WorldWideScience

Sample records for broadband time-resolved spectroscopy

  1. 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.)

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

    DEFF Research Database (Denmark)

    Cooke, David; Iwaszczuk, Krzysztof; Nielsen, Kristian;

    2009-01-01

    , 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...... that the influence of fluctuations on the laser parameters during data acquisition can be minimized, and highly reproducible quantitative data can be recorded and extracted in a very efficient manner. This technique may become especially important in the high THz range, where phase noise becomes critical...

  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. Sub-nanosecond, time-resolved, broadband infrared spectroscopy using synchrotron radiation

    CERN Document Server

    Lobo, R; Reitze, D H; Tanner, D B; Carr, G L

    2001-01-01

    A facility for sub-nanosecond time-resolved (pump-probe) infrared spectroscopy has been developed at the National Synchrotron Light Source of Brookhaven National Laboratory. A mode-locked Ti:sapphire laser produces 2 ps duration, tunable near-IR pump pulses synchronized to probe pulses from a synchrotron storage ring. The facility is unique on account of the broadband infrared from the synchrotron, which allows the entire spectral range from 2 cm-1 (0.25 meV) to 20,000 cm-1 (2.5 eV) to be probed. A temporal resolution of 200 ps, limited by the infrared synchrotron-pulse duration, is achieved. A maximum time delay of 170 ns is available without gating the infrared detector. To illustrate the performance of the facility, a measurement of electron-hole recombination dynamics for an HgCdTe semiconductor film in the far- and mid infrared range is presented.

  5. TIME-RESOLVED VIBRATIONAL SPECTROSCOPY

    Energy Technology Data Exchange (ETDEWEB)

    Andrei Tokmakoff, MIT (Conference Chair); Paul Champion, Northeastern University; Edwin J. Heilweil, NIST; Keith A. Nelson, MIT; Larry Ziegler, Boston University

    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 five of 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.

  6. Time-resolved fluorescence spectroscopy

    International Nuclear Information System (INIS)

    This article addresses the evolution in time of light emitted by a molecular system after a brief photo-excitation. The authors first describe fluorescence from a photo-physical point of view and discuss the characterization of the excited state. Then, they explain some basic notions related to fluorescence characterization (lifetime and decays, quantum efficiency, so on). They present the different experimental methods and techniques currently used to study time-resolved fluorescence. They discuss basic notions of time resolution and spectral reconstruction. They briefly present some conventional methods: intensified Ccd cameras, photo-multipliers and photodiodes associated with a fast oscilloscope, and phase modulation. Other methods and techniques are more precisely presented: time-correlated single photon counting (principle, examples, and fluorescence lifetime imagery), streak camera (principle, examples), and optical methods like the Kerr optical effect (principle and examples) and fluorescence up-conversion (principle and theoretical considerations, examples of application)

  7. 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....

  8. Application of a mode-locked fiber laser for highly time resolved broadband absorption spectroscopy and laser-assisted breakdown on micro-plasmas

    International Nuclear Information System (INIS)

    Absorption spectroscopy is known to be a powerful tool to gain spatially and temporally resolved information on excited and reactive species in a plasma discharge. Furthermore, the interaction of the discharge with short intense laser pulses can trigger the ignition and the transition into other transient states of the plasma. In this context laser-assisted ‘pump-probe’ experiments involving simultaneously generated supercontinuum radiation yield highly temporally resolved and spatially well-defined information on the transient phenomena. In this paper we demonstrate the possibility for ‘pump-probe’ experiments by initiating breakdown on a picosecond time scale (‘pump’) with a high-power beam and measuring the broadband absorption with the simultaneously provided supercontinuum (‘probe’). Since both pulses are generated from the same mode-locked master oscillator, they have a strong level of synchronization. (paper)

  9. Time-Resolved Spectroscopy with SDSS

    CERN Document Server

    Bickerton, Steven; Hettinger, Thomas; Beers, Timothy; Huang, Sonya

    2011-01-01

    We present a brief technical outline of the newly-formed 'Detection of Spectroscopic Differences over Time' (DS/DT) project. Our collaboration is using the individual exposures from the SDSS spectroscopic archive to produce a uniformly-processed set of time-resolved spectra. Here we provide an overview of the properties and processing of the available data, and highlight the wide range of time baselines present in the archive.

  10. Steady state and time resolved spectroscopy of photoswitchable systems

    NARCIS (Netherlands)

    Hou, Lili

    2013-01-01

    Steady state en time resolved spectroscopie zijn twee fundamentele methodes voor het bestuderen van fotochemische processen. In dit proefschrift zijn drie zelf-opgezette spectroscopische systemen beschreven, waarmee samen met andere spectroscopische methoden verscheidende met licht schakelbare syste

  11. Time-resolved orbital angular momentum spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Noyan, Mehmet A.; Kikkawa, James M. [Department of Physics and Astronomy, The University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2015-07-20

    We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.

  12. Time-resolved orbital angular momentum spectroscopy

    International Nuclear Information System (INIS)

    We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes

  13. Time resolved spectroscopy using synchrotron infrared pulses

    Energy Technology Data Exchange (ETDEWEB)

    Carr, G.L. [Brookhaven National Lab., Upton, NY (United States). National Synchrotron Light Source; Lobo, R.P.S.M. [Brookhaven National Lab., Upton, NY (United States). National Synchrotron Light Source]|[Univ. of Florida, Gainesville, FL (United States). Physics Dept.; Hirschmugl, C.J. [Lawrence Berkeley National Lab., CA (United States). Advanced Light Source; LaVeigne, J.; Reitze, D.H.; Tanner, D.B. [Univ. of Florida, Gainesville, FL (United States). Physics Dept.

    1997-09-01

    Electron synchrotron storage rings, such as the VUV ring at the National Synchrotron Light Source (NSLS), produce short pulses of infrared (IR) radiation suitable for investigating the time-dependent phenomena in a variety of interesting experimental systems. In contrast to other pulses sources of IR, the synchrotron produces a continuum spectral output over the entire IR (and beyond), though at power levels typically below those obtained from laser systems. The infrared synchrotron radiation (IRSR) source is therefore well-suited as a probe using standard FTIR spectroscopic techniques. Here the authors describe the pump-probe spectroscopy facility being established at the NSLS and demonstrate the technique by measuring the photocarrier decay in a semiconductor.

  14. 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.

  15. Time-resolved terahertz spectroscopy of black silicon

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Jepsen, Peter Uhd;

    2010-01-01

    The ultrafast photoconductivity dynamics of black silicon is measured by time-resolved terahertz spectroscopy. Black silicon is produced by laser annealing of an a-Si:H film. We show that the decay time of the photoconductivity depends on the annealing method and fluence used in the production...

  16. 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...... 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....... produced by laser annealing of amorphous silicon lms. The amplitude and the decay time of the photoconductivity depends strongly on the method and annealing uence used in the production process. Furthermore, it is shown that by adding copper to the black silicon, the decay time of the photoconductivity can...

  17. Ultrafast time resolved vibrational spectroscopy in liquid systems

    Science.gov (United States)

    Seifert, G.; Hofmann, M.; Weidlich, K.; Graener, H.

    1996-04-01

    The ultrafast dynamics of small molecules in the liquid phase can successfully be studied tracing the relaxation pathways of vibrational excess energy. Two complementing experimental techniques, picosecond IR double resonance spectroscopy and time resolved incoherent Anti-Stokes Raman spectroscopy, are very powerful tools for such studies. The capabilities of investigations combining these methods are discussed on the example of new experimental data on liquid dichloromethane (CH2Cl2).

  18. Ultrafast time resolved vibrational spectroscopy in liquid systems

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, G.; Hofmann, M.; Weidlich, K.; Graener, H. [Physics Institute, University of Bayreuth, D-95440 Bayreuth (Germany)

    1996-04-01

    The ultrafast dynamics of small molecules in the liquid phase can successfully be studied tracing the relaxation pathways of vibrational excess energy. Two complementing experimental techniques, picosecond IR double resonance spectroscopy and time resolved incoherent Anti-Stokes Raman spectroscopy, are very powerful tools for such studies. The capabilities of investigations combining these methods are discussed on the example of new experimental data on liquid dichloromethane (CH{sub 2}Cl{sub 2}). {copyright} {ital 1996 American Institute of Physics.}

  19. 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....... The time resolution of the technique is shown to be limited by the spatial excitation profile, which for sharply focused beams can approach ~1 ps time scales....

  20. Probing Local Environments by Time-Resolved Stimulated Emission Spectroscopy

    OpenAIRE

    Ana Rei; Graham Hungerford; Michael Belsley; Ferreira, M. Isabel C.; Peter Schellenberg

    2012-01-01

    Time-resolved stimulated emission spectroscopy was employed to probe the local environment of DASPMI (4-(4-(dimethylamino)styryl)-N-methyl-pyridinium iodide) in binary solvents of different viscosity and in a sol-gel matrix. DASPMI is one of the molecules of choice to probe local environments, and the dependence of its fluorescence emission decay on viscosity has been previously used for this purpose in biological samples, solid matrices as well as in solution. The results presented in this p...

  1. Time-resolved laser-induced breakdown spectroscopy of aluminum

    Institute of Scientific and Technical Information of China (English)

    LIU Xian-yun; ZHANG Wei-jun; WANG Zhen-ya; HAO Li-qing; HUANG Ming-qiang; ZHAO Wen-wu; LONG Bo; Zhao Wei

    2008-01-01

    We develop a system to measure the elemental composition of unprepared samples using laser-induced breakdown spectroscopy (LIBS) in our laboratory, which can be used for the determination of elements in solids, liquids and aerosols. A description of the instrumentation, including laser, sample chamber and detection, is followed by a brief discussion. The time-resolved LIBS of aluminum at atmospheric pressure is presented. At the end, the possibilities and later uses of this technique are briefly discussed.

  2. Probing Local Environments by Time-Resolved Stimulated Emission Spectroscopy

    Directory of Open Access Journals (Sweden)

    Ana Rei

    2012-01-01

    Full Text Available Time-resolved stimulated emission spectroscopy was employed to probe the local environment of DASPMI (4-(4-(dimethylaminostyryl-N-methyl-pyridinium iodide in binary solvents of different viscosity and in a sol-gel matrix. DASPMI is one of the molecules of choice to probe local environments, and the dependence of its fluorescence emission decay on viscosity has been previously used for this purpose in biological samples, solid matrices as well as in solution. The results presented in this paper show that time-resolved stimulated emission of DASPMI is a suitable means to probe the viscosity of local environments. Having the advantage of a higher time resolution, stimulated emission can provide information that is complementary to that obtained from fluorescence decay measurements, making it feasible to probe systems with lower viscosity.

  3. 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....

  4. Multidimensional time-resolved spectroscopy of vibrational coherence in biopolyenes.

    Science.gov (United States)

    Buckup, Tiago; Motzkus, Marcus

    2014-01-01

    Multidimensional femtosecond time-resolved vibrational coherence spectroscopy allows one to investigate the evolution of vibrational coherence in electronic excited states. Methods such as pump-degenerate four-wave mixing and pump-impulsive vibrational spectroscopy combine an initial ultrashort laser pulse with a nonlinear probing sequence to reinduce vibrational coherence exclusively in the excited states. By carefully exploiting specific electronic resonances, one can detect vibrational coherence from 0 cm(-1) to over 2,000 cm(-1) and map its evolution. This review focuses on the observation and mapping of high-frequency vibrational coherence for all-trans biological polyenes such as β-carotene, lycopene, retinal, and retinal Schiff base. We discuss the role of molecular symmetry in vibrational coherence activity in the S1 electronic state and the interplay of coupling between electronic states and vibrational coherence.

  5. Time resolved optical emission spectroscopy of an HPPMS coating process

    International Nuclear Information System (INIS)

    This paper deals with the time resolved optical emission spectroscopy of a high power pulse magnetron sputtering (HPPMS) physical vapour deposition coating process. With an industrial coating unit CC800/9 HPPMS (CemeCon AG, Wuerselen) a (Cr,Al,Si)N coating was deposited. During the coating process, an absolute calibrated Echelle spectrometer (ESA-3000) measured the intensities of the spectral lines of chromium (Cr), aluminium (Al) and molecular bands of nitrogen (N2). Time resolved measurements enable us to calculate different parameters such as the average velocity of sputtered Al and Cr atoms or the internal plasma parameters electron density ne and electron temperature kTe with a time resolution of 20 μs. With these parameters, we determine the ionization rates of Al, Cr, Ar and Kr atoms and the deposition densities of Al and Cr atoms. Thus simulated deposition densities of 1.75 x 1020 m-2 s-1 for chromium and 1.7 x 1022 m-2 s-1 for aluminium are reached.

  6. Diagnosis of meningioma by time-resolved fluorescence spectroscopy.

    Science.gov (United States)

    Butte, Pramod V; Pikul, Brian K; Hever, Aviv; Yong, William H; Black, Keith L; Marcu, Laura

    2005-01-01

    We investigate the use of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as an adjunctive tool for the intraoperative rapid evaluation of tumor specimens and delineation of tumor from surrounding normal tissue. Tissue autofluorescence is induced with a pulsed nitrogen laser (337 nm, 1.2 ns) and the intensity decay profiles are recorded in the 370 to 500 nm spectral range with a fast digitizer (0.2 ns resolution). Experiments are conducted on excised specimens (meningioma, dura mater, cerebral cortex) from 26 patients (97 sites). Spectral intensities and time-dependent parameters derived from the time-resolved spectra of each site are used for tissue characterization. A linear discriminant analysis algorithm is used for tissue classification. Our results reveal that meningioma is characterized by unique fluorescence characteristics that enable discrimination of tumor from normal tissue with high sensitivity (>89%) and specificity (100%). The accuracy of classification is found to increase (92.8% cases in the training set and 91.8% in the cross-validated set correctly classified) when parameters from both the spectral and the time domain are used for discrimination. Our findings establish the feasibility of using TR-LIFS as a tool for the identification of meningiomas and enables further development of real-time diagnostic tools for analyzing surgical tissue specimens of meningioma or other brain tumors. PMID:16409091

  7. Nonselective and polarization effects in time-resolved optogalvanic spectroscopy

    Science.gov (United States)

    Zhechev, D.; Steflekova, V.

    2016-02-01

    Three interfering effects in optogalvanic (OG) spectroscopy are identified in a hollow cathode discharge (HCD) - OG detector. The laser beam is found to generate two nonselective processes, namely photoelectron emission (PE) from the cathode surface with a sub-breakdown bias applied, and nonresonant space ionization. The convolution of these galvanic contributions was determined experimentally as an instrumental function and a deconvolution procedure to determine the actual OG signal was developed. Specific plasma conductance is detected dependent on the polarization of the laser beam irradiating. Linearly/circularly polarized light beam is found to induce OG signals differ in amplitude (and their shape parameters in the time-resolved OG signals (TROGS)). The phenomena coherence and specific conductance are found to be in causal relationship. The additional conductance due to coherent states of atoms manifests itself as an intrinsic instrumental property of OG detector.

  8. Electron-transfer acceleration investigated by time resolved infrared spectroscopy.

    Science.gov (United States)

    Vlček, Antonín; Kvapilová, Hana; Towrie, Michael; Záliš, Stanislav

    2015-03-17

    Ultrafast electron transfer (ET) processes are important primary steps in natural and artificial photosynthesis, as well as in molecular electronic/photonic devices. In biological systems, ET often occurs surprisingly fast over long distances of several tens of angströms. Laser-pulse irradiation is conveniently used to generate strongly oxidizing (or reducing) excited states whose reactions are then studied by time-resolved spectroscopic techniques. While photoluminescence decay and UV-vis absorption supply precise kinetics data, time-resolved infrared absorption (TRIR) and Raman-based spectroscopies have the advantage of providing additional structural information and monitoring vibrational energy flows and dissipation, as well as medium relaxation, that accompany ultrafast ET. We will discuss three cases of photoinduced ET involving the Re(I)(CO)3(N,N) moiety (N,N = polypyridine) that occur much faster than would be expected from ET theories. [Re(4-N-methylpyridinium-pyridine)(CO)3(N,N)](2+) represents a case of excited-state picosecond ET between two different ligands that remains ultrafast even in slow-relaxing solvents, beating the adiabatic limit. This is caused by vibrational/solvational excitation of the precursor state and participation of high-frequency quantum modes in barrier crossing. The case of Re-tryptophan assemblies demonstrates that excited-state Trp → *Re(II) ET is accelerated from nanoseconds to picoseconds when the Re(I)(CO)3(N,N) chromophore is appended to a protein, close to a tryptophan residue. TRIR in combination with DFT calculations and structural studies reveals an interaction between the N,N ligand and the tryptophan indole. It results in partial electronic delocalization in the precursor excited state and likely contributes to the ultrafast ET rate. Long-lived vibrational/solvational excitation of the protein Re(I)(CO)3(N,N)···Trp moiety, documented by dynamic IR band shifts, could be another accelerating factor. The last

  9. A Clinical Tissue Oximeter Using NIR Time-Resolved Spectroscopy.

    Science.gov (United States)

    Fujisaka, Shin-ichi; Ozaki, Takeo; Suzuki, Tsuyoshi; Kamada, Tsuyoshi; Kitazawa, Ken; Nishizawa, Mitsunori; Takahashi, Akira; Suzuki, Susumu

    2016-01-01

    The tNIRS-1, a new clinical tissue oximeter using NIR time-resolved spectroscopy (TRS), has been developed. The tNIRS-1 measures oxygenated, deoxygenated and total hemoglobin and oxygen saturation in living tissues. Two-channel TRS measurements are obtained using pulsed laser diodes (LD) at three wavelengths, multi-pixel photon counters (MPPC) for light detection, and time-to-digital converters (TDC) for time-of-flight photon measurements. Incorporating advanced semiconductor devices helped to make the design of this small-size, low-cost and low-power TRS instrument possible. In order to evaluate the correctness and reproducibility of measurement data obtained with the tNIRS-1, a study using blood phantoms and healthy volunteers was conducted to compare data obtained from a conventional SRS device and data from an earlier TRS system designed for research purposes. The results of the study confirmed the correctness and reproducibility of measurement data obtained with the tNIRS-1. Clinical evaluations conducted in several hospitals demonstrated a high level of usability in clinical situations and confirmed the efficacy of measurement data obtained with the tNIRS-1. PMID:26782242

  10. A Clinical Tissue Oximeter Using NIR Time-Resolved Spectroscopy.

    Science.gov (United States)

    Fujisaka, Shin-ichi; Ozaki, Takeo; Suzuki, Tsuyoshi; Kamada, Tsuyoshi; Kitazawa, Ken; Nishizawa, Mitsunori; Takahashi, Akira; Suzuki, Susumu

    2016-01-01

    The tNIRS-1, a new clinical tissue oximeter using NIR time-resolved spectroscopy (TRS), has been developed. The tNIRS-1 measures oxygenated, deoxygenated and total hemoglobin and oxygen saturation in living tissues. Two-channel TRS measurements are obtained using pulsed laser diodes (LD) at three wavelengths, multi-pixel photon counters (MPPC) for light detection, and time-to-digital converters (TDC) for time-of-flight photon measurements. Incorporating advanced semiconductor devices helped to make the design of this small-size, low-cost and low-power TRS instrument possible. In order to evaluate the correctness and reproducibility of measurement data obtained with the tNIRS-1, a study using blood phantoms and healthy volunteers was conducted to compare data obtained from a conventional SRS device and data from an earlier TRS system designed for research purposes. The results of the study confirmed the correctness and reproducibility of measurement data obtained with the tNIRS-1. Clinical evaluations conducted in several hospitals demonstrated a high level of usability in clinical situations and confirmed the efficacy of measurement data obtained with the tNIRS-1.

  11. 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...... induced THz Kerr effect, indicating that free carriers are responsible for the transient index change. (C) 2016 Chinese Laser Press...

  12. Time-resolved diffuse optical spectroscopy: a differential absorption approach

    Science.gov (United States)

    Taroni, Paola; Bassi, Andrea; Spinelli, Lorenzo; Cubeddu, Rinaldo; Pifferi, Antonio

    2009-07-01

    A method was developed to estimate spectral changes of the absorption properties of turbid media from time-resolved reflectance/transmittance measurements. It was derived directly from the microscopic Beer-Lambert law, and tested against simulations and phantom measurements.

  13. Time-resolved spectroscopy of low-dimensional semiconductor structures

    Science.gov (United States)

    Murphy, Joseph R.

    This dissertation is a survey of ultrafast time-resolved optical measurements conducted on a variety of low-dimensional semiconductor systems to further the understanding of the dynamic behavior in the following systems: ZnMnTe/ZnSe quantum dots, ZnTe/ZnMnSe quantum dots, InGaAs quantum wells, CdMnSe colloidal quantum dots, multi-shell CdSe/CdMnS/CdS colloidal nanoplatelets, and graphene and graphene-related solutions and films. Using time-resolved photoluminescence to study epitaxially-grown ZnTe and ZnMnTe quantum dots in corresponding ZnMnSe and ZnSe matrices, the location dependence of manganese ions in respect to magnetic polaron formation is shown. The structure with manganese ions located in the matrix exhibited magnetic polaron behavior consistent with previous literature, whereas the structure with the magnetic ions located within the quantum dots exhibited unconventional magnetic polaron properties. These properties, including temperature and magnetic field insensitivity, were explained through the use of a model that predicted an increased internal magnetic field due to a decreased effective volume of the magnetic polaron and a higher effective temperature due to laser heating. Magneto-time-resolved photoluminescence measurements on a system of colloidal CdMnSe quantum dots show that the magnetic polaron properties differ significantly from the epitaxially grown quantum dots. First the timescales at which the magnetic polaron forms and the polarization saturates are different by more than an order of magnitude, and second, the magnetic polaron energy exhibited step-like behavior as the strength of the externally applied magnetic field is increased. The field dependent MP formation energy that is observed experimentally is explained as due to the breaking of the antiferromagnetic coupling of Mn dimers within the QDs. This model is further verified by the observation of quantized behavior in the Zeeman energy splitting. Through the use of magneto

  14. [Laser-time-resolved fluorescence spectroscopy in immunoassays].

    Science.gov (United States)

    Pan, L; Du, J; Xie, W; Du, Q; Yun, Q

    2000-06-01

    This paper described a laser-excited time-resolved fluoroimmunoassay set. It made lanthanide ion to couple the anhydrde of diethylenetriaminepentaacetic acid (DTPAA) for labeling antibodies. The experiment used polystyrene tap coated with HCV antigen as the solid phase and a chelate of the rare earth metal europium as fluorescent label. A nitrogen laser beam was used to excite the Eu3- chelates and after 60 microseconds delay time, the emission fluorescence was measured. Background fluorescence of short lifetimes caused by serum components and Raman scattering can be eliminated by set the delay time. In the system condition, fluorescent spectra and fluorescent lifetimes of Eu3+ beta-naphthoyltrifluroacetone (NTA) chelates were measured. The fluorescent lifetime value is 650 microseconds. The maximum emission wavelength is 613 nm. The linear range of europium ion concentration is 1 x 10(-7)-1 x 10(-11) g.mL-1 and the detection limit is 1 x 10(-13) g.mL-1. The relative standard deviation of determination (n = 12) for samples at 0.01 ng.mL-1 magnitude is 6.4%. Laser-TRFIA was also found to be suitable for diagnosis of HCV. The sensitivity and specificity were comparable to enzyme immunoassay. The result was obtained with laser-TRFIA for 29 human correlated well with enzyme immunoassay. PMID:12958930

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

    International Nuclear Information System (INIS)

    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. (paper)

  16. BROADBAND TIME-RESOLVED E{sub p,i}-L{sub iso} CORRELATION IN GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Frontera, F.; Guidorzi, C. [Dipartimento di Fisica, Universita di Ferrara, Via Saragat 1, I-44100 Ferrara (Italy); Amati, L.; Landi, R. [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna, Via Gobetti 101, I-40129 Bologna (Italy); In' t Zand, J., E-mail: frontera@fe.infn.it [Space Research Organization in the Netherlands, Sorbonnelaan 2, NL-3584 CA Utrecht (Netherlands)

    2012-08-01

    We report the results of a systematic study of the broadband (2-2000 keV) time-resolved prompt emission spectra of a sample of gamma-ray bursts (GRBs) detected with both Wide Field Cameras on board the BeppoSAX satellite and the BATSE experiment on board CGRO. In this first paper, we study the time-resolved dependence of the intrinsic peak energy E{sub p,i} of the E F(E) spectrum on the corresponding isotropic bolometric luminosity L{sub iso}. The E{sub p,i}-L{sub iso} relation or the equivalent relation between E{sub p,i} and the bolometric released energy E{sub iso}, derived using the time-averaged spectra of long GRBs with known redshift, is well established, but its physical origin is still a subject of discussion. In addition, some authors maintain that these relations are the result of instrumental selection effects. We find that not only a relation between the measured peak energy E{sub p} and the corresponding energy flux, but also a strong E{sub p,i} versus L{sub iso} correlation are found not only within each burst, but also are merging together the time-resolved data points from different GRBs. We do not expect significant instrumental selection effects that can affect the results obtained, apart from the fact that the GRBs in our sample are sufficiently bright to perform a time-resolved spectroscopy and that they have known redshift. If the fundamental physical process that gives rise to the GRB phenomenon does not depend on its brightness, we conclude that the E{sub p,i} versus L{sub iso} correlation found within each GRB is intrinsic to the emission process and that the correlations discovered by Amati et al. and Yonetoku et al. are likely not the result of selection effects. We also discuss the properties of the correlations found.

  17. 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....

  18. XPS for time resolved X-ray spectroscopy of plasmas

    International Nuclear Information System (INIS)

    Photoelectron spectroscopy is based on the simple energy conservation relation between a photon and an electron, hν = E /sub b/ + E /sub k/ , where hν is the photon energy, E /sub k/ is the electron kinetic energy and E /sub b/ is the binding energy of the electron ejected by the photon. In photoelectron spectroscopy, monochromatic photons are used to extract information about the various E /sub b/ 's in an atomic system by measuring E /sub k/ . By using atomic systems having a single electronic level with significant photoionization cross-section at the photon energies of interest it is also possible to find the energy of photons in a polychromatic source, again by measuring E /sub k/

  19. Time-resolved Spectroscopy of Active Binary Stars

    Science.gov (United States)

    Brown, Alexander

    EUVE has provided the first stellar coronal spectra showing individual emission lines, thereby allowing coronal modelling at a level of sophistication previously unattainable. Long EUVE observations have shown the prevalence of large-scale flaring in the coronae of active binary stars. We propose to obtain EUVE DSS spectra and photometry for 8 active binaries, four of which have never been observed by EUVE (EI Eri, AR Psc, V478 Lyr, BY Dra) and four EUV-bright systems that merit reobservation (Sigma CrB, Sigma Gem, Xi UMa, Lambda And). We shall use these observations to derive high quality quiescent coronal spectra for modelling, and to obtain new flare data. We shall try to coordinate these observations with ground-based radio observations and other spacecraft, if the scheduling allows. The proposed observations will significantly increase the available EUVE spectroscopy of active binaries.

  20. Resonant and Time-Resolved Spin Noise Spectroscopy

    Science.gov (United States)

    Song, Xinlin; Pursley, Brennan; Sih, Vanessa

    Spin noise spectroscopy is a technique which can probe the system while it remains in equilibrium. It was first demonstrated in atomic gases and then in solid state systems. Most existing spin noise measurement setups digitize the spin fluctuation signal and then analyze the power spectrum. Recently, pulsed lasers have been used to expand the bandwidth of accessible dynamics and allow direct time-domain correlation measurements. Here we develop and test a model for ultrafast pulsed laser spin noise measurements as well as a scheme to measure spin lifetimes longer than the laser repetition period. For the resonant spin noise technique, analog electronics are used to capture correlations from the extended pulse train, and the signal at a fixed time delay is measured as a function of applied magnetic field.

  1. [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.

  2. Applications of time-resolved terahertz spectroscopy in ultrafast carrier dynamics

    Institute of Scientific and Technical Information of China (English)

    Qingli Zhou; Xicheng Zhang

    2011-01-01

    1.Introduction Terahertz time-domain spectroscopy (THz-TDS)[1-3]is a powerful and coherent free-space technique in which nearly single-cycle electromagnetic pulse is generated and detected using femtosecond optical pulses.THz-TDS has been utilized as one of the important methods for material characterization in the past two decades.Because transmission or reflection of THz waves is sensitive to carrier density and mobility,an ultrafast THz-TDS system is required to provide time-resolved capability of material characterization in the THz region[4-6].In the past decade,one of the widely used time-resolved THz spectroscopy methods is optical-pump/THz probe (O/T)spectroscopy[3].%Three time-resolved terahertz (THz) spectroscopy methods (optical-pump/THz-probe spectroscopy, THz-pump/THz-probe spectroscopy, and THz-pump/optical-probe spectroscopy) are reviewed. These are used to characterize ultrafast dynamics in photo- or THz-excited semiconductors, superconductors, nanomateri-als, and other materials. In particular, the optical-pump/THz-probe spectroscopy is utilized to investigate carrier dynamics and the related intervalley scattering phenomena in semiconductors. The recent development of intense pulsed THz sources is expected to affect the research in nonlinear THz responses of various materials.

  3. Time-resolved diffusing wave spectroscopy applied to dynamic heterogeneity imaging

    CERN Document Server

    Cheikh, M; Ettori, D; Tinet, E; Avrillier, S; Tualle, J M; Cheikh, Monia; Nghiem, Ha Lien; Ettori, Dominique; Tinet, Eric; Avrillier, Sigrid; Tualle, Jean-Michel

    2006-01-01

    We report in this paper what is to our knowledge the first observation of a time-resolved diffusing wave spectroscopy signal recorded by transillumination through a thick turbid medium: the DWS signal is measured for a fixed photon transit time, which opens the possibility of improving the spatial resolution. This technique could find biomedical applications, especially in mammography.

  4. Speciation of actinides in aqueous solution by time-resolved laser-induced fluorescence spectroscopy (TRLFS)

    International Nuclear Information System (INIS)

    Time-resolved laser-induced fluorescence spectroscopy (TRLFS) as a sensitive and selective method has been applied to the speciation of actinides in aqueous solution. Studies on hydrolysis and carbonate complexation of U(VI) and on determination of hydration number of Cm(III) are reported. (author)

  5. Combined time-resolved SAXS and X-ray Spectroscopy methods

    NARCIS (Netherlands)

    Bras, W.; Nikitenko, S.; Portale, G.; Beale, A.M.; van der Eerden, A.M.J.; Detollenaere, D.

    2013-01-01

    Recently developed equipment suitable for quasi simultaneous data collection of SAXS/WAXS and X-ray spectroscopy is discussed. The main applications for this technique are foreseen to be time-resolved studies in inorganic materials relevant for catalysis research and ceramics. The equipment is descr

  6. 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.

  7. 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 of the...

  8. 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

    In this paper we report on the numerical analysis of a time-resolved terahertz (THz) spectroscopy experiment using a modified finite-difference time-domain method. Using this method, we show that ultrafast carrier dynamics can be extracted with a time resolution smaller than the duration of the T...

  9. Excitation emission and time-resolved fluorescence spectroscopy of selected varnishes used in historical musical instruments.

    Science.gov (United States)

    Nevin, Austin; Echard, Jean-Philippe; Thoury, Mathieu; Comelli, Daniela; Valentini, Gianluca; Cubeddu, Rinaldo

    2009-11-15

    The analysis of various varnishes from different origins, which are commonly found on historical musical instruments was carried out for the first time with both fluorescence excitation emission spectroscopy and laser-induced time-resolved fluorescence spectroscopy. Samples studied include varnishes prepared using shellac, and selected diterpenoid and triterpenoid resins from plants, and mixtures of these materials. Fluorescence excitation emission spectra have been collected from films of naturally aged varnishes. In parallel, time-resolved fluorescence spectroscopy of varnishes provides means for discriminating between short- (less than 2.0 ns) and long-lived (greater than 7.5 ns) fluorescence emissions in each of these complex materials. Results suggest that complementary use of the two non destructive techniques allows a better understanding of the main fluorophores responsible for the emission in shellac, and further provides means for distinguishing the main classes of other varnishes based on differences in fluorescence lifetime behaviour. Spectrofluorimetric data and time resolved spectra presented here may form the basis for the interpretation of results from future in situ fluorescence examination and time resolved fluorescence imaging of varnished musical instruments.

  10. Disentangling Multichannel Photodissociation Dynamics in Acetone by Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy.

    Science.gov (United States)

    Maierhofer, Paul; Bainschab, Markus; Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E; Koch, Markus

    2016-08-18

    For the investigation of photoinduced dynamics in molecules with time-resolved pump-probe photoionization spectroscopy, it is essential to obtain unequivocal information about the fragmentation behavior induced by the laser pulses. We present time-resolved photoelectron-photoion coincidence (PEPICO) experiments to investigate the excited-state dynamics of isolated acetone molecules triggered by two-photon (269 nm) excitation. In the complex situation of different relaxation pathways, we unambiguously identify three distinct pump-probe ionization channels. The high selectivity of PEPICO detection allows us to observe the fragmentation behavior and to follow the time evolution of each channel separately. For channels leading to fragment ions, we quantitatively obtain the fragment-to-parent branching ratio and are able to determine experimentally whether dissociation occurs in the neutral molecule or in the parent ion. These results highlight the importance of coincidence detection for the interpretation of time-resolved photochemical relaxation and dissociation studies if multiple pathways are present.

  11. Broadband terahertz spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Wenhui Fan

    2011-01-01

    1.Introduction Spanning the frequency range between the infrared (IR) radiation and microwaves,terahertz (THz) waves are,also known as T-rays,T-lux,or simply called THz,assigned to cover the electromagnetic spectrum typically from 100 GHz (1011 Hz) to 10 THz (1013 Hz),namely,from 3 mm to 30 μm in wavelength,although slightly different definitions have been quoted by different authors.For a very long time,THz region is an almost unexplored field due to its rather unique location in the electromagnetic spectrum.Well-known techniques in optical or microwave region can not be directly employed in the THz range because optical wavelengths are too short and microwave wavelengths are too long compared to THz wavelengths.%An overview of the major techniques to generate and detect THz radiation so far, especially the major approaches to generate and detect coherent ultra-short THz pulses using ultra-short pulsed laser, has been presented. And also, this paper, in particularly, focuses on broadband THz spectroscopy and addresses on a number of issues relevant to generation and detection of broadband pulsed THz radiation as well as broadband time-domain THz spectroscopy (THz-TDS) with the help of ultra-short pulsed laser. The time-domain waveforms of coherent ultra-short THz pulses from photoconductive antenna excited by femtosecond laser with different pulse durations and their corresponding Fourier-transformed spectra have been obtained via the numerical simulation of ultrafast dynamics between femtosecond laser pulse and photoconductive material. The origins of fringes modulated on the top of broadband amplitude spectrum, which is measured by electric-optic detector based on thin nonlinear crystal and extracted by fast Fourier transformation, have been analyzed and the major solutions to get rid of these fringes are discussed.

  12. Simultaneous measurements of global vibrational spectra and dephasing times of molecular vibrational modes by broadband time-resolved coherent anti-Stokes Raman scattering spectrography

    Institute of Scientific and Technical Information of China (English)

    Yin Jun; Yu Ling-Yao; Liu Xing; Wan Hui; Lin Zi-Yang; Niu Han-Ben

    2011-01-01

    In broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy with supercontinuum (SC), the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of various spectral components of SC in an enough bandwidth. By numerical simulations, the optimal experimental conditions for improving the SC are obtained. The broadband time-resolved CARS spectrography based on the SC with required temporal and spectral distributions is realised. The global molecular vibrational spectrum with well suppressed nonresonant background noise can be obtained in a single measurement. At the same time, the measurements of dephasing times of verious molecular vibrational modes can be conveniently achieved from intensities of a sequence of time-resolved CARS signals. It will be more helpful to provide a complete picture of molecular vibrations, and to exhibit a potential to understand not only both the solvent dynamics and the solute-solvent interactions, but also the mechanisms of chemical reactious in the fields of biology, chemistry and naterial science.

  13. Simultaneous measurements of global vibrational spectra and dephasing times of molecular vibrational modes by broadband time-resolved coherent anti-Stokes Raman scattering spectrography

    International Nuclear Information System (INIS)

    In broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy with supercontinuum (SC), the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of various spectral components of SC in an enough bandwidth. By numerical simulations, the optimal experimental conditions for improving the SC are obtained. The broadband time-resolved CARS spectrography based on the SC with required temporal and spectral distributions is realised. The global molecular vibrational spectrum with well suppressed nonresonant background noise can be obtained in a single measurement. At the same time, the measurements of dephasing times of various molecular vibrational modes can be conveniently achieved from intensities of a sequence of time-resolved CARS signals. It will be more helpful to provide a complete picture of molecular vibrations, and to exhibit a potential to understand not only both the solvent dynamics and the solute-solvent interactions, but also the mechanisms of chemical reactions in the fields of biology, chemistry and material science. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  14. Following [FeFe] Hydrogenase Active Site Intermediates by Time-Resolved Mid-IR Spectroscopy.

    Science.gov (United States)

    Mirmohades, Mohammad; Adamska-Venkatesh, Agnieszka; Sommer, Constanze; Reijerse, Edward; Lomoth, Reiner; Lubitz, Wolfgang; Hammarström, Leif

    2016-08-18

    Time-resolved nanosecond mid-infrared spectroscopy is for the first time employed to study the [FeFe] hydrogenase from Chlamydomonas reinhardtii and to investigate relevant intermediates of the enzyme active site. An actinic 355 nm, 10 ns laser flash triggered photodissociation of a carbonyl group from the CO-inhibited state Hox-CO to form the state Hox, which is an intermediate of the catalytic proton reduction cycle. Time-resolved infrared spectroscopy allowed us to directly follow the subsequent rebinding of the carbonyl, re-forming Hox-CO, and determine the reaction half-life to be t1/2 ≈ 13 ± 5 ms at room temperature. This gives direct information on the dynamics of CO inhibition of the enzyme. PMID:27494400

  15. Time resolving imaging spectroscopy applied to the analysis of plasmas generated by pulsed lasers

    Energy Technology Data Exchange (ETDEWEB)

    Alvira, F C; Bilmes, G M [Centro de Investigaciones Opticas (CONICET La Plata-CIC) CC 3, 1897, Gonnet, La Plata, Buenos Aires (Argentina); Ponce, L; Arronte, M, E-mail: fcalvira@ciop.unlp.edu.ar [CICATA-IPN, Unidad Altamira, Altamira 89600, Tamps (Mexico)

    2011-01-01

    Time resolved imaging spectroscopy were used to study the spatial and temporal evolution of LIBS (Laser Induced Breakdown Spectroscopy) plasmas generated in Cu substrates by laser pulses of different duration. Long laser pulses (microsecond) and short laser pulses (nanosecond) as well as multipulse emission were used for excitation. Analysis was made by using an imaging spectrometer with time resolved detection. Results show that the use of long laser excitation pulses produce emission spectra with the same signal to noise ratio, but with lower resolution than those produced with shorter ones. The different species generated in LIBS experiments as neutral or single ionized have a different spatial distribution inside the plasma. We demonstrated that using spatial discrimination procedures is possible to obtain spectra with the same signal to noise ratio than those obtained with a gating detector. In this case an appreciable advantage in cost reduction is obtained by replacing the gating detector by a cheap screen.

  16. Time resolving imaging spectroscopy applied to the analysis of plasmas generated by pulsed lasers

    International Nuclear Information System (INIS)

    Time resolved imaging spectroscopy were used to study the spatial and temporal evolution of LIBS (Laser Induced Breakdown Spectroscopy) plasmas generated in Cu substrates by laser pulses of different duration. Long laser pulses (microsecond) and short laser pulses (nanosecond) as well as multipulse emission were used for excitation. Analysis was made by using an imaging spectrometer with time resolved detection. Results show that the use of long laser excitation pulses produce emission spectra with the same signal to noise ratio, but with lower resolution than those produced with shorter ones. The different species generated in LIBS experiments as neutral or single ionized have a different spatial distribution inside the plasma. We demonstrated that using spatial discrimination procedures is possible to obtain spectra with the same signal to noise ratio than those obtained with a gating detector. In this case an appreciable advantage in cost reduction is obtained by replacing the gating detector by a cheap screen.

  17. Following [FeFe] Hydrogenase Active Site Intermediates by Time-Resolved Mid-IR Spectroscopy.

    Science.gov (United States)

    Mirmohades, Mohammad; Adamska-Venkatesh, Agnieszka; Sommer, Constanze; Reijerse, Edward; Lomoth, Reiner; Lubitz, Wolfgang; Hammarström, Leif

    2016-08-18

    Time-resolved nanosecond mid-infrared spectroscopy is for the first time employed to study the [FeFe] hydrogenase from Chlamydomonas reinhardtii and to investigate relevant intermediates of the enzyme active site. An actinic 355 nm, 10 ns laser flash triggered photodissociation of a carbonyl group from the CO-inhibited state Hox-CO to form the state Hox, which is an intermediate of the catalytic proton reduction cycle. Time-resolved infrared spectroscopy allowed us to directly follow the subsequent rebinding of the carbonyl, re-forming Hox-CO, and determine the reaction half-life to be t1/2 ≈ 13 ± 5 ms at room temperature. This gives direct information on the dynamics of CO inhibition of the enzyme.

  18. 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 not harmonic with respect to each other. Our method allows not only twice as fast data acquisition but also minimization of noise connected to slowly varying laser power fluctuations and timing instabilities. Our use of the nonlinear crystal N-benzyl-2-methyl-4-nitroaniline (BNA) enables time-resolved THz...... spectroscopy to beyond 5 THz, thereby highlighting that the presented method is especially valuable at higher frequencies where phase errors in the data acquisition become increasingly important....

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

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    a parallel plate waveguide, termed time-resolved THz waveguide spectroscopy. The interaction of the THz radiation with the sample is then enhanced by travelling along the material over lengths of cm's instead of through it where the length can be nm's. We highlight the performance of this technique...... by examining photocarriers induced in Si and show a spin-off technique where we can use the photocarriers to control the propagation of the THz pulse within the waveguide....

  20. A beamline for time-resolved extreme ultraviolet and soft x-ray spectroscopy

    OpenAIRE

    Grilj, Jakob; Sistrunk, Emily; Koch, Markus; Gühr, Markus

    2013-01-01

    High harmonic generation is a convenient way to obtain extreme ultraviolet light from table-top laser systems and the experimental tools to exploit this simple and powerful light source for time-resolved spectroscopy are being developed by several groups. For these applications, brightness and stability of the high harmonic generation is a key feature. This article focuses on practical aspects in the generation of extreme ultraviolet pulses with ultrafast commercial lasers, namely generation ...

  1. Echelle-MEPSICRON time-resolved spectroscopy of the dwarf nova SS Cygni

    International Nuclear Information System (INIS)

    High-dispersion time-resolved spectroscopy of the dwarf nova SS Cygni was obtained during two consecutive days at the end of an outburst. The emission lines present a double-peaked profile with a peak-to-peak separation of 526±14 km s-1. The lines have a complex structure which includes a narrow asymmetric component coming from a hot spot in the accretion disc or from the chromosphere of the red dwarf. (author)

  2. Echelle-MEPSICRON time-resolved spectroscopy of the dwarf nova SS Cygni

    Energy Technology Data Exchange (ETDEWEB)

    Echevarria, J.; Tapia, M. (Universidad Nacional Autonoma de Mexico, Baja California (Mexico). Inst. de Astronomia); Diego, F. (Institute of Oceanographic Sciences, Godalming (UK)); Costero, R.; Ruiz, E.; Salas, L.; Gutierrez, L.; Enriquez, R. (Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Astronomia)

    1989-10-15

    High-dispersion time-resolved spectroscopy of the dwarf nova SS Cygni was obtained during two consecutive days at the end of an outburst. The emission lines present a double-peaked profile with a peak-to-peak separation of 526{plus minus}14 km s{sup -1}. The lines have a complex structure which includes a narrow asymmetric component coming from a hot spot in the accretion disc or from the chromosphere of the red dwarf. (author).

  3. Time-Resolved Photoluminescence Spectroscopy: A Novel Technique for Determination of Luminescence of Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    ZHENG Zhu-Hong; SHEN De-Zhen

    2007-01-01

    @@ The time-resolved photoluminescence (PL) spectroscopy measured by the gradually increasing start delay time is utilized as a tool for the determination of the luminescence of quantum dots (QDs). The luminescence evolution of self-assembled CdSe QDs during the luminescence decay is fully revealed in terms of the experiment technique.The characteristic narrow luminescence lines of self-assembled CdSe QDs are obtained with increasing start delay time.

  4. 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.

  5. 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.

  6. 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

    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......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...

  7. Time-resolved spatially offset Raman spectroscopy for depth analysis of diffusely scattering layers.

    Science.gov (United States)

    Iping Petterson, Ingeborg E; Dvořák, Patrick; Buijs, Joost B; Gooijer, Cees; Ariese, Freek

    2010-12-01

    The objective of this study is to use time-resolved (TR) Raman spectroscopy, spatially offset Raman spectroscopy (SORS), and a combination of these approaches to obtain high quality Raman spectra from materials hidden underneath an opaque layer. Both TR Raman and SORS are advanced techniques that allow for an increased relative selectivity of photons from deeper layers within a sample. Time-resolved detection reduces fluorescence background, and the selectivity for the second layer is improved. By combining this with spatially offset excitation we additionally increased selectivity for deeper layers. Test samples were opaque white polymer blocks of several mm thicknesses. Excitation was carried out with a frequency-doubled Ti:sapphire laser at 460 nm, 3 ps pulse width and 76 MHz repetition rate. Detection was either with a continuous-wave CCD camera or in time-resolved mode using an intensified CCD camera with a 250 ps gate width. The Raman photons were collected in backscatter mode, with or without lateral offset. By measuring the delay of the Raman signal from the second layer (polyethylene terephthalate/PET/Arnite), the net photon migration speeds through Teflon, polythene, Delrin and Nylon were determined. Raman spectra could be obtained from a second layer of PET through Teflon layers up to 7 mm of thickness. The ability to obtain chemical information through layers of diffusely scattering materials has powerful potential for biomedical applications.

  8. Noninvasive assessment of breast cancer risk using time-resolved diffuse optical spectroscopy

    Science.gov (United States)

    Taroni, Paola; Pifferi, Antonio; Quarto, Giovanna; Spinelli, Lorenzo; Torricelli, Alessandro; Abbate, Francesca; Villa, Anna; Balestreri, Nicola; Menna, Simona; Cassano, Enrico; Cubeddu, Rinaldo

    2010-11-01

    Breast density is a recognized strong and independent risk factor for breast cancer. We propose the use of time-resolved transmittance spectroscopy to estimate breast tissue density and potentially provide even more direct information on breast cancer risk. Time-resolved optical mammography at seven wavelengths (635 to 1060 nm) is performed on 49 subjects. Average information on breast tissue of each subject is obtained on oxy- and deoxyhemoglobin, water, lipids, and collagen content, as well as scattering amplitude and power. All parameters, except for blood volume and oxygenation, correlate with mammographic breast density, even if not to the same extent. A synthetic optical index proves to be quite effective in separating different breast density categories. Finally, the estimate of collagen content as a more direct means for the assessment of breast cancer risk is discussed.

  9. 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

  10. 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.

  11. Investigation of hydrogen atom addition to vinyl monomers by time resolved ESR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Beckert, D.; Mehler, K.

    1983-07-01

    By means of time resolved ESR spectroscopy in the microsecond time scale the H atom addition to different vinyl monomers was investigated. The H atoms produced by pulse radiolysis of aqueous solutions show a strong recombination CIDEP effect which also allows the recombination rate constant of H atoms to be determined. By analysis of ESR time profiles with the modified Bloch equations the relaxation times T/sub 1/, T/sub 2/, the polarization factors and the chemical rate constants with scavengers were obtained. Besides the H atom addition rate constants to different vinyl monomers the structure of the monomer radical was determined for acrylic acid.

  12. 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...... described by a Kramers-Kronig compatible Jonscher-type power law with exponent between 0.5 and 1 suggesting that interchain hopping in the polymer or between nanorods occurs at frequencies higher than 3 THz immediately after photoexcitation....

  13. 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.)

  14. A beamline for time-resolved extreme ultraviolet and soft x-ray spectroscopy

    CERN Document Server

    Grilj, Jakob; Koch, Markus; Gühr, Markus

    2013-01-01

    High harmonic generation is a convenient way to obtain extreme ultraviolet light from table-top laser systems and the experimental tools to exploit this simple and powerful light source for time-resolved spectroscopy are being developed by several groups. For these applications, brightness and stability of the high harmonic generation is a key feature. This article focuses on practical aspects in the generation of extreme ultraviolet pulses with ultrafast commercial lasers, namely generation parameters and online monitoring as well as analysis of generation yield and stability.

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

    Science.gov (United States)

    Miaja-Avila, Luis; O'Neil, Galen C.; Joe, Young I.; Alpert, Bradley K.; Damrauer, Niels H.; Doriese, William B.; Fatur, Steven M.; Fowler, Joseph W.; Hilton, Gene C.; Jimenez, Ralph; Reintsema, Carl D.; Schmidt, Daniel R.; Silverman, Kevin L.; Swetz, Daniel S.; Tatsuno, Hideyuki; Ullom, Joel N.

    2016-07-01

    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.

  16. A versatile and reconfigurable setup for all-terahertz time-resolved pump-probe spectroscopy

    Science.gov (United States)

    Elezzabi, A. Y.; Maraghechi, P.

    2012-05-01

    A versatile optical setup for all-terahertz (THz) time resolved pump-probe spectroscopy was designed and tested. By utilizing a dual THz pulse generator emitter module, independent and synchronized THz radiation pump and probe pulses were produced, thus eliminating the need for THz beam splitters and the limitations associated with their implementation. The current THz setup allows for precise control of the electric fields splitting ratio between the THz radiation pump and probe pulses, as well as in-phase, out-of-phase, and polarization dependent pump-probe spectroscopy. Since the present THz pump-probe setup does not require specialized THz radiation optical components, such as phase shifters, polarization rotators, or wide bandwidth beam splitters, it can be easily implemented with minimal alterations to a conventional THz time domain spectroscopy system. The present setup is valuable for studying the time dynamics of THz coherent phenomena in solid-state, chemical, and biological systems.

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

    Science.gov (United States)

    Yankelevich, Diego R; Ma, Dinglong; Liu, Jing; Sun, Yang; Sun, Yinghua; Bec, Julien; Elson, Daniel S; Marcu, Laura

    2014-03-01

    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 time-resolved fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores.

