Amir H.; Pourrezaei, Kambiz; Daryoush, Afshin

    2013-01-01

    Modeling behavior of broadband (30 to 1000 MHz) frequency modulated near-infrared (NIR) photons through a phantom is the basis for accurate extraction of optical absorption and scattering parameters of biological turbid media. Photon dynamics in a phantom are predicted using both analytical and numerical simulation and are related to the measured insertion loss (IL) and insertion phase (IP) for a given geometry based on phantom optical parameters. Accuracy of the extracted optical parameters using finite element method (FEM) simulation is compared to baseline analytical calculations from the diffusion equation (DE) for homogenous brain phantoms. NIR spectroscopy is performed using custom-designed, broadband, free-space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 680, 780, and 820 nm. Differential detection between two optical Rx locations separated by 0.3 cm is employed to eliminate systemic artifacts associated with interfaces of the optical Tx and Rx with the phantoms. Optical parameter extraction is achieved for four solid phantom samples using the least-square-error method in MATLAB (for DE) and COMSOL (for FEM) simulation by fitting data to measured results over broadband and narrowband frequency modulation. Confidence in numerical modeling of the photonic behavior using FEM has been established here by comparing the transmission mode's experimental results with the predictions made by DE and FEM for known commercial solid brain phantoms.

  9. Broadband Microwave Spectroscopy as a Tool to Study Intermolecular Interactions in the Diphenyl Ether - Water System

    Science.gov (United States)

    Fatima, Mariyam; Perez, Cristobal; Schnell, Melanie

    2017-06-01

    Many biological processes, such as chemical recognition and protein folding, are mainly controlled by the interplay of hydrogen bonds and dispersive forces. This interplay also occurs between organic molecules and solvent water molecules. Broadband rotational spectroscopy studies of weakly bound complexes are able to accurately reveal the structures and internal dynamics of molecular clusters isolated in the gas phase. Amongst them, water clusters with organic molecules are of particular interest. In this work, we investigate the interplay between different types of weak intermolecular interactions and how it controls the preferred interaction sites of aromatic ethers, where dispersive interactions may play a significant role. We present our results on diphenyl ether (C_{12}H_{10}O, 1,1'-Oxydibenzene) complexed with up to three molecules of water. Diphenyl ether is a flexible molecule, and it offers two competing binding sites for water: the ether oxygen and the aromatic π system. In order to determine the structure of the diphenyl ether-water complexes, we targeted transitions in the 2-8 GHz range using broadband rotational spectroscopy. We identify two isomers with one water, one with two water, and one with three water molecules. Further analysis from isotopic substitution measurements provided accurate structural information. The preferred interactions, as well as the observed structural changes induced upon complexation, will be presented and discussed.

  10. Interest in broadband dielectric spectroscopy to study the electronic transport in materials for lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Badot, Jean-Claude, E-mail: jc.badot@chimie-paristech.fr [Institut de Recherche de Chimie Paris, UMR CNRS 8247, Réseau sur le Stockage Electrochimique de l' Energie (RS2E), Chimie Paris Tech, PSL*, 11 rue P. et M. Curie, 75231 Cedex 05 Paris (France); Lestriez, Bernard [Institut des Matériaux Jean Rouxel, UMR CNRS 6502, Université de Nantes, 2 rue de la Houssinière, BP32229, 44322 Nantes (France); Dubrunfaut, Olivier [GeePs | Group of electrical engineering – Paris, UMR CNRS 8507, CentraleSupélec, Univ. Paris-Sud, Université Paris-Saclay, Sorbonne Universités, UPMC Univ Paris 06, 3 & 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette CEDEX, Paris (France)

    2016-11-15

    Highlights: • Broadband dielectric spectroscopy measures the multiscale electronic conductivity from macroscopic to interatomic sizes. • There is an influence of the surface states on the electronic transfer of powdered materials (e.g. thin insulating layer of Li{sub 2}CO{sub 3} on LiNiO{sub 2} and carbon coating on LiFePO{sub 4}). • Electrical relaxations resulting from the interfacial polarizations at the different scales of the carbon black network are evidenced. - Abstract: Broadband dielectric spectroscopy (BDS) is used to measure complex permittivity and conductivity of conducting materials for lithium batteries at frequencies from a few Hz to several GHz with network and impedance analysers. Under the influence of an electric field, there will be charge density fluctuations in the conductor mainly due to electronic transfer. These fluctuations result in dielectric relaxations for frequencies below 100 GHz. The materials are compacted powders in which each element (particles, agglomerates of particles) can have different sizes and morphologies. In the present review, studies are reported on the influence of surface states in LiNiO{sub 2} (ageing and degradation in air) and LiFePO{sub 4} (carbon coating thin layer), and on a composite electrode based on the lithium trivanadate (Li{sub 1.1}V{sub 3}O{sub 8}) active material. The results have shown that the BDS technique is very sensitive to the different scales of materials architectures involved in electronic transport, from interatomic distances to macroscopic sizes.

  11. Broadband spectroscopy of magnetic response in a nano-scale magnetic wire

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, A., E-mail: yamaguti@lasti.u-hyogo.ac.jp [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Koto, Kamigori, Ako, Hyogo 678-1205 (Japan); Motoi, K.; Miyajima, H. [Department of Physics, Keio University, Hiyoshi, Yokohama, Kanagawa 223-8522 (Japan); Utsumi, Y. [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Koto, Kamigori, Ako, Hyogo 678-1205 (Japan)

    2014-09-01

    We measure the broadband spectra of magnetic response in a single layered ferromagnetic nano-scale wire in order to investigate the size effect on the ferromagnetic resonance. We found that the resonance frequency difference between 300-nm- and 5-μm-wide wires was varied by about 5 GHz due to the shape anisotropy. Furthermore, we experimentally detected the magnetization precession induced by the thermal fluctuation via the rectification of a radio-frequency (rf) current by incorporating an additional direct current (dc) by using Wheatstone bridge circuit. Our investigation renders that the shape anisotropy is of great importance to control the resonance frequency and to provide thermal stability of the microwave devices. - Highlights: • We describe an experimental investigation of the magnetic response of a single layered ferromagnetic nano-scale wire. • We present the conventional broadband microwave spectroscopy with a vector network analyzer and rectifying spectroscopy obtained with a Wheatstone bridge technique. • The investigation enables us to characterize the size effect on the ferromagnetic response and also to detect the magnetization precession induced by the thermal fluctuations.

  12. Time-resolved photoemission using attosecond streaking

    Science.gov (United States)

    Nagele, S.; Pazourek, R.; Wais, M.; Wachter, G.; Burgdörfer, J.

    2014-04-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric efect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the feld-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for efective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes A@C60 and discuss how streaking time shifts are modifed due to the interaction of the C60 cage with the probing infrared streaking field.

  13. Stationary and time resolved PL spectroscopy for analysis of ultrafst photoreactions in MALDI and solar cell samples; Stationaere und zeitaufgeloeste Photolumineszenz-Spektroskopie zur Analyse ultraschneller Photoreaktionen in MALDI- und Solarzellenproben

    Energy Technology Data Exchange (ETDEWEB)

    Hoyer, Theo

    2009-02-12

    Stationary and time resolved measurements of photoluminescence (PL) were performed to analyse ultrafast photoreactions in solid MALDI (Matrix-Assisted Laser Desorption/Ionization) and solar cell samples. The investigation of pure cinnamic acid samples resulted in a first-time observation of a PL signature which is controlled by a photodimerisation on a ps- and fs-time scale. Other matrix compounds showed clear evidence of ultrafast photoinduced crystal reactions as well. In analyte/matrix mixtures consisting of angiotensin II and alpha-cyano-4-hydroxycinnamic acid or sinapinic acid, an additional effective PL quenching of matrix monomers was identified. This clearly indicates the existence of a further ultrafast photoreaction which strongly competes with the photodimerisation. The additional reaction is assumed to be a photoisomerisation of matrix monomers and to occur in the immediate vicinity of the analyte molecules. PL measurements on solar cell samples were performed with a P3HT/PCBM-mixture. The results show that within 150 fs about 50% of the P3HT-excitations relax via spontaneous charge transfer to PCBM molecules in this mixture.

  14. Space and time resolved spectroscopy of laser-produced plasmas: A study of density-sensitive x-ray transitions in helium-like and neon-like ions

    Energy Technology Data Exchange (ETDEWEB)

    Young, Bruce Kai Fong

    1988-09-01

    The determination of level populations and detailed population mechanisms in dense plasmas has become an increasingly important problem in atomic physics. In this work, the density variation of line intensities and level populations in aluminum K-shell and molybdenum and silver L-shell emission spectra have been measured from high-powered, laser-produced plasmas. For each case, the density dependence of the observed line emission is due to the effect of high frequency electron-ion collisions on metastable levels. The density dependent line intensities vary greatly in laser-produced plasmas and can be used to extract detailed information concerning the population kinetics and level populations of the ions. The laser-plasmas had to be fully characterized in order to clearly compare the observed density dependence with atomic theory predictions. This has been achieved through the combined use of new diagnostic instruments and microdot targets which provided simultaneously space, time, and spectrally resolved data. The plasma temperatures were determined from the slope of the hydrogen-like recombination continuum. The time resolved electron density profiles were measured using multiple frame holographic interferometry. Thus, the density dependence of K-shell spectral lines could be clearly examined, independent of assumptions concerning the dynamics of the plasma. In aluminum, the electron density dependence of various helium-like line intensity ratios were measured. Standard collisional radiative equilibrium models fail to account for the observed density dependence measured for the ''He/sub ..cap alpha..//IC'' ratio. Instead, a quasi-steady state atomic model based on a purely recombining plasma is shown to accurately predict the measured density dependence. This same recombining plasma calculation successfully models the density dependence of the high-n ''He/sub ..gamma..//He/sub ..beta../'' and ''He/sub delta

  15. Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics Lecture: Broadband Rotational Spectroscopy for Chemical Kinetics, Molecular Structure, and Analytical Chemistry

    Science.gov (United States)

    Pate, Brooks

    2013-03-01

    Advances in high-speed digital electronics have enabled a new generation of molecular rotational spectroscopy techniques that provide instantaneous broadband spectral coverage. These techniques use a chirped excitation pulse to coherently excite the molecular sample over a spectral bandwidth of 10 GHz or larger through rapid passage. The subsequent time-domain emission is recorded using high-speed digitizers (up to 100 Gigasample/s) and the frequency domain spectrum is produced by fast Fourier transformation. The chirped-pulse Fourier transform (CP-FT) method has been implemented in the microwave frequency range (2-40 GHz) for studies of cold samples in pulsed jet sources and in the mm-wave/terahertz (THz) frequency range for studies of samples at room-temperature. The method has opened new applications for molecular rotational spectroscopy in the area of chemical kinetics where dynamic rotational spectroscopy is used to measure the rates of unimolecular isomerization reactions in highly excited molecules prepared by pulsed infrared laser excitation. In these applications, the isomerization rate is obtained from an analysis of the overall line shapes which are modified by chemical exchange leading to coalescence behavior similar to the effect in NMR spectroscopy. The sensitivity of the method and the ability to extend it to low frequency (2-8 GHz) have significantly increased the size range of molecules and molecular clusters for structure determination using isotopic substitution to build up the 3D molecular structures atom-by-atom. Application to the structure of water clusters with up to 15 water molecules will be presented. When coupled with advances in solid-state mm-wave/THz devices, this method provides a direct digital technique for analytical chemistry of room-temperature gases based on molecular rotational spectroscopy. These high-throughput methods can analyze complex sample mixtures with unmatched chemical selectivity and short analysis times. Work

  16. Design of tri-level excitation signals for broadband bioimpedance spectroscopy.

    Science.gov (United States)

    Yang, Yuxiang; Wang, Lianhuan; Wang, Peipei; Yang, Xiufang; Zhang, Fu; Wen, He; Teng, Zhaosheng

    2015-09-01

    Bioimpedance spectroscopy (BIS) measurement methods have been evolving from the traditional frequency-sweep approach to the multi-frequency simultaneous measurement technique which can drastically reduce measuring time and will be increasingly attractive for time-varying biological applications. Multi-frequency mixed (MFM) signals with sparsely distributed spectra are desirable for broadband BIS measurement. This paper proposes a synthesis method to design a series of tri-level MFM signals which contain only three values (+1, 0, -1), and has majority energy distributed on its (2(n))th primary harmonics. Tri-level MFM signals have both high energy efficiency and a low crest factor. An impedance measurement experiment excited by an 8th-order tri-level MFM signal on a RC three-element equivalent model has been performed, and the results on 8 primary harmonic frequencies ranging from 8 to 1024 kHz show a high accuracy with the mean amplitude relative error of 0.41% and mean phase absolute error of 0.18°, which has validated the feasibility of the tri-level MFM signals for broadband BIS measurement.

  17. Broadband multi-resonant strong field coherence breaking as a tool for single isomer microwave spectroscopy

    Science.gov (United States)

    Hernandez-Castillo, A. O.; Abeysekera, Chamara; Hays, Brian M.; Zwier, Timothy S.

    2016-09-01

    Using standard hardware available in chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy, an experimental method is introduced to selectively extract from the microwave spectrum of an otherwise complicated multicomponent mixture a set of transitions due to a single component, thereby speeding spectral assignment. The method operates the broadband chirped-pulse used to excite the sample in the strong-field limit through a combination of high power and control of the sweep rate. A procedure is introduced that leads to selection of three transition frequencies that can be incorporated as a set of resonant sequential single-frequency microwave pulses that follow broadband chirped-pulse excitation, resulting in a reduction in the coherent signal from a set of transitions ascribable to the component of interest. The difference in the CP-FTMW spectrum with and without this set of multi-resonant single-frequency pulses produces a set of transitions that can confidently be assigned to a single component of the mixture, aiding the analysis of its spectrum. The scheme is applied to (i) selectively extract the spectrum of one of five singly 13C-subsituted isotopologues of benzonitrile in natural abundance, (ii) obtain the microwave spectra of the two structural isomers (E)- and (Z)-phenylvinylnitrile, and (iii) obtain conformer-specific microwave spectra of methylbutyrate.

  18. Broadband coherent anti-Stokes Raman spectroscopy with a modeless dye laser.

    Science.gov (United States)

    Hahn, J W; Park, C W; Park, S N

    1997-09-20

    We develop a modeless dye laser for broadband coherent anti-Stokes Raman spectroscopy (CARS) and investigate the operational characteristics of the modeless laser. The energy efficiency of the modeless laser is 6%, and the beam divergence is 0.65 mrad. We construct a compact movable CARS system with the modeless laser and a graphite tube furnace to assess the accuracy of the CARS temperature. It is found that the difference between the averaged CARS temperature and the radiation temperature measured with an optical pyrometer is <2% at a temperature range from 1000 to 2400 K. We also measure the averaged CARS temperature drift owing to the variation of the spectral distribution of the modeless laser, which is <1.5% during 5 h of operation.

  19. Time-resolved studies with FELs

    Energy Technology Data Exchange (ETDEWEB)

    Rudenko, Artem [J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS 66506 (United States); Max-Planck Institut für Kernphysik, 69117 Heidelberg (Germany); Rolles, Daniel, E-mail: Rolles@phys.ksu.edu [J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS 66506 (United States); Deutsches Elektronen Synchrotron (DESY), 22607 Hamburg (Germany)

    2015-10-15

    Highlights: • Free-electron lasers open up new possibilities for studying ultrafast dynamics. • We describe the current status of the field and recent exemplary experiments. • Experiments studying charge transfer in dissociating molecules are discussed. • Photoelectron diffraction from aligned gas-phase molecules is presented. • We give an outlook on future developments and perspectives. - Abstract: Intense femtosecond VUV, XUV, and X-ray pulses from free-electron lasers (FELs) enable time-resolved experiments studying ultrafast dynamics in a large variety of systems relevant, e.g., to physics, chemistry, biology, and material sciences. In this paper, we focus on time-resolved studies of gas-phase molecules, which lie at the crossroad between atomic, molecular and optical physics and ultrafast photochemistry. We describe the current status of the field and discuss typical experimental configurations used for pump-probe experiments with FELs. We illustrate them with three recent examples for such experiments performed at the FLASH and LCLS FELs studying charge transfer following XUV and X-ray photoabsorption as well as photoelectron diffraction from aligned molecules. We conclude with a short outlook on future developments and perspectives for femtosecond pump-probe experiments with FELs.

  20. Broadband photon time of flight spectroscopy: advanced spectroscopic analysis for ensuring safety and performance of pharmaceutical tablets

    DEFF Research Database (Denmark)

    Kamran, Faisal; Nielsen, Otto Højager Attermann; Andersson-Engels, Stefan

    2013-01-01

    We report on extended spectroscopic analysis of pharmaceutical tablets performed with broadband photon time-of-flight absorption/scaring spectroscopy. Precise monitoring of absorption and scattering spectra enables cost-efficient monitoring of key safety and performance parameters of the drugs....

  1. Decomposition of time-resolved tomographic PIV

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, Peter J. [Ecole Polytechnique, Laboratoire d' Hydrodynamique (LadHyX), Palaiseau (France); Violato, Daniele; Scarano, Fulvio [Delft University of Technology, Department of Aerospace Engineering, Delft (Netherlands)

    2012-06-15

    An experimental study has been conducted on a transitional water jet at a Reynolds number of Re = 5,000. Flow fields have been obtained by means of time-resolved tomographic particle image velocimetry capturing all relevant spatial and temporal scales. The measured three-dimensional flow fields have then been postprocessed by the dynamic mode decomposition which identifies coherent structures that contribute significantly to the dynamics of the jet. Both temporal and spatial analyses have been performed. Where the jet exhibits a primary axisymmetric instability followed by a pairing of the vortex rings, dominant dynamic modes have been extracted together with their amplitude distribution. These modes represent a basis for the low-dimensional description of the dominant flow features. (orig.)

  2. Time-Resolved Fluorescence in Photodynamic Therapy

    Directory of Open Access Journals (Sweden)

    Shu-Chi Allison Yeh

    2014-12-01

    Full Text Available Photodynamic therapy (PDT has been used clinically for treating various diseases including malignant tumors. The main advantages of PDT over traditional cancer treatments are attributed to the localized effects of the photochemical reactions by selective illumination, which then generate reactive oxygen species and singlet oxygen molecules that lead to cell death. To date, over- or under-treatment still remains one of the major challenges in PDT due to the lack of robust real-time dose monitoring techniques. Time-resolved fluorescence (TRF provides fluorescence lifetime profiles of the targeted fluorophores. It has been demonstrated that TRF offers supplementary information in drug-molecular interactions and cell responses compared to steady-state intensity acquisition. Moreover, fluorescence lifetime itself is independent of the light path; thus it overcomes the artifacts given by diffused light propagation and detection geometries. TRF in PDT is an emerging approach, and relevant studies to date are scattered. Therefore, this review mainly focuses on summarizing up-to-date TRF studies in PDT, and the effects of PDT dosimetric factors on the measured TRF parameters. From there, potential gaps for clinical translation are also discussed.

  3. Time-resolved tribo-thermography

    Science.gov (United States)

    Dinwiddie, Ralph B.; Blau, Peter J.

    1999-03-01

    Wear of coated surfaces tends to progress through a series of stages in which damage accumulates until the coating fails to protect its substrate. Depending on the coating system and the contact conditions, these stages can sometimes be detected as a series of discrete periods of changing frictional behavior, or they can occur quite rapidly, leading to rapid removal of the coating. A new technique has been developed to capture magnified infrared (IR) images of a selected location on a moving wear surface and to synchronize these cycle-by-cycle images with the instantaneous friction force that occurs at the same location. A pin-on-disk tribometer has been used to demonstrate the principle, but other kinds of test geometries can also be used. Contrast in the IR images derives not only from the surface temperatures but also from the emissivity of surface features. A spatial calibration of the system allows the measurement of the width of the wear path as a function of time. By studying a series of captured and friction- synchronized images, it is possible to observe the detailed progression of wear and the corresponding frictional transitions in a limitless variety of materials. Examples of several different materials, including, steel, aluminum, brass, and paint, will be used to illustrate the application of time-resolved microscopic tribo-thermography to coatings research.

  4. Kinetics and branching ratios of the reactions NH2+NO2->N2O+H2O and NH2+NO2->H2NO+NO studied by pulse radiolysis combined with time-resolved infrared diode laser spectroscopy

    DEFF Research Database (Denmark)

    Meunier, H.; Pagsberg, Palle Bjørn; Sillesen, A.

    1996-01-01

    The source reaction F + NH3 --> HF + NH2 was initiated by the pulse radiolysis of NH3/SF6 mixtures, and the primary yield of F atoms was determined by monitoring the decrease in the infrared absorption of methane consumed in the titration reaction F + CH4 --> HF + CH3. The title reactions have been...... studied by monitoring the decay of NH2 and the simultaneous formation of N2O and NO by time-resolved infrared diode laser spectroscopy. The decay rate of NH2 was studied as a function of NO2 concentration to obtain an overall rate constant k(NH2 + NO2) = (1.35 +/- 0.15) X 10(-11) molecule(-1) cm(3) s(-1...

  5. Optical-Fiber-Type Broadband Cavity Ring-Down Spectroscopy Using Wavelength-Tunable Ultrashort Pulsed Light

    Science.gov (United States)

    Hiraoka, Takehiro; Ohta, Takayuki; Ito, Masafumi; Nishizawa, Norihiko; Hori, Masaru

    2013-04-01

    We proposed an optical-fiber-type broadband cavity ring-down spectroscopy system using wavelength-tunable ultrashort pulsed light. The absorbance of glucose in various concentrations in water was derived from the ring-down plots of intensities of the interference waveforms generated using a Mach-Zehnder interferometer with different optical delay path lengths, which were shifted by an automatic optical switching module. The absorption spectrum of glucose was obtained in the wavelength region from 1620 to 1690 nm by varying the wavelength using wavelength-tunable ultrashort pulsed light, which was generated from a femtosecond pulsed laser and polarization-maintaining fiber. The measurement error of concentration was improved using multiple linear regression analysis of absorption spectra. The results demonstrate that the optical-fiber-type cavity ring-down spectroscopy system has the potential to measure broadband absorption spectra with high sensitivity.

  6. Broadband spectroscopy of the electromagnetic properties of aqueous ferrofluids for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Bellizzi, G., E-mail: gbellizz@unina.i [Dipartimento di Ingegneria Biomedica, Elettronica e delle Telecomunicazioni, Universita di Napoli Federico II, via Claudio 21, 80125 Napoli (Italy); Bucci, O.M. [Dipartimento di Ingegneria Biomedica, Elettronica e delle Telecomunicazioni, Universita di Napoli Federico II, via Claudio 21, 80125 Napoli (Italy); Istituto per il Rilevamento Elettromagnetico dell' Ambiente - Consiglio Nazionale delle Ricerche, via Diocleziano 328, I-80124 Napoli (Italy); Capozzoli, A. [Dipartimento di Ingegneria Biomedica, Elettronica e delle Telecomunicazioni, Universita di Napoli Federico II, via Claudio 21, 80125 Napoli (Italy)

    2010-10-15

    This paper presents the results of a broadband spectroscopy study, over the frequency range 1 MHz-2 GHz, of the electromagnetic properties of a ferrofluid consisting of magnetite nanoparticles, with a mean magnetic size of 10 nm, dispersed in water. An innovative measurement approach and apparatus, allowing an accurate determination of the permeability, even in presence of a large permittivity, have been developed to characterize the suspension. The results obtained show a significant magnetic response over the whole analyzed frequency range, with a good agreement with the theoretical models describing the magnetization dynamics of these systems. Moreover, a strong dielectric response has been detected, which is in satisfactory agreement with the models developed to describe the dielectric behavior of charged nanoparticles suspended in aqueous solution. This result implies that measurement techniques able to determine both the permittivity and permeability become mandatory for a reliable determination of the magnetic properties of aqueous ferrofluids. The accuracy of the determined permeability spectrum is estimated to be of the order of few percent, so these results provide a reliable experimental basis to estimate how fruitful the use of magnetic nanoparticles can be in relevant biomedical applications.

  7. Measurements of Iodine Monoxide Levels During the CAST Campaign Using Broadband Cavity Enhanced Absorption Spectroscopy

    Science.gov (United States)

    Harris, N. R. P.; Popoola, O. A.; McLeod, M.; Ouyang, B.; Jones, R. L.

    2014-12-01

    Iodine monoxide (IO) has been regarded as an important radical involved in the ozone destruction in the remote marine boundary layer. Here we presented the first in situ aircraft measurements of IO using broadband cavity enhanced absorption spectroscopy with 1s -sensitivity of ~1.5 ppt Hz-1/2 on the surface level during the Coordinated Airborne Studies in the Tropics (CAST) campaign between January - February 2014. IO was retrieved from analysis of absorption spectrum recorded between 415 nm - 452.5 nm. Instrument baseline corresponding to the "zero" signal of IO was obtained by injection of ~20 ppb of nitric oxide (NO) into the sample air at chosen frequency and period. No clear absorption feature was observable from the spectra by eye with up to 100 seconds averaging, pointing to very low mixing ratios (<~0.5 ppt) of IO over the sampled area. A small positive bias (~0.3 ppt) of IO (against the baseline signal during NO titration) was obtained in the statistical histogram of retrieved IO from average of each straight and level run, but little altitude dependence was noted. In summary, our observation appears to support the existence of IO in the remote marine boundary above the Pacific Ocean at sub ppt levels, but the limited sensitivity precludes us from quantifying spatial gradients more accurately.

  8. Molecular dynamics of amorphous pharmaceutical fenofibrate studied by broadband dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    U. Sailaja

    2016-06-01

    Full Text Available Fenofibrate is mainly used to reduce cholesterol level in patients at risk of cardiovascular disease. Thermal transition study with the help of differential scanning calorimetry (DSC shows that the aforesaid active pharmaceutical ingredient (API is a good glass former. Based on our DSC study, the molecular dynamics of this API has been carried out by broadband dielectric spectroscopy (BDS covering wide temperature and frequency ranges. Dielectric measurements of amorphous fenofibrate were performed after its vitrification by fast cooling from a few degrees above the melting point (Tm=354.11 K to deep glassy state. The sample does not show any crystallization tendency during cooling and reaches the glassy state. The temperature dependence of the structural relaxation has been fitted by single Vogel–Fulcher–Tamman (VFT equation. From VFT fit, glass transition temperature (Tg was estimated as 250.56 K and fragility (m was determined as 94.02. This drug is classified as a fragile glass former. Deviations of experimental data from Kohlrausch–Williams–Watts (KWW fits on high-frequency flank of α-peak indicate the presence of an excess wing in fenofibrate. Based on Ngai׳s coupling model, we identified the excess wing as true Johari–Goldstein (JG process. Below the glass transition temperature one can clearly see a secondary relaxation (γ with an activation energy of 32.67 kJ/mol.

  9. Broadband Bioimpedance Spectroscopy Based on a Multifrequency Mixed Excitation and Nuttall Windowed FFT Algorithm

    Directory of Open Access Journals (Sweden)

    Yuxiang Yang

    2014-01-01

    Full Text Available Bioimpedance spectroscopy (BIS has become an important clinical indicator for monitoring the pathological status of biological tissues, and multifrequency simultaneous measurement of BIS may provide more accurate diagnostic information compared with the traditional frequency-sweep measurement technology. This paper proposes a BIS multifrequency simultaneous measurement method based on multifrequency mixed (MFM signal excitation and a Nuttall windowed interpolation FFT algorithm. Firstly, the excitation source adopts the nine-frequency MFM signal f(9,t, which has excellent spectral characteristic and is very suitable for BIS measurement. On this basis, a Nuttall window is adopted to truncate sample data, and an interpolation FFT algorithm based on Nuttall window is built to perform spectral analysis, in which the parameter correction formula is provided based on polynomial approximation. A BIS measurement simulation experiment is performed on an RC three-element equivalent circuit, and results on the 9 primary harmonic frequencies ranging from 3.9 kHz to 1 MHz show a high accuracy with the impedance amplitude relative error |Ez|<0.3%, and the phase absolute error |Ep|<0.1°. This paper validates the feasibility of BIS multifrequency simultaneous measurement method and establishes an algorithm foundation for the development of practical broadband BIS measurement system.

  10. Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy

    Science.gov (United States)

    Rutkowski, Lucile; Morville, Jérôme

    2017-01-01

    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique which allows us to record broadband spectra at high sensitivity and GHz resolution (Rutkowski and Morville, 2014) [1]. We discuss here the effect of Vernier filtering on the observed lineshapes in the 3 ν + δ band of water vapor and the entire A-band of oxygen around 800 nm in ambient air. We derive expressions for the absorption profiles resulting from the continuous Vernier filtering method, testing them on spectra covering more than 2000 cm-1 around 12,500 cm-1. With 31,300 independent spectral elements acquired at the second time scale, an absorption baseline noise of 2 ×10-8cm-1 is obtained, providing a figure of merit of 1.1×10-10 cm-1/√{ Hz } per spectral element with a cavity finesse of 3000 and a cavity round-trip length around 3.3 m.

  11. Ultra-Broadband Two-Dimensional Electronic Spectroscopy and Pump-Probe Microscopy of Molecular Systems

    Science.gov (United States)

    Spokoyny, Boris M.

    Ultrafast spectroscopy offers an unprecedented view on the dynamic nature of chemical reactions. From charge transfer in semiconductors to folding and isomerization of proteins, these all important processes can now be monitored and in some instances even controlled on real, physical timescales. One of the biggest challenges of ultrafast science is the incredible energetic complexity of most systems. It is not uncommon to encounter macromolecules or materials with absorption spectra spanning significant portions of the visible spectrum. Monitoring a multitude of electronic and vibrational transitions, all dynamically interacting with each other on femtosecond timescales poses a truly daunting experimental task. The first part of this thesis deals with the development of a novel Two-Dimensional Electronic Spectroscopy (2DES) and its associated, advanced detection methodologies. Owing to its ultra-broadband implementation, this technique enables us to monitor femtosecond chemical dynamics that span the energetic landscape of the entire visible spectrum. In order to demonstrate the utility of our method, we apply it to two laser dye molecules, IR-144 and Cresyl Violet. Variation of photophysical properties on a microscopic scale in either man-made or naturally occurring systems can have profound implications on how we understand their macroscopic properties. Recently, inorganic hybrid perovskites have been tapped as the next generation solar energy harvesting materials. Their remarkable properties include low exciton binding energy, low exciton recombination rates and long carrier diffusion lengths. Nevertheless, considerable variability in device properties made with nearly identical preparation methods has puzzled the community. In the second part of this thesis we use non-linear pump probe microscopy to study the heterogeneous nature of femtosecond carrier dynamics in thin film perovskites. We show that the local morphology of the perovskite thin films has a

  12. Time resolved spectroscopy of the cool Ap star HD 213637*

    Science.gov (United States)

    Elkin, V. G.; Kurtz, D. W.; Mathys, G.

    2015-02-01

    We present an analysis of high time resolution spectra of the chemically peculiar Ap star HD 213637. The star shows rapid radial velocity variations with a period close to the photometric pulsation period. Radial velocity pulsation amplitudes vary significantly for different rare earth elements. The highest pulsation amplitudes belong to lines of Tb III (˜360 m s-1), Pr II (˜250 m s-1) and Pr III (˜230 m s-1). We did not detect any pulsations from spectral lines of Eu II and in Hα, in contrast to many other roAp stars. We also did not find radial velocity pulsations using spectral lines of other chemical elements, including Mg, Si, Ca, Sc, Cr, Fe, Ni, Y and Ba. There are phase shifts between the maxima of pulsation amplitudes of different rare earth elements and ions, which is evidence of an outwardly running magneto-acoustic wave propagating through the upper stellar atmosphere.

  13. Time Resolved Spectroscopy of High Field Polars (FUSE 00)

    Science.gov (United States)

    Barrett, Paul

    2004-01-01

    The following work has been accomplished: 1) The emission lines of O VI1 and He II were used to produce Doppler tomograms of the plasma emission. 2) An improved interstellar absorption model is being developed for the CIAO spectral fitting program, Sherpa. Use of the earlier version of this model showed it to be inadequate for its purpose. Once this model is working, we intend to complete our analysis of V884 Her and those of other FUSE programs. In addition to the above work, this grant has helped support the following related work: 1) The publication of the paper "Periodicities in the X-ray intensity variations of TV Columbae: an Intermediate Polar" by Rana, V. R., Singh, K. P., Schlegel, E. M., & Barrett, P. 2004, AJ, 126,489, and 2) FUSE data of a possible nova-like variable Ret 1 has been analyzed and shown to contain a hot (37000 deg) white dwarf (WD 0334-6400). The FUV spectrum shows strong absorption lines of C III.

  14. Pulsed Green Laser for Time Resolved Raman Spectroscopy Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort will demonstrate the feasibility of developing a fully packaged, efficient, short pulse, high repetition rate frequency doubled micro-chip...

