Time resolved spectroscopy of GRB 030501 using INTEGRAL

DEFF Research Database (Denmark)

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

2003-01-01

The gamma-ray instruments on-board INTEGRAL offer an unique opportunity to perform time resolved analysis on GRBs. The imager IBIS allows accurate positioning of GRBs and broad band spectral analysis, while SPI provides high resolution spectroscopy. GRB 030501 was discovered by the INTEGRAL Burst...... the Ulysses and RHESSI experiments....

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

DEFF Research Database (Denmark)

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

2014-01-01

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

Examining Electron-Boson Coupling Using Time-Resolved Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

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

2013-12-26

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

Time-resolved spectroscopy defines perturbation in molecules

International Nuclear Information System (INIS)

Ahmed, K.

1998-01-01

Time-resolved LIF spectroscopy is employed in order to investigate perturbations in different excited electronic state of alkali molecules. Dunham Coefficients are used to search the selected excited ro-vibrational level, which is overlap with the other nearby excited states. Lifetime measurement has been performed of more than 50 ro-vibrational levels. Out of these 25 levels were observed drastically different lifetimes from the other unperturbed levels. In this report, influence of different perturbations on this anomalous behavior is investigated and discussed. (author)

Plasma polarization spectroscopy. Time resolved spectroscopy in soft x-ray region on recombining plasma

International Nuclear Information System (INIS)

Iwamae, Atsushi; Hasuo, Masahiro; Atake, Makoto; Hasegawa, Noboru; Kawachi, Tetsuya

2007-01-01

We present an experimental study of polarization of emission radiations from recombining plasmas generated by the interaction of 60 fs ultra-short laser pulses with a gas jet. Time-resolved spectroscopy with a temporal resolution of 5 ps with repetitive accumulation is used to follow the recombination time histories. (author)

Generation of pulsed far-infrared radiation and its application for far-infrared time-resolved spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kondo, Yasuhiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

1996-07-01

So-called time-resolved spectroscopy technique has been used from old time as the means for studying the dynamic optical property, light-induced reaction and so on of matters. As an example, there is the method called pump and probe, and here, the wavelength of this probe light is the problem. If the object energy region is limited to about 0.1 eV, fast time-resolved spectroscopy is feasible relatively easily. However, energy region is extended to low energy region, the light source which is available as the pulsed probe light having sufficient intensity is limited. In this paper, the attempt of time-resolved spectroscopy utilizing coherent radiation, which has ended in failure, and the laser pulse-induced far-infrared radiation which can be utilized as new far-infrared probe light are reported. The reason why far-infrared radiation is used is explained. The attempt of time-resolved spectroscopy using NaCl crystals is reported on the equipment, the method of measuring absorption spectra and the results. Laser pulse-induced far-infrared radiation and the method of generating it are described. The multi-channel detector for far-infrared radiation which was made for trial is shown. (K.I.)

Time-resolved and doppler-reduced laser spectroscopy on atoms

International Nuclear Information System (INIS)

Bergstroem, H.

1991-10-01

Radiative lifetimes have been studied in neutral boron, carbon, silicon and strontium, in singly ionized gadolinium and tantalum and in molecular carbon monoxide and C 2 . The time-resolved techniques were based either on pulsed lasers or pulse-modulated CW lasers. Several techniques have been utilized for the production of free atoms and ions such as evaporation into an atomic beam, sputtering in hollow cathodes and laser-produced plasmas. Hyperfine interactions in boron, copper and strontium have been examined using quantum beat spectroscopy, saturation spectroscopy and collimated atomic beam spectroscopy. Measurement techniques based on effusive hollow cathodes as well as laser produced plasmas in atomic physics have been developed. Investigations on laser produced plasmas using two colour beam deflection tomography for determination of electron densities have been performed. Finally, new possibilities for view-time-expansion in light-in-flight holography using mode-locked CW lasers have been demonstrated. (au)

Space- and time-resolved raman and breakdown spectroscopy: advanced lidar techniques

Science.gov (United States)

Silviu, Gurlui; Marius Mihai, Cazacu; Adrian, Timofte; Oana, Rusu; Georgiana, Bulai; Dimitriu, Dan

2018-04-01

DARLIOES - the advanced LIDAR is based on space- and time-resolved RAMAN and breakdown spectroscopy, to investigate chemical and toxic compounds, their kinetics and physical properties at high temporal (2 ns) and spatial (1 cm) resolution. The high spatial and temporal resolution are needed to resolve a large variety of chemical troposphere compounds, emissions from aircraft, the self-organization space charges induced light phenomena, temperature and humidity profiles, ice nucleation, etc.