  18. 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.

  19. Time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water

    Institute of Scientific and Technical Information of China (English)

    WU Jiang-lai; LU Yuan; Li Ying; CHENG Kai; GUO Jin-jia; ZHENG Rong-er

    2011-01-01

    @@ The laser induced breakdown spectroscopy (LIBS) is an element analysis technique with the advantages of real time detection, simultaneous multi-element identification, and in-situ and stand-off capacities.To evaluate its potential of ocean applications, in this paper, the time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water is investigated.With the optimum experimental parameters, the plasma emission lifetime is determined to be about 500 ns with 532 nm laser excitation, and 1000 ns with 1064 nm laser excitation.The lowest detection concentration of 50ppm is achieved for calcium detection in CaC12 water solution using the 532 nm LIBS.Even better detection sensitivity is achieved using the 1064 nm LIBS, and the resulted lowest detection concentration of calcium is 25 ppm.The results suggest that it is feasible to develop LIBS as an on-line sensor for metal element monitoring in the sea.

  20. Capturing interfacial photoelectrochemical dynamics with picosecond time-resolved X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Neppl, Stefan; Shavorskiy, Andrey; Zegkinoglou, Ioannis; Fraund, Matthew; Slaughter, Daniel S; Troy, Tyler; Ziemkiewicz, Michael P; Ahmed, Musahid; Gul, Sheraz; Rude, Bruce; Zhang, Jin Z; Tremsin, Anton S; Glans, Per-Anders; Liu, Yi-Sheng; Wu, Cheng Hao; Guo, Jinghua; Salmeron, Miquel; Bluhm, Hendrik; Gessner, Oliver

    2014-01-01

    Time-resolved core-level spectroscopy using laser pulses to initiate and short X-ray pulses to trace photoinduced processes has the unique potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics in complex systems. Time-domain studies using transient X-ray absorption and emission techniques have proven extremely valuable to investigate electronic and structural dynamics in isolated and solvated molecules. Here, we describe the implementation of a picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS) technique at the Advanced Light Source (ALS) and its application to monitor photoinduced electron dynamics at the technologically pertinent interface formed by N3 dye molecules anchored to nanoporous ZnO. Indications for a dynamical chemical shift of the Ru3d photoemission line originating from the N3 metal centre are observed ∼30 ps after resonant HOMO-LUMO excitation with a visible laser pump pulse. The transient changes in the TRXPS spectra are accompanied by a characteristic surface photovoltage (SPV) response of the ZnO substrate on a pico- to nanosecond time scale. The interplay between the two phenomena is discussed in the context of possible electronic relaxation and recombination pathways that lead to the neutralisation of the transiently oxidised dye after ultrafast electron injection. A detailed account of the experimental technique is given including an analysis of the chemical modification of the nano-structured ZnO substrate during extended periods of solution-based dye sensitisation and its relevance for studies using surface-sensitive spectroscopy techniques.

  1. Time-resolved photoelectric spectroscopy of photorefractive CdTe:V crystals

    Energy Technology Data Exchange (ETDEWEB)

    Gnatenko, Yu P [Institute of Physics of NASU, 46 Prospekt Nauky, 03028 Kyiv (Ukraine); Piryatinski, Yu P [Institute of Physics of NASU, 46 Prospekt Nauky, 03028 Kyiv (Ukraine); Bukivskij, P M [Institute of Physics of NASU, 46 Prospekt Nauky, 03028 Kyiv (Ukraine); Kolendryckyj, D D [Institute of Physics of NASU, 46 Prospekt Nauky, 03028 Kyiv (Ukraine); Shigiltchoff, O A [Institute of Physics of NASU, 46 Prospekt Nauky, 03028 Kyiv (Ukraine); Gamernyk, R V [Lviv National University, 8 Kyrylo and Mefodiy Street, 29005 Lviv (Ukraine)

    2006-10-25

    The time-resolved photoelectric spectroscopy technique was used for the characterization of semi-insulating CdTe:V crystals using a short light pulse with 9 ns duration from a nitrogen laser (337.1 nm). The stationary monochromatic illumination of crystals let us measure the time-resolved photocurrent caused by the detrapping of the electrons photogenerated by the pulse laser excitation. The dependence of the intensity of pulse photocurrent on the energy of additional monochromatic illumination in the photorefractive CdTe:V crystals with the delay time t{sub d} = 5 ns, which corresponds to its maximum value, was investigated. The spectral dependence of pulse photocurrent produced by the detrapping process of electrons in CdTe:V crystals was measured under different intensities of the applied electric field. It is shown that the additional illumination at h-bar{omega}

  2. Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy.

    Science.gov (United States)

    Wilkinson, Iain; Boguslavskiy, Andrey E; Mikosch, Jochen; Bertrand, Julien B; Wörner, Hans Jakob; Villeneuve, David M; Spanner, Michael; Patchkovskii, Serguei; Stolow, Albert

    2014-05-28

    The excited state dynamics of isolated sulfur dioxide molecules have been investigated using the time-resolved photoelectron spectroscopy and time-resolved photoelectron-photoion coincidence techniques. Excited state wavepackets were prepared in the spectroscopically complex, electronically mixed (B̃)(1)B1/(Ã)(1)A2, Clements manifold following broadband excitation at a range of photon energies between 4.03 eV and 4.28 eV (308 nm and 290 nm, respectively). The resulting wavepacket dynamics were monitored using a multiphoton ionisation probe. The extensive literature associated with the Clements bands has been summarised and a detailed time domain description of the ultrafast relaxation pathways occurring from the optically bright (B̃)(1)B1 diabatic state is presented. Signatures of the oscillatory motion on the (B̃)(1)B1/(Ã)(1)A2 lower adiabatic surface responsible for the Clements band structure were observed. The recorded spectra also indicate that a component of the excited state wavepacket undergoes intersystem crossing from the Clements manifold to the underlying triplet states on a sub-picosecond time scale. Photoelectron signal growth time constants have been predominantly associated with intersystem crossing to the (c̃)(3)B2 state and were measured to vary between 750 and 150 fs over the implemented pump photon energy range. Additionally, pump beam intensity studies were performed. These experiments highlighted parallel relaxation processes that occurred at the one- and two-pump-photon levels of excitation on similar time scales, obscuring the Clements band dynamics when high pump beam intensities were implemented. Hence, the Clements band dynamics may be difficult to disentangle from higher order processes when ultrashort laser pulses and less-differential probe techniques are implemented.

  3. Structure-activity relationships of heterogeneous catalysts from time-resolved X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Knowing the composition and the evolution of the bulk structure of a heterogeneous catalyst under working conditions (in situ) is a pre-requisite for understanding structure-activity relationships. X-ray absorption spectroscopy can be employed to study a catalytically active material in situ. In addition to steady-state investigations, the technique permits experiments with a time-resolution in the sub-second range to elucidate the solid-state kinetics of the reactions involved. Combined with mass spectrometry, the evolution of the short-range order structure of a heterogeneous catalyst, the average valence of the constituent metals, and the phase composition can be obtained. Here we present results obtained from time-resolved studies on the reduction of MoO3 in propene and in propene and oxygen

  4. 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...... for enhancing the interaction of THz radiation with thin lms to the point where spectroscopy on 20 nm-thick layers of water have been performed.[2] A natural extension ofthis technique is to examine photoexcited samples inside the waveguide, with the addition of a second femtosecond excitation pulse. Here we...... demonstrate such a technique for time-resolved optical pump-THz probe measurements of materials embedded within a parallel plate waveguide. This is made possible by replacing one of the plates with a transparent conducting oxide, which provides sufcient electrical conductivity to guide the THz pulse, yet...

  5. Quantitative interpretation of time-resolved coherent anti-Stokes Raman spectroscopy with all Gaussian pulses

    CERN Document Server

    Ariunbold, Gombojav O

    2016-01-01

    Coherent Raman scattering spectroscopy is studied purposely, with the Gaussian ultrashort pulses as a hands-on elucidatory extraction tool of the clean coherent Raman resonant spectra from the overall measured data contaminated with the non-resonant four wave mixing background. The integral formulae for both the coherent anti-Stokes and Stokes Raman scattering are given in the semiclassical picture, and the closed-form solutions in terms of a complex error function are obtained. An analytic form of maximum enhancement of pure coherent Raman spectra at threshold time delay depending on bandwidth of probe pulse is also obtained. The observed experimental data for pyridine in liquid-phase are quantitatively elucidated and the inferred time-resolved coherent Raman resonant results are reconstructed with a new insight.

  6. Time-resolved luminescence spectroscopy of structurally disordered K3WO3F3 crystals

    Science.gov (United States)

    Omelkov, S. I.; Spassky, D. A.; Pustovarov, V. A.; Kozlov, A. V.; Isaenko, L. I.

    2016-08-01

    Three emission centers of exciton-like origin, with distinct relaxation time, emission and excitation spectra were revealed in K3WO3F3 and described taking into account its structural disordering. Low-temperature monoclinic phase of K3WO3F3 features few anion sites with mixed oxygen/fluorine occupancy per [WO3F3] octahedron. Therefore, different kinds of distorted octahedra form, providing different luminescence centers. The time-resolved luminescence spectroscopy technique was applied to distinguish these centers. The simultaneous thermal quenching of them above ∼200 K was qualitatively explained involving dynamic structural disorder of the compound. The energy transfer mechanism between centers was found and tentatively described by the diffusion of excitons. Apart from intrinsic luminescence, the PL of defect-related centers was discovered and the role of shallow charge carrier traps in the low-temperature persistent luminescence was revealed.

  7. Time-resolved Fourier transform intracavity spectroscopy with a Cr2+:ZnSe laser

    CERN Document Server

    Picqué, N; Guelachvili, G; Sorokin, E; Sorokina, I T; Picqu\\'{e}, Nathalie; Gueye, Fatou; Guelachvili, Guy; Sorokin, Evgeni; Sorokina, Irina T.

    2005-01-01

    Intracavity laser absorption spectroscopy (ICLAS) with an evacuated Cr2+: ZnSe laser is performed with a high-resolution time-resolved Fourier transform interferometer with a minimum detectable absorption coefficient equal to 4 10-9 cm-1 Hz-1/2 in the 2.5$\\mu$m region. This represents the extreme limit presently reached in the infrared by ICLAS with Doppler limited resolution. The broad gain band of the crystal allows a spectral coverage at most equal to 125 nm, wide enough to see entire vibration bands. Weak CO2 bands observed up to now only in the Venus atmosphere are recorded for the first time in a laboratory. H2O detection limit down to 0.9 ppbv is also demonstrated.

  8. Time-resolved laser fluorescence spectroscopy of UO2(CO3)3(4-).

    Science.gov (United States)

    Jung, E C; Cho, H-R; Baik, M H; Kim, H; Cha, W

    2015-11-21

    The objective of the present study is to examine the luminescence characteristics of UO2(CO3)3(4-) in detail using time-resolved laser fluorescence spectroscopy. The peak wavelengths and lifetime of UO2(CO3)3(4-) were determined at room temperature using the two excitation laser wavelengths of 266 and 448 nm. The peak wavelengths in the luminescence spectrum exhibited hypsochromic shifts compared with those of UO2(2+). The lifetime determined from several samples containing various uranium concentrations was 8.9 ± 0.8 ns. Explanations for the hindrance to the observation of the luminescence spectrum of UO2(CO3)3(4-) in previous investigations are discussed. The representative experimental parameters, which might interrupt the measurement of weak luminescence, are the insertion delay time of the detection device, the overlapped luminescence of the background materials and the primary inner filter effect in the sample solution.

  9. Reaction of CH radical with O2 by time-resolved FTIR spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The reaction of CH radical with O2 has been experimentally investigated by time-resolved Fourier transform IR emission spectroscopy. CH radicals were generated by multi-photon UV laser photolysis of bromoform (CHBr3) in gaseous phase. Highly vibrationally excited product CO (v =1-12) with a near Boltzmann distribution was observed after the reaction. The vibrational temperature of CO is estimated as high as 14400(1400 K and the averaged vibrational energy is about 25.8 kcal(mol-1. The emission intensity of CO is not sensitive to the quenching gas, which indicates that there is no early barrier in the reaction of CH+O2. However, the theoretically predicted product CO2 has not been found in the experiment.

  10. Time-resolved spectroscopy of spin-current emission from a magnetic insulator

    Science.gov (United States)

    Tateno, Yuma; Fukami, Masaya; Tashiro, Takaharu; Ando, Kazuya

    2016-05-01

    We demonstrate time-resolved spectroscopy of spin-current emission from a magnetic insulator using the inverse spin Hall effect (ISHE). We measured magnetic field dependence of the spin-current emission in the time domain and found that the spectral shape of the ISHE voltage changes with time. The change in the spectral shape is due to field and power dependent temporal oscillation of the spin pumping driven by parametric magnons. The observed oscillating spin-current emission driven by dipole-exchange magnons is well reproduced by a model calculation based on the S theory. In contrast, the spin-current emission driven by short-wavelength exchange magnons cannot be reproduced with this model, illustrating an important role of higher-order nonlinear effects in the spin-current emission.

  11. Label-Free Toxin Detection by Means of Time-Resolved Electrochemical Impedance Spectroscopy

    Science.gov (United States)

    Chai, Changhoon; Takhistov, Paul

    2010-01-01

    The real-time detection of trace concentrations of biological toxins requires significant improvement of the detection methods from those reported in the literature. To develop a highly sensitive and selective detection device it is necessary to determine the optimal measuring conditions for the electrochemical sensor in three domains: time, frequency and polarization potential. In this work we utilized a time-resolved electrochemical impedance spectroscopy for the detection of trace concentrations of Staphylococcus enterotoxin B (SEB). An anti-SEB antibody has been attached to the nano-porous aluminum surface using 3-aminopropyltriethoxysilane/glutaraldehyde coupling system. This immobilization method allows fabrication of a highly reproducible and stable sensing device. Using developed immobilization procedure and optimized detection regime, it is possible to determine the presence of SEB at the levels as low as 10 pg/mL in 15 minutes. PMID:22315560

  12. Label-Free Toxin Detection by Means of Time-Resolved Electrochemical Impedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Paul Takhistov

    2010-01-01

    Full Text Available The real-time detection of trace concentrations of biological toxins requires significant improvement of the detection methods from those reported in the literature. To develop a highly sensitive and selective detection device it is necessary to determine the optimal measuring conditions for the electrochemical sensor in three domains: time, frequency and polarization potential. In this work we utilized a time-resolved electrochemical impedance spectroscopy for the detection of trace concentrations of Staphylococcus enterotoxin B (SEB. An anti-SEB antibody has been attached to the nano-porous aluminum surface using 3-aminopropyltriethoxysilane/glutaraldehyde coupling system. This immobilization method allows fabrication of a highly reproducible and stable sensing device. Using developed immobilization procedure and optimized detection regime, it is possible to determine the presence of SEB at the levels as low as 10 pg/mL in 15 minutes.

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

    International Nuclear Information System (INIS)

    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

  14. 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.

  15. Time-resolved X-ray spectroscopies of chemical systems: New perspectives.

    Science.gov (United States)

    Chergui, Majed

    2016-05-01

    The past 3-5 years have witnessed a dramatic increase in the number of time-resolved X-ray spectroscopic studies, mainly driven by novel technical and methodological developments. The latter include (i) the high repetition rate optical pump/X-ray probe studies, which have greatly boosted the signal-to-noise ratio for picosecond (ps) X-ray absorption spectroscopy studies, while enabling ps X-ray emission spectroscopy (XES) at synchrotrons; (ii) the X-ray free electron lasers (XFELs) are a game changer and have allowed the first femtosecond (fs) XES and resonant inelastic X-ray scattering experiments to be carried out; (iii) XFELs are also opening the road to the development of non-linear X-ray methods. In this perspective, I will mainly focus on the most recent technical developments and briefly address some examples of scientific questions that have been addressed thanks to them. I will look at the novel opportunities in the horizon. PMID:27376102

  16. 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.

  17. Time-resolved X-ray spectroscopies of chemical systems: New perspectives

    Directory of Open Access Journals (Sweden)

    Majed Chergui

    2016-05-01

    Full Text Available The past 3–5 years have witnessed a dramatic increase in the number of time-resolved X-ray spectroscopic studies, mainly driven by novel technical and methodological developments. The latter include (i the high repetition rate optical pump/X-ray probe studies, which have greatly boosted the signal-to-noise ratio for picosecond (ps X-ray absorption spectroscopy studies, while enabling ps X-ray emission spectroscopy (XES at synchrotrons; (ii the X-ray free electron lasers (XFELs are a game changer and have allowed the first femtosecond (fs XES and resonant inelastic X-ray scattering experiments to be carried out; (iii XFELs are also opening the road to the development of non-linear X-ray methods. In this perspective, I will mainly focus on the most recent technical developments and briefly address some examples of scientific questions that have been addressed thanks to them. I will look at the novel opportunities in the horizon.

  18. Advancements in time-resolved x-ray laser induced time-of-flight photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A J; Dunn, J; Widmann, K; Ao, T; Ping, Y; Hunter, J; Ng, A

    2005-07-28

    Time-resolved soft x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) metal foils and bulk semiconductors. Single-shot soft x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution was used in combination with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated metal foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.3-2.5 mJ laser energy focused in a large 500 x 700 {micro}m{sup 2} spot to create heated conditions of 0.2-1.8 x 10{sup 12} W cm{sup -2} intensity. The unique LLNL COMET compact tabletop soft x-ray laser source provided the necessary high photon flux, highly monoenergetic, picosecond pulse duration, and coherence for observing the evolution of changes in the valence band electronic structure of laser heated metals and semiconductors with picosecond time resolution. This work demonstrates the continuing development of a powerful new technique for probing reaction dynamics and changes of local order on surfaces on their fundamental timescales including phenomena such as non-thermal melting, chemical bond formation, intermediate reaction steps, and the existence of transient reaction products.

  19. Time-resolved X-ray spectroscopies of chemical systems: New perspectives.

    Science.gov (United States)

    Chergui, Majed

    2016-05-01

    The past 3-5 years have witnessed a dramatic increase in the number of time-resolved X-ray spectroscopic studies, mainly driven by novel technical and methodological developments. The latter include (i) the high repetition rate optical pump/X-ray probe studies, which have greatly boosted the signal-to-noise ratio for picosecond (ps) X-ray absorption spectroscopy studies, while enabling ps X-ray emission spectroscopy (XES) at synchrotrons; (ii) the X-ray free electron lasers (XFELs) are a game changer and have allowed the first femtosecond (fs) XES and resonant inelastic X-ray scattering experiments to be carried out; (iii) XFELs are also opening the road to the development of non-linear X-ray methods. In this perspective, I will mainly focus on the most recent technical developments and briefly address some examples of scientific questions that have been addressed thanks to them. I will look at the novel opportunities in the horizon.

  20. Standoff Time-Resolved Laser-Based Spectroscopy Tools for Sample Characterization and Biosignature Detection

    Science.gov (United States)

    Gasda, P. J.; Acosta-Maeda, T.; Lucey, P. G.; Misra, A. K.; Sharma, S. K.; Taylor, J.

    2014-12-01

    The NASA Mars2020 rover will be searching for signs of past habitability and past life on Mars. Additionally, the rover mission will prepare a cache of highly significant samples for a future sample return mission. NASA requires these samples to be well characterized; the instruments on the rover must be capable of fine-scale in situ mineralogical or elemental analysis with emphasis on biosignature detection or characterization. We have been developing multiple standoff laser-based instruments at the University of Hawaii, Manoa that are capable of fine-scale in situ chemical analysis and biosignatures detection. By employing a time-resolved spectroscopy, we can perform elemental analysis with Laser-Induced Breakdown Spectroscopy (LIBS), mineral and organic analysis with Raman spectroscopy, and biosignature detection with Laser-Induced Fluorescence (LIF). Each of these techniques share the same optics and detection equipment, allowing us to integrate them into a single, compact instrument. High time-resolution (~100 ns/pulse) is the key to this instrument; with it, the detector only records data when the signal is the brightest. Spectra can be taken during the day, LIBS can be measured without a plasma light background, and the Raman signal can be separated from the mineral fluorescence signal. Since bio-organics have very short fluorescence lifetimes, the new instrument can be used to unambiguously detect bio-organics. The prototype uses a low power (0.5 mJ/pulse) 532 nm laser with a detection limit of drill holes, or outcrops, and then allow the slower but more precise instruments on the rover to characterize the regions of interest. Either of these prototypes would be ideally suited for future NASA missions, including human exploration missions. The next iterations of the instruments will be designed specifically for future astronaut explorers.

  1. 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,...

  2. Carrier Formation Dynamics of Organic Photovoltaics as Investigated by Time-Resolved Spectroscopy

    Directory of Open Access Journals (Sweden)

    Kouhei Yonezawa

    2012-01-01

    Full Text Available Bulk heterojunction (BHJ based on a donor (D polymer and an acceptor (A fullerene derivative is a promising organic photovoltaics (OPV. In order to improve the incident photon-to-current efficiency (IPCE of the BHJ solar cell, a comprehensive understanding of the ultrafast dynamics of excited species, such as singlet exciton (D*, interfacial charge-transfer (CT state, and carrier (D+, is indispensable. Here, we performed femtosecond time-resolved spectroscopy of two prototypical BHJ blend films: poly(3-hexylthiophene (P3HT/[6,6]-phenyl C61-butyric acid methyl ester (PCBM blend film and poly(9,9′-dioctylfluorene-co-bithiophene (F8T2/[6,6]-phenyl C71-butyric acid methyl ester (PC70BM blend film. We decomposed differential absorption spectra into fast, slow, and constant components via two-exponential fitting at respective probe photon energies. The decomposition procedure clearly distinguished photoinduced absorptions (PIAs due to D*, CT, and D+. Based on these assignments, we will compare the charge dynamics between the F8T2/PC70BM and P3HT/PCBM blend films.

  3. Light adaptation of the unicellular red alga, Cyanidioschyzon merolae, probed by time-resolved fluorescence spectroscopy.

    Science.gov (United States)

    Ueno, Yoshifumi; Aikawa, Shimpei; Kondo, Akihiko; Akimoto, Seiji

    2015-08-01

    Photosynthetic organisms change the quantity and/or quality of their pigment-protein complexes and the interactions among these complexes in response to light conditions. In the present study, we analyzed light adaptation of the unicellular red alga Cyanidioschyzon merolae, whose pigment composition is similar to that of cyanobacteria because its phycobilisomes (PBS) lack phycoerythrin. C. merolae were grown under different light qualities, and their responses were measured by steady-state absorption, steady-state fluorescence, and picosecond time-resolved fluorescence spectroscopies. Cells were cultivated under four monochromatic light-emitting diodes (blue, green, yellow, and red), and changes in pigment composition and energy transfer were observed. Cells grown under blue and green light increased their relative phycocyanin levels compared with cells cultured under white light. Energy-transfer processes to photosystem I (PSI) were sensitive to yellow and red light. The contribution of direct energy transfer from PBS to PSI increased only under yellow light, while red light induced a reduction in energy transfer from photosystem II to PSI and an increase in energy transfer from light-harvesting chlorophyll protein complex I to PSI. Differences in pigment composition, growth, and energy transfer under different light qualities are discussed. PMID:25577254

  4. Electronic structure dynamics in a low bandgap polymer studied by time-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Cappel, Ute B; Plogmaker, Stefan; Terschlüsen, Joachim A; Leitner, Torsten; Johansson, Erik M J; Edvinsson, Tomas; Sandell, Anders; Karis, Olof; Siegbahn, Hans; Svensson, Svante; Mårtensson, Nils; Rensmo, Håkan; Söderström, Johan

    2016-08-01

    Means to measure the temporal evolution following a photo-excitation in conjugated polymers are a key for the understanding and optimization of their function in applications such as organic solar cells. In this paper we study the electronic structure dynamics by direct pump-probe measurements of the excited electrons in such materials. Specifically, we carried out a time-resolved photoelectron spectroscopy (TRPES) study of the polymer PCPDTBT by combining an extreme ultraviolet (XUV) high harmonic generation source with a time-of-flight spectrometer. After excitation to either the 1st excited state or to a higher excited state, we follow how the electronic structure develops and relaxes on the electron binding energy scale. Specifically, we follow a less than 50 fs relaxation of the higher exited state and a 10 times slower relaxation of the 1st excited state. We corroborate the results using DFT calculations. Our study demonstrates the power of TRPES for studying photo-excited electron energetics and dynamics of solar cell materials. PMID:27440450

  5. Time-resolved spectroscopy of mitochondria, cells and tissues under normal and pathological conditions.

    Science.gov (United States)

    Beauvoit, B; Chance, B

    1998-07-01

    In this study, the detailed dependence of light scattering on tissue architecture and intracellular composition has been investigated. Firstly, we simulated the reduced scattering coefficient (mu(s)') of the rat liver using the Mie theory, the Rayleigh-Debye-Gans approximation and electron microscopy data. Then, the reduced scattering coefficient of isolated rat liver mitochondria, isolated hepatocytes and various rat tissues (i.e. perfused liver, brain, muscle, tumors) was measured at 780 nm by using time-resolved spectroscopy and a sample-substitution protocol. The comparison of the isolated mitochondria data with the isolated hepatocyte and whole liver measurements suggests that the mitochondrial compartment is the primary factor for light propagation in hepatic tissue, thus strengthening the relevance of the preliminary theoretical study. Nevertheless, the possibility that other intracellular components, such as peroxisomes and lysosomes, interfere with light propagation in rat liver is discussed. Finally, we demonstrate that light scattering in normal rat tissues and tumors is roughly proportional to the mitochondrial content, according to estimates of the mitochondrial protein content of the tissues. PMID:9746339

  6. Time resolved spectroscopy of SGR J1550-5418 bursts detected with Fermi/GBM

    CERN Document Server

    Younes, G; van der Horst, A J; Baring, M G; Granot, J; Watts, A L; Bhat, P N; Collazzi, A; Gehrels, N; Gorgone, N; Gogus, 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 time-resolved spectroscopy of the 63 brightest bursts of SGR J1550-5418, detected with Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms time-scales, to characterize the spectral evolution of the bursts. Using a Comptonized model, we find that the peak energy, E_peak, anti-correlates with flux, while the low-energy photon index remains constant at -0.8 up to a flux limit F~10^-5 erg s-1 cm-2. Above this flux value the E_peak-flux correlation changes sign, and the index positively correlates with flux reaching 1 at the highest fluxes. Using a two black-body model, we find that the areas and fluxes of the two emitting regions correlate positively. Further, we study here for the first time, the evolution of the temperatures and areas as a function of flux. We find that the area-kT relation follows lines of constant luminosity at the lowest fluxes, R^2 \\propto kT^-4, with a break at higher fluxes ($F>10^-5.5 erg s-1 cm-2). The are...

  7. Nonadiabatic Dynamics May Be Probed through Electronic Coherence in Time-Resolved Photoelectron Spectroscopy.

    Science.gov (United States)

    Bennett, Kochise; Kowalewski, Markus; Mukamel, Shaul

    2016-02-01

    We present a hierarchy of Fermi golden rules (FGRs) that incorporate strongly coupled electronic/nuclear dynamics in time-resolved photoelectron spectroscopy (TRPES) signals at different levels of theory. Expansion in the joint electronic and nuclear eigenbasis yields the numerically most challenging exact FGR (eFGR). The quasistatic Fermi Golden Rule (qsFGR) neglects nuclear motion during the photoionization process but takes into account electronic coherences as well as populations initially present in the pumped matter as well as those generated internally by coupling between electronic surfaces. The standard semiclassical Fermi Golden Rule (scFGR) neglects the electronic coherences and the nuclear kinetic energy during the ionizing pulse altogether, yielding the classical Condon approximation. The coherence contributions depend on the phase-profile of the ionizing field, allowing coherent control of TRPES signals. The photoelectron spectrum from model systems is simulated using these three levels of theory. The eFGR and the qsFGR show temporal oscillations originating from the electronic or vibrational coherences generated as the nuclear wave packet traverses a conical intersection. These oscillations, which are missed by the scFGR, directly reveal the time-evolving splitting between electronic states of the neutral molecule in the curve-crossing regime. PMID:26691822

  8. Lasing dynamics study by femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy

    Science.gov (United States)

    Wei, Dang; Qing, Liao; Peng-Cheng, Mao; Hong-Bing, Fu; Yu-Xiang, Weng

    2016-05-01

    Femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) is a versatile technique with advantages of high sensitivity, broad detection bandwidth, and intrinsic spectrum correction function. These advantages should benefit the study of coherent emission, such as measurement of lasing dynamics. In this letter, the FNOPAS was used to trace the lasing process in Rhodamine 6G (R6G) solution and organic semiconductor nano-wires. High-quality transient emission spectra and lasing dynamic traces were acquired, which demonstrates the applicability of FNOPAS in the study of lasing dynamics. Our work extends the application scope of the FNOPAS technique. Project supported by the National Natural Science Foundation of China (Grant Nos. 20925313 and 21503066), the Innovation Program of Chinese Academy of Sciences (Grant No. KJCX2-YW-W25), the Postdoctoral Project of Hebei University, China, and the Project of Science and Technology Bureau of Baoding City, China (Grant No. 15ZG029).

  9. Multiple regimes of carrier cooling in photoexcited graphene probed by time-resolved terahertz spectroscopy

    Science.gov (United States)

    Frenzel, A. J.; Gabor, N. M.; Herring, P. K.; Fang, W.; Kong, J.; Jarillo-Herrero, P.; Gedik, N.

    2013-03-01

    Energy relaxation and cooling of photoexcited charge carriers in graphene has recently attracted significant attention due to possible hot carrier effects, large quantum efficiencies, and photovoltaic applications. However, the details of these processes remain poorly understood, with many conflicting interpretations reported. Here we use time-resolved terahertz spectroscopy to explore multiple relaxation and cooling regimes in graphene in order to elucidate the fundamental physical processes which occur upon photoexcitation of charge carriers. We observe a novel negative terahertz photoconductivity that results from the unique linear dispersion and allows us to measure the electron temperature with ultrafast time resolution. Additionally, we present measurements of the relaxation dynamics over a wide range of excitation fluence. By varying the pump photon energy, we demonstrate that cooling dynamics of photoexcited carriers depend on the amount of energy deposited in the graphene system by the pump pulse, not the number of absorbed photons. The data suggest that fundamentally different regimes are encountered for different excitation fluences. These results may provide a unifying framework for reconciling various measurements of energy relaxation and cooling in graphene.

  10. 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.

  11. 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.

  12. Time-resolved tunable diode laser absorption spectroscopy of pulsed plasma.

    Science.gov (United States)

    Adámek, P; Olejníček, J; Čada, M; Kment, Š; Hubička, Z

    2013-07-15

    A method for time-resolved tunable diode laser absorption spectroscopy (LAS) has been developed. In this Letter, we describe in detail a developed electronic module that controls the time resolution of the LAS system. The transistor-transistor logic signal triggering the plasma pulse is used for generation of two signals: the first one triggers fine tuning of the laser wavelength and the second one controls time-defined signal sampling from the absorption detector. The described method and electronic system enable investigation of the temporal evolution of the density and temperature of selected particles in technological plasma systems. The high-power impulse magnetron sputtering system with a period of 10 ms and a duty cycle of 1% has been used to verify this method. The temporal evolution of argon metastable density was measured in the active part of the pulse and in the afterglow. The resulting density of Ar* displays a double-peak structure with a first peak in the plasma "ON" phase and a second peak in the afterglow approximately 1 ms after the end of the pulse.

  13. 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...

  14. Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy.

    Science.gov (United States)

    Miaja-Avila, L; O'Neil, G C; Uhlig, J; Cromer, C L; Dowell, M L; Jimenez, R; Hoover, A S; Silverman, K L; Ullom, J N

    2015-03-01

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼10(6) photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >10(7) laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.

  15. Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

    Directory of Open Access Journals (Sweden)

    L. Miaja-Avila

    2015-03-01

    Full Text Available We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.

  16. High Resolution Time-resolved UCLES Spectroscopy of AE Aqr: I. The Secondary Star Revealed

    Science.gov (United States)

    Echevarria, J.; Diego, F.; Mills, D.; Connon Smith, R.

    2006-06-01

    High-dispersion time-resolved spectroscopy of the cataclysmic variable AE Aqr has been obtained. The emission lines have a complex structure that make difficult to measure the motion of the white dwarf. The cross correlation for the absorption lines shows a clear asymmetric profile as expected from a heated side of the red star. The spectral type for the secondary star varies from K2 to K5; there are clear indications that the temperature varies as a function of star longitude. The radial velocity analysis yield Kab = 165.2 ± 0.6 Km s-1 for the cross-correlated secondary star. The rotational velocity of the red star has been measured as a function of orbital period. It shows ellipsoidal variations with a period half the orbital period. The rotational velocities vary within the range Vrot sin i = 105 ± 3 Km s-1 and Vrot sin i = 130 ± 3 Km s-1. The former can be used to constrain the white dwarf semi-amplitude value to yield Kem = 139 ± 4 Km s-1 consistent with derived values from published radial velocity measurements. From a variation in the absorption line strength of 30%, we constrain the inclination angle to i = 58° ± 3. The estimated masses of the binary are: Mw = 1.07 ± 0.07 M? and Mr = 0.90 ± 0.05 M?. If this is correct we should expect a spectral type of G5 if the secondary star is a main sequence star. We suggest that the discrepancy is explained if the star has a radius 40% greater than a main sequence star for a mass of 0.90 M?.

  17. Intraoperative delineation of primary brain tumors using time-resolved fluorescence spectroscopy

    Science.gov (United States)

    Butte, Pramod V.; Fang, Qiyin; Jo, Javier A.; Yong, William H.; Pikul, Brian K.; Black, Keith L.; Marcu, Laura

    2010-03-01

    The goal of this study is to determine the potential of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as an adjunctive tool for delineation of brain tumor from surrounding normal tissue in order to assist the neurosurgeon in near-complete tumor excision. A time-domain TR-LIFS prototype apparatus (gated photomultiplier detection, fast digitizer) was used for recording tissue autofluorescence in normal cortex (NC), normal white matter (NWM), and various grades of gliomas intraoperatively. Tissue fluorescence was induced with a pulsed nitrogen laser (337 nm, 700 ps), and the intensity decay profiles were recorded in the 360- to 550-nm spectral range (10-nm interval). Histopathological analysis (hematoxylin & eosin) of the biopsy samples taken from the site of TR-LIFS measurements was used for validation of spectroscopic results. Preliminary results on 17 patients demonstrate that normal cortex (N=16) and normal white matter (N=3) show two peaks of fluorescence emission at 390 nm (lifetime=1.8+/-0.3 ns) and 460 nm (lifetime=0.8+/-0.1 ns). The 390-nm emission peak is absent in low-grade glioma (N=5; lifetime=1.1 ns) and reduced in high-grade glioma (N=9; lifetime=1.7+/-0.4 ns). The emission characteristics at 460 nm in all tissues correlated with the nicotinamide adenine dinucleotide fluorescence (peak: 440 to 460 nm lifetime: 0.8 to 1.0 ns). These findings demonstrate the potential of using TR-LIFS as a tool for enhanced delineation of brain tumors during surgery. In addition, this study evaluates similarities and differences between TR-LIFS signatures of brain tumors obtained in vivo and those previously reported in ex vivo brain tumor specimens.

  18. Effects of maturity on chlorophyll-related absorption in nectarines, measured by non-destructive time-resolved reflectance spectroscopy

    NARCIS (Netherlands)

    Tijskens, L.M.M.; Eccher Zerbini, P.C.; Vanoli, M.; Jacob, S.; Grassi, M.; Cebeddu, R.; Spinelli, L.; Torricelli, A.

    2006-01-01

    The ripening of fruits like nectarines and peaches is characterised by the decrease in chlorophyll content or colour of the fruit flesh. However, measuring the colour of fruit flesh is usually not conducted, as there is a lack of suitable techniques. Time-Resolved Reflectance Spectroscopy (TRS) is a

  19. 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

  20. Time resolved ESR spectroscopy. ESR pulse radiolysis equipment with microsecond time resolution

    Energy Technology Data Exchange (ETDEWEB)

    Beckert, D.; Mehler, K. (Akademie der Wissenschaften der DDR, Leipzig. Zentralinstitut fuer Isotopen- und Strahlenforschung)

    1983-01-01

    Time resolved ESR experiments allow the study of the chemical kinetics as well as spin dynamics of free radicals in the liquid phase. Starting from the physical and chemical requirements the experimental parameters of a universal time resolved ESR spectrometer are derived. The main components of the ESR pulse radiolysis equipment are described and their technical parameters are discussed. By two experimental examples it is shown that at a time resolution of 0.3 ..mu..s a sensitivity of c/sub min/ = 10/sup -6/ mol dm/sup -3/ for simple radical spectra can be achieved.

  1. Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

    Energy Technology Data Exchange (ETDEWEB)

    Niedzwiedzki, Dariusz; Fuciman, Marcel; Kobayashi, Masayuki; Frank, Harry A; Blankenship, R. E.

    2011-10-08

    The light-harvesting complex 2 from the thermophilic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption and fluorescence, sub-nanosecond-time-resolved fluorescence and femtosecond time-resolved transient absorption spectroscopy. The measurements were performed at room temperature and at 10 K. The combination of both ultrafast and steady-state optical spectroscopy methods at ambient and cryogenic temperatures allowed the detailed study of carotenoid (Car)-to-bacteriochlorophyll (BChl) as well BChl-to-BChl excitation energy transfer in the complex. The studies show that the dominant Cars rhodopin (N = 11) and spirilloxanthin (N = 13) do not play a significant role as supportive energy donors for BChl a. This is related with their photophysical properties regulated by long π-electron conjugation. On the other hand, such properties favor some of the Cars, particularly spirilloxanthin (N = 13) to play the role of the direct quencher of the excited singlet state of BChl.

  2. Molecular orbital imaging of the acetone S2 excited state using time-resolved (e, 2e) electron momentum spectroscopy.

    Science.gov (United States)

    Yamazaki, Masakazu; Oishi, Keiya; Nakazawa, Hiroyuki; Zhu, Chaoyuan; Takahashi, Masahiko

    2015-03-13

    We report a time-resolved (e, 2e) experiment on the deuterated acetone molecule in the S2 Rydberg state with a lifetime of 13.5 ps. The acetone S2 state was prepared by a 195 nm pump laser and probed with electron momentum spectroscopy using a 1.2 keV incident electron beam of 1 ps temporal width. In spite of the low data statistics as well as of the limited time resolution (±35  ps) due to velocity mismatch, the experimental results clearly demonstrate that electron momentum spectroscopy measurements of short-lived transient species are feasible, opening the door to time-resolved orbital imaging in momentum space.

  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. High-pressure-low-temperature cryostat designed for use with fourier transform infrared spectrometers and time-resolved infrared spectroscopy.

    Science.gov (United States)

    Calladine, James A; Love, Ashley; Fields, Peter A; Wilson, Richard G M; George, Michael W

    2014-01-01

    The design for a new high-pressure-low-temperature infrared (IR) cell for performing experiments using conventional Fourier transform infrared or fast laser-based time-resolved infrared spectroscopy, in a range of solvents, is described. The design builds upon a commercially available compressor and cold end (Polycold PCC(®) and CryoTiger(®)), which enables almost vibration-free operation, ideal for use with sensitive instrumentation. The design of our cell and cryostat allows for the study of systems at temperatures from 77 to 310 K and at pressures up to 250 bar. The CaF2 windows pass light from the mid-IR to the ultraviolet (UV), enabling a number of experiments to be performed, such as Raman, UV-visible absorption spectroscopy, and time-resolved techniques where sample excitation/probing using continuous wave or pulsed lasers is required. We demonstrate the capabilities of this cell by detailing two different applications: (i) the reactivity of a range of Group V-VII organometallic alkane complexes using time-resolved spectroscopy on the millisecond timescale and (ii) the gas-to-liquid phase transition of CO2 at low temperature, which is applicable to measurements associated with transportation issues related to carbon capture and storage.

  6. Characterization of hydroxyapatite by time-resolved luminescence and FTIR spectroscopy

    International Nuclear Information System (INIS)

    Time-resolved luminescence and FTIR absorption spectra of undoped and Eu and Ce doped hydroxyapatite nanocrystalline powders prepared by sol-gel method were studied. The luminescence band at 350–400 nm was detected and two decay times (11 ns and 38 ns) was determinated for Ce doped samples. The luminescence spectra and decay kinetics were analized for Eu doped nanopowders. The Eu3+ ion was incorporated in different Ca sites. The process of energy transfer to Eu3+ excited state (5D0) was detected from luminescence decay kinetics

  7. Time-Resolved Terahertz Spectroscopy with Free-Space Electro-Optic Sampling

    Institute of Scientific and Technical Information of China (English)

    ZHANG Liang-Liang; ZHAO Guo-Zhong; ZHONG Hua; HU Ying; ZHANG Cun-Lin

    2004-01-01

    @@ We present a time-resolved ultrafast measurement in terahertz (THz) frequency region by means of the free-space electro-optic sampling. The fast delay scan technique is used to suppress the noise with low frequency and to improve the signal-to-noise ratio of the system. The transmission spectra of different materials are obtained.The optical properties of these materials in a THz region are shown. The broadening of spectrum and chirping phenomena are illustrated. We find that polystyrene is an excellent material for the THz application.

  8. Time-resolved nonlinear polarization spectroscopy for measuring transient absorption and refraction in isotropic materials

    Science.gov (United States)

    Taranenko, Victor B.; Bazhenov, Vladimir Y.; Kulikovskaya, Olga A.

    1995-11-01

    A novel time-resolved nonlinear spectroscopic technique is described, which is based on stroboscopic registration of optical polarization transformation taking place at a vector incoherent two-wave mixing interaction in a modified Mach-Zehnder interferometer. It allows an accurate measuring of the dynamics of excitation and relaxation for real and imaginary parts of complex nonlinearity tensor components. The technique is demonstrated for measuring the light-induced change of transient absorption (delta) (alpha) e(t), (delta) (alpha) o(t) and refraction (delta) ne(t), (delta) no(t) for bacteriorhodopsin- based film pumped by linearly polarized laser pulses.

  9. Ultrafast dynamics of o-fluorophenol studied with femtosecond time-resolved photoelectron and photoion spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The ultrafast dynamics of o-fluorophenol via the excited states has been studied by femtosecond time-resolved photoelectron imaging. The photoion and photoelectron spectra taken with a time delay between 267 nm pump laser and 800 nm probe laser provide a longer-lived S1 electronic state of about ns timescale. In comparison,the spectra obtained by exciting the S2 state with femtosecond laser pulses at 400 nm and ionizing with pulses at 800 nm suggest that the S2 state has an ultrashort lifetime about 102 fs and reflects the internal conversion dynamics of the S2 state to the S1 state.

  10. High-sensitivity time-resolved intracavity laser Fourier transform spectroscopy with vertical cavity surface emitting multiple quantum well lasers

    CERN Document Server

    Picqué, N; Kachanov, A A; Picqu\\'e, Nathalie; Guelachvili, Guy; Kachanov, Alexander A.

    2003-01-01

    Spectra comprised of hundreds of time-components for absorption path lengths up to 130 km have been recorded around 1050 nm by combining two recent techniques, intracavity laser spectroscopy with vertical external cavity surface emitting multiple-quantum-well lasers and time-resolved Fourier transform spectroscopy. A sensitivity of 1 10^{-10} cm^{-1}.Hz^{-1/2} is achieved, for simultaneously acquired 10^4 spectral elements, three orders of magnitude better than the sensitivity obtained in previous similar experiments. Specific advantages of the method, especially for frequency and intensity metrology of weak absorption transitions, are discussed.

  11. [Discrimination of Crude Oil Samples Using Laser-Induced Time-Resolved Fluorescence Spectroscopy].

    Science.gov (United States)

    Han, Xiao-shuang; Liu, De-qing; Luan, Xiao-ning; Guo, Jin-jia; Liu, Yong-xin; Zheng, Rong-er

    2016-02-01

    The Laser-induced fluorescence spectra combined with pattern recognition method has been widely applied in discrimination of different spilled oil, such as diesel, gasoline, and crude oil. However, traditional three-dimension fluorescence analysis method, which is not adapted to requirement of field detection, is limited to laboratory investigatio ns. The development of oil identification method for field detection is significant to quick response and operation of oil spill. In this paper, a new method based on laser-induced time-resolved fluorescence combined with support vector machine (SVM) model was introduced to discriminate crude oil samples. In this method, time-resolved spectra data was descended into two dimensions with selecting appropriate range in time and wavelength domains respectively to form a SVM data base. It is found that the classification accurate rate increased with an appropriate selection. With a selected range from 54 to 74 ns in time domain, the classification accurate rate has been increased from 83.3% (without selection) to 88.1%. With a selected wavelength range of 387.00~608.87 nm, the classification accurate rate of suspect oil was improved from 84% (without selection) to 100%. Since the detection delay of fluorescence lidar fluctuates due to wave and platform swing, the identification method with optimizing in both time and wavelength domains could offer a better flexibility for field applications. It is hoped that the developed method could provide some useful reference with data reduction for classification of suspect crude oil in the future development.

  12. Radiative lifetime measurements for some levels in Mn I and Ni I by time-resolved laser spectroscopy

    International Nuclear Information System (INIS)

    Natural radiative lifetimes for 32 excited levels of Mn I and for 17 excited levels of Ni I were measured using time-resolved laser-induced fluorescence (TR-LIF) spectroscopy in laser-induced plasma. The energy regions are from 45,754.27 to 54,950.81 cm−1 for Mn I and from 28,578.018 to 50,851.199 cm−1 for Ni I. The uncertainties of all lifetime results are within 10%. To our best knowledge, 26 lifetime results of Mn I and 9 lifetime results of Ni I are reported for the first time. - Highlights: • The experimental lifetimes of some Mn I and Ni I levels were obtained by time-resolved laser induced fluorescence method. • Radiative lifetimes of 26 energy levels in Mn I were reported for the first time. • Radiative lifetimes of 9 energy levels in Ni I were reported for the first time

  13. Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy.

    Science.gov (United States)

    Dorchies, F; Fedorov, N; Lecherbourg, L

    2015-07-01

    We present an experimental station designed for time-resolved X-ray Absorption Near-Edge Spectroscopy (XANES). It is based on ultrashort laser-plasma x-ray pulses generated from a table-top 100 mJ-class laser at 10 Hz repetition rate. A high transmission (10%-20%) x-ray beam line transport using polycapillary optics allows us to set the sample in an independent vacuum chamber, providing high flexibility over a wide spectral range from 0.5 up to 4 keV. Some XANES spectra are presented, demonstrating 1% noise level in only ∼1 mn and ∼100 cumulated laser shots. Time-resolved measurements are reported, indicating that the time resolution of the entire experimental station is 3.3 ± 0.6 ps rms.

  14. Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dorchies, F., E-mail: dorchies@celia.u-bordeaux1.fr; Fedorov, N.; Lecherbourg, L. [Université Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et Applications), UMR 5107, Talence F-33405 (France)

    2015-07-15

    We present an experimental station designed for time-resolved X-ray Absorption Near-Edge Spectroscopy (XANES). It is based on ultrashort laser-plasma x-ray pulses generated from a table-top 100 mJ-class laser at 10 Hz repetition rate. A high transmission (10%–20%) x-ray beam line transport using polycapillary optics allows us to set the sample in an independent vacuum chamber, providing high flexibility over a wide spectral range from 0.5 up to 4 keV. Some XANES spectra are presented, demonstrating 1% noise level in only ∼1 mn and ∼100 cumulated laser shots. Time-resolved measurements are reported, indicating that the time resolution of the entire experimental station is 3.3 ± 0.6 ps rms.

  15. Time resolved optical biopsy spectroscopy of normal, benign and malignant tissues from NADH and FAD changes

    Science.gov (United States)

    Masilamani, V.; Das, B. B.; Secor, J.; AlSalhi, M.; Amer, S. B.; Farhat, K.; Rabah, D.; Alfano, R. R.

    2012-01-01

    Histo pathological examination is the gold standard to discriminate between benign and malignant growth of tissue. But this is invasive and stressful. Hence many non invasive imaging techniques, such as CT, MRI, PET, etc are employed, each having certain advantages and disadvantages. In this context optical biopsy is a newly emerging technique, since it employs non-ionizing radiation like light or laser, which could be shined directly or launched through optical fiber to reach any part of the body. This paper reports results of time resolved emission spectra of 24 excised tissue sample (normal control=12; benign=4; malignant=8) of breast and prostate, employing a 390nm, 100 fs, Ti-Sapphire laser pulses. The fluorescence decay times were measured using streak camera and fitted for single and bi- exponential decays with reliability of 97%. Our results show the distinct difference between normal, benign and malignant tissues attributed changes of NADH and FAD levels.

  16. Determination of Iron in Water Solution by Time-Resolved Femtosecond Laser-Induced Breakdown Spectroscopy

    Science.gov (United States)

    Sergey, S. Golik; Alexey, A. Ilyin; Michael, Yu. Babiy; Yulia, S. Biryukova; Vladimir, V. Lisitsa; Oleg, A. Bukin

    2015-11-01

    The influence of the energy of femtosecond laser pulses on the intensity of Fe I (371.99 nm) emission line and the continuous spectrum of the plasma generated on the surface of Fe3+ water solution by a Ti: sapphire laser radiation with pulse duration laser pulse energy. It is found that an increase of laser pulse energy insignificantly affects on LOD in the time-resolved LIBS and leads to a slight improvement of the limit of detection. supported by the Russian Science Foundation (agreement #14-50-00034) (measurements of limit of detection), Russian Foundation for Basic Research (NK 15-32-20878/15) obtained in the frame of “Organization of Scientific Research” in the Far Eastern Federal University supported by Ministry of Education and Science of Russian Federation

  17. Analysis of hydrocarbon-bearing fluid inclusions (HCFI) using time-resolved fluorescence spectroscopy

    Science.gov (United States)

    Przyjalgowski, Milosz A.; Ryder, Alan G.; Feely, Martin; Glynn, Thomas J.