  15. Time-Resolved Emission Spectroscopy of Field Reversed Configuration Thruster

    Science.gov (United States)

    2016-08-31

    currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 01 November 2016 2. REPORT TYPE ...supernovae in ultra- luminous infrared galaxies (ULIRGs) 4Distribution A: Approved for Public Release; Distribution Unlimited. PA# 16468 Objective To

  16. Broadband diffuse optical spectroscopy assessment of hemorrhage- and hemoglobin-based blood substitute resuscitation

    Science.gov (United States)

    Lee, Jangwoen; Kim, Jae G.; Mahon, Sari; Tromberg, Bruce J.; Mukai, David; Kreuter, Kelly; Saltzman, Darin; Patino, Renee; Goldberg, Robert; Brenner, Matthew

    2009-07-01

    Hemoglobin-based oxygen carriers (HBOCs) are solutions of cell-free hemoglobin (Hb) that have been developed for replacement or augmentation of blood transfusion. It is important to monitor in vivo tissue hemoglobin content, total tissue hemoglobin [THb], oxy- and deoxy-hemoglobin concentrations ([OHb], [RHb]), and tissue oxygen saturation (StO2=[OHb]/[THb]×100%) to evaluate effectiveness of HBOC transfusion. We designed and constructed a broadband diffuse optical spectroscopy (DOS) prototype system to measure bulk tissue absorption and scattering spectra between 650 and 1000 nm capable of accurately determining these tissue hemoglobin component concentrations in vivo. Our purpose was to assess the feasibility of using DOS to optically monitor tissue [OHb], [RHb], StO2, and total tissue hemoglobin concentration ([THb]=[OHb]+[RHb]) during HBOC infusion using a rabbit hypovolemic shock model. The DOS prototype probe was placed on the shaved inner thigh muscle of the hind leg to assess concentrations of [OHb], [RHb], [THb], as well as StO2. Hemorrhagic shock was induced in intubated New Zealand white rabbits (N=6) by withdrawing blood via a femoral arterial line to 20% blood loss (10-15 cc/kg). Hemoglobin glutamer-200 (Hb-200) 1:1 volume resuscitation was administered following the hemorrhage. These values were compared against traditional invasive measurements, serum hemoglobin concentration (sHGB), systemic blood pressure, heart rate, and blood gases. DOS revealed increases of [THb], [OHb], and tissue hemoglobin oxygen saturation after Hb-200 infusion, while blood total hemoglobin values continued did not increase; we speculate, due to hyperosmolality induced hemodilution. DOS enables noninvasive in vivo monitoring of tissue hemoglobin and oxygenation parameters during shock and volume expansion with HBOC and potentially enables the assessment of efficacy of resuscitation efforts using artificial blood substitutes.

  17. Broadband Microwave Spectroscopy as a Tool to Study Dispersion Interactions in Camphor-Alcohol Systems

    Science.gov (United States)

    Fatima, Mariyam; Perez, Cristobal; Schnell, Melanie

    2016-06-01

    Many biological processes such as chemical recognition and protein folding are mainly controlled by the interplay between hydrogen bonds and dispersive forces. Broadband rotational spectroscopy studies of weakly bound complexes are able to accurately reveal the structures and internal dynamics of molecular clusters isolated in the gas phase. To investigate the influence of the interplay between different types of weak intermolecular interactions and how it controls the preferred active sites of an amphiphilic molecule, we are using camphor (C10H16O, 1,7,7-trimethylbicyclo[2.2.1]hepta-2-one) with different aliphatic alcohol systems. Camphor is a conformationally rigid bicyclic molecule endowed with considerable steric hindrance and has a single polar group (-C=O). The rotational spectrum of camphor and its structure has been previously reported [1] as well as multiple clusters with water [2]. In order to determine the structure of the camphor-alcohol complexes, we targeted low energy rotational transitions in the 2-8 GHz range under the isolated conditions of a molecular jet in the gas phase. The data obtained suggests that camphor forms one complex with methanol and two with ethanol, with differences in the intermolecular interaction in both complexes. With these results, we aim to study the shift in intermolecular interaction from hydrogen bonding to dispersion with the increase in the size of the aliphatic alcohol. [1] Z. Kisiel, et al., Phys. Chem. Chem. Phys., 5 (2003), 820-826. [2] C. Pérez, et al, J. Phys. Chem. Lett., 7 (2016), 154-160.

  18. Advances in high-order harmonic generation sources for time-resolved investigations

    Energy Technology Data Exchange (ETDEWEB)

    Reduzzi, Maurizio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Carpeggiani, Paolo [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Kühn, Sergei [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Calegari, Francesca [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Nisoli, Mauro; Stagira, Salvatore [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Vozzi, Caterina [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Dombi, Peter [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Wigner Research Center for Physics, 1121 Budapest (Hungary); Kahaly, Subhendu [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Tzallas, Paris; Charalambidis, Dimitris [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Foundation for Research and Technology – Hellas, Institute of Electronic Structure and Lasers, P.O. Box 1527, GR-711 10 Heraklion, Crete (Greece); Varju, Katalin [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Department of Optics and Quantum Electronics, University of Szeged, Dóm tér 9, 6720 Szeged (Hungary); Osvay, Karoly [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); and others

    2015-10-15

    We review the main research directions ongoing in the development of extreme ultraviolet sources based on high-harmonic generation for the synthesization and application of trains and isolated attosecond pulses to time-resolved spectroscopy. A few experimental and theoretical works will be discussed in connection to well-established attosecond techniques. In this context, we present the unique possibilities offered for time-resolved investigations on the attosecond timescale by the new Extreme Light Infrastructure Attosecond Light Pulse Source, which is currently under construction.

  19. Time resolved resonant photoemission study of energy level alignment at donor/acceptor interfaces

    Science.gov (United States)

    Costantini, R.; Pincelli, T.; Cossaro, A.; Verdini, A.; Goldoni, A.; Cichoň, S.; Caputo, M.; Pedio, M.; Panaccione, G.; Silly, M. G.; Sirotti, F.; Morgante, A.; Dell'Angela, M.

    2017-09-01

    The knowledge of the picosecond dynamics of the energy level alignment between donor and acceptor materials in organic photovoltaic devices under working conditions is a challenge for fundamental material research. We measured by means of time-resolved Resonant X-ray Photoemission Spectroscopy (RPES) the energy level alignment in ZnPc/C60 films. We employed 800 nm femtosecond laser pulses to pump the system simulating sunlight excitation and X-rays from the synchrotron as a probe. We measured changes in the valence bands due to pump induced modifications of the interface dipole. Our measurements prove the feasibility of time-resolved RPES with high repetition rate sources.

  20. Direct time-resolved spectroscopic investigation of intramolecular hydrogen atom transfer of deoxyblebbistatin

    Science.gov (United States)

    Li, Ming-De; Zhu, Ruixue; Lee Phillips, David

    2017-09-01

    The photophysics and photochemistry of deoxyblebbistatin was investigated using femtosecond time-resolved transient absorption spectroscopy. An ultrafast intramolecular hydrogen atom transfer (IHAT) appears to take place via the first singlet excited state of deoxyblebbistatin within 8 ps. Absorption and fluorescence photochemical results indicate the IHAT process leads to mainly conversion of deoxyblebbistatin into an enol form final product which was observed and characterized by resonance Raman spectroscopy.

  1. Effects of cations and cholesterol with sphingomyelin membranes investigated by high-resolution broadband sum frequency vibrational spectroscopy

    Science.gov (United States)

    Zhang, Zhen; Feng, Rong-juan; Li, Yi-yi; Liu, Ming-hua; Guo, Yuan

    2017-08-01

    Sphingomyelin(SM) is specifically enriched in the plasma membrane of mammalian cells. Its molecular structure is compose by N-acyl-Derythro-sphingosylphosphorylcholine. The function of the SM related to membrane signaling and protein trafficking are relied on the interactions of the SM, cations, cholesterol and proteins. In this report, the interaction of three different nature SMs, cations and cholesterol at air/aqueous interfaces studied by high-resolution broadband sum frequency vibrational spectroscopy, respectively. Our results shed lights on understanding the relationship between SMs monolayer, cholesterol and Cations.

  2. Time-resolved infrared spectroscopic techniques as applied to Channelrhodopsin

    Directory of Open Access Journals (Sweden)

    Eglof eRitter

    2015-07-01

    Full Text Available Among optogenetic tools, channelrhodopsins, the light gated ion channels of the plasma membrane from green algae, play the most important role. Properties like channel selectivity, timing parameters or color can be influenced by the exchange of selected amino acids. Although widely used, in the field of neurosciences for example, there is still little known about their photocycles and the mechanism of ion channel gating and conductance. One of the preferred methods for these studies is infrared spectroscopy since it allows observation of proteins and their function at a molecular level and in near-native environment. The absorption of a photon in channelrhodopsin leads to retinal isomerization within femtoseconds, the conductive states are reached in the microsecond time scale and the return into the fully dark-adapted state may take more than minutes. To be able to cover all these time regimes, a range of different spectroscopical approaches are necessary. This mini-review focuses on time-resolved applications of the infrared technique to study channelrhodopsins and other light triggered proteins. We will discuss the approaches with respect to their suitability to the investigation of channelrhodopsin and related proteins.

  3. Novel lanthanide doped micro- and mesoporous solids. Characterization of ion-host-interactions, species distribution and luminescence properties using time-resolved luminescence spectroscopy; Neuartige Lanthanoid-dotierte mikro- und mesoporoese Feststoffe. Charakterisierung von Ion-Wirt-Wechselwirkungen, Speziesverteilung und Lumineszenzeigenschaften mittels zeitaufgeloester Lumineszenzspektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Gessner, Andre

    2010-12-15

    In this work lanthanide-doped microporous zeolites, microporous-mesoporous hybrid materials and mesoporous silicates were investigated regarding their luminescence properties and the ion-host-interactions using time-resolved luminescence spectroscopy. Thereby, time-resolved emission spectra (TRES) provide information in the wavelength and time domain. For the analysis of the TRES a broad set of analytic methods was applied and thus a corresponding ''toolbox'' developed. Fitting of the luminescence decays was performed with a discrete number of exponentials and supported by luminescence decay times distributions. Time-resolved area normalized emission spectra (TRANES), an advancement of TRES, could be used for the determination of the number of emissive lanthanide species in porous materials for the first time. Calculation of the decay-associated spectra (DAS) allowed the correlation of spectral information with luminescence decay times and thus delivered the luminescence spectra of the different europium species. For europium(III) we could use in addition the time-dependent asymmetry ratio and spectral evolution of the {sup 5}D{sub 0}-{sup 7}F{sub 0}-transition with time to obtain further information about the distribution of the lanthanide ions in the host material. Luminescence decay times and spectra allowed conclusions on the number of OH-oscillators in and the symmetry of the first coordination sphere. For the microporous and microporous-mesoporous materials were found different lanthanide species, which were characterized by the above mentioned methods. These lanthanide species can be found on different positions in the host material. One position is located deep in the pore system. Here, lanthanide ions are hardly accessible for water and mainly coordinated by framework oxygens. This results in long luminescence decay times and distorted coordination spheres. The second position can be found near or on the outer surface or in the

  4. Time-resolved Chemical Imaging of Molecules by High-order Harmonics and Ultrashort Rescattering Electrons

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chii Dong [Kansas State Univ., Manhattan, KS (United States)

    2016-03-21

    Directly monitoring atomic motion during a molecular transformation with atomic-scale spatio-temporal resolution is a frontier of ultrafast optical science and physical chemistry. Here we provide the foundation for a new imaging method, fixed-angle broadband laser-induced electron scattering, based on structural retrieval by direct one-dimensional Fourier transform of a photoelectron energy distribution observed along the polarization direction of an intense ultrafast light pulse. The approach exploits the scattering of a broadband wave packet created by strong-field tunnel ionization to self-interrogate the molecular structure with picometre spatial resolution and bond specificity. With its inherent femtosecond resolution, combining our technique with molecular alignment can, in principle, provide the basis for time-resolved tomography for multi-dimensional transient structural determination.

  5. Insights into the Structural Changes Occurring upon Photoconversion in the Orange Carotenoid Protein from Broadband Two-Dimensional Electronic Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    De Re, Eleonora; Schlau-Cohen, Gabriela S.; Leverenz, Ryan L.; Huxter, Vanessa M.; Oliver, Thomas A. A.; Mathies, Richard A.; Fleming, Graham R.

    2014-05-22

    Carotenoids play an essential role in photoprotection, interacting with other pigments to safely dissipate excess absorbed energy as heat. In cyanobacteria, the short time scale photoprotective mechanisms involve the photoactive orange carotenoid protein (OCP), which binds a single carbonyl carotenoid. Blue-green light induces the photoswitching of OCP from its ground state form (OCPO) to a metastable photoproduct (OCPR). OCPR can bind to the phycobilisome antenna and induce fluorescence quenching. The photoswitching is accompanied by structural and functional changes at the level of the protein and of the bound carotenoid. In this study, we use broadband two-dimensional electronic spectroscopy to look at the differences in excited state dynamics of the carotenoid in the two forms of OCP. Our results provide insight into the origin of the pronounced vibrational lineshape and oscillatory dynamics observed in linear absorption and 2D electronic spectroscopy of OCPO and the large inhomogeneous broadening in OCPR, with consequences for the chemical function of the two forms.

  6. Development of a hybrid broadband NIRS/diffusion correlation spectroscopy system to monitor preterm brain injury (Conference Presentation)

    Science.gov (United States)

    Rajaram, Ajay; St. Lawrence, Keith; Diop, Mamadou

    2017-02-01

    In Canada, 8% of births occur prematurely. Preterm infants weighing less than 1500g are at a high risk of neurodevelopmental impairment: 5-10% develop major disabilities such as cerebral palsy and 40-50% show other cognitive and behavioural deficits. The brain is vulnerable to periods of low cerebral blood flow (CBF) that can impair energy metabolism and cause tissue damage. There is, therefore, a need for an efficient neuromonitoring system to alert the neonatal intensive care team to clinically significant changes in CBF and metabolism, before injury occurs. Optical technologies offer safe, non-invasive, and cost-effective methods for neuromonitoring. Cerebral oxygen saturation (ScO2) can be measured by exploiting the absorption properties of hemoglobin though Near-Infrared Spectroscopy (NIRS), and Diffuse Correlation Spectroscopy (DCS) can monitor CBF by tracking red blood cells. These measures can be combined to describe metabolism, a key indicator of tissue viability. In this study we present the development and testing of a hybrid broadband NIRS/DCS neuromonitor. This system is novel in its ability to simultaneously acquire broadband NIRS and DCS signals, providing a truly real-time measure of metabolism. Narrow bandpass and notch filters have been incorporated to diminish light contamination between the two modalities, preferentially filtering out each source from the opposing detector, allowing for an accurate measure of ScO2, CBF, and metabolism. With a broadband NIRS/DCS system, a real-time measure of CBF and metabolism within the developing brain can aid clinicians in monitoring events that precede brain injury, ultimately leading to better clinical outcomes.

  7. Broadband spectroscopy for characterization of tissue-like phantom optical properties

    Science.gov (United States)

    Shahin, Ali; Bachir, Wesam

    2017-12-01

    Optical phantoms are widely used for evaluating the performance of biomedical optical modalities, and hence, absorbing and scattering materials are required for the construction of optical phantoms. Towards that aim, new readily available and inexpensive black Ink (Parker) as a simulating absorber as well as Intralipid 20% as a simulating scatterer are thoroughly investigated. Broadband Transmittance and Diffuse reflectance spectroscopic measurements were performed in the visible range 400 - 700 nm. Optical properties of the phantom materials are determined. Analytical expressions for absorption and scattering coefficient related to the concentrations and wavelength of the Parker ink and Intralipid are also presented and discussed. The results show nonlinear trend in the absorption coefficient of Parker ink over the examined visible spectral range. Furthermore, Intralipid scattering coefficient variation across the mentioned spectral range shows a tissue-like scattering trend. The findings demonstrate the capability of the broadband transmission and diffuse reflectance for characterizing tissue-like phantom materials in the examined spectral range.

  8. Glucose Sensing by Time-Resolved Fluorescence of Sol-Gel Immobilized Glucose Oxidase

    OpenAIRE

    Esposito, Rosario; Ventura, Bartolomeo Della; De Nicola, Sergio; Altucci, Carlo; Velotta, Raffaele; Mita, Damiano Gustavo; Lepore, Maria

    2011-01-01

    A monolithic silica gel matrix with entrapped glucose oxidase (GOD) was constructed as a bioactive element in an optical biosensor for glucose determination. Intrinsic fluorescence of free and immobilised GOD was investigated in the visible range in presence of different glucose concentrations by time-resolved spectroscopy with time-correlated single-photon counting detector. A three-exponential model was used for analysing the fluorescence transients. Fractional intensities and mean lifetime...

  9. The time-dependent emission of molecular iodine from Laminaria Digitata measured with incoherent broadband cavity-enhanced absorption spectroscopy

    Science.gov (United States)

    Dixneuf, S.

    2009-04-01

    The release of molecular iodine (I2) from the oceans into the atmosphere has been recognized to correlate strongly with ozone depletion events and aerosol formation in the Marine Boundary Layer (MBL), which affects in turn global radiative forcing. The detailed mechanisms and dominant sources leading to the observed concentrations of I2 in the marine troposphere are still under intense investigation. In a recent campaign on the Irish west coast at Mace Head Atmospheric Research Station [1], it was found that significant levels of molecular iodine correlated with times of low tide, suggesting that the emission of air-exposed macro-algae may be a prime source of molecular iodine in coastal areas [2]. To further investigate this hypothesis we tried to detect the I2 emission of the brown seaweed Laminaria digitata, one of the most efficient iodine accumulators among living systems, directly by means of highly sensitive incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) [3]. IBBCEAS combines a good temporal and spatial resolution with high molecule-specific detection limits [4] comparable to that of typical LP-DOAS. IBBCEAS thus complements LP-DOAS in the search for sources of tropospheric trace gases. In this presentation the first direct observation of the time dependence of molecular iodine emission from Laminaria digitata will be shown. Plants were studied under naturally occurring stress for quasi in situ conditions for many hours. Surprisingly, the release of I2 occurs in short, strong bursts with quasi-oscillatory behaviour, bearing similarities to well known "iodine clock reactions". References [1] Saiz-Lopez A. & Plane, J. M. C. Novel iodine chemistry in the marine boundary layer. Geophys. Res. Lett. 31, L04112 (2004) doi:10.1029/2003GL019215. [2] McFiggans, G., Coe, H., Burgess, R., Allan, J., Cubison, M., Alfarra, M. R., Saunders, R., Saiz-Lopez, A., Plane, J. M. C., Wevill, D. J., Carpenter, L. J., Rickard, A. R. & Monks, P. S. Direct

  10. Applying Broadband Dielectric Spectroscopy (BDS) for the Biophysical Characterization of Mammalian Tissues under a Variety of Cellular Stresses.

    Science.gov (United States)

    Souli, Maria P; Klonos, Panagiotis; Fragopoulou, Adamantia F; Mavragani, Ifigeneia V; Pateras, Ioannis S; Kostomitsopoulos, Nikolaos; Margaritis, Lukas H; Zoumpoulis, Pavlos; Kaklamanis, Loukas; Kletsas, Dimitris; Gorgoulis, Vassilis G; Kyritsis, Apostolos; Pissis, Polycarpos; Georgakilas, Alexandros G

    2017-04-15

    The dielectric properties of biological tissues can contribute non-invasively to a better characterization and understanding of the structural properties and physiology of living organisms. The question we asked, is whether these induced changes are effected by an endogenous or exogenous cellular stress, and can they be detected non-invasively in the form of a dielectric response, e.g., an AC conductivity switch in the broadband frequency spectrum. This study constitutes the first methodological approach for the detection of environmental stress-induced damage in mammalian tissues by the means of broadband dielectric spectroscopy (BDS) at the frequencies of 1-10⁶ Hz. Firstly, we used non-ionizing (NIR) and ionizing radiation (IR) as a typical environmental stress. Specifically, rats were exposed to either digital enhanced cordless telecommunication (DECT) radio frequency electromagnetic radiation or to γ-radiation, respectively. The other type of stress, characterized usually by high genomic instability, was the pathophysiological state of human cancer (lung and prostate). Analyzing the results of isothermal dielectric measurements provided information on the tissues' water fraction. In most cases, our methodology proved sufficient in detecting structural changes, especially in the case of IR and malignancy. Useful specific dielectric response patterns are detected and correlated with each type of stress. Our results point towards the development of a dielectric-based methodology for better understanding and, in a relatively invasive way, the biological and structural changes effected by radiation and developing lung or prostate cancer often associated with genomic instability.

  11. Broadband pump-probe spectroscopy with sub-10-fs resolution for probing ultrafast internal conversion and coherent phonons in carotenoids

    Energy Technology Data Exchange (ETDEWEB)

    Polli, D. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy); Antognazza, M.R. [Italian Institute of Technology, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy); Brida, D.; Lanzani, G. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy); Cerullo, G. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy)], E-mail: giulio.cerullo@fisi.polimi.it; De Silvestri, S. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy)

    2008-06-23

    We use pump-probe spectroscopy with broadband detection to study electronic energy relaxation and coherent vibrational dynamics in carotenoids. A fast optical multichannel analyzer combined with a non-collinear optical parametric amplifier allows simultaneous acquisition of the differential transmission dynamics on the 500-700 nm wavelength range with sub-10-fs temporal resolution. The broad spectral coverage enables on the one hand a detailed study of the ultrafast bright-to-dark state internal conversion process; on the other hand, the tracking of the motion of the vibrational wavepacket launched on the ground state multidimensional potential energy surface. We present results on all-trans {beta}-carotene and on a long-chain polyene in solution. The developed experimental setup enables the straightforward acquisition and analysis of coherent vibrational dynamics, highlighting time-frequency domain features with extreme resolution.

  12. Microfluidics: From crystallization to serial time-resolved crystallography

    Directory of Open Access Journals (Sweden)

    Shuo Sui

    2017-05-01

    Full Text Available Capturing protein structural dynamics in real-time has tremendous potential in elucidating biological functions and providing information for structure-based drug design. While time-resolved structure determination has long been considered inaccessible for a vast majority of protein targets, serial methods for crystallography have remarkable potential in facilitating such analyses. Here, we review the impact of microfluidic technologies on protein crystal growth and X-ray diffraction analysis. In particular, we focus on applications of microfluidics for use in serial crystallography experiments for the time-resolved determination of protein structural dynamics.

  13. Broadband spectroscopy of magnetic response in a nano-scale magnetic wire

    Science.gov (United States)

    Yamaguchi, A.; Motoi, K.; Miyajima, H.; Utsumi, Y.

    2014-09-01

    We measure the broadband spectra of magnetic response in a single layered ferromagnetic nano-scale wire in order to investigate the size effect on the ferromagnetic resonance. We found that the resonance frequency difference between 300-nm- and 5-μm-wide wires was varied by about 5 GHz due to the shape anisotropy. Furthermore, we experimentally detected the magnetization precession induced by the thermal fluctuation via the rectification of a radio-frequency (rf) current by incorporating an additional direct current (dc) by using Wheatstone bridge circuit. Our investigation renders that the shape anisotropy is of great importance to control the resonance frequency and to provide thermal stability of the microwave devices.

  14. Time-Resolved Small-Angle X-Ray Scattering

    NARCIS (Netherlands)

    ten Elshof, Johan E.; Besselink, R.; Stawski, Tomasz; Castricum, H.L.; Levy, D.; Zayat, M.

    2015-01-01

    This chapter focuses on time-resolved studies of nanostructure development in sol-gel liquids, that is, diluted sols, wet gels, and drying thin fffilms. The most commonly investigated classes of sol-gel materials are silica, organically modified silica, template-directed mesostructured silica,

  15. Time-resolved cryo-electron microscopy: Recent progress.

    Science.gov (United States)

    Frank, Joachim

    2017-06-16

    Time-resolved cryo-electron microscopy (cryo-EM) combines the known advantages of single-particle cryo-EM in visualizing molecular structure with the ability to dissect the time progress of a reaction between molecules in vitro. Here some of the recent progress of this methodology and its first biological applications are outlined. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Time-Resolved 2PPE and Time-Resolved PEEM as a Probe of LSP's in Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    D. Bayer

    2008-01-01

    Full Text Available The time-resolved two-photon photoemission technique (TR-2PPE has been applied to study static and dynamic properties of localized surface plasmons (LSP in silver nanoparticles. Laterally, integrated measurements show the difference between LSP excitation and nonresonant single electron-hole pair creation. Studies below the optical diffraction limit were performed with the detection method of time-resolved photoemission electron microscopy (TR-PEEM. This microscopy technique with a resolution down to 40 nm enables a systematic study of retardation effects across single nanoparticles. In addition, as will be shown in this paper, it is a highly sensitive sensor for coupling effects between nanoparticles.

  17. BROADBAND X-RAY IMAGING AND SPECTROSCOPY OF THE CRAB NEBULA AND PULSAR WITH NuSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Madsen, Kristin K.; Harrison, Fiona; Grefenstette, Brian W. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Reynolds, Stephen [Physics Department, NC State University, Raleigh, NC 27695 (United States); An, Hongjun [Department of Physics, McGill University, Montreal, Quebec, H3A 2T8 (Canada); Boggs, Steven; Craig, William W.; Zoglauer, Andreas [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, Finn E. [DTU Space, National Space Institute, Technical University of Denmark, Elektronvej 327, DK-2800 Lyngby (Denmark); Fryer, Chris L. [CCS-2, Los Alamos National Laboratory, Livermore, CA 94550 (United States); Hailey, Charles J.; Nynka, Melania [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Markwardt, Craig; Zhang, William [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2015-03-01

    We present broadband (3-78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power law in this energy band, spatially resolved spectroscopy of the nebula finds a break at ∼9 keV in the spectral photon index of the torus structure with a steepening characterized by ΔΓ ∼ 0.25. We also confirm a previously reported steepening in the pulsed spectrum, and quantify it with a broken power law with break energy at ∼12 keV and ΔΓ ∼ 0.27. We present spectral maps of the inner 100'' of the remnant and measure the size of the nebula as a function of energy in seven bands. These results find that the rate of shrinkage with energy of the torus size can be fitted by a power law with an index of γ = 0.094 ± 0.018, consistent with the predictions of Kennel and Coroniti. The change in size is more rapid in the NW direction, coinciding with the counter-jet where we find the index to be a factor of two larger. NuSTAR observed the Crab during the latter part of a γ-ray flare, but found no increase in flux in the 3-78 keV energy band.

  18. Broad-band dielectric spectroscopy of Ba 2NaNb 5O 15 single crystal

    Science.gov (United States)

    Buixaderas, E.; Porokhonskyy, V.; Paskhin, A.; Savinov, M.; Petzelt, J.

    2002-12-01

    Barium sodium niobate (BNN) single crystals are studied by IR spectroscopy, time-domain THz transmission spectroscopy, HF coaxial wave-guide technique and LF dielectric spectroscopy to cover the frequency range 10^2 10^{14} Hz in a wide temperature interval. The dielectric response parallel and perpendicular to the polar c-axis is discussed. The ferroelectric transition at T_c=830 K is driven by a relaxational soft mode coupled with another central-mode type relaxation which both gradually disappear on cooling in the ferroelectric phase. Below T_i the parameters of the expected IR active amplitudon were estimated. The low-temperature permittivity increase on cooling for the {ěc E}bot {ěc c} field direction has been explained by an incipient proper ferroelectric-ferroelastic transition driven by an IR and Raman active B2-symmetry soft mode.

  19. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

    DEFF Research Database (Denmark)

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.

    2016-01-01

    Frequency-comb-assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this Letter, we present a novel method using cascaded frequency agile diode lasers...

  20. Turbulent Statistics From Time-Resolved PIV Measurements of a Jet Using Empirical Mode Decomposition

    Science.gov (United States)

    Dahl, Milo D.

    2013-01-01

    Empirical mode decomposition is an adaptive signal processing method that when applied to a broadband signal, such as that generated by turbulence, acts as a set of band-pass filters. This process was applied to data from time-resolved, particle image velocimetry measurements of subsonic jets prior to computing the second-order, two-point, space-time correlations from which turbulent phase velocities and length and time scales could be determined. The application of this method to large sets of simultaneous time histories is new. In this initial study, the results are relevant to acoustic analogy source models for jet noise prediction. The high frequency portion of the results could provide the turbulent values for subgrid scale models for noise that is missed in large-eddy simulations. The results are also used to infer that the cross-correlations between different components of the decomposed signals at two points in space, neglected in this initial study, are important.

  1. Broadband integrated mid infrared light sources as enabling technology for point of caremid infrared spectroscopy

    Science.gov (United States)

    2017-08-20

    wavelengths is still in its infancy, resulting in mid-IR spectroscopy being currently restricted to academic proof-of- principle experiments only.
 This...journal paper has resulted. I am assuming that the author has just concentrated on finishing this thesis and has not had time to write these papers...I sincerely hope that Xiantao Jiang will find the time to write these papers.” Indeed, we are currently in the process of writing those papers in

  2. Mapping Charge Carrier Density in Organic Thin-Film Transistors by Time-Resolved Photoluminescence Lifetime Studies

    DEFF Research Database (Denmark)

    Leißner, Till; Jensen, Per Baunegaard With; Liu, Yiming

    2017-01-01

    /organic interface or at grain boundaries. In our comprehensive experimental and analytical work we demonstrate a method to characterize the charge carrier density in organic thin-film transistors using time-resolved photoluminescence spectroscopy. We developed a numerical model that describes the electrical...

  3. High-performance broad-band spectroscopy for breast cancer risk assessment

    Science.gov (United States)

    Pawluczyk, Olga; Blackmore, Kristina; Dick, Samantha; Lilge, Lothar

    2005-09-01

    Medical diagnostics and screening are becoming increasingly demanding applications for spectroscopy. Although for many years the demand was satisfied with traditional spectrometers, analysis of complex biological samples has created a need for instruments capable of detecting small differences between samples. One such application is the measurement of absorbance of broad spectrum illumination by breast tissue, in order to quantify the breast tissue density. Studies have shown that breast cancer risk is closely associated with the measurement of radiographic breast density measurement. Using signal attenuation in transillumination spectroscopy in the 550-1100nm spectral range to measure breast density, has the potential to reduce the frequency of ionizing radiation, or making the test accessible to younger women; lower the cost and make the procedure more comfortable for the patient. In order to determine breast density, small spectral variances over a total attenuation of up to 8 OD have to be detected with the spectrophotometer. For this, a high performance system has been developed. The system uses Volume Phase Holographic (VPH) transmission grating, a 2D detector array for simultaneous registration of the whole spectrum with high signal to noise ratio, dedicated optical system specifically optimized for spectroscopic applications and many other improvements. The signal to noise ratio exceeding 50,000 for a single data acquisition eliminates the need for nitrogen cooled detectors and provides sufficient information to predict breast tissue density. Current studies employing transillumination breast spectroscopy (TIBS) relating to breast cancer risk assessment and monitoring are described.

  4. Benchtop time-resolved magneto-optical Kerr magnetometer.

    Science.gov (United States)

    Barman, Anjan; Kimura, T; Otani, Y; Fukuma, Y; Akahane, K; Meguro, S

    2008-12-01

    We present here the construction and application of a compact benchtop time-resolved Kerr magnetometer to measure the magnetization precession in magnetic thin films and lithographically patterned elements. As opposed to very expensive femtosecond lasers this system is built upon a picosecond pulsed injection diode laser and electronic pulse and delay generators. The precession is triggered by the electronic pulses of controlled duration and shape, which is launched onto the sample by a microstrip line. We used polarized optical pulses synchronous to the electronic pulses to measure the magneto-optical Kerr rotation. The system is integrated in a conventional upright microscope configuration with separate illumination, imaging, and magneto-optical probe paths. The system offers high stability, relative ease of alignment, sample changing, and a long range of time delay. We demonstrate the measurements of time-resolved dynamics of a Permalloy microwire and microdot using this system, which showed dynamics at two different time scales.

  5. Logarithmic based optical delay for time-resolved data collection.

    Science.gov (United States)

    Cole, Richard L; Barisas, B George; Levinger, Nancy E

    2010-09-01

    A method has been established that generates values spaced according to a mathematical function, specifically the logarithm function that can be applied to a stepper motor. Here, it is applied to yield logarithmically spaced time delay points for subnanosecond interferometric time-resolved experiments using a stepper motor controlled translation stage. Application of this method is discussed in terms of three input parameters: the optical delay stage time resolution, dt; the time of maximum delay, d(stop); and the desired number of data points, N. The method improves the efficiency of interferometric time-resolved data collection while providing data collection effective to determine decay parameters. In principle, this technique could be generalized to any mathematical function.

  6. Gated detector for time-resolved photoemission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wiemann, Carsten; Kaiser, Alexander; Cramm, Stefan; Schneider, Claus M. [Forschungszentrum Juelich (Germany)

    2008-07-01

    Photoemission microscopy in combination with X-ray circular dichroism is a well established tool to image magnetic domain patterns in micrometer sized structures. Apart from imaging static magnetization patterns, the microscope can be integrated in a time-resolved setup. Here a magnetic field pulse is used to excite a dynamic response of the micromagnetic ordering in the structures, which is in turn imaged by pulsed X-ray illumination from a synchrotron source. With this technique, precession dynamics and domain wall movements in polycristalline permalloy structures have already been successfully investigated. However, the timing requirements make it necessary to use single-bunch beam conditions for these experiments. Here, we present and compare two different approaches for fast switching of the imaging unit of the microscope in order to exploit the hybrid bunch in the normal injection pattern of Bessy II for time-resolved experiments.