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....

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....

Liver Status Assessment by Spectrally and Time Resolved IR Detection of Drug Induced Breath Gas Changes

Directory of Open Access Journals (Sweden)

Tom Rubin

2016-05-01

Full Text Available The actual metabolic capacity of the liver is crucial for disease identification, liver therapy, and liver tumor resection. By combining induced drug metabolism and high sensitivity IR spectroscopy of exhaled air, we provide a method for quantitative liver assessment at bedside within 20 to 60 min. Fast administration of 13C-labelled methacetin induces a fast response of liver metabolism and is tracked in real-time by the increase of 13CO2 in exhaled air. The 13CO2 concentration increase in exhaled air allows the determination of the metabolic liver capacity (LiMAx-test. Fluctuations in CO2 concentration, pressure and temperature are minimized by special gas handling, and tracking of several spectrally resolved CO2 absorption bands with a quantum cascade laser. Absorption measurement of different 12CO2 and 13CO2 rotation-vibration transitions in the same time window allows for multiple referencing and reduction of systematic errors. This FLIP (Fast liver investigation package setup is being successfully used to plan operations and determine the liver status of patients.

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...

Development of soft x-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU

Energy Technology Data Exchange (ETDEWEB)

Ogawa, Manami; Yamamoto, Susumu; Nakamura, Fumitaka; Yukawa, Ryu; Fukushima, Akiko; Harasawa, Ayumi; Kakizaki, Akito; Matsuda, Iwao [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8581 (Japan); Kousa, Yuka; Kondoh, Hiroshi [Department of Chemistry, Keio University, Yokohama 223-8522 (Japan); Tanaka, Yoshihito [RIKEN/SPring-8 Center, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

2012-02-15

We have developed a soft x-ray time-resolved photoemission spectroscopy system using synchrotron radiation (SR) at SPring-8 BL07LSU and an ultrashort pulse laser system. Two-dimensional angle-resolved measurements were performed with a time-of-flight-type analyzer. The photoemission spectroscopy system is synchronized to light pulses of SR and laser using a time control unit. The performance of the instrument is demonstrated by mapping the band structure of a Si(111) crystal over the surface Brillouin zones and observing relaxation of the surface photo-voltage effect using the pump (laser) and probe (SR) method.

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

International Nuclear Information System (INIS)

Hedqvist, A.; Rachlew-Kaellne, E.

1998-01-01

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 Z eff together with a description of the interpretation and the equipment are presented. (author)

Time-resolved tunable diode laser absorption spectroscopy of pulsed plasma

Czech Academy of Sciences Publication Activity Database

Adámek, Petr; Olejníček, Jiří; Čada, Martin; Kment, Š.; Hubička, Zdeněk

2013-01-01

Roč. 38, č. 14 (2013), s. 2428-2430 ISSN 0146-9592 R&D Projects: GA MŠk LH12045; GA ČR(CZ) GAP205/11/0386; GA MŠk LD12002; GA MŠk LH12043 Institutional support: RVO:68378271 Keywords : diode laser s * plasma diagnostics * absorption spectroscopy * time resolved Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.179, year: 2013

Time-resolved spectroscopy using a chopper wheel as a fast shutter

International Nuclear Information System (INIS)

Wang, Shicong; Wendt, Amy E.; Boffard, John B.; Lin, Chun C.