    2005-06-01

    Hydrocarbon-bearing fluid inclusions (HCFI) are microscopic cavities within rocks that are filled with petroleum oil, the composition of which may not have changed since the trapping event. Thus, the composition of that entrapped oil can provide information about the formation and evolution of the oil reservoir. This type of information is important to the petroleum production and exploration industries. Crude oil fluorescence originates from the presence of cyclic aromatic compounds and the nature of the emission is governed by the chemical composition of the oil. Fluorescence based methods are widely used for analysis of crude oil because they offer robust, non-contact and non-destructive measurement options. The goal of our group is the development of a non-destructive analytical method for HCFI using time-resolved fluorescence methods. In broad terms, crude oil fluorescence behavior is governed by the concentration of quenching species and the distribution of fluorophores. For the intensity averaged fluorescence lifetime, the best correlations have been found between polar or alkane concentrations, but these are not suitable for robust, quantitative analysis. We have recently started to investigate another approach for characterizing oils by looking at Time-resolved Emission Spectra (TRES). TRES are constructed from intensities sampled at discrete times during the fluorescence decay of the sample. In this study, TRES, from a series of 10 crude oils from the Middle East, have been measured at discrete time gates (0.5 ns, 1 ns, 2 ns, 4 ns) over the 450-700 nm wavelength range. The spectral changes in TRES, such as time gate dependent Stokes' shift and spectral broadening, are analyzed in the context of energy transfer rates. In this work, the efficacy of using TRES for fingerprinting individual oils and HCFI is also demonstrated.

  18. Cerebral and Muscle Tissue Oxygenation During Incremental Cycling in Male Adolescents Measured by Time-Resolved Near-Infrared Spectroscopy.

    Science.gov (United States)

    Ganesan, Goutham; Leu, Szu-Yun; Cerussi, Albert; Tromberg, Bruce; Cooper, Dan M; Galassetti, Pietro

    2016-05-01

    Near-infrared spectroscopy has long been used to measure tissue-specific O2 dynamics in exercise, but most published data have used continuous wave devices incapable of quantifying absolute Hemoglobin (Hb) concentrations. We used time-resolved near-infrared spectroscopy to study exercising muscle (Vastus Lateralis, VL) and prefrontal cortex (PFC) Hb oxygenation in 11 young males (15.3 ± 2.1 yrs) performing incremental cycling until exhaustion (peak VO2 = 42.7 ± 6.1 ml/min/kg, mean peak power = 181 ± 38 W). Time-resolved near-infrared spectroscopy measurements of reduced scattering (μs´) and absorption (μa) at three wavelengths (759, 796, and 833 nm) were used to calculate concentrations of oxyHb ([HbO2]), deoxy Hb ([HbR]), total Hb ([THb]), and O2 saturation (stO2). In PFC, significant increases were observed in both [HbO2] and [HbR] during intense exercise. PFC stO2% remained stable until 80% of total exercise time, then dropped (-2.95%, p = .0064). In VL, stO2% decreased until peak time (-6.8%, p = .01). Segmented linear regression identified thresholds for PFC [HbO2], [HbR], VL [THb]. There was a strong correlation between timing of second ventilatory threshold and decline in PFC [HbO2] (r = .84). These findings show that time-resolved near-infrared spectroscopy can be used to study physiological threshold phenomena in children during maximal exercise, providing insight into tissue specific hemodynamics and metabolism. PMID:26451845

  19. Optimization of Supercontinuum Sources for Ultra-Broadband T-CARS Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    LIU Xing; LIU Wei; YIN Jun; QU Jun-Le; LIN Zi-Yang; NIU Han-Ben

    2011-01-01

    For a typical photonic crystal fiber with two zero-dispersion wavelengths, we theoretically demonstrate a new way to generate supercontinuum using an input pulse of 30fs duration and lOkW peak power for providing a compact and cost effective light source to the ultra-broadband time-resolved coherent anti-Stokes Raman scattering spectroscopy.

  20. Time-resolved fluorescence spectroscopy of matrix-isolated silver atoms after pulsed excitation of inner-shell transitions

    Science.gov (United States)

    Hebert, T.; Wiggenhauser, H.; Schriever, U.; Kolb, D. M.

    1990-02-01

    The energy dissipation in matrix-isolated silver atoms after pulsed vacuum ultraviolet (VUV) excitation of 4d-5p transitions has been studied by time-resolved fluorescence spectroscopy. The decay behavior of the various fluorescence bands has been analyzed and a model for the relaxation process proposed within the framework of a two-dimensional configuration-coordinate diagram. If minute quantities of Ag2 are present in the matrix, the analysis requires consideration of energy transfer between silver atoms and dimers.

  1. Time-resolved two-photon excitation fluorescence spectroscopy and microscopy using a high repetition rate streak camera

    Institute of Scientific and Technical Information of China (English)

    LIU Li-xin; QU Ju-le; LIN Zi-yang; WANG Lei; FU Zhe; GUO Bao-ping; NIU Han-ben

    2007-01-01

    We present a time-resolved two-photon excitation fluorescence spectroscopy and a simultaneous time- and spectrumresolved multifocal multiphoton microscopy system that is based on a high repetition rate picosecond streak camera for providing time- and spectrum- resolved measurement and imaging in biomedicine. The performance of the system is tested and characterized by the fluorescence spectrum and lifetime analysis of several standard fluorescent dyes and their mixtures.Spectrum-resolved fluorescence lifetime images of fluorescence beads are obtained. Potential applications of the system include clinical diagnostics and cell biology etc.

  2. Probing Reaction Dynamics of Transition-Metal Complexes in Solution via Time-Resolved X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huse, Nils; Khalil, Munira; Kim, Tae Kyu; Smeigh, Amanda L.; Jamula, Lindsey; McCusker, James K.; Schoenlein, Robert W.

    2009-05-24

    We report measurements of the photo-induced Fe(II) spin crossover reaction dynamics in solution via time-resolved x-ray absorption spectroscopy. EXAFS measurements reveal that the iron?nitrogen bond lengthens by 0.21+-0.03 Angstrom in the high-spin transient excited state relative to the ground state. XANES measurements at the Fe L-edge show directly the influence of the structural change on the ligand-field splitting of the Fe(II) 3d orbitals associated with the spin transition.

  3. Probing reaction dynamics of transition-metal complexes in solution via time-resolved X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huse, Nils [Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1Cyclotron Road, Berkeley, CA 94720 (United States); Khalil, Munira [Department of Chemistry, University of Washington, Seattle, WA 98195 (United States); Kim, Tae Kyu [Department of Chemistry, Pusan National University, Busan 609-735 (Korea, Republic of); Smeigh, Amanda L; Jamula, Lindsey; McCusker, James K [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Schoenlein, Robert W, E-mail: nhuse@lbl.go, E-mail: rwschoenlein@lbl.go [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States)

    2009-02-01

    We report measurements of the photoinduced Fe{sup II} spin crossover reaction dynamics in solution via time-resolved x-ray absorption spectroscopy. EXAFS measurements reveal that the iron-nitrogen bond lengthens by 0.21+-0.03 A in the high-spin transient excited state relative to the ground state. XANES measurements at the Fe L-edge show directly the influence of the structural change on the ligand-field splitting of the Fe{sup II} 3d orbitals associated with the spin transition.

  4. 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......, as is the solvent heating due to the initial energy dissipation from the excited HS molecule. Combining information from X-ray emission spectroscopy and scattering, the excitation fraction as well as the temperature and density changes of the solvent can be closely followed on the subnanosecond time scale of the HS...

  5. Diffusion optical spectroscopy of cancerous and normal prostate tissues in time-resolved and frequency domain

    Science.gov (United States)

    Zhou, Kenneth J.; Pu, Yang; Chen, Jun

    2014-03-01

    It is well-known that light transport can be well described using Maxwell's electromagnetic theory. In biological tissue, the scattering particles cause the interaction of scattered waves from neighboring particles. Since such interaction cannot be ignored, multiple scattering occurs. The theoretical solution of multiple scattering is complicated. A suitable description is that the wavelike behavior of light is ignored and the transport of an individual photon is considered to be absorbed or scattered. This is known as the Radiative Transfer Equation (RTE) theory. Analytical solutions to the RTE that explicitly describes photon migration can be obtained by introducing some proper approximations. One of the most popular models used in the field of tissue optics is the Diffusion Approximation (DA). In this study, we report on the results of our initial study of optical properties of ex vivo normal and cancerous prostate tissues and how tissue parameters affect the near infrared light transporting in the two types of tissues. The time-resolved transport of light is simulated as an impulse isotropic point source of energy within a homogeneous unbounded medium with different absorption and scattering properties of cancerous and normal prostate tissues. Light source is also modulated sinusoidally to yield a varied fluence rate in frequency domain at a distant observation point within the cancerous and normal prostate tissues. Due to difference of the absorption and scattering coefficients between cancerous and normal tissues, the expansion of light pulse, intensity, phase are found to be different.

  6. Non-adiabatic and time-resolved photoelectron spectroscopy for molecular systems

    CERN Document Server

    Flick, Johannes; Rubio, Angel

    2014-01-01

    We quantify the non-adiabatic contributions to the vibronic sidebands of equilibrium and explicitly time-resolved non-equilibrium photoelectron spectra for a vibronic model system of Trans-Polyacetylene. Using exact diagonalization, we directly evaluate the sum-over-states expressions for the linear-response photocurrent. We show that spurious peaks appear in the Born-Oppenheimer approximation for the vibronic spectral function, which are not present in the exact spectral function of the system. The effect can be traced back to the factorized nature of the Born-Oppenheimer initial and final photoemission states and also persists when either only initial, or final states are replaced by correlated vibronic states. Only when correlated initial and final vibronic states are taken into account, the spurious spectral weights of the Born-Oppenheimer approximation are suppressed. In the non-equilibrium case, we illustrate for an initial Franck-Condon excitation and an explicit pump-pulse excitation how the vibronic ...

  7. Time-resolved fluorescence spectroscopy for intraoperative assistance of thyroid surgery

    Science.gov (United States)

    Bachmann, L.; Brandao, M. P.; Iwakura, R.; Basilio, F. S.; Haleplian, K.; Ito, A. S.; Conti de Freitas, L. C.

    2016-03-01

    Searching for new methods to provide information of biochemical composition and structure is critical to improve the prognosis of thyroid diseases. The use of time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help develop a portable, minimally invasive, and non-destructive method to assist during surgical procedures. This research looks for employ a fluorescence technique based on lifetime measurements to differentiate healthy and benign lesions from malignant thyroid tissue. We employ a wide range of excitation and chose a more appropriate region for this work: 298-300 nm; and the fluorescence decay was measured at 340-450 nm. We observed fluorescence lifetimes at 340 nm emission of 0.80+/-0.26 and 3.94+/-0.47 ns for healthy tissue; 0.90+/-0.24 and 4.05+/-0.46 ns for benign lesions; and 1.21+/-0.14 and 4.63+/-0.25 ns for malignant lesions. For 450 nm emissions, we obtain lifetimes of 0.25+/-0.18 and 3.99+/-0.39 ns for healthy tissue, 0.24+/-0.17 and 4.20+/-0.48 ns for benign lesions, 0.33+/-0.32 and 4.55+/-0.55 ns for malignant lesions. We successfully demonstrated that fluorescence lifetimes at 340 nm emission can differentiate between thyroid malignant and healthy/benign tissues.

  8. TIME-RESOLVED SPECTROSCOPY OF THE POLAR EU CANCRI IN THE OPEN CLUSTER MESSIER 67

    International Nuclear Information System (INIS)

    We present time-resolved spectroscopic and polarimetric observations of the AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster Messier 67; new proper motion measurements indicate that EU Cnc is indeed a member of the star cluster, and this system therefore is useful to constrain the formation and evolution of magnetic cataclysmic variables. The spectra exhibit two-component emission features with independent radial velocity variations as well as time-variable cyclotron emission indicating a magnetic field strength of 41 MG. The period of the radial velocity and cyclotron hump variations are consistent with the previously known photometric period, and the spectroscopic flux variations are consistent in amplitude with previous photometric amplitude measurements. The secondary star is also detected in the spectrum. We also present polarimetric imaging measurements of EU Cnc that show a clear detection of polarization, and the degree of polarization drops below our detection threshold at phases when the cyclotron emission features are fading or not evident. The combined data are all consistent with the interpretation that EU Cnc is a low-state polar in the cluster Messier 67. The mass function of the system gives an estimate of the accretor mass of MWD ≥ 0.68 M☉ with MWD ≈ 0.83 M☉ for an average inclination. We are thus able to place a lower limit on the progenitor mass of the accreting white dwarf of ≥1.43 M☉.

  9. Multiplexed measurements by time resolved spectroscopy using colloidal CdSe/ZnS quantum dots

    International Nuclear Information System (INIS)

    Multiplexed measurements of analytes in parallel is a topical demand in bioanalysis and bioimaging. An interesting alternative to commonly performed spectral multiplexing is lifetime multiplexing. In this Letter, we present a proof of principle of single-color lifetime multiplexing by coupling the same fluorophore to different nanoparticles. The effective lifetime of the fluorophores can be tuned by more than one order of magnitude due to resonance energy transfer from donor states. Measurements have been done on a model systems consisting of ATTO-590 dye molecules linked to either gold particles or to CdSe/ZnS core shell quantum dots. Both systems show the same luminescence spectrum of ATTO-590 dye emission in continuous wave excitation, but can be distinguished by means of time resolved measurements. The dye molecules bound to gold particles exhibit a mono-exponential decay with a lifetime of 4.5 ns, whereas the dye molecules bound to CdSe/ZnS dots show a nonexponential decay with a slow component of about 135 ns due to the energy transfer from the quantum dots. We demonstrate the fundamental possibility to determine the mixing ratio for dyes with equal luminescence spectra but very different transients. This opens up a pathway independent of the standard optical multiplexing with many different fluorophores emitting from the near ultraviolet to the near infrared spectral region

  10. Spectroscopy and optically stimulated luminescence of Al2O3:C using time-resolved measurements

    Science.gov (United States)

    Yukihara, E. G.; McKeever, S. W. S.

    2006-10-01

    This paper reports the observation of ultraviolet (UV) emission at 335nm in the optically stimulated luminescence (OSL) of carbon-doped aluminum oxide (Al2O3:C) and presents results on the investigation of the OSL properties of this band, including its dose response, time dependence after irradiation, and dependence of the OSL signal on the type of radiation. Time-resolved OSL measurements were used to separate the UV emission band from the dominant OSL emission band of Al2O3:C, namely, the F-center luminescence at 420nm. A comparison of the OSL properties of the UV and F-center emission bands is important for various dosimetric applications because the relative contribution of the UV and F-center emissions to the OSL signal varies with readout technique and optical filters used in the readout equipment. The UV emission band is found to show an ionization density dependence that is different from the dependence observed for the F-center emission, and an increase in intensity with time elapsed after beta irradiation. These results are relevant for OSL dosimetry of radiation fields containing heavy charged particles, such as the space radiation field and the secondary fields created by interactions of matter with energetic neutrons, as well as for understanding of the basic OSL mechanism in Al2O3:C.

  11. Theory of spin dynamics of magnetic adatoms traced by time-resolved scanning tunneling spectroscopy

    CERN Document Server

    Schüler, Michael; Berakdar, Jamal

    2012-01-01

    The inelastic scanning tunneling microscopy (STM) has been shown recently (Loth et al. Science 329, 1628 (2010)) to be extendable as to access the nanosecond, spin-resolved dynamics of magnetic adatoms and molecules. Here we analyze theoretically this novel tool by considering the time-resolved spin dynamics of a single adsorbed Fe atom excited by a tunneling current pulse from a spin-polarized STM tip. The adatom spin-configuration can be controlled and probed by applying voltage pulses between the substrate and the spin-polarized STM tip. We demonstrate how, in a pump-probe manner, the relaxation dynamics of the sample spin is manifested in the spin-dependent tunneling current. Our model calculations are based on the scattering theory in a wave-packet formulation. The scheme is nonpertubative and hence, is valid for all voltages. The numerical results for the tunneling probability and the conductance are contrasted with the prediction of simple analytical models and compared with experiments.

  12. Far-field infrared super-resolution microscopy using picosecond time-resolved transient fluorescence detected IR spectroscopy

    Science.gov (United States)

    Sakai, Makoto; Kawashima, Yasutake; Takeda, Akihiro; Ohmori, Tsutomu; Fujii, Masaaki

    2007-05-01

    A new far-field infrared super-resolution microscopy combining laser fluorescence microscope and picosecond time-resolved transient fluorescence detected IR (TFD-IR) spectroscopy is proposed. TFD-IR spectroscopy is a kind of IR-visible/UV double resonance spectroscopy, and detects IR transitions by the transient fluorescence due to electronic transition originating from vibrationally excited level populated by IR light. IR images of rhodamine-6G solution and of fluorescent beads were clearly observed by monitoring the transient fluorescence. Super-resolution twice higher than the diffraction limit for IR light was achieved. The IR spectrum due to the transient fluorescence was also measured from spatial domains smaller than the diffraction limit.

  13. 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...

  14. Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

    OpenAIRE

    Miaja-Avila, L.; G. C. O'Neil; Uhlig, J.; C. L. Cromer; Dowell, M. L.; Jimenez, R.; Hoover, A. S.; Silverman, K. L.; Ullom, J. N.

    2015-01-01

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼106 photons/s, by focusing the produced x-rays with a polycapillary opti...

  15. Time resolved super continuum Cavity Ring-Down Spectroscopy for multicomponent gas detection

    International Nuclear Information System (INIS)

    In this work, we present a variation of the technique CRDS (Cavity Ring-Down Spectroscopy) to obtain simultaneously a multicomponent absorption spectrum in a broad visible range. This new approach uses the Supercontinuum (SC) spectrum (resulting from irradiation of nonlinear media by femtosecond lasers, or simply generated by compact sources) as a light source to illuminate the cavity. In this context it is described the features of the modules assembling a MC-SC-CRDS (Multicomponent Supercontinuum Cavity Ring-Down Spectroscopy): a set of high reflectivity mirrors, the resonant cavity and the detection system. Some problems related to the multimode excitation, stray light, effective use of the dynamic range of the detector, the poor resolution of the instrument to resolve narrow absorption lines are issued. We present the absorption spectra of H2O (polyads 4υ, 4υ + δ) and O2 (spin-forbidden b-X branch) measured simultaneously by this technique in the visible range and a comparison with the absorption lines based on HITRAN database is made to demonstrate the functionality of this method. (author)

  16. Retrieval procedure for time-resolved near-infrared tissue spectroscopy based on the optimal estimation method

    International Nuclear Information System (INIS)

    We propose the use of a retrieval procedure for time-resolved near-infrared tissue spectroscopy based on the ‘optimal estimation’ method. The aim of this retrieval method is to obtain an improved estimate of the target parameters compared with standard nonlinear least-squares routines, since the inverse problem dedicated to retrieve the optical properties of tissue is ill posed. A priori information on target and forward model parameters is used, so that a larger number of target parameters can be retrieved, and/or a better accuracy and precision can be achieved on the retrieved target parameters. The procedure has been tested on time-resolved simulated experiments generated, using solutions of the diffusion equation and with solutions of the radiative transfer equation reconstructed with Monte Carlo simulations. The results obtained show that, by using a priori information on target parameters, we have a smaller difference between retrieved values and true values, and lower retrieved error bars. Similarly, a more correct estimate of the errors of the forward model parameters improves the retrieval of the target parameters. (paper)

  17. Time-resolved Spectroscopy of Active Binary Stars: Coronal Structure and Flares (Part II)

    Science.gov (United States)

    Brown, Alexander

    EUVE has provided the first stellar coronal spectra showing individual emission lines, thereby allowing coronal modelling at a level of sophistication previously unattainable. Long EUVE observations have shown that large-scale flaring is prevalent in the coronae of active binary stars. We propose to obtain EUVE DSS spectra and photometry for 4 active binaries, one of which has never been observed by EUVE (V478 Lyr) and three EUV-bright systems that merit reobservation (Sigma CrB, Sigma Gem, Xi UMa). We shall use these observations to derive high quality quiescent coronal spectra for measuring emission measure distributions and modelling, and to obtain new flare data. We shall try to coordinate these observations with ground-based radio observations and other spacecraft, if the scheduling allows. The Sigma CrB spectra may be coordinated with AXAF GTO observations. The proposed observations will significantly increase the available EUVE spectroscopy of active binaries.

  18. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy

    Science.gov (United States)

    Ramasesha, Krupa; Leone, Stephen R.; Neumark, Daniel M.

    2016-05-01

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions.

  19. Natural Lifetimes of Excited-states of Neutral Nitrogen Determined By Time-resolved Laser Spectroscopy

    OpenAIRE

    Bengtsson, G. J; Larsson, Jörgen; Svanberg, Sune; Wang, D. D

    1992-01-01

    Radiative lifetimes were determined for three quartet states of neutral nitrogen, and sequences of Rydberg states were studied using depletion spectroscopy. Free nitrogen atoms were generated by photodissociation of N2O using frequency-tripled dye-laser radiation that was two-photon resonant with the 2p(2)3p 4S or 4D states. Further quartet states were reached by a subsequent single-photon absorption. We obtain tau(2p(2)3p 4D7/2) = 44(2) ns, tau(2p(2)3p 4S3/2) = 26.0(1.5) ns, and tau(2p(2)6s4...

  20. Picosecond time-resolved X-ray absorption spectroscopy of ultrafast aluminum plasmas.

    Science.gov (United States)

    Audebert, P; Renaudin, P; Bastiani-Ceccotti, S; Geindre, J-P; Chenais-Popovics, C; Tzortzakis, S; Nagels-Silvert, V; Shepherd, R; Matsushima, I; Gary, S; Girard, F; Peyrusse, O; Gauthier, J-C

    2005-01-21

    We have used point-projection K-shell absorption spectroscopy to infer the ionization and recombination dynamics of transient aluminum plasmas. Two femtosecond beams of the 100 TW laser at the LULI facility were used to produce an aluminum plasma on a thin aluminum foil (83 or 50 nm), and a picosecond x-ray backlighter source. The short-pulse backlighter probed the aluminum plasma at different times by adjusting the delay between the two femtosecond driving beams. Absorption x-ray spectra at early times are characteristic of a dense and rather homogeneous plasma. Collisional-radiative atomic physics coupled with hydrodynamic simulations reproduce fairly well the measured average ionization as a function of time. PMID:15698184

  1. Synthesis of Ag clusters in microemulsions: A time-resolved UV vis and fluorescence spectroscopy study

    Science.gov (United States)

    Ledo, Ana; Martínez, F.; López-Quintela, M. A.; Rivas, J.

    2007-09-01

    The combined use of the microemulsion technique and the kinetic control allows the preparation of small silver clusters. By using UV-vis and fluorescence spectroscopy the main stages by which the clusters grow, before the formation of nanoparticles, were elucidated. Transmission electron microscopy (TEM) and scanning tunnelling microscopy (STM) were used to further characterize the samples. Two main stages were clearly identified, which are associated with: (1) the formation of Ag n clusters with n<10, which self-aggregate into one atom high 2D nanodiscs of 3.2 nm size and (2) Ag n clusters, which self-aggregate into 3D nanostructures of 1.5 nm in size. The fluorescence properties observed with both stages show that the formed clusters are small enough to display a molecule-like behaviour.

  2. 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.

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

    International Nuclear Information System (INIS)

    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, [FeII(bpy)3]2+, in aqueous solution, resolving the Fe-N bond distance elongation as 0.2 A. In addition an analysis technique using the reduced χ2 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.

  4. Ultrafast XUV Pulses at High Repetition Rate for Time Resolved Photoelectron Spectroscopy of Surface Dynamics

    Science.gov (United States)

    Corder, Christopher; Zhao, Peng; Li, Xinlong; Muraca, Amanda R.; Kershis, Matthew D.; White, Michael G.; Allison, Thomas K.

    2016-05-01

    Ultrafast photoelectron studies of surface dynamics are often limited by low repetition rates. At Stony Brook we have built a cavity-enhanced high-harmonic generation XUV source that delivers ultrafast pulses to a surface science apparatus for photoelectron spectroscopy. We begin with a Ytterbium fiber laser at a repetition rate of 78 MHz and up to 90 W of average power. After compression the pulses have μJ's of energy with high harmonic generation. The enhancement cavity is a six mirror double folded bow-tie geometry with a focus of 15 μm at a Krypton gas jet, followed by a Sapphire crystal at Brewster's angle for the fundamental to allow outcoupling of the harmonics. A single harmonic is selected using a time-preserving monochromator to maintain the short pulses, and is sent to an ultra high vacuum chamber with sample preparation and diagnostic tools as well as an electron energy spectrometer. This allows us to study the electronic dynamics of semiconductor surfaces and their interfaces with adsorbed molecules which enable various charge transfer effects. Supported by AFOSR.

  5. Time-resolved Ultraviolet Spectroscopy of the M-dwarf GJ 876 Exoplanetary System

    CERN Document Server

    France, Kevin; 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 aboard the Hubble Space Telescope, we have measured the 1150-3140A spectrum of GJ 876. We have reconstructed the stellar HI LyA emission line profile, and find that the integrated LyA flux is roughly equal to the rest of the integrated flux (1150-1210A + 1220-3140A) in the entire ultraviolet bandpass (F(LyA)/F(FUV+NUV) ~0.7). This ratio is ~ 2500x greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H2 (T(H2) > ...

  6. Direct Visualization of Excited-State Symmetry Breaking Using Ultrafast Time-Resolved Infrared Spectroscopy.

    Science.gov (United States)

    Dereka, Bogdan; Rosspeintner, Arnulf; Li, Zhiquan; Liska, Robert; Vauthey, Eric

    2016-04-01

    Most symmetric quadrupolar molecules designed for two-photon absorption behave as dipolar molecules in the S1 electronic excited state. This is usually explained by a breakup of the symmetry in the excited state. However, the origin of this process and its dynamics are still not fully understood. Here, excited-state symmetry breaking in a quadrupolar molecule with a D-π-A-π-D motif, where D and A are electron donating and accepting units, is observed in real time using ultrafast transient infrared absorption spectroscopy. The nature of the relaxed S1 state was found to strongly depend on the solvent polarity: (1) in nonpolar solvents, it is symmetric and quadrupolar; (2) in weakly polar media, the quadrupolar state observed directly after excitation transforms to a symmetry broken S1 state with one arm bearing more excitation than the other; and (3) in highly polar solvents, the excited state evolves further to a purely dipolar S1 state with the excitation localized entirely on one arm. The time scales associated with the transitions between these states coincide with those of solvation dynamics, indicating that symmetry breaking is governed by solvent fluctuations.

  7. Diagnosis of laser ablated carbon particles measured by time-resolved X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    The time and space resolved properties of laser ablated carbon particles were measured by X-ray absorption spectroscopy using LPX as an X-ray source. The energy density of the irradiation laser on the sample was in the range of 0.5-20J/cm2 and the time delay was varied between 0 and 120ns. The absorption spectra exhibited several peaks originated from level to level transitions and an intense broad absorption in the energy range of C-K edge. At a delay time of 120ns, the absorption peak from 1s→2p transition of neutral carbon atom (C0), C-, C+ and C2+ ions were observed. The absorption peak from C0 was stronger as the probing position was closer to the sample surface and decreased rapidly with distance from the sample surface. The absorption peak C2+ ion was observed only at comparatively distant positions from surface. The maximum speeds of highly charged ions were faster than that of neutral atoms and negative charged ions. The neutral atom and lower charged ions were emitted from the sample even after laser irradiation. The spatial distributions of the laser ablated carbon particles in the localized helium gas environment were measured. In the helium gas environment, the ablation plume was depressed by the helium cloud generated on the top of ablation plume. (author)

  8. 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.

  9. 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.

  10. 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.

  11. Ultrafast terahertz modulation characteristic of tungsten doped vanadium dioxide nanogranular film revealed by time-resolved terahertz spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Yang [College of Materials Science and Engineering, Sichuan University, Chengdu, Sichuan 610065 (China); National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics & Terahertz Research Center, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Zhai, Zhao-Hui; Zhu, Li-Guo, E-mail: zhuliguo@tsinghua.org.cn, E-mail: huangwanxia@scu.edu.cn; Li, Jun; Peng, Qi-Xian; Li, Ze-Ren [National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics & Terahertz Research Center, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Shi, Qi-Wu; Huang, Wan-Xia, E-mail: zhuliguo@tsinghua.org.cn, E-mail: huangwanxia@scu.edu.cn; Yue, Fang; Hu, Yan-Yan [College of Materials Science and Engineering, Sichuan University, Chengdu, Sichuan 610065 (China)

    2015-07-20

    The ultrafast terahertz (THz) modulation characteristic during photo-induced insulator-to-metal transition (IMT) of undoped and tungsten (W)-doped VO{sub 2} film was investigated at picoseconds time scale using time-resolved THz spectroscopy. W-doping slows down the photo-induced IMT dynamic processes (both the fast non-thermal process and the slow metallic phase propagation process) in VO{sub 2} film and also reduces the pump fluence threshold of photo-induced IMT in VO{sub 2} film. Along with the observed broadening of phase transition temperature window of IMT in W-doped VO{sub 2}, we conclude that W-doping prevents metallic phase domains from percolation. By further extracting carrier properties from photo-induced THz conductivity at several phase transition times, we found that the electron-electron correlation during IMT is enhanced in W-doped VO{sub 2}.

  12. 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.

  13. In situ time-resolved X-ray near-edge absorption spectroscopy of selenite reduction by siderite

    International Nuclear Information System (INIS)

    The reduction oxidation-reaction between aqueous selenite (SeO32-) and siderite (FeCO3(s)) was monitored by in situ, time-resolved X-ray absorption near-edge structure (XANES) spectroscopy at the selenium K edge in a controlled electrochemical environment. Spectral evolutions showed that more than 60% of selenite was reduced at the siderite surface after 20 h of experiment, at which time the reaction was still incomplete. Fitting of XANES spectra by linear combination of reference spectra showed that selenite reaction with siderite is essentially a two-step process, selenite ions being immobilized on siderite surface prior to their reduction. A kinetic model of the reduction step is proposed, allowing to identify the specific contribution of surface reduction. These results have strong implications for the retention of selenite by corrosion products in nuclear waste repositories and in a larger extent for the fate of selenium in the environment. (authors)

  14. Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy

    Science.gov (United States)

    Ponseca, C. S., Jr.; Sundström, V.

    2016-03-01

    Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

  15. Homogeneous time-resolved G protein-coupled receptor-ligand binding assay based on fluorescence cross-correlation spectroscopy.

    Science.gov (United States)

    Antoine, Thomas; Ott, David; Ebell, Katharina; Hansen, Kerrin; Henry, Luc; Becker, Frank; Hannus, Stefan

    2016-06-01

    G protein-coupled receptors (GPCRs) mediate many important physiological functions and are considered as one of the most successful therapeutic target classes for a wide spectrum of diseases. Drug discovery projects generally benefit from a broad range of experimental approaches for screening compound libraries and for the characterization of binding modes of drug candidates. Owing to the difficulties in solubilizing and purifying GPCRs, assay formats have been so far mainly limited to cell-based functional assays and radioligand binding assays. In this study, we used fluorescence cross-correlation spectroscopy (FCCS) to analyze the interaction of detergent-solubilized receptors to various types of GPCR ligands: endogenous peptides, small molecules, and a large surrogate antagonist represented by a blocking monoclonal antibody. Our work demonstrates the suitability of the homogeneous and time-resolved FCCS assay format for a robust, high-throughput determination of receptor-ligand binding affinities and kinetic rate constants for various therapeutically relevant GPCRs. PMID:26954998

  16. Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy.

    Science.gov (United States)

    Ponseca, C S; Sundström, V

    2016-03-28

    Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

  17. Radiative lifetime measurements of some Tm I and Tm II levels by time-resolved laser spectroscopy

    Science.gov (United States)

    Tian, Yanshan; Wang, Xinghao; Yu, Qi; Li, Yongfan; Gao, Yang; Dai, Zhenwen

    2016-04-01

    Radiative lifetimes of 88 levels of Tm I in the energy range 22 791.176-48 547.98 cm-1 and 29 levels of Tm II in the range 27 294.79-65 612.85 cm-1 were measured by time-resolved laser-induced fluorescence spectroscopy in laser-ablation plasma. The lifetime values obtained are in the range from 15.4 to 7900 ns for Tm I and from 36.5 to 1000 ns for Tm II. To the best of our knowledge, 77 lifetimes of Tm I and 22 lifetimes of Tm II are reported for the first time. Good agreements between the present results and the previous experimental values were achieved for both Tm I and Tm II.

  18. 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.

  19. Long-Lived Excited-State Dynamics of i-Motif Structures Probed by Time-Resolved Infrared Spectroscopy.

    Science.gov (United States)

    Keane, Páraic M; Baptista, Frederico R; Gurung, Sarah P; Devereux, Stephen J; Sazanovich, Igor V; Towrie, Michael; Brazier, John A; Cardin, Christine J; Kelly, John M; Quinn, Susan J

    2016-05-01

    UV-generated excited states of cytosine (C) nucleobases are precursors to mutagenic photoproduct formation. The i-motif formed from C-rich sequences is known to exhibit high yields of long-lived excited states following UV absorption. Here the excited states of several i-motif structures have been characterized following 267 nm laser excitation using time-resolved infrared spectroscopy (TRIR). All structures possess a long-lived excited state of ∼300 ps and notably in some cases decays greater than 1 ns are observed. These unusually long-lived lifetimes are attributed to the interdigitated DNA structure which prevents direct base stacking overlap.

  20. 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.

  1. Ultrafast time-resolved absorption spectroscopy of geometric isomers of carotenoids

    Science.gov (United States)

    Niedzwiedzki, Dariusz M.; Sandberg, Daniel J.; Cong, Hong; Sandberg, Megan N.; Gibson, George N.; Birge, Robert R.; Frank, Harry A.

    2009-02-01

    The structures of a number of stereoisomers of carotenoids have been revealed in three-dimensional X-ray crystallographic investigations of pigment-protein complexes from photosynthetic organisms. Despite these structural elucidations, the reason for the presence of stereoisomers in these systems is not well understood. An important unresolved issue is whether the natural selection of geometric isomers of carotenoids in photosynthetic pigment-protein complexes is determined by the structure of the protein binding site or by the need for the organism to accomplish a specific physiological task. The association of cis isomers of a carotenoid with reaction centers and trans isomers of the same carotenoid with light-harvesting pigment-protein complexes has led to the hypothesis that the stereoisomers play distinctly different physiological roles. A systematic investigation of the photophysics and photochemistry of purified, stable geometric isomers of carotenoids is needed to understand if a relationship between stereochemistry and biological function exists. In this work we present a comparative study of the spectroscopy and excited state dynamics of cis and trans isomers of three different open-chain carotenoids in solution. The molecules are neurosporene ( n = 9), spheroidene ( n = 10), and spirilloxanthin ( n = 13), where n is the number of conjugated π-electron double bonds. The spectroscopic experiments were carried out on geometric isomers of the carotenoids purified by high performance liquid chromatography (HPLC) and then frozen to 77 K to inhibit isomerization. The spectral data taken at 77 K provide a high resolution view of the spectroscopic differences between geometric isomers. The kinetic data reveal that the lifetime of the lowest excited singlet state of a cis-isomer is consistently shorter than that of its corresponding all- trans counterpart despite the fact that the excited state energy of the cis molecule is typically higher than that of the trans

  2. 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.

  3. A field programmable gate array-based time-resolved scaler for collinear laser spectroscopy with bunched radioactive potassium beams

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, D. M., E-mail: rossi@nscl.msu.edu; Davis, M.; Ringle, R.; Rodriguez, J. A.; Ryder, C. A.; Schwarz, S.; Sumithrarachchi, C.; Zhao, S. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States); Minamisono, K., E-mail: minamiso@nscl.msu.edu; Barquest, B. R.; Bollen, G.; Hughes, M.; Strum, R.; Tarazona, D. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States); Cooper, K.; Hammerton, K.; Mantica, P. F.; Morrissey, D. J. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States); Department of Chemistry, Michigan State University, East Lansing, Michigan 48824 (United States)

    2014-09-15

    A new data acquisition system including a Field Programmable Gate Array (FPGA) based time-resolved scaler was developed for laser-induced fluorescence and beam bunch coincidence measurements. The FPGA scaler was tested in a collinear laser-spectroscopy experiment on radioactive {sup 37}K at the BEam COoler and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory at Michigan State University. A 1.29 μs bunch width from the buncher and a bunch repetition rate of 2.5 Hz led to a background suppression factor of 3.1 × 10{sup 5} in resonant photon detection measurements. The hyperfine structure of {sup 37}K and its isotope shift relative to the stable {sup 39}K were determined using 5 × 10{sup 4} s{sup −1} {sup 37}K ions injected into the BECOLA beam line. The obtained hyperfine coupling constants A({sup 2}S{sub 1/2}) = 120.3(1.4) MHz, A({sup 2}P{sub 1/2}) = 15.2(1.1) MHz, and A({sup 2}P{sub 3/2}) = 1.4(8) MHz, and the isotope shift δν{sup 39,} {sup 37} = −264(3) MHz are consistent with the previously determined values, where available.

  4. A field programmable gate array-based time-resolved scaler for collinear laser spectroscopy with bunched radioactive potassium beams.

    Science.gov (United States)

    Rossi, D M; Minamisono, K; Barquest, B R; Bollen, G; Cooper, K; Davis, M; Hammerton, K; Hughes, M; Mantica, P F; Morrissey, D J; Ringle, R; Rodriguez, J A; Ryder, C A; Schwarz, S; Strum, R; Sumithrarachchi, C; Tarazona, D; Zhao, S

    2014-09-01

    A new data acquisition system including a Field Programmable Gate Array (FPGA) based time-resolved scaler was developed for laser-induced fluorescence and beam bunch coincidence measurements. The FPGA scaler was tested in a collinear laser-spectroscopy experiment on radioactive (37)K at the BEam COoler and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory at Michigan State University. A 1.29 μs bunch width from the buncher and a bunch repetition rate of 2.5 Hz led to a background suppression factor of 3.1 × 10(5) in resonant photon detection measurements. The hyperfine structure of (37)K and its isotope shift relative to the stable (39)K were determined using 5 × 10(4) s(-1) (37)K ions injected into the BECOLA beam line. The obtained hyperfine coupling constants A((2)S(1/2)) = 120.3(1.4) MHz, A((2)P(1/2)) = 15.2(1.1) MHz, and A((2)P(3/2)) = 1.4(8) MHz, and the isotope shift δν(39, 37) = -264(3) MHz are consistent with the previously determined values, where available. PMID:25273722

  5. A field programmable gate array-based time-resolved scaler for collinear laser spectroscopy with bunched radioactive potassium beams.

    Science.gov (United States)

    Rossi, D M; Minamisono, K; Barquest, B R; Bollen, G; Cooper, K; Davis, M; Hammerton, K; Hughes, M; Mantica, P F; Morrissey, D J; Ringle, R; Rodriguez, J A; Ryder, C A; Schwarz, S; Strum, R; Sumithrarachchi, C; Tarazona, D; Zhao, S

    2014-09-01

    A new data acquisition system including a Field Programmable Gate Array (FPGA) based time-resolved scaler was developed for laser-induced fluorescence and beam bunch coincidence measurements. The FPGA scaler was tested in a collinear laser-spectroscopy experiment on radioactive (37)K at the BEam COoler and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory at Michigan State University. A 1.29 μs bunch width from the buncher and a bunch repetition rate of 2.5 Hz led to a background suppression factor of 3.1 × 10(5) in resonant photon detection measurements. The hyperfine structure of (37)K and its isotope shift relative to the stable (39)K were determined using 5 × 10(4) s(-1) (37)K ions injected into the BECOLA beam line. The obtained hyperfine coupling constants A((2)S(1/2)) = 120.3(1.4) MHz, A((2)P(1/2)) = 15.2(1.1) MHz, and A((2)P(3/2)) = 1.4(8) MHz, and the isotope shift δν(39, 37) = -264(3) MHz are consistent with the previously determined values, where available.

  6. A field programmable gate array-based time-resolved scaler for collinear laser spectroscopy with bunched radioactive potassium beams

    Science.gov (United States)

    Rossi, D. M.; Minamisono, K.; Barquest, B. R.; Bollen, G.; Cooper, K.; Davis, M.; Hammerton, K.; Hughes, M.; Mantica, P. F.; Morrissey, D. J.; Ringle, R.; Rodriguez, J. A.; Ryder, C. A.; Schwarz, S.; Strum, R.; Sumithrarachchi, C.; Tarazona, D.; Zhao, S.

    2014-09-01

    A new data acquisition system including a Field Programmable Gate Array (FPGA) based time-resolved scaler was developed for laser-induced fluorescence and beam bunch coincidence measurements. The FPGA scaler was tested in a collinear laser-spectroscopy experiment on radioactive 37K at the BEam COoler and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory at Michigan State University. A 1.29 μs bunch width from the buncher and a bunch repetition rate of 2.5 Hz led to a background suppression factor of 3.1 × 105 in resonant photon detection measurements. The hyperfine structure of 37K and its isotope shift relative to the stable 39K were determined using 5 × 104 s-1 37K ions injected into the BECOLA beam line. The obtained hyperfine coupling constants A(2S1/2) = 120.3(1.4) MHz, A(2P1/2) = 15.2(1.1) MHz, and A(2P3/2) = 1.4(8) MHz, and the isotope shift δν39, 37 = -264(3) MHz are consistent with the previously determined values, where available.

  7. Kinetics of the reaction F+NO+M->FNO+M studied by pulse radiolysis combined with time-resolved IR and UV spectroscopy

    DEFF Research Database (Denmark)

    Pagsberg, Palle Bjørn; Sillesen, A.; Jodkowski, J.T.;

    1996-01-01

    The title reaction was initiated by pulse radiolysis of SF6/NO gas mixtures, and the formation of FNO was studied by time-resolved IR and UV spectroscopy. At SF6 pressures of 10-320 mbar at 298 K, the formation of FNO was studied by infrared diode laser spectroscopy at 1857.324 cm(-1). Comparative...

  8. Reaction mechanism of adenylyltransferase DrrA from Legionella pneumophila elucidated by time-resolved fourier transform infrared spectroscopy.

    Science.gov (United States)

    Gavriljuk, Konstantin; Schartner, Jonas; Itzen, Aymelt; Goody, Roger S; Gerwert, Klaus; Kötting, Carsten

    2014-07-01

    Modulation of the function of small GTPases that regulate vesicular trafficking is a strategy employed by several human pathogens. Legionella pneumophila infects lung macrophages and injects a plethora of different proteins into its host cell. Among these is DrrA/SidM, which catalyzes stable adenylylation of Rab1b, a regulator of endoplasmatic reticulum to Golgi trafficking, and thereby alters the function and interactions of this small GTPase. We employed time-resolved FTIR-spectroscopy to monitor the DrrA-catalyzed AMP-transfer to Tyr77 of Rab1b. A transient complex between DrrA, adenylylated Rab1b, and the pyrophosphate byproduct was resolved, allowing us to analyze the interactions at the active site. Combination of isotopic labeling and site-directed mutagenesis allowed us to derive the catalytic mechanism of DrrA from the FTIR difference spectra. DrrA shares crucial residues in the ATP-binding pocket with similar AMP-transferring enzymes such as glutamine synthetase adenylyltransferase or kanamycin nucleotidyltransferase, but provides the complete active site on a single subunit. We determined that Asp112 of DrrA functions as the catalytic base for deprotonation of Tyr77 of Rab1b to enable nucleophilic attack on the ATP. The study provides detailed understanding of the Legionella pneumophila protein DrrA and of AMP-transfer reactions in general.

  9. HELIOS—A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Plogmaker, S., E-mail: Stefan.Plogmaker@physics.uu.se, E-mail: Joachim.Terschluesen@physics.uu.se, E-mail: Johan.Soderstrom@physics.uu.se; Terschlüsen, J. A., E-mail: Stefan.Plogmaker@physics.uu.se, E-mail: Joachim.Terschluesen@physics.uu.se, E-mail: Johan.Soderstrom@physics.uu.se; Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Söderström, J., E-mail: Stefan.Plogmaker@physics.uu.se, E-mail: Joachim.Terschluesen@physics.uu.se, E-mail: Johan.Soderstrom@physics.uu.se [Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala (Sweden)

    2015-12-15

    In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20 000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ⋅ 10{sup 10} photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

  10. ''Live'' Prussian blue fading by time-resolved X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gervais, Claire [Smithsonian Institution Museum Conservation Institute, Suitland, MD (United States); Bern University of the Arts, Bern (Switzerland); Languille, Marie-Angelique [Synchrotron SOLEIL, IPANEMA, USR 3461 CNRS/MCC, Gif-sur-Yvette (France); Reguer, Solenn [Synchrotron SOLEIL, DiffAbs beamline, Gif-sur-Yvette (France); Gillet, Martine [Museum national d' histoire naturelle, Centre de Recherche sur la Conservation des Collections, Paris (France); Vicenzi, Edward P. [Smithsonian Institution Museum Conservation Institute, Suitland, MD (United States); Chagnot, Sebastien; Baudelet, Francois [Synchrotron SOLEIL, ODE beamline, Gif-sur-Yvette (France); Bertrand, Loic [Synchrotron SOLEIL, IPANEMA, USR 3461 CNRS/MCC, Gif-sur-Yvette (France); Synchrotron SOLEIL, Gif-sur-Yvette (France)

    2013-04-15

    Prussian blue (PB) is an artists' pigment that has been frequently used in many artworks but poses several problems of conservation because of its fading under light and anoxia treatment. PB fading is due to the reduction of iron(III) into iron(II) and depends a lot on the object investigated. Due to the complexity of the structure, the precise physico-chemical mechanisms behind the redox process remain obscure. In this paper, we present a procedure to investigate light- and anoxia-induced fading of PB-paper samples by means of time resolved X-ray absorption spectroscopy performed at the Fe K-edge. A system composed of a visible light source and a flux-controlled environmental cell allowed light, gas and humidity to be modified in situ. The synchrotron X-ray beam was evidenced to induce a reduction of PB and to play a major role in the kinetics. The analysis of the PB fading kinetics of a sample submitted to various gas and light environments showed that both synchrotron beam and anoxia were influencing PB reduction in a correlated way. In comparison, light was found to play a minor role. Finally, we have demonstrated that the type of paper substrate could influence significantly the kinetics of reduction. Several hypotheses to explain the correlation between PB reduction mechanism and substrate are presented. (orig.)

  11. Time-Resolved Frequency Comb Spectroscopy for Studying the Kinetics and Branching Ratio of OD+CO

    Science.gov (United States)

    Bui, Thinh Quoc; Bjork, Bryce J.; Heckl, Oliver H.; Changala, Bryan; Spaun, Ben; Okumura, Mitchio; Ye, Jun

    2016-06-01

    The chemical kinetics of the OH+CO reaction plays important roles in combustion and atmospheric processes. OH+CO has two product channels, H+CO_2 and the stabilized HOCO intermediate, with a branching ratio that is highly pressure dependent. Therefore, establishing an accurate kinetic model for this chemical system requires knowledge of the reaction rates and product yields, and the lifetimes of all molecules along a particular reaction pathway. We report the application of time-resolved frequency comb spectroscopy (TRFCS) in the mid-infrared (3.7 μm) spectral region to address the complex reaction kinetics of OD+CO at room temperature. We use the deuterated forms to avoid atmospheric water interference. This technique allows us to detect the lowest energy conformer trans-DOCO intermediate with high time-resolution and sensitivity while also permitting the direct determination of rotational state distributions of all relevant molecules. We simultaneously observe the time-dependent concentrations of trans-DOCO, OD, and D_2O which are used in conjunction with kinetics modeling to obtain the pressure- and collision partner-dependent branching ratio of OD+CO.

  12. 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.

  13. Study of Heat Transfer Dynamics from Gold Nanorods to the Environment via Time-Resolved Infrared Spectroscopy.

    Science.gov (United States)

    Nguyen, Son C; Zhang, Qiao; Manthiram, Karthish; Ye, Xingchen; Lomont, Justin P; Harris, Charles B; Weller, Horst; Alivisatos, A Paul

    2016-02-23

    Studying the local solvent surrounding nanoparticles is important to understanding the energy exchange dynamics between the particles and their environment, and there is a need for spectroscopic methods that can dynamically probe the solvent region that is in nearby contact with the nanoparticles. In this work, we demonstrate the use of time-resolved infrared spectroscopy to track changes in a vibrational mode of local water on the time scale of hundreds of picoseconds, revealing the dynamics of heat transfer from gold nanorods to the local water environment. We applied this probe to a prototypical plasmonic photothermal system consisting of organic CTAB bilayer capped gold nanorods, as well as gold nanorods coated with varying thicknesses of inorganic mesoporous-silica. The heat transfer time constant of CTAB capped gold nanorods is about 350 ps and becomes faster with higher laser excitation power, eventually generating bubbles due to superheating in the local solvent. Silica coating of the nanorods slows down the heat transfer and suppresses the formation of superheated bubbles.

  14. Time-resolved optical spectroscopy on Er-doped fluorozirconate-based glasses for efficient up-conversion

    International Nuclear Information System (INIS)

    Fluorozirconate(FZ)-based glasses have shown their potential as hosts for rare-earth (RE) ions such as Er, in these glasses REs show emissions that would be quenched in other glasses. Such material systems are of practical interest for photon up-conversion. For photovoltaic applications, the efficiency of bifacial solar cells could be vastly improved by an up-converting back layer. Up-conversion is the sequential absorption of two or more low-energy infrared photons by a RE ion followed by subsequent emission of a visible photon. This process is dependent on the intermediate level lifetime of the RE ion, which is determined by the phonon energies of the host material. Low phonon energy glasses like FZ glasses are thus desirable hosts. The lifetimes of the energy levels involved in the up-conversion process are investigated by time-resolved spectroscopy. Short laser pulses at different wavelengths are used for excitation; the emissions are detected via time-correlated photon counting. The radiative and non-radiative decay processes in Er-doped FZ glasses are analyzed and discussed.

  15. A multi-analytical investigation of semi-conductor pigments with time-resolved spectroscopy and imaging

    Science.gov (United States)

    Nevin, A.; Cesaratto, A.; D'Andrea, C.; Valentini, Gianluca; Comelli, D.

    2013-05-01

    We present the non-invasive study of historical and modern Zn- and Cd-based pigments with time-resolved fluorescence spectroscopy, fluorescence multispectral imaging and fluorescence lifetime imaging (FLIM). Zinc oxide and Zinc sulphide are semiconductors which have been used as white pigments in paintings, and the luminescence of these pigments from trapped states is strongly dependent on the presence of impurities and crystal defects. Cadmium sulphoselenide pigments vary in hue from yellow to deep red based on their composition, and are another class of semiconductor pigments which emit both in the visible and the near infrared. The Fluorescence lifetime of historical and modern pigments has been measured using both an Optical Multichannel Analyser (OMA) coupled with a Nd:YAG nslaser, and a streak camera coupled with a ps-laser for spectrally-resolved fluorescence lifetime measurements. For Znbased pigments we have also employed Fluorescence Lifetime Imaging (FLIM) for the measurement of luminescence. A case study of FLIM applied to the analysis of the painting by Vincent Van Gogh on paper - "Les Bretonnes et le pardon de Pont-Aven" (1888) is presented. Through the integration of complementary, portable and non-invasive spectroscopic techniques, new insights into the optical properties of Zn- and Cd-based pigments have been gained which will inform future analysis of late 19th] and early 20th C. paintings.