  7. Time-resolved potentiometry on liquid-liquid interface

    OpenAIRE

    Mansfeldová, Věra

    2017-01-01

    MSc. Věra Mansfeldová Dissertation thesis: Time-resolved potentiometry on liquid-liquid interface Abstract The aim of this work is to explore the method of temporal resolution in potentiometry as a new prospective electrochemical analytical technique. In connection with interface of two immiscible electrolyte solutions (ITIES) it may find utilization in analytical chemistry. This technique up to my knowledge has not been published yet. Potential response of analyte on liquid/liquid interface ...

  8. On the interpretation of time-resolved anisotropic diffraction patterns

    DEFF Research Database (Denmark)

    Lorenz, Ulf; Møller, Klaus Braagaard; Henriksen, Niels Engholm

    2010-01-01

    In this paper, we review existing systematic treatments for the interpretation of anisotropic diffraction patterns from partially aligned symmetric top molecules. Such patterns arise in the context of time-resolved diffraction experiments. We calculate diffraction patterns for ground-state NaI ex......I excited with an ultraviolet laser. The results are interpreted with the help of a qualitative analytic model, and general recommendations on the analysis and interpretation of anisotropic diffraction patterns are given....

  9. Theory of time-resolved inelastic x-ray diffraction

    DEFF Research Database (Denmark)

    Lorenz, Ulf; Møller, Klaus Braagaard; Henriksen, Niels Engholm

    2010-01-01

    Starting from a general theory of time-resolved x-ray scattering, we derive a convenient expression for the diffraction signal based on a careful analysis of the relevant inelastic scattering processes. We demonstrate that the resulting inelastic limit applies to a wider variety of experimental...... conditions than similar, previously derived formulas, and it directly allows the application of selection rules when interpreting diffraction signals. Furthermore, we present a simple extension to systems simultaneously illuminated by x rays and a laser beam....

  10. Time-resolved crystallography using the Hadamard Transform

    Science.gov (United States)

    Yorke, Briony A.; Beddard, Godfrey S.; Owen, Robin L.; Pearson, Arwen R.

    2014-01-01

    A new method for performing time-resolved X-ray crystallographic experiments based on the Hadamard Transform is proposed and demonstrated. The time-resolution is defined by the underlying periodicity of the probe pulse sequence and the signal to noise is greatly improved compared to the fastest experiments depending on a single pulse. This approach is general and equally applicable to any spectroscopic or imaging measurement where the probe can be encoded. PMID:25282611

  11. Broadband Ftmw Spectroscopy of the Urea-Argon and Thiourea-Argon Complexes

    Science.gov (United States)

    Medcraft, Chris; Bittner, Dror M.; Cooper, Graham A.; Mullaney, John C.; Walker, Nick

    2017-06-01

    The rotational spectra complexes of argon-urea, argon-thiourea and water-thiourea have been measured by chirped-pulse Fourier transform microwave spectroscopy from 2-18.5 GHz. The sample was produced via laser vaporisation of a rod containing copper and the organic sample as a stream of argon was passed over the surface and subsequently expanded into the vacuum chamber cooling the sample. Argon was found to bind to π system of the carbonyl bond for both the urea and thiourea complexes.

  12. Coupling between amino acid and water dynamics by broadband dielectric spectroscopy

    Science.gov (United States)

    Saiz, Luciana; Cerveny, Silvina

    2014-05-01

    The dynamics of proline aqueous solution was investigated for water concentrations from 40 to 60 wt% by dielectric spectroscopy (106 - 109 Hz) in the temperature range from 230 to 300 K, where the solutions remain amorphous. We found two relaxation processes, related with the reorientation of proline and water as previously observed in a higher frequency range at room temperature [1]. We found that both dynamics are strongly coupled, as previously observed in hydrated proteins powders, in spite of the fact that a single amino acid is a molecule much simpler than a protein.

  13. Integrated fiber optic incoherent broadband cavity enhanced absorption spectroscopy detector for near-IR absorption measurements of nanoliter samples.

    Science.gov (United States)

    Gomez, Anthony L; Renzi, Ronald F; Fruetel, Julia A; Bambha, Ray P

    2012-05-10

    An integrated fiber-optic sensor is described that uses incoherent broadband cavity enhanced absorption spectroscopy for sensitive detection of aqueous samples in nanoliter volumes. Absorption was measured in a 100 µm gap between the ends of two short segments of multimode graded-index fiber that were integrated into a capillary using a precision machined V-grooved fixture that allowed for passive fiber alignment. The other ends of the fibers were coated with dielectric mirrors to form a 9.5 cm optical resonator. Light from a fiber-coupled superluminescent diode was directly coupled into one end of the cavity, and transmission was measured using a fiber-coupled silicon photodiode. Dilute aqueous solutions of near infrared dye were used to determine the minimum detectable absorption change of 2.4×10(-4) under experimental conditions in which pressure fluctuations limited performance. We also determined that the absolute minimum detectable absorption change would be 1.6×10(-5) for conditions of constant pressure in which absorption measurement is limited by electronic and optical noise. Tolerance requirements for alignment are also presented.

  14. Time resolved IR-LIGS experiments for gas-phase trace detection and temperature measurements

    Energy Technology Data Exchange (ETDEWEB)

    Fantoni, R.; Giorgi, M. [ENEA, Centro Ricerche Frascati, Rome (Italy). Dip. Innovazione; Snels, M. [CNR, Tito Scalo, Potenza (Italy). Istituto per i Materiali Speciali; Latzel, H.

    1997-01-01

    Time resolved Laser Induced Grating Spectroscopy (LIGS) has been performed to detect different gases in mixtures at atmospheric pressure or higher. The possibility of trace detection of minor species and of temperature measurements has been demonstrated for various molecular species either of environmental interest or involved in combustion processes. In view of the application of tracing unburned hydrocarbons in combustion chambers, the coupling of the IR-LIGS technique with imaging detection has been considered and preliminary results obtained in small size ethylene/air flames are shown.

  15. a New Broadband Cavity Enhanced Frequency Comb Spectroscopy Technique Using GHz Vernier Filtering.

    Science.gov (United States)

    Morville, Jérôme; Rutkowski, Lucile; Dobrev, Georgi; Crozet, Patrick

    2015-06-01

    We present a new approach to Cavity Enhanced - Direct Frequency Comb Spectroscopy where the full emission bandwidth of a Titanium:Sapphire laser is exploited at GHz resolution. The technique is based on a low-resolution Vernier filtering obtained with an appreciable -actively stabilized- mismatch between the cavity Free Spectral Range and the laser repetition rate, using a diffraction grating and a split-photodiode. This particular approach provides an immunity to frequency-amplitude noise conversion, reaching an absorption baseline noise in the 10-9 cm-1 range with a cavity finesse of only 3000. Spectra covering 1800 cm-1 (˜ 55 THz) are acquired in recording times of about 1 second, providing an absorption figure of merit of a few 10-11 cm-1/√{Hz}. Initially tested with ambient air, we report progress in using the Vernier frequency comb method with a discharge source of small radicals. Rutkowski et al, Opt. Lett., 39(23)2014

  16. Time-resolved photoinduced Kerr rotation in semiconductor microcavity

    Energy Technology Data Exchange (ETDEWEB)

    Mitsumori, Y.; Kosaka, H. [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira, Aoba-ku, Sendai (Japan); CREST-JST (Japan); Kato, N.; Edamatsu, K. [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira, Aoba-ku, Sendai (Japan); Yamamoto, N.; Akahane, K. [National Institute of Information and Communications Technology, Nukuikita, Koganei-shi, Tokyo (Japan)

    2009-01-15

    We studied photoinduced Kerr effect in cavity polaritons in a semiconductor microcavity by carefully measuring the time-resolved Kerr rotation and ellipticity spectra. The Kerr rotation angle of the microcavity polaritons is a hundred times larger than a conventional single quantum well. A spectral shape analysis of the observed spectra suggests that the photoindeced Kerr effect mainly results from a line broadening of the polarions due to spin-polarized polariton-polariton scattering. Enhancement in oscillator strength also contributes to the large rotation angle. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Development of new devices for time-resolved Raman spectroelectrochemistry

    OpenAIRE

    Ibáñez Martínez, David

    2015-01-01

    La Tesis Doctoral desarrollada por D. David Ibáñez Martínez que lleva por título “Development of new devices for time-resolved Raman spectroelectrochemistry” ha sido realizada en el área de Química Analítica de la Universidad de Burgos y dirigida por los doctores Álvaro Colina Santamaría y Mª Aránzazu Heras Vidaurre. En este trabajo se han desarrollado nuevas celdas y dispositivos espectroelectroquímicos que permiten el estudio tanto de nuevos materiales como de mecanismos químicos de reacció...

  18. Time-resolved SERS for characterizing extracellular vesicles

    Science.gov (United States)

    Rojalin, Tatu; Saari, Heikki; Somersalo, Petter; Laitinen, Saara; Turunen, Mikko; Viitala, Tapani; Wachsmann-Hogiu, Sebastian; Smith, Zachary J.; Yliperttula, Marjo

    2017-02-01

    The aim of this work is to develop a platform for characterizing extracellular vesicles (EV) by using gold-polymer nanopillar SERS arrays simultaneously circumventing the photoluminescence-related disadvantages of Raman with a time-resolved approach. EVs are rich of biochemical information reporting of, for example, diseased state of the biological system. Currently, straightforward, label-free and fast EV characterization methods with low sample consumption are warranted. In this study, SERS spectra of red blood cell and platelet derived EVs were successfully measured and their biochemical contents analyzed using multivariate data analysis techniques. The developed platform could be conveniently used for EV analytics in general.

  19. Time-resolved luminescence from feldspars: New insight into fading

    DEFF Research Database (Denmark)

    Tsukamoto, S.; Denby, P.M.; Murray, A.S.

    2006-01-01

    Time-resolved infrared optically stimulated luminescence (IR-OSL) signals of K- and Na-feldspar samples extracted from sediments were measured in UV, blue and red detection windows, using a fast photon counter and pulsed IR stimulation (lambda = 875 nm). We observe that the relative contribution...... of long lifetime (similar to 20 mu s) components in K-feldspars is greater than that in Na-feldspars at each detection wavelength. From any one feldspar sample, red and blue IR-OSL signals have a greater contribution of long lifetime components than UV IR-OSL. We found this long lifetime component...

  20. Time resolved fluorescence of cow and goat milk powder

    Science.gov (United States)

    Brandao, Mariana P.; de Carvalho dos Anjos, Virgílio; Bell., Maria José V.

    2017-01-01

    Milk powder is an international dairy commodity. Goat and cow milk powders are significant sources of nutrients and the investigation of the authenticity and classification of milk powder is particularly important. The use of time-resolved fluorescence techniques to distinguish chemical composition and structure modifications could assist develop a portable and non-destructive methodology to perform milk powder classification and determine composition. This study goal is to differentiate milk powder samples from cows and goats using fluorescence lifetimes. The samples were excited at 315 nm and the fluorescence intensity decay registered at 468 nm. We observed fluorescence lifetimes of 1.5 ± 0.3, 6.4 ± 0.4 and 18.7 ± 2.5 ns for goat milk powder; and 1.7 ± 0.3, 6.9 ± 0.2 and 29.9 ± 1.6 ns for cow's milk powder. We discriminate goat and cow powder milk by analysis of variance using Fisher's method. In addition, we employed quadratic discriminant analysis to differentiate the milk samples with accuracy of 100%. Our results suggest that time-resolved fluorescence can provide a new method to the analysis of powder milk and its composition.

  1. Time Resolved FTIR Analysis of Tailpipe Exhaust for Several Automobiles

    Science.gov (United States)

    White, Allen R.; Allen, James; Devasher, Rebecca B.

    2011-06-01

    The automotive catalytic converter reduces or eliminates the emission of various chemical species (e.g. CO, hydrocarbons, etc.) that are the products of combustion from automobile exhaust. However, these units are only effective once they have reached operating temperature. The design and placement of catalytic converters has changed in order to reduce both the quantity of emissions and the time that is required for the converter to be effective. In order to compare the effectiveness of catalytic converters, time-resolved measurements were performed on several vehicles, including a 2010 Toyota Prius, a 2010 Honda Fit, a 1994 Honda Civic, and a 1967 Oldsmobile 442 (which is not equipped with a catalytic converter but is used as a baseline). The newer vehicles demonstrate bot a reduced overall level of CO and hydrocarbon emissions but are also effective more quickly than older units. The time-resolved emissions will be discussed along with the impact of catalytic converter design and location on the measured emissions.

  2. Time-resolved fluorescence study of all-trans-retinal

    Science.gov (United States)

    Erez, Yuval; Presiado, Itay; Gepshtein, Rinat; Simkovitch, Ron; Huppert, Dan

    2014-11-01

    UV-vis steady-state and time-resolved emission techniques were employed to study the ultrafast relaxation path of all-trans-retinal. We found that the steady-state emission spectrum consists mainly of two bands that we assign to the allowed transition from the ? state and the forbidden transition from the ?(ππ*) state. The time-resolved emission signal is dependent on the excitation wavelength, and is composed of three decay components. The short-time component of less than 80 fs, irrespective of the solvent, is assigned to the transition from the ? state. The intermediate-time decay component is assigned to the transition from the ?(ππ*) state, depends on the solvent's polarity and not on the existence of hydrogen bonds between the solute and the solvent or the viscosity of the latter. It has a lifetime of ~1 ps in polar solvents, and of 0.6 and 0.4 ps in the non-polar solvents n-octane and cyclohexane, respectively.

  3. Contactless, probeless and non-titrimetric determination of acid-base reactions using broadband acoustic resonance dissolution spectroscopy (BARDS).

    Science.gov (United States)

    Ahmed, M Rizwan; McSweeney, Sean; Krüse, Jacob; Vos, Bastiaan; Fitzpatrick, Dara

    2018-02-12

    pH determination is a routine measurement in scientific laboratories worldwide. Most major advances in pH measurement were made in the 19th and early 20th century. pH measurements are critical for the determination of acid base reactions. This study demonstrates how an acid-base reaction can be monitored without the use of a pH probe, indicator and titres of reagent. The stoichiometric reaction between carbonate and HCl acid yields specific quantities of CO 2 , which causes reproducible changes to the compressibility of the solvent. This in turn slows down the speed of sound in solution which is induced by a magnetic follower gently tapping the inner wall of the vessel. As a consequence the frequencies of the acoustic resonances in the vessel are reduced. This approach is called Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS) which harnesses this phenomenon for many applications. The acid-carbonate experiments have also been validated using H 2 SO 4 acid and using both potassium and sodium counterions for the carbonate. This method can be used to interrogate strong acid-base reactions in a rapid and non-invasive manner using carbonate as the base. The data demonstrate the first example of a reactant also acting as an indicator. The applicability of the method to weak acids has yet to be determined. A novel conclusion from the study is that a person with a well-trained ear is capable of determining the concentration and pH of a strong acid just by listening. This brings pH measurement into the realm of human perception.

  4. A time resolved microfocus XEOL facility at the Diamond Light Source

    Science.gov (United States)

    Mosselmans, J. F. W.; Taylor, R. P.; Quinn, P. D.; Finch, A. A.; Cibin, G.; Gianolio, D.; Sapelkin, A. V.

    2013-03-01

    We have constructed a Time-Resolved X-ray Excited Optical Luminescence (TR-XEOL) detection system at the Microfocus Spectroscopy beamline I18 at the Diamond Light Source. Using the synchrotron in "hybrid bunch mode", the data collection is triggered by the RF clock, and we are able to record XEOL photons with a time resolution of 6.1 ps during the 230 ns gap between the hybrid bunch and the main train of electron bunches. We can detect photons over the range 180-850 nm using a bespoke optical fibre, with X-ray excitation energies between 2 and 20 keV. We have used the system to study a range of feldspars. The detector is portable and has also been used on beamline B18 to collect Optically Determined X-ray Absorption Spectroscopy (OD-XAS) in QEXAFS mode.

  5. Application of a broadband blue laser diode to trace NO2 detection using off-beam quartz-enhanced photoacoustic spectroscopy.

    Science.gov (United States)

    Yi, Hongming; Liu, Kun; Chen, Weidong; Tan, Tu; Wang, Lei; Gao, Xiaoming

    2011-02-15

    We applied for the first time, to our knowledge, broadband off-beam quartz-enhanced photoacoustic spectroscopy (BB-OB-QEPAS) to trace NO2 detection using a broadband blue laser diode centered at 450 nm. A detection limit of 18 ppbv (parts in 10(9) by volume) for NO2 in N2 at atmospheric pressure was achieved with an average laser power of 7 mW at a 1 s integration time, which corresponds to a 1 σ normalized noise equivalent absorption coefficient of 4.1×10(-9)  cm(-1) W=Hz(1=2). An Allan variance analysis was performed to investigate the long-term stability of the BB-OB-QEPAS-based NO2 sensor.

  6. Thyroid tissue constituents characterization and application to in vivo studies by broadband (600-1200 nm) diffuse optical spectroscopy

    Science.gov (United States)

    Konugolu Venkata Sekar, Sanathana; Farina, Andrea; dalla Mora, Alberto; Taroni, Paola; Lindner, Claus; Mora, Mireia; Farzam, Parisa; Pagliazzi, Marco; Squarcia, Mattia; Halperin, Irene; Hanzu, Felicia A.; Dehghani, Hamid; Durduran, Turgut; Pifferi, Antonio

    2017-07-01

    We present the first broadband (600-1100 nm) diffuse optical characterization of thyroglobulin and tyrosine, which are thyroid-specific tissue constituents. In-vivo measurements at the thyroid region enabled their quantification for functional and diagnostic applications.

  7. Photon-Counting Arrays for Time-Resolved Imaging

    Directory of Open Access Journals (Sweden)

    I. Michel Antolovic

    2016-06-01

    Full Text Available The paper presents a camera comprising 512 × 128 pixels capable of single-photon detection and gating with a maximum frame rate of 156 kfps. The photon capture is performed through a gated single-photon avalanche diode that generates a digital pulse upon photon detection and through a digital one-bit counter. Gray levels are obtained through multiple counting and accumulation, while time-resolved imaging is achieved through a 4-ns gating window controlled with subnanosecond accuracy by a field-programmable gate array. The sensor, which is equipped with microlenses to enhance its effective fill factor, was electro-optically characterized in terms of sensitivity and uniformity. Several examples of capture of fast events are shown to demonstrate the suitability of the approach.

  8. FXR LIA Optimization - Time-resolved OTR Emittance Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, J; Ong, M; Wargo, P; LeSage, G

    2005-07-21

    The Flash X-Ray Radiography (FXR) facility at Lawrence Livermore National Laboratory utilizes a high current, long pulse linear induction accelerator to produce high doses of x-ray radiation. Accurate characterization of the transverse beam emittance is required in order to facilitate accelerator modeling and tuning efforts and, ultimately, to optimize the final focus spot size, yielding higher resolution radiographs. In addition to conventional magnet scan, pepper-pot, and multiple screen techniques, optical transition radiation (OTR) has been proven as a useful emittance measurement diagnostic and is particularly well suited to the FXR accelerator. We shall discuss the time-resolved emittance characterization of an induction linac electron beam using OTR, and we will present our experimental apparatus and analysis software. We shall also develop the theoretical background of beam emittance and transition radiation.

  9. Spectral characteristics of time resolved magnonic spin Seebeck effect

    Energy Technology Data Exchange (ETDEWEB)

    Etesami, S. R.; Chotorlishvili, L.; Berakdar, J. [Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Germany)

    2015-09-28

    Spin Seebeck effect (SSE) holds promise for new spintronic devices with low-energy consumption. The underlying physics, essential for a further progress, is yet to be fully clarified. This study of the time resolved longitudinal SSE in the magnetic insulator yttrium iron garnet concludes that a substantial contribution to the spin current stems from small wave-vector subthermal exchange magnons. Our finding is in line with the recent experiment by S. R. Boona and J. P. Heremans [Phys. Rev. B 90, 064421 (2014)]. Technically, the spin-current dynamics is treated based on the Landau-Lifshitz-Gilbert equation also including magnons back-action on thermal bath, while the formation of the time dependent thermal gradient is described self-consistently via the heat equation coupled to the magnetization dynamics.

  10. Time resolved optical Bloch oscillations in porous silicon superlattice structures

    Energy Technology Data Exchange (ETDEWEB)

    Ghulinyan, Mher; Gaburro, Zeno; Pavesi, Lorenzo [Department of Physics, University of Trento and INFM, 38050 Povo (Trento) (Italy); Oton, Claudio J. [Department of Physics, University of Trento and INFM, 38050 Povo (Trento) (Italy); Department of Fundamental Physics, University of La Laguna, La Laguna 38204 Tenerife (Spain); Sapienza, Riccardo; Costantino, Paola; Wiersma, Diederik S. [European Laboratory for Nonlinear Spectroscopy and INFM, 50019 Sesto Fiorentino (Florence) (Italy)

    2005-06-01

    We report on the observation of time resolved Bloch oscillations of light waves in optical superlattice structures. The structures are series of coupled microcavities, which are grown in porous silicon with high control of optical parameters. A controlled linear gradient of refractive index along the growth direction was maintained to tilt the photonic band gap of the superlattice. This is in perfect analogy to the tilted electronic miniband structure of a semiconductor in an electric field. In this way an optical Wannier-Stark ladder of equidistant optical modes was formed. Their frequency separation defines the period of the photon Bloch oscillations. The experimental results are in excellent agreement with transfer matrix calculations. The observed phenomenon is the optical counterpart of the well known electronic Bloch oscillations. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. STROBE-X: X-ray timing and spectroscopy on dynamical timescales from microseconds to years

    Directory of Open Access Journals (Sweden)

    Colleen A. Wilson-Hodge

    Full Text Available The Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X probes strong gravity for stellar mass to supermassive black holes and ultradense matter with unprecedented effective area, high time-resolution, and good spectral resolution, while providing a powerful time-domain X-ray observatory. Keywords: Missions, X-ray timing, X-ray spectroscopy, Compact objects

  12. Time-resolved fluorescence studies of nucleotide flipping by restriction enzymes.

    Science.gov (United States)

    Neely, Robert K; Tamulaitis, Gintautas; Chen, Kai; Kubala, Marta; Siksnys, Virginijus; Jones, Anita C

    2009-11-01

    Restriction enzymes Ecl18kI, PspGI and EcoRII-C, specific for interrupted 5-bp target sequences, flip the central base pair of these sequences into their protein pockets to facilitate sequence recognition and adjust the DNA cleavage pattern. We have used time-resolved fluorescence spectroscopy of 2-aminopurine-labelled DNA in complex with each of these enzymes in solution to explore the nucleotide flipping mechanism and to obtain a detailed picture of the molecular environment of the extrahelical bases. We also report the first study of the 7-bp cutter, PfoI, whose recognition sequence (T/CCNGGA) overlaps with that of the Ecl18kI-type enzymes, and for which the crystal structure is unknown. The time-resolved fluorescence experiments reveal that PfoI also uses base flipping as part of its DNA recognition mechanism and that the extrahelical bases are captured by PfoI in binding pockets whose structures are quite different to those of the structurally characterized enzymes Ecl18kI, PspGI and EcoRII-C. The fluorescence decay parameters of all the enzyme-DNA complexes are interpreted to provide insight into the mechanisms used by these four restriction enzymes to flip and recognize bases and the relationship between nucleotide flipping and DNA cleavage.

  13. Time-Resolved WAXD and FTIR Studies on Imidization-Induced Molecular Ordering in Polyimide Precursors

    Science.gov (United States)

    Ree, Moonhor; Shin, Tae Joo; Lee, Byeongdu; Wang, Xiaodong; Youn, Hwa Shik; Lee, Ki-Bong

    2000-03-01

    In general, aromatic polyimides are not melt-processable and not soluble in common solvents so that they are always processed in their soluble precursor forms and followed by imidization. Most poyimide precursors are poorly ordered in the solid state but molecular ordering develops during imidization. In this study, the imidization-induced molecular ordering in precursors of PMDA-ODA polyimide was examined in detail by time-resolved wide-angle X-ray diffraction using synchrotron radiation source at Pohang Accelerator Laboratory while the degree of imidization was monitored by time-resolved FT-IR spectroscopy. The imidization was conducted isothermally and non-isothermally over 20-400 C under nitrogen atmosphere. The imidization behavior was dependent on the precursor types: polyamic acid started to imidize at 120 C while polyamic diethyl ester began to imidize at 190 C. The molecular ordering was strongly dependent on the degree of imidization: the molecular ordering was found to be developed as the imidization began. The molecular ordering behavior will be discussed in detail with considering precursor types and their imidization kinetics. [This study was supported in part by the Ministry of Industry and the Ministry of Science & Technology (G7 Project Program) and by POSCO].

  14. A table-top femtosecond time-resolved soft x-ray transient absorption spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Leone, Stephen; Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E.; Leone, Stephen R.

    2008-05-21

    A laser-based, table-top instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a home-built soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray CCD camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterization of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.

  15. Applications of a table-top time-resolved luminescence spectrometer with nanosecond soft X-ray pulse excitation

    Czech Academy of Sciences Publication Activity Database

    Brůža, P.; Pánek, D.; Fidler, V.; Benedikt, P.; Čuba, V.; Gbur, T.; Boháček, Pavel; Nikl, Martin

    2014-01-01

    Roč. 61, č. 1 (2014), s. 448-451 ISSN 0018-9499 R&D Projects: GA ČR GA13-09876S Institutional support: RVO:68378271 Keywords : LiCaAlF 6 * luminescence * scintillators * soft x-ray * SrHfO 3 * time-resolved spectroscopy * ZnO :Ga Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.283, year: 2014

  16. Spread spectrum time-resolved diffuse optical measurement system for enhanced sensitivity in detecting human brain activity

    Science.gov (United States)

    Mehta, Kalpesh; Hasnain, Ali; Zhou, Xiaowei; Luo, Jianwen; Penney, Trevor B.; Chen, Nanguang

    2017-04-01

    Diffuse optical spectroscopy (DOS) and imaging methods have been widely applied to noninvasive detection of brain activity. We have designed and implemented a low cost, portable, real-time one-channel time-resolved DOS system for neuroscience studies. Phantom experiments were carried out to test the performance of the system. We further conducted preliminary human experiments and demonstrated that enhanced sensitivity in detecting neural activity in the cortex could be achieved by the use of late arriving photons.

  17. Time resolved multiphoton excited fluorescence probes in model membranes

    CERN Document Server

    Bai, Y

    2000-01-01

    Using the time-correlated single-photon counting technique, this thesis reports on a time-resolved fluorescence study of several fluorescent probes successfully employed in membrane research. Concentration and temperature effects on fluorescence anisotropy parameters are demonstrated by DPH, p-terphenyl, alpha-NPO and PPO in DPPC lipid bilayers. Fluorescence anisotropy has shown that trans-stilbene and Rhd 800 have a two-site location in membranes. Multiphoton induced fluorescence of DPH, p-terphenyl, alpha-NPO and v-biphenyl in liposomes was measured using 800nm excitation with a femtosecond Ti:Sapphire laser. P-terphenyl, alpha-NPO and v-biphenyl are new probes for membranes. Comparison of one and multiphoton excitation results has demonstrated higher initial anisotropy with multiphoton excitation than with one-photon excitation. The rotational times were identical for one and multiphoton excitation, indicating the absence of significant local heating or sample perturbation. Excimer formation of alpha-NPO w...

  18. Time resolved strain dependent morphological study of electrically conducting nanocomposites

    Science.gov (United States)

    Khan, Imran; Mitchell, Geoffrey; Mateus, Artur; Kamma-Lorger, Christina S.

    2015-10-01

    An efficient and reliable method is introduced to understand the network behaviour of nano-fillers in a polymeric matrix under uniaxial strain coupled with small angle x-ray scattering measurements. The nanoparticles (carbon nanotubes) are conductive and the particles form a percolating network that becomes apparent source of electrical conduction and consequently the samples behave as a bulk conductor. Polyurethane based nanocomposites containing 2% w/w multiwall carbon nanotubes are studied. The electrical conductivity of the nanocomposite was (3.28×10-5s/m).The sample was able to be extended to an extension ratio of 1.7 before fracture. A slight variation in the electrical conductivity is observed under uniaxial strain which we attribute to the disturbance of conductive pathways. Further, this work is coupled with in- situ time resolved small angle x-ray scattering measurements using a synchrotron beam line to enable its measurements to be made during the deformation cycle. We use a multiscale structure to model the small angle x-ray data. The results of the analysis are interpreted as the presence of aggregates which would also go some way towards understanding why there is no alignment of the carbon nanotubes.

  19. Quantitative analysis of time-resolved microwave conductivity data

    Energy Technology Data Exchange (ETDEWEB)

    Reid, Obadiah G.; Moore, David T.; Li, Zhen; Zhao, Dewei; Yan, Yanfa; Zhu, Kai; Rumbles, Garry

    2017-11-10

    Flash-photolysis time-resolved microwave conductivity (fp-TRMC) is a versatile, highly sensitive technique for studying the complex photoconductivity of solution, solid, and gas-phase samples. The purpose of this paper is to provide a standard reference work for experimentalists interested in using microwave conductivity methods to study functional electronic materials, describing how to conduct and calibrate these experiments in order to obtain quantitative results. The main focus of the paper is on calculating the calibration factor, K, which is used to connect the measured change in microwave power absorption to the conductance of the sample. We describe the standard analytical formulae that have been used in the past, and compare them to numerical simulations. This comparison shows that the most widely used analytical analysis of fp-TRMC data systematically under-estimates the transient conductivity by ~60%. We suggest a more accurate semi-empirical way of calibrating these experiments. However, we emphasize that the full numerical calculation is necessary to quantify both transient and steady-state conductance for arbitrary sample properties and geometry.

  20. Time-resolved biophysical approaches to nucleocytoplasmic transport

    Directory of Open Access Journals (Sweden)

    Francesco Cardarelli

    2017-01-01

    Full Text Available Molecules are continuously shuttling across the nuclear envelope barrier that separates the nucleus from the cytoplasm. Instead of being just a barrier to diffusion, the nuclear envelope is rather a complex filter that provides eukaryotes with an elaborate spatiotemporal regulation of fundamental molecular processes, such as gene expression and protein translation. Given the highly dynamic nature of nucleocytoplasmic transport, during the past few decades large efforts were devoted to the development and application of time resolved, fluorescence-based, biophysical methods to capture the details of molecular motion across the nuclear envelope. These methods are here divided into three major classes, according to the differences in the way they report on the molecular process of nucleocytoplasmic transport. In detail, the first class encompasses those methods based on the perturbation of the fluorescence signal, also known as ensemble-averaging methods, which average the behavior of many molecules (across many pores. The second class comprises those methods based on the localization of single fluorescently-labelled molecules and tracking of their position in space and time, potentially across single pores. Finally, the third class encompasses methods based on the statistical analysis of spontaneous fluorescence fluctuations out of the equilibrium or stationary state of the system. In this case, the behavior of single molecules is probed in presence of many similarly-labelled molecules, without dwelling on any of them. Here these three classes, with their respective pros and cons as well as their main applications to nucleocytoplasmic shuttling will be briefly reviewed and discussed.

  1. Monitoring tissue metabolism via time-resolved laser fluorescence

    Science.gov (United States)

    Maerz, Holger K.; Buchholz, Rainer; Emmrich, Frank; Fink, Frank; Geddes, Clive L.; Pfeifer, Lutz; Raabe, Ferdinand; Marx, Uwe

    1999-05-01

    Most assays for drug screening are monitoring the metabolism of cells by detecting the NADH content, which symbolize its metabolic activity, indirectly. Nowadays, the performance of a LASER enables us to monitor the metabolic state of mammalian cells directly and on-line by using time-resolved autofluorescence detection. Therefore, we developed in combination with tissue engineering, an assay for monitoring minor toxic effects of volatile organic compounds (VOC), which are accused of inducing Sick Building Syndrome (SBS). Furthermore, we used the Laserfluoroscope (LF) for pharmacological studies on human bone marrow in vitro with special interest in chemotherapy simulation. In cancer research and therapy, the effect of chemostatica in vitro in the so-called oncobiogram is being tested; up to now without great success. However, it showed among other things that tissue structure plays a vital role. Consequently, we succeeded in simulating a chemotherapy in vitro on human bone marrow. Furthermore, after tumor ektomy we were able to distinguish between tumoric and its surrounding healthy tissue by using the LF. With its sensitive detection of metabolic changes in tissues the LF enables a wide range of applications in biotechnology, e.g. for quality control in artificial organ engineering or biocompatability testing.

  2. Fielding of a Time-Resolved Tomographic Diagnostic

    Energy Technology Data Exchange (ETDEWEB)

    Daniel Frayer, Brian Cox, Wendi Dreesen, Douglas Johnson, Mike Jones, Morris Kaufman

    2008-09-11

    A diagnostic instrument has been developed for the acquisition of high-speed time-resolved images at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility at Los Alamos National Laboratory. The instrument was developed in order to create time histories of the electron beam. Four discrete optical subsystems view Cerenkov light generated at an x-ray target inside of a vacuum envelope. Each system employs cylindrical optics to image light in one direction and collapse light in the orthogonal direction. Each of the four systems images and collapses in unique axes, thereby capturing unique information. Light along the imaging axis is relayed via optical fiber to streak cameras. A computer is used to reconstruct the original image from the four optically collapsed images. Due to DARHT’s adverse environment, the instrument can be operated remotely to adjust optical parameters and contains a subsystem for remote calibration. The instrument was deployed and calibrated, and has been used to capture and reconstruct images. Matters of alignment, calibration, control, resolution, and adverse conditions will be discussed.

  3. Quantitative analysis of time-resolved microwave conductivity data

    Science.gov (United States)

    Reid, Obadiah G.; Moore, David T.; Li, Zhen; Zhao, Dewei; Yan, Yanfa; Zhu, Kai; Rumbles, Garry

    2017-12-01

    Flash-photolysis time-resolved microwave conductivity (fp-TRMC) is a versatile, highly sensitive technique for studying the complex photoconductivity of solution, solid, and gas-phase samples. The purpose of this paper is to provide a standard reference work for experimentalists interested in using microwave conductivity methods to study functional electronic materials, describing how to conduct and calibrate these experiments in order to obtain quantitative results. The main focus of the paper is on calculating the calibration factor, K, which is used to connect the measured change in microwave power absorption to the conductance of the sample. We describe the standard analytical formulae that have been used in the past, and compare them to numerical simulations. This comparison shows that the most widely used analytical analysis of fp-TRMC data systematically under-estimates the transient conductivity by ~60%. We suggest a more accurate semi-empirical way of calibrating these experiments. However, we emphasize that the full numerical calculation is necessary to quantify both transient and steady-state conductance for arbitrary sample properties and geometry.

  4. Time-resolved multiphoton imaging of basal cell carcinoma

    Science.gov (United States)

    Cicchi, R.; Sestini, S.; De Giorgi, V.; Stambouli, D.; Carli, P.; Massi, D.; Pavone, F. S.

    2007-02-01

    We investigated human cutaneous basal cell carcinoma ex-vivo samples by combined time resolved two photon intrinsic fluorescence and second harmonic generation microscopy. Morphological and spectroscopic differences were found between malignant skin and corresponding healthy skin tissues. In comparison with normal healthy skin, cancer tissue showed a different morphology and a mean fluorescence lifetime distribution slightly shifted towards higher values. Topical application of delta-aminolevulinic acid to the lesion four hours before excision resulted in an enhancement of the fluorescence signal arising from malignant tissue, due to the accumulation of protoporphyrines inside tumor cells. Contrast enhancement was prevalent at tumor borders by both two photon fluorescence microscopy and fluorescence lifetime imaging. Fluorescence-based images showed a good correlation with conventional histopathological analysis, thereby supporting the diagnostic accuracy of this novel method. Combined morphological and lifetime analysis in the study of ex-vivo skin samples discriminated benign from malignant tissues, thus offering a reliable, non-invasive tool for the in-vivo analysis of inflammatory and neoplastic skin lesions.

  5. Time-resolved pump-probe experiments at the LCLS

    Energy Technology Data Exchange (ETDEWEB)

    Glownia, James; /SLAC /Stanford U., Appl. Phys. Dept.; Cryan, J.; /SLAC /Stanford U., Phys. Dept.; Andreasson, J.; /Uppsala U.; Belkacem, A.; /LBNL, Berkeley; Berrah, N.; /Western Michigan U.; Blaga, C.L.; /Ohio State U.; Bostedt, C.; Bozek, J.; /SLAC; DiMauro, L.F.; /Ohio State U.; Fang, L.; /Western Michigan U.; Frisch, J.; /SLAC; Gessner, O.; /LBNL; Guhr, M.; /SLAC; Hajdu, J.; /Uppsala U.; Hertlein, M.P.; /LBNL; Hoener, M.; /Western Michigan U. /LBNL; Huang, G.; Kornilov, O.; /LBNL; Marangos, J.P.; /Imperial Coll., London; March, A.M.; /Argonne; McFarland, B.K.; /SLAC /Stanford U., Phys. Dept. /SLAC /IRAMIS, Saclay /Stanford U., Phys. Dept. /Georgia Tech /Argonne /Kansas State U. /SLAC /Stanford U., Phys. Dept. /SLAC /Stanford U., Appl. Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC /LBNL /Argonne /SLAC /SLAC /Stanford U., Appl. Phys. Dept. /Stanford U., Phys. Dept.

    2011-08-12

    The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs.

  6. Revisiting the photophysics of 9-fluorenone: Ultrafast time-resolved fluorescence and theoretical studies

    Science.gov (United States)

    Chang, Chih-Wei; Sølling, Theis I.; Diau, Eric Wei-Guang

    2017-10-01

    Ultrafast intersystem crossing dynamics of fluorenone in gas and condensed phases were investigated by time-resolved mass spectrometry and fluorescence up-conversion spectroscopy. The former shows the ultrafast Franck-Condon relaxation and the internal conversion dynamics of isolated fluorenone in the gas phase. The latter reveals that the vibrational relaxation time is 2.2 ps and a 110 ps fluorescence lifetime of fluorenone in hexane. The fluorescence lifetime in acetonitrile and dimethylsulfoxide is 16 ns and 15.1 ns, respectively. The potential energy surface along the Cdbnd O out of plane bending motion shows that this coordinate is important for ISC in both polar and non-polar solvents.

  7. Glucose Sensing by Time-Resolved Fluorescence of Sol-Gel Immobilized Glucose Oxidase

    Science.gov (United States)

    Esposito, Rosario; Ventura, Bartolomeo Della; De Nicola, Sergio; Altucci, Carlo; Velotta, Raffaele; Mita, Damiano Gustavo; Lepore, Maria

    2011-01-01

    A monolithic silica gel matrix with entrapped glucose oxidase (GOD) was constructed as a bioactive element in an optical biosensor for glucose determination. Intrinsic fluorescence of free and immobilised GOD was investigated in the visible range in presence of different glucose concentrations by time-resolved spectroscopy with time-correlated single-photon counting detector. A three-exponential model was used for analysing the fluorescence transients. Fractional intensities and mean lifetime were shown to be sensitive to the enzymatic reaction and were used for obtaining calibration curve for glucose concentration determination. The sensing system proposed achieved high resolution (up to 0.17 mM) glucose determination with a detection range from 0.4 mM to 5 mM. PMID:22163807

  8. Glucose Sensing by Time-Resolved Fluorescence of Sol-Gel Immobilized Glucose Oxidase

    Directory of Open Access Journals (Sweden)

    Maria Lepore

    2011-03-01

    Full Text Available A monolithic silica gel matrix with entrapped glucose oxidase (GOD was constructed as a bioactive element in an optical biosensor for glucose determination. Intrinsic fluorescence of free and immobilised GOD was investigated in the visible range in presence of different glucose concentrations by time-resolved spectroscopy with time-correlated single-photon counting detector. A three-exponential model was used for analysing the fluorescence transients. Fractional intensities and mean lifetime were shown to be sensitive to the enzymatic reaction and were used for obtaining calibration curve for glucose concentration determination. The sensing system proposed achieved high resolution (up to 0:17 mM glucose determination with a detection range from 0:4 mM to 5 mM.

  9. Time-resolved ARPES at LACUS: Band Structure and Ultrafast Electron Dynamics of Solids.

    Science.gov (United States)

    Crepaldi, Alberto; Roth, Silvan; Gatti, Gianmarco; Arrell, Christopher A; Ojeda, José; van Mourik, Frank; Bugnon, Philippe; Magrez, Arnaud; Berger, Helmuth; Chergui, Majed; Grioni, Marco

    2017-05-31

    The manipulation of the electronic properties of solids by light is an exciting goal, which requires knowledge of the electronic structure with energy, momentum and temporal resolution. Time- and angle-resolved photoemission spectroscopy (tr-ARPES) is the most direct probe of the effects of an optical excitation on the band structure of a material. In particular, tr-ARPES in the extreme ultraviolet (VUV) range gives access to the ultrafast dynamics over the entire Brillouin zone. VUV tr-ARPES experiments can now be performed at the ASTRA (ARPES Spectrometer for Time-Resolved Applications) end station of Harmonium, at LACUS. Its capabilities are illustrated by measurements of the ultrafast electronic response of ZrSiTe, a novel topological semimetal characterized by linearly dispersing states located at the Brillouin zone boundary.

  10. Time-resolved studies at PETRA III with a highly repetitive synchronized laser system

    Energy Technology Data Exchange (ETDEWEB)

    Schlie, Mortiz

    2013-09-15

    Atomic and molecular processes can nowadays be directly followed in the time domain. This is a core technique for a better understanding of the involved fundamental physics, thus auguring new applications in the future as well. Usually the so-called pump-probe technique making use of two synchronized ultrashort light pulses is utilized to obtain this time-resolved data. In this work, the development and characterization of a synchronization system enabling such pump-probe studies at the storage ring PETRA III in combination with an external, then synchronized fs-laser system is described. The synchronization is based on an extended PLL approach with three interconnected feedback loops allowing to monitor short-time losses of the lock and thus prevent them. This way, the jitter between the laser PHAROS and the PETRA III reference signal is reduced to {sigma} <5 ps. Thus the system allows to conduct experiments at a repetition rate of 130 kHz with a temporal resolution limited only by the X-ray pulse length. A major emphasis in the fundamental introductory chapters is an intuitive explanation of the basic principles of phase locked loops and the different aspects of phase noise to allow a deeper understanding of the synchronization. Furthermore, first pump-probe experiments conducted at different beamlines at PETRA III are presented, demonstrating the usability of the laser system in a scientific environment as well. In first characterizing experiments the pulse duration of PETRA III X-ray pulses has been measured to be 90 ps FWHM. In particular, there have been time resolved X-ray absorption spectroscopy experiments on Gaq3 and Znq2 conducted at beamline P11. First results show dynamics of the electronic excitation on the timescale of a few hundred pico seconds up to a few nano seconds and provide a basic understanding for further research on those molecules. For Gaq3 this data is analyzed in detail and compared with visible fluorescence measurements suggesting at

  11. A robust noise reduction technique for time resolved CT.

    Science.gov (United States)

    Li, Zhoubo; Yu, Lifeng; Leng, Shuai; Williamson, Eric E; Kotsenas, Amy L; DeLone, David R; Manduca, Armando; McCollough, Cynthia H

    2016-01-01

    To develop a noise reduction method for time resolved CT data, especially those with significant patient motion. PArtial TEmporal Nonlocal (PATEN) means is a technique that uses the redundant information in time-resolved CT data to achieve noise reduction. In this method, partial temporal profiles are used to determine the similarity (or weight) between pixels, and the similarity search makes use of both spatial and temporal information, providing robustness to patient motion. The performance of the PATEN filter was qualitatively and quantitatively evaluated with nine cardiac CT patient data sets and five CT brain perfusion patient data sets. In cardiac CT, PATEN was applied to reduce noise primarily in the reduced-dose phases created with electrocardiographic (ECG) pulsing. CT number accuracy and noise reduction were evaluated in both full-dose phases and reduced-dose phases between filtered backprojection images and PATEN filtered images. In CT brain perfusion, simulated quarter dose data were obtained by adding noise to the raw data of a routine dose scan. PATEN was applied to the simulated low-dose images. Image noise, time-intensity profile accuracy, and perfusion parameter maps were compared among low-dose, low-dose+PATEN filter, and full-dose images. The noise reduction performance of PATEN was compared to a previously proposed noise reduction method, time-intensity profile similarity (TIPS) bilateral filtering. In 4D cardiac CT, after PATEN filtering, the image noise in the reduced-dose phases was greatly reduced, making anatomical structures easier to identify. The mean decreases in noise values between the original and PATEN images were 11.0% and 53.8% for the full and reduced-dose phases of the cardiac cycle, respectively. TIPS could not achieve effective noise reduction. In CT brain perfusion, PATEN achieved a 55.8%-66.3% decrease in image noise in the low-dose images. The contrast to noise ratio in the axial images was increased and was comparable to

  12. Microsecond Time-Resolved Circular Dichroism of Rhodopsin Photointermediates†

    Science.gov (United States)

    Thomas, Yiren Gu; Szundi, Istvan; Lewis, James W.; Kliger, David S.

    2009-01-01

    Time-resolved circular dichroism measurements, over a spectral range from 300 to 700 nm, were made at delays of 5, 100 and 500 μs after room temperature photoexcitation of bovine rhodopsin in lauryl maltoside suspension. The purpose was to provide more structural information about intermediate states in the activation of rhodopsin and other G protein-coupled receptors. In particular, information was sought about photointermediates that are isochromic or nearly isochromic in their unpolarized absorbance. The circular dichroism spectrum of lumirhodopsin, obtained after correcting the 5 μs difference CD data for the rhodopsin bleached, was in reasonable agreement with the lumirhodopsin CD spectrum obtained previously by thermal trapping at -76°C. Similarly, the metarhodopsin II spectrum obtained at 500 μs delay was also in agreement with the results of previous work on the temperature trapped form of metarhodopsin II. However, the CD of the mixture formed at 100 μs delay after photoexcitation, whose only visible absorbing component is lumirhodopsin, could not be accounted for near 480 nm in terms of the initially formed, 5 μs lumirhodopsin CD spectrum. Thus, the CD spectrum of lumirhodopsin changes on the time scale from 5 to 100 μs, showing reduced rotational strength in its visible band, possibly associated with either a process responsible for a small spectral shift that occurs in the lumirhodopsin absorbance spectrum at earlier times or the Schiff base deprotonation-reprotonation which occurs during equilibration of lumirhodopsin with the Meta I380 photointermediate. Either explanation suggests a chromophore conformation change closely associated with deprotonation which could be the earliest direct trigger of activation. PMID:19905009

  13. Time-resolved diagnostic of an impulse discharge in variable pressure air

    Science.gov (United States)

    Robledo-Martinez, A.; Sobral, H.; Ruiz-Meza, A.

    2008-09-01

    The effect of gas pressure on the characteristics of a short-gap lightning discharge in air was investigated. For the tests, 70 ns front lightning pulses were applied to a short (11 cm) point-plane gap under variable pressure. The diagnostics employed included electric current and field measurements, spectroscopy in the visible and fast-frame photography. We found that the pressure has a clear effect on the electric field at the plane. For low pressures, the high fields measured (~7 kV cm-1) are comparable to the Laplacian field, indicating that very little ionization takes place in the gap at this pressure; at higher pressures the space charge contributes substantially to the field magnitude. The effect of pressure on the current pulse was, in contrast, minimal; its peak amplitude and shape remained largely unaffected by pressure. Time-resolved spectroscopy allowed the determination of the instantaneous electron density and temperature to be made; the latter, for example, was found to reach 33 000 K at t ~ 1 µs for most of the pressures employed. Using the measured temperature and radius we made estimations of the arc's resistance. We found that the Spitzer resistivity model gives values of resistance that are compatible with the experimental data obtained.

  14. Time resolved FTIR study of the catalytic CO oxidation under periodic variation of the reactant concentration

    Energy Technology Data Exchange (ETDEWEB)

    Kritzenberger, J.; Wokaun, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Oxidation of CO over palladium/zirconia catalyst obtained from an amorphous Pd{sub 25}Zr{sub 75} precursor was investigated by time resolved FTIR spectroscopy. Sine wave shaped modulation of the reactant concentration, i.e. variation of CO or O{sub 2} partial pressure, was used to induce variations of the IR signals of product (CO{sub 2}) and unconverted reactant (CO), which were detected in a multi-pass absorption cell. The phase shift {phi} between external perturbation and variation of the CO{sub 2} signal was examined in dependence on temperature (100{sup o}C{<=}T{<=}350{sup o}C) and modulation frequency (1.39x10{sup -4}Hz{<=}{omega}{<=}6.67x10{sup -2}Hz). From the phase shift values, a simple Eley-Rideal mechanism is excluded, and the rate limiting step of the Langmuir-Hinshelwood mechanism for the CO oxidation may be identified. Adsorption and possible surface movement of CO to the actual reaction site determine the rate of the CO oxidation on the palladium/zirconia catalyst used in our study. The introduction of an external perturbation is a first step towards the application of two-dimensional infrared spectroscopy to heterogeneous catalyzed reactions. (author) 3 figs., 4 refs.

  15. Ultrafast broadband laser spectroscopy reveals energy and charge transfer in novel donor-acceptor triads for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Roland, T; Ramirez, G Hernandez; Leonard, J; Mery, S; Haacke, S, E-mail: stefan.haacke@ipcms.u-strasbg.fr [Institut de Physique et Chimie des Materiaux de Strasbourg, Strasbourg University - CNRS UMR 7504, F-67034 Strasbourg (France)

    2011-02-01

    Triggered by the quest for new organic materials and micro-structures for photovoltaic applications, a novel class of donor-acceptor-donor (DAD) triads extended with siloxane chains has been synthesized in our labs. Because of the siloxane chains, the molecules self-organize into a smectic liquid crystal phase, resulting in a stacking of the DAD cores.We report here a preliminary study of the ultrafast dynamics of energy and charge transfer studied by femtosecond broadband transient absorption experiments on isolated triads in chloroform.

  16. Detection of H2S, SO2 and NO2 in CO2 at pressures ranging from 1-40 bar by using broadband absorption spectroscopy in the UV/VIS range

    NARCIS (Netherlands)

    Gersen, Sander; van Essen, Vincent; Visser, Pieter; Ahmad, Mohammad; Mokhov, Anatoli; Sepman, Alexey; Alberts, Ramon; Douma, Arno; Levinsky, Howard

    2014-01-01

    This paper presents a methodology to quantitatively measure H2S, SO2 and NO2 fractions in gaseous CO2 by using broadband absorption spectroscopy at 1 and 40 bar. The mole fractions of binary- and 3-component mixtures of H2S, SO2 and NO2 in CO2 with known fractions ranging from 35-250 ppm are

  17. Time-resolved X-ray absorption spectroscopy for the study of solid state reactions: synthesis of nanocrystalline barium titanate and thermal decomposition of ammonium hexachlorometallate compounds; Zeitaufgeloeste Roentgenabsorptionspektroskopie zur Untersuchung von Festkoerperreaktionen: Synthese von nanokristallinem Bariumtitanat und thermische Zersetzung von Ammoniumhexachlorometallat-Verbindungen

    Energy Technology Data Exchange (ETDEWEB)

    Rumpf, H.

    2001-07-01

    This report presents investigations on the mechanism of two different types of solid-state reactions: At first, barium titanate nanopowders were prepared through a combined polymerization and pyrolysis of a metallo-organic precursor. The mean particle size d{sub m} could be adjusted by choosing appropriate reaction temperatures and tempering atmospheres. In the present in situ study of this particular solid-phase reaction, X-ray absorption near edge structure (XANES) spectroscopy at the Ti K and Ba L{sub 3}-edges was applied in the preparation route of BaTiO{sub 3} nanopowders. A pronounced distortion of the lattice symmetry was found to occur in very fine BaTiO{sub 3} nanopowders (d{sub m} < 20 nm). Secondly, in situ XANES investigations were carried out at the Cl K, Pd L{sub 3}, Rh L{sub 3}, and Pt L{sub 3}-edges to study the mechanism of the thermal decomposition of ammonium hexachlorometallates. The results exceed structural information obtained by in situ X-ray diffraction methods and thermal analysis. Feff8 multiple scattering simulations have been carried out to disclose new intermediate phases of unknown reference compounds. (orig.)

  18. Time-Resolved Dynamics of Shallow Acceptor Transitions in Silicon

    Directory of Open Access Journals (Sweden)

    N. Q. Vinh

    2013-03-01

    Full Text Available Shallow group-V donors in silicon may be thought of as hydrogenlike, and shallow acceptors are similarly described by effective-mass theory with similar energy scales, which implies that donor and acceptor excitations should be just as long-lived. Yet, spectral widths of acceptors are considerably wider. We have measured the orbital dynamics of acceptors in silicon using time-domain spectroscopy with a free-electron laser. Both the population and coherence lifetimes for acceptors in natural silicon are substantially longer—e.g. approximately 60 ps for boron—than implied by the spectral linewidths; our experiments also establish the recombination time for ionized acceptors to be, at approximately 500 ps, nearly an order of magnitude longer. We show that there are no extra sources of decoherence introduced by the host crystal, other than the population relaxation. In this sense, the crystal acts as an atom trap, and, by introducing quantum coherent control of acceptors to that previously established for donors, we open the way to optically controllable nanoscale p-n devices.

  19. Competitive solid-phase immunoassay of gastrin in serum using time-resolved fluorometry

    DEFF Research Database (Denmark)

    Johnsen, Anders H; Assaad, Fahed N; Rehfeld, Jens F

    2011-01-01

    A competitive solid-phase assay for the measurement of gastrin in serum using time-resolved fluorescence was developed as an alternative to conventional radioimmunoassay (RIA) technology.......A competitive solid-phase assay for the measurement of gastrin in serum using time-resolved fluorescence was developed as an alternative to conventional radioimmunoassay (RIA) technology....

  20. Time-resolved detection of surface plasmon polaritons with a scanning tunneling microscope

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Ha, T.; Jensen, Jacob Riis

    1998-01-01

    We present the time-resolved detection of surface plasmon polaritons with an STM. The results indicate that the time resolved signal is due to rectification of coherently superimposed plasmon voltages. The comparison with differential reflectivity measurements shows that the tip itself influences...

  1. Primary α and secondary β relaxation dynamics of meta-toluidine in the liquid state investigated by broadband dielectric spectroscopy

    Science.gov (United States)

    Švajdlenková, H.; Ruff, A.; Lunkenheimer, P.; Loidl, A.; Bartoš, J.

    2017-08-01

    We report a broadband dielectric spectroscopic (BDS) study on the clustering fragile glass-former meta-toluidine (m-TOL) from 187 K up to 289 K over a wide frequency range of 10-3-109 Hz with focus on the primary α relaxation and the secondary β relaxation above the glass temperature Tg. The broadband dielectric spectra were fitted by using the Havriliak-Negami (HN) and Cole-Cole (CC) models. The β process disappearing at Tβ,disap = 1.12Tg exhibits non-Arrhenius dependence fitted by the Vogel-Fulcher-Tamman-Hesse equation with T0βVFTH in accord with the characteristic differential scanning calorimetry (DSC) limiting temperature of the glassy state. The essential feature of the α process consists in the distinct changes of its spectral shape parameter βHN marked by the characteristic BDS temperatures TB1βHN and TB2βHN. The primary α relaxation times were fitted over the entire temperature and frequency range by several current three-parameter up to six-parameter dynamic models. This analysis reveals that the crossover temperatures of the idealized mode coupling theory model (TcMCT), the extended free volume model (T0EFV), and the two-order parameter (TOP) model (Tmc) are close to TB1βHN, which provides a consistent physical rationalization for the first change of the shape parameter. In addition, the other two characteristic TOP temperatures T0TOP and TA are coinciding with the thermodynamic Kauzmann temperature TK and the second change of the shape parameter at around TB2βHN, respectively. These can be related to the onset of the liquid-like domains in the glassy state or the disappearance of the solid-like domains in the normal liquid state.

  2. SVD-aided pseudo principal-component analysis: A new method to speed up and improve determination of the optimum kinetic model from time-resolved data

    Energy Technology Data Exchange (ETDEWEB)

    Oang, Key Young; Yang, Cheolhee; Muniyappan, Srinivasan; Kim, Jeongho; Ihee, Hyotcherl

    2017-07-01

    Determination of the optimum kinetic model is an essential prerequisite for characterizing dynamics and mechanism of a reaction. Here, we propose a simple method, termed as singular value decomposition-aided pseudo principal-component analysis (SAPPA), to facilitate determination of the optimum kinetic model from time-resolved data by bypassing any need to examine candidate kinetic models. We demonstrate the wide applicability of SAPPA by examining three different sets of experimental time-resolved data and show that SAPPA can efficiently determine the optimum kinetic model. In addition, the results of SAPPA for both time-resolved X-ray solution scattering (TRXSS) and transient absorption (TA) data of the same protein reveal that global structural changes of protein, which is probed by TRXSS, may occur more slowly than local structural changes around the chromophore, which is probed by TA spectroscopy.

  3. SVD-aided pseudo principal-component analysis: A new method to speed up and improve determination of the optimum kinetic model from time-resolved data

    Directory of Open Access Journals (Sweden)

    Key Young Oang

    2017-07-01

    Full Text Available Determination of the optimum kinetic model is an essential prerequisite for characterizing dynamics and mechanism of a reaction. Here, we propose a simple method, termed as singular value decomposition-aided pseudo principal-component analysis (SAPPA, to facilitate determination of the optimum kinetic model from time-resolved data by bypassing any need to examine candidate kinetic models. We demonstrate the wide applicability of SAPPA by examining three different sets of experimental time-resolved data and show that SAPPA can efficiently determine the optimum kinetic model. In addition, the results of SAPPA for both time-resolved X-ray solution scattering (TRXSS and transient absorption (TA data of the same protein reveal that global structural changes of protein, which is probed by TRXSS, may occur more slowly than local structural changes around the chromophore, which is probed by TA spectroscopy.

  4. Time-resolved crystallization of deeply cooled liquid hydrogen isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Kuehnel, Matthias

    2014-02-15

    This thesis serves two main purposes: 1. The introduction of a novel experimental method to investigate phase change dynamics of supercooled liquids 2. First-time measurements for the crystallization behaviour for hydrogen isotopes under various conditions (1) The new method is established by the synergy of a liquid microjet of ∼ 5 μm diameter and a scattering technique with high spatial resolution, here linear Raman spectroscopy. Due to the high directional stability and the known velocity of the liquid filament, its traveling axis corresponds to a time axis static in space. Utilizing evaporative cooling in a vacuum environment, the propagating liquid cools down rapidly and eventually experiences a phase transition to the crystalline state. This temporal evolution is probed along the filament axis, ultimately resulting in a time resolution of 10 ns. The feasibility of this approach is proven successfully within the following experiments. (2) A main object of study are para-hydrogen liquid filaments. Raman spectra reveal a temperature gradient of the liquid across the filament. This behaviour can quantitatively be reconstructed by numerical simulations using a layered model and is rooted in the effectiveness of evaporative cooling on the surface and a finite thermal conductivity. The deepest supercoolings achieved are ∼ 30% below the melting point, at which the filament starts to solidify from the surface towards the core. With a crystal growth velocity extracted from the data the appropriate growth mechanism is identified. The crystal structure that initially forms is metastable and probably the result of Ostwald's rule of stages. Indications for a transition within the solid towards the stable equilibrium phase support this interpretation. The analog isotope ortho-deuterium is evidenced to behave qualitatively similar with quantitative differences being mass related. In further measurements, isotopic mixtures of para-hydrogen and ortho-deuterium are

  5. Time-resolved observations of water oxidation intermediates on a cobalt oxide nanoparticle catalyst

    Science.gov (United States)

    Zhang, Miao; de Respinis, Moreno; Frei, Heinz

    2014-04-01

    In any artificial photosynthetic system, the oxidation of water to molecular oxygen provides the electrons needed for the reduction of protons or carbon dioxide to a fuel. Understanding how this four-electron reaction works in detail is important for the development of improved robust catalysts made of Earth-abundant materials, like first-row transition-metal oxides. Here, using time-resolved Fourier-transform infrared spectroscopy and under reaction conditions, we identify intermediates of water oxidation catalysed by an abundant metal-oxide catalyst, cobalt oxide (Co3O4). One intermediate is a surface superoxide (three-electron oxidation intermediate absorbing at 1,013 cm-1), whereas a second observed intermediate is attributed to an oxo Co(IV) site (one-electron oxidation intermediate absorbing at 840 cm-1). The temporal behaviour of the intermediates reveals that they belong to different catalytic sites. Knowledge of the structure and kinetics of surface intermediates will enable the design of improved metal-oxide materials for more efficient water oxidation catalysis.

  6. Time-resolved photoluminescence characterization of oxygen-related defect centers in AlN

    Energy Technology Data Exchange (ETDEWEB)

    Genji, Kumihiro; Uchino, Takashi, E-mail: uchino@kobe-u.ac.jp [Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501 (Japan)

    2016-07-11

    Time-resolved photoluminescence (PL) spectroscopy has been employed to investigate the emission characteristics of oxygen-related defects in AlN in the temperature region from 77 to 500 K. Two PL components with different decay constants are observed in the near-ultraviolet to visible regions. One is the PL component with decay time of <10 ns and its peak position shifts to longer wavelengths from ∼350 to ∼500 nm with increasing temperature up to 500 K. This PL component is attributed to the radiative relaxation of photoexcited electrons from the band-edge states to the ground state of the oxygen-related emission centers. In the time region from tens to hundreds of nanoseconds, the second PL component emerges in the wavelength region from 300 to 400 nm. The spectral shape and the decay profiles are hardly dependent on temperature. This temperature-independent PL component most likely results from the transfer of photoexcited electrons from the band-edge states to the localized excited state of the oxygen-related emission centers. These results provide a detailed insight into the radiative relaxation processes of the oxygen-related defect centers in AlN immediately after the photoexcitation process.

  7. Time-resolved temperature and number density measurements in a repetitively pulsed nanosecond-duration discharge

    Science.gov (United States)

    Manoharan, Rounak; Boyson, Toby K.; O'Byrne, Sean

    2016-12-01

    This paper presents a fast detection technique using diode laser absorption spectroscopy as an optical diagnostic tool to measure time-resolved temperature and number density in a repetitively pulsed nanosecond-duration discharge. Argon atoms in the 1 s3 metastable state were optically probed by current scanning a vertical cavity surface emitting laser diode over the 1 s3→2 p4 transition at 794 nm. Temperature and number density measurements are presented at pulse energies from 20 μJ to 300 μJ, at a constant pressure of 2.67 kPa and 10 kHz repetition frequency. A time resolution of 2 ns was achieved for the measurements during and after the discharge pulse. We demonstrate the method used to make nanosecond resolution measurements, the precision of this technique and the effect of pulse energy on the translational temperature and number density of the metastable atoms. Our measurements show that, for small input pulse energies, the peak temperature of the argon atoms in the 1s3 state can exceed ambient room temperature by up to an order of magnitude.

  8. Combined zero-quantum and spin-diffusion mixing for efficient homonuclear correlation spectroscopy under fast MAS: broadband recoupling and detection of long-range correlations.

    Science.gov (United States)

    Lu, Xingyu; Guo, Changmiao; Hou, Guangjin; Polenova, Tatyana

    2015-01-01

    Fast magic angle spinning (MAS) NMR spectroscopy is emerging as an essential analytical and structural biology technique. Large resolution and sensitivity enhancements observed under fast MAS conditions enable structural and dynamics analysis of challenging systems, such as large macromolecular assemblies and isotopically dilute samples, using only a fraction of material required for conventional experiments. Homonuclear dipolar-based correlation spectroscopy constitutes a centerpiece in the MAS NMR methodological toolbox, and is used essentially in every biological and organic system for deriving resonance assignments and distance restraints information necessary for structural analysis. Under fast MAS conditions (rotation frequencies above 35-40 kHz), dipolar-based techniques that yield multi-bond correlations and non-trivial distance information are ineffective and suffer from low polarization transfer efficiency. To overcome this limitation, we have developed a family of experiments, CORD-RFDR. These experiments exploit the advantages of both zero-quantum RFDR and spin-diffusion based CORD methods, and exhibit highly efficient and broadband dipolar recoupling across the entire spectrum, for both short-range and long-range correlations. We have verified the performance of the CORD-RFDR sequences experimentally on a U-(13)C,(15)N-MLF tripeptide and by numerical simulations. We demonstrate applications of 2D CORD-RFDR correlation spectroscopy in dynein light chain LC8 and HIV-1 CA tubular assemblies. In the CORD-RFDR spectra of LC8 acquired at the MAS frequency of 40 kHz, many new intra- and inter-residue correlations are detected, which were not observed with conventional dipolar recoupling sequences. At a moderate MAS frequency of 14 kHz, the CORD-RFDR experiment exhibits excellent performance as well, as demonstrated in the HIV-1 CA tubular assemblies. Taken together, the results indicate that CORD-RFDR experiment is beneficial in a broad range of conditions

  9. Time-resolved X-ray transmission microscopy on magnetic microstructures; Zeitaufloesende Roentgentransmissionsmikroskopie an magnetischen Mikrostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Puzic, Aleksandar

    2007-10-23

    Three excitation schemes were designed for stroboscopic imaging of magnetization dynamics with time-resolved magnetic transmission X-ray microscopy (TR-MTXM). These techniques were implemented into two types of X-ray microscopes, namely the imaging transmission X-ray microscope (ITXM) and the scanning transmission X-ray microscope (STXM), both installed at the electron storage ring of the Advanced Light Source in Berkeley, USA. Circular diffraction gratings (Fresnel zone plates) used in both microscopes as focusing and imaging elements presently allow for lateral resolution down to 30 nm. Magnetic imaging is performed by using the X-ray magnetic circular dichroism (XMCD) as element specific contrast mechanism. The developed methods have been successfully applied to the experimental investigation of magnetization dynamics in ferromagnetic microstructures. A temporal resolution well below 100 ps was achieved. A conventional pump-probe technique was implemented first. The dynamic response of the magnetization excited by a broadband pulsed magnetic field was imaged spatially resolved using focused X-ray flashes. As a complementary method, the spatially resolved ferromagnetic resonance (SR-FMR) technique was developed for experimental study of magnetization dynamics in the frequency domain. As a third excitation mode, the burst excitation was implemented. The performance and efficiency of the developed methods have been demonstrated by imaging the local magnetization dynamics in laterally patterned ferromagnetic thin-film elements and three-layer stacks. The existence of multiple eigenmodes in the excitation spectra of ferromagnetic microstructures has been verified by using the pump-probe technique. Magnetostatic spin waves were selectively excited and detected with a time resolution of 50 ps using the SR-FMR technique. Thorough analysis of 20 in most cases independently prepared samples has verified that vortices which exhibit a low-amplitude switching of their core

  10. BROADBAND ESO/VISIR-SPITZER INFRARED SPECTROSCOPY OF THE OBSCURED SUPERGIANT X-RAY BINARY IGR J16318-4848

    Energy Technology Data Exchange (ETDEWEB)

    Chaty, S.; Rahoui, F., E-mail: sylvain.chaty@cea.fr, E-mail: frahoui@cfa.harvard.edu [AIM (UMR-E 9005 CEA/DSM-CNRS-Universite Paris Diderot) Irfu/Service d' Astrophysique, Centre de Saclay, FR-91191 Gif-sur-Yvette Cedex (France)

    2012-06-01

    A new class of X-ray binaries has recently been discovered by the high-energy observatory INTEGRAL. It is composed of intrinsically obscured supergiant high-mass X-ray binaries, unveiled by means of multi-wavelength X-ray, optical, near- and mid-infrared observations, in particular, photometric and spectroscopic observations using ESO facilities. However, the fundamental questions about these intriguing sources, namely, their formation, evolution, and the nature of their environment, are still unsolved. Among them, IGR J16318-4848, a compact object orbiting around a supergiant B[e] star, seems to be one of the most extraordinary celestial sources of our Galaxy. We present here new ESO/Very Large Telescope (VLT) VISIR mid-infrared (MIR) spectroscopic observations of this source. First, line diagnostics allow us to confirm the presence of absorbing material (dust and cold gas) enshrouding the whole binary system, and to characterize the nature of this material. Second, by fitting broadband near- to mid-infrared spectral energy distribution, including ESO NTT/SofI, VLT/VISIR, and Spitzer data, with a phenomenological model for sgB[e] stars, we show that the star is surrounded by an irradiated rim heated to a temperature of {approx}3800-5500 K, along with a viscous disk component at an inner temperature of {approx}750 K. VISIR data allow us to exclude the spherical geometry for the dust component. This detailed study will allow us in the future to get better constraints on the formation and evolution of such rare and short-living high-mass X-ray binary systems in our Galaxy.