  16. 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.

  17. 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.

  18. Elucidating low-frequency vibrational dynamics in calcite and water with time-resolved third-harmonic generation spectroscopy.

    Science.gov (United States)

    Wang, Liang; Liu, Weimin; Fang, Chong

    2015-07-14

    Low-frequency vibrations are foundational for material properties including thermal conductivity and chemical reactivity. To resolve the intrinsic molecular conformational dynamics in condensed phase, we implement time-resolved third-harmonic generation (TRTHG) spectroscopy to unravel collective skeletal motions in calcite, water, and aqueous salt solution in situ. The lifetime of three Raman-active modes in polycrystalline calcite at 155, 282 and 703 cm(-1) is found to be ca. 1.6 ps, 1.3 ps and 250 fs, respectively. The lifetime difference is due to crystallographic defects and anharmonic effects. By incorporating a home-built wire-guided liquid jet, we apply TRTHG to investigate pure water and ZnCl2 aqueous solution, revealing ultrafast dynamics of water intermolecular stretching and librational bands below 500 cm(-1) and a characteristic 280 cm(-1) vibrational mode in the ZnCl4(H2O)2(2-) complex. TRTHG proves to be a compact and versatile technique that directly uses the 800 nm fundamental laser pulse output to capture ultrafast low-frequency vibrational motion snapshots in condensed-phase materials including the omnipresent water, which provides the important time dimension to spectral characterization of molecular structure-function relationships.

  19. HELIOS—A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy

    Science.gov (United States)

    Plogmaker, S.; Terschlüsen, J. A.; Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Söderström, J.

    2015-12-01

    In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20 000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ṡ 1010 photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

  20. HELIOS--A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy.

    Science.gov (United States)

    Plogmaker, S; Terschlüsen, J A; Krebs, N; Svanqvist, M; Forsberg, J; Cappel, U B; Rubensson, J-E; Siegbahn, H; Söderström, J

    2015-12-01

    In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20,000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ⋅ 10(10) photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

  1. 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.

  2. Nonlinear spectroscopy in the near-field: time resolved spectroscopy and subwavelength resolution non-invasive imaging

    Science.gov (United States)

    Namboodiri, Mahesh; Khan, Tahirzeb; Karki, Khadga; Kazemi, Mehdi Mohammad; Bom, Sidhant; Flachenecker, Günter; Namboodiri, Vinu; Materny, Arnulf

    2014-04-01

    The combination of near-field microscopy along with nonlinear optical spectroscopic techniques is presented here. The scanning near-field imaging technique can be integrated with nonlinear spectroscopic techniques to improve spatial and axial resolution of the images. Additionally, ultrafast dynamics can be probed down to nano-scale dimension. The review shows some examples for this combination, which resulted in an exciton map and vibrational contrast images with sub-wavelength resolution. Results of two-color femtosecond time-resolved pump-probe experiments using scanning near-field optical microscopy (SNOM) on thin films of the organic semiconductor 3,4,9,10 Perylenetetracarboxylic dianhydride (PTCDA) are presented. While nonlinear Raman techniques have been used to obtain highly resolved images in combination with near-field microscopy, the use of femtosecond laser pulses in electronic resonance still constitutes a big challenge. Here, we present our first results on coherent anti-Stokes Raman scattering (fs-CARS) with femtosecond laser pulses detected in the near-field using SNOM. We demonstrate that highly spatially resolved images can be obtained from poly(3-hexylthiophene) (P3HT) nano-structures where the fs-CARS process was in resonance with the P3HT absorption and with characteristic P3HT vibrational modes without destruction of the samples. Sub-diffraction limited lateral resolution is achieved. Especially the height resolution clearly surpasses that obtained with standard microCARS. These results will be the basis for future investigations of mode-selective dynamics in the near-field.

  3. Optimization of Supercontinuum Sources for Ultra-Broadband T-CARS Spectroscopy

    International Nuclear Information System (INIS)

    For a typical photonic crystal fiber with two zero-dispersion wavelengths, we theoretically demonstrate a new way to generate supercontinuum using an input pulse of 30 fs duration and 10 kW peak power for providing a compact and cost effective light source to the ultra-broadband time-resolved coherent anti-Stokes Raman scattering spectroscopy. (fundamental areas of phenomenology(including applications))

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

    Science.gov (United States)

    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.

    2014-04-01

    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 Comptonized model, we find that the peak energy, E peak, anti-correlates with flux, while the low-energy photon index remains constant at ~ - 0.8 up to a flux limit F ≈ 10-5 erg s-1 cm-2. Above this flux value, the E peak-flux correlation changes sign, and the index positively correlates with the flux reaching ~1 at the highest fluxes. Using a two blackbody model, we find that the areas and fluxes of the two emitting regions correlate positively. Further, we study here for the first time the evolution of the temperatures and areas as a function of flux. We find that the area-kT relation follows the lines of constant luminosity at the lowest fluxes, R 2vpropkT -4, with a break at the higher fluxes (F > 10-5.5 erg s-1 cm-2). The area of the high-kT component increases with the flux while its temperature decreases, which we interpret as being due to an adiabatic cooling process. The area of the low-kT component, on the other hand, appears to saturate at the highest fluxes, toward R max ≈ 30 km. Assuming that crust quakes are responsible for soft gamma repeater (SGR) bursts and considering R max as the maximum radius of the emitting photon-pair plasma fireball, we relate this saturation radius to a minimum excitation radius of the magnetosphere, and we put a lower limit on the internal magnetic field of SGR J1550-5418, B int >~ 4.5 × 1015 G.

  5. Kinetics of the F+NO2+M->FNO2+M reaction studied by pulse radiolysis combined with time-resolved IR and UV spectroscopy

    DEFF Research Database (Denmark)

    Pagsberg, Palle Bjørn; Sillesen, A.; Jodkowski, J.T.;

    1996-01-01

    The title reaction was initiated by the pulse radiolysis of SF6/NO2 gas mixtures, and the formation of FNO2 was studied by time-resolved infrared spectroscopy employing strong rotational transitions within the nu(1) and nu(4) bands of FNO2. The pressure dependence of the formation kinetics...

  6. Electronic Excited State and Vibrational Dynamics of Water Solution of Cytosine Observed by Time-resolved Transient Absorption Spectroscopy with Sub-10fs Deep Ultraviolet Laser Pules

    Directory of Open Access Journals (Sweden)

    Kobayashi Takayoshi.

    2013-03-01

    Full Text Available Time-resolved transient absorption spectroscopy for water solution of cytosine with sub-10fs deep ultraviolet laser pulse is reported. Ultrafast electronic excited state dynamics and coherent molecular vibrational dynamics are simultaneously observed and their relaxation mechanisms are discussed.

  7. Electron-hole recombination on ZnO(0001) single-crystal surface studied by time-resolved soft X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yukawa, R.; Yamamoto, S.; Ogawa, M.; Yamamoto, Sh.; Fujikawa, K.; Hobara, R.; Matsuda, I., E-mail: imatsuda@issp.u-tokyo.ac.jp [Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Ozawa, K. [Department of Chemistry and Materials Science, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan); Emori, M.; Sakama, H. [Department of Physics, Sophia University, Chiyoda-ku, Tokyo 102-8554 (Japan); Kitagawa, S.; Daimon, H. [Nara Institute of Science and Technology (NAIST), Ikoma, Nara 630-0192 (Japan)

    2014-10-13

    Time-resolved soft X-ray photoelectron spectroscopy (PES) experiments were performed with time scales from picoseconds to nanoseconds to trace relaxation of surface photovoltage on the ZnO(0001) single crystal surface in real time. The band diagram of the surface has been obtained numerically using PES data, showing a depletion layer which extends to 1 μm. Temporal evolution of the photovoltage effect is well explained by a recombination process of a thermionic model, giving the photoexcited carrier lifetime of about 1 ps at the surface under the flat band condition. This lifetime agrees with a temporal range reported by the previous time-resolved optical experiments.

  8. Ultrafast time-resolved pump-probe spectroscopy of PYP by a sub-8 fs pulse laser at 400 nm.

    Science.gov (United States)

    Liu, Jun; Yabushita, Atsushi; Taniguchi, Seiji; Chosrowjan, Haik; Imamoto, Yasushi; Sueda, Keiichi; Miyanaga, Noriaki; Kobayashi, Takayoshi

    2013-05-01

    Impulsive excitation of molecular vibration is known to induce wave packets in both the ground state and excited state. Here, the ultrafast dynamics of PYP was studied by pump-probe spectroscopy using a sub-8 fs pulse laser at 400 nm. The broadband spectrum of the UV pulse allowed us to detect the pump-probe signal covering 360-440 nm. The dependence of the vibrational phase of the vibrational mode around 1155 cm(-1) on the probe photon energy was observed for the first time to our knowledge. The vibrational mode coupled to the electronic transition observed in the probe spectral ranges of 2.95-3.05 and 3.15-3.35 eV was attributed to the wave packets in the ground state and the excited state, respectively. The frequencies in the ground state and excited state were determined to be 1155 ± 1 and 1149 ± 1 cm(-1), respectively. The frequency difference is due to change after photoexcitation. This means a reduction of the bond strength associated with π-π* excitation, which is related to the molecular structure change associated with the primary isomerization process in the photocycle in PYP. Real-time vibrational modes at low frequency around 138, 179, 203, 260, and 317 cm(-1) were also observed and compared with the Raman spectrum for the assignment of the vibrational wave packet.

  9. Complexation of polyacrylates by Ca2+ ions. Time-resolved studies using attenuated total reflectance Fourier transform infrared dialysis spectroscopy.

    Science.gov (United States)

    Fantinel, Fabiana; Rieger, Jens; Molnar, Ferenc; Hübler, Patrick

    2004-03-30

    The attenuated total reflectance Fourier transform infrared dialysis technique is introduced for the time-resolved investigation of the binding processes of Ca2+ to polyacrylates dissolved in water. We observed transient formation of intermediates in water with various types of coordination of the carboxylate group to Ca2+ throughout the complexation steps. Time-resolved changes in the spectra were analyzed with principal component analysis, from which the spectral species were obtained as well as their formation kinetics. We propose a model for the mechanisms of Ca2+ coordination to polyacrylates. The polymer chain length plays an important role in Ca2+ binding. PMID:15835120

  10. Time resolved spectroscopy of SGR J1550–5418 bursts detected with Fermi/gamma-ray burst monitor

    Energy Technology Data Exchange (ETDEWEB)

    Younes, G. [Universities Space Research Association, 6767 Old Madison Pike, Suite 450, Huntsville, AL 35806 (United States); Kouveliotou, C.; Collazzi, A. [Astrophysics Office, ZP 12, NASA-Marshall Space Flight Center, Huntsville, AL 35812 (United States); Van der Horst, A. J.; Watts, A. L.; Huppenkothen, D.; Van der Klis, M.; Van Putten, T. [Astronomical Institute " Anton Pannekoek," University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raánana 43537 (Israel); Bhat, P. N.; Gorgone, N. [University of Alabama in Huntsville CSPAR, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Gehrels, N.; Mcenery, J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Göğüş, E.; Kaneko, Y.; Lin, L. [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Gruber, D.; Von Kienlin, A. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany); Grunblatt, S. [University of Hawaii at Manoa, 2500 Campus Road, Honolulu, HI 96822 (United States); and others

    2014-04-10

    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 Comptonized model, we find that the peak energy, E {sub peak}, anti-correlates with flux, while the low-energy photon index remains constant at ∼ – 0.8 up to a flux limit F ≈ 10{sup –5} erg s{sup –1} cm{sup –2}. Above this flux value, the E {sub peak}–flux correlation changes sign, and the index positively correlates with the flux reaching ∼1 at the highest fluxes. Using a two blackbody model, we find that the areas and fluxes of the two emitting regions correlate positively. Further, we study here for the first time the evolution of the temperatures and areas as a function of flux. We find that the area–kT relation follows the lines of constant luminosity at the lowest fluxes, R {sup 2}∝kT {sup –4}, with a break at the higher fluxes (F > 10{sup –5.5} erg s{sup –1} cm{sup –2}). The area of the high-kT component increases with the flux while its temperature decreases, which we interpret as being due to an adiabatic cooling process. The area of the low-kT component, on the other hand, appears to saturate at the highest fluxes, toward R {sub max} ≈ 30 km. Assuming that crust quakes are responsible for soft gamma repeater (SGR) bursts and considering R {sub max} as the maximum radius of the emitting photon-pair plasma fireball, we relate this saturation radius to a minimum excitation radius of the magnetosphere, and we put a lower limit on the internal magnetic field of SGR J1550–5418, B {sub int} ≳ 4.5 × 10{sup 15} G.

  11. Broadband Phase Spectroscopy over Turbulent Air Paths.

    Science.gov (United States)

    Giorgetta, Fabrizio R; Rieker, Gregory B; Baumann, Esther; Swann, William C; Sinclair, Laura C; Kofler, Jon; Coddington, Ian; Newbury, Nathan R

    2015-09-01

    Broadband atmospheric phase spectra are acquired with a phase-sensitive dual-frequency-comb spectrometer by implementing adaptive compensation for the strong decoherence from atmospheric turbulence. The compensation is possible due to the pistonlike behavior of turbulence across a single spatial-mode path combined with the intrinsic frequency stability and high sampling speed associated with dual-comb spectroscopy. The atmospheric phase spectrum is measured across 2 km of air at each of the 70,000 comb teeth spanning 233  cm(-1) across hundreds of near-infrared rovibrational resonances of CO(2), CH(4), and H(2)O with submilliradian uncertainty, corresponding to a 10(-13) refractive index sensitivity. Trace gas concentrations extracted directly from the phase spectrum reach 0.7 ppm uncertainty, demonstrated here for CO(2). While conventional broadband spectroscopy only measures intensity absorption, this approach enables measurement of the full complex susceptibility even in practical open path sensing.

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

    International Nuclear Information System (INIS)

    Graphical abstract: The first time resolved FTIR investigation of a GTPase reaction of a protein anchored at a single lipid bilayer. Display Omitted Highlights: ► FTIR difference spectroscopy monitors protein dynamics with atomic detail. ► ATR–FTIR allows the measurement of a monolayer sample. ► Membrane proteins can be investigated near physiological conditions. ► 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.

  13. Time-resolved resonance Raman spectroscopy of 1,3,5-hexatrienes in the lowest excited triplet state. The potential energy surface in T1

    OpenAIRE

    Wilbrandt, R; Langkilde, F.W.; Brouwer, A.M.; Negri, F; Orlandi, G.

    1990-01-01

    Time-resolved resonance Raman spectroscopy is applied to the study of the T1 state of 1,3,5-hexatriene and deuteriated and methylated derivatives in solution. The technique is described briefly. The experimentally obtained resonance Raman spectra are discussed in the light of theoretical Quantum Chemical Force Field calculations. Implications for the potential energy surface of the T1 state are discussed.

  14. Photoinduced phenoxyl radical formation from ligno- p-cresol as studied by steady-state and time-resolved EPR spectroscopy

    Science.gov (United States)

    Tero-Kubota, Shozo; Tachikawa, Takashi; Ito, Fuyuki; Matsui, Mikio; Konishi, Kazuyori

    2003-11-01

    The phenoxyl radical formation mechanism from the UV-photolysis of ligno- p-cresol in organic solvents has been investigated by steady-state and time-resolved EPR spectroscopy. It is suggested that the phenoxyl radical is generated from the o-methoxy phenol moiety in the main chain of the polymer through the dissociative photoionization by the biphotonic process from the excited triplet states.

  15. NI-49SMART SUCKER: NEXT GENERATION SMART SURGICAL TOOL FOR INTRAOPERATIVE BRAIN TUMOR RESECTION USING TIME RESOLVED LASER INDUCED FLUORESCENCE SPECTROSCOPY

    OpenAIRE

    Kittle, David S.; Butte, Pramod V.; Vasefi, Fartash; Patil, Chirag G.; Black, Keith

    2014-01-01

    Primary brain tumors are highly lethal tumors where surgical resection is the primary treatment of choice. It has been shown that survival rate is directly related to the extent of tumor resection. In order to aid the surgeon in achieving near-complete resection, novel technologies are required. Time-resolved laser induced fluorescence spectroscopy (TRLIFS) promises to be one such technology, where the tissue is excited using an ultra-short laser and the corresponding fluorescence intensity d...

  16. Comparison of beetroot extracts originating from several sites using time-resolved laser-induced fluorescence spectroscopy

    Science.gov (United States)

    Rabasović, M. S.; Šević, D.; Terzić, M.; Marinković, B. P.

    2012-05-01

    Beetroot (Beta vulgaris) juice contains a large number of fluorophores which can fluoresce. There is a growing interest in beetroot extracts analysis. In contrast, there is only limited information about beetroot obtained without sample preparation and/or extraction of components from the sample. In this work, we continue our previous study (Rabasović et al 2009 Acta Phys. Pol. A 116 570-2), analyzing and comparing beetroot extracts from several sites, using the time-resolved laser-induced fluorescence technique to measure the fluorescence of samples at different excitation wavelengths (340-470 nm) and for different sample dilutions.

  17. Time-resolved measurement of atomic emission enhancement by fs-ns dual-pulsed laser-induced breakdown spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Yan Li-Xin; Zhang Yong-Sheng; Zheng Guo-Xin; Liu Jing-Ru; Cheng Jian-Ping; Lü Min

    2006-01-01

    Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to the enhancement effect are made mainly by the bremsstrahlung radiation and cascade ionization.

  18. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

    Science.gov (United States)

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

    2016-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the

  19. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

    Science.gov (United States)

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

    2016-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the

  20. Study of the laser-induced decomposition of energetic materials at static high-pressure by time-resolved absorption spectroscopy

    Science.gov (United States)

    Hebert, Philippe; Saint-Amans, Charles

    2013-06-01

    A detailed description of the reaction rates and mechanisms occurring in shock-induced decomposition of condensed explosives is very important to improve the predictive capabilities of shock-to-detonation transition models. However, direct measurements of such experimental data are difficult to perform during detonation experiments. By coupling pulsed laser ignition of an explosive in a diamond anvil cell (DAC) with time-resolved streak camera recording of transmitted light, it is possible to make direct observations of deflagration phenomena at detonation pressure. We have developed an experimental set-up that allows combustion front propagation rates and time-resolved absorption spectroscopy measurements. The decomposition reactions are initiated using a nanosecond YAG laser and their kinetics is followed by time-resolved absorption spectroscopy. The results obtained for two explosives, nitromethane (NM) and HMX are presented in this paper. For NM, a change in reactivity is clearly seen around 25 GPa. Below this pressure, the reaction products are essentially carbon residues whereas at higher pressure, a transient absorption feature is first observed and is followed by the formation of a white amorphous product. For HMX, the evolution of the absorption as a function of time indicates a multi-step reaction mechanism which is found to depend on both the initial pressure and the laser fluence.

  1. Femtosecond time-resolved difference absorption spectroscopy of all-trans-β-Apo-8′-carotenal

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lei; QUAN Donghui; WANG Li; YANG Guozhen; WENG Yuxiang

    2004-01-01

    The femtosecond time-resolved difference absorption spectra of all-trans-βApo-8′-carotenal have been recorded and analyzed by the singular-value decomposition (SVD) method followed by global fitting using a sequential model for the excited-state energy relaxation. With this model, we have obtained the excited-state absorption spectra and the lifetimes of the corresponding excited states both in nonpolar solvent n-hexane and polar solvent methanol. Three excited states, namely S3(170fs), S2(2.32ps) and S1(26ps) in n-hexane, and two excited states S2 (190fs) and S1(9.4ps) in methanol have been observed. The excited-state absorption spectra of all-trans-β-Apo-8′-carotenal in methanol display a red shift and broadeness, while the lifetime of S1 state becomes shorter. It is proposed that these effects are related to the presence of a carbonyl functional group that leads to the solvent effect on the excited-state energy level. At the same time, it is shown that the SVD method is a useful tool in resolving the time-resolved absorption spectra.

  2. 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.

  3. Photocarrier dynamics in undoped and Na-doped Cu2ZnSnS4 single crystals revealed by ultrafast time-resolved terahertz spectroscopy

    Science.gov (United States)

    Quang Phuong, Le; Okano, Makoto; Yamashita, Genki; Nagai, Masaya; Ashida, Masaaki; Nagaoka, Akira; Yoshino, Kenji; Kanemitsu, Yoshihiko

    2015-06-01

    We investigated the effects of sodium doping on the photocarrier dynamics in Cu2ZnSnS4 (CZTS) single crystals using optical pump-THz probe transient reflectivity (THz-TR) and time-resolved photoluminescence (PL) spectroscopy. The THz-TR and PL decay dynamics are influenced by sodium doping, and their sodium-induced changes are consistent with each other. These time-resolved measurements revealed that the lifetime of photocarriers increases with sodium doping. This result indicates that a part of defects is suppressed by doping sodium into CZTS and implies that sodium doping improves the charge transport properties of CZTS, leading to an improvement in the performance of CZTS-based solar cells.

  4. Time-resolvedspectroscopy measurements of hot-electron equilibration dynamics in thin-foil solid targets: Collisional and collective effects

    International Nuclear Information System (INIS)

    Time-resolvedspectroscopy measurements from high-intensity laser interactions with thin-foil solid targets are reviewed. Thin Cu foils were irradiated with 1- to 10-J, 1-ps pulses at focused intensities from 1018 to 1019 W/cm2. The experimental data show Kα-emission pulse widths from 3 to 6 ps, increasing with laser intensity. The time-resolved Kα-emission data are compared to a hot-electron transport and Kα-production model that includes collisional electron-energy coupling, resistive heating, and electromagnetic field effects. The experimental data show good agreement with the model when a reduced ponderomotive scaling is used to describe the initial mean hot-electron energy over the relevant intensity range

  5. Time-resolved K α spectroscopy measurements of hot-electron equilibration dynamics in thin-foil solid targets: collisional and collective effects

    Science.gov (United States)

    Nilson, P. M.; Solodov, A. A.; Davies, J. R.; Theobald, W.; Mileham, C.; Stoeckl, C.; Begishev, I. A.; Zuegel, J. D.; Froula, D. H.; Betti, R.; Meyerhofer, D. D.

    2015-11-01

    Time-resolved K α spectroscopy measurements from high-intensity laser interactions with thin-foil solid targets are reviewed. Thin Cu foils were irradiated with 1-10 J, 1 ps pulses at focused intensities from 1018 to 1019 W cm-2. The experimental data show K α -emission pulse widths from 3 to 6 ps, increasing with laser intensity. The time-resolved K α -emission data are compared to a hot-electron transport and K α -production model that includes collisional electron-energy coupling, resistive heating, and electromagnetic field effects. The experimental data show good agreement with the model when a reduced ponderomotive scaling is used to describe the initial mean hot-electron energy over the relevant intensity range.

  6. Radiative lifetime measurements of odd-parity highly-excited levels of Sn I by time-resolved laser spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Xu Jia-Xin; Feng Yan-Yan; Sun Gui-Juan; Dai Zhen-Wen

    2009-01-01

    Natural radiative lifetimes of five higher-lying odd-parity levels 5pTs 3p1o,5p5d 1p1o,5p6d 3F2o,3D1o and 3F3o in neutral tin are measured by the time-resolved laser-induced fluorescence (TR-LIF) technique and the atomic beam method. All these lifetimes are not longer than 100 ns and they are found to be shorter than the lifetimes of evenparity levels in the same energy region. The results reported in this paper provide important transition parameters for highly-excited atomic Sn,which may be useful for theoretically calculating excited heavy atoms.

  7. 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.

  8. 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.

  9. Charge Photoinjection in Intercalated and Covalently Bound [Re(CO)_(3)(dppz)(py)]^(+)–DNA Constructs Monitored by Time-Resolved Visible and Infrared Spectroscopy

    OpenAIRE

    Olmon, Eric D.; Sontz, Pamela A.; Blanco-Rodríguez, Ana María; Towrie, Michael; Clark, Ian P; Vlček, Antonín; Barton, Jacqueline K.

    2011-01-01

    The complex [Re(CO)_(3)(dppz)(py′-OR)]+ (dppz = dipyrido[3,2-a:2′,3′-c]phenazine; py′-OR = 4-functionalized pyridine) offers IR sensitivity and can oxidize DNA directly from the excited state, making it a promising probe for the study of DNA-mediated charge transport (CT). The behavior of several covalent and noncovalent Re–DNA constructs was monitored by time-resolved IR (TRIR) and UV/visible spectroscopies, as well as biochemical methods, confirming the long-range oxidation of DNA by the ex...

  10. 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.

  11. Scintillating screen CCD camera using fast analog on-chip storage for time-resolved x-ray absorption spectroscopy

    Science.gov (United States)

    Koch, Andreas; Hagelstein, Michael; San Miguel, Alfonso; Fontaine, Alain; Ressler, Thorsten

    1995-03-01

    Serial readout of cooled, linear Si-photodiode arrays or CCDs offer a high dynamic range but only at moderate pixel readout rates. Recording spectroscopic information, i.e. 1D images, requires only a few sensitive lines of a 2D CCD array. A camera is presented where the unexposed part of the CCD is used as a buffer to store successive spectra with high frame rates. In this 'streak mode' the time resolution for data acquisition depends only on the line shift time of the CCD and no longer on the slow pixel readout time. A frame rate of 10 kHz for X-ray absorption spectra has been achieved. The CCD is part of an X-ray camera consisting of a scintillating screen lens-coupled to the CCD. The camera provides a high dynamic range of 17 bit, a spatial resolution of 60 micrometers (FWHM) and a high detective quantum efficiency of > 40% for x- ray energies between 4 keV and 25 keV. The camera is used for time- resolved energy-dispersive XAFS (X-ray Absorption Fine Structure) experiments. This technique permits the study of time-dependent variations of electronic properties and the local environment of atoms under induced external perturbation.

  12. Steady state and time-resolved fluorescence spectroscopy of quinine sulfate dication bound to sodium dodecylsulfate micelles: Fluorescent complex formation

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Sunita; Pant, Debi D., E-mail: ddpant@pilani.bits-pilani.ac.in

    2014-01-15

    Interaction of quinine sulfate dication (QSD) with anionic, sodium dodecylsulphate (SDS) surfactant has been studied at different premicellar, micellar and postmicellar concentrations in aqueous phase using steady state, time-resolved fluorescence and fluorescence anisotropy techniques. At premicellar concentrations of SDS, the decrease in absorbance, appearance of an extra fluorescence band at lower wavelengths and tri-exponential decay behavior of fluorescence, are attributed to complex formation between QSD molecules and surfactant monomers. At postmicellar concentrations the red shift in fluorescence spectrum, increase in quantum yield and increase in fluorescence lifetimes are attributed to incorporation of solute molecules to micelles. At lower concentrations of SDS, a large shift in fluorescence is observed on excitation at the red edge of absorption spectrum and this is explained in terms of distribution of ion pairs of different energies in the ground state and the observed fluorescence lifetime behavior corroborates with this model. The temporal fluorescence anisotropy decay of QSD in SDS micelles allowed determination of restriction on the motion of the fluorophore. All the different techniques used in this study reveal that the photophysics of QSD is very sensitive to the microenvironments of SDS micelles and QSD molecules reside at the water-micelle interface. -- Highlights: • Probe molecule is very sensitive to microenvironment of micelles. • Highly fluorescent ion-pair formation has been observed. • Modulated photophysics of probe molecule in micellar solutions has been observed. • Probe molecules strongly bind with micelles and reside at probe–micelle interface.

  13. A theoretical analysis of the spin dynamics of magnetic adatoms traced by time-resolved scanning tunneling spectroscopy

    Science.gov (United States)

    Schüler, M.; Pavlyukh, Y.; Berakdar, J.

    2012-04-01

    Inelastic scanning tunneling microscopy (STM) has recently been shown (Loth et al 2010 Science 329 1628) to be extendable to access the nanosecond, spin-resolved dynamics of magnetic adatoms and molecules. Here we analyze this novel tool theoretically by considering the time-resolved spin dynamics of a single adsorbed Fe atom excited by a tunneling current pulse from a spin-polarized STM tip. The adatom spin configuration can be controlled and probed by applying voltage pulses between the substrate and the spin-polarized STM tip. We demonstrate how, in a pump-probe manner, the relaxation dynamics of the sample spin is manifested in the spin-dependent tunneling current. Our model calculations are based on the scattering theory in a wave-packet formulation. The scheme is non-perturbative and, hence, is valid for all voltages. The numerical results for the tunneling probability and the conductance are contrasted with the predictions of simple analytical models and compared with experiments.

  14. Characterization of the ionization degree evolution of the PF-400J plasma sheath by means of time resolved optical spectroscopy

    Science.gov (United States)

    Avaria, G.; Cuadrado, O.; Moreno, J.; Pavez, C.; Soto, L.

    2016-05-01

    Spectral measurements in the visible range of the plasma sheath ionization degree evolution on the plasma focus device PF-400J are presented. The measurements were done with temporal and spatial resolution in a plasma focus device of low stored energy: PF-400J (176-539 J, 880 nF, 20-35 kV, quarter period ∼ 300ns) [1]. An ICCD was attached to a 0.5 m focal length visible spectrometer, which enabled the acquisition of time resolved spectrum with 20 ns integration time throughout the whole current pulse evolution. The spatial resolution was attained using a set of lenses which allowed the focusing of a small volume of the plasma sheath in different positions of the inter-electrode space. Discharges were carried out in mixtures of Hydrogen with gases in different proportions: 5% Neon, 5% Krypton and 2% Nitrogen. Discharges using Neon as an impurity showed no ionization of the gas, just a very low intensity emission of Ne I at times much larger than the maximum current. Nitrogen, on the other hand, showed a high ionization reaching N V (N 4+) at the end of the axial phase, with a distinctive evolution of the ionization degree as the plasma sheath moved towards the end of the electrodes. A mixed result was found when using Krypton, since the ionization degree only reached levels around Kr II/III, even though it has an ionization potential lower than Neon.

  15. Time-resolved step-scan Fourier transform infrared spectroscopy reveals differences between early and late M intermediates of bacteriorhodopsin.

    Science.gov (United States)

    Rödig, C; Chizhov, I; Weidlich, O; Siebert, F

    1999-05-01

    In this report, from time-resolved step-scan Fourier transform infrared investigations from 15 ns to 160 ms, we provide evidence for the subsequent rise of three different M states that differ in their structures. The first state rises with approximately 3 microseconds to only a small percentage. Its structure as judged from amide I/II bands differs in small but well-defined aspects from the L state. The next M state, which appears in approximately 40 microseconds, has almost all of the characteristics of the "late" M state, i.e., it differs considerably from the first one. Here, the L left arrow over right arrow M equilibrium is shifted toward M, although some percentage of L still persists. In the last M state (rise time approximately 130 microseconds), the equilibrium is shifted toward full deprotonation of the Schiff base, and only small additional structural changes take place. In addition to these results obtained for unbuffered conditions or at pH 7, experiments performed at lower and higher pH are presented. These results are discussed in terms of the molecular changes postulated to occur in the M intermediate to allow the shift of the L/M equilibrium toward M and possibly to regulate the change of the accessibility of the Schiff base necessary for effective proton pumping. PMID:10233083

  16. Ultrafast nuclear dynamics in halomethanes studied with time-resolved Coulomb explosion imaging and channel-selective Fourier spectroscopy

    Science.gov (United States)

    Malakar, Y.; Kaderiya, B.; Pearson, W. L.; Ziaee, F.; Kanaka Raju, P.; Zohrabi, M.; Jensen, K.; Rajput, J.; Ben-Itzhak, I.; Rolles, D.; Rudenko, A.

    2016-05-01

    Halomethanes have recently attracted considerable attention since they often serve as prototype systems for laser-controlled chemistry (e.g., selective bond breaking or concerted elimination reactions), and are important molecules in atmospheric chemistry. Here we combine a femtosecond laser pump-probe setup with coincident 3D ion momentum imaging apparatus to study strong-field induced nuclear dynamics in methane and several of its halogenated derivatives (CH3 I, CH2 I2, CH2 ICl). We apply a time-resolved Coulomb explosion imaging technique to map the nuclear motion on both, bound and continuum potential surfaces, disentangle different fragmentation pathways and, for halogenated molecules, observe clear signatures of vibrational wave packets in neutral or ionized states. Channel-selective and kinetic-energy resolved Fourier analysis of these data allows for unique identification of different electronic states and vibrational modes responsible for a particular structure. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. DOE. K. R. P. and W. L. P. supported by NSF Award No. IIA-143049. K.J. supported by the NSF-REU Grant No. PHYS-1461251.

  17. Time resolved study of the emission enhancement mechanisms in orthogonal double-pulse laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sanginés, R., E-mail: roberto.sangines@ccadet.unam.mx; Sobral, H.

    2013-10-01

    The evolution of laser induced ablation plume on aluminum targets has been investigated in orthogonal pre-ablation double pulse scheme at atmospheric pressure from the earliest stages of plasma evolution. Time-resolved emission spectra from neutrals, singly- and doubly-ionized species obtained with the double pulse experiment have been compared with those from the single pulse configuration. Signal-to-noise enhancement reaches values of up to 15 depending on the analyzed species; and the lower the charge state the later its maximum signal-to-noise ratio is reached. Ablation plume dynamics was monitored from 10 ns after the plasma onset via shadowgraphy and fast-photography with narrow interference filters to follow the evolution of individual species. Results show that ionic species from the target are located at the plasma core while nitrogen from the background air is found at the plume peripheral. Initially both configurations exhibit similar ablation plume sizes and their expansions were successfully fitted with the strong explosion model for the first 500 ns. At later times a good agreement was obtained by using the drag model, which predicts that the plume expansion eventually stops due to interaction with the background gas particles. The emission enhancement measured in the double pulse scheme is discussed in terms of the models describing the plume dynamics. - Highlights: • Production of 2 + ions at the earliest stages of plasma evolution • The higher the charge state the inner the location within the ablation plume. • The expansion rate of the second (ablation) plume was measured. • Shock and drag models successfully fit the ablation shock front expansion.

  18. Broadband Dielectric Spectroscopy on Human Blood

    CERN Document Server

    Wolf, M; Lunkenheimer, P; Loidl, A

    2011-01-01

    Dielectric spectra of human blood reveal a rich variety of dynamic processes. Achieving a better characterization and understanding of these processes not only is of academic interest but also of high relevance for medical applications as, e.g., the determination of absorption rates of electromagnetic radiation by the human body. The dielectric properties of human blood are studied using broadband dielectric spectroscopy, systematically investigating the dependence on temperature and hematocrit value. By covering a frequency range from 1 Hz to 40 GHz, information on all the typical dispersion regions of biological matter is obtained. We find no evidence for a low-frequency relaxation (alpha-relaxation) caused, e.g., by counterion diffusion effects as reported for some types of biological matter. The analysis of a strong Maxwell-Wagner relaxation arising from the polarization of the cell membranes in the 1-100 MHz region (beta-relaxation) allows for the test of model predictions and the determination of variou...

  19. 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.

  20. Depth profiling for the identification of unknown substances and concealed content at remote distances using time-resolved stand-off Raman spectroscopy.

    Science.gov (United States)

    Zachhuber, Bernhard; Gasser, Christoph; Ramer, Georg; Chrysostom, Engelene t H; Lendl, Bernhard

    2012-08-01

    Time-resolved stand-off Raman spectroscopy was used to determine both the position and identity of substances relative to each other at remote distances (up to tens of meters). Spectral information of three xylene isomers, toluene, and sodium chlorate was obtained at a distance of 12 m from the setup. Pairs and triplets of these samples were placed at varying distances (10-60 cm) relative to each other. Via the photon time of flight the distance between the individual samples was determined to an accuracy of 7% (corresponding to a few cm) of the physically measured distance. Furthermore, at a distance of 40 m, time-resolved Raman depth profiling was used to detect sodium chlorate in a white plastic container that was non-transparent to the human eye. The combination of the ranging capabilities of Raman LIDAR (sample location usually determined using prior knowledge of the analyte of interest) with stand-off Raman spectroscopy (analyte detection at remote distances) provides the capability for depth profile identification of unknown substances and analysis of concealed content in distant objects. To achieve these results, a 532 nm laser with a pulse length of 4.4 ns was synchronized to an intensified charge-coupled device camera with a minimum gate width of 500 ps. For automated data analysis a multivariate curve resolution algorithm was employed. PMID:22800681

  1. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Li, Deyong; Li, Yunliang; Li, Hao; Weng, Yuxiang, E-mail: yxweng@iphy.ac.cn [Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wu, Xianyou [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China); Yu, Qingxu [School of Physics and Optoelectronic Technology, Dalian University of Technology, No. 2, Linggong Road, Dalian 116023 (China)

    2015-05-15

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm{sup −1} as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10{sup −4} ΔOD for a single wavelength detection, and 2 × 10{sup −4} ΔOD for spectral detection in amide I′ region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

  2. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity.

    Science.gov (United States)

    Li, Deyong; Li, Yunliang; Li, Hao; Wu, Xianyou; Yu, Qingxu; Weng, Yuxiang

    2015-05-01

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm(-1) as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10(-4) ΔOD for a single wavelength detection, and 2 × 10(-4) ΔOD for spectral detection in amide I' region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

  3. 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.

  4. 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

    2004-03-01

    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 muscle SmO2 and tHb.

  5. Time-Resolved Spectroscopy of the 3 Brightest and Hardest Short Gamma-Ray Bursts Observed with the FGST Gamma-Ray Burst Monitor

    CERN Document Server

    Guiriec, Sylvain; Connaugthon, Valerie; Kara, Erin; Daigne, Frederic; Kouveliotou, Chryssa; van der Horst, Alexander J; Paciesas, William; Meegan, Charles A; Bhat, P N; Foley, Suzanne; Bissaldi, Elisabetta; Burgess, Michael; Chaplin, Vandiver; Diehl, Roland; Fishman, Gerald; Gibby, Melissa; Giles, Misty; Goldstein, Adam; Greiner, Jochen; Gruber, David; von Kienlin, Andreas; Kippen, Marc; McBreen, Sheila; Preece, Robert; Rau, Arne; Tierney, Dave; Wilson-Hodge, Colleen

    2010-01-01

    From July 2008 to October 2009, the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope (FGST) has detected 320 Gamma-Ray Bursts (GRBs). About 20% of these events are classified as short based on their T90 duration below 2 s. We present here for the first time time-resolved spectroscopy at timescales as short as 2 ms for the three brightest short GRBs observed with GBM. The time-integrated spectra of the events deviate from the Band function, indicating the existence of an additional spectral component, which can be fit by a power-law with index ~-1.5. The time-integrated Epeak values exceed 2 MeV for two of the bursts, and are well above the values observed in the brightest long GRBs. Their Epeak values and their low-energy power-law indices ({\\alpha}) confirm that short GRBs are harder than long ones. We find that short GRBs are very similar to long ones, but with light curves contracted in time and with harder spectra stretched towards higher energies. In our time-resolved spectrosco...

  6. Implementation of time-resolved step-scan fourier transform infrared (FT-IR) spectroscopy using a kHz repetition rate pump laser.

    Science.gov (United States)

    Magana, Donny; Parul, Dzmitry; Dyer, R Brian; Shreve, Andrew P

    2011-05-01

    Time-resolved step-scan Fourier transform infrared (FT-IR) spectroscopy has been shown to be invaluable for studying excited-state structures and dynamics in both biological and inorganic systems. Despite the established utility of this method, technical challenges continue to limit the data quality and more wide ranging applications. A critical problem has been the low laser repetition rate and interferometer stepping rate (both are typically 10 Hz) used for data acquisition. Here we demonstrate significant improvement in the quality of time-resolved spectra through the use of a kHz repetition rate laser to achieve kHz excitation and data collection rates while stepping the spectrometer at 200 Hz. We have studied the metal-to-ligand charge transfer excited state of Ru(bipyridine)(3)Cl(2) in deuterated acetonitrile to test and optimize high repetition rate data collection. Comparison of different interferometer stepping rates reveals an optimum rate of 200 Hz due to minimization of long-term baseline drift. With the improved collection efficiency and signal-to-noise ratio, better assignments of the MLCT excited-state bands can be made. Using optimized parameters, carbonmonoxy myoglobin in deuterated buffer is also studied by observing the infrared signatures of carbon monoxide photolysis upon excitation of the heme. We conclude from these studies that a substantial increase in performance of ss-FT-IR instrumentation is achieved by coupling commercial infrared benches with kHz repetition rate lasers.

  7. In-situ analysis of fruit anthocyanins by means of total internal reflectance, continuous wave and time-resolved spectroscopy

    Science.gov (United States)

    Zude, Manuela; Spinelli, Lorenzo; Dosche, Carsten; Torricelli, Alessandro

    2009-08-01

    In sweet cherry (Prunus avium), the red pigmentation is correlated with the fruit maturity stage and can be measured by non-invasive spectroscopy. In the present study, the influence of varying fruit scattering coefficients on the fruit remittance spectrum (cw) were corrected with the effective pathlength and refractive index in the fruit tissue obtained with distribution of time-of-flight (DTOF) readings and total internal reflection fluorescence (TIRF) analysis, respectively. The approach was validated on fruits providing variation in the scattering coefficient outside the calibration sample set. In the validation, the measuring uncertainty when non-invasively analyzing fruits with cw method in comparison with combined application of cw, DTOF, and TIRF measurements showed an increase in r2 up to 22.7 % with, however, high errors in all approaches.

  8. Photoinduced electron transfer between 2-methylanthraquinone and triethylamine in an ionic liquid: time-resolved EPR and transient absorption spectroscopy study.

    Science.gov (United States)

    Zhu, Guanglai; Wang, Yu; Fu, Haiying; Xu, Xinsheng; Cui, Zhifeng; Ji, Xuehan; Wu, Guozhong

    2015-02-25

    Photoinduced electron transfer between 2-methylanthraquinone (MeAQ) and triethylamine (TEA) in a room-temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), was investigated by comparing the time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy and the transient absorption spectroscopy. The results of TR-EPR spectroscopy, in which MeAQ was 8 mmol L(-1) and TEA was 150 mmol L(-1), indicated that the transient radical would exist longer time in [bmim][PF6] than in acetonitrile. At the delay time of 8 μs after laser excitation, the TR-EPR signal transformed from an emissive peak into an absorptive peak when the experiment was performed in [bmim][PF6]. The results of the transient absorption spectroscopy, in which MeAQ was 0.1 mmol L(-1) and TEA was 2.2 mmol L(-1), showed that the efficiency and the rate of the photoinduced electron transfer reaction in [bmim][PF6] were obviously lower than that in acetonitrile. It was concluded that various factors, such as concentration, viscosity and local structural transformation of the solution, have an influence on the process of photoinduced electron transfer in [bmim][PF6].

  9. 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...

  10. Effects of aging on working memory performance and prefrontal cortex activity:A time-resolved spectroscopy study

    Institute of Scientific and Technical Information of China (English)

    Jie Shi; Wenjing Zhou; Tongchao Geng; Huancong Zuo; Masahiro Tanida; Kaoru Sakatani

    2016-01-01

    Objective:This study aimed to employ time‐resolved spectroscopy (TRS) to explore age‐related differences in prefrontal cortex (PFC) activity while subjects performed a working memory task. Methods:We employed TRS to measure PFC activity in ten healthy younger and ten healthy older subjects while they performed a working memory (WM) task. All subjects performed the Sternberg test (ST) in which the memory‐set size varied between one and six digits. Using TRS, we recorded changes in cerebral blood oxygenation as a measure of changes in PFC activity during the task. In order to identify left/right asymmetry of PFC activity during the working memory task, we calculated the laterality score, i.e.,Δoxy‐Hb (rightΔoxy‐Hb—leftΔoxy‐Hb);positive values indicate greater activity in the right PFC, while negative values indicate greater activity in the left PFC. Results:During the ST, statistical analyses showed no significant differences between the younger and older groups in accuracy for low memory‐load and high memory‐load. In high memory‐load tasks, however, older subjects were slower than younger subjects (P Conclusions: The present results are consistent with the hemispheric asymmetry reduction in older adults (HAROLD) model;working memory tasks cause asymmetrical PFC activation in younger adults, while older adults tend to show reduced hemispheric lateralization.

  11. 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.

  12. Photodissociation of CH3CHO at 248 nm by time-resolved Fourier-transform infrared emission spectroscopy: Verification of roaming and triple fragmentation

    Science.gov (United States)

    Hung, Kai-Chan; Tsai, Po-Yu; Li, Hou-Kuan; Lin, King-Chuen

    2014-02-01

    By using time-resolved Fourier-transform infrared emission spectroscopy, the HCO fragment dissociated from acetaldehyde (CH3CHO) at 248 nm is found to partially decompose to H and CO. The fragment yields are enhanced by the Ar addition that facilitates the collision-induced internal conversion. The channels to CH2CO + H2 and CH3CO + H are not detected significantly. The rotational population distribution of CO, after removing the Ar collision effect, shows a bimodal feature comprising both low- and high-rotational (J) components, sharing a fraction of 19% and 81%, respectively, for the vibrational state v = 1. The low-J component is ascribed to both roaming pathway and triple fragmentation. They are determined to have a branching ratio of 0.06, respectively, relative to the whole v = 1 population. The CO roaming is accompanied by a highly vibrational population of CH4 that yields a vibrational bimodality.

  13. Interaction of Cm(III) and Am(III) with human serum transferrin studied by time-resolved laser fluorescence and EXAFS spectroscopy.

    Science.gov (United States)

    Bauer, Nicole; Fröhlich, Daniel R; Panak, Petra J

    2014-05-14

    The complexation of Cm(III) with human serum transferrin was investigated in a pH range from 3.5 to 11.0 using time-resolved laser fluorescence spectroscopy (TRLFS). At pH ≥ 7.4 Cm(III) is incorporated at the Fe(III) binding site of transferrin whereas at lower pH a partially bound Cm(III) transferrin species is formed. At physiological temperature (310 K) at pH 7.4, about 70% of the partially bound and 30% of the incorporated Cm(III) transferrin species are present in solution. The Cm(III) results obtained by TRLFS are in very good agreement with Am(III) EXAFS results, confirming the incorporation of Am(III) at the Fe(III) binding site at pH 8.5.

  14. Hollow plasmonic antennas for broadband SERS spectroscopy.

    Science.gov (United States)

    Messina, Gabriele C; Malerba, Mario; Zilio, Pierfrancesco; Miele, Ermanno; Dipalo, Michele; Ferrara, Lorenzo; De Angelis, Francesco

    2015-01-01

    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.

  15. Pulse laser photolysis of aqueous ozone in the microsecond range studied by time-resolved far-ultraviolet absorption spectroscopy.

    Science.gov (United States)

    Goto, Takeyoshi; Morisawa, Yusuke; Higashi, Noboru; Ikehata, Akifumi; Ozaki, Yukihiro

    2013-05-01

    Chemical dynamics of an ozone (O3) pulse-photolytic reaction in aqueous solutions were studied with pump-probe transient far-ultraviolet (FUV) absorption spectroscopy. With a nanosecond pulse laser of 266 nm as pump light, transient spectra of O3 aqueous solutions (78-480 μM, pH 2.5-11.3) were acquired in the time range from -50 to 50 μs in the wavelength region from 190 to 225 nm. The measured transient spectra were linearly decomposed into the molar absorption coefficients and the concentration-time profiles of constituted chemical components with a multivariate curve resolution method. From the dependences of the time-averaged concentrations for 20 μs of the constituted chemicals on the initial concentration of O3, it was found that the transient spectra involve the decomposition of O3 and the formation of hydrogen peroxide (H2O2) and a third component that is assigned to hydroxyl radical (OH) or perhydroxyl radical (HO2). Furthermore, the pH dependence of the time-averaged concentration of the third components indicates that HO2 is more probable than OH as the third component. The time-averaged concentration ratio of each chemical component to the initial O3 concentration depends on the pH conditions from -0.95 to -0.60 for O3, 0.98 to 1.2 for H2O2, 0.002 to 0.29 for OH, and 0.012 to 0.069 for HO2.

  16. 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.

  17. 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

  18. Measurements of plasma temperature and electron density in laser-induced copper plasma by time-resolved spectroscopy of neutral atom and ion emissions

    Indian Academy of Sciences (India)

    V K Unnikrishnan; Kamlesh Alti; V B Kartha; C Santhosh; G P Gupta; B M Suri

    2010-06-01

    Plasma produced by a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a copper solid sample in air at atmospheric pressure is studied spectroscopically. The temperature and electron density characterizing the plasma are measured by time-resolved spectroscopy of neutral atom and ion line emissions in the time window of 300–2000 ns. An echelle spectrograph coupled with a gated intensified charge coupled detector is used to record the plasma emissions. The temperature is obtained using the Boltzmann plot method and the electron density is determined using the Saha– Boltzmann equation method. Both parameters are studied as a function of delay time with respect to the onset of the laser pulse. The results are discussed. The time window where the plasma is optically thin and is also in local thermodynamic equilibrium (LTE), necessary for the laser-induced breakdown spectroscopy (LIBS) analysis of samples, is deduced from the temporal evolution of the intensity ratio of two Cu I lines. It is found to be 700–1000 ns.

  19. Element-specific characterization of transient electronic structure of solvated Fe(II) complexes with time-resolved soft X-ray absorption spectroscopy.

    Science.gov (United States)

    Hong, Kiryong; Cho, Hana; Schoenlein, Robert W; Kim, Tae Kyu; Huse, Nils

    2015-11-17

    Polypyridyl transition-metal complexes are an intriguing class of compounds due to the relatively facile chemical designs and variations in ligand-field strengths that allow for spin-state changes and hence electronic configurations in response to external perturbations such as pressure and light. Light-activated spin-conversion complexes have possible applications in a variety of molecular-based devices, and ultrafast excited-state evolution in these complexes is of fundamental interest for understanding of the origins of spin-state conversion in metal complexes. Knowledge of the interplay of structure and valence charge distributions is important to understand which degrees of freedom drive spin-conversion and which respond in a favorable (or unfavorable) manner. To track the response of the constituent components, various types of time-resolved X-ray probe methods have been utilized for a broad range of chemical and biological systems relevant to catalysis, solar energy conversions, and functional molecular devices. In particular, transient soft X-ray spectroscopy of solvated molecules can offer complementary information on the detailed electronic structures and valence charge distributions of photoinduced intermediate species: First-row transition-metal L-edges consist of 2p-3d transitions, which directly probe the unoccupied valence density of states and feature lifetime broadening in the range of 100 meV, making them sensitive spectral probes of metal-ligand interactions. In this Account, we present some of our recent progress in employing picosecond and femtosecond soft X-ray pulses from synchrotron sources to investigate element specific valence charge distributions and spin-state evolutions in Fe(II) polypyridyl complexes via core-level transitions. Our results on transient L-edge spectroscopy of Fe(II) complexes clearly show that the reduction in σ-donation is compensated by significant attenuation of π-backbonding upon spin-crossover. This underscores

  20. Noninvasive determination of absorption and reduced scattering coefficients of adult heads by time-resolved reflectance measurements for functional near infra-red spectroscopy.

    Science.gov (United States)

    Tanifuji, T; Wang, L

    2014-01-01

    Absorption and reduced scattering coefficients (μ(a) and μ'(s)) of adult heads have been noninvasively determined by time-resolved reflectance measurements. The finite difference time domain (FDTD) analysis was used to calculate time-resolved reflectance from realistic adult head models with brain grooves containing a non-scattering layer. In vivo time-resolved reflectances of human heads were measured by a system composed of a time-correlated single photon counter and a diode laser. By minimizing the objective functions that compare theoretical and experimental time resolved reflectances, μ(a) and μ'(s) of brain were determined. It became clear that time-resolved measurements have enough sensitivity to determine both μ(a) and μ'(s) for superficial tissues, gray matter and white matter, except μ(s) for white matter.

  1. Statistical Time-Resolved Spectroscopy: A higher fraction of short-period binaries for metal-rich F-type dwarfs in SDSS

    CERN Document Server

    Hettinger, T; Strader, J; Bickerton, S J; Beers, T C

    2015-01-01

    Stellar multiplicity lies at the heart of many problems in modern astrophysics, including the physics of star formation, the observational properties of unresolved stellar populations, and the rates of interacting binaries such as cataclysmic variables, X-ray binaries, and Type Ia supernovae. However, little is known about the stellar multiplicity of field stars in the Milky Way, in particular about the differences in the multiplicity characteristics between metal-rich disk stars and metal-poor halo stars. In this study we perform a statistical analysis of ~15,000 F-type dwarf stars in the Milky Way through time-resolved spectroscopy with the sub-exposures archived in the Sloan Digital Sky Survey. We obtain absolute radial velocity measurements through template cross-correlation of individual sub-exposures with temporal baselines varying from minutes to years. These sparsely sampled radial velocity curves are analyzed using Markov chain Monte Carlo techniques to constrain the very short-period binary fraction...

  2. Interaction of quinine sulfate with anionic micelles of sodium dodecylsulfate: A time-resolved fluorescence spectroscopy at different pH

    Science.gov (United States)

    Joshi, Sunita; Pant, Debi D.

    2015-09-01

    Photophysical behavior and rotational relaxation dynamics of quinine sulfate (QS) in anionic surfactant, sodium dodecylsulfate (SDS) at different pH have been studied using steady state and time resolved fluorescence spectroscopy. It has been observed that the cationic form of quinine sulfate (at pH 2) forms a fluorescent ion pair complex with the surfactant molecules at lower concentrations of surfactant. However, for higher concentrations of SDS, the probe molecules bind strongly with the micelles and reside at the water-micelle interface. At pH 7, QS is singly protonated in bulk aqueous solution. At lower concentrations of SDS aggregation between probe and surfactant molecules has been observed. However, for higher concentrations of SDS, an additional fluorescence peak corresponding to dicationic form of QS appears and this has been attributed to double protonation of the QS molecule in micellar solution. At pH 7, in the presence of SDS micelles, the photophysical properties of QS showed substantial changes compared to that in the bulk water solution. At pH 12, an increase in fluorescence intensity and lifetime has been observed and this has been attributed to the increase in radiative rate due to the incorporation of QS at the micelle-water interface. The local pH at micellar surface has been found different from the pH of bulk solution.

  3. In vivo validation of a bimodal technique combining time-resolved fluorescence spectroscopy and ultrasonic backscatter microscopy for diagnosis of oral carcinoma

    Science.gov (United States)

    Sun, Yang; Xie, Hongtao; Liu, Jing; Lam, Matthew; Chaudhari, Abhijit J.; Zhou, Feifei; Bec, Julien; Yankelevich, Diego R.; Dobbie, Allison; Tinling, Steven L.; Gandour-Edwards, Regina F.; Monsky, Wayne L.; Gregory Farwell, D.; Marcu, Laura

    2012-11-01

    Tissue diagnostic features generated by a bimodal technique integrating scanning time-resolved fluorescence spectroscopy (TRFS) and ultrasonic backscatter microscopy (UBM) are investigated in an in vivo hamster oral carcinoma model. Tissue fluorescence is excited by a pulsed nitrogen laser and spectrally and temporally resolved using a set of filters/dichroic mirrors and a fast digitizer, respectively. A 41-MHz focused transducer (37-μm axial, 65-μm lateral resolution) is used for UBM scanning. Representative lesions of the different stages of carcinogenesis show that fluorescence characteristics complement ultrasonic features, and both correlate with histological findings. These results demonstrate that TRFS-UBM provide a wealth of co-registered, complementary data concerning tissue composition and structure as it relates to disease status. The direct co-registration of the TRFS data (sensitive to surface molecular changes) with the UBM data (sensitive to cross-sectional structural changes and depth of tumor invasion) is expected to play an important role in pre-operative diagnosis and intra-operative determination of tumor margins.

  4. Time-resolved infrared diode laser spectroscopy of the ν1 (C O stretch) band of the CoCO radical

    Science.gov (United States)

    Ikeda, Seiki; Hikida, Toshihide; Tanaka, Takehiko; Tanaka, Keiichi

    2008-02-01

    Infrared spectrum of the cobalt carbonyl radical CoCO produced by the 193 nm excimer laser photolysis of cobalt tricarbonyl nitrosyl Co(CO) 3NO was observed by time-resolved diode laser spectroscopy. More than 600 lines were identified as belonging to the ν1 (C-O stretch) fundamental band, consisting of the Ω=5/2 and 3/2 subbands, and the associated hot bands 112, 101211, 101311, and 101222. The 2Δi electronic ground state of CoCO was experimentally confirmed. The ν1 band origins are 1974.172582(93) cm -1 and 1973.53178(14) cm -1 for the Ω=5/2 and 3/2 subbands, respectively. The rotational constant in the ground state was determined as B0=4427.146(50) MHz. The centrifugal distortion constant D0=1.1243(68) kHz was obtained for the Ω=5/2 substate of the ground state. The equilibrium rotational constant Be=4435.44(14) MHz was derived, together with the vibration-rotation interaction constants.

  5. Local heterogeneity for a Eu3+-doped glass evidenced by time-resolved fluorescence spectroscopy coupled to scanning near-field optical microscopy

    International Nuclear Information System (INIS)

    Time-resolved fluorescence spectroscopy (TRFS) was applied to an aluminate glass sample doped with Eu3+ cation as a fluorescent probe of the chemical environment and local symmetry. Conventional far-field experiments revealed the presence of two different phases: an amorphous phase featured by a highly disordered environment surrounding the Eu3+ cation and a more ordered polycrystalline phase that exhibits a significant increase in the Eu3+ fluorescence decay time compared to that of the amorphous phase. Near-field fluorescence spectra and decay kinetics were recorded in the frontier region between the two phases using a home-built scanning near-field optical microscope. SNOM-TRFS experiments confirmed the presence of local heterogeneities in this part of the glass at a sub-micrometric spatial scale. Polycrystalline sites featured an important shear-force interaction with the probing fiber optic tip, a longer fluorescence decay time, and a higher Stark splitting of the 5D0 → 7FJ (J = 1-4) electronic transitions of the Eu3+ cations. (authors)

  6. ESIPT and photodissociation of 3-hydroxychromone in solution: photoinduced processes studied by static and time-resolved UV/Vis, fluorescence, and IR spectroscopy.

    Science.gov (United States)

    Chevalier, Katharina; Grün, Anneken; Stamm, Anke; Schmitt, Yvonne; Gerhards, Markus; Diller, Rolf

    2013-11-01

    The spectral properties of fluorescence sensors such as 3-hydroxychromone (3-HC) and its derivatives are sensitive to interaction with the surrounding medium as well as to substitution. 3-HC is a prototype system for other derivatives because it is the basic unit of all flavonoides undergoing ESIPT and is not perturbed by a substituent. In this study, the elementary processes and intermediate states in the photocycle of 3-HC as well as its anion were identified and characterized by the use of static and femtosecond time-resolved spectroscopy in different solvents (methylcyclohexane, acetonitrile, ethanol, and water at different pH). Electronic absorption and fluorescence spectra and lifetimes of the intermediate states were obtained for the normal, tautomer and anionic excited state, while mid-IR vibrational spectra yielded structural information on ground and excited states of 3-HC. A high sensitivity on hydrogen-bonding perturbations was observed, leading to photoinduced anion formation in water, while in organic solvents, different processes are suggested, including slow picosecond ESIPT and contribution of the trans-structure excited state or a different stable solvation state with different direction of OH. The formation of the latter could be favored by the lack of a substituent increasing contact points for specific solute-solvent interactions at the hydroxyl group compared to substituted derivatives. The effect of substituents has to be considered for the design of future fluorescence sensors based on 3-HC. PMID:24083478

  7. Temperature dependent kinetics of the OH/HO{sub 2}/O{sub 3} chain reaction by time-resolved IR laser absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nizkorodov, S.A.; Harper, W.W.; Blackmon, B.W.; Nesbitt, D.J.

    2000-05-04

    This paper presents an extensive temperature dependent kinetic study of the catalytic HO{sub x} ozone cycle, (1) OH + O{sub 3} {r_arrow} HO{sub 2} + O{sub 2} and (2) HO{sub 2} + O{sub 3} {r_arrow} OH + 2 O{sub 2}, based on time-resolved, Doppler limited direct absorption spectroscopy of OH with a single mode ({Delta}{nu} = 0.0001 cm{sup {minus}1}) high-resolution infrared laser. The sum of the two chain rate constants, k{sub 1} + k{sub 2}, is measured over the 190--315 K temperature range and can be accurately described by an Arrhenius-type expression: k{sub 1} + k{sub 2} (cm{sup 3}/s) = 2.26(40) x 10{sup {minus}12} exp[{minus}976(50)/T]. These results are in excellent agreement with studies by Ravishankara et al. and Smith et al. but are significantly higher than the values currently accepted for atmospheric modeling. In addition, these studies also reflect the first such rate measurements to access the 190--230 K temperature range relevant to kinetic modeling of ozone chain loss in the lower stratosphere.

  8. Femtosecond time-resolved transient absorption spectroscopy of CH3NH3PbI3 perovskite films: evidence for passivation effect of PbI2.

    Science.gov (United States)

    Wang, Lili; McCleese, Christopher; Kovalsky, Anton; Zhao, Yixin; Burda, Clemens

    2014-09-01

    CH3NH3PbI3 perovskite layered films deposited on substrates with and without a titania support structure have been prepared and studied using time-resolved femtosecond transient absorption (fs-TA) spectroscopy in the visible light range (450-800 nm). The electron injection dynamics from the photoexcited perovskite layers to the neighboring film structures could be directly monitored via the transient bleaching dynamics of the perovskite at ∼750 nm and thus systematically studied as a function of the layer-by-layer architecture. In addition, for the first time we could spectrally distinguish transient bleaching at ∼750 nm from laser-induced fluorescence that occurs red-shifted at ∼780 nm. We show that an additional bleach feature at ∼510 nm appears when PbI2 is present in the perovskite film. The amplitudes of the PbI2 and perovskite TA peaks were compared to estimate relative amounts of PbI2 in the samples. Kinetic analysis reveals that perovskite films with less PbI2 show faster relaxation rates than those containing more PbI2. These fast dynamics are attributed to charge carrier trapping at perovskite grain boundaries, and the slower dynamics in samples containing PbI2 are due to a passivation effect, in line with other recently reported work.

  9. Femtosecond time-resolved X-ray absorption spectroscopy of liquid using a hard X-ray free electron laser in a dual-beam dispersive detection method.

    Science.gov (United States)

    Obara, Yuki; Katayama, Tetsuo; Ogi, Yoshihiro; Suzuki, Takayuki; Kurahashi, Naoya; Karashima, Shutaro; Chiba, Yuhei; Isokawa, Yusuke; Togashi, Tadashi; Inubushi, Yuichi; Yabashi, Makina; Suzuki, Toshinori; Misawa, Kazuhiko

    2014-01-13

    We present femtosecond time-resolved X-ray absorption spectroscopy of aqueous solution using a hard x-ray free electron laser (SACLA) and a synchronized Ti:sapphire laser. The instrumental response time is 200 fs, and the repetition rate of measurement is 10 Hz. A cylindrical liquid beam 100 μm in diameter of aqueous ammonium iron(III) oxalate solution is photoexcited at 400 nm, and the transient X-ray absorption spectra are measured in the K-edge region of iron, 7.10 - 7.26 keV, using a dual X-ray beam dispersive detection method. Each of the dual beams has the pulse energy of 1.4 μJ, and pump-induced absorbance change on the order of 10(-3) is successfully detected. The photoexcited iron complex exhibits a red shifted iron K-edge with the appearance time constant of 260 fs. The X-ray absorption difference spectra, with and without the pump pulses, are independent of time delay after 1.5 ps up to 100 ps, indicating that the photoexcited species is long-lived.

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

    Science.gov (United States)

    Winghart, Marc-Oliver; Yang, Ji-Ping; Vonderach, Matthias; Unterreiner, Andreas-Neil; Huang, Dao-Ling; Wang, Lai-Sheng; Kruppa, Sebastian; Riehn, Christoph; Kappes, Manfred M.

    2016-02-01

    Time-resolved pump-probe photoelectron spectroscopy has been used to study the relaxation dynamics of gaseous [Pt2(μ-P2O5H2)4 + 2H]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 1A2u state and concomitant rise in population of the triplet 3A2u 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 1A2u state takes only a few picoseconds, ESETD from the triplet 3A2u 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. [Pt2(μ-P2O5H2)4 + 2H]2- is the first example of a photoexcited multianion for which ESETD has been observed following ISC.

  11. Photolysis of n-butyl nitrite and isoamyl nitrite at 355 nm: A time-resolved Fourier transform infrared emission spectroscopy and ab initio study

    CERN Document Server

    Ji, Min; Zhang, Qun; Chen, Yang

    2009-01-01

    We report on the photodissociation dynamics study of n-butyl nitrite (n-C_4H_9ONO) and isoamyl nitrite ((CH_3)_2C_3H_5ONO) by means of time-resolved Fourier transform infrared (TR-FTIR) emission spectroscopy. The obtained TR-FTIR emission spectra of the nascent NO fragments produced in the 355-nm laser photolysis of the two alkyl nitrite species showed an almost identical rotational temperature and vibrational distributions of NO. In addition, a close resemblance between the two species was also found in the measured temporal profiles of the IR emission of NO and the recorded UV absorption spectra. The experimental results are consistent with our ab initio calculations using the time-dependent density functional theory at the B3LYP/6-311G(d,p) level, which indicate that the substitution of one of the two {gamma}-H atoms in n-C_4H_9ONO with a methyl group to form (CH_3)_2C_3H_5ONO has only a minor effect on the photodissociation dynamics of the two molecules.

  12. 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.

  13. 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

    2014-11-01

    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.

  14. Charge dynamics at heterojunctions for PbS/ZnO colloidal quantum dot solar cells probed with time-resolved surface photovoltage spectroscopy

    Science.gov (United States)

    Spencer, B. F.; Leontiadou, M. A.; Clark, P. C. J.; Williamson, A. I.; Silly, M. G.; Sirotti, F.; Fairclough, S. M.; Tsang, S. C. E.; Neo, D. C. J.; Assender, H. E.; Watt, A. A. R.; Flavell, W. R.

    2016-02-01

    Time-resolved laser-pump X-ray-photoemission-probe spectroscopy of a ZnO ( 10 1 ¯ 0 ) substrate with and without PbS quantum dots (QDs) chemically linked to the surface is performed, using laser photon energies resonant with and below the band gap energy of the substrate (λ = 372 and 640 nm, hν = 3.33 and 1.94 eV). Charge injection from the photoexcited QDs to ZnO is demonstrated through the change in the surface photovoltage of the ZnO substrate observed when the heterojunction is illuminated with 1.94 eV radiation. The measured carrier dynamics are limited by the persistent photoconductivity of ZnO, giving dark carrier lifetimes of the order of 200 μs in a depletion layer at the interface. The chemical specificity of soft X-rays is used to separately measure the charge dynamics in the quantum dots and the substrate, yielding evidence that the depletion region at the interface extends into the PbS QD layer.

  15. Relationship Between Texture Sensory Profiles and Optical Properties Measured by Time-Resolved Reflectance Spectroscopy During Post-Storage Shelf Life of ‘Braeburn’ Apples

    Directory of Open Access Journals (Sweden)

    Rizzolo Anna

    2014-09-01

    Full Text Available ‘Braeburn’ apples from three harvests after 6-month storage in controlled atmosphere were measured at 670 nm by time-resolved reflectance spectroscopy (TRS, ranked on decreasing μa670 (increasing maturity, classified as less (LeM, medium and more mature (MoM, randomised into three batches per harvest and analysed after 1, 8 and 14 days of shelf life. LeM and MoM apples were measured in the 630-900 nm range by TRS, and analysed for sensory profile (firm, crispy, juicy, mealy and pulp mechanical characteristics (firmness, stiffness, energy-to-rupture. All data were processed by Principal Component Analysis (PCA. According to sensory intensity scores, fruits were either divided into five classes (very low – VL; low – L; medium – M; high – H; very high – VH separately for every attribute, or clustered into four groups, each one representing a specific sensory profile. The absorption spectra showed a maximum at 670 nm (chlorophyll-a and μa670 was higher in the VH class for firm, crispy and juicy and in the VL and L classes for mealy. The scattering spectra had a decreasing trend with the wavelength increase, and μs’ values were lower in the VH class for firm and crispy, and higher in the VH class for mealy and in the VL ones for juicy. PCA underlined that μs’ values were negatively related to firmness and μa670, and that μa690, μa730, μa830, μa850 and μa900 were opposed to mealiness. PC scores differed among the four sensory profiles and increased from VL to VH classes for firmness, crispiness and juiciness and from VH to VL classes for mealiness.

  16. Charge-transfer-to-solvent reactions from I- to water, methanol, and ethanol studied by time-resolved photoelectron spectroscopy of liquids

    Science.gov (United States)

    Okuyama, Haruki; Suzuki, Yoshi-Ichi; Karashima, Shutaro; Suzuki, Toshinori

    2016-08-01

    The charge-transfer-to-solvent (CTTS) reactions from iodide (I-) to H2O, D2O, methanol, and ethanol were studied by time-resolved photoelectron spectroscopy of liquid microjets using a magnetic bottle time-of-flight spectrometer with variable pass energy. Photoexcited iodide dissociates into a weak complex (a contact pair) of a solvated electron and an iodine atom in similar reaction times, 0.3 ps in H2O and D2O and 0.5 ps in methanol and ethanol, which are much shorter than their dielectric relaxation times. The results indicate that solvated electrons are formed with minimal solvent reorganization in the long-range solvent polarization field created for I-. The photoelectron spectra for CTTS in H2O and D2O—measured with higher accuracy than in our previous study [Y. I. Suzuki et al., Chem. Sci. 2, 1094 (2011)]—indicate that internal conversion yields from the photoexcited I-* (CTTS) state are less than 10%, while alcohols provide 2-3 times greater yields of internal conversion from I-*. The overall geminate recombination yields are found to be in the order of H2O > D2O > methanol > ethanol, which is opposite to the order of the mutual diffusion rates of an iodine atom and a solvated electron. This result is consistent with the transition state theory for an adiabatic outer-sphere electron transfer process, which predicts that the recombination reaction rate has a pre-exponential factor inversely proportional to a longitudinal solvent relaxation time.

  17. Subpicosecond oxygen trapping in the heme pocket of the oxygen sensor FixL observed by time-resolved resonance Raman spectroscopy.

    Science.gov (United States)

    Kruglik, Sergei G; Jasaitis, Audrius; Hola, Klara; Yamashita, Taku; Liebl, Ursula; Martin, Jean-Louis; Vos, Marten H

    2007-05-01

    Dissociation of oxygen from the heme domain of the bacterial oxygen sensor protein FixL constitutes the first step in hypoxia-induced signaling. In the present study, the photodissociation of the heme-O2 bond was used to synchronize this event, and time-resolved resonance Raman (TR(3)) spectroscopy with subpicosecond time resolution was implemented to characterize the heme configuration of the primary photoproduct. TR(3) measurements on heme-oxycomplexes are highly challenging and have not yet been reported. Whereas in all other known six-coordinated heme protein complexes with diatomic ligands, including the oxymyoglobin reported here, heme iron out-of-plane motion (doming) occurs faster than 1 ps after iron-ligand bond breaking; surprisingly, no sizeable doming is observed in the oxycomplex of the Bradyrhizobium japonicum FixL sensor domain (FixLH). This assessment is deduced from the absence of the iron-histidine band around 217 cm(-1) as early as 0.5 ps. We suggest that efficient ultrafast oxygen rebinding to the heme occurs on the femtosecond time scale, thus hindering heme doming. Comparing WT oxy-FixLH, mutant proteins FixLH-R220H and FixLH-R220Q, the respective carbonmonoxy-complexes, and oxymyoglobin, we show that a hydrogen bond of the terminal oxygen atom with the residue in position 220 is responsible for the observed behavior; in WT FixL this residue is arginine, crucially implicated in signal transmission. We propose that the rigid O2 configuration imposed by this residue, in combination with the hydrophobic and constrained properties of the distal cavity, keep dissociated oxygen in place. These results uncover the origin of the "oxygen cage" properties of this oxygen sensor protein.

  18. Sorption of Eu(III)/Cm(III) on Ca-montmorillonite and Na-illite. Part 1: Batch sorption and time-resolved laser fluorescence spectroscopy experiments

    Science.gov (United States)

    Rabung, Th.; Pierret, M. C.; Bauer, A.; Geckeis, H.; Bradbury, M. H.; Baeyens, B.

    2005-12-01

    Sorption of Cm(III) and Eu(III) at trace concentrations onto Ca-montmorillonite (SWy-1) and Na-illite (Illite du Puy) has been studied under anaerobic conditions by batch sorption experiments and time-resolved laser fluorescence spectroscopy (TRLFS). Comparison of the results from spectroscopic and batch sorption experiments with Cm and Eu indicates the existence of outer-sphere complexes at pH 5 for both clay minerals. Five H 2O/OH - molecules remain in the first metal ion coordination sphere of the sorbed Eu/Cm. Measured fluorescence lifetimes of sorbed Eu/Cm and peak deconvolution of Cm-spectra are consistent with the formation of surface complexes of the form ≡S-O-Eu/Cm(OH) x(2-x)(H 2O) 5-x. At pH ≥ 12 Cm becomes incorporated into a surface precipitate at the Ca-montmorillonite surface presumably composed of Ca(OH) 2 or calcium silicate hydrate. A dramatic shift of the fluorescence emission band by more than 20 nm and a clear increase in the fluorescence lifetime suggests the almost complete displacement of coordinated H 2O and OH -. The pH dependent Eu sorption data obtained in batch experiments are consistent with spectroscopic data on Eu and Cm within experimental uncertainties thus demonstrating the validity of Eu as a homologue for trivalent actinides. Parameterization of a two-site protolysis nonelectrostatic surface complexation and cation exchange model using the batch sorption data and spectroscopic results is discussed in Part 2 of this work.

  19. Stark-assisted population control of coherent CS(2) 4f and 5p Rydberg wave packets studied by femtosecond time-resolved photoelectron spectroscopy.

    Science.gov (United States)

    Knappenberger, Kenneth L; Lerch, Eliza-Beth W; Wen, Patrick; Leone, Stephen R

    2007-09-28

    A two-color (3+1(')) pump-probe scheme is employed to investigate Rydberg wave packet dynamics in carbon disulfide (CS(2) (*)). The state superpositions are created within the 4f and 5p Rydberg manifolds by three photons of the 400 nm pump pulse, and their temporal evolution is monitored with femtosecond time-resolved photoelectron spectroscopy using an 800 nm ionizing probe pulse. The coherent behavior of the non-stationary superpositions are observed through wavepacket revivals upon ionization to either the upper (12) or lower (32) spin-orbit components of CS(2) (+). The results show clearly that the composition of the wavepacket can be efficiently controlled by the power density of the excitation pulse over a range from 500 GWcm(2) to 10 TWcm(2). The results are consistent with the anticipated ac-Stark shift for 400 nm light and demonstrate an effective method for population control in molecular systems. Moreover, it is shown that Rydberg wavepackets can be formed in CS(2) with excitation power densities up to 10 TWcm(2) without significant fragmentation. The exponential 1e population decay (T(1)) of specific excited Rydberg states are recovered by analysis of the coherent part of the signal. The dissociation lifetimes of these states are typically 1.5 ps. However, a region exhibiting a more rapid decay ( approximately 800 fs) is observed for states residing in the energy range of 74 450-74 550 cm(-1), suggestive of an enhanced surface crossing in this region. PMID:17902914

  20. Photoionization-induced π↔ H site switching dynamics in phenol(+)-Rg (Rg = Ar, Kr) dimers probed by picosecond time-resolved infrared spectroscopy.

    Science.gov (United States)

    Miyazaki, Mitsuhiko; Sakata, Yuri; Schütz, Markus; Dopfer, Otto; Fujii, Masaaki

    2016-09-21

    The ionization-induced π↔ H site switching reaction in phenol(+)-Rg (PhOH(+)-Rg) dimers with Rg = Ar and Kr is traced in real time by picosecond time-resolved infrared (ps-TRIR) spectroscopy. The ps-TRIR spectra show the prompt appearance of the non-vanishing free OH stretching band upon resonant photoionization of the π-bound neutral clusters, and the delayed appearance of the hydrogen-bonded (H-bonded) OH stretching band. This result directly proves that the Rg ligand switches from the π-bound site on the aromatic ring to the H-bonded site at the OH group by ionization. The subsequent H →π back reaction converges the dimer to a π↔ H equilibrium. This result is in sharp contrast to the single-step π→ H forward reaction in the PhOH(+)-Ar2 trimer with 100% yield. The reaction mechanism and yield strongly depend on intracluster vibrational energy redistribution. A classical rate equation analysis for the time evolutions of the band intensities of the two vibrations results in similar estimates for the time constants of the π→ H forward reaction of τ+ = 122 and 73 ps and the H →π back reaction of τ- = 155 and 188 ps for PhOH(+)-Ar and PhOH(+)-Kr, respectively. The one order of magnitude slower time constant in comparison to the PhOH(+)-Ar2 trimer (τ+ = 7 ps) is attributed to the decrease in density of states due to the absence of the second Ar in the dimer. The similar time constants for both PhOH(+)-Rg dimers are well rationalized by a classical interpretation based on the comparable potential energy surfaces, reaction pathways, and density of states arising from their similar intermolecular vibrational frequencies.

  1. Subpicosecond oxygen trapping in the heme pocket of the oxygen sensor FixL observed by time-resolved resonance Raman spectroscopy.

    Science.gov (United States)

    Kruglik, Sergei G; Jasaitis, Audrius; Hola, Klara; Yamashita, Taku; Liebl, Ursula; Martin, Jean-Louis; Vos, Marten H

    2007-05-01

    Dissociation of oxygen from the heme domain of the bacterial oxygen sensor protein FixL constitutes the first step in hypoxia-induced signaling. In the present study, the photodissociation of the heme-O2 bond was used to synchronize this event, and time-resolved resonance Raman (TR(3)) spectroscopy with subpicosecond time resolution was implemented to characterize the heme configuration of the primary photoproduct. TR(3) measurements on heme-oxycomplexes are highly challenging and have not yet been reported. Whereas in all other known six-coordinated heme protein complexes with diatomic ligands, including the oxymyoglobin reported here, heme iron out-of-plane motion (doming) occurs faster than 1 ps after iron-ligand bond breaking; surprisingly, no sizeable doming is observed in the oxycomplex of the Bradyrhizobium japonicum FixL sensor domain (FixLH). This assessment is deduced from the absence of the iron-histidine band around 217 cm(-1) as early as 0.5 ps. We suggest that efficient ultrafast oxygen rebinding to the heme occurs on the femtosecond time scale, thus hindering heme doming. Comparing WT oxy-FixLH, mutant proteins FixLH-R220H and FixLH-R220Q, the respective carbonmonoxy-complexes, and oxymyoglobin, we show that a hydrogen bond of the terminal oxygen atom with the residue in position 220 is responsible for the observed behavior; in WT FixL this residue is arginine, crucially implicated in signal transmission. We propose that the rigid O2 configuration imposed by this residue, in combination with the hydrophobic and constrained properties of the distal cavity, keep dissociated oxygen in place. These results uncover the origin of the "oxygen cage" properties of this oxygen sensor protein. PMID:17446273

  2. NI-49SMART SUCKER: NEXT GENERATION SMART SURGICAL TOOL FOR INTRAOPERATIVE BRAIN TUMOR RESECTION USING TIME RESOLVED LASER INDUCED FLUORESCENCE SPECTROSCOPY

    Science.gov (United States)

    Kittle, David S.; Butte, Pramod V.; Vasefi, Fartash; Patil, Chirag G.; Black, Keith

    2014-01-01

    Primary brain tumors are highly lethal tumors where surgical resection is the primary treatment of choice. It has been shown that survival rate is directly related to the extent of tumor resection. In order to aid the surgeon in achieving near-complete resection, novel technologies are required. Time-resolved laser induced fluorescence spectroscopy (TRLIFS) promises to be one such technology, where the tissue is excited using an ultra-short laser and the corresponding fluorescence intensity decay is captured. Based on the fluorescence spectrum and the decay characteristics at various color bands from TRLIFS, differentiation of tumor from the normal brain tissue is possible in real-time. We built a portable TRLIFS system using custom optics and hardware (laser excitation: 355nm, 400ps pulse width, 5 uJ/pulse; PMT detector: Photek, rise time 80 picoseconds; digitizer: 7 Giga-samples per second) which is capable of providing the results in real time (every 50 milliseconds). We have designed a custom probe which is attached to a Roton sucker "Smart sucker" to collect the data during surgical resection from patients at Cedars-Sinai Medical Center. The histopathological diagnosis of the site under study with TRLIFS is confirmed with a biopsy and H-E staining. We will present our preliminary data from human brain tumor samples collected in-vivo. Our preliminary study shows that TRLIFS is capable of classifying low grade tumors with high sensitivity and specificity. This study will also demonstrate the potential of using the TRLIFS system to enhance the surgical instrumentation, aiding surgeons in near-complete excision of tumors and bringing these instruments into the next generation of smart tools.

  3. 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.

  4. Time-resolved studies

    International Nuclear Information System (INIS)

    When new or more powerful probes become available that offer both shorter data-collection times and the opportunity to apply innovative approaches to established techniques, it is natural that investigators consider the feasibility of exploring the kinetics of time-evolving systems. This stimulating area of research not only can lead to insights into the metastable or excited states that a system may populate on its way to a ground state, but can also lead to a better understanding of that final state. Synchrotron radiation, with its unique properties, offers just such a tool to extend X-ray measurements from the static to the time-resolved regime. The most straight-forward application of synchrotron radiation to the study of transient phenomena is directly through the possibility of decreased data-collection times via the enormous increase in flux over that of a laboratory X-ray system. Even further increases in intensity can be obtained through the use of novel X-ray optical devices. Widebandpass monochromators, e.g., that utilize the continuous spectral distribution of synchrotron radiation, can increase flux on the sample several orders of magnitude over conventional X-ray optical systems thereby allowing a further shortening of the data-collection time. Another approach that uses the continuous spectral nature of synchrotron radiation to decrease data-collection times is the open-quote parallel data collectionclose quotes method. Using this technique, intensities as a function of X-ray energy are recorded simultaneously for all energies rather than sequentially recording data at each energy, allowing for a dramatic decrease in the data-collection time

  5. Sulfate complexation of trivalent lanthanides probed by nano-electro-spray mass spectrometry and time-resolved laser-induced fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Full text of publication follows: Sulfate complexation of lanthanides is of great interest to predict the speciation of radionuclides in natural environments. In the present work, the stability constants of sulfate complexes of trivalent lanthanide ions were investigated by two speciation techniques: nano-Electro-Spray Ionisation Mass Spectrometry (nano-ESI-MS) and Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS). TRLFS was used to study the Eu(III) speciation in the ionic conditions 0.02-0.05 mol/l H+ (H2SO4 / HClO4) and 0.4-2.0 mol/l Na+ (Na2SO4 / NaClO4). The data were interpreted with the EuSO4+ and Eu(SO4)2- species. To calculate the effect of the ionic medium on the complexation constants, all the major ions were taken into account through several ion-pair parameters, ε, of the Specific ion Interaction Theory (SIT). Several ε values were estimated by analogy using linear correlations, while ε(Eu3+, SO42-) was fitted to experimental data, since, to date, SIT coefficients between multicharged species are not reported. The formation constants proposed here confirm some of those previously measured for Ln(III) and An(III) by various experimental techniques. The TRLFS lifetimes measured for EuSO4+ and Eu(SO4)2- were found consistent with the replacement of one H2O molecule in the first coordination sphere of Eu3+ for each added SO42- ligand, suggesting monodentate SO42- coordination. Moreover, these results and equilibrium thermodynamics do not give credit that TRLFS and other spectroscopic techniques would provide stability constants of only inner sphere complexes while they are in equilibrium with possible outer sphere complexes. Besides, numerous La(III) species were observed in a gaseous phase by nano-ESI-MS from the analysis of HNO3 / H2SO4 aqueous solutions with low ionic strength. The mass spectra were interpreted according to the expected formation of LaSO4+(aq). Its formation constant was measured and compared well with the TRLFS results

  6. Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources

    Energy Technology Data Exchange (ETDEWEB)

    Shavorskiy, Andrey; Slaughter, Daniel S.; Zegkinoglou, Ioannis; Rude, Bruce S.; Bluhm, Hendrik [Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Neppl, Stefan; Cryan, James P.; Siefermann, Katrin R.; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P.; Fraund, Matthew W.; Khurmi, Champak; Wright, Travis W.; Schoenlein, Robert W.; Gessner, Oliver, E-mail: ogessner@lbl.gov [Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Hertlein, Marcus P.; Tyliszczak, Tolek [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Huse, Nils [Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Physics Department, University of Hamburg and Max-Planck Institute for Structure and Dynamics of Matter, 22761 Hamburg (Germany); and others

    2014-09-15

    An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ∼0.1 mm spatial resolution and ∼150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E{sub p} = 150 eV and an electron kinetic energy range KE = 503–508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ∼9 ns at a pass energy of 50 eV and ∼1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular

  7. Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources.

    Science.gov (United States)

    Shavorskiy, Andrey; Neppl, Stefan; Slaughter, Daniel S; Cryan, James P; Siefermann, Katrin R; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P; Zegkinoglou, Ioannis; Fraund, Matthew W; Khurmi, Champak; Hertlein, Marcus P; Wright, Travis W; Huse, Nils; Schoenlein, Robert W; Tyliszczak, Tolek; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A; Rude, Bruce S; Ölsner, Andreas; Mähl, Sven; Bluhm, Hendrik; Gessner, Oliver

    2014-09-01

    An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ~9 ns at a pass energy of 50 eV and ~1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with

  8. Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources.

    Science.gov (United States)

    Shavorskiy, Andrey; Neppl, Stefan; Slaughter, Daniel S; Cryan, James P; Siefermann, Katrin R; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P; Zegkinoglou, Ioannis; Fraund, Matthew W; Khurmi, Champak; Hertlein, Marcus P; Wright, Travis W; Huse, Nils; Schoenlein, Robert W; Tyliszczak, Tolek; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A; Rude, Bruce S; Ölsner, Andreas; Mähl, Sven; Bluhm, Hendrik; Gessner, Oliver

    2014-09-01

    An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ~9 ns at a pass energy of 50 eV and ~1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with

  9. 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 to t...

  10. 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.

  11. Strategies for Complex Mixture Analysis in Broadband Microwave Spectroscopy.

    Science.gov (United States)

    Steber, Amanda L.; Neill, Justin L.; Muckle, Matthew T.; Pate, Brooks H.; Plusquellic, D. F.; Lattanzi, V.; Spezzano, S.; McCarthy, M. C.

    2010-06-01

    Broadband microwave spectra often contain overlapping spectra from a large number of species in the sample mixture, whether in the study of conformational isomers, molecular complexes, reaction products from reactive molecular sources (e.g., electrical discharge), or analysis of chemical mixtures. In these experiments, the identification of individual spectra in the full spectrum through pattern recognition becomes difficult when there is a high density of transitions. Strategies for extracting individual spectra from broadband measurements are discussed. Two approaches for microwave-microwave double resonance spectroscopy have been evaluated. One uses a transition-by-transition screening in a narrowband cavity spectrometer to identify an unknown spectrum and has a time advantage from the increased sensitivity of cavity spectroscopy. The second double-resonance approach uses a broadband spectral editing approach that gives a multiplex advantage in the detection. Both of these experimental techniques are combined with computer-aided assignment algorithms to make the spectral assignment in a minimum of double-resonance observations. The performance of spectral analysis solely using computer-aided assignment is also evaluated. The potential for fully automated spectral decomposition of the broadband spectrum of a complex mixture will be described.

  12. 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. PMID:26698997

  13. "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.

  14. Frequency Comb Assisted Broadband Precision Spectroscopy with Cascaded Diode Lasers

    CERN Document Server

    Liu, Junqiu; Pfeiffer, Martin H P; Kordts, Arne; Kamel, Ayman N; Guo, Hairun; Geiselmann, Michael; Kippenberg, Tobias J

    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, which allows extending the measurement bandwidth to 37.4 THz (1355 to 1630 nm) at MHz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy and in particular it enables to characterize the dispersion of integrated microresonators up to the fourth order.

  15. Structure of fenchone by broadband rotational spectroscopy.

    Science.gov (United States)

    Loru, Donatella; Bermúdez, Miguel A; Sanz, M Eugenia

    2016-08-21

    The bicyclic terpenoid fenchone (C10H16O, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one) has been investigated by chirped pulse Fourier transform microwave spectroscopy in the 2-8 GHz frequency region. The parent species and all heavy atom isotopologues have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and effective (r0) structures of fenchone. Calculations at the B3LYP, M06-2X, and MP2 levels of theory with different basis sets were carried out to check their performance against experimental results. The structure of fenchone has been compared with those of norbornane (bicyclo[2.2.1]heptane) and the norbornane derivatives camphor (1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) and camphene (3,3-dimethyl-2-methylenebicyclo[2.2.1]heptane), both with substituents at C2. The structure of fenchone is remarkably similar to those of camphor and camphene. Comparison with camphor allows identification of changes in ∠CCC angles due to the different position of the methyl groups. All norbornane derivatives display similar structural changes with respect to norbornane. These changes mainly affect the bond lengths and angles of the six-membered rings, indicating that the substituent at C2 drives structural adjustments to minimise ring strain after its introduction. PMID:27544109

  16. Structure of fenchone by broadband rotational spectroscopy

    Science.gov (United States)

    Loru, Donatella; Bermúdez, Miguel A.; Sanz, M. Eugenia

    2016-08-01

    The bicyclic terpenoid fenchone (C10H16O, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one) has been investigated by chirped pulse Fourier transform microwave spectroscopy in the 2-8 GHz frequency region. The parent species and all heavy atom isotopologues have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and effective (r0) structures of fenchone. Calculations at the B3LYP, M06-2X, and MP2 levels of theory with different basis sets were carried out to check their performance against experimental results. The structure of fenchone has been compared with those of norbornane (bicyclo[2.2.1]heptane) and the norbornane derivatives camphor (1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) and camphene (3,3-dimethyl-2-methylenebicyclo[2.2.1]heptane), both with substituents at C2. The structure of fenchone is remarkably similar to those of camphor and camphene. Comparison with camphor allows identification of changes in ∠CCC angles due to the different position of the methyl groups. All norbornane derivatives display similar structural changes with respect to norbornane. These changes mainly affect the bond lengths and angles of the six-membered rings, indicating that the substituent at C2 drives structural adjustments to minimise ring strain after its introduction.

  17. The open, the closed, and the empty: time-resolved fluorescence spectroscopy and computational analysis of RC-LH1 complexes from Rhodopseudomonas palustris.

    Science.gov (United States)

    Beyer, Sebastian R; Müller, Lars; Southall, June; Cogdell, Richard J; Ullmann, G Matthias; Köhler, Jürgen

    2015-01-29

    We studied the time-resolved fluorescence of isolated RC-LH1 complexes from Rhodopseudomonas palustris as a function of the photon fluence and the repetition rate of the excitation laser. Both parameters were varied systematically over 3 orders of magnitude. On the basis of a microstate description we developed a quantitative model for RC-LH1 and obtained very good agreement between experiments and elaborate simulations based on a global master equation approach. The model allows us to predict the relative population of RC-LH1 complexes with the special pair in the neutral state or in the oxidized state P(+) and those complexes that lack a reaction center.

  18. 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

  19. 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

    International Nuclear Information System (INIS)

    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 FEL pulse

  20. X-ray Absorption Spectroscopy and Coherent X-ray Diffraction Imaging for Time-Resolved Investigation of the Biological Complexes: Computer Modelling towards the XFEL Experiment

    Science.gov (United States)

    Bugaev, A. L.; Guda, A. A.; Yefanov, O. M.; Lorenz, U.; Soldatov, A. V.; Vartanyants, I. A.

    2016-05-01

    The development of the next generation synchrotron radiation sources - free electron lasers - is approaching to become an effective tool for the time-resolved experiments aimed to solve actual problems in various fields such as chemistry’ biology’ medicine’ etc. In order to demonstrate’ how these experiments may be performed for the real systems to obtain information at the atomic and macromolecular levels’ we have performed a molecular dynamics computer simulation combined with quantum chemistry calculations for the human phosphoglycerate kinase enzyme with Mg containing substrate. The simulated structures were used to calculate coherent X-ray diffraction patterns’ reflecting the conformational state of the enzyme, and Mg K-edge X-ray absorption spectra, which depend on the local structure of the substrate. These two techniques give complementary information making such an approach highly effective for time-resolved investigation of various biological complexes, such as metalloproteins or enzymes with metal-containing substrate, to obtain information about both metal-containing active site or substrate and the atomic structure of each conformation.

  1. Acetylene weak bands at 2.5 $\\mu$m from intracavity Cr2+:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy

    CERN Document Server

    Girard, V; Sorokin, E; Sorokina, I T; Guelachvili, G; Picqué, N; Farrenq, Robert; Sorokin, Evgeni; Sorokina, Irina T.; Guelachvili, Guy; Picqu\\'{e}, Nathalie

    2006-01-01

    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_2H_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 n_1+n_4^1 and n_3+n_5^1 transitions of ^12C^13CH_2. The n_1+n_5^1 band of ^12C_2HD and fourteen ^12C_2H_2 bands are observed, among which for the first time n_2+2n_4^2+n_5^-1.

  2. 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.)

  3. 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.

  4. Hyperfine structure and lifetime measurements in the 4s2nd 2D3/2 Rydberg sequence of Ga I by time-resolved laser spectroscopy

    Science.gov (United States)

    Liu, Chunqing; Tian, Yanshan; Yu, Qi; Bai, Wanshuang; Wang, Xinghao; Wang, Chong; Dai, Zhenwen

    2016-05-01

    The hyperfine structure (HFS) constants of the 4s2nd 2D3/2 (n=6-18) Rydberg sequence and the 4s26p 2P3/2 level for two isotopes of 69Ga and 71Ga atoms were measured by means of the time-resolved laser-induced fluorescence (TR-LIF) technique and the quantum beat method. The observed hyperfine quantum beat spectra were analyzed and the magnetic-dipole HFS constants A as well as the electric-quadrupole HFS constants B of these levels were obtained by Fourier transform and a program for multiple regression analysis. Also using TR-LIF method radiative lifetimes of the above sequence states were determined at room temperature. The measured lifetime values range from 69 to 2279 ns with uncertainties no more than 10%. To our knowledge, the HFS constants of this Rydberg sequence and the lifetimes of the 4s2nd 2D3/2 (n=10-18) levels are reported for the first time. Good agreement between our results and the previous is achieved.

  5. Chemically-specific time-resolved surface photovoltage spectroscopy: Carrier dynamics at the interface of quantum dots attached to a metal oxide

    Science.gov (United States)

    Spencer, Ben F.; Cliffe, Matthew J.; Graham, Darren M.; Hardman, Samantha J. O.; Seddon, Elaine A.; Syres, Karen L.; Thomas, Andrew G.; Sirotti, Fausto; Silly, Mathieu G.; Akhtar, Javeed; O'Brien, Paul; Fairclough, Simon M.; Smith, Jason M.; Chattopadhyay, Swapan; Flavell, Wendy R.

    2015-11-01

    We describe a new experimental pump-probe methodology where a 2D delay-line detector enables fast (ns) monitoring of a narrow XPS spectrum in combination with a continuous pump laser. This has been developed at the TEMPO beamline at Synchrotron SOLEIL to enable the study of systems with intrinsically slow electron dynamics, and to complement faster measurements that use a fs laser as the pump. We demonstrate its use in a time-resolved study of the surface photovoltage of the m-plane ZnO (10 1 bar 0) surface which shows persistent photoconductivity, requiring monitoring periods on ms timescales and longer. We make measurements from this surface in the presence and absence of chemically-linked quantum dots (QDs), using type I PbS and type II CdSe/ZnSe (core/shell) QDs as examples. We monitor signals from both the ZnO substrate and the bound QDs during photoexcitation, yielding evidence for charge injection from the QDs into the ZnO. The chemical specificity of the technique allows us to observe differences in the extent to which the QD systems are influenced by the field of the surface depletion layer at the ZnO surface, which we attribute to differences in the band structure at the interface.

  6. 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.

  7. 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)

  8. 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.

  9. Ultrafast Time-Resolved Emission and Absorption Spectra of meso-Pyridyl Porphyrins upon Soret Band Excitation Studied by Fluorescence Up-Conversion and Transient Absorption Spectroscopy.

    Science.gov (United States)

    Venkatesh, Yeduru; Venkatesan, M; Ramakrishna, B; Bangal, Prakriti Ranjan

    2016-09-01

    A comprehensive study of ultrafast molecular relaxation processes of isomeric meso-(pyridyl) porphyrins (TpyPs) has been carried out by using femtosecond time-resolved emission and absorption spectroscopic techniques upon pumping at 400 nm, Soret band (B band or S2), in 4:1 dichloromethane (DCM) and tetrahydrofuran (THF) solvent mixture. By combined studies of fluorescence up-conversion, time-correlated single photon counting, and transient absorption spectroscopic techniques, a complete model with different microscopic rate constants associated with elementary processes involved in electronic manifolds has been reported. Besides, a distinct coherent nuclear wave packet motion in Qy state is observed at low-frequency mode, ca. 26 cm(-1) region. Fluorescence up-conversion studies constitute ultrafast time-resolved emission spectra (TRES) over the whole emission range (430-710 nm) starting from S2 state to Qx state via Qy state. Careful analysis of time profiles of up-converted signals at different emission wavelengths helps to reveal detail molecular dynamics. The observed lifetimes are as indicated: A very fast decay component with 80 ± 20 fs observed at ∼435 nm is assigned to the lifetime of S2 (B) state, whereas being a rise component in the region of between 550 and 710 nm emission wavelength pertaining to Qy and Qx states, it is attributed to very fast internal conversion (IC) occurring from B → Qy and B → Qx as well. Two distinct components of Qy emission decay with ∼200-300 fs and ∼1-1.5 ps time constants are due to intramolecular vibrational redistribution (IVR) induced by solute-solvent inelastic collisions and vibrational redistribution induced by solute-solvent elastic collision, respectively. The weighted average of these two decay components is assigned as the characteristic lifetime of Qy, and it ranges between 0.3 and 0.5 ps. An additional ∼20 ± 2 ps rise component is observed in Qx emission, and it is assigned to the formation time of

  10. 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.

  11. 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.

  12. 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...

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

    CERN Document Server

    Rutkowski, Lucile

    2016-01-01

    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique and we present the corresponding formalism for quantitative broadband spectroscopy. We achieve high sensitivity and broadband performance by acquiring spectra covering more than 2000 cm$^{-1}$ around 12600 cm$^{-1}$ (800 nm), resolving the 3$\

  14. Reaction dynamics of O({sup 1}D) + HCOOD/DCOOH investigated with time-resolved Fourier-transform infrared emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Shang-Chen; Putikam, Raghunath; Lin, M. C., E-mail: chemmcl@emory.edu, E-mail: tsuchis@sepia.plala.or.jp, E-mail: yplee@mail.nctu.edu.tw; Tsuchiya, Soji, E-mail: chemmcl@emory.edu, E-mail: tsuchis@sepia.plala.or.jp, E-mail: yplee@mail.nctu.edu.tw [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Nghia, N. T. [School of Chemical Engineering - Hanoi University of Science and Technology, Hanoi (Viet Nam); Nguyen, Hue M. T. [Center for Computational Science and Faculty of Chemistry, Hanoi National University of Education, Hanoi (Viet Nam); Lee, Yuan-Pern, E-mail: chemmcl@emory.edu, E-mail: tsuchis@sepia.plala.or.jp, E-mail: yplee@mail.nctu.edu.tw [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China)

    2014-10-21

    We investigated the reaction dynamics of O({sup 1}D) towards hydrogen atoms of two types in HCOOH. The reaction was initiated on irradiation of a flowing mixture of O{sub 3} and HCOOD or DCOOH at 248 nm. The relative vibration-rotational populations of OH and OD (1 ≦ v ≦ 4, J ≤ 15) states were determined from time-resolved IR emission recorded with a step-scan Fourier-transform spectrometer. In the reaction of O({sup 1}D) + HCOOD, the rotational distribution of product OH is nearly Boltzmann, whereas that of OD is bimodal. The product ratio [OH]/[OD] is 0.16 ± 0.05. In the reaction of O({sup 1}D) + DCOOH, the rotational distribution of product OH is bimodal, but the observed OD lines are too weak to provide reliable intensities. The three observed OH/OD channels agree with three major channels of production predicted with quantum-chemical calculations. In the case of O({sup 1}D) + HCOOD, two intermediates HOC(O)OD and HC(O)OOD are produced in the initial C−H and O−D insertion, respectively. The former undergoes further decomposition of the newly formed OH or the original OD, whereas the latter produces OD via direct decomposition. Decomposition of HOC(O)OD produced OH and OD with similar vibrational excitation, indicating efficient intramolecular vibrational relaxation, IVR. Decomposition of HC(O)OOD produced OD with greater rotational excitation. The predicted [OH]/[OD] ratio is 0.20 for O({sup 1}D) + HCOOD and 4.08 for O({sup 1}D) + DCOOH; the former agrees satisfactorily with experiments. We also observed the v{sub 3} emission from the product CO{sub 2}. This emission band is deconvoluted into two components corresponding to internal energies E = 317 and 96 kJ mol{sup −1} of CO{sub 2}, predicted to be produced via direct dehydration of HOC(O)OH and secondary decomposition of HC(O)O that was produced via decomposition of HC(O)OOH, respectively.