  11. Investigation of setting reaction in magnesium potassium phosphate ceramics with time resolved infrared spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Mácová, Petra; Viani, Alberto

    2017-01-01

    Roč. 205, October (2017), s. 62-66 ISSN 0167-577X R&D Projects: GA MŠk(CZ) LO1219 Keywords : amorphous materials * magnesium potassium phosphate cements * FTIR Subject RIV: JH - Ceramics , Fire-Resistant Materials and Glass Impact factor: 2.572, year: 2016 http://www.sciencedirect.com/science/article/pii/S0167577X17309552

  12. Extremely slow intramolecular vibrational redistribution: Direct observation by time-resolved raman spectroscopy in trifluoropropyne

    Science.gov (United States)

    Malinovsky, A. L.; Makarov, A. A.; Ryabov, E. A.

    2011-04-01

    We have studied the dynamics of intramolecular vibrational redistribution (IVR) from the initially excited mode v1 ≈ 3330 cm-1 (acetylene-type H-C bond) in H-C≡C-CF3 molecules in the gaseous phase by means of anti-Stokes spontaneous Raman scattering. The time constant of this process is estimated as 2.3 ns—this is the slowest IVR time reported so far for the room-temperature gases. It is suggested that so long IVR time with respect to the other propyne derivatives can be explained by a larger defect, in this case, of the Fermi resonance of v1 with v2 + 2v7—the most probable doorway state leading to IVR from v1 to the bath of all vibrational-rotational states with the close energies. In addition, it is shown that the observed dynamics is in agreement with a theoretical model assuming strong vibrational-rotational mixing.

  13. Time-resolved photoelectron nano-spectroscopy of individual silver particles: Perspectives and limitations

    DEFF Research Database (Denmark)

    Rohmer, Martin; Bauer, Michael; Leissner, Till

    2010-01-01

    Simultaneous time- and energy-resolved two-photon photoemission with nanometer resolution is demonstrated for the first time. We monitor the energy dependence of the decay dynamics of electron excitations in individual silver particles, which were deposited from a gas aggregation cluster source o...

  14. Advances in high repetition rate, ultra-short, gigawatt laser systems for time-resolved spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    DiMauro, L.F.

    1991-12-31

    The objective of this article is to emphasize the current advances in the development of high-repetition rate amplifier pumps. Although this review highlights amplifier pump development, any recent data from achieved outputs via the tunable amplifier section is also discussed. The first section describes desirable parameters attributable to the pump amplifier while the rest of the article deals with specific examples for various options. The pump amplifiers can be characterized into two distinct classes; those achieving operation in the hundred hertz regime and those performing at repetition rates {ge}1kHz. 23 refs., 4 figs.

  15. Advances in high repetition rate, ultra-short, gigawatt laser systems for time-resolved spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    DiMauro, L.F.

    1991-01-01

    The objective of this article is to emphasize the current advances in the development of high-repetition rate amplifier pumps. Although this review highlights amplifier pump development, any recent data from achieved outputs via the tunable amplifier section is also discussed. The first section describes desirable parameters attributable to the pump amplifier while the rest of the article deals with specific examples for various options. The pump amplifiers can be characterized into two distinct classes; those achieving operation in the hundred hertz regime and those performing at repetition rates {ge}1kHz. 23 refs., 4 figs.

  16. Temperature-dependent loop formation kinetics in flexible peptides studied by time-resolved fluorescence spectroscopy

    Directory of Open Access Journals (Sweden)

    Harekrushna Sahoo

    2006-01-01

    Full Text Available Looping rates in short polypeptides can be determined by intramolecular fluorescence quenching of a 2,3-diazabicyclo[2.2.2]oct-2-ene-labeled asparagine (Dbo by tryptophan. By this methodology, the looping rates in glycine-serine peptides with the structure Trp-(Gly-Sern-Dbo-NH2 of different lengths (n = 0–10 were determined in dependence on temperature in D2O and the activation parameters were derived. In general, the looping rate increases with decreasing peptide length, but the shortest peptide (n=0 shows exceptional behavior because its looping rate is slower than that for the next longer ones (n=1,2. The activation energies increase from 17.5 kJ mol−1 for the longest peptide (n=10 to 20.5 kJ mol−1 for the shortest one (n=0, while the pre-exponential factors (log⁡(A/s−1 range from 10.20 to 11.38. The data are interpreted in terms of an interplay between internal friction (stiffness of the biopolymer backbone and steric hindrance effects and solvent friction (viscosity-limited diffusion. For the longest peptides, the activation energies resemble more and more the value expected for solvent viscous flow. Internal friction is most important for the shortest peptides, causing a negative curvature and a smaller than ideal slope (ca. –1.1 of the double-logarithmic plots of the looping rates versus the number of peptide chain segments (N. Interestingly, the corresponding plot for the pre-exponential factors (logA versus logN shows the ideal slope (–1.5. While the looping rates can be used to assess the flexibility of peptides in a global way, it is suggested that the activation energies provide a measure of the “thermodynamic” flexibility of a peptide, while the pre-exponential factors reflect the “dynamic” flexibility.

  17. Time resolved spectroscopy and gain studies of Fullerenes C60 and C70.

    Science.gov (United States)

    Qaiser, Darakhshan; Khan, Mohd Shahid; Singh, R D; Khan, Zahid H

    2013-09-01

    The fluorescence decay time of Fullerenes C60 and C70 in pure form as well as in mixture with Coumarin C440 and Quinizarine dyes are studied. Results indicate that the decay of pure fullerenes is constant throughout the solute concentration and it is also independent of excitation wavelength, whereas in the case of mixture with dyes different behavior is noticed. We have also calculated the Stern-Volmer quenching constant and optical gain of both the fullerenes from which it is found that the optical gain is positive for Fullerene C70 only in a very narrow range of concentration. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Operation mechanism of a molecular machine revealed using time-resolved vibrational spectroscopy.

    Science.gov (United States)

    Panman, Matthijs R; Bodis, Pavol; Shaw, Daniel J; Bakker, Bert H; Newton, Arthur C; Kay, Euan R; Brouwer, Albert M; Buma, Wybren Jan; Leigh, David A; Woutersen, Sander

    2010-06-04

    Rotaxanes comprise macrocycles that can shuttle between docking stations along an axle. We explored the nanosecond shuttling mechanism by reversing the relative binding affinities of two stations through ultraviolet-induced transient reduction. We monitored the ensuing changes in the CO-stretching bands of the two stations and the shuttling macrocycle by means of an infrared probing pulse. Because hydrogen-bond scission and formation at the initial and final stations led to well-resolved changes in the respective CO-stretch frequencies, the departure and arrival of the macrocycle could be observed separately. We found that the shuttling involves two steps: thermally driven escape from the initial station, followed by rapid motion along the track ending either at the initial or final station. By varying the track's length, we found that the rapid motion approximates a biased one-dimensional random walk. However, surprisingly, the direction of the overall motion is opposite that of the bias.

  19. Application of Time-Resolved Tryptophan Phosphorescence Spectroscopy to Protein Folding Studies.

    Science.gov (United States)

    Subramaniam, Vinod

    This thesis presents studies of the protein folding problem, one of the most significant questions in contemporary biophysics. Sensitive biophysical techniques, including room temperature tryptophan phosphorescence, which reports on the local environment of the residue, and the lability of proteins to denaturation, a global parameter, were used to assess the validity of the traditional assumption that the biologically active state of a protein is the 'native' state, and to determine whether the pathways of folding in vitro lead to the folded state achieved in vivo. Phosphorescence techniques have also been extended to study, for the first time, emission from tryptophan residues engineered into specific positions as reporters of protein structure. During in vitro refolding of E. coli alkaline phosphatase and bovine 13-lactoglobulin, significant differences were found between the refolded proteins and the native conformations, which have no apparent effect on the biological functions. Slow conformational transitions, termed 'annealing,' that occur long after the return of enzyme activity of alkaline phosphatase are manifested in the retarded recovery of phosphorescence intensity, lifetime, and protein lability. While 'annealing' is not observed for beta -lactoglobulin, both phosphorescence and lability experiments reveal changes in the structure of the refolded protein, even though its biological activity, retinol binding, is fully recovered. This result suggests that the pathways of folding in vitro need not lead to the structure formed in vivo. We have used phosphorescence techniques to study the refolding of ribonuclease T1, which exhibits slow kinetics characteristic of proline isomerization. Furthermore, the ability to extract structural information from phosphorescent tryptophan probes engineered into selected regions represents an important advance in studying protein structure; we have reported the first such results from a mutant staphylococcal nuclease. The refolding data have been interpreted in the context of recent theoretical work on rugged energy landscape models of protein folding. Our results suggest that the barriers to folding can be as large as ~ 20 kcal-mol^{-1}, and imply that the conventional definition of the 'native' state as the biologically active conformation may need revision to acknowledge that the active state may represent a long-lived intermediate on the pathway to the native structure.

  20. Operation mechanism of a molecular machine revealed using time-resolved vibrational spectroscopy

    NARCIS (Netherlands)

    Panman, M.R.; Bodis, P.; Shaw, D.J.; Bakker, B.H.; Newton, A.C.; Kay, E.R.; Brouwer, A.M.; Buma, W.J.; Leigh, D.A.; Woutersen, S.

    2010-01-01

    Rotaxanes comprise macrocycles that can shuttle between docking stations along an axle. We explored the nanosecond shuttling mechanism by reversing the relative binding affinities of two stations through ultraviolet-induced transient reduction. We monitored the ensuing changes in the CO-stretching

  1. Expansion dynamics of supercritical water probed by picosecond time-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Gladytz, Thomas; Abel, Bernd; Siefermann, Katrin R

    2015-02-21

    Vibrational excitation of liquid water with femtosecond laser pulses can create extreme states of water. Yet, the dynamics directly after initial sub-picosecond delocalization of molecular vibrations remain largely unclear. We study the ultrafast expansion dynamics of an accordingly prepared supercritical water phase with a picosecond time resolution. Our experimental setup combines vacuum-compatible liquid micro-jet technology and a table top High Harmonic light source driven by a femtosecond laser system. An ultrashort laser pulse centered at a wavelength of 2900 nm excites the OH-stretch vibration of water molecules in the liquid. The deposited energy corresponds to a supercritical phase with a temperature of about 1000 K and a pressure of more than 1 GPa. We use a time-delayed extreme ultraviolet pulse centered at 38.6 eV, and obtained via High Harmonic generation (HHG), to record valence band photoelectron spectra of the expanding water sample. The series of photoelectron spectra is analyzed with noise-corrected target transform fitting (cTTF), a specifically developed multivariate method. Together with a simple fluid dynamics simulation, the following picture emerges: when a supercritical phase of water expands into vacuum, temperature and density of the first few nanometers of the expanding phase drop below the critical values within a few picoseconds. This results in a supersaturated phase, in which condensation seeds form and grow from small clusters to large clusters on a 100 picosecond timescale.

  2. Investigation Of Laser-Polymer Interaction By Time Resolved Emission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Urech, L.; Lippert, T.; Wokaun, A.

    2005-03-01

    The plasma emission properties of poly(vinyl chloride) (PVC), glycidyl azide polymer (GAP) and poly(vinyl nitrate) (PVN) have been investigated. The plasma temperature and electron density were calculated from the recorded spectra. For the energetic polymers (GAP and PVN) the plasma temperature decreased faster and had a higher maximum value. The fastest rate of decrease in the electron density was observed for GAP, whereas PVN and PVC had similar, but slower density reduction. For all polymers an increase in the plasma temperature within the first {mu}s was observed. (author)

  3. Photodestruction of NO2- using time resolved multicoincidence detection photofragment spectroscopy

    NARCIS (Netherlands)

    Dinu, L.; Zande, W.J. van der

    2004-01-01

    We present an experiment on the photodestruction of the NO2- anion at 266 nm. We have quantified the competition between photodetachment and photodissociation and have identified the nature of the photodissociation process from the photofragment angular distribution. This study involves a novel

  4. Magnetic dynamics studied by high-resolution electron spectroscopy and time-resolved electron microscopy

    Science.gov (United States)

    Jayaraman, Rajeswari

    Future information technology requires an increased magnetically encoded data density and novel electromagnetic modes of data transfer. While to date magnetic properties are observed and characterized mostly statically, the need emerges to monitor and capture their fast dynamics. In this talk, I will focus on the spin dynamics i.e. spin wave excitations and the dynamics of a new topological distribution of spins termed ``skyrmions''. Wave packets of spin waves offer the unique capability to transport a quantum bit, the spin, without the transport of charge or mass. Here, large wave-vector spin waves are of particular interest as they admit spin localization within a few nanometers. By using our recently developed electron energy loss spectrometer, we could study such spin waves in ultrathin films with an unprecedented energy resolution of 4 meV. By virtue of the finite penetration depth of low energy electrons, spin waves localized at interfaces between a substrate and a thin capping layer can be been studied yielding information about the exchange coupling between atoms at the interface. The quantization of spin waves with wave vectors perpendicular to the film gives rise to standing modes to which EELS has likewise access. Such studies when carried out as function of the film thickness again yield information on the layer dependence of the exchange coupling. Magnetic skyrmions are promising candidates as information carriers in logic or storage devices. Currently, little is known about the influence of disorder, defects, or external stimuli on the spatial distribution and temporal evolution of the skyrmion lattice. In this talk, I will describe the dynamical role of disorder in a large and flat thin film of Cu2OSeO3, exhibiting a skyrmion phase in an insulating material. We image up to 70,000 skyrmions by means of cryo-Lorentz Transmission Electron Microscopy as a function of the applied magnetic field. In the skyrmion phase, dislocations are shown to cause the emergence and switching between domains with different lattice orientations, and the temporal fluctuation of these domains is filmed. These observations pave the way to the control of a large 2D array of skyrmions.

  5. The variable projection algorithm in time-resolved spectroscopy, microscopy and mass spectrometry applications

    NARCIS (Netherlands)

    Mullen, K.M.; van Stokkum, I.H.M.

    2009-01-01

    Nonlinear least squares optimization problems in which the parameters can be partitioned into two sets such that optimal estimates of parameters in one set are easy to solve for given fixed values of the parameters in the other set are common in practice. Particularly ubiquitous are data fitting

  6. Infrared absorption of CH3OSO detected with time-resolved Fourier-transform spectroscopy.

    Science.gov (United States)

    Chen, Jin-Dah; Lee, Yuan-Pern

    2011-03-07

    A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to detect temporally resolved infrared absorption spectra of CH(3)OSO produced upon irradiation of a flowing gaseous mixture of CH(3)OS(O)Cl in N(2) or CO(2) at 248 nm. Two intense transient features with origins near 1152 and 994 cm(-1) are assigned to syn-CH(3)OSO; the former is attributed to overlapping bands at 1154 ± 3 and 1151 ± 3 cm(-1), assigned to the S=O stretching mixed with CH(3) rocking (ν(8)) and the S=O stretching mixed with CH(3) wagging (ν(9)) modes, respectively, and the latter to the C-O stretching (ν(10)) mode at 994 ± 6 cm(-1). Two weak bands at 2991 ± 6 and 2956 ± 3 cm(-1) are assigned as the CH(3) antisymmetric stretching (ν(2)) and symmetric stretching (ν(3)) modes, respectively. Observed vibrational transition wavenumbers agree satisfactorily with those predicted with quantum-chemical calculations at level B3P86∕aug-cc-pVTZ. Based on rotational parameters predicted at that level, the simulated rotational contours of these bands agree satisfactorily with experimental results. The simulation indicates that the S=O stretching mode of anti-CH(3)OSO near 1164 cm(-1) likely makes a small contribution to the observed band near 1152 cm(-1). A simple kinetic model of self-reaction is employed to account for the decay of CH(3)OSO and yields a second-order rate coefficient k=(4 ± 2)×10(-10) cm(3)molecule(-1)s(-1). © 2011 American Institute of Physics.

  7. The Fourteenth International Meeting on Time-Resolved Vibrational Spectroscopy (TRVS XIV)

    Science.gov (United States)

    2010-02-03

    Sponsored by Infrared Systems Development and Infrared Associates Sunday, May 10, 2009      7:30 AM Breakfast 8:50 AM Opening ...solutes 10:20 AM C Artem A Bakulin Wayne Liang Thomas la Cour Do hydrophobic groups stabilize the water structure?. , , Jansen Douwe A Wiersma Huib... opening of a beta turn thioxopeptide 13 Joshua Lessing, Jongjin Kim, Kevin Jones, Ziad Ganim, and Andrei Tokmakoff, MIT Two dimensional vibrational

  8. Picosecond Time-Resolved Temperature and Density Measurements with K-Shell Spectroscopy

    Science.gov (United States)

    Stillman, C. R.; Nilson, P. M.; Ivancic, S. T.; Mileham, C.; Froula, D. H.; Golovkin, I. E.

    2017-10-01

    The thermal x-ray emission from rapidly heated solid targets containing a buried-aluminum layer was measured to track the evolution of the bulk plasma conditions. The targets were driven by high-contrast 1 ω laser pulses at focused intensities up to 1 × 1019 W/cm2. A streaked x-ray spectrometer recorded the AlHeα and lithium-like satellite lines with 2-ps temporal resolution and moderate resolving power (E E ΔE 1000 ΔE 1000) . Time-integrated measurements over the same spectral range were used to correct the streaked data for variations in photocathode sensitivity. Linewidths and intensity ratios from the streaked data were interpreted using a collisional radiative atomic kinetics model to provide the average plasma conditions in the buried layer as a function of time. Experimental uncertainties in the measured plasma conditions are quantified within a consistent model-dependent framework. The data demonstrate the production of a 330 +/-56 eV, 0.9 +/-0.3 g/cm3 plasma that evolves slowly during peak Heα emission. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  9. Two-color time-resolved spectroscopy of helium using high-order harmonics

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, J.; Mevel, E.; Zerne, R.; Wahlstroem, C.-G.; Svanberg, S. [Lund Univ. (Sweden). Dept. of Physics; L`Huillier, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Recherche sur l`Etat Condense, les Atomes et les Molecules

    1995-02-14

    The radiative lifetime of the 1s2p {sup 1}P state of helium is measured in a two-colour ionization experiment with a 5% accuracy. The state is excited by the 13th harmonic of a tunable 80 ps laser and ionized by a synchronous ultraviolet laser, with a variable time delay. This experiment demonstrates that the high harmonics generated in a jet of rare gas exposed to an intense laser field provide a tunable short-pulse XUV source ideally suited for pump/probe type of studies and, in particular, short lifetime measurements. (author).

  10. Time-resolved terahertz spectroscopy in a parallel-plate waveguide

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    The parallel plate waveguide (PPWG), formed by two conducting parallel plates separated by a distance on the order of the wavelength of the propagating light, has shown itself to be a near ideal terahertz interconnect exhibiting low loss and dispersionless propagation.[1] It is also a useful tool...

  11. Time-resolved spectroscopy of the electrode region in a fluorescent lamp

    National Research Council Canada - National Science Library

    Lennartsson, Thomas; Huldt, Sven

    2011-01-01

    .... The intensity of the spectral lines of neutral and singly ionized mercury and krypton in the electrode region in a fluorescent lamp are investigated, both as a function of current through the tube...

  12. Finite-difference time-domain analysis of time-resolved terahertz spectroscopy experiments

    DEFF Research Database (Denmark)

    Larsen, Casper; Cooke, David G.; Jepsen, Peter Uhd

    2011-01-01

    probe pulse and can be determined solely by the pump pulse duration. Our method is found to reproduce complicated two-dimensional transient conductivity maps exceedingly well, demonstrating the power of the time-domain numerical method for extracting ultrafast and dynamic transport parameters from time...

  13. Light harvesting, light adaptation and photoprotection in aquatic photosynthesis studies by time-resolved fluorescence spectroscopy

    NARCIS (Netherlands)

    Chukhutsina, V.

    2015-01-01

    Summary Aquatic photosynthetic organisms unavoidably experience light fluctuations that vary in amplitude, duration and origin, compromising their photosynthetic efficiency. Weather conditions and underwater flow cause continuous changes in irradiance to which the organisms have to

  14. SUDDEN POLARIZATION IN THE TWISTED, PHANTOM STATE OF TETRAPHENYLETHYLENE DETECTED BY TIME-RESOLVED MICROWAVE CONDUCTIVITY

    NARCIS (Netherlands)

    SCHUDDEBOOM, W; JONKER, SA; WARMAN, JM; DEHAAS, MP; VERMEULEN, MJW; JAGER, WF; DELANGE, B; FERINGA, BL; FESSENDEN, RW

    1993-01-01

    Photoexcitation of the symmetrical molecules tetraphenylethylene and tetra-p-methoxyphenylethylene dissolved in saturated hydrocarbon solvents results in a transient increase in the dielectric loss of the solutions as monitored using the nanosecond time-resolved microwave conductivity (TRMC)

  15. The Application of Time Resolved Dielectric Instruments to Air Force Ground Fleet Maintenance

    National Research Council Canada - National Science Library

    Thompson, Stephanie

    1998-01-01

    In 1993 the Military Equipment Evaluation Program (MEEP) located at Eglin Air Force Base, FL, evaluated a time resolved dielectric instrument for use in air force ground fleet maintenance applications...

  16. Time-resolved spin-dependent processes in magnetic field effects in organic semiconductors

    Science.gov (United States)

    Peng, Qiming; Li, Xianjie; Li, Feng

    2012-12-01

    We investigated the time-resolved magnetic field effects (MFEs) in tri-(8-hydroxyquinoline)-aluminum (Alq3) based organic light-emitting diodes (OLEDs) through the transient electroluminescence (EL) method. The values of magneto-electroluminescence (MEL) decrease with the time, and the decreasing slope is proportional to the driving voltage. Specifically, negative MELs are seen when the driving voltage is high enough (V > 11 V). We propose a model to elucidate the spin-dependent processes and theoretically simulate the time-resolved MELs. In particular, this dynamic analysis of time-resolved MELs reveals that the intersystem crossing between singlet and triplet electron-hole pairs and the triplet-triplet annihilation are responsible for the time-resolved MELs at the beginning and enduring periods of the pulse, respectively.

  17. Ultra-broadband 2D electronic spectroscopy of carotenoid-bacteriochlorophyll interactions in the LH1 complex of a purple bacterium

    Energy Technology Data Exchange (ETDEWEB)

    Maiuri, Margherita [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133 (Italy); Department of Chemistry, Princeton University, Washington Road, Princeton, New Jersey 08544 (United States); Réhault, Julien; Polli, Dario; Cerullo, Giulio, E-mail: giulio.cerullo@polimi.it [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133 (Italy); Carey, Anne-Marie; Hacking, Kirsty; Cogdell, Richard J. [Glasgow Biomedical Research Centre, IBLS, University of Glasgow, 126 Place, Glasgow G12 8TA, Scotland (United Kingdom); Garavelli, Marco [Dipartimento di Chimica “G. Ciamician,” Università di Bologna, Via Selmi 2, IT-40126 Bologna (Italy); CNRS, Institut de Chimie de Lyon, École Normale Supérieure de Lyon, Université de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07 (France); Lüer, Larry [Madrid Institute for Advanced Studies, IMDEA Nanociencia, Madrid (Spain)

    2015-06-07

    We investigate the excitation energy transfer (EET) pathways in the photosynthetic light harvesting 1 (LH1) complex of purple bacterium Rhodospirillum rubrum with ultra-broadband two-dimensional electronic spectroscopy (2DES). We employ a 2DES apparatus in the partially collinear geometry, using a passive birefringent interferometer to generate the phase-locked pump pulse pair. This scheme easily lends itself to two-color operation, by coupling a sub-10 fs visible pulse with a sub-15-fs near-infrared pulse. This unique pulse combination allows us to simultaneously track with extremely high temporal resolution both the dynamics of the photoexcited carotenoid spirilloxanthin (Spx) in the visible range and the EET between the Spx and the B890 bacterio-chlorophyll (BChl), whose Q{sub x} and Q{sub y} transitions peak at 585 and 881 nm, respectively, in the near-infrared. Global analysis of the one-color and two-color 2DES maps unravels different relaxation mechanisms in the LH1 complex: (i) the initial events of the internal conversion process within the Spx, (ii) the parallel EET from the first bright state S{sub 2} of the Spx towards the Q{sub x} state of the B890, and (iii) the internal conversion from Q{sub x} to Q{sub y} within the B890.

  18. Up-regulation of cerebral cytochrome-c-oxidase and hemodynamics by transcranial infrared laser stimulation: A broadband near-infrared spectroscopy study.

    Science.gov (United States)

    Wang, Xinlong; Tian, Fenghua; Reddy, Divya D; Nalawade, Sahil S; Barrett, Douglas W; Gonzalez-Lima, Francisco; Liu, Hanli

    2017-12-01

    Transcranial infrared laser stimulation (TILS) is a noninvasive form of brain photobiomulation. Cytochrome-c-oxidase (CCO), the terminal enzyme in the mitochondrial electron transport chain, is hypothesized to be the primary intracellular photoacceptor. We hypothesized that TILS up-regulates cerebral CCO and causes hemodynamic changes. We delivered 1064-nm laser stimulation to the forehead of healthy participants ( n = 11), while broadband near-infrared spectroscopy was utilized to acquire light reflectance from the TILS-treated cortical region before, during, and after TILS. Placebo experiments were also performed for accurate comparison. Time course of spectroscopic readings were analyzed and fitted to the modified Beer-Lambert law. With respect to the placebo readings, we observed (1) significant increases in cerebral concentrations of oxidized CCO (Δ[CCO]; >0.08 µM; p 0.8 µM; p 0.5 µM; p < 0.01) during and after TILS, and (2) linear interplays between Δ[CCO] versus Δ[HbO] and between Δ[CCO] versus Δ[HbT]. Ratios of Δ[CCO]/Δ[HbO] and Δ[CCO]/Δ[HbT] were introduced as TILS-induced metabolic-hemodynamic coupling indices to quantify the coupling strength between TILS-enhanced cerebral metabolism and blood oxygen supply. This study provides the first demonstration that TILS causes up-regulation of oxidized CCO in the human brain, and contributes important insight into the physiological mechanisms.

  19. Relevance of the structure of time-resolved spectral output to light-tissue interaction using intense pulsed light (IPL).

    Science.gov (United States)

    Ash, Caerwyn; Town, Godfrey; Bjerring, Peter

    2008-02-01

    High quality IPLs can offer simple, safe and effective treatments for long-term hair removal, removal of benign vascular and pigmented skin abnormalities, skin rejuvenation and acne treatments. Significant differences in clinical outcome have been recorded among different free-discharge and constant current IPLs despite identical settings. We investigated the differences in optical output of 19 IPLs in normal clinical use in the UK to evaluate spectral output, energy density values and pulse structure and propose a correlation between light-tissue interaction and spectral output as measured by time-resolved photo-spectrometry. Using a fast spectrometer, generating 1,000 full spectral scans per second, time resolved spectral data of IPL outputs was captured with a resolution of 0.035 nm. IPL spectral outputs were calculated and graphically modelled using MathCAD software for comparison. Several IPLs, which professed matching of pulse durations to the thermal relaxation times of specific follicular or vascular targets were shown to have effective pulse durations that were vastly shorter than those claimed. Some IPLs claiming 'square pulse' characteristics failed to show constant spectral output across the duration of the pulse or sub-pulses. This study provides a suitable method to determine accurately key parameters of the emitted light pulses from IPLs and confirms the direct correlation between the electrical discharge current profile and the output energy profile. The differences measured between first generation free discharge systems and modern square pulse systems may have important clinical consequences in terms of different light-tissue interactions and hence clinical efficacy and safety. IPL manufacturers should provide time-resolved spectroscopy graphs to users.

  20. Application of time-resolved glucose concentration photoacoustic signals based on an improved wavelet denoising

    Science.gov (United States)

    Ren, Zhong; Liu, Guodong; Huang, Zhen

    2014-10-01

    Real-time monitoring of blood glucose concentration (BGC) is a great important procedure in controlling diabetes mellitus and preventing the complication for diabetic patients. Noninvasive measurement of BGC has already become a research hotspot because it can overcome the physical and psychological harm. Photoacoustic spectroscopy is a well-established, hybrid and alternative technique used to determine the BGC. According to the theory of photoacoustic technique, the blood is irradiated by plused laser with nano-second repeation time and micro-joule power, the photoacoustic singals contained the information of BGC are generated due to the thermal-elastic mechanism, then the BGC level can be interpreted from photoacoustic signal via the data analysis. But in practice, the time-resolved photoacoustic signals of BGC are polluted by the varities of noises, e.g., the interference of background sounds and multi-component of blood. The quality of photoacoustic signal of BGC directly impacts the precision of BGC measurement. So, an improved wavelet denoising method was proposed to eliminate the noises contained in BGC photoacoustic signals. To overcome the shortcoming of traditional wavelet threshold denoising, an improved dual-threshold wavelet function was proposed in this paper. Simulation experimental results illustrated that the denoising result of this improved wavelet method was better than that of traditional soft and hard threshold function. To varify the feasibility of this improved function, the actual photoacoustic BGC signals were test, the test reslut demonstrated that the signal-to-noises ratio(SNR) of the improved function increases about 40-80%, and its root-mean-square error (RMSE) decreases about 38.7-52.8%.

  1. Photoluminescence, time-resolved emission and photoresponse of plasma-modified porous silicon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Benyahia, Be., E-mail: benyahiabedra@hotmail.com [Unité de Développement de la Technologie du Silicium, 2 Boulevard Frantz Fanon, B.P. 140, Alger-7 Merveilles, Algiers 16200 (Algeria); Guerbous, L. [Centre de Recherche Nucléaire d' Alger, 2 Boulevard Frantz Fanon, B.P. 399, Alger-Gare, Algiers 16000 (Algeria); Gabouze, N.; Mahmoudi, Br. [Unité de Développement de la Technologie du Silicium, 2 Boulevard Frantz Fanon, B.P. 140, Alger-7 Merveilles, Algiers 16200 (Algeria)

    2013-07-01

    Photoluminescence and photoelectrical study on plasma-modified porous silicon (PS) thin films is presented. Porous silicon passivated by hydrocarbon groups (CH{sub x}) shows an intense broad and stable photoluminescence (PL) band centered at 623 nm whereas the maximum of the photosensitivity spectrum is placed around 400 nm. Along with its potential utilization for silicon-based light emitters' fabrication, it could also represent an appealing option for the improvement of energy conversion efficiency in silicon-based solar cells whether by using its luminescence properties (photon down-conversion) or the excess photocurrent produced by an improved high-energy photon's absorption. Excitation spectra (PLE) under steady-state conditions are reported. PLE shows that visible PL is excited by light from UV region. The time-resolved photoluminescence of CH{sub x}/PS in the range of some tenth of μs are investigated at room temperature. The PL decay line shape, in CH{sub x}/PS is well described by stretched exponential. The photosensitivity spectroscopy shows a significant increase of absorption at high photon energy excitation. - Highlights: • Coating porous silicon (PS) by hydrocarbon (CH{sub x}) reduces nonradiative transition. • Drop of the photoluminescence (PL) intensity. • The PL of CH{sub x}/PS is due to radiative transitions at 1.8 and 1.87 eV. • Photosensitivity revealed an excess spectral response (SR) at high-energy excitation. • For photovoltaic PL and SR could be used for the evolution of the silicon solar cells.