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

    NARCIS (Netherlands)

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

    2010-01-01

    Solution-phase photoinduced low-spin to high-spin conversion in the Fe-II 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 (1)A(1) -> (MLCT)-M-1 (metal-to-ligand charge transfer) exc

  16. Nuclear magnetic resonance, fluorescence correlation spectroscopy and time-resolved fluorescence anisotropy studies of intermolecular interactions in bis(1-methyl-1H-imidazol-3-ium-3-yl)dihydroborate bis(trifluoromethylsulfonyl)amide and its mixtures with various cosolvents

    Science.gov (United States)

    Sahu, Prabhat Kumar; Nanda, Raju; Seth, Sudipta; Ghosh, Arindam; Sarkar, Moloy

    2016-09-01

    Keeping in mind the potential usefulness of mixed ionic liquid (IL)-cosolvents systems in several industrial applications, intermolecular interactions between a borate-based IL, bis(1-methyl-1H-imidazol-3-ium-3-yl)dihydroborate bis(trifluoromethylsulfonyl)amide ([BIMIMDBA][TF2N]), and its binary mixtures with several molecular solvents has been investigated through NMR and fluorescence spectroscopy. Analysis of the 1H chemical shifts (δ/ppm) and translational diffusion coefficients (D) of the IL in different solvent mixtures demonstrate interplay of nonspecific (ion-dipole) and specific (hydrogen bonding) interactions in governing the properties of these mixtures. Fluorescence correlation spectroscopy (FCS) and time-resolved fluorescence anisotropy data provide evidence in favour of different IL-solvent interaction for different IL-cosolvent systems.

  17. Time-resolved molecular imaging

    Science.gov (United States)

    Xu, Junliang; Blaga, Cosmin I.; Agostini, Pierre; DiMauro, Louis F.

    2016-06-01

    Time-resolved molecular imaging is a frontier of ultrafast optical science and physical chemistry. In this article, we review present and future key spectroscopic and microscopic techniques for ultrafast imaging of molecular dynamics and show their differences and connections. The advent of femtosecond lasers and free electron x-ray lasers bring us closer to this goal, which eventually will extend our knowledge about molecular dynamics to the attosecond time domain.

  18. Development of time-resolved (e, 2e) electron momentum spectroscopy: a tool for visualizing the motion of electrons during a chemical reaction

    International Nuclear Information System (INIS)

    We report the instrumental design and technical details of an (e, 2e) electron momentum spectroscopy (EMS) apparatus, which employs an ultrashort-pulsed incident electron beam with a repetition rate of 5 kHz and a pulse duration in the order of one picosecond. EMS data for the neutral Ar atom in the ground state measured by using the pulsed electron beam are presented to illustrate the potential abilities of the apparatus for ultrafast molecular dynamics. The results are discussed mainly in terms of signal intensity

  19. Ultrafast free-carrier dynamics in Cu2ZnSnS4 single crystals studied using femtosecond time-resolved optical spectroscopy

    OpenAIRE

    Phuong, L. Q.; Okano, M; Yamada, Y.; Yamashita, G.; Morimoto, T.; Nagai, M.; Ashida, M; Nagaoka, A; Yoshino, K; Kanemitsu, Y.

    2014-01-01

    We studied the dynamics of photogenerated carriers in Cu2ZnSnS4 (CZTS) single crystals using femtosecond transient reflectivity (TR) and optical pump-THz probe transient absorption (THz-TA) spectroscopy. The TR and THz-TA decay dynamics consistently showed that free carriers have long lifetimes of up to a few nanoseconds. The excitation-photon-energy-dependent TR measurements revealed a slow picosecond energy relaxation of free carriers to the band edge in CZTS. The relaxation and recombinati...

  20. Ultrafast free-carrier dynamics in Cu{sub 2}ZnSnS{sub 4} single crystals studied using femtosecond time-resolved optical spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Phuong, L. Q.; Kanemitsu, Y., E-mail: kanemitu@scl.kyoto-u.ac.jp [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Japan Science and Technology Agency, CREST, Uji, Kyoto 611-0011 (Japan); Okano, M.; Yamada, Y. [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Yamashita, G.; Morimoto, T.; Nagai, M.; Ashida, M. [Graduate School of Engineering Science, Osaka University, Osaka 560-8531 (Japan); Nagaoka, A. [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Department of Applied Physics and Electronic Engineering, University of Miyazaki, Miyazaki 889-2192 (Japan); Yoshino, K. [Department of Applied Physics and Electronic Engineering, University of Miyazaki, Miyazaki 889-2192 (Japan)

    2014-12-08

    We studied the dynamics of photogenerated carriers in Cu{sub 2}ZnSnS{sub 4} (CZTS) single crystals using femtosecond transient reflectivity (TR) and optical pump-THz probe transient absorption (THz-TA) spectroscopy. The TR and THz-TA decay dynamics consistently showed that free carriers have long lifetimes of up to a few nanoseconds. The excitation-photon-energy-dependent TR measurements revealed a slow picosecond energy relaxation of free carriers to the band edge in CZTS. The relaxation and recombination dynamics of free carriers were affected by nonradiative recombinations at the surface. Our results revealed a global feature of energy relaxation and recombination processes of free carriers in CZTS single crystals.

  1. Evaluation of superconducting gaps in optimally doped Ba(Fe1−xCox)2As2/Fe bilayers by ultrafast time-resolved spectroscopy

    International Nuclear Information System (INIS)

    Highlights: • Femtosecond spectroscopy measurements in FeSe0.5Te05 with Tc = 19 K are reported. • An estimation of a temperature-dependent energy gap Δ(T) at T < Tc is reported. • An electron–phonon constant λ = 06 is estimated. - Abstract: Measurements of nonequilibrium quasi-particle relaxation dynamics by using ultrafast pump and probe technique in optimally Co-doped Ba(Fe2As2)/Fe thin film has been reported. Multiple relaxation processes are present with BCS-like temperature-dependent superconducting gaps Δ0 = (3.67 ± 0.13) meV and Δ1 = (6.1 ± 0.1) meV, which are calculated considering the conventional electron-boson and spin fluctuations pairing mechanism. Then, the value of the electron–phonon coupling constant of λ = 0.18 has been obtained

  2. Time-resolved surface infrared spectroscopy during atomic layer deposition of TiO2 using tetrakis(dimethylamido)titanium and water

    International Nuclear Information System (INIS)

    Atomic layer deposition of titanium dioxide using tetrakis(dimethylamido)titanium (TDMAT) and water vapor is studied by reflection-absorption infrared spectroscopy (RAIRS) with a time resolution of 120 ms. At 190 °C and 240 °C, a decrease in the absorption from adsorbed TDMAT is observed without any evidence of an adsorbed product. Ex situ measurements indicate that this behavior is not associated with an increase in the impurity concentration or a dramatic change in the growth rate. A desorbing decomposition product is consistent with these observations. RAIRS also indicates that dehydroxylation of the growth surface occurs only among one type of surface hydroxyl groups. Molecular water is observed to remain on the surface and participates in reactions even at a relatively high temperature (110 °C) and with long purge times (30 s)

  3. Time-resolved surface infrared spectroscopy during atomic layer deposition of TiO{sub 2} using tetrakis(dimethylamido)titanium and water

    Energy Technology Data Exchange (ETDEWEB)

    Sperling, Brent A., E-mail: brent.sperling@nist.gov; Hoang, John; Kimes, William A.; Maslar, James E. [Chemical Sciences Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8320, Gaithersburg, Maryland 20899-8320 (United States); Steffens, Kristen L. [Biomolecular Measurement Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8362, Gaithersburg, Maryland 20899-8362 (United States); Nguyen, Nhan V. [Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8120, Gaithersburg, Maryland 20899-8120 (United States)

    2014-05-15

    Atomic layer deposition of titanium dioxide using tetrakis(dimethylamido)titanium (TDMAT) and water vapor is studied by reflection-absorption infrared spectroscopy (RAIRS) with a time resolution of 120 ms. At 190 °C and 240 °C, a decrease in the absorption from adsorbed TDMAT is observed without any evidence of an adsorbed product. Ex situ measurements indicate that this behavior is not associated with an increase in the impurity concentration or a dramatic change in the growth rate. A desorbing decomposition product is consistent with these observations. RAIRS also indicates that dehydroxylation of the growth surface occurs only among one type of surface hydroxyl groups. Molecular water is observed to remain on the surface and participates in reactions even at a relatively high temperature (110 °C) and with long purge times (30 s)

  4. Plasmon-exciton coupling at Ag nanocluster decorated TiO2(110) surface studied by time-resolved two-photon photoemission spectroscopy

    Science.gov (United States)

    Tan, Shijing; Argondizzo, Adam; Petek, Hrvoje

    We study the spectroscopy and electron dynamics at Ag nanocluster decorated TiO2(110) surface upon photoexcitation of plasmonic modes by two-photon photoemission spectroscopy (2PP). Depositing Ag onto a reduced rutile TiO2(110) surface at room temperature forms pancake-like Ag particles with an average diameter of 4 nm and height of 1.5 nm. Measurements of the 2PP yield from Ag/TiO2 surface with tunable femtosecond laser excitation show enhancement at plasmonic resonances. Exciting with s-polarization (S -->) the plasmonic resonance enhancement has a single peak at 3.1 eV, whereas with p-polarization (P -->) there is an additional more intense resonance at 3.8 eV. We attribute the 3.1 and 3.8 eV peaks to the in-plane and the surface-normal plasmon modes respectively. Crystal azimuth orientation dependent excitation with (S -->) shows an anisotropy in the 2PP spectra for the 3.1 eV in-plane plasmon mode when the laser electric field is aligned in the [001] vs. [ 1 1 0 ] directions. The existence of two plasmon modes and the in-plane plasmon anisotropy imply that the plasmon modes are perturbed by coherent coupling with excitons in the rutile TiO2 substrate. We speculate that plasmon-exciton resonant energy transfer could play an important role in the plasmonically enhanced photocatalysis at the Ag/TiO2 surface.

  5. 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.

  6. 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.

  7. Time resolved spectroscopy and photometry of three little known bright cataclysmic variables: LS IV -08$^{\\rm o}$ 3, HQ Monocerotis and ST Chamaeleontis

    CERN Document Server

    Bruch, Albert

    2016-01-01

    As part of a project to better characterize comparatively bright but so far little studied cataclysmic variables in the southern hemisphere, we have obtained spectroscopic and photometric data of the nova-like variables LS IV -08$^{\\rm o}$ 3 and HQ Mon, and of the Z Cam type dwarf nova ST Cha. The spectra of all systems are as expected for their respective types. We derive improved orbital ephemeris of LS IV -08$^{\\rm o}$ 3 and map its accretion disk in the light of the H$\\alpha$ emission using Doppler tomography. We find that the emission has a two component origin, arising in the outer parts of the accretion disk and possibly on the illuminated face of the secondary star. The light curve of LS IV -08$^{\\rm o}$ 3 exhibits a low level of flickering and indications for a modulation on the orbital period. Spectroscopy of HQ Mon suggests an orbital period of $\\approx$5.15 hours which is incompatible with previous (uncertain) estimates. The light curves show the typical low scale flickering of UX UMa type nova-li...

  8. 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

    2016-03-01

    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. PMID:26891098

  9. Mechanistic study of electrocatalytic oxidation of formic acid at platinum in acidic solution by time-resolved surface-enhanced infrared absorption spectroscopy.

    Science.gov (United States)

    Samjeské, Gabor; Miki, Atsushi; Ye, Shen; Osawa, Masatoshi

    2006-08-24

    Surface-enhanced infrared absorption spectroscopy (SEIRAS) combined with cyclic voltammetry or chronoamperometry has been utilized to examine kinetic and mechanistic aspects of the electrocatalytic oxidation of formic acid on a polycrystalline Pt surface at the molecular scale. Formate is adsorbed on the electrode in a bridge configuration in parallel to the adsorption of linear and bridge CO produced by dehydration of formic acid. A solution-exchange experiment using isotope-labeled formic acids (H(12)COOH and H(13)COOH) reveals that formic acid is oxidized to CO(2) via adsorbed formate and the decomposition (oxidation) of formate to CO(2) is the rate-determining step of the reaction. The adsorption/oxidation of CO and the oxidation/reduction of the electrode surface strongly affect the formic acid oxidation by blocking active sites for formate adsorption and also by retarding the decomposition of adsorbed formate. The interplay of the involved processes also affects the kinetics and complicates the cyclic voltammograms of formic acid oxidation. The complex voltammetric behavior is comprehensively explained at the molecular scale by taking all these effects into account. PMID:16913790

  10. Time-resolved in situ detection of CO in a shock tube using cavity-enhanced absorption spectroscopy with a quantum-cascade laser near 4.6 µm.

    Science.gov (United States)

    Sun, Kai; Wang, Shengkai; Sur, Ritobrata; Chao, Xing; Jeffries, Jay B; Hanson, Ronald K

    2014-10-01

    Cavity-enhanced absorption spectroscopy (CEAS) using a mid-infrared DFB quantum-cascade laser is reported for sensitive time-resolved (10 μs) in situ CO measurements in a shock tube. Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 91 was demonstrated, which enabled sub-ppm detection sensitivity for gas temperatures of 1000-2100K in a 15 cm diameter shock tube. This substantial improvement in detection sensitivity compared to conventional single-pass absorption measurements, shows great potential for the study of reaction pathways of high-temperature combustion kinetics mechanisms in shock tubes.

  11. 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)

  12. Near-field imaging and nano-Fourier-transform infrared spectroscopy using broadband synchrotron radiation.

    Science.gov (United States)

    Hermann, Peter; Hoehl, Arne; Patoka, Piotr; Huth, Florian; Rühl, Eckart; Ulm, Gerhard

    2013-02-11

    We demonstrate scanning near-field optical microscopy with a spatial resolution below 100 nm by using low intensity broadband synchrotron radiation in the IR regime. The use of such a broadband radiation source opens up the possibility to perform nano-Fourier-transform infrared spectroscopy over a wide spectral range. PMID:23481749

  13. Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility

    International Nuclear Information System (INIS)

    A single-shot CCD-based data acquisition system for time-resolved photoelectron spectroscopy using an X-ray free-electron laser has been developed. The basic performance of the system is demonstrated using XFEL-induced and synchrotron-radiation-induced Ti 1s core-level spectroscopy. In order to utilize high-brilliance photon sources, such as X-ray free-electron lasers (XFELs), for advanced time-resolved photoelectron spectroscopy (TR-PES), a single-shot CCD-based data acquisition system combined with a high-resolution hemispherical electron energy analyzer has been developed. The system’s design enables it to be controlled by an external trigger signal for single-shot pump–probe-type TR-PES. The basic performance of the system is demonstrated with an offline test, followed by online core-level photoelectron and Auger electron spectroscopy in ‘single-shot image’, ‘shot-to-shot image (image-to-image storage or block storage)’ and ‘shot-to-shot sweep’ modes at soft X-ray undulator beamline BL17SU of SPring-8. In the offline test the typical repetition rate for image-to-image storage mode has been confirmed to be about 15 Hz using a conventional pulse-generator. The function for correcting the shot-to-shot intensity fluctuations of the exciting photon beam, an important requirement for the TR-PES experiments at FEL sources, has been successfully tested at BL17SU by measuring Au 4f photoelectrons with intentionally controlled photon flux. The system has also been applied to hard X-ray PES (HAXPES) in ‘ordinary sweep’ mode as well as shot-to-shot image mode at the 27 m-long undulator beamline BL19LXU of SPring-8 and also at the SACLA XFEL facility. The XFEL-induced Ti 1s core-level spectrum of La-doped SrTiO3 is reported as a function of incident power density. The Ti 1s core-level spectrum obtained at low power density is consistent with the spectrum obtained using the synchrotron source. At high power densities the Ti 1s core-level spectra show

  14. Time resolved spectroscopic studies on some nanophosphors

    Indian Academy of Sciences (India)

    Harish Chander; Santa Chawla

    2008-06-01

    Time resolved spectroscopy is an important tool for studying photophysical processes in phosphors. Present work investigates the steady state and time resolved photoluminescence (PL) spectroscopic characteristics of ZnS, ZnO and (Zn, Mg)O nanophosphors both in powder as well as thin film form. Photoluminescence (PL) of ZnS nanophosphors typically exhibit a purple/blue emission peak termed as self activated (SA) luminescence and emission at different wavelengths arising due to dopant impurities e.g. green emission for ZnS : Cu, orange emission for ZnS : Mn and red emission for ZnS : Eu. The lifetimes obtained from decay curves range from ns to ms level and suggest the radiative recombination path involving donor–acceptor pair recombination or internal electronic transitions of the impurity atom. A series of ZnMgO nanophosphor thin films with varied Zn : Mg ratios were prepared by chemical bath deposition. Photoluminescence (PL) excitation and emission spectra exhibit variations with changing Mg ratio. Luminescence lifetime as short as 10-10 s was observed for ZnO and ZnMgO (100 : 10) nanophosphors. With increasing Mg ratio, PL decay shifts into microsecond range. ZnO and ZnMgO alloys up to 50% Mg were prepared as powder by solid state mixing and sintering at high temperature in reducing atmosphere. Time resolved decay of PL indicated lifetime in the microsecond time scale. The novelty of the work lies in clear experimental evidence of dopants (Cu, Mn, Eu and Mg) in the decay process and luminescence life times in II–VI semiconductor nanocrystals of ZnS and ZnO. For ZnS, blue self activated luminescence decays faster than Cu and Mn related emission. For undoped ZnO nanocrystals, PL decay is in the nanosecond range whereas with Mg doping the decay becomes much slower in the microsecond range.

  15. Optimal multisine excitation design for broadband electrical impedance spectroscopy

    International Nuclear Information System (INIS)

    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

  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. Time-resolved spectroscopy using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Poliakoff, E.D.

    1979-08-01

    Work performed at the Stanford Synchrotron Radiation Laboratory (SSRL) is reported. The timing characteristics of the SPEAR beam (pulse width less than or equal to 0.4 nsec, pulse repetition period = 780 nsec) were exploited to determine dynamic behavior of atomic, molecular, excimeric, and photodissociative gas-phase species excited by vacuum-ultraviolet (VUV) radiation. Fast fluorescence timing measurements were done to determine excited-state lifetimes of Kr and Xe. Pressure-dependent timing studies on Xe gas at higher concentrations demonstrated some of the problems associated with previous kinetic modeling of the Xe/sub 2/ system. It was found that even qualitative agreement of observed Xe/sub 2/ lifetimes as a function of pressure required the assumption that the radiative lifetime was a strong function of internuclear separation. The radiative decays of chemically unstable fragments, CN* (B/sup 2/..sigma../sup +/) and XeF* (B/sup 2/..sigma../sup +/ and C/sup 2/ Pi/sub 3/2//), were studied by pulsed photodissociation of stable parent compounds, ICN and XeF/sub 2/. When the polarization of the CN* (B/sup 2/..sigma../sup +/) fragment fluorescence was measured, it was found to be non-zero and strongly dependent on excitation wavelength. This polarization is related to the symmetry of the photodissociative surface via a classical model, and the variations in the polarization with wavelength is attributed to symmetry and lifetime effects of a predissociating parent molecule. Despite the drawbacks of limited availability and low radiation flux, synchrotron radiation is definitely a useful spectroscopic tool for VUV studies of gas-phase systems.

  18. Time-resolved spectroscopy using synchrotron radiation

    International Nuclear Information System (INIS)

    Work performed at the Stanford Synchrotron Radiation Laboratory (SSRL) is reported. The timing characteristics of the SPEAR beam (pulse width less than or equal to 0.4 nsec, pulse repetition period = 780 nsec) were exploited to determine dynamic behavior of atomic, molecular, excimeric, and photodissociative gas-phase species excited by vacuum-ultraviolet (VUV) radiation. Fast fluorescence timing measurements were done to determine excited-state lifetimes of Kr and Xe. Pressure-dependent timing studies on Xe gas at higher concentrations demonstrated some of the problems associated with previous kinetic modeling of the Xe2 system. It was found that even qualitative agreement of observed Xe2 lifetimes as a function of pressure required the assumption that the radiative lifetime was a strong function of internuclear separation. The radiative decays of chemically unstable fragments, CN* (B2Σ+) and XeF* (B2Σ+ and C2 Pi/sub 3/2//), were studied by pulsed photodissociation of stable parent compounds, ICN and XeF2. When the polarization of the CN* (B2Σ+) fragment fluorescence was measured, it was found to be non-zero and strongly dependent on excitation wavelength. This polarization is related to the symmetry of the photodissociative surface via a classical model, and the variations in the polarization with wavelength is attributed to symmetry and lifetime effects of a predissociating parent molecule. Despite the drawbacks of limited availability and low radiation flux, synchrotron radiation is definitely a useful spectroscopic tool for VUV studies of gas-phase systems

  19. Structural and dynamical properties of Mg{sub 65}Cu{sub 25}Y{sub 10} metallic glasses studied by in situ high energy X-ray diffraction and time resolved X-ray photon correlation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ruta, B., E-mail: ruta@esrf.fr [European Synchrotron Radiation Facility, BP220, F-38043 Grenoble (France); Giordano, V.M. [ILM, Université Claude Bernard Lyon 1 and CNRS, 69622 Villeurbanne (France); Erra, L. [European Synchrotron Radiation Facility, BP220, F-38043 Grenoble (France); Liu, C.; Pineda, E. [Departament Física i Enginyeria Nuclear, ESAB, UPC-BarcelonaTech, Castelldefels (Spain)

    2014-12-05

    Highlights: • Study of rapidly quenched Mg-based metallic glasses under different thermal paths. • The atomic dynamics was investigated by X-ray photon correlation spectroscopy. • The structural changes were followed by in situ high energy X-ray diffraction. • Dynamical and structural properties of Mg-based metallic glasses at the atomic level. • Strengthened idea of a stress-induced atomic motion in metallic glasses. - Abstract: We present a temperature investigation of the structural and dynamical evolution of rapidly quenched metallic glasses of Mg{sub 65}Cu{sub 25}Y{sub 10} at the atomic length scale by means of in situ high energy X-ray diffraction and time resolved X-ray photon correlation spectroscopy. We find a flattening of the temperature evolution of the position of the first sharp diffraction peak on approaching the glass transition temperature from the glassy state, which reflects into a surprising slowing down of the relaxation dynamics of even one order of magnitude with increasing temperature. The comparison between structural and dynamical properties strengthens the idea of a stress-induced, rather than pure diffusive, atomic motion in metallic glasses.

  20. Structural and dynamical properties of Mg65Cu25Y10 metallic glasses studied by in situ high energy X-ray diffraction and time resolved X-ray photon correlation spectroscopy

    International Nuclear Information System (INIS)

    Highlights: • Study of rapidly quenched Mg-based metallic glasses under different thermal paths. • The atomic dynamics was investigated by X-ray photon correlation spectroscopy. • The structural changes were followed by in situ high energy X-ray diffraction. • Dynamical and structural properties of Mg-based metallic glasses at the atomic level. • Strengthened idea of a stress-induced atomic motion in metallic glasses. - Abstract: We present a temperature investigation of the structural and dynamical evolution of rapidly quenched metallic glasses of Mg65Cu25Y10 at the atomic length scale by means of in situ high energy X-ray diffraction and time resolved X-ray photon correlation spectroscopy. We find a flattening of the temperature evolution of the position of the first sharp diffraction peak on approaching the glass transition temperature from the glassy state, which reflects into a surprising slowing down of the relaxation dynamics of even one order of magnitude with increasing temperature. The comparison between structural and dynamical properties strengthens the idea of a stress-induced, rather than pure diffusive, atomic motion in metallic glasses

  1. Time-Resolved Fluorescence Assays.

    Science.gov (United States)

    Ma, Chen-Ting; Sergienko, Eduard A

    2016-01-01

    Fluorescence-based detection techniques are popular in high throughput screening due to sensitivity and cost-effectiveness. Four commonly used techniques exist, each with distinct characteristics. Fluorescence intensity assays are the simplest to run, but suffer the most from signal interference. Fluorescence polarization assays show less interference from the compounds or the instrument, but require a design that results in change of fluorophore-containing moiety size and usually have narrow assay signal window. Fluorescence resonance energy transfer (FRET) is commonly used for detecting protein-protein interactions and is constrained not by the sizes of binding partners, but rather by the distance between fluorophores. Time-resolved fluorescence resonance energy transfer (TR-FRET), an advanced modification of FRET approach utilizes special fluorophores with long-lived fluorescence and earns its place near the top of fluorescent techniques list by its performance and robustness, characterized by larger assay window and minimized compound spectral interference. TR-FRET technology can be applied in biochemical or cell-based in vitro assays with ease. It is commonly used to detect modulation of protein-protein interactions and in detection of products of biochemical reactions and cellular activities. PMID:27316992

  2. Sensing cell metabolism by time-resolved autofluorescence

    Science.gov (United States)

    Wu, Yicong; Zheng, Wei; Qu, Jianan Y.

    2006-11-01

    We built a time-resolved confocal fluorescence spectroscopy system equipped with the multichannel time-correlated single-photon-counting technique. The instrument provides a unique approach to study the fluorescence sensing of cell metabolism via analysis of the wavelength- and time-resolved intracellular autofluorescence. The experiments on monolayered cell cultures show that with UV excitation at 365 nm the time-resolved autofluorescence decays, dominated by free-bound reduced nicotinamide adenine dinucleotide signals, are sensitive indicators for cell metabolism. However, the sensitivity decreases with the increase of excitation wavelength possibly due to the interference from free-bound flavin adenine dinucleotide fluorescence. The results demonstrate that time-resolved autofluorescence can be potentially used as an important contrast mechanism to detect epithelial precancer.

  3. Direct and quantitative broadband absorptance spectroscopy with multilayer cantilever probes

    Science.gov (United States)

    Hsu, Wei-Chun; Tong, Jonathan Kien-Kwok; Liao, Bolin; Chen, Gang

    2015-04-21

    A system for measuring the absorption spectrum of a sample is provided that includes a broadband light source that produces broadband light defined within a range of an absorptance spectrum. An interferometer modulates the intensity of the broadband light source for a range of modulation frequencies. A bi-layer cantilever probe arm is thermally connected to a sample arm having at most two layers of materials. The broadband light modulated by the interferometer is directed towards the sample and absorbed by the sample and converted into heat, which causes a temperature rise and bending of the bi-layer cantilever probe arm. A detector mechanism measures and records the deflection of the probe arm so as to obtain the absorptance spectrum of the sample.

  4. 一种时间分辨激光诱导击穿光谱的测量方法%A Method for Time-Resolved Laser-Induced Breakdown Spectroscopy Measurement

    Institute of Scientific and Technical Information of China (English)

    潘从元; 韩振宇; 李朝阳; 于云偲; 王声波; 王秋平

    2014-01-01

    Laser-Induced Breakdown Spectroscopy (LIBS) is strongly time related .Time-resolved LIBS measurement is an im-portant 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 μs-scale time-resolved LIBS measurement by using general ms-scale detector .By setting different integration delay time of the ms-scale spectrum detec-tor ,a series of spectrum are recorded .And the integration delay time interval should be longer than the worst temporal preci-sion .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 μs ,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 .%激光诱导击穿光谱(L IBS )是一种动态光谱。时间分辨L IBS光谱测量是研究激光诱导等离子体演化和谱线自吸收的重要技术。结合激光诱导击穿光谱测量的时序特性,提出一种利用常规性能光谱探测设备获得微秒级时间分辨L IBS光谱的测量方法。通过控制毫秒级光谱探测设备的积分延迟时间,获得不同延时下的L IB S光谱信号,对所得光谱进行处理得

  5. Optical characterization of fourfold (T{sub d})- and sixfold (O{sub h})-transition-metal species in MgAl{sub 2}O{sub 4}:Co{sup 2+} by time-resolved spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nataf, L., E-mail: lucie.nataf@unican.e [DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander (Spain); Rodriguez, F. [DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander (Spain); Valiente, R. [Department Fisica Aplicada, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander (Spain); Ulanov, V. [Russian Academy of Sciences, Sibirski Trakt 10/7, 420029 Kazan (Russian Federation)

    2009-12-15

    This work investigates the origin of novel visible photoluminescence (PL) bands observed in the spinel MgAl{sub 2}O{sub 4}:Co{sup 2+}. Besides the well-known fourfold-coordinated Co{sup 2+}(T{sub d}) PL at 670 nm [N.V. Kuleshov, V.P. Mikhailov, V.G. Scherbitsky, P.V. Prokoshin and K.V. Yumashev, J. Lumin. 55 (1993) 265.], a rich structured PL band at 686 nm was also observed that we associate with uncontrolled impurities of sixfold coordinated Cr{sup 3+}(O{sub h}) by time-resolved spectroscopy and lifetime measurements and their variation with temperature. We also show that the lifetime of the Co{sup 2+}(T{sub d}) emission at 670 nm varies from tau=6.7 mus to 780 ns on passing from T=10 to 290 K. This unexpected behaviour for T{sub d} systems is related to the excited-state crossover ({sup 4}T{sub 1}reversible{sup 2}E), making the emission band to transform from a narrow-like emission from {sup 2}E at low temperature to a broad structureless band from {sup 4}T{sub 1} at room temperature.

  6. 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.

  7. Complexation of Cm(III) and Eu(III) with a hydrophilic 2,6-bis(1,2,4-triazin-3-yl)-pyridine studied by time-resolved laser fluorescence spectroscopy.

    Science.gov (United States)

    Ruff, Christian M; Müllich, Udo; Geist, Andreas; Panak, Petra J

    2012-12-28

    The complexation of Cm(III) and Eu(III) with 2,6-bis(5,6-di(sulfophenyl)-1,2,4-triazin-3-yl)pyridine (aq-BTP) is studied in water at pH 3.0 applying time-resolved laser fluorescence spectroscopy. With increasing ligand concentration [M(H(2)O)(9-3n)(aq-BTP)(n)] (M = Cm(III)/Eu(III), n = 1, 2, 3) complex species are spectroscopically identified. The conditional stability constants of the M(III) 1 : 3 complex species with aq-BTP are log β(03) = 12.2 for Cm(III) and log β(03) = 10.2 for Eu(III). The complexation reaction is enthalpy- and entropy-driven for both metal ions, while the enthalpy change ΔH(03) is 9.7 kJ mol(-1) more negative for Cm(III); changes in ΔS(03) are marginal. The difference in ΔG(03) of -12.7 kJ mol(-1) between the formation of the [M(aq-BTP)(3)] complexes agrees with aq-BTP's selectivity in liquid-liquid extraction studies.

  8. High-sensitivity broadband microwave spectroscopy with small nonresonant coils

    Science.gov (United States)

    Mahdjour, H.; Clark, W. G.; Baberschke, K.

    1986-06-01

    The use of a small, nonresonant, coil of micron dimensions as the microwave magnetic field structure of a broadband electron-spin-resonance (ESR) spectrometer is described. The coil is driven by a broadband microwave generator which operates between 0.1 and 8.5 GHz. The samples may fill the coil to approximately 100 percent. It is shown that for small size samples this system offers higher sensitivity than a conventional cavity spectrometer. Because the system is broadband, either frequency scans or the conventional magnetic field scans can be used to traverse the resonance. Examples for DPPH and for the spin glass AgMn using this method are reported. Since the sample coil is small, it has many potential applications, such as insertion into the mixing chamber of dilution refrigerator or high-pressure cell, efficient use of power in ENDOR and other double resonance experiments, and rapid recovery from transients in pulsed ESR experiments.

  9. Broadband cavity enhanced spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

    OpenAIRE

    Washenfelder, R. A.; A. R. Attwood; Flores, J. M.; Rudich, Y.; S. S. Brown

    2015-01-01

    Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity enhanced spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and ...

  10. Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) – applicability and corrections

    OpenAIRE

    U. Platt; J. Meinen; D. Pöhler; T. Leisner

    2008-01-01

    Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broadband light sources, the broadband CEAS (BB-CEAS). BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light pa...

  11. Ultraviolet photochemical reaction of [Fe(III)(C2O4)3](3-) in aqueous solutions studied by femtosecond time-resolved X-ray absorption spectroscopy using an X-ray free electron laser.

    Science.gov (United States)

    Ogi, Y; Obara, Y; Katayama, T; Suzuki, Y-I; Liu, S Y; Bartlett, N C-M; Kurahashi, N; Karashima, S; Togashi, T; Inubushi, Y; Ogawa, K; Owada, S; Rubešová, M; Yabashi, M; Misawa, K; Slavíček, P; Suzuki, T

    2015-05-01

    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)(C2O4)3](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)(C2O4)3](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)(C2O4)2](3-) and subsequently [Fe(II)(C2O4)2](2-).

  12. 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.

  13. 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−.

  14. 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.

  15. Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility.

    Science.gov (United States)

    Oura, Masaki; Wagai, Tatsuya; Chainani, Ashish; Miyawaki, Jun; Sato, Hiromi; Matsunami, Masaharu; Eguchi, Ritsuko; Kiss, Takayuki; Yamaguchi, Takashi; Nakatani, Yasuhiro; Togashi, Tadashi; Katayama, Tetsuo; Ogawa, Kanade; Yabashi, Makina; Tanaka, Yoshihito; Kohmura, Yoshiki; Tamasaku, Kenji; Shin, Shik; Ishikawa, Tetsuya

    2014-01-01

    In order to utilize high-brilliance photon sources, such as X-ray free-electron lasers (XFELs), for advanced time-resolved photoelectron spectroscopy (TR-PES), a single-shot CCD-based data acquisition system combined with a high-resolution hemispherical electron energy analyzer has been developed. The system's design enables it to be controlled by an external trigger signal for single-shot pump-probe-type TR-PES. The basic performance of the system is demonstrated with an offline test, followed by online core-level photoelectron and Auger electron spectroscopy in 'single-shot image', 'shot-to-shot image (image-to-image storage or block storage)' and `shot-to-shot sweep' modes at soft X-ray undulator beamline BL17SU of SPring-8. In the offline test the typical repetition rate for image-to-image storage mode has been confirmed to be about 15 Hz using a conventional pulse-generator. The function for correcting the shot-to-shot intensity fluctuations of the exciting photon beam, an important requirement for the TR-PES experiments at FEL sources, has been successfully tested at BL17SU by measuring Au 4f photoelectrons with intentionally controlled photon flux. The system has also been applied to hard X-ray PES (HAXPES) in `ordinary sweep' mode as well as shot-to-shot image mode at the 27 m-long undulator beamline BL19LXU of SPring-8 and also at the SACLA XFEL facility. The XFEL-induced Ti 1s core-level spectrum of La-doped SrTiO3 is reported as a function of incident power density. The Ti 1s core-level spectrum obtained at low power density is consistent with the spectrum obtained using the synchrotron source. At high power densities the Ti 1s core-level spectra show space-charge effects which are analysed using a known mean-field model for ultrafast electron packet propagation. The results successfully confirm the capability of the present data acquisition system for carrying out the core-level HAXPES studies of condensed matter induced by the XFEL. PMID:24365935

  16. Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility.

    Science.gov (United States)

    Oura, Masaki; Wagai, Tatsuya; Chainani, Ashish; Miyawaki, Jun; Sato, Hiromi; Matsunami, Masaharu; Eguchi, Ritsuko; Kiss, Takayuki; Yamaguchi, Takashi; Nakatani, Yasuhiro; Togashi, Tadashi; Katayama, Tetsuo; Ogawa, Kanade; Yabashi, Makina; Tanaka, Yoshihito; Kohmura, Yoshiki; Tamasaku, Kenji; Shin, Shik; Ishikawa, Tetsuya

    2014-01-01

    In order to utilize high-brilliance photon sources, such as X-ray free-electron lasers (XFELs), for advanced time-resolved photoelectron spectroscopy (TR-PES), a single-shot CCD-based data acquisition system combined with a high-resolution hemispherical electron energy analyzer has been developed. The system's design enables it to be controlled by an external trigger signal for single-shot pump-probe-type TR-PES. The basic performance of the system is demonstrated with an offline test, followed by online core-level photoelectron and Auger electron spectroscopy in 'single-shot image', 'shot-to-shot image (image-to-image storage or block storage)' and `shot-to-shot sweep' modes at soft X-ray undulator beamline BL17SU of SPring-8. In the offline test the typical repetition rate for image-to-image storage mode has been confirmed to be about 15 Hz using a conventional pulse-generator. The function for correcting the shot-to-shot intensity fluctuations of the exciting photon beam, an important requirement for the TR-PES experiments at FEL sources, has been successfully tested at BL17SU by measuring Au 4f photoelectrons with intentionally controlled photon flux. The system has also been applied to hard X-ray PES (HAXPES) in `ordinary sweep' mode as well as shot-to-shot image mode at the 27 m-long undulator beamline BL19LXU of SPring-8 and also at the SACLA XFEL facility. The XFEL-induced Ti 1s core-level spectrum of La-doped SrTiO3 is reported as a function of incident power density. The Ti 1s core-level spectrum obtained at low power density is consistent with the spectrum obtained using the synchrotron source. At high power densities the Ti 1s core-level spectra show space-charge effects which are analysed using a known mean-field model for ultrafast electron packet propagation. The results successfully confirm the capability of the present data acquisition system for carrying out the core-level HAXPES studies of condensed matter induced by the XFEL.

  17. Self-referenced ultra-broadband transient terahertz spectroscopy using air-photonics.

    Science.gov (United States)

    D'Angelo, F; Němec, H; Parekh, S H; Kužel, P; Bonn, M; Turchinovich, D

    2016-05-01

    Terahertz (THz) air-photonics employs nonlinear interactions of ultrashort laser pulses in air to generate and detect THz pulses. As air is virtually non-dispersive, the optical-THz phase matching condition is automatically met, thus permitting the generation and detection of ultra-broadband THz pulses covering the entire THz spectral range without any gaps. Air-photonics naturally offers unique opportunities for ultra-broadband transient THz spectroscopy, yet many critical challenges inherent to this technique must first be resolved. Here, we present explicit guidelines for ultra-broadband transient THz spectroscopy with air-photonics, including a novel method for self-referenced signal acquisition minimizing the phase error, and the numerically-accurate approach to the transient reflectance data analysis. PMID:27137624

  18. Dynamics of substituted Alkyl monolayers covalently bonded to silicon: A broadband admittance spectroscopy study

    NARCIS (Netherlands)

    Godet, C.; Fadjie-Djomkam, A.B.; Ababou-Girard, S.; Tricot, S.; Turban, P.; Li, Y.; Pujari, S.P.; Scheres, L.M.W.; Zuilhof, H.; Fabre, B.

    2014-01-01

    The relaxation dynamics of surface-bound n-alkyl chains was studied by broadband admittance spectroscopy (10 mHz–10 MHz) measured at low temperature (130–300 K) in the reverse bias regime of rectifying Hg//organic monolayer (OML)–n-doped Si tunnel junctions. To obtain molecular-level information on

  19. Conformational Analysis of Ibuprofen Using Broadband Microwave Spectroscopy

    Science.gov (United States)

    Zinn, Sabrina; Betz, Thomas; Schnell, Melanie

    2014-06-01

    The broadband rotational spectrum of ibuprofen ((RS)-2-(4-isobutylphenyl)-propanoic acid), a well-known drug, will be presented. As it is used to relieve pain, reduce fever, and inhibit inflammation, the knowledge of its biological activity is very interesting. Insights to the conformational flexibility of this drug might lead to a better understanding of the class of non-steroidal anti-inflammatory drugs that ibuprofen belongs to. The spectrum was recorded with our broadband chirped-pulse Fourier transform microwave spectrometer in the frequency range of 2.0 - 8.3 GHz. With the obtained results, we are able to identify several conformers of ibuprofen and to determine their rotational constants. Density functional theory calculations were performed and used to support the conformational assignments. Fragments of ibuprofen could be also identified in the spectrum, which can be explained by thermal decomposition during the heating process for vaporizing it. The analysis of this fragmentation process as a function of temperature might provide us with some interesting insights into its mechanism.

  20. Characterization of mechanical properties of materials using ultrasound broadband spectroscopy.

    Science.gov (United States)

    Agrawal, Megha; Prasad, Abhinav; Bellare, Jayesh R; Seshia, Ashwin A

    2016-01-01

    This article explores the characterization of homogenous materials (metals, alloys, glass and polymers) by a simple broadband ultrasonic interrogation method. The novelty lies in the use of ultrasound in a continuous way with very low input power (0 dBm or less) and analysis of the transmitted acoustic wave spectrum for material property characterization like speed of sound, density and dimensions of a material. Measurements were conducted on various thicknesses of samples immersed in liquid where continuous-wave, frequency swept ultrasonic energy was incident normal to the sample surface. The electro-acoustic transmission response is analyzed in the frequency domain with respect to a specifically constructed multi-layered analytical model. From the acoustic signature of the sample materials, material properties such as speed of sound and acoustic impedance can be calculated with experimentally derived values found to be in general agreement with the literature and with pulse-echo technique establishing the basis for a non-contact and non-destructive technique for material characterization. Further, by looking at the frequency spacing of the peaks of water when the sample is immersed, the thickness of the sample can be calculated independently from the acoustic response. This technique can prove to be an effective non-contact, non-destructive and fast material characterization technique for a wide variety of materials.

  1. 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

    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...

  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. Time resolved thermal lens in edible oils

    Science.gov (United States)

    Albuquerque, T. A. S.; Pedreira, P. R. B.; Medina, A. N.; Pereira, J. R. D.; Bento, A. C.; Baesso, M. L.

    2003-01-01

    In this work time resolved thermal lens spectrometry is applied to investigate the optical properties of the following edible oils: soya, sunflower, canola, and corn oils. The experiments were performed at room temperature using the mode mismatched thermal lens configuration. The results showed that when the time resolved procedure is adopted the technique can be applied to investigate the photosensitivity of edible oils. Soya oil presented a stronger photochemical reaction as compared to the other investigated samples. This observation may be relevant for future studies evaluating edible oils storage conditions and also may contribute to a better understanding of the physical and chemical properties of this important foodstuff.

  4. Broadband light scattering spectroscopy utilizing an ultra-narrowband holographic notch filter

    Science.gov (United States)

    Fujii, Yasuhiro; Katayama, Daisuke; Koreeda, Akitoshi

    2016-10-01

    The broadband spectroscopic analysis over Brillouin, quasi-elastic, and Raman regions arising from the same position of the sample has been achieved by employing an ultra-narrowband holographic notch filter (HNF) and an optical isolator. Recently, HNFs are often employed to reject strong elastic scattering in low-frequency Raman experiments. Meanwhile, the rejected spectral component agrees with the frequency range that can be observed by a triple-pass tandem Fabry-Pérot interferometer. Thus the broadband spectroscopy can be accomplished by introducing the rejected light to the interferometer. This system, in combination with the local symmetry analysis by polarization-direction-resolved Raman spectroscopy, is particularly advantageous for the investigation of spatially inhomogeneous systems.

  5. Perspective: The first ten years of broadband chirped pulse Fourier transform microwave spectroscopy.

    Science.gov (United States)

    Park, G Barratt; Field, Robert W

    2016-05-28

    Since its invention in 2006, the broadband chirped pulse Fourier transform spectrometer has transformed the field of microwave spectroscopy. The technique enables the collection of a ≥10 GHz bandwidth spectrum in a single shot of the spectrometer, which allows broadband, high-resolution microwave spectra to be acquired several orders of magnitude faster than what was previously possible. We discuss the advantages and challenges associated with the technique and look back on the first ten years of chirped pulse Fourier transform spectroscopy. In addition to enabling faster-than-ever structure determination of increasingly complex species, the technique has given rise to an assortment of entirely new classes of experiments, ranging from chiral sensing by three-wave mixing to microwave detection of multichannel reaction kinetics. However, this is only the beginning. Future generations of microwave experiments will make increasingly creative use of frequency-agile pulse sequences for the coherent manipulation and interrogation of molecular dynamics.

  6. Perspective: The first ten years of broadband chirped pulse Fourier transform microwave spectroscopy

    Science.gov (United States)

    Park, G. Barratt; Field, Robert W.

    2016-05-01

    Since its invention in 2006, the broadband chirped pulse Fourier transform spectrometer has transformed the field of microwave spectroscopy. The technique enables the collection of a ≥10 GHz bandwidth spectrum in a single shot of the spectrometer, which allows broadband, high-resolution microwave spectra to be acquired several orders of magnitude faster than what was previously possible. We discuss the advantages and challenges associated with the technique and look back on the first ten years of chirped pulse Fourier transform spectroscopy. In addition to enabling faster-than-ever structure determination of increasingly complex species, the technique has given rise to an assortment of entirely new classes of experiments, ranging from chiral sensing by three-wave mixing to microwave detection of multichannel reaction kinetics. However, this is only the beginning. Future generations of microwave experiments will make increasingly creative use of frequency-agile pulse sequences for the coherent manipulation and interrogation of molecular dynamics.

  7. Broadband excitation for short-time impedance spectroscopy

    International Nuclear Information System (INIS)

    Frequency domain impedance measurements are still the common approach in assessing passive electrical properties of cells and tissues. However, due to the time requirements for sweeping over a frequency range for performing spectroscopy, they are not suited for recovering fast impedance changes of biological objects. The use of broad bandwidth excitation and monitoring the response as a function of time will greatly reduce the measurement time. The widespread usage of a square wave excitation is simple but not always the best choice. Here we consider different waveforms for excitation and discuss not only the advantages but also their limitations. Measurements in a miniaturized chamber where frequency and time domain measurements are compared show the suitability of different waveforms as excitation signals for the measurements of bio-impedance. The chirp excitation has been found to be most promising in terms of frequency range, signal-to-noise ratio and crest factor

  8. Decomposition of time-resolved tomographic PIV

    NARCIS (Netherlands)

    Schmid, P.J.; Violato, D.; Scarano, F.

    2012-01-01

    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 threedimensional flow fields have

  9. A Study of the Dynamics of the Heme Pocket and C-helix in CooA upon CO Dissociation Using Time-Resolved Visible and UV Resonance Raman Spectroscopy.

    Science.gov (United States)

    Otomo, Akihiro; Ishikawa, Haruto; Mizuno, Misao; Kimura, Tetsunari; Kubo, Minoru; Shiro, Yoshitsugu; Aono, Shigetoshi; Mizutani, Yasuhisa

    2016-08-18

    CooA is a CO-sensing transcriptional activator from the photosynthetic bacterium Rhodospirillum rubrum that binds CO at the heme iron. The heme iron in ferrous CooA has two axial ligands: His77 and Pro2. CO displaces Pro2 and induces a conformational change in CooA. The dissociation of CO and/or ligation of the Pro2 residue are believed to trigger structural changes in the protein. Visible time-resolved resonance Raman spectra obtained in this study indicated that the ν(Fe-His) mode, arising from the proximal His77-iron stretch, does not shift until 50 μs after the photodissociation of CO. Ligation of the Pro2 residue to the heme iron was observed around 50 μs after the photodissociation of CO, suggesting that the ν(Fe-His) band exhibits no shift until the ligation of Pro2. UV resonance Raman spectra suggested structural changes in the vicinity of Trp110 in the C-helix upon CO binding, but no or very small spectral changes in the time-resolved UV resonance Raman spectra were observed from 100 ns to 100 μs after the photodissociation of CO. These results strongly suggest that the conformational change of CooA is induced by the ligation of Pro2 to the heme iron. PMID:27457181

  10. Broadband dielectric spectroscopy of BPDA/ODA polyimide films

    Science.gov (United States)

    Khazaka, R.; Locatelli, M. L.; Diaham, S.; Bidan, P.; Dupuy, L.; Grosset, G.

    2013-02-01

    Dielectric spectroscopy of a high-temperature photosensitive polyimide was investigated in wide temperature and frequency ranges during heating and cooling cycles (from -150 to 370 °C and from 0.1 to 1 MHz). During the heating phase measurements two sub-glass relaxation processes were observed, noted as γ and β relaxations. The γ relaxation appears at a low temperature (around -60 °C at 1 kHz) with an activation energy of 0.44 eV during the heating phase and disappears during the cooling one, indicating that the peak is initially related to the presence of water in the polyimide films. The β relaxation appears at higher temperatures (around 180 °C at 1 kHz) with a higher activation energy of about 1.5 eV. The β peak location and intensity for low temperatures (between 100 °C and 120 °C) change slightly on comparing the heating and cooling spectra, indicating also the effect of water molecules, which may act as a plasticizer. However, for higher temperatures, the β peak does not show any significant effect of the thermal cycle, and the relaxation is mainly attributed to the non-cooperative relaxation of the polyimide molecules. The ac conductivity (σ‧) values show that the electronic hopping process is influenced by the dynamics of the segmental and macromolecular chains of the polyimide in the γ and β relaxation regions. At high temperatures (>250 °C) a plateau region appears in the ac conductivity allowing the extraction of the dc conductivity values, which are not affected between the heating and cooling measurements. This leads us to conclude that there are no significant morphological or chemical changes in the polyimide even for temperatures higher than its glass transition one under N2 for short periods. For temperatures above 300 °C an increase in the values of relative permittivity is observed and referred to the Maxwell-Wagner-Sillars or to the electrode polarization phenomena. In this range the activation energy of the polarization peak

  11. Development of a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer in resonance with transitions in the 900-1550 nm region.

    Science.gov (United States)

    Takaya, Tomohisa; Iwata, Koichi

    2016-07-21

    Charge transfer and charge delocalisation processes play key roles in the functions of large biomolecular systems and organic/inorganic devices. Many of the short-lived transients involved in these processes can be sensitively detected by monitoring their low-energy electronic transitions in the near-IR region. Ultrafast time-resolved near-IR Raman spectroscopy is a promising tool for investigating the structural dynamics of the short-lived transients as well as their electronic dynamics. In this study, we have developed a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer using the Raman pump pulse at 1190 nm and a broadband probe pulse covering the 900-1550 nm region. Spectral and temporal instrument responses of the spectrometer are estimated to be 5 cm(-1) and 120 fs, respectively. Time-resolved near-IR stimulated Raman spectra of poly(3-dodecylthiophene) (P3DDT) are recorded in toluene solution for investigating its structural changes following the photoexcitation. The spectra strongly indicate conformational changes of P3DDT in excited states associated with the elongation of its effective conjugation length. The results on P3DDT fully demonstrate the effectiveness of the newly developed femtosecond time-resolved near-IR stimulated Raman spectrometer. PMID:27327140

  12. Time-resolved photoemission using attosecond streaking

    CERN Document Server

    Nagele, Stefan; Wais, Michael; Wachter, Georg; Burgdörfer, Joachim

    2014-01-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric effect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the field-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for effective 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 $A$@$\\text{C}_{60}$ and discuss how streaking time shifts are modified due to the interaction of the $\\text{C}_...

  13. Rapid, broadband spectroscopic temperature measurement of hbox {CO}_2 using VIPA spectroscopy

    Science.gov (United States)

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

    2016-04-01

    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 (5000hbox { cm}^{-1}). The laser was passed through a 12-cm-long cell containing hbox {CO}_2, and the transmitted light was analyzed in a virtually imaged phased array-based spectrometer. Broadband spectra spanning more than 100hbox { cm}^{-1 } with a spectral resolution of roughly 0.075hbox { cm}^{-1} (2.2 GHz) were acquired with an integration period of 2 ms. The temperature of the hbox {CO}_2 sample was deduced from fitting a modeled spectrum to the line intensities of the experimentally acquired spectrum. Temperature dynamics on the timescale 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. Potential applications of this technique include quantitative measurement of carbon dioxide concentration and temperature dynamics in gas-phase chemical reactions (e.g., combustion) and plasma diagnostics.

  14. 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...

  15. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    International Nuclear Information System (INIS)

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz

  16. 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.

  17. Time-resolved UV-IR pump-stimulated emission pump spectroscopy to probe collisional relaxation of the 8p2P3/2 state of Cs I

    Science.gov (United States)

    Salahuddin, Mohammed; Arndt, Phill; McFarland, Jacob; Bayram, S. Burçin

    2015-12-01

    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 8p2P3/2 cesium atoms were produced by a pump laser. A second laser, the stimulated emission pump, promoted the population exclusively to the 5d2D5/2 level. The intensity of the 5 d 5/2 2 D → 6 s 1/2 2S cascade fluorescence at 852.12 nm was monitored. The linear polarization dependence of the 6 s 1/2 2S → 8 p 3/2 2P → 5 d 5/2 2S transition was measured in the presence of argon gas at various pressures. From the measurement, we obtained the disalignment cross sectional value for the 8p2P3/2 level due to collisions with ground-level argon atoms.

  18. Broadband cavity enhanced spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

    Science.gov (United States)

    Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Rudich, Y.; Brown, S. S.

    2015-09-01

    Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity enhanced spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99933 ± 0.00003 (670 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.49 km within the 1 m cell. We measure the cavity output over the 315-350 nm spectral region using a grating monochromator and charge-coupled device (CCD) array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity enhanced spectroscopy and cavity ringdown spectroscopy agree within 2 % (slope for linear fit = 0.98 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity enhanced spectroscopy and calculated based on flow dilution are also well-correlated, with r2 = 0.9998. During constant, mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1-min detection limit for extinction measurements at 315-350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically-based trace gas detection that may complement higher precision techniques based on non-absolute detection methods. In addition to trace gases, this approach will be appropriate for

  19. Broadband 2D electronic spectroscopy reveals a carotenoid dark state in purple bacteria.

    Science.gov (United States)

    Ostroumov, Evgeny E; Mulvaney, Rachel M; Cogdell, Richard J; Scholes, Gregory D

    2013-04-01

    Although the energy transfer processes in natural light-harvesting systems have been intensively studied for the past 60 years, certain details of the underlying mechanisms remain controversial. We performed broadband two-dimensional (2D) electronic spectroscopy measurements on light-harvesting proteins from purple bacteria and isolated carotenoids in order to characterize in more detail the excited-state manifold of carotenoids, which channel energy to bacteriochlorophyll molecules. The data revealed a well-resolved signal consistent with a previously postulated carotenoid dark state, the presence of which was confirmed by global kinetic analysis. The results point to this state's role in mediating energy flow from carotenoid to bacteriochlorophyll.

  20. Ultra-broadband infrared pump-probe spectroscopy using synchrotron radiation and a tuneable pump

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, Lee; Friedli, Peter; Stutz, Stefan; Sigg, Hans [Laboratory for Micro and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Lerch, Philippe; Schneider, Joerg; Treyer, Daniel; Hunziker, Stephan [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)

    2011-06-15

    Synchrotron infrared sources have become popular mainly because of their excellent broadband brilliance, which enables spectroscopically resolved spatial-mapping of stationary objects at the diffraction limit. In this article we focus on an often-neglected further advantage of such sources - their unique time-structure - to bring such broadband spectroscopy to the time domain, for studying dynamic phenomenon down to the 100 ps limit. We describe the ultra-broadband (12.5 to 1.1 {mu}m) Fourier transform pump-probe setup, for condensed matter transmission- and reflection-spectroscopy, installed at the X01DC infrared beam-line of the Swiss Light Source (SLS). The optical pump consists of a widely tuneable 100 ps 1 kHz laser system, covering 94% of the 16 to 1.1 {mu}m range. A thorough description of the system is given, including (i) the vector-modulator providing purely electronic tuning of the pump-probe overlap up to 1 ms with sub-ps time resolution, (ii) the 500 MHz data acquisition system interfaced with the experimental physics and industrial control system (EPICS) based SLS control system for consecutive pulse sampling, and (iii) the step-scan time-slice Fourier transform scheme for simultaneous recording of the dual-channel pumped, un-pumped, and difference spectra. The typical signal/noise ratio of a single interferogram in a 100 ps time slice is 300 (measured during one single 140 s TopUp period). This signal/noise ratio is comparable to that of existing gated Globar pump-probe Fourier transform spectroscopy, but brings up to four orders of magnitude better time resolution. To showcase the utility of broadband pump-probe spectroscopy, we investigate a Ge-on-Si material system similar to that in which optically pumped direct-gap lasing was recently reported. We show that the mid-infrared reflection-spectra can be used to determine the optically injected carrier density, while the mid- and near-infrared transmission-spectra can be used to separate the strong

  1. Ultra-broadband infrared pump-probe spectroscopy using synchrotron radiation and a tuneable pump.

    Science.gov (United States)

    Carroll, Lee; Friedli, Peter; Lerch, Philippe; Schneider, Jörg; Treyer, Daniel; Hunziker, Stephan; Stutz, Stefan; Sigg, Hans

    2011-06-01

    Synchrotron infrared sources have become popular mainly because of their excellent broadband brilliance, which enables spectroscopically resolved spatial-mapping of stationary objects at the diffraction limit. In this article we focus on an often-neglected further advantage of such sources - their unique time-structure - to bring such broadband spectroscopy to the time domain, for studying dynamic phenomenon down to the 100 ps limit. We describe the ultra-broadband (12.5 to 1.1 μm) Fourier transform pump-probe setup, for condensed matter transmission- and reflection-spectroscopy, installed at the X01DC infrared beam-line of the Swiss Light Source (SLS). The optical pump consists of a widely tuneable 100 ps 1 kHz laser system, covering 94% of the 16 to 1.1 μm range. A thorough description of the system is given, including (i) the vector-modulator providing purely electronic tuning of the pump-probe overlap up to 1 ms with sub-ps time resolution, (ii) the 500 MHz data acquisition system interfaced with the experimental physics and industrial control system (EPICS) based SLS control system for consecutive pulse sampling, and (iii) the step-scan time-slice Fourier transform scheme for simultaneous recording of the dual-channel pumped, un-pumped, and difference spectra. The typical signal/noise ratio of a single interferogram in a 100 ps time slice is 300 (measured during one single 140 s TopUp period). This signal/noise ratio is comparable to that of existing gated Globar pump-probe Fourier transform spectroscopy, but brings up to four orders of magnitude better time resolution. To showcase the utility of broadband pump-probe spectroscopy, we investigate a Ge-on-Si material system similar to that in which optically pumped direct-gap lasing was recently reported. We show that the mid-infrared reflection-spectra can be used to determine the optically injected carrier density, while the mid- and near-infrared transmission-spectra can be used to separate the strong pump

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

    International Nuclear Information System (INIS)

    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 α//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 γ//He/sub β/'' and ''He/sub δ//He/sub β/'' helium-like resonance line intensity ratios

  3. 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

  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

    -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...... 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...... and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultrabroadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science....

  5. Effects of sulfation level on the desulfation behavior of pre-sulfated Pt BaO/Al2O3 lean NOx trap catalysts: a combined H2 Temperature-Programmed Reaction, in-situ sulfur K-edge X-ray Absorption Near-Edge Spectroscopy, X-ray Photoelectron Spectroscopy, and Time-Resolved X-ray Diffraction Study

    International Nuclear Information System (INIS)

    Desulfation by hydrogen of pre-sulfated Pt(2wt%) BaO(20wt%)/Al2O3 with various sulfur loading (S/Ba = 0.12, 0.31 and 0.62) were investigated by combining H2 temperature programmed reaction (TPRX), x-ray photoelectron spectroscopy (XPS), in-situ sulfur K-edge x-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved x-ray diffraction (TR-XRD) techniques. We find that the amount of H2S desorbed during the desulfation in the H2 TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in-situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates were transformed to a BaS phase and remained in the catalyst, rather than being removed as H2S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H2S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H2O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H2S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt BaO/Al2O3 lean NOx trap catalysts is markedly dependent on the sulfation levels.

  6. Discrimination of Crude Oil Samples Using Laser-Induced Time-Resolved Fluorescence Spectroscopy%基于激光诱导时间分辨荧光的原油识别方法研究

    Institute of Scientific and Technical Information of China (English)

    韩晓爽; 刘德庆; 栾晓宁; 郭金家; 刘永信; 郑荣儿

    2016-01-01

    在柴油、汽油、重质燃料油等成品油和原油等溢油油源的区分方面 ,荧光光谱结合模式识别手段得到了广泛的应用.传统的三维荧光光谱分析方法虽然能够获得溢油样品丰富的成分信息 ,但难以适应现场应用的要求 ,目前还停留在实验室检测的阶段.发展适用于现场应用的原油识别方法 ,对于海洋溢油污染的快速响应与处理意义重大.面向激光雷达的需要 ,发展了一种基于激光诱导时间分辨荧光手段、结合支持向量机(SVM )模型的原油识别方法 ,从时间和波长两个不同维度出发 ,通过对时间窗口和波长范围的选取进行优化 ,获得了理想的油种识别准确率.实验结果表明通过选取ICCD探测延时为54~74 ns可以将分类正确率从全谱线数据的83. 3% 提高到88. 1% .通过选取波长范围为387. 00~608. 87 nm的谱线数据 ,可将疑似油种的分类正确率从全谱线数据的84% 提高到100% .激光荧光雷达在实际工作中 ,受波浪、运载平台晃动等因素的影响 ,探测延时会出现一定的波动.本文介绍的分类识别方法通过时间和波长两个维度的筛选 ,更加适用于现场探测数据的识别 ,并进一步凸显了原油时间分辨荧光光谱特征 ,为疑似油种分类识别过程中数据量的压缩提供了重要依据.%The Laser-induced fluorescence spectra combined with pattern recognition method has been widely applied in discrimi-nation of different spilled oil ,such as diesel ,gasoline ,and crude oil .However ,traditional three-dimension fluorescence analysis method ,which is not adapted to requirement of field detection ,is limited to laboratory investigatio ns .The development of oil identification method for field detection is significant to quick response and operation of oil spill .In this paper ,a new method based on laser-induced time-resolved fluorescence combined with support vector machine (SVM ) model was introduced to dis

  7. 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

  8. Time resolved super continuum Cavity Ring-Down Spectroscopy for multicomponent gas detection; Espectroscopia de cavidade ressonante tipo Ring-Down Supercontinuum resolvida no tempo para detecao de multicomponentes gasosos

    Energy Technology Data Exchange (ETDEWEB)

    Nakaema, Walter Morinobu

    2010-07-01

    In this work, we present a variation of the technique CRDS (Cavity Ring-Down Spectroscopy) to obtain simultaneously a multicomponent absorption spectrum in a broad visible range. This new approach uses the Supercontinuum (SC) spectrum (resulting from irradiation of nonlinear media by femtosecond lasers, or simply generated by compact sources) as a light source to illuminate the cavity. In this context it is described the features of the modules assembling a MC-SC-CRDS (Multicomponent Supercontinuum Cavity Ring-Down Spectroscopy): a set of high reflectivity mirrors, the resonant cavity and the detection system. Some problems related to the multimode excitation, stray light, effective use of the dynamic range of the detector, the poor resolution of the instrument to resolve narrow absorption lines are issued. We present the absorption spectra of H{sub 2}O (polyads 4{upsilon}, 4{upsilon} + {delta}) and O{sub 2} (spin-forbidden b-X branch) measured simultaneously by this technique in the visible range and a comparison with the absorption lines based on HITRAN database is made to demonstrate the functionality of this method. (author)

  9. Some Signal Processing Techniques for Use in Broadband Time Domain Microwave Spectroscopy

    Science.gov (United States)

    Cooke, S. A.

    2016-06-01

    At the present time, in the typical broadband, time domain microwave spectroscopy experiment each free induction decay (FID) collected is on the order of 10^6 data points in length with a sampling rate on the order of 10-12 seconds per point. Traditionally, the FID is processed using a fast Fourier transform algorithm (FFT) with the resulting power spectrum used in ensuing spectral analyses. For use with the FFT algorithm we have implemented some pre- and post-processing techniques to improve the signal quality. These techniques include the use of Lissajous plots to ensure phase stability in signal addition, novel windowing functions, and also automated broadband phase corrections which allow the absorption spectrum to be used as a more highly resolved version of the traditional power spectrum (see figure). We have also implemented alternatives to the FFT algorithm for time domain signal processing including Hankel singular valued decomposition, a maximum entropy method, and wavelet transformations. Although these techniques are unlikely to be used in place of a fast Fourier transform we will demonstrate how each of these techniques may be used to augment the traditional FFT algorithm in regards to spectral analysis.

  10. 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. PMID:26261063

  11. Advances in Low-Frequency 3-color Broadband Coherent Raman Spectroscopy of Condensed Phase Samples

    Science.gov (United States)

    Ujj, Laszlo

    2016-05-01

    Low-frequency dispersive spontaneous Raman spectroscopy is a very useful method to measure phonon frequencies in crystals or characterize collective vibrational motions of macromolecules. The coherent version of the method has not been fully explored yet. It is shown here that the 3-color Broadband Coherent Raman scattering can be a very powerful extension to not only gas phase but condensed phase low frequency (5-500 cm-1) vibrational measurements with large frequency separation between the narrowband and broadband radiation generating the signal. The spectral measurements presented here used volumetric Brag filters for the first time to record coherent Raman spectra. Specific spectral analysis using model independent methods to derive the vibrational information is also presented. The technic can be extended to measure electronic resonance enhanced spectra by tuning only the frequency of the narrowband laser close to the electronic transition frequencies. This makes the method suitable for coherent Raman microscopy. The polarization properties of the signal is also explained and experimentally verified. Financial support from the College of Sciences and Engineering of UWF is acknowledged.

  12. Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS – applicability and corrections

    Directory of Open Access Journals (Sweden)

    D. Pöhler

    2009-11-01

    Full Text Available Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broadband light sources, the broadband CEAS (BB-CEAS. BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light path by the trace gas absorption, since cavity losses due to absorption by gases reduce the quality (Q of the cavity. In fact, at wavelength, where the quality of the BB-CEAS cavity is dominated by the trace gas absorption (especially at very high mirror reflectivity, the average light path will vary nearly inversely with the trace gas concentration and the strength of the band will become only weakly dependent on the trace gas concentration c in the cavity, (the differential optical density being proportional to the logarithm of the trace gas concentration. Only in the limiting case where the mirror reflectivity determines Q at all wavelength, the strength of the band as seen by the CE-DOAS instrument becomes directly proportional to the concentration c. We investigate these relationships in detail and present methods to correct for the cases between the two above extremes, which are of course the important ones in practice.

  13. Enzyme reactions and their time resolved measurements

    International Nuclear Information System (INIS)

    This paper discusses experimental strategies in data collection with the Laue method and summarises recent results using synchrotron radiation. Then, an assessment is made of the progress towards time resolved studies with protein crystals and the problems that remain. The paper consists of three parts which respectively describe some aspects of Laue diffraction, recent examples of structural results from Laue diffraction, and kinetic Laue crystallography. In the first part, characteristics of Laue diffraction is discussed first, focusing on the harmonics problems, spatials problem, wavelength normalization, low resolution hole, data completeness, and uneven coverage of reciprocal space. Then, capture of the symmetry unique reflection set is discussed focusing on the effect of wavelength range on the number of reciprocal lattice points occupying diffracting positions, effect of crystal to film distance and the film area and shape on the number of reflections captured, and effect of crystal symmetry on the number of unique reflections within the number of reflections captured. The second part addresses the determination of the structure of turkey egg white lysozyme, and calcium binding in tomato bushy stunt virus. The third part describes the initiation of reactions in enzyme crystals, picosecond Laue diffraction at high energy storage rings, and detectors. (N.K.)

  14. Glassy dynamics and physical aging in fucose saccharides as studied by infrared- and broadband dielectric spectroscopy.

    Science.gov (United States)

    Kossack, Wilhelm; Adrjanowicz, Karolina; Tarnacka, Magdalena; Kipnusu, Wycliffe Kiprop; Dulski, Mateusz; Mapesa, Emmanuel Urandu; Kaminski, Kamil; Pawlus, Sebastian; Paluch, Marian; Kremer, Friedrich

    2013-12-21

    Fourier Transform Infra Red (FTIR) and Broadband Dielectric Spectroscopy (BDS) are combined to study both the intra- and inter-molecular dynamics of two isomers of glass forming fucose, far below and above the calorimetric glass transition temperature, T(g). It is shown that the various IR-active vibrations exhibit in their spectral position and oscillator strength quite different temperature dependencies, proving their specific signature in the course of densification and glass formation. The coupling between intra- and inter molecular dynamics is exemplified by distinct changes in IR active ring vibrations far above the calorimetric glass transition temperature at about 1.16T(g), where the dynamic glass transition (α relaxation) and the secondary β relaxation merge. For physically annealed samples it is demonstrated that upon aging the different moieties show characteristic features as well, proving the necessity of atomistic descriptions beyond coarse-grained models.

  15. 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....

  16. Broadband 2D Electronic Spectroscopy Reveals Coupling Between Dark 1Bu- State of Carotenoid and Qx State of Bacteriochlorophyll

    Directory of Open Access Journals (Sweden)

    Scholes Gregory D.

    2013-03-01

    Full Text Available The study of LH2 protein of purple bacteria by broadband 2D electronic spectroscopy is presented. The dark 1Bu- carotenoid state is directly observed in 2D spectra and its role in carotenoid-bacteriochlorophyll interaction is discussed.

  17. Experimental validation of the use of Kramers-Kronig relations to eliminate the phase sheet ambiguity in broadband phase spectroscopy.

    Science.gov (United States)

    Trousil, R L; Waters, K R; Miller, J G

    2001-05-01

    The technique of broadband phase spectroscopy proposed in 1978 by Sachse and Pao [J. Appl. Phys. 49, 4320-4327 (1978)] determines the phase velocity as a function of frequency from the Fourier transforms of a received reference and through-sample signal. Although quite successful, this approach can be influenced by an ambiguity in the phase velocity calculation which stems from the boundedness of the inverse tangent operation used to calculate phase. Several empirical approaches to resolve the phase ambiguity have been reported. An alternative approach that has not previously been considered appeals to the causal nature of the measurements. This article experimentally validates a method which uses the causally consistent Kramers-Kronig relations to eliminate the ambiguity in phase spectroscopy-derived phase velocity calculations. Broadband pulse and narrow-band tone burst measurements were performed on three gelatin-based phantoms containing different concentrations of graphite particles (0%, 10%, and 20% by volume). The phantoms were constructed to have attenuation coefficients which vary approximately linear-with-frequency, a dependence exhibited by many soft tissues. The narrow-band phase velocity measurements do not suffer from a phase ambiguity, and thus they serve as a "gold standard" against which the broadband phase velocity measurements are compared. The experimental results illustrate that using the Kramers-Kronig dispersion relations in conjunction with phase spectroscopy-derived phase velocity measurements is an effective means by which to resolve the phase sheet ambiguity in broadband phase spectroscopy.

  18. Radiationless S 1 → S 0 phenyl deactivation pathway: an investigation of iodine-marked bi-phenyl on a silicon surface by means of time resolved core-level photoelectron spectroscopy

    Science.gov (United States)

    Michelswirth, Martin; Dachraoui, Hatem; Mattay, Jochen; Heinzmann, Ulrich

    2012-02-01

    The S 1 → S 0 radiationless deactivation of iodine terminated bi-phenyl immobilized on a silicon surface was probed by analysing the I4d signature (BE: 45.6 eV, 47.3 eV) by means of High Harmonic Generation (HHG) based photoelectron spectroscopy. Modifications of the 4d5/2,3/2 spectroscopic contents spanning about 0.2 ps after UV activation (266 nm) were verified as showing a transient molecular response character. A localization to the terminated phenyl substructure in the complex structural environment on the surface was ensured according to the core-level nature of the recorded I4d. The activation of the bi-phenyl achieved by UV irradiation, corresponding to the UV absorption band-edge, was verified as being dominated by a Bπ → Bπ* phenyl excitation. Time-Dependent Density Functional Theory (TD-DFT) modellings were therefore performed. They were matched to Configuration Interaction semi-empirical calculations (CI-MNDO) verifying the Rustagi-Ducuing relation. The simulated singlet-singlet excitation spectrum was referenced to the spectra of an iodine terminated monomer and a linear oligophenyl chain (N = 8). Thus the deactivation response studied was assigned to a conical intersection promoted ? reaction pathway.

  19. Study of broadband THz time-domain spectroscopy at different relative humidity levels

    Institute of Scientific and Technical Information of China (English)

    Chiajen Lin; Ichen Ho; X. C. Zhang

    2012-01-01

    Two detection techniques of broadband terahertz (THz) time-domain spectroscopy-THz air-biased coherent detection (THz-ABCD; from 0.3 to 14 THz) and electro-optical (EO) detection (from 0.3 to 7 THz) - are both performed at several different relative humidity levels.The THz power exponentially decays with the increase in relative humidity.The dynamic range of the main pulse in the time domain linearly decreases as the relative humidity increases from 0% to 40%,and linear fittings show that the slopes are -0.017 and -0.019 for THz-ABCD and EO detection,respectively.Because of the multiple reflections caused by the crystal in the common EO detection,THz-ABCD has better spectral resolution (17 GHz) than that of EO detection (170 GHz).The spectrum of water vapor absorption measured by THz-ABCD is also compared with that measured by the Fourier transform infrared spectroscopy (FTIR).

  20. Continuous-wave 1.55 $\\mu$m diode-pumped surface emitting semiconductor laser for broadband multiplex spectroscopy

    CERN Document Server

    Jacquemet, M; Guelachvili, G; Picqué, N; Sagnes, I; Strassner, M; Symonds, C; Garnache, Arnaud; Guelachvili, Guy; Jacquemet, Mathieu; Picqu\\'{e}, Nathalie; Sagnes, Isabelle; Strassner, Martin; Symonds, Cl\\'{e}mentine

    2007-01-01

    A room temperature operating Vertical External Cavity Surface Emitting Laser is applied around 1550 nm to intracavity laser absorption spectroscopy analyzed by time-resolved Fourier transform interferometry. At an equivalent pathlength of 15 km, the high resolution spectrum of the semiconductor disk laser emission covers 17 nm simultaneously. A noise equivalent absorption coefficient at one second averaging equal to 1.5 10^{-10} cm^{-1}.Hz^{-1/2} per spectral element is reported for the 65 km longest path length employed.

  1. Time-resolved spectroscopy in the Rijnhuizen Tokamak Project tokamak

    NARCIS (Netherlands)

    Box, F. M. A.; Howard, J.; VandeKolk, E.; Meijer, F. G.

    1997-01-01

    At the Rijnhuizen Tokamak Project tokamak spectrometers are used to diagnose the velocity distribution and abundances of impurity ions. Quantities can be measured as a function of time, and the temporal resolution depends on the line emissivity and can be as good as 0.2 ms for the strongest lines. S

  2. 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...

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

    DEFF Research Database (Denmark)

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

    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...

  4. Time-resolved spectroscopy in the Rijnhuizen Tokamak Project tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Box, F.M.A.; Kolk, E. van de [Associatie Euratom-FOM, Nieuwegein (Netherlands). FOM-Instituut voor Plasmafysica; Howard, J. [Plasma Research Laboratory, Research School of Physical Science and Engineering, Australian National University, Canberra 0200 (Australia); Meijer, F.G. [Physics Faculty, University of Amsterdam, Amsterdam (Netherlands)

    1997-03-01

    At the Rijnhuizen Tokamak Project tokamak spectrometers are used to diagnose the velocity distribution and abundances of impurity ions. Quantities can be measured as a function of time, and the temporal resolution depends on the line emissivity and can be as good as 0.2 ms for the strongest lines. Several spectrometers, equipped with a charge-coupled device array, are being used with spectral ranges in the visible, the vacuum UV and the extreme UV. (orig.)

  5. Time-Resolved Remote Raman Spectroscopy for Venus Exploration

    Science.gov (United States)

    Sharma, S. K.; Misra, A. K.; Acosta-Maeda, T. E.; Dyer, M. D.; Clegg, S. M.; Wiens, R. C.

    2015-04-01

    We describe a compact gatable planetary Raman spectrograph developed at the University of Hawaii that is suitable for detecting low concentrations of relevant minerals in a basaltic glass matrix on the Venus surface from a lander.

  6. Resonant and time-resolved spin noise spectroscopy

    Science.gov (United States)

    Pursley, Brennan C.; Song, X.; Sih, V.

    2015-11-01

    We demonstrate a method to extend the range of pulsed laser spin noise measurements to long spin lifetimes. We use an analog detection scheme with a bandwidth limited only by laser pulse duration. Our model uses statistics and Bloch-Torrey equations to extract the Lande g-factor, Faraday cross-section σ F , and spin lifetime τ s , while accounting for finite detector response. Varying the magnetic field with a fixed probe-probe delay yields τ s when it is longer than the laser repetition period. Varying the probe-probe delay with a fixed field produces a time-domain measurement of the correlation function.

  7. A time-resolved fluorescence study of matrix-isolated Ag 2

    Science.gov (United States)

    Hebert, T.; Kolb, D. M.; Rotermund, H. H.; Schriever, U.; Wiggenhauser, H.

    1990-02-01

    The nanosecond lifetimes of the A, B and C states of Ag 2 in Ar, Kr and Xe matrices were determined by time-resolved emission spectroscopy. From an analysis of the rise and decay times after pulsed optical excitation, the non-radiative relaxation channel between the B and A states was quantitatively established.

  8. 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.

  9. Blend uniformity analysis of pharmaceutical products by Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS).

    Science.gov (United States)

    Fitzpatrick, Dara; Scanlon, Eoin; Krüse, Jacob; Vos, Bastiaan; Evans-Hurson, Rachel; Fitzpatrick, Eileen; McSweeney, Seán

    2012-11-15

    Blend uniformity analysis (BUA) is a routine and highly regulated aspect of pharmaceutical production. In most instances, it involves quantitative determination of individual components of a blend in order to ascertain the mixture ratio. This approach often entails the use of costly and sophisticated instrumentation and complex statistical methods. In this study, a new and simple qualitative blend confirmatory test is introduced based on a well known acoustic phenomenon. Several over the counter (OTC) product powder blends are analysed and it is shown that each product has a unique and highly reproducible acoustic signature. The acoustic frequency responses generated during the dissolution of the product are measured and recorded in real time. It is shown that intra-batch and inter-batch variation for each product is either insignificant or non-existent when measured in triplicate. This study demonstrates that Broadband Acoustic Resonance Dissolution Spectroscopy or BARDS can be used successfully to determine inter-batch variability, stability and uniformity of powder blends. This is just one application of a wide range of BARDS applications which are more cost effective and time efficient than current methods.

  10. Broadband Infrared Spectroscopy of Vanadium Dioxide Films Under the Influence of Strain

    Science.gov (United States)

    Huffman, T. J.; Xu, Peng; Hollingshad, A. J.; Penthorn, N. E.; Brooker, D. J.; Qazilbash, M. M.; Wang, Lei; Lukaszew, R. A.; Pike, R. D.; Kim, B.-J.; Kim, H.-T.

    2013-03-01

    Vanadium dioxide (VO2) undergoes a phase transition between an insulating monoclinic phase and a conducting rutile phase. Even in this simple, stoichiometric material, a complete explanation of the phase transition has proved elusive. This transition, like phase transitions in other correlated electron systems, involves interacting electronic, lattice, and orbital degrees of freedom. This leads to physical properties that are particularly sensitive to small changes in external parameters such as strain. VO2films grown on different substrates are subject to differing strain effects that often lead to a shift in the transition temperature. Broadband infrared (IR) and optical spectroscopy allows us to examine the electronic structure and dynamics as well as IR-active, zone-center phonons of strained films grown on sapphire and quartz. Comparing and contrasting the IR and optical properties of these films, and those of bulk crystals, will provide insight into the influence of strain on the electronic and lattice degrees of freedom. MMQ gratefully acknowledges support from the Jeffress Memorial Trust

  11. 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.

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

    Institute of Scientific and Technical Information of China (English)

    U. Sailaja; M. Shahin Thayyil; N.S. Krishna Kumar; G. Govindaraj

    2016-01-01

    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 per-formed after its vitrification by fast cooling from a few degrees above the melting point (Tm ¼ 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.

  13. The σ-hole interaction between sulfur hexafluoride and ammonia characterised by broadband rotational spectroscopy.

    Science.gov (United States)

    Bittner, Dror M; Zaleski, Daniel P; Stephens, Susanna L; Walker, Nicholas R; Legon, Anthony C

    2015-08-24

    A weakly-bound complex of SF6 and NH3 is generated within an expanding gas jet and characterised by broadband rotational spectroscopy. The spectra of isotopologues (32) SF6 ⋅⋅⋅(14) NH3 , (32) SF6 ⋅⋅⋅(14) ND3 , (32) SF6 ⋅⋅⋅(15) NH3 and (34) SF6 ⋅⋅⋅(15) NH3 are observed and assigned to determine the spectroscopic parameters. These parameters are consistent with the complex having a C3v symmetric rotor geometry, in which the nitrogen atom of NH3 coordinates to SF6 such that the C3v axis of the NH3 sub-unit is aligned with a local C3 axis on the SF6 sub-unit. The geometry of the complex is rationalized in terms of a σ-hole interaction. The observed spectra and ab initio calculations also reveal evidence of internal dynamics involving internal rotation of one monomer sub-unit with respect to the other about the symmetry axis of the complex. PMID:26175274

  14. Vibrational dynamics of aqueous hydroxide solutions probed using broadband 2DIR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Aritra [Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637 (United States); Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Tokmakoff, Andrei, E-mail: tokmakoff@uchicago.edu [Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637 (United States)

    2015-11-21

    We employed ultrafast transient absorption and broadband 2DIR spectroscopy to study the vibrational dynamics of aqueous hydroxide solutions by exciting the O–H stretch vibrations of the strongly hydrogen-bonded hydroxide solvation shell water and probing the continuum absorption of the solvated ion between 1500 and 3800 cm{sup −1}. We observe rapid vibrational relaxation processes on 150–250 fs time scales across the entire probed spectral region as well as slower vibrational dynamics on 1–2 ps time scales. Furthermore, the O–H stretch excitation loses its frequency memory in 180 fs, and vibrational energy exchange between bulk-like water vibrations and hydroxide-associated water vibrations occurs in ∼200 fs. The fast dynamics in this system originate in strong nonlinear coupling between intra- and intermolecular vibrations and are explained in terms of non-adiabatic vibrational relaxation. These measurements indicate that the vibrational dynamics of the aqueous hydroxide complex are faster than the time scales reported for long-range transport of protons in aqueous hydroxide solutions.

  15. Vibrational dynamics of aqueous hydroxide solutions probed using broadband 2DIR spectroscopy

    International Nuclear Information System (INIS)

    We employed ultrafast transient absorption and broadband 2DIR spectroscopy to study the vibrational dynamics of aqueous hydroxide solutions by exciting the O–H stretch vibrations of the strongly hydrogen-bonded hydroxide solvation shell water and probing the continuum absorption of the solvated ion between 1500 and 3800 cm−1. We observe rapid vibrational relaxation processes on 150–250 fs time scales across the entire probed spectral region as well as slower vibrational dynamics on 1–2 ps time scales. Furthermore, the O–H stretch excitation loses its frequency memory in 180 fs, and vibrational energy exchange between bulk-like water vibrations and hydroxide-associated water vibrations occurs in ∼200 fs. The fast dynamics in this system originate in strong nonlinear coupling between intra- and intermolecular vibrations and are explained in terms of non-adiabatic vibrational relaxation. These measurements indicate that the vibrational dynamics of the aqueous hydroxide complex are faster than the time scales reported for long-range transport of protons in aqueous hydroxide solutions

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

    Science.gov (United States)

    Bellizzi, G.; Bucci, O. M.; Capozzoli, A.

    2010-10-01

    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.

  17. 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.

  18. Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS – applicability and corrections

    Directory of Open Access Journals (Sweden)

    D. Pöhler

    2008-12-01

    Full Text Available Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broad band light sources, the broad-band CEAS (BB-CEAS. BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light path by the trace gas absorption, since cavity losses due to absorption by gases reduce the quality (Q of the cavity. In fact, at wavelength, where the quality of the BB-CEAS cavity is dominated by the trace gas absorption (esp. at very high mirror reflectivity, the light path will vary inversely with the trace gas concentration and the strength of the band will become nearly independent of the trace gas concentration c in the cavity, rendering the CEAS Method useless for trace gas measurements. Only in the limiting case where the mirror reflectivity determines Q at all wavelength, the strength of the band as seen by the BB-CEAS instrument becomes proportional to the concentration c. We investigate these relationships in detail and present methods to correct for the cases between the two above extremes, which are of course the important ones in practice.

  19. Advances in ultrafast time resolved fluorescence physics for cancer detection in optical biopsy

    Directory of Open Access Journals (Sweden)

    R. R. Alfano

    2012-03-01

    Full Text Available We discuss the use of time resolved fluorescence spectroscopy to extract fundamental kinetic information on molecular species in tissues. The temporal profiles reveal the lifetime and amplitudes associated with key active molecules distinguishing the local spectral environment of tissues. The femtosecond laser pulses at 310 nm excite the tissue. The emission profile at 340 nm from tryptophan is non-exponential due to the micro-environment. The slow and fast amplitudes and lifetimes of emission profiles reveal that cancer and normal states can be distinguished. Time resolved optical methods offer a new cancer diagnostic modality for the medical community.

  20. Time-resolved pulsed EPR: microwave and optical detection

    Energy Technology Data Exchange (ETDEWEB)

    Trifunac, A.D.; Smith, J.P.

    1981-01-01

    Time-resolved pulsed EPR spectrometers are described. EPR spectra, kinetic profiles, and relaxation studies are used to illustrate some capabilities of the pulsed EPR experiment. Optical detection of time-resolved EPR spectra of radical ion pairs is used to study radical-ion recombination kinetics, recombination pathways, and the structure of radical anions and cations. 17 figures.

  1. Time-resolved pulsed EPR: microwave and optical detection

    International Nuclear Information System (INIS)

    Time-resolved pulsed EPR spectrometers are described. EPR spectra, kinetic profiles, and relaxation studies are used to illustrate some capabilities of the pulsed EPR experiment. Optical detection of time-resolved EPR spectra of radical ion pairs is used to study radical-ion recombination kinetics, recombination pathways, and the structure of radical anions and cations. 17 figures

  2. Time resolved excitation dynamics in emeraldine base

    Energy Technology Data Exchange (ETDEWEB)

    Menšík, Miroslav, E-mail: mensik@imc.cas.cz; Rais, David; Pfleger, Jiří

    2015-07-29

    Highlights: • fs-transient absorption spectra of emeraldine base of polyaniline pumped at 700 nm. • Kinetic master equations for experimental data. • Formation of charge transfer states within 50 fs. Non-radiative decay (0.5 ps). • Phenyl rings relaxation (2.1 ps). • Formation of long-lived polarons (∼ns). - Abstract: Using femtosecond pump–probe transient absorption spectroscopy (wavelengths 330–800 nm), we observed and explained excited state, charge transfer and polaron state dynamics in emeraldine base form of polyaniline in dimethyl sulfoxide solution. The excited state created by a pump pulse (700 nm) in the quinoid absorption Q-band loses its initial symmetry by subsequent energy transition to a charge transfer state within 50 fs. The hot charge transfer state either recombines non-radiatively into the ground state with decay time constant 0.55 ps or transfers into a relaxed state corresponding to the relaxed phenyl geometry during ca 2.1 ps. This relaxed state shows a prolonged lifetime of about 6.5 ps before its recombination to the ground state. However, a small amount of long-lived polarons with lifetime of about 2 ns in air and with lifetime longer than 6 ns in the solution bubbled with dry N{sub 2} was detected.

  3. 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...... 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....

  4. Adsorption of cytochrome c to silica surfaces studied using evanescent wave broadband cavity-enhanced absorption spectroscopy

    Science.gov (United States)

    Moore, L. J.; van der Sneppen, L.; Peverall, R.; Hancock, G.; Ritchie, G. A. D.

    2010-08-01

    The adsorption of cytochrome c (cyt c) to a silica surface has been studied by use of evanescent wave broadband cavityenhanced absorption spectroscopy (EW-BBCEAS). Visible radiation from a supercontinuum source is coupled into an optical cavity consisting of a pair of broadband high reflectivity mirrors, and a total internal reflection (TIR) event at the prism/water interface. Aqueous solutions of cyt c are placed onto the TIR footprint on the prism surface and the subsequent protein adsorption is probed by the resulting evanescent wave. The time integrated cavity output is directed into a spectrometer, where it is dispersed and analysed. The high spectral brilliance of the SC affords a baseline noise comparable to evanescent wave cavity ring-down spectroscopy (EW-CRDS), and the broadband nature of the source allows observation of a wide spectral range (ca 250 nm in the visible). The system is calibrated by measuring the absorption spectra of dyes of a known absorbance. Absorption spectra of cyt c are obtained for both S and P polarized radiation, allowing information about the orientation of the adsorbed protein to be extracted.

  5. Time-resolved scanning tunnelling microscopy for molecular science

    International Nuclear Information System (INIS)

    Time-resolved scanning tunnelling microscopy (STM) and its application in molecular science are reviewed. STM can image individual atoms and molecules and thus is able to observe the results of molecular processes such as diffusion, desorption, configuration switching, bond-breaking and chemistry, on the atomic scale. This review will introduce time-resolved STM, its experimental limitations and implementations with particular emphasis on thermally activated and tunnelling current induced molecular processes. It will briefly examine the push towards ultrafast imaging. In general, results achieved by time-resolved STM demonstrate the necessity of both space and time resolution for fully characterizing molecular processes on the atomic scale.

  6. 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.

  7. 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

  8. Time-resolved luminescence studies of Eu3+ in soda-lime silicate glasses

    International Nuclear Information System (INIS)

    Soda-lime glasses doped with Eu3+ were synthesized using a variety of compositions, namely changing the fraction of CaO or Eu2O3. Those glasses were characterized with several techniques, including ellipsometry, UV–vis–NIR absorption spectroscopy, steady-state photoluminescence spectroscopy and time-resolved luminescence. The compositions' effects on optical properties such as refraction indexes, Eu3+ oscillator strengths and luminescence lifetimes were accessed from the analysis of the experimental results. Judd–Ofelt theory was used to analyze all these aspects, which allow the detection of a mismatch of optical properties from absorption and emission spectroscopy. This mismatch was confirmed from the time-resolved data, showing the existence of two different spectroscopic Eu3+ species. From those results it is concluded that there is evidence for lanthanide aggregation, giving rise to self-quenching effects that may be described through resonance energy transfer mechanisms. The difference between luminescence lifetimes for isolated and aggregated Eu(III) is interpreted as due to different interactions with oxygen in the matrix, namely degree of covalency of the Eu–O bond and point group symmetry of the lanthanide. -- Highlights: • Time resolved luminescence studies of Eu(III) in soda-lime silicate glass show the existence of two different species. • Mismatch of Judd–Ofelt parameters are obtained from absorption and emission spectroscopy. • Eu(III) has less clustering tendency when Eu2O3 concentration decreases and when CaO concentration increases

  9. Chain Dynamics in Solid Polymers and Polymerizing Systems as Revealed by Broadband Dielectric Spectroscopy

    Science.gov (United States)

    Williams, Graham

    2008-08-01

    A number of techniques are used to study the chain-dynamics of solid polymers, including those of dielectric relaxation [1-4], dynamic mechanical thermal analysis (DMTA) [1, 5], multinuclear NMR relaxations [6], quasi-elastic dynamic light scattering [7] and neutron scattering [8] (QELS & QENS) and transient fluorescence depolarization (TFD) [9]. Each technique has its own particular probe of the dynamics in a material. e.g. dielectric relaxation gives information on the angular motions of molecular chain-dipoles (for dipole relaxation) and the translational motions of ions (for f-dependent electrical conduction); NMR relaxations relate to the angular motions of chemical bonds; QELS relates to fluctuations in local refractive index; QENS to the time-dependent van Hove correlation function (suitably-defined) for proton-containing groups; TFD to the angular motions of fluorescent groups in a chain. Due to its relevance to practical applications of materials, DMTA is pre-eminent among the many physical techniques applied to solid polymers, but interpretations of behaviour in terms of molecular properties remain difficult since the direct link between an applied macroscopic stress and the molecular response of polymer chains in a bulk material remains an unsolved problem. Of the above techniques, Broadband Dielectric Spectroscopy (BDS) offers several advantages. (a) Materials may be studied in the frequency range 10-6 to 1010 Hz, over wide ranges of temperature and applied pressure, using commercially-available instrumentation. (b) Since the electrical capacitance of a film is inversely proportional its thickness, free-standing and supported films may be studied down to nm-thicknesses, giving e.g. information on the behaviour of the dynamic Tg as sample thickness approaches molecular dimensions. (c) Theoretical interpretations of dielectric relaxation and a.c. conduction are well-established in terms of Fourier transforms of molecular time correlation functions (TCFs

  10. Time-resolved study of Higgs mode in superconductors

    Science.gov (United States)

    Shimano, Ryo

    The behavior of superconductors far from equilibrium has been intensively studied over decades. Goals of these studies are the elucidation of bosonic fluctuations essential for the pairing mechanisms, the manifestation of competing orders or hidden phases, and the optical manipulation of superconductivity. The study of collective modes is crucially important for these perspectives as it provides the information on the dynamics of order parameters in non-equilibirium states. Generally, collective modes in ordered phases associated with spontaneous symmetry breaking are classified into 1) gapless phase modes and 2) gapped amplitude modes. In superconductors, the phase mode is eaten by gauge field, according to the Anderson-Higgs mechanism. The remaining amplitude mode is recently termed as Higgs mode from its analogy to the Higgs boson in particle physics. Despite its long history of investigation, unambiguous observation of Higgs mode has remained elusive. This is because the Higgs mode does not have a charge nor electric dipole and therefore it does not couple directly to the electromagnetic field. Here we report on our recent observation of Higgs mode in s-wave superconductors by using THz-pump and THz-probe spectroscopy technique. After nonadiabatic excitation near the superconducting gap energy with monocycle THz pulses, Higgs mode was observed as oscillations in the transmission of THz probe pulse. The resonant nonlinear coupling between the Higgs mode and coherent radiation field was also discovered, resulting in an efficient third order harmonic generation of the incident THz radiation. The extension of experiments to multiband superconductors and unconventional superconductors will be discussed. Time-resolved study of Higgs mode in superconductors.

  11. Time resolved studies of bond activation by organometallic complexes

    Energy Technology Data Exchange (ETDEWEB)

    Wilkens, M J [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1998-05-01

    In 1971, Jetz and Graham discovered that the silicon-hydrogen bond in silanes could be broken under mild photochemical conditions in the presence of certain transition metal carbonyls. Such reactions fall within the class of oxidative addition. A decade later, similar reactivity was discovered in alkanes. In these cases a C-H bond in non-functionalized alkanes was broken through the oxidative addition of Cp*Ir(H){sub 2}L (Cp* = (CH{sub 3}){sub 5}C{sub 5}, L = PPh{sub 3}, Ph = C{sub 6}H{sub 5}) to form Cp*ML(R)(H) or of Cp*Ir(CO){sub 2} to form Cp*Ir(CO)(R)(H). These discoveries opened an entirely new field of research, one which naturally included mechanistic studies aimed at elucidating the various paths involved in these and related reactions. Much was learned from these experiments but they shared the disadvantage of studying under highly non-standard conditions a system which is of interest largely because of its characteristics under standard conditions. Ultrafast time-resolved IR spectroscopy provides an ideal solution to this problem; because it allows the resolution of chemical events taking place on the femto-through picosecond time scale, it is possible to study this important class of reactions under the ambient conditions which are most of interest to the practicing synthetic chemist. Certain of the molecules in question are particularly well-suited to study using the ultrafast IR spectrophotometer described in the experimental section because they contain one or more carbonyl ligands.

  12. Real-time observation of vibrational quantum beat in condensed phase by 20 fs time-resolved spectroscopy%凝聚相分子振动量子拍的20fs时间分辨光谱实时观测

    Institute of Scientific and Technical Information of China (English)

    王云鹏; 王专; 翁羽翔

    2012-01-01

    Impulsive coherent vibrational spectroscopy is a kind of time-resolved spectroscopy methodology with a pulse duration of the femtosecond laser shorter than the molecular vibrational period. Usually, it is based on pump-probe technique and is utilized to real-time observation of the molecular vibrational dynamics coupled to the electronic ground or excited state. We have built an impulsive coherent vibrational spectroscopy setup based on a sub-20 fs, 550 to 700 nm tunable non-collinear optical parametric amplifier and performed pump-probe experiment with an Oxazine 720 methanol solution as the sample. Two vibrational quantum beats with frequency of 592 and 678 cm-1 were observed and the corresponding vibrational periods are 56.3 and 49.2 fs respectively.%冲击相干振动光谱是以脉冲宽度比分子振动周期短的飞秒激光作为激发光源的一种光谱学实验方法,通常是以泵浦-探测实验装置为基础,可以实时观测与电子基态或激发态相耦合的分子振动动力学过程.中国科学院物理研究所以小于20 fs,550~700 nm光谱范围内可调谐的非共线光参量放大器为光源,建立了一套冲击相干振动光谱学实验装置,并以染料分子Oxazine 720的甲醇溶液为样品进行了实验测试.实验中样品被泵浦光脉冲激发后在电子基态形成振动波包,并观测到振动波包在电子势能曲面上运动所形成的振动量子拍信号.经分析有两个分子振动模式被激发,其振动频率分别为592与678cm-1,所对应的振动周期分别为56.3与49.2 fs.

  13. Broadband terahertz time-domain spectroscopy of ferroelectric LiTaO{sub 3}: Phonon-polariton dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Seiji, E-mail: kojima@bk.tsukuba.ac.jp; Mori, Tatsuya, E-mail: kojima@bk.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)

    2014-11-05

    The lowest frequency IR active A{sub 1}(z) and E(x) modes of a ferroelectric congruent lithium tantalate crystal were studied by the broadband polarized Terahertz Time-Domain Spectroscopy using the coherent THz radiation from 0.2 to 6.5 THz. The dispersion relations of the real and imaginary parts of a polariton wave vector were determined from the complex extraordinary and ordinary refractive indices for the A{sub 1}(z) and E(x) symmetry phonon-polaritons, respectively. The observed complex dispersion relations of two symmetries are in agreement within the experimental uncertainty with the calculated dispersion curves by the damped harmonic oscillator model.

  14. Broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

    Science.gov (United States)

    Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Zarzana, K. J.; Rudich, Y.; Brown, S. S.

    2016-01-01

    Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and it strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99930 ± 0.00003 (1- reflectivity = 700 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.43 km within the 1 m cell. We measure the cavity output over the 315-350 nm spectral region using a grating monochromator and charge-coupled device array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity-enhanced absorption spectroscopy and cavity ring-down spectroscopy agree within 2 % (slope for linear fit = 1.02 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity-enhanced absorption spectroscopy and calculated based on flow dilution are also well correlated, with r2 = 0.9998. During constant mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1 min detection limit for extinction measurements at 315-350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically based trace gas detection that may complement higher precision techniques based on non-absolute detection methods. In addition to

  15. Alteration of time-resolved autofluorescence properties of rat aorta, induced by diabetes mellitus

    Science.gov (United States)

    Uherek, M.; Uličná, O.; Vančová, O.; Muchová, J.; Ďuračková, Z.; Šikurová, L.; Chorvát, D.

    2016-10-01

    Changes in autofluorescence properties of isolated rat aorta, induced by diabetes mellitus, were detected using time-resolved fluorescence spectroscopy with pulsed ultraviolet (UV) laser excitation. We demonstrated that time-resolved spectroscopy was able to detect changes in aorta tissues related to diabetes and unambiguously discriminate diabetic (τ 1 0.63  ±  0.05 ns, τ 2 3.66  ±  0.10 ns) samples from the control (τ 1 0.76  ±  0.03 ns, τ 2 4.48  ±  0.15 ns) group. We also report changes in the ratio of relative amplitudes of the two lifetime component in aorta tissue during diabetes, most likely related to the pseudohypoxic state with altered NADH homeostasis.

  16. Steady state and time-resolved autofluorescence studies of human colonic tissues

    Institute of Scientific and Technical Information of China (English)

    Buhong Li; Zhenxi Zhang; Shusen Xie

    2006-01-01

    Steady state and time-resolved autofluorescence spectroscopies are employed to study the autofluorescence characteristics of human colonic tissues in vitro. The excitation wavelength varies from 260 to 540 nm, and the corresponding fluorescence emission spectra are acquired from 280 to 800 nm. Significant difference in fluorescence intensity of excitation-emission matrices (EEMs) is observed between normal and tumor colonic tissues. Compared with normal colonic tissue, low nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD), and high amino acids and protoporphyrin Ⅸ (PpⅨ) fluorescences characterize high-grade malignant tissue. Moreover, the autofluorescence lifetimes of normal and carcinomatous colonic tissues at 635 nm under 397-nm excitation are about 4.32±0.12 and 18.45±0.05 ns, respectively. The high accumulation of endogenous PpⅨ in colonic cancers is demonstrated in both steady state and time-resolved autofluorescence spectroscopies.