  2. THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Trichas, Markos; Green, Paul J.; Aldcroft, Tom; Kim, Dong-Woo; Mossman, Amy [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Silverman, John D. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568 (Japan); Barkhouse, Wayne [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Cameron, Robert A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Constantin, Anca [Department of Physics and Astronomy, James Madison University, PHCH, Harrisonburg, VA 22807 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1 (Canada); Foltz, Craig [Division of Astronomical Sciences, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230 (United States); Haggard, Daryl [Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Jannuzi, Buell T. [NOAO, Kitt Peak National Observatory, Tucson, AZ 85726 (United States); Marshall, Herman L. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Perez, Laura M. [Department of Astronomy, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125 (United States); Romero-Colmenero, Encarni [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Ruiz, Angel [Osservatorio Astronomico di Brera-INAF, Milan (Italy); Smith, Malcolm G., E-mail: mtrichas@cfa.harvard.edu [Cerro Tololo Interamerican Observatory, La Serena (Chile); and others

    2012-06-01

    From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5 m, SAAO/1.9 m, WIYN 3.5 m, CTIO/4 m, KPNO/4 m, Magellan/6.5 m, MMT/6.5 m, and Gemini/8 m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z {approx} 5.5 and galaxies out to z {approx} 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While {approx}58% of X-ray Seyferts (10{sup 42} erg s{sup -1} < L{sub 2-10keV} <10{sup 44} erg s{sup -1}) require a starburst event (>5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L{sub 2-10keV} >10{sup 44} erg s{sup -1}) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO

  3. Broadband radiometer

    Science.gov (United States)

    Cannon, T.W.

    1994-07-26

    A broadband radiometer is disclosed including (a) an optical integrating sphere having generally spherical integrating chamber and an entry port for receiving light (e.g., having visible and ultraviolet fractions), (b) a first optical radiation detector for receiving light from the sphere and producing an electrical output signal corresponding to broadband radiation, (c) a second optical radiation detector for receiving light from the sphere and producing an electrical output signal corresponding to a predetermined wavelength fraction of the broadband radiation, and (d) an output for producing an electrical signal which is proportional to the difference between the two electrical output signals. The radiometer is very useful, for example, in measuring the absolute amount of ultraviolet light present in a given light sample. 8 figs.

  4. Broadband enhancement of local density of states using silicon-compatible hyperbolic metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu; Inampudi, Sandeep; Capretti, Antonio [Department of Electrical and Computer Engineering and Photonics Center, Boston University, 8 Saint Mary' s Street Boston, Massachusetts 02215 (United States); Sugimoto, Hiroshi [Department of Electrical and Computer Engineering and Photonics Center, Boston University, 8 Saint Mary' s Street Boston, Massachusetts 02215 (United States); Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501 (Japan); Fujii, Minoru [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501 (Japan); Dal Negro, Luca, E-mail: dalnegro@bu.edu [Department of Electrical and Computer Engineering and Photonics Center, Boston University, 8 Saint Mary' s Street Boston, Massachusetts 02215 (United States); Division of Materials Science and Engineering, Boston University, 15 Saint Mary' s Street, Brookline, Massachusetts 02446 (United States)

    2015-06-15

    Light emitting silicon quantum dots by colloidal synthesis were uniformly spin-coated into a 20 nm-thick film and deposited atop a hyperbolic metamaterial of alternating TiN and SiO{sub 2} sub-wavelength layers. Using steady-state and time-resolved photoluminescence spectroscopy as a function of the emission wavelength in partnership with rigorous electromagnetic modeling of dipolar emission, we demonstrate enhanced Local Density of States and coupling to high-k modes in a broad spectral range. These findings provide an alternative approach for the engineering of novel Si-compatible broadband sources that leverage the control of radiative transitions in hyperbolic metamaterials and the flexibility of the widespread Si platform.

  5. [Time-Resolved XEOL Experiment System on BL14W1 at SSRF].

    Science.gov (United States)

    Zhang, Zhao-hong; Jiang, Zheng; Xue, Song; Zheng, Li-fang

    2015-08-01

    A novel time-resolved X-ray excited optical luminescence (TRXEOL) experiment system was developed for X ray absorption fine structure spectroscopy(XAFS) beamline at Shanghai Synchrotron Radiation Facility (SSRF). The TRXEOL system is composed of three parts: timing system, spectrometer system and nuclear instrument module (NIM) system. These three systems were integrated to measure and record the optical luminescence from the sample excited by the synchrotron X-ray pulses, according to the time-correlated single photon counting methodology. It's the first time in the domestic synchrotron radiation facilities to achieve TRXEOL experiment using the synchrotron X-ray pulses and the time structure of the storage ring. In this work, a SSRF-self-developed timing system was used, which is based on the Field programmable Gate Array and the high-speed serial communication technology. The timing system can provide trigger pulse synchronized with the X-ray pulse. The timing jitter is about 6 ps, and the timing delay resolution is 5 ps. The NIM system is the core of the TRXEOL experiment system, it has three main modules: the Constant Fraction Discriminator (CFD), the Time to Amplitude Converter (TAC) and the Multi-Channel Analyzer (MCA). During one excitation circle, the spectrometer and the Photomultiplier Tube detector translate the induced luminescence of the sample excited by a single X-ray pulse into electrical pulse. The CFD module eliminates the timing walk larger than 50 ps induced by the amplitude of the electrical pulse. The TAC module calculates the time interval between the timing trigger pulse and the luminescence electrical pulse, and converts the interval into proportional amplitude of voltage. After plenty of circles, the MCA module gets the luminescence decay curve by recording and analyzing the voltage signals. And the data acquisition system gets the TRXEOL spectra by scanning the spectrometer and acquiring the frequency of the voltage pulses from the TAC

  6. Nanosecond Time Resolved and Steady State Infrared Studies of Photoinduced Decomposition of TATB at Ambient and Elevated Pressures

    Science.gov (United States)

    Glascoe, Elizabeth A.; Zaug, Joseph M.; Armstrong, Michael R.; Crowhurst, Jonathan C.; Grant, Christian D.; Fried, Laurence E.

    2009-06-01

    The timescale and/or products of photo-induced decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were investigated at ambient and elevated pressures. Ultrafast time-resolved infrared and steady state Fourier transform IR (FTIR) spectroscopies were used to probe TATB and its products after photoexcitation with a 5 nanosecond pulse of 532 nm light. At ambient pressure, transient spectra of TATB indicate that the molecule has significantly decomposed within 60 nanoseconds; transient spectra also indicate that formation of CO2, an observed decomposition product, is complete within 30-40 microseconds. Comparison of steady-state FTIR spectra obtained at ambient and elevated pressure (ca. 8 GPa) indicate that the decomposition products vary with pressure and only the high pressure decomposition produces water.

  7. Towards Solvation of a Chiral Alpha-Hydroxy Ester: Broadband Chirp and Narrow Band Cavity Fouirier Transform Microwave Spectroscopy of Methyl Lactate-Water Clusters

    Science.gov (United States)

    Thomas, Javix; Sukhorukov, Oleksandr; Jaeger, Wolfgang; Xu, Yunjie

    2013-06-01

    Methyl lactate (ML), a chiral alpha-hydroxy ester, has attracted much attention as a prototype system in studies of chirality transfer,[1] solvation effects on chiroptical signatures,[2] and chirality recognition.[3] It has multiple functional groups which can serve both as a hydrogen donor and acceptor. By applying rotational spectroscopy and high level ab initio calculations, we examine the delicate competition between inter- and intramolecular hydrogen-bonding in the ML-water clusters. Broadband rotational spectra obtained with a chirp Fourier transform microwave (FTMW) spectrometer, reveal that the insertion conformations are the most favourable ones in the binary and ternary solvated complexes. In the insertion conformations, the water molecule(s) inserts itself (themselves) into the existing intramolecular hydrogen-bonded ring formed between the alcoholic hydroxyl group and the oxygen of the carbonyl group of ML. The final frequency measurements have been carried out using a cavity based FTMW instrument where internal rotation splittings due to the ester methyl group have also been detected. A number of insertion conformers with subtle structural differences for both the binary and ternary complexes have been identified theoretically. The interconversion dynamics of these conformers and the identification of the most favorable conformers will be discussed. 1. C. Merten, Y. Xu, Angew. Chem. Int. Ed., 2013, 52, 2073 -2076. 2. M. Losada, Y. Xu, Phys. Chem. Chem. Phys., 2007, 9, 3127-3135; Y. Liu, G. Yang, M. Losada, Y. Xu, J. Chem. Phys., 2010, 132, 234513/1-11. 3. A. Zehnacker, M. Suhm, Angew. Chem. Int. Ed. 2008, 47, 6970 - 6992.

  8. Trans-cranial infrared laser stimulation induces hemodynamic and metabolic response measured by broadband near infrared spectroscopy in vivo on human forehead (Conference Presentation)

    Science.gov (United States)

    Wang, Xinlong; Nalawade, Sahil Sunil; Reddy, Divya Dhandapani; Tian, Fenghua; Gonzalez-Lima, F.; Liu, Hanli

    2017-02-01

    Transcranial infrared laser stimulation (TILS) uses infrared light (lasers or LEDs) for nondestructive and non-thermal photobiomodulation on the human brain. Although TILS has shown its beneficial effects to a variety of neurological and psychological conditions, its physiological mechanism remains unknown. Cytochrome-c-oxidase (CCO), the last enzyme in the electron transportation chain, is proposed to be the primary photoacceptor of this infrared laser. In this study, we wish to validate this proposed mechanism. We applied 8 minutes in vivo TILS on the right forehead of 11 human participants with a 1064-nm laser. Broad-band near infrared spectroscopy (bb-NIRS) from 740-900nm was also employed near the TILS site to monitor hemodynamic and metabolic responses during the stimulation and 5-minute recovery period. For rigorous comparison, we also performed similar 8-min bb-NIR measurements under placebo conditions. A multi-linear regression analysis based on the modified Beer-Lambert law was performed to estimate concentration changes of oxy-hemoglobin (Δ[HbO]), deoxy-hemoglobin (Δ[Hb]), and cytochrome-c-oxidase (Δ[CCO]). We found that TILS induced significant increases of [CCO], [HbO] and a decrease of [Hb] with dose-dependent manner as compared with placebo treatments. Furthermore, strong linear relationships or interplays between [CCO] versus [HbO] and [CCO] versus [Hb] induced by TILS were observed in vivo for the first time. These relationships have clearly revealed close coupling/relationship between the hemodynamic oxygen supply and blood volume versus up-regulation of CCO induced by photobiomodulation. Our results demonstrate the tremendous potential of bb-NIRS as a non-invasive in vivo means to study photobiomodulation mechanisms and perform treatment evaluations of TILS.

  9. Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin 1

    Science.gov (United States)

    Gauden, Magdalena; Crosson, Sean; van Stokkum, I. H. M.; van Grondelle, Rienk; Moffat, Keith; Kennis, John T. M.

    2004-09-01

    The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm-1. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

  10. Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin

    Energy Technology Data Exchange (ETDEWEB)

    Gauden, Magdalena; Crosson, Sean; van Stokkum, I.H.; Grondelle, Rienkvan; Moffat, Keith; Kennis, John T. (UC)

    2004-12-13

    The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm{sup -1}. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

  11. Luminescent trimethoprim-polyaminocarboxylate lanthanide complex conjugates for selective protein labeling and time-resolved bioassays

    Science.gov (United States)

    Reddy, D. Rajasekhar; Pedró Rosa, Laura E.; Miller, Lawrence W.

    2011-01-01

    Labeling proteins with long-lifetime emitting lanthanide (III) chelate reporters enables sensitive, time-resolved luminescence bioaffinity assays. Heterodimers of trimethoprim (TMP) covalently linked to various cs124-sensitized, polyaminocarboxylate chelates stably retain lanthanide ions and exhibit quantum yields of europium emission up to 20% in water. A time-resolved, luminescence resonance energy transfer (LRET) assay showed that TMP-polyaminocarboxylates bind to Escherichia coli dihydrofolate reductase (eDHFR) fusion proteins with nanomolar affinity in purified solutions and in bacterial lysates. The ability to selectively impart terbium or europium luminescence to fusion proteins in complex physiological mixtures bypasses the need for specific antibodies and simplifies sample preparation. PMID:21619068

  12. Time-resolved photoluminescence properties of semiconductor quantum dot superlattices of different microcrystal shapes

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Weon-Sik, E-mail: wschae@kbsi.re.kr; Choi, Eunjin; Ku Jung, Yun [Korea Basic Science Institute, Gangneung 210-702 (Korea, Republic of); Jung, Jin-Seung [Department of Chemistry, Gangneung-Wonju National University, Gangneung 210-702 (Korea, Republic of); Lee, Jin-Kyu [Department of Chemistry, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-04-14

    We report time-resolved photoluminescence properties on semiconductor quantum dot (QD) superlattices (SLs) using PL lifetime imaging microscopy at a single particle level. PL lifetime imaging technique clearly reveals that different shaped QD SL microcrystals have different time-resolved PL characteristics. The faceted SL microcrystals consisted of well-organized QDs showed faster recombination rates than those of the spherical microparticles including randomly organized QDs, which can be explained by the different degree of energetic couplings among component QDs due to different packing fraction.

  13. Time-resolved electron transport in quantum-dot systems; Zeitaufgeloester Elektronentransport in Quantendotsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Croy, Alexander

    2010-06-30

    In this thesis the time-resolved electron transport in quantum dot systems was studied. For this two different formalisms were presented: The nonequilibrium Green functions and the generalized quantum master equations. For both formalisms a propagation method for the numerical calculation of time-resolved expectation values, like the occupation and the electron current, was developed. For the demonstration of the propagation method two different question formulations were considered. On the one hand the stochastically driven resonant-level model was studied. On the other hand the pulse-induced transport through a double quantum dot was considered.

  14. Computational time-resolved and resonant x-ray scattering of strongly correlated materials

    Energy Technology Data Exchange (ETDEWEB)

    Bansil, Arun [Northeastern Univ., Boston, MA (United States)

    2016-11-09

    predominantly decays via Auger processes, thereby providing an internal time-scale, which limits intermediate-state processes to timescales of a few femtoseconds. Accordingly, a number of activities directed at modeling K-, L- and M-edge RIXS in correlated materials were also pursused by our CRT. Our research effort supported by this CMCSN grant substantially advanced the understanding of x-ray scattering processes in the time-domain as well as in the more conventional scattering channels, including time-resolved photoemission, and how such processes can be modeled realistically in complex correlated materials more generally. The modeling of relaxation processes involved in time-domain spectroscopies is important also for understanding photoinduced effects such as energy conversion in photosynthesis and solar cell applications, and thus impacts the basic science for energy needs.

  15. Time-resolved analytical methods for liquid/solid interfaces. Progress report, November 1, 1993--October 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Harris, J.M.

    1994-10-31

    A number of chemical phenomena that occur at the boundaries between insulating solids and liquids (adsorption, partition, monolayer self-assembly, catalysis, and chemical reactions) are important to energy-related analytical chemistry. These phenomena are central to the development and understanding of chromatographic methods, solid-phase extraction techniques, immobilized analytical reagents, and optical sensors. The goal of this program, therefore, is to develop surface-sensitive spectroscopies by which chemical kinetics at liquid/solid interfaces can be observed on time-scales from nanoseconds to seconds. In the second year of this program, the authors have used temperature-jump relaxation measurements to monitor adsorption/desorption kinetics at liquid/solid interfaces using Joule heating to compare the adsorption of ions from solution onto C1- and C4-derivatized silica surfaces. They completed a study of rate of migration of covalently-attached ligands on silica surfaces; from the temperature-dependence of the migration, the large energy barrier to migration was estimated. Surface heterogeneity of adsorption sites on silica was characterized by time-resolve fluorescence, and the chemical origins investigated by Si{sup 29} NMR spectroscopy. Surface-enhance Raman and fluorescence spectroscopies were modified to study adsorption and binding to silica surfaces. Molecular dynamics simulations were started to help better understand kinetic barriers to adsorption; ESR probe measurements were launched to measure and compare the chain mobility of silica-attached alkyl ligands.

  16. Time-resolved Imaging of H2 + (D2 +) Nuclear Wave Packets

    Science.gov (United States)

    Ergler, Th.; Rudenko, A.; Feuerstein, B.; Zrost, K.; Schröter, C. D.; Moshammer, R.; Ullrich, J.

    The spatio-temporal evolution of H2 + (D2 +) nuclear wave packets is mapped using time-resolved Coulomb explosion imaging. We visualize the motion of both dissociating and bound parts of the wave packet, observe its dephasing and subsequent revivals. The reconstructed probability density of the wave packet is in good agreement with earlier theoretical predictions.

  17. On the theory of time-resolved x-ray diffraction

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm; Møller, Klaus Braagaard

    2008-01-01

    of the experimental diffraction signal for both types of X-ray sources. We present a simple analysis of time-resolved X-ray scattering for direct bond breaking in diatomic molecules. This essentially analytical approach highlights the relation between the signal and the time-dependent quantum distribution...

  18. Quantitative analysis of time-resolved infrared stimulated luminescence in feldspars

    DEFF Research Database (Denmark)

    Pagonis, Vasilis; Ankjærgaard, Christina; Jain, Mayank

    2016-01-01

    Time-resolved infrared-stimulated luminescence (TR-IRSL) from feldspar samples is of importance in the field of luminescence dating, since it provides information on the luminescence mechanism in these materials. In this paper we present new analytical equations which can be used to analyze TR...

  19. Ambiguities in the interpretation of time-resolved fluorescence anisotropy measurements on lipid vesicle systems

    NARCIS (Netherlands)

    Langen, H. van; Levine, Y.K.; Ameloot, M.; Pottel, H.

    1987-01-01

    Analysis of time-resolved fluorescence anisotropy measurements on DPH and TMA-DPH in POPC vesicles with and without cholesterol in terms of the rotational diffusion model shows two distinct χr2 minima which are statistically equivalent. This is explained by the fact that the anisotropy decay

  20. Expected resolution and detectability of adenocarcinoma tumors within human breast in time-resolved images

    Science.gov (United States)

    Gandjbakhche, Amir H.; Nossal, Ralph J.; Dadmarz, Roya; Schwartzentruber, Douglas; Bonner, Robert F.

    1995-04-01

    The prospects for time-resolved optical mammography rests on the ability to detect adenocarcinoma within the breast with sufficient resolution and specificity to compete with X-ray mammography. We characterized the optical properties of an unusually large (6 cm diameter) fresh adenocarcinoma and normal breast tissue (determined by histology to be predominantly adipose tissue) obtained from a patient undergoing mastectomy. Large specimens (5 mm thick and 3 cm wide) allowed the determination of absorption and scattering coefficients and their spatial heterogeneity as probed with a 1 mm diameter laser beam at 633 nm and 800 nm utilizing total reflectance and transmittance measure with integrating spheres. The difference between scattering coefficients of the malignant tumor and those of normal (principally adipose) breast tissue at 633 nm was much greater than the heterogeneity within each sample. This scattering difference is the principal source of contrast, particularly in time-resolved images. However, the high scattering coefficient of normal breast tissue at 633 nm limits the practicality of time-resolved mammography of a human breast compressed to 5 cm. Although the scattering coefficient of the normal breast tissue decreases at 800 nm, the differences between the optical properties of normal and abnormal breast tissue also are reduced. We used these empirical results in theoretical expressions obtained from random walk theory to quantify the expected resolution, contrast, and the detected intensity of 3, 6, and 9 mm tumors within otherwise homogeneous human breasts as a function of the gating-time of time-resolved optical mammography.

  1. Time-resolved electron spectrum diagnostics for a free-electron laser

    NARCIS (Netherlands)

    Gillespie, W. A.; MacLeod, A. M.; Martin, P. F.; van der Meer, A. F. G.; van Amersfoort, P. W.

    1996-01-01

    Time-resolved electron-beam diagnostics have been developed for use with free-electron lasers (FELs) and associated electron sources, based on the techniques of secondary electron emission and optical transition radiation (OTR). The 32-channel OTR detector forms part of a high-resolution (0.18%)

  2. Time-resolved fluorescence analysis of the mobile flavin cofactor in ...

    Indian Academy of Sciences (India)

    Conformational heterogeneity of the FAD cofactor in -hydroxybenzoate hydroxylase (PHBH) was investigated with time-resolved polarized flavin fluorescence. For binary enzyme/substrate (analogue) complexes of wild-type PHBH and Tyr222 mutants, crystallographic studies have revealed two distinct flavin conformations ...

  3. Time-resolved proton polarisation (TPP) images tyrosyl radical sites in bovine liver catalase.

    Science.gov (United States)

    Zimmer, Oliver; Jouve, Hélène M.; Stuhrmann, Heinrich B.

    2017-05-01

    A differentiation between dynamic polarised protons close to tyrosyl radical sites in catalase and those of the bulk is achieved by time-resolved polarised neutron scattering. Three radical sites, all of them being close to the molecular centre and the heme, appear to be equally possible. Among these is tyr-369 the radial site of which had previously been proven by EPR.

  4. Evolution of a Rippled Membrane during Phospholipase A2 Hydrolysis Studied by Time-Resolved AFM

    DEFF Research Database (Denmark)

    Leidy, Chad; Mouritsen, Ole G.; Jørgensen, Kent

    2004-01-01

    The sensitivity of phospholipase A2 (PLA2) for lipid membrane curvature is explored by monitoring, through time-resolved atomic force microscopy, the hydrolysis of supported double bilayers in the ripple phase. The ripple phase presents a corrugated morphology. PLA2 is shown to have higher activity...

  5. Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources

    Energy Technology Data Exchange (ETDEWEB)

    Rutherford, Michael E.; Chapman, David J.; White, Thomas G. [Imperial College London, London (United Kingdom); Drakopoulos, Michael [Diamond Light Source, I12 Joint Engineering, Environmental, Processing (JEEP) Beamline, Didcot, Oxfordshire (United Kingdom); Rack, Alexander [European Synchrotron Radiation Facility, Grenoble (France); Eakins, Daniel E., E-mail: d.eakins@imperial.ac.uk [Imperial College London, London (United Kingdom)

    2016-03-24

    Scintillator performance in time-resolved, hard, indirect detection X-ray studies on the sub-microsecond timescale at synchrotron light sources is reviewed, modelled and examined experimentally. LYSO:Ce is found to be the only commercially available crystal suitable for these experiments. The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits)

  6. Fluctuations between high- and low-modularity topology in time-resolved functional connectivity.

    Science.gov (United States)

    Fukushima, Makoto; Betzel, Richard F; He, Ye; de Reus, Marcel A; van den Heuvel, Martijn P; Zuo, Xi-Nian; Sporns, Olaf

    2017-08-17

    Modularity is an important topological attribute for functional brain networks. Recent human fMRI studies have reported that modularity of functional networks varies not only across individuals being related to demographics and cognitive performance, but also within individuals co-occurring with fluctuations in network properties of functional connectivity, estimated over short time intervals. However, characteristics of these time-resolved functional networks during periods of high and low modularity have remained largely unexplored. In this study we investigate basic spatiotemporal properties of time-resolved networks in the high and low modularity periods during rest, with a particular focus on their spatial connectivity patterns, temporal homogeneity and test-retest reliability. We show that spatial connectivity patterns of time-resolved networks in the high and low modularity periods are represented by increased and decreased dissociation of the default mode network module from task-positive network modules, respectively. We also find that the instances of time-resolved functional connectivity sampled from within the high (respectively, low) modularity period are relatively homogeneous (respectively, heterogeneous) over time, indicating that during the low modularity period the default mode network interacts with other networks in a variable manner. We confirmed that the occurrence of the high and low modularity periods varies across individuals with moderate inter-session test-retest reliability and that it is correlated with previously-reported individual differences in the modularity of functional connectivity estimated over longer timescales. Our findings illustrate how time-resolved functional networks are spatiotemporally organized during periods of high and low modularity, allowing one to trace individual differences in long-timescale modularity to the variable occurrence of network configurations at shorter timescales. Copyright © 2017 The Authors

  7. Mix and Inject: Reaction Initiation by Diffusion for Time-Resolved Macromolecular Crystallography

    Directory of Open Access Journals (Sweden)

    Marius Schmidt

    2013-01-01

    Full Text Available Time-resolved macromolecular crystallography unifies structure determination with chemical kinetics, since the structures of transient states and chemical and kinetic mechanisms can be determined simultaneously from the same data. To start a reaction in an enzyme, typically, an initially inactive substrate present in the crystal is activated. This has particular disadvantages that are circumvented when active substrate is directly provided by diffusion. However, then it is prohibitive to use macroscopic crystals because diffusion times become too long. With small micro- and nanocrystals diffusion times are adequately short for most enzymes and the reaction can be swiftly initiated. We demonstrate here that a time-resolved crystallographic experiment becomes feasible by mixing substrate with enzyme nanocrystals which are subsequently injected into the X-ray beam of a pulsed X-ray source.

  8. Identifiability of models for time-resolved fluorescence with underlying distributions of rate constants.

    Science.gov (United States)

    Boens, Noël; Van der Auweraer, Mark

    2014-02-01

    The deterministic identifiability analysis of photophysical models for the kinetics of excited-state processes, assuming errorless time-resolved fluorescence data, can verify whether the model parameters can be determined unambiguously. In this work, we have investigated the identifiability of several uncommon models for time-resolved fluorescence with underlying distributions of rate constants which lead to non-exponential decays. The mathematical functions used here for the description of non-exponential fluorescence decays are the stretched exponential or Kohlrausch function, the Becquerel function, the Förster type energy transfer function, decay functions associated with exponential, Gaussian and uniform distributions of rate constants, a decay function with extreme sub-exponential behavior, the Mittag-Leffler function and Heaviside's function. It is shown that all the models are uniquely identifiable, which means that for each specific model there exists a single parameter set that describes its associated fluorescence δ-response function.

  9. A fluorescence LIDAR sensor for hyper-spectral time-resolved remote sensing and mapping.

    Science.gov (United States)

    Palombi, Lorenzo; Alderighi, Daniele; Cecchi, Giovanna; Raimondi, Valentina; Toci, Guido; Lognoli, David

    2013-06-17

    In this work we present a LIDAR sensor devised for the acquisition of time resolved laser induced fluorescence spectra. The gating time for the acquisition of the fluorescence spectra can be sequentially delayed in order to achieve fluorescence data that are resolved both in the spectral and temporal domains. The sensor can provide sub-nanometric spectral resolution and nanosecond time resolution. The sensor has also imaging capabilities by means of a computer-controlled motorized steering mirror featuring a biaxial angular scanning with 200 μradiant angular resolution. The measurement can be repeated for each point of a geometric grid in order to collect a hyper-spectral time-resolved map of an extended target.

  10. A direct electron detector for time-resolved MeV electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vecchione, T.; Denes, P.; Jobe, R. K.; Johnson, I. J.; Joseph, J. M.; Li, R. K.; Perazzo, A.; Shen, X.; Wang, X. J.; Weathersby, S. P.; Yang, J.; Zhang, D.

    2017-03-01

    The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μmμm spatial resolution and less than 20 analogue-to-digital converter count RMS pixel noise. The unique capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.

  11. Sub-nanosecond time-resolved near-field scanning magneto-optical microscope.

    Science.gov (United States)

    Rudge, J; Xu, H; Kolthammer, J; Hong, Y K; Choi, B C

    2015-02-01

    We report on the development of a new magnetic microscope, time-resolved near-field scanning magneto-optical microscope, which combines a near-field scanning optical microscope and magneto-optical contrast. By taking advantage of the high temporal resolution of time-resolved Kerr microscope and the sub-wavelength spatial resolution of a near-field microscope, we achieved a temporal resolution of ∼50 ps and a spatial resolution of microscope, the magnetic field pulse induced gyrotropic vortex dynamics occurring in 1 μm diameter, 20 nm thick CoFeB circular disks has been investigated. The microscope provides sub-wavelength resolution magnetic images of the gyrotropic motion of the vortex core at a resonance frequency of ∼240 MHz.

  12. Time-resolved PEEM measurements on single-crystalline Fe-structures

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Alexander; Wiemann, Carsten; Cramm, Stefan; Schneider, Claus M. [Forschungszentrum Juelich, Institut fuer Festkoerperforschung IFF-9, 52425 Juelich (Germany)

    2008-07-01

    Time-resolved photo-electron emission microscopy (TR-PEEM) provides a method for investigating the spatial and temporal magnetodynamics of micron-sized magnetic elements. By the use of e-beam evaporation thin films of (100)-oriented Iron in bcc-structure can be epitaxially grown on GaAs substrates with a Silver buffer layer. Due to their single-crystallinity the films exhibit a four-fold in-plane magnetocrystalline anisotropy. The films have been microstructured by lithographic techniques and the micromagnetic response on a short magnetic field pulse was investigated by the TR-PEEM technique. Compared to well-studied polycrystalline Permalloy samples the magnetocrystalline anisotropy gives rise to additional terms in the effective magnetic field, leading to different magnetodynamic behaviour. Results of the time-resolved measurements are presented and compared to those of anisotropy-free Permalloy structures.

  13. Theoretical Study of Time-Resolved Fluorescence Anisotropy from Coupled Chromophore Pairs

    CERN Document Server

    Matro, A; Matro, Alexander; Cina, Jeffrey A.

    1994-01-01

    Calculations of time-resolved fluorescence anisotropy from a pair of chromophores coupled by an excitation transfer interaction are presented. For the purpose of investigating the effects of nuclear motion on the energy transfer and anisotropy, an illustrative model is developed that provides each chromophore with a single intramolecular vibrational mode. Account is taken of non-instantaneous excitation and time- and frequency-resolved detection. Effects of excitation pulse duration, detection window duration and frequency resolution, and excitation transfer coupling strength on the time-resolved anisotropy are examined in detail. Effects of vibrational relaxation and dephasing are also examined using a simplified Redfield description of the effects of coupling to a thermal bath.

  14. Intracellular Monitoring of AS1411 Aptamer by Time-Resolved Microspectrofluorimetry and Fluorescence Imaging.

    Science.gov (United States)

    Kočišová, Eva; Praus, Petr; Bok, Jiří; Bonneau, Stéphanie; Sureau, Franck

    2015-09-01

    Time-resolved microspectrofluorimetry and fluorescence microscopy imaging-two complementary fluorescence techniques-provide important information about the intracellular distribution, level of uptake and binding/interactions inside living cell of the labeled molecule of interest. They were employed to monitor the "fate" of AS1411 aptamer labeled by ATTO 425 in human living cells. Confocal microspectrofluorimeter adapted for time-resolved intracellular fluorescence measurements by using a phase-modulation principle with homodyne data acquisition was employed to obtain emission spectra and to determine fluorescence lifetimes in U-87 MG tumor brain cells and Hs68 non-tumor foreskin cells. Acquired spectra from both the intracellular space and the reference solutions were treated to observe the aptamer localization and its interaction with biological structures inside the living cell. The emission spectra and the maximum emission wavelengths coming from the cells are practically identical, however significant lifetime lengthening was observed for tumor cell line in comparison to non-tumor one.

  15. A Time-Resolved Dynamic Stall Investigation Based On Coherent Structure Analysis

    OpenAIRE

    Mulleners, Karen; Raffel, Markus

    2010-01-01

    Dynamic stall on an airfoil comprises a series of complex aerodynamic phenomena in response to an unsteady change of the angle of attack. It is accompanied by a lift overshoot and delayed massive flow separation with respect to static stall. The classical hallmark of the dynamic stall phenomenon is the dynamic stall vortex. The flow over an oscillating OA209 airfoil under dynamic stall conditions was investigated by means of unsteady surface pressure measurements and time-resolved particle im...

  16. Time resolved analysis of water drainage in porous asphalt concrete using neutron radiography.

    Science.gov (United States)

    Poulikakos, L D; Sedighi Gilani, M; Derome, D; Jerjen, I; Vontobel, P

    2013-07-01

    Porous asphalt as a road surface layer controls aquaplaning as rain water can drain through its highly porous structure. The process of water drainage through this permeable layer is studied using neutron radiography. Time-resolved water configuration and distribution within the porous structure are reported. It is shown that radiography depicts the process of liquid water transport within the complex geometry of porous asphalt, capturing water films, filled dead end pores and water islands. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Simulations of Time-Resolved X-Ray Diffraction in Laue Geometry

    OpenAIRE

    Lings, B.; DeCamp, M. F.; Reis, D.A.; Fahy, S.; Wark, J. S.

    2005-01-01

    A method of computer simulation of Time-Resolved X-ray Diffraction (TRXD) in asymmetric Laue (transmission) geometry with an arbitrary propagating strain perpendicular to the crystal surface is presented. We present two case studies for possible strain generation by short-pulse laser irradiation: (i) a thermoelastic-like analytic model; (ii) a numerical model including effects of electron-hole diffusion, Auger recombination, deformation potential and thermal diffusion. A comparison with recen...

  18. Bimodal Exciplex Formation in Bimolecular Photoinduced Electron Transfer Revealed by Ultrafast Time-Resolved Infrared Absorption

    OpenAIRE

    Koch, Marius; Licari, Giuseppe Léonardo; Vauthey, Eric

    2015-01-01

    The dynamics of a moderately exergonic photoinduced charge separation has been investigated by ultrafast time-resolved infrared absorption with the dimethylanthracene/phthalonitrile donor/acceptor pair in solvents covering a broad range of polarity. A distinct spectral signature of an exciplex could be identified in the −C≡N stretching region. On the basis of quantum chemistry calculations, the 4–5 times larger width of this band compared to those of the ions and of the locally excited donor ...