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

    OpenAIRE

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

    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...

  18. Time-resolved far-infrared experiments at the National Synchrotron Light Source. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Tanner, D.B.; Reitze, D.H.; Carr, G.L.

    1999-10-12

    A facility for time-resolved infrared and far-infrared spectroscopy has been built and commissioned at the National Synchrotron Light Source. This facility permits the study of time dependent phenomena over a frequency range from 2-8000cm{sup {minus}1} (0.25 meV-1 eV). Temporal resolution is approximately 200 psec and time dependent phenomena in the time range out to 100 nsec can be investigated.

  19. Femtosecond time-resolved molecular multiphoton ionization: the Na_2 system

    OpenAIRE

    Baumert, Thomas,; Grosser, M.; Thalweiser, Rainer; Gerber, Gustav

    1991-01-01

    We report here the first experimental study of femtosecond time-resolved molecular multiphoton ionization. Femtosecond pump-probe techniques are combined with time-of-flight spectroscopy to measure transient ionization spectra of Na_2 in a molecular-beam experiment. The wave-packet motions in different molecular potentials show that incoherent contributions from direct photoionization of a singly excited state and from excitation and autoionization of a bound doubly excited molecu...

  20. Using Pyridinium Styryl Dyes as the Standards of Time-Resolved Instrument Response.

    Science.gov (United States)

    Li, Lei; Chang, Mengfang; Yi, Hua; Jia, Menghui; Cao, Xiaodan; Zhou, Zhongneng; Zhang, Sanjun; Pan, Haifeng; Shih, Chun-Wei; Jimenez, Ralph; Xu, Jianhua

    2016-07-01

    In this paper, two pyridinium styryl dyes, [2-(4-dimethylamino-phenyl)-vinyl]-1-methylpyridinium iodide (DASPMI), were synthesized and characterized by steady state fluorescence spectroscopy as well as picosecond and femtosecond time-resolved fluorescence spectroscopies. Both dyes exhibit large Stokes shifts and fluorescence decays equivalent to the instrument response function (IRF) standards employed in time-correlated single-photon counting. Due to their styryl and pyridinium moieties, DASPMIs have higher peak fluorescence intensity and shorter excited-state lifetimes than iodide ion-quenched fluorophores. The fluorescence lifetimes of o-DASPMI and p-DASPMI were measured to be 6.6 ps and 12.4 ps, respectively. The fluorescence transients of these DASPMIs were used as the IRFs for iterative reconvolution fitting of the time-resolved fluorescence decay profiles of Rhodamine B (RhB), sulforhodamine B (SRB), and the SRB-SRB2m RNA aptamer complex. The quality of the fits employing the DASPMI-derived IRFs are consistently equivalent to those employing IRFs obtained from light scattering. These results indicate that DASPMI-derived IRFs may be suited for a broad range of applications in time-resolved spectroscopy and fluorescence lifetime imaging microscopy (FLIM), especially in the visible emission range. PMID:27231333

  1. EPICS oscilloscope for time-resolved data acquisition

    International Nuclear Information System (INIS)

    The Sector 7 undulator beamline (7 ID) of the Advanced Photon Source (APS) is dedicated to time-resolved X-ray research . Silicon avalanche photodiodes (APDs) are used as the primary point detector for time-resolved Bragg diffraction experiments for their fast recovery time (5 photons/s) at the detector, however, deadtime corrections to the counting statistics become appreciable . Common practice has been to attenuate the monochromatic beam entering the experimental hutch to an appropriately low flux . For these high-flux experiments, an APD operated in proportional mode is a better detector choice due to a large dynamic range and linearity. With the ZT4212 ZTEC, EPICS based oscilloscope, the operating procedure to use an APD in proportional mode has been improved. This article shows the setup and operating procedure for this oscilloscope and demonstrates its application to measuring time-resolved rocking curves of laser excited semiconductors.

  2. Advances in Time-Resolved Tomographic Particle Image Velocimetry

    NARCIS (Netherlands)

    Lynch, K.P.

    2015-01-01

    This thesis details advanced developments in 3-D particle image velocimetry (PIV) based on the tomographic PIV technique, with an emphasis on time-resolved experiments. Tomographic PIV is a technique introduced in 2006 to measure the flow velocity in a three-dimensional volume. When measurements are

  3. An x-ray detector for time-resolved studies

    International Nuclear Information System (INIS)

    The development of ultrahigh-brightness x-ray sources makes time-resolved x-ray studies more and more feasible. Improvements in x-ray optics components are also critical for obtaining the appropriate beam for a particular type of experiment. Moreover, fast parallel detectors will be essential in order to exploit the combination of high intensity x-ray sources and novel optics for time-resolved experiments. A CCD detector with a time resolution of microseconds has been developed at the Advanced Photon Source (APS). This detector is fully programmable using CAMAC electronics and a Micro Vax computer. The techniques of time-resolved x-ray studies, which include scattering, microradiography, microtomography, stroboscopy, etc., can be applied to a range of phenomena (including rapid thermal annealing, surface ordering, crystallization, and the kinetics of phase transition) in order to understand these time-dependent microscopic processes. Some of these applications will be illustrated by recent results performed at synchrotrons. New powerful x-ray sources now under construction offer the opportunity to apply innovative approaches in time-resolved work

  4. Optimizing a time-resolved X-ray absorption experiment

    CERN Document Server

    Bressler, C; Chergui, M; Abela, R; Pattison, P

    2001-01-01

    Calculations are presented of the optimum conditions for performing a laser-pump X-ray probe time-resolved X-ray absorption experiment. The results concerning sensitivity and feasibility for implementing the method are illustrated for the case of the nascent I radical environment following I sup - photolysis in H sub 2 O.

  5. 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.

  6. Isotope identification capabilities using time resolved prompt gamma emission from epithermal neutrons

    International Nuclear Information System (INIS)

    We present a concept of integrated measurements for isotope identification which takes advantage of the time structure of spallation neutron sources for time resolved γ spectroscopy. Time resolved Prompt Gamma Activation Analysis (T-PGAA) consists in the measurement of gamma energy spectrum induced by the radioactive capture as a function of incident neutron Time Of Flight (TOF), directly related with the energy of incident neutrons. The potential of the proposed concept was explored on INES (Italian Neutron Experimental Station) at the ISIS spallation neutron source (U.K.). Through this new technique we show an increase in the sensitivity to specific elements of archaeometric relevance, through incident neutron energy selection in prompt γ spectra for multicomponent samples. Results on a standard bronze sample are presented

  7. Band edge identification and carrier dynamics of CVD MoS2 monolayer measured by broadband Femtosecond Transient Absorption Spectroscopy

    Science.gov (United States)

    Aleithan, Shrouq; Livshits, Maksim; Rack, Jeffrey; Kordesch, Martin; Stinaff, Eric

    Two-dimensional atomic crystals of transition metal dichalcogenides are considered promising candidates for optoelectronics, valleytronics, and energy harvesting devices. These materials exhibit excitonic features with high binding energy as a result of confinement effect and reduced screening when the material is thinned to monolayer. However, previous theoretical and experimental studies report different binding energy results. This work further examines the electronic structure and binding energy in this material using broadband Femtosecond Transient Absorption Spectroscopy. Samples of MoS2 were grown by chemical vapor deposition, pumped with femtosecond laser, and probed by femtosecond white light resulting in broadband differential absorption spectra with three distinct features related to the three dominant absorption peaks in the material: A, B, and C. The dependence of the transient absorption spectra on excitation wavelength and layer number provides evidence of a band gap located at C (2.9 eV) and therefore an excitonic binding energy of 1 eV. Additional features in the spectra identified as a broadening of the absorption features caused by carrier scattering, surface defects and trap states.

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

    International Nuclear Information System (INIS)

    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 β-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

  9. Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields

    Science.gov (United States)

    Paffi, Alessandra; Camera, Francesca; Lucano, Elena; Apollonio, Francesca; Liberti, Micaela

    2016-06-01

    An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform’s size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257–65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke’s brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz.

  10. Time resolved optical tomography of the human forearm

    Science.gov (United States)

    Hillman, Elizabeth M. C.; Hebden, Jeremy C.; Schweiger, Martin; Dehghani, Hamid; Schmidt, Florian E. W.; Delpy, David T.; Arridge, Simon R.

    2001-04-01

    A 32-channel time-resolved optical imaging instrument has been developed principally to study functional parameters of the new-born infant brain. As a prelude to studies on infants, the device and image reconstruction methodology have been evaluated on the adult human forearm. Cross-sectional images were generated using time-resolved measurements of transmitted light at two wavelengths. All data were acquired using a fully automated computer-controlled protocol. Images representing the internal scattering and absorbing properties of the arm are presented, as well as images that reveal physiological changes during a simple finger flexion exercise. The results presented in this paper represent the first simultaneous tomographic reconstruction of the internal scattering and absorbing properties of a clinical subject using purely temporal data, with additional co-registered difference images showing repeatable absorption changes at two wavelengths in response to exercise.

  11. Time-resolved CT angiography in aortic dissection

    Energy Technology Data Exchange (ETDEWEB)

    Meinel, Felix G., E-mail: felix.meinel@med.uni-muenchen.de [Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); Nikolaou, Konstantin, E-mail: konstantin.nikolaou@med.uni-muenchen.de [Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); Weidenhagen, Rolf, E-mail: rolf.weidenhagen@med.uni-muenchen.de [Department of Surgery, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); Hellbach, Katharina, E-mail: katharina.hellbach@med.uni-muenchen.de [Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); Helck, Andreas, E-mail: andreas.helck@med.uni-muenchen.de [Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); Bamberg, Fabian, E-mail: fabian.bamberg@med.uni-muenchen.de [Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); Reiser, Maximilian F., E-mail: maximilian.reiser@med.uni-muenchen.de [Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany); Sommer, Wieland H., E-mail: wieland.sommer@med.uni-muenchen.de [Department of Clinical Radiology, Ludwig Maximilians-University, Marchioninistr. 15, 81377 Munich (Germany)

    2012-11-15

    Objectives: We performed this study to assess feasibility and additional diagnostic value of time-resolved CT angiography of the entire aorta in patients with aortic dissection. Materials and methods: 14 consecutive patients with known or suspected aortic dissection (aged 60 {+-} 9 years) referred for aortic CT angiography were scanned on a dual-source CT scanner (Somatom Definition Flash; Siemens, Forchheim, Germany) using a shuttle mode for multiphasic image acquisition (range 48 cm, time resolution 6 s, 6 phases, 100 kV, 110 mAs/rot). Effective radiation doses were calculated from recorded dose length products. For all phases, CT densities were measured in the aortic lumen and renal parenchyma. From the multiphasic data, 3 phases corresponding to a triphasic standard CT protocol, served as a reference and were compared against findings from the time-resolved datasets. Results: Mean effective radiation dose was 27.7 {+-} 3.5 mSv. CT density of the true lumen peaked at 355 {+-} 53 HU. Compared to the simulated triphasic protocol, time-resolved CT angiography added diagnostic information regarding a number of important findings: the enhancement delay between true and false lumen (n = 14); the degree of membrane oscillation (n = 14); the perfusion delay in arteries originating from the false lumen (n = 9). Other additional information included true lumen collapse (n = 4), quantitative assessment of renal perfusion asymmetry (n = 2), and dynamic occlusion of aortic branches (n = 2). In 3/14 patients (21%), these additional findings of the multiphasic protocol altered patient management. Conclusions: Multiphasic, time-resolved CT angiography covering the entire aorta is feasible at a reasonable effective radiation dose and adds significant diagnostic information with therapeutic consequences in patients with aortic dissection.

  12. 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 ...... from the quartz D-e. It is possible that the long lifetime component from feldspars do not show anomalous fading. (c) 2006 Elsevier Ltd. All rights reserved....

  13. 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....

  14. Time-resolved imaging of latent fingerprints with nanosecond resolution

    Science.gov (United States)

    Seah, L. K.; Dinish, U. S.; Ong, S. K.; Chao, Z. X.; Murukeshan, V. M.

    2004-07-01

    Imaging of latent fingerprints using time-resolved (TR) method offers a broader platform to eliminate the unwanted background emission. In this paper, a novel TR imaging technique is demonstrated and implemented, which facilitates the detection of latent fingerprints with nanosecond resolution. Simulated experiments were carried out with two overlapping fingerprints treated with two fluorescent powders having different lifetimes in nanosecond range. The dependence of the fluorescence emission intensity in nanosecond resolution of TR imaging is also revealed.

  15. Stationary and time-resolved fluorescence for humic substances characterization

    OpenAIRE

    Kumke, Michael U.; Frimmel, Fritz Hartmann

    2007-01-01

    Steady-state and time-resolved fluorescence methods were applied to investigate the fluorescence properties of humic substances of different origins. Using standard 2D emission and total luminescence spectra, fluorescence maxima, the width of the fluorescence band and a relative fluorescence quantum efficiency were determined. Different trends for fulvic acids and humic acids were observed indicating differences in the heterogeneity of the sample fractions. The complexity of the fluorescence ...

  16. Time-resolved diffraction experiments on piezoelectric actuators

    OpenAIRE

    Rödl, Florian

    2010-01-01

    One of the most important features of many common functional ceramics is piezoelectricity, a phenomenon which is not fully under-stood so far. Especially the time-dependent response and its role in the deterioration of properties due to fatigue has not been much investigated. The present work focuses especially on time-resolved X-ray-diffraction, but also uses static methods to improve the understanding of dynamic processes that occur during switching in piezoelectric actuators and how they c...

  17. Time-resolved luminescence of Cr3+ in topaz Al2SiO4(OH,F)2

    International Nuclear Information System (INIS)

    Laser-induced time-resolved luminescence, decay times and optical spectroscopy of natural topaz Al2SiO4(OH,F)2 show the presence of several luminescence centers: single Cr3+ in intermediate crystal field position, Cr-Cr pairs and radiation induced center. The possible connection of the last center with Mn4+ and V2+ is discussed

  18. Time-resolved MR angiography with limited projections.

    Science.gov (United States)

    Huang, Yuexi; Wright, Graham A

    2007-08-01

    A method for reconstruction of time-resolved MRI called highly-constrained backprojection (HYPR) has been developed. To evaluate the HYPR reconstruction in relation to data sparsity and temporal dynamics, computer simulations were performed, investigating signal modulations under different situations that reflect dynamic contrast-enhanced MR angiography (MRA). In vivo studies were also performed with gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) for abdominal MRA in a canine model to demonstrate the application of HYPR for three-dimensional (3D) time-resolved MRA. When contrast dynamics vary over space, large vessels (e.g., veins) tend to introduce signal interference to small vessels (e.g., arteries) in HYPR, particularly when the vessels are in close proximity. The enhancement of background tissue signals may also alter the arterial and venous temporal profiles in HYPR. However, the artifacts are manifest as intensity modulation rather than structural interference, and therefore have little impact on structural diagnosis. Increasing the number of projections per time point increases temporal blur while reducing corruption of temporal behavior from adjacent tissues. Uniformly interleaved acquisition order, such as the bit-reversed order, is important to reduce artifacts. With high signal-to-noise ratio (SNR) and limited artifacts, HYPR reconstruction has potential to greatly improve time-resolved MRA in clinical practice.

  19. Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography.

    Science.gov (United States)

    Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; Gati, Cornelius; Kimura, Tetsunari; Milne, Christopher; Milathianaki, Despina; Kubo, Minoru; Wu, Wenting; Conrad, Chelsie; Coe, Jesse; Bean, Richard; Zhao, Yun; Båth, Petra; Dods, Robert; Harimoorthy, Rajiv; Beyerlein, Kenneth R; Rheinberger, Jan; James, Daniel; DePonte, Daniel; Li, Chufeng; Sala, Leonardo; Williams, Garth J; Hunter, Mark S; Koglin, Jason E; Berntsen, Peter; Nango, Eriko; Iwata, So; Chapman, Henry N; Fromme, Petra; Frank, Matthias; Abela, Rafael; Boutet, Sébastien; Barty, Anton; White, Thomas A; Weierstall, Uwe; Spence, John; Neutze, Richard; Schertler, Gebhard; Standfuss, Jörg

    2016-08-22

    Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within the crystal lattice is confirmed by time-resolved visible absorption spectroscopy. This study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX.

  20. Broadband optical absorbance spectroscopy using a whispering gallery mode microsphere resonator

    Science.gov (United States)

    Westcott, Sarah L.; Zhang, Jiangquan; Shelton, Robert K.; Bruce, Nellie M. K.; Gupta, Sachin; Keen, Steven L.; Tillman, Jeremy W.; Wald, Lara B.; Strecker, Brian N.; Rosenberger, A. T.; Davidson, Roy R.; Chen, Wei; Donovan, Kevin G.; Hryniewicz, John V.

    2008-03-01

    We demonstrate the ability to excite and monitor many whispering gallery modes (WGMs) of a microsphere resonator simultaneously in order to make broadband optical absorbance measurements. The 340μm diameter microsphere is placed in a microfluidic channel. A hemispherical prism is used for coupling the WGMs into and out of the microsphere. The flat surface of the prism seals the microfluidic channel. The slight nonsphericity in the microsphere results in coupling to precessed modes whose emission is spatially separated from the reflected excitation light. The evanescent fields of the light trapped in WGMs interact with the surrounding environment. The change in transmission observed in the precessed modes is used to determine the absorbance of the surrounding environment. In contrast to our broadband optical absorbance measurements, previous WGM sensors have used only a single narrow mode to measure properties such as refractive index. With the microfluidic cell, we have measured the absorbance of solutions of dyes (lissamine green B, sunset yellow, orange G, and methylene blue), aromatic molecules (benzylamine and benzoic acid), and biological molecules (tryptophan, phenylalanine, tyrosine, and o-phospho-L-tyrosine) at visible and ultraviolet wavelengths. The microsphere surface was reacted with organosilane molecules to attach octadecyl groups, amino groups, and fluorogroups to the surface. Both electrostatic and hydrophobic interactions were observed between the analytes and the microsphere surface, as indicated by changes in the measured effective pathlength with different organosilanes. For a given analyte and coated microsphere, the pathlength measurement was repeatable within a few percent. Methylene blue dye had a very strong interaction with the surface and pathlengths of several centimeters were measured. Choosing an appropriate surface coating to interact with a specific analyte should result in the highest sensitivity detection.

  1. Time-resolved mass spectroscopic studies of an atmospheric-pressure helium microplasma jet

    OpenAIRE

    Oh, Jun-Seok; Aranda-Gonzalvo, Yolanda; James W. Bradley

    2011-01-01

    Abstract Using molecular beam mass spectroscopy, time-resolved measurements of the ionic species 12 in the plasma plume of an atmospheric-pressure helium microplasma jet have been made for 13 a range of excitation frequencies (5, 10 and 25 kHz) and source-instruments orifice distances 14 (1, 7 and 11 mm). Ionic species can only be observed in the visible plasma plume, with the 15 main positive species being N 2 + (65.26%) and O 2 + (21.11%), and few percentages of N +, O +, 16 NO + and He ...

  2. Spectroscopic Analysis of Time-Resolved Emission from Shocked Explosive Samples

    Science.gov (United States)

    Kay, Jeffrey; Jilek, Brook; Wixom, Ryan; Knepper, Robert; Tappan, Alexander; Damm, David

    2015-06-01

    We report a series of time-resolved spectroscopic measurements that aim to characterize the reactions that occur during shock initiation of high explosives. The experiments employ time- and wavelength-resolved emission spectroscopy to analyze light emitted from shocked and detonating thin explosive films. In this talk we present analysis of optical emission spectra from hexanitroazobenzene (HNAB), hexanitrostilbene (HNS), and pentaerythritol tetranitrate (PETN) samples. The emission features observed in the spectra are assigned to electronic transitions of molecular fragments, and the implications of these findings on our understanding of the underlying reaction mechanisms are discussed.

  3. Singlet Exciton Migration in a Conjugated Polymer by Picosecond Time-Resolved Photoluminescence

    Institute of Scientific and Technical Information of China (English)

    马国宏; 钱士雄; 雷洪; 汪河洲; 王荣秋; 李永舫

    2001-01-01

    The transient photoluminescence (PL) of DO-PPV (poly-(2,5-dioctyloxy-1,4-phenylene vinylene)) solution in chloroform was investigated by picosecond time-resolved PL spectroscopy. An ultrafast rise of PL and the following single exponential decay with a time constant of about 400ps were assigned to the formation of the intrachain exciton and its decay process, respectively. The redshift of the PL emission spectrum with time was caused by the subsequent exciton migration among the different conjugated segments in the DO-PPV polymer.

  4. Time-resolved luminescence studies of Eu3+ in soda-lime silicate glasses

    Science.gov (United States)

    Ruivo, Andreia; Muralha, Vânia S. F.; Águas, Hugo; de Matos, António Pires; Laia, César A. T.

    2014-02-01

    Soda-lime glasses doped with Eu3+ were synthesized using a variety of compositions, namely changing the fraction of CaO or Eu2O3. Those glasses were characterized with several techniques, including ellipsometry, UV-vis-NIR absorption spectroscopy, steady-state photoluminescence spectroscopy and time-resolved luminescence. The compositions' effects on optical properties such as refraction indexes, Eu3+ oscillator strengths and luminescence lifetimes were accessed from the analysis of the experimental results. Judd-Ofelt theory was used to analyze all these aspects, which allow the detection of a mismatch of optical properties from absorption and emission spectroscopy. This mismatch was confirmed from the time-resolved data, showing the existence of two different spectroscopic Eu3+ species. From those results it is concluded that there is evidence for lanthanide aggregation, giving rise to self-quenching effects that may be described through resonance energy transfer mechanisms. The difference between luminescence lifetimes for isolated and aggregated Eu(III) is interpreted as due to different interactions with oxygen in the matrix, namely degree of covalency of the Eu-O bond and point group symmetry of the lanthanide.

  5. 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.

  6. Lucas-Kanade fluid trajectories for time-resolved PIV

    Science.gov (United States)

    Yegavian, Robin; Leclaire, Benjamin; Champagnat, Frédéric; Illoul, Cédric; Losfeld, Gilles

    2016-08-01

    We introduce a new method for estimating fluid trajectories in time-resolved PIV. It relies on a Lucas-Kanade paradigm and consists in a simple and direct extension of a two-frame estimation with FOLKI-PIV (Champagnat et al 2011 Exp. Fluids 50 1169-82). The so-called Lucas-Kanade Fluid Trajectories (LKFT) are assumed to be polynomial in time, and are found as the minimizer of a global functional, in which displacements are sought so as to match the intensities of a series of images pairs in the sequence, in the least-squares sense. All pairs involve the central image, similar to other recent time-resolved approaches (FTC (Lynch and Scarano 2013 Meas. Sci. Technol. 24 035305) and FTEE (Jeon et al 2014 Exp. Fluids 55 1-16)). As switching from a two-frame to a time-resolved objective simply amounts to adding terms in a functional, no significant additional algorithmic element is required. Similar to FOLKI-PIV the method is very well suited for GPU acceleration, which is an important feature as computational complexity increases with the image sequence size. Tests on synthetic data exhibiting peak-locking show that increasing the image sequence size strongly reduces both associated bias and random error, and that LKFT has a remaining total error comparable to that of FTEE on this case. Results on case B of the third PIV challenge (Stanislas et al 2008 Exp. Fluids 45 27-71) also show its ability to drastically reduce the error in situations with low signal-to-noise ratio. These results are finally confirmed on experimental images acquired in the near-field of a low Reynolds number jet. Strong reductions in peak-locking, spatial and temporal noise compared to two-frame estimation are also observed, on the displacement components themselves, as well as on spatial or temporal derivatives, such as vorticity and material acceleration.

  7. Femtosecond time-resolved MeV electron microscopy

    International Nuclear Information System (INIS)

    The direct visualization of fundamental dynamic processes in matter occurring on femtosecond time scales over sub-nanometer (even atomic) spatial dimensions has long been a goal in science. In this paper, the development of a femtosecond time-resolved relativistic transmission electron microscopy (FsTEM) based on a photocathode radio-frequency (RF) gun is reported. The requirements and limitations of the beam parameters used in FsTEM are discussed. Finally, some demonstrations of relativistic ultrafast electron diffraction measurement using the RF gun are presented. (author)

  8. A compact electron gun for time-resolved electron diffraction

    International Nuclear Information System (INIS)

    A novel compact time-resolved electron diffractometer has been built with the primary goal of studying the ultrafast molecular dynamics of photoexcited gas-phase molecules. Here, we discuss the design of the electron gun, which is triggered by a Ti:Sapphire laser, before detailing a series of calibration experiments relating to the electron-beam properties. As a further test of the apparatus, initial diffraction patterns have been collected for thin, polycrystalline platinum samples, which have been shown to match theoretical patterns. The data collected demonstrate the focusing effects of the magnetic lens on the electron beam, and how this relates to the spatial resolution of the diffraction pattern

  9. TIME-RESOLVED PHOTOLUMINESCENCE OF SINTERED ZnO CERAMICS

    Institute of Scientific and Technical Information of China (English)

    WEN XIAO-MING(文小明); N.OHNO; ZHANG ZHONG-MING(张中明)

    2001-01-01

    The time-resolved photoluminescence (TRPL) of sintered ZnO ceramics was measured at low temperatures. A broad luminescence band was observed in the visible region. The TRPL experiment shows that photolurninescence decay behaviour can be depicted as t-π(r). The decay rate n(r) and lifetime are wavelength dependent, and the former varies exponentially with wavelength. The power-lowering behaviour of the luminescence intensity indicates that the luminescence band originates from the recombination of donor-acceptor pairs.

  10. Natural killer cell cytotoxicity assay with time-resolved fluorimetry

    Institute of Scientific and Technical Information of China (English)

    李建中; 章竹君; 金伯泉; 田方

    1996-01-01

    A new time-resolved fluorimetric method for the measurement of natural killer (NK) cell cytotoxicity has been developed by labelling the target cell K562 with a new synthesized fluorescence marker KLUK. The method has advantages of higher sensitivity, time-saving, good reproducibility and has no radioactivity problems. A satisfactory result is obtained by comparing it with 51Cr release method. It demonstrates that the new marker provides an alternative to currently used radioactive markers for the assessment of in vitro cellular cytotoxicity.

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

    OpenAIRE

    Yuxiang Yang; Wen Zhang; Fangling Du; Xuan Tang; He Wen; Zhaosheng Teng

    2014-01-01

    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, th...

  12. 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...

  13. 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.

  14. Time-resolved HAXPES at SACLA: probe and pump pulse-induced space-charge effects

    International Nuclear Information System (INIS)

    Time-resolved hard x-ray photoelectron spectroscopy (trHAXPES) is established using the x-ray free-electron laser SACLA. The technique extends time-resolved photoemission into the hard x-ray regime and, as a core-level spectroscopy, combines element and atomic-site specificity and sensitivity to the chemical environment with femtosecond time resolution and bulk (sub-surface) sensitivity. The viability of trHAXPES using 8 keV x-ray free-electron-laser radiation is demonstrated by a systematic investigation of probe and pump pulse-induced vacuum space-charge effects on the V 1s emission of VO2 and the Ti 1s emission of SrTiO3. The time and excitation energy dependencies of the measured spectral shifts and broadenings are compared to the results of N-body numerical simulations and simple analytic (mean-field) models. Good agreement between the experimental and calculated results is obtained. In particular, the characteristic temporal evolution of the pump pulse-induced spectral shift is shown to provide an effective means to determine the temporal overlap of pump and probe pulses. trHAXPES opens a new avenue in the study of ultrafast atomic-site specific electron and chemical dynamics in materials and at buried interfaces. (paper)

  15. Time-to-digital converter card for multichannel time-resolved single-photon counting applications

    Science.gov (United States)

    Tamborini, Davide; Portaluppi, Davide; Tisa, Simone; Tosi, Alberto

    2015-03-01

    We present a high performance Time-to-Digital Converter (TDC) card that provides 10 ps timing resolution and 20 ps (rms) timing precision with a programmable full-scale-range from 160 ns to 10 μs. Differential Non-Linearity (DNL) is better than 1.3% LSB (rms) and Integral Non-Linearity (INL) is 5 ps rms. Thanks to the low power consumption (400 mW) and the compact size (78 mm x 28 mm x 10 mm), this card is the building block for developing compact multichannel time-resolved instrumentation for Time-Correlated Single-Photon Counting (TCSPC). The TDC-card outputs the time measurement results together with the rates of START and STOP signals and the number of valid TDC conversions. These additional information are needed by many TCSPC-based applications, such as: Fluorescence Lifetime Imaging (FLIM), Time-of-Flight (TOF) ranging measurements, time-resolved Positron Emission Tomography (PET), single-molecule spectroscopy, Fluorescence Correlation Spectroscopy (FCS), Diffuse Optical Tomography (DOT), Optical Time-Domain Reflectometry (OTDR), quantum optics, etc.

  16. Toward picosecond time-resolved X-ray absorption studies of interfacial photochemistry

    Science.gov (United States)

    Gessner, Oliver; Mahl, Johannes; Neppl, Stefan

    2016-05-01

    We report on the progress toward developing a novel picosecond time-resolved transient X-ray absorption spectroscopy (TRXAS) capability for time-domain studies of interfacial photochemistry. The technique is based on the combination of a high repetition rate picosecond laser system with a time-resolved X-ray fluorescent yield setup that may be used for the study of radiation sensitive materials and X-ray spectroscopy compatible photoelectrochemical (PEC) cells. The mobile system is currently deployed at the Advanced Light Source (ALS) and may be used in all operating modes (two-bunch and multi-bunch) of the synchrotron. The use of a time-stamping technique enables the simultaneous recording of TRXAS spectra with delays between the exciting laser pulses and the probing X-ray pulses spanning picosecond to nanosecond temporal scales. First results are discussed that demonstrate the viability of the method to study photoinduced dynamics in transition metal-oxide semiconductor (SC) samples under high vacuum conditions and at SC-liquid electrolyte interfaces during photoelectrochemical water splitting. Opportunities and challenges are outlined to capture crucial short-lived intermediates of photochemical processes with the technique. This work was supported by the Department of Energy Office of Science Early Career Research Program.

  17. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    Energy Technology Data Exchange (ETDEWEB)

    Grills, David C., E-mail: dcgrills@bnl.gov; Farrington, Jaime A.; Layne, Bobby H.; Preses, Jack M.; Wishart, James F. [Chemistry Department, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973-5000 (United States); Bernstein, Herbert J. [Department of Mathematics and Computer Science, Dowling College, 1300 William Floyd Parkway, Shirley, New York 11967 (United States)

    2015-04-15

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330 to 1051 cm{sup −1}. The response time of the TRIR detection setup is ∼40 ns, with a typical sensitivity of ∼100 μOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. This new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.

  18. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility.

    Science.gov (United States)

    Grills, David C; Farrington, Jaime A; Layne, Bobby H; Preses, Jack M; Bernstein, Herbert J; Wishart, James F

    2015-04-01

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330 to 1051 cm(-1). The response time of the TRIR detection setup is ∼40 ns, with a typical sensitivity of ∼100 μOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. This new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.

  19. A Study of Electron and Phonon Dynamics by Broadband Two-Dimensional THz Time-Domain Spectroscopy

    Science.gov (United States)

    Fu, Zhengping

    Terahertz (THz) wave interacts with semiconductors in many ways, such as resonant excitation of lattice vibration, intraband transition and polaron formation. Different from the optical waves, THz wave has lower photon energy (1 THz = 4.14 meV) and is suitable for studying dynamics of low-energy excitations. Recently the studies of the interaction of THz wave and semiconductors have been extending from the linear regime to the nonlinear regime, owing to the advance of the high-intensity THz generation and detection methods. Two-dimensional (2D) spectroscopy, as a useful tool to unravel the nonlinearity of materials, has been well developed in nuclear magnetic resonance and infrared region. However, the counterpart in THz region has not been well developed and was only demonstrated at frequency around 20 THz due to the lack of intense broadband THz sources. Using laser-induced plasma as the THz source, we developed collinear broadband 2D THz time-domain spectroscopy covering from 0.5 THz to 20 THz. Broadband intense THz pulses emitted from laser-induced plasma provide access to a variety of nonlinear properties of materials. Ultrafast optical and THz pulses make it possible to resolve the transient change of the material properties with temporal resolution of tens of femtoseconds. This thesis focuses on the linear and nonlinear interaction of the THz wave with semiconductors. Since a great many physical processes, including vibrational motion of lattice and plasma oscillation, has resonant frequency in the THz range, rich physics can be studies in our experiment. The thesis starts from the linear interaction of the THz wave with semiconductors. In the narrow band gap semiconductor InSb, the plasma absorption edge, Restrahlen band and dispersion of polaritons are observed. The nonlinear response of InSb in high THz field is verified in the frequency-resolved THz Z-scan experiment. The third harmonic generations due to the anharmonicity of plasma oscillation and the

  20. Vacuum UV broad-band absorption spectroscopy: a powerful diagnostic tool for reactive plasma monitoring

    OpenAIRE

    Cunge, G; Fouchier, M; Brihoum, M; Bodart, P.; Touzeau, M.; N. Sadeghi

    2011-01-01

    Abstract Broad band UV-visible absorption spectroscopy is widely used to measure the concentration of radicals in reactive plasmas. We extended the applicability of this technique to the VUV (115 nm to 200 nm), the spectral range in which the electronic transitions from the ground state to the Rydberg or pre-dissociated states of many closed shell molecules are located. This gives access to the absolute densities of species which do not, or weakly absorb in the UV/visible range. The techni...

  1. Broadband multi-interferometer spectroscopy in high magnetic fields: From THz to visible

    Science.gov (United States)

    Padilla, W. J.; Li, Z. Q.; Burch, K. S.; Lee, Y. S.; Mikolaitis, K. J.; Basov, D. N.

    2004-11-01

    We present a system capable of broad band frequency domain spectroscopy in the range 6-20 000 cm-1 at cryogenic temperatures. The apparatus couples two different interferometers to a 9 Tesla superconducting split coil magnet and is designed to work with various detectors, including thermal bolometers and semiconducting detectors. The optical layout utilizes an intermediate focus while preserving optical f/#'s throughout enabling DC magnetic field measurements of small crystals with polarized light in both Voight and Faraday geometries. A reference channel eliminates errors associated with system drift and facilitates determination of the optical constants. For transparent samples, simultaneous reflection and transmission can be performed.

  2. Director tumbling of nematic wormlike micelles under shear: time-resolved rheo-NMR experiments

    International Nuclear Information System (INIS)

    Nematic liquid crystals show a complex flow behavior due to the coupling between orientation and flow. Some materials show a stable director orientation in steady shear flow (flow aligning), while for others no stable director orientation exists (tumbling). Director tumbling gives rise to oscillations of shear and normal stresses in rheological experiments and can be detected by optical methods, for example by microscopy or birefringence measurements. We have used deuterium NMR spectroscopy to observe shear-induced director orientations. In the lyotropic system cetylpyridinium chloride/hexanol/brine, which forms a nematic phase of wormlike micelles, time-resolved observations of the director orientation by means of deuterium NMR spectroscopy of D2O have been possible for the first time. The time-dependence of the director orientations in both shear start-up and flow-reversal experiments will be presented. (orig.)

  3. Detailed optical and near-infrared polarimetry, spectroscopy and broadband photometry of the afterglow of GRB 091018: Polarisation evolution

    CERN Document Server

    Wiersema, K; Kruehler, T; Melandri, A; Rol, E; Starling, R L C; Tanvir, N R; van der Horst, A J; Covino, S; Fynbo, J P U; Goldoni, P; Gorosabel, J; Hjorth, J; Klose, S; Mundell, C G; O'Brien, P T; Palazzi, E; Wijers, R A M J; D'Elia, V; Evans, P A; Filgas, R; Gomboc, A; Greiner, J; Guidorzi, C; Kaper, L; Kobayashi, S; Kouveliotou, C; Levan, A J; Rossi, A; Rowlinson, A; Steele, I A; Postigo, A de Ugarte; Vergani, S D

    2012-01-01

    [Abridged] A number of phenomena have been observed in GRB afterglows that defy explanation by simple versions of the standard fireball model, leading to a variety of new models. Polarimetry can be a major independent diagnostic of afterglow physics, probing the magnetic field properties and internal structure of the GRB jets. In this paper we present the first high quality multi-night polarimetric light curve of a Swift GRB afterglow, aimed at providing a well calibrated dataset of a typical afterglow to serve as a benchmark system for modelling afterglow polarisation behaviour. In particular, our dataset of the afterglow of GRB 091018 (at redshift z=0.971) comprises optical linear polarimetry (R band, 0.13 - 2.3 days after burst); circular polarimetry (R band) and near-infrared linear polarimetry (Ks band). We add to that high quality optical and near-infrared broadband light curves and spectral energy distributions as well as afterglow spectroscopy. The linear polarisation varies between 0 and 3%, with bot...

  4. Vibrational Spectral Signatures of Crystalline Cellulose Using High Resolution Broadband Sum Frequency Generation Vibrational Spectroscopy (HR-BB-SFG-VS)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Libing; Lu, Zhou; Velarde Ruiz Esparza, Luis A.; Fu, Li; Pu, Yunqiao; Ding, Shi-You; Ragauskas, Art J.; Wang, Hongfei; Yang, Bin

    2015-03-03

    Here we reported the first sub-wavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) study on both the C-H and O-H region spectra of crystalline cellulose. HR-BB-SFG-VS has about 10 times better resolution than the conventional scanning SFG-VS and is known to be able to measure the intrinsic spectral lineshape and to resolve much more spectral details. With HR-BB-SFG-VS, we found that in cellulose from different sources, including Avicel and cellulose crystals isolated from algae Valonia (Iα) and tunicates (Iβ), the spectral signatures in the OH regions were unique for different allomorphs, i.e. Iα and Iβ, while the spectral signatures in the C-H regions varied in all samples examined. Even though the origin of the different behaviors of the crystalline cellulose in the O-H and C-H vibrational frequency regions is yet to be correlated to the structure of cellulose, these results provided new spectroscopic methods and opportunities to classify and understand the basic crystalline structure, as well as variations, in polymorphism of the crystalline cellulose structure.

  5. High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: Part 1, data analysis and results

    Science.gov (United States)

    Erskine, David J.; Edelstein, Jerry; Wishnow, Edward H.; Sirk, Martin; Muirhead, Philip S.; Muterspaugh, Matthew W.; Lloyd, James P.; Ishikawa, Yuzo; McDonald, Eliza A.; Shourt, William V.; Vanderburg, Andrew M.

    2016-04-01

    High-resolution broadband spectroscopy at near-infrared wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar. Observations of stars were performed with the "TEDI" interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec near-infrared echelle spectrograph. These are the first multidelay EDI demonstrations on starlight, as earlier measurements used a single delay or laboratory sources. We demonstrate very high (10×) resolution boost, from original 2700 to 27,000 with current set of delays (up to 3 cm), well beyond the classical limits enforced by the slit width and detector pixel Nyquist limit. Significantly, the EDI used with multiple delays rather than a single delay as used previously yields an order of magnitude or more improvement in the stability against native spectrograph point spread function (PSF) drifts along the dispersion direction. We observe a dramatic (20×) reduction in sensitivity to PSF shift using our standard processing. A recently realized method of further reducing the PSF shift sensitivity to zero is described theoretically and demonstrated in a simple simulation which produces a 350× times reduction. We demonstrate superb rejection of fixed pattern noise due to bad detector pixels-EDI only responds to changes in pixel intensity synchronous to applied dithering. This part 1 describes data analysis, results, and instrument noise. A section on theoretical photon limited sensitivity is in a companion paper, part 2.

  6. Broadband Ultrahigh-Resolution Spectroscopy of Particle-Induced X Rays: Extending the Limits of Nondestructive Analysis

    Science.gov (United States)

    Palosaari, M. R. J.; Käyhkö, M.; Kinnunen, K. M.; Laitinen, M.; Julin, J.; Malm, J.; Sajavaara, T.; Doriese, W. B.; Fowler, J.; Reintsema, C.; Swetz, D.; Schmidt, D.; Ullom, J. N.; Maasilta, I. J.

    2016-08-01

    Nondestructive analysis (NDA) based on x-ray emission is widely used, for example, in the semiconductor and concrete industries. Here, we demonstrate significant quantitative and qualitative improvements in broadband x-ray NDA by combining particle-induced emission with detection based on superconducting microcalorimeter arrays. We show that the technique offers great promise in the elemental analysis of thin-film and bulk samples, especially in the difficult cases where tens of different elements with nearly overlapping emission lines have to be identified down to trace concentrations. We demonstrate the efficiency and resolving capabilities by spectroscopy of several complex multielement samples in the energy range 1-10 keV, some of which have a trace amount of impurities not detectable with standard silicon drift detectors. The ability to distinguish the chemical environment of an element is also demonstrated by measuring the intensity differences and chemical shifts of the characteristics x-ray peaks of titanium compounds. In particular, we report measurements of the K α /K β intensity ratio of thin films of TiN and measurements of Ti K α satellite peak intensities in various Ti thin-film compounds. We also assess the detection limits of the technique, comment on detection limits possible in the future, and discuss possible applications.

  7. Towards time-resolved serial crystallography in a microfluidic device.

    Science.gov (United States)

    Pawate, Ashtamurthy S; Šrajer, Vukica; Schieferstein, Jeremy; Guha, Sudipto; Henning, Robert; Kosheleva, Irina; Schmidt, Marius; Ren, Zhong; Kenis, Paul J A; Perry, Sarah L

    2015-07-01

    Serial methods for crystallography have the potential to enable dynamic structural studies of protein targets that have been resistant to single-crystal strategies. The use of serial data-collection strategies can circumvent challenges associated with radiation damage and repeated reaction initiation. This work utilizes a microfluidic crystallization platform for the serial time-resolved Laue diffraction analysis of macroscopic crystals of photoactive yellow protein (PYP). Reaction initiation was achieved via pulsed laser illumination, and the resultant electron-density difference maps clearly depict the expected pR(1)/pR(E46Q) and pR(2)/pR(CW) states at 10 µs and the pB1 intermediate at 1 ms. The strategies presented here have tremendous potential for extension to chemical triggering methods for reaction initiation and for extension to dynamic, multivariable analyses.

  8. Femtosecond Time-resolved MeV Electron Diffraction

    CERN Document Server

    Zhu, Pengfei; Cao, J; Geck, J; Hidaka, Y; Kraus, R; Pjerov, S; Shen, Y; Tobey, R I; Zhu, Y; Hill, J P; Wang, X J

    2013-01-01

    We report the experimental demonstration of electron diffraction with 130 femtosecond time resolution using bench-top MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminium and single-crystal 1T-TaS_{2} are obtained utilizing a 5 femto-Coulomb (~3x10^{4} electrons) pulse of electrons at 2.8 MeV. The timing jitter between the pump laser and probe electron beam was found to be ~ 100 fs. The time resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS_{2} following an optical pump. Our experiemntal results demonstrate the feasibility of ultimately realizing 40 fs time-resolved electron diffraction.

  9. 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.

  10. 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.

  11. Fast time-resolved aerosol collector: proof of concept

    Directory of Open Access Journals (Sweden)

    X.-Y. Yu

    2010-10-01

    Full Text Available Atmospheric particles can be collected in the field on substrates for subsequent laboratory analysis via chemically sensitive single particle methods such as scanning electron microscopy with energy dispersive x-ray analysis. With moving substrates time resolution of seconds to minutes can be achieved. In this paper, we demonstrate how to increase the time resolution when collecting particles on a substrate to a few milliseconds to provide real-time information. Our fast time-resolved aerosol collector ("Fast-TRAC" microscopically observes the particle collection on a substrate and records an on-line video. Particle arrivals are resolved to within a single frame (4–17 ms in this setup, and the spatial locations are matched to the subsequent single particle analysis. This approach also provides in-situ information on particle size and number concentration. Applications are expected in airborne studies of cloud microstructure, pollution plumes, and surface long-term monitoring.

  12. Fast time-resolved aerosol collector: proof of concept

    Directory of Open Access Journals (Sweden)

    X.-Y. Yu

    2010-06-01

    Full Text Available Atmospheric particles can be collected in the field on substrates for subsequent laboratory analysis via chemically sensitive single particle methods such as scanning electron microscopy with energy dispersive x-ray analysis. With moving substrates time resolution of seconds to minutes can be achieved. In this paper, we demonstrate how to increase the time resolution when collecting particles on a substrate to a few milliseconds to provide real-time information. Our fast time-resolved aerosol collector ("Fast-TRAC" microscopically observes the particle collection on a substrate and records an on-line video. Particle arrivals are resolved to within a single frame (4–17 ms in this setup, and the spatial locations are matched to the subsequent single particle analysis. This approach also provides in-situ information on particle size and number concentration. Applications are expected in airborne studies of cloud microstructure, pollution plumes, and surface long-term monitoring.

  13. Pose estimation using time-resolved inversion of diffuse light.

    Science.gov (United States)

    Raviv, Dan; Barsi, Christopher; Naik, Nikhil; Feigin, Micha; Raskar, Ramesh

    2014-08-25

    We present a novel approach for evaluation of position and orientation of geometric shapes from scattered time-resolved data. Traditionally, imaging systems treat scattering as unwanted and are designed to mitigate the effects. Instead, we show here that scattering can be exploited by implementing a system based on a femtosecond laser and a streak camera. The result is accurate estimation of object pose, which is a fundamental tool in analysis of complex scenarios and plays an important role in our understanding of physical phenomena. Here, we experimentally show that for a given geometry, a single incident illumination point yields enough information for pose estimation and tracking after multiple scattering events. Our technique can be used for single-shot imaging behind walls or through turbid media.

  14. Time-resolved tomographic images of a relativistic electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, H.A.; Jacoby, B.A.; Nelson, M.

    1984-07-01

    We obtained a sequential series of time-resolved tomographic two-dimensional images of a 4.5-MeV, 6-kA, 30-ns electron beam. Three linear fiber-optic arrays of 30 or 60 fibers each were positioned around the beam axis at 0/sup 0/, 61/sup 0/, and 117/sup 0/. The beam interacting with nitrogen at 20 Torr emitted light that was focused onto the fiber arrays and transmitted to a streak camera where the data were recorded on film. The film was digitized, and two-dimensional images were reconstructed using the maximum-entropy tomographic technique. These images were then combined to produce an ultra-high-speed movie of the electron-beam pulse.

  15. Time-resolved neutron imaging at ANTARES cold neutron beamline

    CERN Document Server

    Tremsin, A S; Tittelmeier, K; Schillinger, B; Schulz, M; Lerche, M; Feller, W B

    2015-01-01

    In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time is conducted with static objects mainly due to the limited flux intensity of neutron beamline facilities and sometimes due to the limitations of the detectors. However, some applications require the studies of dynamic phenomena and can now be conducted at several high intensity beamlines such as the recently rebuilt ANTARES beam line at the FRM-II reactor. In this paper we demonstrate the capabilities of time resolved imaging for repetitive processes, where different phases of the process can be imaged simultaneously and...

  16. 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.

  17. Carrier dynamics of rubrene single-crystals revealed by transient broadband terahertz spectroscopy

    Science.gov (United States)

    Yada, H.; Uchida, R.; Sekine, H.; Terashige, T.; Tao, S.; Matsui, Y.; Kida, N.; Fratini, S.; Ciuchi, S.; Okada, Y.; Uemura, T.; Takeya, J.; Okamoto, H.

    2014-10-01

    Carrier dynamics of an organic molecular semiconductor, rubrene, was investigated by optical-pump terahertz-probe spectroscopy from 1 to 15 THz. At 294 K, a Drude-like response due to photogenerated hole carriers is observed below 8 THz. The real part σ 1 ( ω ) of the optical conductivity is suppressed below 2 THz, indicating the presence of a localization effect. Such a spectral feature was reproduced by a Drude-Anderson model including the effect of dynamical disorder due to intermolecular vibrations. At 50 K, the spectral weight of σ 1 ( ω ) due to photocarriers shifts to lower frequency below 4 THz and the suppression of σ 1 ( ω ) is hardly observed, which we associate with a reduction of thermal molecular motions. The overall photocarrier generation and recombination dynamics is also discussed.

  18. A superconfiguration model for broadband spectroscopy of non-LTE plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Peyrusse, O. [CEA-DIF, BP 12, 91680 Bruyeres-le-Chatel (France)

    2000-10-28

    We present an atomic physics package called AVERROES/TRANSPEC for studying plasma spectroscopy of complex L-, M-shell emitters or even core-excited multielectron K-shell emitters. The model, which is also intended to give some insights on ionization properties of M-shell ionized plasmas, is divided into two parts. The first part (AVERROES) is based on the superconfiguration concept and on the supertransition array method. It generates superconfiguration average-energies, collisional and radiative rates needed for a calculation of population kinetics. It also calculates the statistical shift and width associated with each possible radiative electron jump between selected superconfigurations. All the previously mentioned quantities are stored on files readable by a multicell time-dependent collisional-radiative model (TRANSPEC) that calculates population kinetics and synthetic emission spectra. This last code can be employed with a hydrodynamics code to provide simulated x-ray outputs of non-steady-state inhomogeneous plasmas. (author)

  19. 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.

  20. Eight-channel time-resolved tissue oximeter for functional muscle studies

    Science.gov (United States)

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

    2003-07-01

    A portable instrument for tissue oximetry based on time-resolved reflectance spectroscopy was developed. The output pulses of 2 laser diodes (683 and 785 nm, 80 MHz pulse repetition rate, 1 mW average power, 100 ps FWHM) are delayed and coupled into a multimode graded-index fiber (50/125 μm and injected into the tissue. The reflectance photons are collected by 8 independent 1 mm fibers and detected by a 16-anode photomultiplier. A time-correlated single photon counting PC board is used for the parallel acquisition of the curves. Simultaneous estimate of the transport scattering and absorption coefficients is achieved by best fitting of time-resolved reflectance curves with a standard model of Diffusion Theory. The performances of the system were tested on phantoms in terms of stability, reproducibility among channels, and accuracy in the determination of the optical properties. Preliminary in vivo measurements were performed on healthy volunteers to monitor spatial changes in calf (medical and lateral gastrocnemius) oxygen hemoglobin saturation and blood volume during dynamic plantar flexion exercise.