  19. Singular value decomposition as a tool for background corrections in time-resolved XFEL scattering data

    DEFF Research Database (Denmark)

    Haldrup, Kristoffer

    2014-01-01

    The development of new X-ray light sources, XFELs, with unprecedented time and brilliance characteristics has led to the availability of very large datasets with high time resolution and superior signal strength. The chaotic nature of the emission processes in such sources as well as entirely nov...... on singular-value decomposition of no-signal subsets of acquired datasets in combination with model inputs and appears generally applicable to time-resolved X-ray diffuse scattering experiments....

  20. Technical note: Time-resolved immunofluorometric assay for growth hormone in ruminants

    DEFF Research Database (Denmark)

    Løvendahl, P.; Adamsen, J.; Lund, Regina Teresa

    2003-01-01

    for 4 h at 25degreesC. Plates were then washed six times, incubated for 5 to 10 min with 250 muL of enhancement solution, and fluorescence read with a time-resolved fluorometer. The sensitivity of the assay was 0.1 ng/mL, and the working range was 0.2 to 200 ng/mL. Recovery of quantitative amounts...

  1. Time-resolved photoemission electron microscopy imaging of mode coupling between three interacting magnetic vortices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiao; Cheng, X. M., E-mail: xcheng@brynmawr.edu [Department of Physics, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010 (United States); Keavney, D. J. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Asmat-Uceda, M.; Buchanan, K. S. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States); Melikyan, A. [American Physical Society, Ridge, New York 11961 (United States)

    2014-09-08

    The interactions between three magnetic vortices in a planar equilateral triangular arrangement were studied by time-resolved photoemission electron microscopy. The gyrotropic resonance frequencies of the three individual vortices in the tri-disk system are different from one another and also shifted from that of an isolated vortex by as much as 12%. A comparison with analytical calculations and numerical simulations shows that the observed frequency shifts result from the dipolar interaction between the vortices.

  2. Time-resolved measurement of Landau-Zener tunneling in periodic potentials

    OpenAIRE

    Zenesini, A.; Lignier, H.; Tayebirad, G.; Radogostowicz, J; Ciampini, D; Mannella, R.; Wimberger, S.; Morsch, O.; Arimondo, E.

    2009-01-01

    We report time-resolved measurements of Landau-Zener tunneling of Bose-Einstein condensates in accelerated optical lattices, clearly resolving the step-like time dependence of the band populations. Using different experimental protocols we were able to measure the tunneling probability both in the adiabatic and in the diabatic bases of the system. We also experimentally determine the contribution of the momentum width of the Bose condensates to the width of the tunneling steps and discuss the...

  3. Fast single photon avalanche photodiode-based time-resolved diffuse optical tomography scanner

    Science.gov (United States)

    Mu, Ying; Niedre, Mark

    2015-01-01

    Resolution in diffuse optical tomography (DOT) is a persistent problem and is primarily limited by high degree of light scatter in biological tissue. We showed previously that the reduction in photon scatter between a source and detector pair at early time points following a laser pulse in time-resolved DOT is highly dependent on the temporal response of the instrument. To this end, we developed a new single-photon avalanche photodiode (SPAD) based time-resolved DOT scanner. This instrument uses an array of fast SPADs, a femto-second Titanium Sapphire laser and single photon counting electronics. In combination, the overall instrument temporal impulse response function width was 59 ps. In this paper, we report the design of this instrument and validate its operation in symmetrical and irregularly shaped optical phantoms of approximately small animal size. We were able to accurately reconstruct the size and position of up to 4 absorbing inclusions, with increasing image quality at earlier time windows. We attribute these results primarily to the rapid response time of our instrument. These data illustrate the potential utility of fast SPAD detectors in time-resolved DOT. PMID:26417526

  4. Wake losses from averaged and time-resolved power measurements at full scale wind turbines

    Science.gov (United States)

    Castellani, Francesco; Astolfi, Davide; Mana, Matteo; Becchetti, Matteo; Segalini, Antonio

    2017-05-01

    This work deals with the experimental analysis of wake losses fluctuations at full-scale wind turbines. The test case is a wind farm sited on a moderately complex terrain: 4 turbines are installed, having 2 MW of rated power each. The sources of information are the time-resolved data, as collected from the OPC server, and the 10-minutes averaged SCADA data. The objective is to compare the statistical distributions of wake losses for far and middle wakes, as can be observed through the “fast” lens of time-resolved data, for certain selected test-case time series, and through the “slow” lens of SCADA data, on a much longer time basis that allow to set the standards of the mean wake losses along the wind farm. Further, time-resolved data are used for an insight into the spectral properties of wake fluctuations, highlighting the role of the wind turbine as low-pass filter. Summarizing, the wind rose, the layout of the site and the structure of the data sets at disposal allow to study middle and far wake behavior, with a “slow” and “fast” perspective.

  5. A New Approach to Time-Resolved 3D-PTV

    Science.gov (United States)

    Boomsma, Aaron; Troolin, Dan; Bjorkquist, Dan; TSI Inc Team

    2017-11-01

    Volumetric three-component velocimetry via particle tracking is a powerful alternative to TomoPIV. It has been thoroughly documented that compared to TomoPIV, particle tracking velocimetry (PTV) methods (whether 2D or 3D) better resolve regions of high velocity gradient, identify fewer ghost particles, and are less computationally demanding, which results in shorter processing times. Recently, 3D-PTV has seen renewed interest in the PIV community with the availability of time-resolved data. Of course, advances in hardware are partly to thank for that availability-higher speed cameras, more effective memory management, and higher speed lasers. But in software, algorithms that utilize time resolved data to improve 3D particle reconstruction and particle tracking are also under development and advancing (e.g. shake-the-box, neighbor tracking reconstruction, etc.). .In the current study, we present a new 3D-PTV method that incorporates time-resolved data. We detail the method, its performance in terms of particle identification and reconstruction error and their relation to varying seeding densities, as well as computational performance.

  6. Hydrodynamic Radii of Ranibizumab, Aflibercept and Bevacizumab Measured by Time-Resolved Phosphorescence Anisotropy.

    Science.gov (United States)

    Hirvonen, Liisa M; Fruhwirth, Gilbert O; Srikantha, Nishanthan; Barber, Matthew J; Neffendorf, James E; Suhling, Klaus; Jackson, Timothy L

    2016-08-01

    To measure the hydrodynamic radii of intravitreal anti-VEGF drugs ranibizumab, aflibercept and bevacizumab with μs time-resolved phosphorescence anisotropy. Ruthenium-based dye Ru(bpy)2(mcbpy - O - Su - ester)(PF6)2, whose lifetime of several hundred nanoseconds is comparable to the rotational correlation time of these drugs in buffer, was used as a label. The hydrodynamic radii were calculated from the rotational correlation times of the Ru(bpy)2(mcbpy - O - Su - ester)(PF6)2-labelled drugs obtained with time-resolved phosphorescence anisotropy measurements in buffer/glycerol solutions of varying viscosity. The measured radii of 2.76±0.04 nm for ranibizumab, 3.70±0.03 nm for aflibercept and 4.58±0.01 nm for bevacizumab agree with calculations based on molecular weight and other experimental measurements. Time-resolved phosphorescence anisotropy is a relatively simple and straightforward method that allows experimental measurement of the hydrodynamic radius of individual proteins, and is superior to theoretical calculations which cannot give the required accuracy for a particular protein.

  7. Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources.

    Science.gov (United States)

    Rutherford, Michael E; Chapman, David J; White, Thomas G; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E

    2016-05-01

    The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits).

  8. Timely resolved measurements on CdSe nanoparticles; Zeitaufgeloeste Messungen an CdSe Nanopartikeln

    Energy Technology Data Exchange (ETDEWEB)

    Holt, B.E. von

    2006-06-06

    By means of infrared spectroscopy the influence of the organic cover on structure and dynamics of CdSe nanoparticles was studied. First a procedure was developed, which allows to get from the static infrared spectrum informations on the quality of the organic cover and the binding behaviour of the ligands. On qualitatively high-grade and well characterized samples thereafter the dynamics of the lowest-energy electron level 1S{sub e} was time-resolvedly meausred in thew visible range. As reference served CdSe TOPO, which was supplemented by samples with the ligands octanthiole, octanic acid, octylamine, naphthoquinone, benzoquinone, and pyridine. The studied nanoparticles had a diameter of 4.86 nm. By means of the excitation-scanning or pump=probe procedure first measurements in the picosecond range were performed. The excitation wavelengths were thereby spectrally confined and so chosen that selectively the transitions 1S{sub 3/2}-1S-e and 1P{sub 3/2}-1P{sub e} but not the intermediately lyingt transition 2S{sub 3/2}-1S{sub e} were excited. The excitation energies were kept so low that the excitation of several excitons in one crystal could be avoided. The scanning wavelength in the infrared corresponded to the energy difference between the electron levels 1S{sub e} and 1P{sub e}. The transients in the picosecond range are marked by a steep increasement of the signal, on which a multi-exponential decay follows. The increasement, which reproduces the popiulation of the excited state, isa inependent on the choice of the ligands. The influence of the organic cover is first visible in the different decay times of the excited electron levels. the decay of the measurement signal of CdSe TOPO can be approximatively described by three time constants: a decay constant in the early picosecond region, a time constant around hundert picoseconds, and a time constant of some nanoseconds. At increasing scanning wavelength the decay constants become longer. By directed excitation

  9. Prospective time-resolved LCA of fully electric supercap vehicles in Germany.

    Science.gov (United States)

    Zimmermann, Benedikt M; Dura, Hanna; Baumann, Manuel J; Weil, Marcel R

    2015-07-01

    The ongoing transition of the German electricity supply toward a higher share of renewable and sustainable energy sources, called Energiewende in German, has led to dynamic changes in the environmental impact of electricity over the last few years. Prominent scenario studies predict that comparable dynamics will continue in the coming decades, which will further improve the environmental performance of Germany's electricity supply. Life cycle assessment (LCA) is the methodology commonly used to evaluate environmental performance. Previous LCA studies on electric vehicles have shown that the electricity supply for the vehicles' operation is responsible for the major part of their environmental impact. The core question of this study is how the prospective dynamic development of the German electricity mix will affect the impact of electric vehicles operated in Germany and how LCA can be adapted to analyze this impact in a more robust manner. The previously suggested approach of time-resolved LCA, which is located between static and dynamic LCA, is used in this study and compared with several static approaches. Furthermore, the uncertainty issue associated with scenario studies is addressed in general and in relation to time-resolved LCA. Two scenario studies relevant to policy making have been selected, but a moderate number of modifications have been necessary to adapt the data to the requirements of a life cycle inventory. A potential, fully electric vehicle powered by a supercapacitor energy storage system is used as a generic example. The results show that substantial improvements in the environmental repercussions of the electricity supply and, consequentially, of electric vehicles will be achieved between 2020 and 2031 on the basis of the energy mixes predicted in both studies. This study concludes that although scenarios might not be able to predict the future, they should nonetheless be used as data sources in prospective LCA studies, because in many cases

  10. Theoretical analysis of the time-resolved binary (e, 2e) binding energy spectra on three-body photodissociation of acetone at 195 nm

    Science.gov (United States)

    Yamazaki, M.; Nakayama, S.; Zhu, C. Y.; Takahashi, M.

    2017-11-01

    We report on theoretical progress in time-resolved (e, 2e) electron momentum spectroscopy of photodissociation dynamics of the deuterated acetone molecule at 195 nm. We have examined the predicted minimum energy reaction path to investigate whether associated (e, 2e) calculations meet the experimental results. A noticeable difference between the experiment and calculations has been found at around binding energy of 10 eV, suggesting that the observed difference may originate, at least partly, in ever-unconsidered non-minimum energy paths.

  11. ns-μs Time-Resolved Step-Scan FTIR of ba3 Oxidoreductase from Thermus thermophilus: Protonic Connectivity of w941-w946-w927

    Directory of Open Access Journals (Sweden)

    Antonis Nicolaides

    2016-09-01

    Full Text Available Time-resolved step-scan FTIR spectroscopy has been employed to probe the dynamics of the ba3 oxidoreductase from Thermus thermophilus in the ns-μs time range and in the pH/pD 6–9 range. The data revealed a pH/pD sensitivity of the D372 residue and of the ring-A propionate of heme a3. Based on the observed transient changes a model in which the protonic connectivity of w941-w946-927 to the D372 and the ring-A propionate of heme a3 is described.

  12. Application of a time-resolved optical brain imager for monitoring cerebral oxygenation during carotid surgery

    Science.gov (United States)

    Kacprzak, Michal; Liebert, Adam; Staszkiewicz, Walerian; Gabrusiewicz, Andrzej; Sawosz, Piotr; Madycki, Grzegorz; Maniewski, Roman

    2012-01-01

    Recent studies have shown that time-resolved optical measurements of the head can estimate changes in the absorption coefficient with depth discrimination. Thus, changes in tissue oxygenation, which are specific to intracranial tissues, can be assessed using this advanced technique, and this method allows us to avoid the influence of changes to extracerebral tissue oxygenation on the measured signals. We report the results of time-resolved optical imaging that was carried out during carotid endarterectomy. This surgery remains the ``gold standard'' treatment for carotid stenosis, and intraoperative brain oxygenation monitoring may improve the safety of this procedure. A time-resolved optical imager was utilized within the operating theater. This instrument allows for the simultaneous acquisition of 32 distributions of the time-of-flight of photons at two wavelengths on both hemispheres. Analysis of the statistical moments of the measured distributions of the time-of-flight of photons was applied for estimating changes in the absorption coefficient as a function of depth. Time courses of changes in oxy- and deoxyhemoglobin of the extra- and intracerebral compartments during cross-clamping of the carotid arteries were obtained. A decrease in the oxyhemoglobin concentration and an increase in the deoxyhemoglobin concentrations were observed in a large area of the head. Large changes were observed in the hemisphere ipsilateral to the site of clamped carotid arteries. Smaller amplitude changes were noted at the contralateral site. We also found that changes in the hemoglobin signals, as estimated from intracerebral tissue, are very sensitive to clamping of the internal carotid artery, whereas its sensitivity to clamping of the external carotid artery is limited. We concluded that intraoperative multichannel measurements allow for imaging of brain tissue hemodynamics. However, when monitoring the brain during carotid surgery, a single-channel measurement may be

  13. The primary photophysics of the Avena sativa phototropin 1 LOV2 domain observed with time-resolved emission spectroscopy†

    Science.gov (United States)

    van Stokkum, Ivo H.M.; Gauden, Magdalena; Crosson, Sean; van Grondelle, Rienk; Moffat, Keith; Kennis, John T.M.

    2016-01-01

    The phototropins are blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine in light, oxygen or voltage (LOV) domains. The primary reactions of the Avena sativa phototropin 1 LOV2 domain were investigated by means of time-resolved and low-temperature fluorescence spectroscopy. Synchroscan streak camera experiments revealed a fluorescence lifetime of 2.2 ns in LOV2. A weak long-lived component with emission intensity from 600 to 650 nm was assigned to phosphorescence from the reactive FMN triplet state. This observation allowed determination of the LOV2 triplet state energy level at physiological temperature at 16600 cm−1. FMN dissolved in aqueous solution showed pH-dependent fluorescence lifetimes of 2.7 ns at pH 2 and 3.9–4.1 ns at pH 3 to 8. Here, too, a weak phosphorescence band was observed. The fluorescence quantum yield of LOV2 increased from 0.13 to 0.41 upon cooling the sample from 293 to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K in the steady-state emission. PMID:21261629

  14. Time-resolved temperature measurements in a rapid compression machine using quantum cascade laser absorption in the intrapulse mode

    KAUST Repository

    Nasir, Ehson Fawad

    2016-07-16

    A temperature sensor based on the intrapulse absorption spectroscopy technique has been developed to measure in situ temperature time-histories in a rapid compression machine (RCM). Two quantum-cascade lasers (QCLs) emitting near 4.55μm and 4.89μm were operated in pulsed mode, causing a frequency "down-chirp" across two ro-vibrational transitions of carbon monoxide. The down-chirp phenomenon resulted in large spectral tuning (δν ∼2.8cm-1) within a single pulse of each laser at a high pulse repetition frequency (100kHz). The wide tuning range allowed the application of the two-line thermometry technique, thus making the sensor quantitative and calibration-free. The sensor was first tested in non-reactive CO-N2 gas mixtures in the RCM and then applied to cases of n-pentane oxidation. Experiments were carried out for end of compression (EOC) pressures and temperatures ranging 9.21-15.32bar and 745-827K, respectively. Measured EOC temperatures agreed with isentropic calculations within 5%. Temperature rise measured during the first-stage ignition of n-pentane is over-predicted by zero-dimensional kinetic simulations. This work presents, for the first time, highly time-resolved temperature measurements in reactive and non-reactive rapid compression machine experiments. © 2016 Elsevier Ltd.

  15. Time-resolved x-ray diffraction and Raman studies of the phase transition mechanisms of methane hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, Hisako, E-mail: hirai@sci.ehime-u.ac.jp; Kadobayashi, Hirokazu [Geodynamics Research Center, Ehime University, Matsuyama, Ehime 790-8577 (Japan); Hirao, Naohisa; Ohishi, Yasuo [Japan Association of Synchrotron Radiation Institution, Harima 679-5198 (Japan); Ohtake, Michika; Yamamoto, Yoshitaka [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8569 (Japan); Nakano, Satoshi [National Institute for Material Science, Tsukuba, Ibaraki 305-0044 (Japan)

    2015-01-14

    The mechanisms by which methane hydrate transforms from an sI to sH structure and from an sH to filled-ice Ih structure were examined using time-resolved X-ray diffractometry (XRD) and Raman spectroscopy in conjunction with charge-coupled device camera observation under fixed pressure conditions. The XRD data obtained for the sI–sH transition at 0.8 GPa revealed an inverse correlation between sI and sH, suggesting that the sI structure is replaced by sH. Meanwhile, the Raman analysis demonstrated that although the 12-hedra of sI are retained, the 14-hedra are replaced sequentially by additional 12-hedra, modified 12-hedra, and 20-hedra cages of sH. With the sH to filled-ice Ih transition at 1.8 GPa, both the XRD and Raman data showed that this occurs through a sudden collapse of the sH structure and subsequent release of solid and fluid methane that is gradually incorporated into the filled-ice Ih to complete its structure. This therefore represents a typical reconstructive transition mechanism.

  16. Time-resolved photoluminescence study of CdSe/CdMnS/CdS core/multi-shell nanoplatelets

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, J. R. [Department of Electrical Engineering, State University of New York, University at Buffalo, Buffalo, New York 14260 (United States); Department of Physics, State University of New York, University at Buffalo, Buffalo, New York 14260 (United States); Delikanli, S.; Demir, H. V., E-mail: volkan@bilkent.edu.tr [LUMINOUS Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Materials Sciences, Nanyang Technological University, Singapore 639798 (Singapore); Department of Electrical and Electronics Engineering, Department of Physics, UNAM−Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Scrace, T.; Zhang, P.; Norden, T.; Petrou, A., E-mail: petrou@buffalo.edu [Department of Physics, State University of New York, University at Buffalo, Buffalo, New York 14260 (United States); Thomay, T.; Cartwright, A. N. [Department of Electrical Engineering, State University of New York, University at Buffalo, Buffalo, New York 14260 (United States)

    2016-06-13

    We used photoluminescence spectroscopy to resolve two emission features in CdSe/CdMnS/CdS and CdSe/CdS core/multi-shell nanoplatelet heterostructures. The photoluminescence from the magnetic sample has a positive circular polarization with a maximum centered at the position of the lower energy feature. The higher energy feature has a corresponding signature in the absorption spectrum; this is not the case for the low-energy feature. We have also studied the temporal evolution of these features using a pulsed-excitation/time-resolved photoluminescence technique to investigate their corresponding recombination channels. A model was used to analyze the temporal dynamics of the photoluminescence which yielded two distinct timescales associated with these recombination channels. The above results indicate that the low-energy feature is associated with recombination of electrons with holes localized at the core/shell interfaces; the high-energy feature, on the other hand, is excitonic in nature with the holes confined within the CdSe cores.

  17. Characterization of induced nanoplasmonic fields in time-resolved photoemission: A classical trajectory approach applied to gold nanospheres

    Science.gov (United States)

    Saydanzad, Erfan; Li, Jianxiong; Thumm, Uwe

    2017-05-01

    Attosecond time-resolved spectroscopy has been shown to be a powerful method for examining the electronic dynamics in atoms, and this technique is now being transferred to the investigation of elastic and inelastic scattering during electron transport and collective electronic (plasmonic) effects in solids. By sampling over classical photoelectron trajectories, we simulated streaked photoelectron energy spectra as a function of the time delay between ionizing isolated attosecond extreme ultraviolet (XUV) pulses and assisting infrared or visible streaking laser pulses. Our calculations comprise a sequence of four steps: XUV excitation, electron transport in matter, escape from the surface, and propagation to the photoelectron detector. Based on numerical applications to gold nanospheres of 5- and 50-nm radius, we investigate streaked photoemission spectra with regard to (i) the nanoparticle's dielectric response to the electric field of the streaking laser pulse, (ii) relative contributions to photoelectron release from different locations on the surface and inside the nanoparticle, (iii) contributions of photoemission from the Fermi level only versus emission from the entire occupied conduction band, and (iv) their fidelity in imaging the spatiotemporal distribution of the induced plasmonic field near the particle's surface.

  18. Assessing the feasibility of time-resolved fNIRS to detect brain activity during motor imagery

    Science.gov (United States)

    Abdalmalak, Androu; Milej, Daniel; Diop, Mamadou; Naci, Lorina; Owen, Adrian M.; St. Lawrence, Keith

    2016-03-01

    Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical technique for detecting brain activity, which has been previously used during motor and motor executive tasks. There is an increasing interest in using fNIRS as a brain computer interface (BCI) for patients who lack the physical, but not the mental, ability to respond to commands. The goal of this study is to assess the feasibility of time-resolved fNIRS to detect brain activity during motor imagery. Stability tests were conducted to ensure the temporal stability of the signal, and motor imagery data were acquired on healthy subjects. The NIRS probes were placed on the scalp over the premotor cortex (PMC) and supplementary motor area (SMA), as these areas are responsible for motion planning. To confirm the fNIRS results, subjects underwent functional magnetic resonance imaging (fMRI) while performing the same task. Seven subjects have participated to date, and significant activation in the SMA and/or the PMC during motor imagery was detected by both fMRI and fNIRS in 4 of the 7 subjects. No activation was detected by either technique in the remaining three participants, which was not unexpected due to the nature of the task. The agreement between the two imaging modalities highlights the potential of fNIRS as a BCI, which could be adapted for bedside studies of patients with disorders of consciousness.

  19. Direct observation of photocarrier electron dynamics in C60 films on graphite by time-resolved two-photon photoemission

    Science.gov (United States)

    Shibuta, Masahiro; Yamamoto, Kazuo; Ohta, Tsutomu; Nakaya, Masato; Eguchi, Toyoaki; Nakajima, Atsushi

    2016-01-01

    Time-resolved two-photon photoemission (TR-2PPE) spectroscopy is employed to probe the electronic states of a C60 fullerene film formed on highly oriented pyrolytic graphite (HOPG), acting as a model two-dimensional (2D) material for multi-layered graphene. Owing to the in-plane sp2-hybridized nature of the HOPG, the TR-2PPE spectra reveal the energetics and dynamics of photocarriers in the C60 film: after hot excitons are nascently formed in C60 via intramolecular excitation by a pump photon, they dissociate into photocarriers of free electrons and the corresponding holes, and the electrons are subsequently detected by a probe photon as photoelectrons. The decay rate of photocarriers from the C60 film into the HOPG is evaluated to be 1.31 × 1012 s−1, suggesting a weak van der Waals interaction at the interface, where the photocarriers tentatively occupy the lowest unoccupied molecular orbital (LUMO) of C60. The photocarrier electron dynamics following the hot exciton dissociation in the organic thin films has not been realized for any metallic substrates exhibiting strong interactions with the overlayer. Furthermore, the thickness dependence of the electron lifetime in the LUMO reveals that the electron hopping rate in C60 layers is 3.3 ± 1.2 × 1013 s−1. PMID:27775005

  20. Lattice dynamics in two-photon-excited CdS studied by picosecond time-resolved X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Kishimura, Hiroaki; Hironaka, Yoichiro [Materials and Structures Laboratory, Tokyo Institute of Technology, R3-10, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Nakamura, Kazutaka G. [Materials and Structures Laboratory, Tokyo Institute of Technology, R3-10, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan)], E-mail: nakamura.k.ai@m.titech.ac.jp

    2008-08-01

    Lattice dynamics and radiative processes in single-crystal cadmium sulfide induced by two-photon excitation with a femtosecond laser are investigated. The development of lattice expansion is directly observed by picosecond time-resolved X-ray diffraction. The obtained lattice dynamics are explained on the basis of a thermally induced impulsive-strain model. The model calculation indicates that two- and more-photon absorption processes occur and that reflectivity rapidly increases under laser irradiation. In photoluminescence spectroscopy, the spectra for TW cm{sup -2} excitation are shifted to lower energy and show an additional shoulder at 2.35 eV. Furthermore, emission due to Fabry-Perot laser modes with self-formed cavities was observed under 11 TW cm{sup -2} excitation. The discrepancy between carrier densities deduced from the lattice expansion and the PL spectra indicates that the predominant process at a higher carrier density is not radiative recombination, but Auger recombination followed by lattice heating.

  1. Time-Resolved Measurements of Suprathermal Ion Transport Induced by Intermittent Plasma Blob Filaments.

    Science.gov (United States)

    Bovet, A; Fasoli, A; Furno, I

    2014-11-28

    Suprathermal ion turbulent transport in magnetized plasmas is generally nondiffusive, ranging from subdiffusive to superdiffusive depending on the interplay of the turbulent structures and the suprathermal ion orbits. Here, we present time-resolved measurements of the cross-field suprathermal ion transport in a toroidal magnetized turbulent plasma. Measurements in the superdiffusive regime are characterized by a higher intermittency than in the subdiffusive regime. Using conditional averaging, we show that, when the transport is superdiffusive, suprathermal ions are transported by intermittent field-elongated turbulent structures that are radially propagating.

  2. Time-resolved photoluminescence of cubic Mg doped GaN

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, R.; Gaspar, C.; Monteiro, T.; Pereira, E.; Schoettker, B.; Frey, T.; As, D.J.; Schikora, D.; Lischka, K.

    1999-07-01

    Mg doped cubic GaN layers were studied by steady state and time resolved photoluminescence. The blue emission due to Mg doping can be decomposed in three bands. The decay curves and the spectral shift with time delays indicates donor-acceptor pair behavior. This can be confirmed by excitation density dependent measurements. Furthermore temperature dependent analysis shows that the three emissions have one impurity in common. The authors propose that this is an acceptor level related to the Mg incorporation and the three deep donor levels are due to compensation effects.

  3. A high sensitivity time-resolved microfluorimeter for real-time cell biology

    Science.gov (United States)

    Martin-Fernandez, M. L.; Tobin, M. J.; Clarke, D. T.; Gregory, C. M.; Jones, G. R.

    1996-10-01

    We describe an instrument based on the novel combination of synchrotron radiation, a high sensitivity time-resolved microfluorimeter, and a multiframe single photon counting data acquisition system. This instrument has been designed specifically to measure kinetic events in live cells using fluorescence resonance energy transfer, and is capable of rapidly collecting multiple consecutive decay profiles from a small number of fluorophores. The low irradiance on the samples (measurements over periods of hours. A very low limit of detection (measurements of fluorescence resonance energy transfer are used to monitor the degree of clustering of epidermal growth factor receptors during endocytosis, over a period of about 1 h, with a 5 s resolution.

  4. Coalescence dynamics of size-selected gold clusters studied by time-resolved transmission electron microscopy

    Science.gov (United States)

    Liu, J.; Foster, D.; Li, Z. Y.; Wilkinson, N.; Yuan, J.

    2017-09-01

    Coalescence dynamics of size-selected gold (Au) clusters (each with nominal 923 atoms), on amorphous Si3N4 substrate at room temperature, has been studied via time-resolved transmission electron microscopy (TEM). We found that the clusters approached each other in two stages. In the first stage, the drift velocity was independent of the particle separation and could be attributed to beam-induced random motion. In the second stage, the clusters were found to jump into contact with a much higher final averaged speed. This is independent of beam dose rates and is attributed to the van der Waal attraction.

  5. CMOS Time-Resolved, Contact, and Multispectral Fluorescence Imaging for DNA Molecular Diagnostics

    Directory of Open Access Journals (Sweden)

    Nan Guo

    2014-10-01

    Full Text Available Instrumental limitations such as bulkiness and high cost prevent the fluorescence technique from becoming ubiquitous for point-of-care deoxyribonucleic acid (DNA detection and other in-field molecular diagnostics applications. The complimentary metal-oxide-semiconductor (CMOS technology, as benefited from process scaling, provides several advanced capabilities such as high integration density, high-resolution signal processing, and low power consumption, enabling sensitive, integrated, and low-cost fluorescence analytical platforms. In this paper, CMOS time-resolved, contact, and multispectral imaging are reviewed. Recently reported CMOS fluorescence analysis microsystem prototypes are surveyed to highlight the present state of the art.

  6. Time-Resolved Imaging and Manipulation of H2 Fragmentation in Intense Laser Fields

    Science.gov (United States)

    Ergler, Th.; Rudenko, A.; Feuerstein, B.; Zrost, K.; Schröter, C. D.; Moshammer, R.; Ullrich, J.

    2005-08-01

    We report on the experimental realization of time-resolved coincident Coulomb explosion imaging of H2 fragmentation in 1014 W/cm2 laser fields. Combining a high-resolution “reaction microscope” and a fs pump-probe setup, we map the motion of wave packets dissociating via one- or two-photon channels, respectively, and observe a new region of enhanced ionization. The long-term interferometric stability of our system allows us to extend pump-probe experiments into the region of overlapping pulses, which offers new possibilities for the manipulation of ultrafast molecular fragmentation dynamics.

  7. Measurements of Turbulent Convection Speeds in Multistream Jets Using Time-Resolved PIV

    Science.gov (United States)

    Bridges, James; Wernet, Mark P.

    2017-01-01

    Convection speeds of turbulent velocities in jets, including multi-stream jets with and without flight stream, were measured using an innovative application of time-resolved particle image velocimetry. The paper describes the unique instrumentation and data analysis that allows the measurement to be made. Extensive data is shown that relates convection speed, mean velocity, and turbulent velocities for multiple jet cases. These data support the overall observation that the local turbulent convection speed is roughly that of the local mean velocity, biased by the relative intensity of turbulence.

  8. Measurements of Turbulence Convection Speeds in Multistream Jets Using Time-Resolved PIV

    Science.gov (United States)

    Bridges, James; Wernet, Mark P.

    2017-01-01

    Convection speeds of turbulent velocities in jets, including multi-stream jets with and without flight stream, were measured using an innovative application of time-resolved particle image velocimetry. The paper describes the unique instrumentation and data analysis that allows the measurement to be made. Extensive data is shown that relates convection speed, mean velocity, and turbulent velocities for multiple jet cases. These data support the overall observation that the local turbulent convection speed is roughly that of the local mean velocity, biased by the relative intensity of turbulence.

  9. Sudden polarization in the twisted, phantom state of tetraphenylethylene detected by time-resolved microwave conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Schuddeboom, W.; Jonker, S.A.; Warman, J.M.; Haas, M.P. de; Vermeulen, M.J.W. (Delft Univ. of Technology (Netherlands)); Jager, W.F.; Lange, B. de; Feringa, B.L. (Univ. of Groningen (Netherlands)); Fessenden, R.W. (Univ. of Notre Dame, IN (United States))

    1993-04-21

    Photoexcitation of the symmetrical molecules tetraphenylethylene and tetra-p-methoxyphenylethylene dissolved in saturated hydrocarbon solvents results in a transient increase in the dielectric loss of the solutions as monitored using the nanosecond time-resolved microwave conductivity (TRMC) technique. This provides direct evidence for the dipolar, or [open quotes]zwitterionic,[close quotes] nature of the [sup 1]p* phantom state formed from S[sub 1] by rotation around the central carbon-carbon bond. Dipole relaxation occurs mainly by charge inversion between the two energetically equivalent zwitterionic configurations. Z[sub [+-

  10. Time-resolved ultraviolet photoluminescence of ZnO/ZnGa2O4 composite layer

    Science.gov (United States)

    Yang, Qing; Zhou, Xiaohong; Nukui, Takao; Saeki, Yu; Izumi, Sotaro; Tackeuchi, Atsushi; Tatsuoka, Hirokazu; Liang, Shuhua

    2014-02-01

    The ultraviolet photoluminescence of ZnO/ZnGa2O4 composite layer grown by the thermal oxidation of ZnS with gallium was investigated by the time-resolved photoluminescence as a function of measuring temperature and excitation power. With increase of excitation power, the D0X emission is easily saturated than the DAP emission from ZnO/ZnGa2O4 composite layer, and which is dramatically enhanced as compared with that from pure ZnO layer grown without gallium. The radiative recombination process with ultra-long lifetime controlled the carrier recombination of ZnO/ZnGa2O4 composite layer.

  11. Ionic contrast terahertz time resolved imaging of frog auricular heart muscle electrical activity

    Science.gov (United States)

    Masson, Jean-Baptiste; Sauviat, Martin-Pierre; Gallot, Guilhem

    2006-10-01

    The authors demonstrate the direct, noninvasive and time resolved imaging of functional frog auricular fibers by ionic contrast terahertz (ICT) near field microscopy. This technique provides quantitative, time-dependent measurement of ionic flow during auricular muscle electrical activity, and opens the way of direct noninvasive imaging of cardiac activity under stimulation. ICT microscopy technique was associated with full three-dimensional simulation enabling to measure precisely the fiber sizes. This technique coupled to waveguide technology should provide the grounds to development of advanced in vivo ion flux measurement in mammalian hearts, allowing the prediction of heart attack from change in K+ fluxes.

  12. Calibration of a time-resolved hard-x-ray detector using radioactive sources

    Energy Technology Data Exchange (ETDEWEB)

    Stoeckl, C., E-mail: csto@lle.rochester.edu; Theobald, W.; Regan, S. P.; Romanofsky, M. H. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299 (United States)

    2016-11-15

    A four-channel, time-resolved, hard x-ray detector (HXRD) has been operating at the Laboratory for Laser Energetics for more than a decade. The slope temperature of the hot-electron population in direct-drive inertial confinement fusion experiments is inferred by recording the hard x-ray radiation generated in the interaction of the electrons with the target. Measuring the energy deposited by hot electrons requires an absolute calibration of the hard x-ray detector. A novel method to obtain an absolute calibration of the HXRD using single photons from radioactive sources was developed, which uses a thermoelectrically cooled, low-noise, charge-sensitive amplifier.

  13. Two-dimensional time resolved measurements of the electron temperature in MST

    Energy Technology Data Exchange (ETDEWEB)

    Franz, P. [Consorzio RFX, Euratom-ENEA Assocation, Padova (Italy); Bonomo, F. [Consorzio RFX, Euratom-ENEA Assocation, Padova (Italy); Univ. di Padova, Padova, (Italy). Dipart. di Fisica; Marrelli, L. [Consorzio RFX, Euratom-ENEA Assocation, Padova (Italy); Martin, P. [Consorzio RFX, Euratom-ENEA Assocation, Padova (Italy); Univ. di Padova, Padova, (Italy). Dipart. di Fisica; Piovesan, P. [Consorzio RFX, Euratom-ENEA Assocation, Padova (Italy); Spizzo, G. [Consorzio RFX, Euratom-ENEA Assocation, Padova (Italy); Chapman, B. E. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics; Craig, D. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas; Den Hartog, D. J. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas; Goetz, J. A. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics; O’Connell, R. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics; Prager, S. C. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas; Reyfman, M. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics; Sarff, J. S. [Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Physics and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas

    2006-01-01

    Two-dimensional (2D) time resolved images of the electron temperature profile in the core of the MST reversed field pinchplasma are presented. The measurements have been obtained with a soft x-ray (SXR) tomographic diagnostic comprised of four cameras, each with a multichannel photodiode array, viewing the plasma from different poloidal angles, with a total of 74 channels. The 2D electron temperature profile is estimated by simultaneously measuring the SXR emissivity through different beryllium foils using the standard double-filter technique. With these methods, fast temperature variation in the core of the plasma (up to 100 kHz) can be analyzed.

  14. Time resolved bovine host reponse to virulence factors mapped in milk by selected reaction monitoring

    DEFF Research Database (Denmark)

    Bislev, Stine Lønnerup; Kusebauch, Ulrike; Codrea, Marius Cosmin

    to gram-positive and gram-negative cell wall components. The results demonstrated that the extent of protein regulation is much larger after challenge with LPS than with PGN underpinning the growing evidence that gram-negative bacteria cause a far more acute host response than gram-positive bacteria...... in milk samples from cows challenged with peptidoglycan (PGN) from the gram-positive bacteria Staphylococcus aureus and lipopolysaccharide (LPS) from the gram-negative bacteria Escherichia coli for 54 hours. This method allowed for the first time a thorough proteome analysis of the time-resolved response...

  15. A sensitive time-resolved radiation pyrometer for shock-temperature measurements above 1500 K

    Science.gov (United States)

    Boslough, Mark B.; Ahrens, Thomas J.

    1989-01-01

    The general design, calibration, and performance of a new high-sensitivity radiation pyrometer are described. The pyrometer can determine time-resolved temperatures (as low as 1500 K) in shocked materials by measuring the spectral radiance of light emitted from shocked solid samples in the visible and near-infrared wavelength range (0.5-1.0 micron). The high sensitivity of the radiation pyrometer is attributed to the large angular aperture (0.06 sr), the large bandwidth per channel (up to 0.1 micron), the large photodiode detection areas (1.0 sq cm), and the small number of calibrated channels (4) among which light is divided.

  16. Optical and x-ray time resolved study of the structural transition in mixed valence manganites

    Directory of Open Access Journals (Sweden)

    Jia Q. X.

    2013-03-01

    Full Text Available Time resolved optical reflectivity and x-ray diffraction techniques are employed to study the laser-induced structural response in two charge and orbitally ordered manganites. Optical data indicate a non-thermal nature of the laser-triggered phase transition via the disappearance of an optical phonon related to the charge and orbitally ordered phase. The x-ray diffraction measurements on superlattice reflections confirm the non-thermal time scale of the initial step of this phase transition but also show that the complete change of structural symmetry is not instantaneous.

  17. Application of time-resolved digital holographic microscopy to study femtosecond damage process in thin films

    Science.gov (United States)

    Å iaulys, Nerijus; Gallais, Laurent; Melninkaitis, Andrius

    2013-11-01

    An imaging of strongly excited thin film dielectric coating is done by the means of femtosecond time-resolved off-axis digital holography (TRDH). Ta2O5 single layer coating have been investigated at different time moments in transmission mode. The evolving damage process was recorded in series of microscopic amplitude and phase contrast images. Different processes were found to occur and namely: Kerr effect, free-electron generation, ultrafast lattice heating and shock wave generation. The trends in electronic contribution are qualitatively reproduced by the theoretical model while the other effects require additional studies.

  18. Performance of the Time Resolved Spectrometer for the 5 MeV Photo-Injector PHIN

    CERN Document Server

    Olvegaard, M; Mete, O; Csatari, M; Dabrowski, A; Dobert, S; Lefevre, T; Petrarca, M

    2011-01-01

    The PHIN photo-injector test facility is being commissioned at CERN to demonstrate the capability to produce the required beam for the 3rd CLIC Test Facility (CTF3), which includes the production of a 3.5A stable beam, bunched at 1.5 GHz with a relative energy spread of less than 1%. A 90◦ spectrometer is instrumented with an OTR screen coupled to a gated intensified camera, followed by a segmented beam dump for time resolved energy measurements. The following paper describes the transverse and temporal resolution of the instrumentation with an outlook towards single-bunch energy measurements.

  19. Watching proteins function with time-resolved x-ray crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Šrajer, Vukica; Schmidt, Marius

    2017-08-22

    Macromolecular crystallography was immensely successful in the last two decades. To a large degree this success resulted from use of powerful third generation synchrotron x-ray sources. An expansive database of more than 100 000 protein structures, of which many were determined at resolution better than 2 Å, is available today. With this achievement, the spotlight in structural biology is shifting from determination of static structures to elucidating dynamic aspects of protein function. A powerful tool for addressing these aspects is time-resolved crystallography, where a genuine biological function is triggered in the crystal with a goal of capturing molecules in action and determining protein kinetics and structures of intermediates (Schmidt et al 2005a Methods Mol. Biol. 305 115–54, Schmidt 2008 Ultrashort Laser Pulses in Biology and Medicine (Berlin: Springer) pp 201–41, Neutze and Moffat 2012 Curr. Opin. Struct. Biol. 22 651–9, Šrajer 2014 The Future of Dynamic Structural Science (Berlin: Springer) pp 237–51). In this approach, short and intense x-ray pulses are used to probe intermediates in real time and at room temperature, in an ongoing reaction that is initiated synchronously and rapidly in the crystal. Time-resolved macromolecular crystallography with 100 ps time resolution at synchrotron x-ray sources is in its mature phase today, particularly for studies of reversible, light-initiated reactions. The advent of the new free electron lasers for hard x-rays (XFELs; 5–20 keV), which provide exceptionally intense, femtosecond x-ray pulses, marks a new frontier for time-resolved crystallography. The exploration of ultra-fast events becomes possible in high-resolution structural detail, on sub-picosecond time scales (Tenboer et al 2014 Science 346 1242–6, Barends et al 2015 Science 350 445–50, Pande et al 2016 Science 352 725–9). We review here state-of-the-art time-resolved crystallographic experiments both at synchrotrons and XFELs. We

  20. The 7BM beamline at the APS: a facility for time-resolved fluid dynamics measurements

    Science.gov (United States)

    Kastengren, Alan; Powell, Christopher F.; Arms, Dohn; Dufresne, Eric M.; Gibson, Harold; Wang, Jin

    2012-01-01

    In recent years, X-ray radiography has been used to probe the internal structure of dense sprays with microsecond time resolution and a spatial resolution of 15 µm even in high-pressure environments. Recently, the 7BM beamline at the Advanced Photon Source (APS) has been commissioned to focus on the needs of X-ray spray radiography measurements. The spatial resolution and X-ray intensity at this beamline represent a significant improvement over previous time-resolved X-ray radiography measurements at the APS. PMID:22713903

  1. Modelling the thermal quenching mechanism in quartz based on time-resolved optically stimulated luminescence

    DEFF Research Database (Denmark)

    Pagonis, V.; Ankjærgaard, Christina; Murray, Andrew

    2010-01-01

    This paper presents a new numerical model for thermal quenching in quartz, based on the previously suggested Mott–Seitz mechanism. In the model electrons from a dosimetric trap are raised by optical or thermal stimulation into the conduction band, followed by an electronic transition from...... simulations are carried out of time-resolved optically stimulated luminescence (TR-OSL) experiments, in which the temperature dependence of luminescence lifetimes in quartz is studied as a function of the stimulation temperature. Good quantitative agreement is found between the simulation results and new...... experimental data obtained using a single-aliquot procedure on a sedimentary quartz sample....

  2. Time resolved temperature measurement of polymer surface irradiated by mid-IR free electron laser

    Science.gov (United States)

    Araki, Mitsunori; Chiba, Tomoyuki; Oyama, Takahiro; Imai, Takayuki; Tsukiyama, Koichi

    2017-08-01

    We have developed the time-resolved temperature measurement system by using a radiation thermometer FLIR SC620. Temporal temperature profiles of an acrylic resin surface by the irradiation of infrared free electron laser (FEL) pulse were recorded in an 8 ms resolution to measure an instantaneous temperature rise and decay profile. Under the single-shot condition, a peak temperature defined as the temperature jump from the ambient temperature was found to be proportional to the absorbance. Under the multi-shot condition, the temperature accumulation was found to reach a roughly constant value where the supply and release of the heat is balanced.

  3. Time-resolved SAXS measurements facilitated by online HPLC buffer exchange

    DEFF Research Database (Denmark)

    Jensen, Malene Hillerup; Toft, Katrine Nørgaard; David, Gabriel

    2010-01-01

    be possible to separate contributions from individual species present in solution. Hence, time-resolved SAXS (TR-SAXS) data of processes in development can be analyzed. Many reported TR-SAXS results are initialized by a sudden change in buffer conditions facilitated by rapid mixing combined with either...... continuous or stopped flow. In this paper a method for obtaining TR-SAXS data from systems where the reaction is triggered by removal of a species is presented. This method is based on fast buffer exchange over a short desalting column facilitated by an online HPLC (high-performance liquid chromatography...

  4. An efficient and accurate approach to MTE-MART for time-resolved tomographic PIV

    Science.gov (United States)

    Lynch, K. P.; Scarano, F.

    2015-03-01

    The motion-tracking-enhanced MART (MTE-MART; Novara et al. in Meas Sci Technol 21:035401, 2010) has demonstrated the potential to increase the accuracy of tomographic PIV by the combined use of a short sequence of non-simultaneous recordings. A clear bottleneck of the MTE-MART technique has been its computational cost. For large datasets comprising time-resolved sequences, MTE-MART becomes unaffordable and has been barely applied even for the analysis of densely seeded tomographic PIV datasets. A novel implementation is proposed for tomographic PIV image sequences, which strongly reduces the computational burden of MTE-MART, possibly below that of regular MART. The method is a sequential algorithm that produces a time-marching estimation of the object intensity field based on an enhanced guess, which is built upon the object reconstructed at the previous time instant. As the method becomes effective after a number of snapshots (typically 5-10), the sequential MTE-MART (SMTE) is most suited for time-resolved sequences. The computational cost reduction due to SMTE simply stems from the fewer MART iterations required for each time instant. Moreover, the method yields superior reconstruction quality and higher velocity field measurement precision when compared with both MART and MTE-MART. The working principle is assessed in terms of computational effort, reconstruction quality and velocity field accuracy with both synthetic time-resolved tomographic images of a turbulent boundary layer and two experimental databases documented in the literature. The first is the time-resolved data of flow past an airfoil trailing edge used in the study of Novara and Scarano (Exp Fluids 52:1027-1041, 2012); the second is a swirling jet in a water flow. In both cases, the effective elimination of ghost particles is demonstrated in number and intensity within a short temporal transient of 5-10 frames, depending on the seeding density. The increased value of the velocity space

  5. Application of time-resolved fluorescence for direct and continuous probing of release from polymeric delivery vehicles.

    Science.gov (United States)

    Viger, Mathieu L; Sheng, Wangzhong; McFearin, Cathryn L; Berezin, Mikhail Y; Almutairi, Adah

    2013-11-10

    Though accurately evaluating the kinetics of release is critical for validating newly designed therapeutic carriers for in vivo applications, few methods yet exist for release measurement in real time and without the need for any sample preparation. Many of the current approaches (e.g. chromatographic methods, absorption spectroscopy, or NMR spectroscopy) rely on isolation of the released material from the loaded vehicles, which require additional sample purification and can lead to loss of accuracy when probing fast kinetics of release. In this study we describe the use of time-resolved fluorescence for in situ monitoring of small molecule release kinetics from biodegradable polymeric drug delivery systems. This method relies on the observation that fluorescent reporters being released from polymeric drug delivery systems possess distinct excited-state lifetime components, reflecting their different environments in the particle suspensions, i.e., confined in the polymer matrices or free in the aqueous environment. These distinct lifetimes enable real-time quantitative mapping of the relative concentrations of dye in each population to obtain precise and accurate temporal information on the release profile of particular carrier/payload combinations. We found that fluorescence lifetime better distinguishes subtle differences in release profiles (e.g. differences associated with dye loading) than conventional steady-state fluorescence measurements, which represent the averaged dye behavior over the entire scan. Given the method's applicability to both hydrophobic and hydrophilic cargo, it could be employed to model the release of any drug-carrier combination. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Development of functionalized terbium fluorescent nanoparticles for antibody labeling and time-resolved fluoroimmunoassay application.

    Science.gov (United States)

    Ye, Zhiqiang; Tan, Mingqian; Wang, Guilan; Yuan, Jingli

    2005-01-15

    Silica-based functionalized terbium fluorescent nanoparticles were prepared, characterized and developed as a fluorescence probe for antibody labeling and time-resolved fluoroimmunoassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion containing a strongly fluorescent Tb(3+) chelate, N,N,N(1),N(1)-[2,6-bis(3'-aminomethyl-1'-pyrazolyl)phenylpyridine] tetrakis(acetate)-Tb(3+) (BPTA-Tb(3+)), Triton X-100, octanol, and cyclohexane by controlling copolymerization of tetraethyl orthosilicate (TEOS) and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AEPS) with ammonia water. The characterizations by transmission electron microscopy and fluorometric methods show that the nanoparticles are spherical and uniform in size, 45 +/- 3nm in diameter, strongly fluorescent with fluorescence quantum yield of 10% and a long fluorescence lifetime of 2.0ms. The amino groups directly introduced to the nanoparticle's surface by using AEPS in the preparation made the surface modification and bioconjugation of the nanoparticles easier. The nanoparticle-labeled anti-human alpha-fetoprotein antibody was prepared and used for time-resolved fluoroimmunoassay of alpha-fetoprotein (AFP) in human serum samples. The assay response is linear from 0.10ngml(-1) to about 100ngml(-1) with the detection limit of 0.10ngml(-1). The coefficient variations (CVs) of the method are less than 9.0%, and the recoveries are in the range of 84-98% for human serum sample measurements.

  7. Real-time digital signal processing in multiphoton and time-resolved microscopy

    Science.gov (United States)

    Wilson, Jesse W.; Warren, Warren S.; Fischer, Martin C.

    2016-03-01

    The use of multiphoton interactions in biological tissue for imaging contrast requires highly sensitive optical measurements. These often involve signal processing and filtering steps between the photodetector and the data acquisition device, such as photon counting and lock-in amplification. These steps can be implemented as real-time digital signal processing (DSP) elements on field-programmable gate array (FPGA) devices, an approach that affords much greater flexibility than commercial photon counting or lock-in devices. We will present progress toward developing two new FPGA-based DSP devices for multiphoton and time-resolved microscopy applications. The first is a high-speed multiharmonic lock-in amplifier for transient absorption microscopy, which is being developed for real-time analysis of the intensity-dependence of melanin, with applications in vivo and ex vivo (noninvasive histopathology of melanoma and pigmented lesions). The second device is a kHz lock-in amplifier running on a low cost (50-200) development platform. It is our hope that these FPGA-based DSP devices will enable new, high-speed, low-cost applications in multiphoton and time-resolved microscopy.

  8. Key Intermediates in Ribosome Recycling Visualized by Time-Resolved Cryoelectron Microscopy.

    Science.gov (United States)

    Fu, Ziao; Kaledhonkar, Sandip; Borg, Anneli; Sun, Ming; Chen, Bo; Grassucci, Robert A; Ehrenberg, Måns; Frank, Joachim

    2016-12-06

    Upon encountering a stop codon on mRNA, polypeptide synthesis on the ribosome is terminated by release factors, and the ribosome complex, still bound with mRNA and P-site-bound tRNA (post-termination complex, PostTC), is split into ribosomal subunits, ready for a new round of translational initiation. Separation of post-termination ribosomes into subunits, or "ribosome recycling," is promoted by the joint action of ribosome-recycling factor (RRF) and elongation factor G (EF-G) in a guanosine triphosphate (GTP) hydrolysis-dependent manner. Here we used a mixing-spraying-based method of time-resolved cryo-electron microscopy (cryo-EM) to visualize the short-lived intermediates of the recycling process. The two complexes that contain (1) both RRF and EF-G bound to the PostTC or (2) deacylated tRNA bound to the 30S subunit are of particular interest. Our observations of the native form of these complexes demonstrate the strong potential of time-resolved cryo-EM for visualizing previously unobservable transient structures. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Characterization of female breast lesions from multi-wavelength time-resolved optical mammography

    Energy Technology Data Exchange (ETDEWEB)

    Spinelli, Lorenzo [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Torricelli, Alessandro [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Pifferi, Antonio [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Taroni, Paola [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Danesini, Gianmaria [Dipartimento di Radiologia, Casa di Cura S. Pio X, via Francesco Nava 31, I-20159 Milan (Italy); Cubeddu, Rinaldo [INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy)

    2005-06-07

    Characterization of both malignant and benign lesions in the female breast is presented as the result of a clinical study that involved more than 190 subjects in the framework of the OPTIMAMM European project. All the subjects underwent optical mammography, by means of a multi-wavelength time-resolved mammograph, in the range 637-985 nm. Optical images were processed by applying a perturbation model, relying on a nonlinear approximation of time-resolved transmittance curves in the presence of an inclusion, with the aim of estimating the major tissue constituents (i.e. oxy- and deoxy-haemoglobin, lipid and water) and structural parameters (linked to dimension and density of the scatterer centres) for both the lesion area and the surrounding tissue. The critical factors for the application of the perturbation model on in vivo data are also discussed. Forty-six malignant and 68 benign lesions were analysed. A subset of 32 cancers, 40 cysts and 14 fibroadenomas were found reliable for the perturbation analysis. For cancers, we show a higher blood content with respect to the surrounding tissue, while cysts are characterized by a lower concentration of scattering centres with respect to the surrounding tissue. For fibroadenomas, the low number of cases does not allow any definite conclusions.

  10. Molecular Tomography of the Quantum State by Time-Resolved Electron Diffraction

    Directory of Open Access Journals (Sweden)

    A. A. Ischenko

    2013-01-01

    Full Text Available A procedure is described that can be used to reconstruct the quantum state of a molecular ensemble from time-dependent internuclear probability density functions determined by time-resolved electron diffraction. The procedure makes use of established techniques for evaluating the density matrix and the phase-space joint probability density, that is, the Wigner function. A novel expression for describing electron diffraction intensities in terms of the Wigner function is presented. An approximate variant of the method, neglecting the off-diagonal elements of the density matrix, was tested by analyzing gas electron diffraction data for N2 in a Boltzmann distribution and TRED data obtained from the 193 nm photodissociation of CS2 to carbon monosulfide, CS, at 20, 40, and 120 ns after irradiation. The coherent changes in the nuclear subsystem by time-resolved electron diffraction method determine the fundamental transition from the standard kinetics to the dynamics of the phase trajectory of the molecule and the tomography of molecular quantum state.

  11. Development of a High-Speed Digitizer to Time Resolve Nanosecond Fluorescence Pulses

    Directory of Open Access Journals (Sweden)

    E. Moreno-García

    2012-04-01

    Full Text Available The development of a high-speed digitizer system to measure time-domain voltage pulses in nanoseconds range is presented in this work. The digitizer design includes a high performance digital signal processor, a high-bandwidth analog-to-digital converter of flash-type, a set of delay lines, and a computer to achieve the time-domain measurements. A program running on the processor applies a time-equivalent sampling technique to acquire the input pulse. The processor communicates with the computer via a serial port RS-232 to receive commands and to transmit data. A control program written in LabVIEW 7.1 starts an acquisition routine in the processor. The program reads data from processor point by point in each occurrence of the signal, and plots each point to recover the time-resolved input pulse after n occurrences. The developed prototype is applied to measure fluorescence pulses from a homemade spectrometer. For this application, the LabVIEW program was improved to control the spectrometer, and to register and plot time-resolved fluorescence pulses produced by a substance. The developed digitizer has 750 MHz of analog input bandwidth, and it is able to resolve 2 ns rise-time pulses with 150 ps of resolution and a temporal error of 2.6 percent.

  12. Determination of ammonia-oxidizing bacteria based on time-resolved fluorescence and tandem probe.

    Science.gov (United States)

    Lv, Xiaoxiao; Li, Zhizhang; Niu, Chenggang; Ruan, Min; Hang, Dawei; Zeng, Guangming

    2012-01-01

    To study the ecology of ammonia-oxidizing bacteria (AOB), quantitative techniques are essential. In this report, the authors introduced an innovative method based on time-resolved fluorescence to quantify AOB as a representative of the major functional microorganisms in sewage water treatment. A bifunctional europium complex with the characteristics of long lifetime and intense luminescence was used as labels in the experiments. In the detection, the capture probe and dye-labeled reporter probe could form a two-probe tandem with the target sequence, and the determination of target DNA was done by monitoring the time-resolved fluorescence signals of europium complex-labeled reporter probe left on the glass slide surface. The experiment conditions consisting of concentration of capture probe, hybridization temperature, hybridization time and washing time were optimized. This method presents satisfactory specificity to common bacteria such as Nitrobacter winogradskyi, Escherichia coli and Paenibacillus polymyxa. The detection limit was 3.65 × 10(-11)mol L(-1). This detection system enables us to rapidly and sensitively analyze the microbial population variety in sewage water treatment.

  13. Assessment of swirl spray interaction in lab scale combustor using time-resolved measurements

    Science.gov (United States)

    Rajamanickam, Kuppuraj; Jain, Manish; Basu, Saptarshi

    2017-11-01

    Liquid fuel injection in highly turbulent swirling flows becomes common practice in gas turbine combustors to improve the flame stabilization. It is well known that the vortex bubble breakdown (VBB) phenomenon in strong swirling jets exhibits complicated flow structures in the spatial domain. In this study, the interaction of hollow cone liquid sheet with such coaxial swirling flow field has been studied experimentally using time-resolved measurements. In particular, much attention is focused towards the near field breakup mechanism (i.e. primary atomization) of liquid sheet. The detailed swirling gas flow field characterization is carried out using time-resolved PIV ( 3.5 kHz). Furthermore, the complicated breakup mechanisms and interaction of the liquid sheet are imaged with the help of high-speed shadow imaging system. Subsequently, proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) is implemented over the instantaneous data sets to retrieve the modal information associated with the interaction dynamics. This helps to delineate more quantitative nature of interaction process between the liquid sheet and swirling gas phase flow field.

  14. Time-resolved structural studies of protein reaction dynamics: a smorgasbord of X-ray approaches.

    Science.gov (United States)

    Westenhoff, Sebastian; Nazarenko, Elena; Malmerberg, Erik; Davidsson, Jan; Katona, Gergely; Neutze, Richard

    2010-03-01

    Proteins undergo conformational changes during their biological function. As such, a high-resolution structure of a protein's resting conformation provides a starting point for elucidating its reaction mechanism, but provides no direct information concerning the protein's conformational dynamics. Several X-ray methods have been developed to elucidate those conformational changes that occur during a protein's reaction, including time-resolved Laue diffraction and intermediate trapping studies on three-dimensional protein crystals, and time-resolved wide-angle X-ray scattering and X-ray absorption studies on proteins in the solution phase. This review emphasizes the scope and limitations of these complementary experimental approaches when seeking to understand protein conformational dynamics. These methods are illustrated using a limited set of examples including myoglobin and haemoglobin in complex with carbon monoxide, the simple light-driven proton pump bacteriorhodopsin, and the superoxide scavenger superoxide reductase. In conclusion, likely future developments of these methods at synchrotron X-ray sources and the potential impact of emerging X-ray free-electron laser facilities are speculated upon.

  15. Feasibility analysis of an epidermal glucose sensor based on time-resolved fluorescence

    Science.gov (United States)

    Katika, Kamal M.; Pilon, Laurent

    2007-06-01

    The goal of this study is to test the feasibility of using an embedded time-resolved fluorescence sensor for monitoring glucose concentration. Skin is modeled as a multilayer medium with each layer having its own optical properties and fluorophore absorption coefficients, lifetimes, and quantum yields obtained from the literature. It is assumed that the two main fluorophores contributing to the fluorescence at these excitation and emission wavelengths are nicotinamide adenine dinucleotide (NAD)H and collagen. The intensity distributions of excitation and fluorescent light in skin are determined by solving the transient radiative transfer equation by using the modified method of characteristics. The fluorophore lifetimes are then recovered from the simulated fluorescence decays and compared with the actual lifetimes used in the simulations. Furthermore, the effect of adding Poissonian noise to the simulated decays on recovering the lifetimes was studied. For all cases, it was found that the fluorescence lifetime of NADH could not be recovered because of its negligible contribution to the overall fluorescence signal. The other lifetimes could be recovered to within 1.3% of input values. Finally, the glucose concentrations within the skin were recovered to within 13.5% of their actual values, indicating a possibility of measuring glucose concentrations by using a time-resolved fluorescence sensor.

  16. Denoising time-resolved microscopy image sequences with singular value thresholding

    Energy Technology Data Exchange (ETDEWEB)

    Furnival, Tom, E-mail: tjof2@cam.ac.uk; Leary, Rowan K., E-mail: rkl26@cam.ac.uk; Midgley, Paul A., E-mail: pam33@cam.ac.uk

    2017-07-15

    Time-resolved imaging in microscopy is important for the direct observation of a range of dynamic processes in both the physical and life sciences. However, the image sequences are often corrupted by noise, either as a result of high frame rates or a need to limit the radiation dose received by the sample. Here we exploit both spatial and temporal correlations using low-rank matrix recovery methods to denoise microscopy image sequences. We also make use of an unbiased risk estimator to address the issue of how much thresholding to apply in a robust and automated manner. The performance of the technique is demonstrated using simulated image sequences, as well as experimental scanning transmission electron microscopy data, where surface adatom motion and nanoparticle structural dynamics are recovered at rates of up to 32 frames per second. - Highlights: • Correlations in space and time are harnessed to denoise microscopy image sequences. • A robust estimator provides automated selection of the denoising parameter. • Motion tracking and automated noise estimation provides a versatile algorithm. • Application to time-resolved STEM enables study of atomic and nanoparticle dynamics.

  17. Compressive hyperspectral time-resolved wide-field fluorescence lifetime imaging

    Science.gov (United States)

    Pian, Qi; Yao, Ruoyang; Sinsuebphon, Nattawut; Intes, Xavier

    2017-07-01

    Spectrally resolved fluorescence lifetime imaging and spatial multiplexing have offered information content and collection-efficiency boosts in microscopy, but efficient implementations for macroscopic applications are still lacking. An imaging platform based on time-resolved structured light and hyperspectral single-pixel detection has been developed to perform quantitative macroscopic fluorescence lifetime imaging (MFLI) over a large field of view (FOV) and multiple spectral bands simultaneously. The system makes use of three digital micromirror device (DMD)-based spatial light modulators (SLMs) to generate spatial optical bases and reconstruct N by N images over 16 spectral channels with a time-resolved capability (∼40 ps temporal resolution) using fewer than N2 optical measurements. We demonstrate the potential of this new imaging platform by quantitatively imaging near-infrared (NIR) Förster resonance energy transfer (FRET) both in vitro and in vivo. The technique is well suited for quantitative hyperspectral lifetime imaging with a high sensitivity and paves the way for many important biomedical applications.

  18. A hyperspectral time resolved DOT system to monitor physiological changes of the human brain activity

    Science.gov (United States)

    Lange, F.; Peyrin, F.; Montcel, B.

    2015-07-01

    Diffuse optical tomography (DOT) is a growing area of research in the field of biomedical optics and neurosciences. Over the past 20 years, technical development allowed a more and more accurate detection of the brain activation, both spatially and in the calculation of the variations of chromophores's concentrations such as Hemoglobin, cytochrome c oxidase, etc. In particular, time resolved systems are able to distinguish between superficial layers (skin, skull) and deep layers (brain) allowing the differentiation between the systemic response and the response of the brain. In order to increase the accuracy of the brain's activation detection, we have developed a Hyperspectral Time Resolved DOT system. It is composed of a compact supercontinuum laser within the picosecond range for the source part and of an ICCD camera coupled with an imaging spectrometer for the detection part. This allows a simultaneous detection of the spatial and spectral dimension, as well as the time of flight of photons. Through the information acquired by our system, we've been able to retrieve, to our knowledge, the first spectrum of the physiology of the human brain activity as function as depth. Here we present the instrument and show our first in-vivo results that are demonstrating its capabilities to distinguish between the skin's response and the brain's responses during a cognitive task. We are also focused on the detection of the Fast Optical Signal.

  19. Time-Resolved In Situ Measurements During Rapid Alloy Solidification: Experimental Insight for Additive Manufacturing

    Science.gov (United States)

    McKeown, Joseph T.; Zweiacker, Kai; Liu, Can; Coughlin, Daniel R.; Clarke, Amy J.; Baldwin, J. Kevin; Gibbs, John W.; Roehling, John D.; Imhoff, Seth D.; Gibbs, Paul J.; Tourret, Damien; Wiezorek, Jörg M. K.; Campbell, Geoffrey H.

    2016-03-01

    Additive manufacturing (AM) of metals and alloys is becoming a pervasive technology in both research and industrial environments, though significant challenges remain before widespread implementation of AM can be realized. In situ investigations of rapid alloy solidification with high spatial and temporal resolutions can provide unique experimental insight into microstructure evolution and kinetics that are relevant for AM processing. Hypoeutectic thin-film Al-Cu and Al-Si alloys were investigated using dynamic transmission electron microscopy to monitor pulsed-laser-induced rapid solidification across microsecond timescales. Solid-liquid interface velocities measured from time-resolved images revealed accelerating solidification fronts in both alloys. The observed microstructure evolution, solidification product, and presence of a morphological instability at the solid-liquid interface in the Al-4 at.%Cu alloy are related to the measured interface velocities and small differences in composition that affect the thermophysical properties of the alloys. These time-resolved in situ measurements can inform and validate predictive modeling efforts for AM.

  20. Time-Resolved Fluorometry Based Sandwich Hybridisation Assay for HLA-DQA1 Typing

    Directory of Open Access Journals (Sweden)

    Minna Sjöroos

    1998-01-01

    Full Text Available A microtitration plate based time-resolved fluorescence (TRF hybridisation assay was developed for HLA typing utilising biotinylated sequence-specific catching probes and europium (Eu labelled gene locus-specific detection probe to allow time-resolved fluorometer reading of the reaction. In an application for HLA-DQA typing a 228 base pair long region of the polymorphic exon 2 of DQA1 gene was amplified and the denatured PCR product distributed into streptavidin-coated microtitration wells together with the detection probe and one of the catching probes. After incubation and washes, the enhancement solution was added and specific hybridisation signal detected by measuring the emitted light. A series of 100 isolated genomic DNA samples were studied using biotinylated probes specific for DQA1*01, *0101/0104, *0103/0201/0601, *0201, *03, *0401/0601, *05 and *0502 alleles with results demonstrating the capacity of the test to detect aimed alleles. A series of whole blood spot samples were also studied and the results confirmed the applicability of this modification of the test.