2015-01-01

Widely available, small form-factor, fiber-coupled spectrometers typically have a minimum exposure time measured in milliseconds, and thus cannot be used directly for time-resolved measurements at the microsecond level. Spectroscopy at these faster time scales is typically done with an intensified charge coupled device (CCD) system where the image intensifier acts as a “fast” electronic shutter for the slower CCD array. In this paper, we describe simple modifications to a commercially available chopper wheel system to allow it to be used as a “fast” mechanical shutter for gating a fiber-coupled spectrometer to achieve microsecond-scale time-resolved optical measurements of a periodically pulsed light source. With the chopper wheel synchronized to the pulsing of the light source, the time resolution can be set to a small fraction of the pulse period by using a chopper wheel with narrow slots separated by wide spokes. Different methods of synchronizing the chopper wheel and pulsing of the light sources are explored. The capability of the chopper wheel system is illustrated with time-resolved measurements of pulsed plasmas

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

2013-11-07

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.

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.

Time-resolved photoelectron spectroscopy of nitrobenzene and its aldehydes

Science.gov (United States)

Schalk, Oliver; Townsend, Dave; Wolf, Thomas J. A.; Holland, David M. P.; Boguslavskiy, Andrey E.; Szöri, Milan; Stolow, Albert

2018-01-01

We report the first femtosecond time-resolved photoelectron spectroscopy study of 2-, 3- and 4-nitrobenzaldehyde (NBA) and nitrobenzene (NBE) in the gas phase upon excitation at 200 nm. In 3- and 4-NBA, the dynamics follow fast intersystem crossing within 1-2 picoseconds. In 2-NBA and NBE, the dynamics are faster (∼ 0.5 ps). 2-NBA undergoes hydrogen transfer similar to solution phase dynamics. NBE either releases NO2 in the excited state or converts internally back to the ground state. We discuss why these channels are suppressed in the other nitrobenzaldehydes.

Probing specific molecular processes and intermediates by time-resolved Fourier transform infrared spectroscopy: application to the bacteriorhodopsin photocycle.

Science.gov (United States)

Lórenz-Fonfría, Víctor A; Kandori, Hideki; Padrós, Esteve

2011-06-23

We present a general approach for probing the kinetics of specific molecular processes in proteins by time-resolved Fourier transform infrared (IR) spectroscopy. Using bacteriorhodopsin (bR) as a model we demonstrate that by appropriately monitoring some selected IR bands it is possible obtaining the kinetics of the most important events occurring in the photocycle, namely changes in the chromophore and the protein backbone conformation, and changes in the protonation state of the key residues implicated in the proton transfers. Besides confirming widely accepted views of the bR photocycle, our analysis also sheds light into some disputed issues: the degree of retinal torsion in the L intermediate to respect the ground state; the possibility of a proton transfer from Asp85 to Asp212; the relationship between the protonation/deprotonation of Asp85 and the proton release complex; and the timing of the protein backbone dynamics. By providing a direct way to estimate the kinetics of photocycle intermediates the present approach opens new prospects for a robust quantitative kinetic analysis of the bR photocycle, which could also benefit the study of other proteins involved in photosynthesis, in phototaxis, or in respiratory chains.

New techniques of time-resolved infrared and Raman spectroscopy using ultrashort laser pulses

International Nuclear Information System (INIS)

Laubereau, A.

1986-01-01

Considerable progress has been made in recent years in the field of spectroscopic applications of ultrashort laser pulses. This paper examines two approaches toward studying ultrafast relaxation processes in condensed matter: an IR technique which complements coherent Raman scattering; and a Fourier Raman method with high frequency resolution. The time domain IR spectroscopy technique has been applied to various vibration-rotation transitions of pure HCl gas and in mixtures with Ar buffer gas. The advantage of the time domain measurements instead of frequency spectroscopy is readily visualized when one recalls that a frequency resolution of 10 -3 cm -1 corresponds to time observations over 10 -8 , which are readily feasible. As a first demonstration of the FT-Raman technique the author presents experimental data on the Q-branch of the v 1 -vibrational mode of methane. An example for the experimental data obtained approximately 2 mm behind the nozzle is presented; the coherent anti-Stokes Raman signal is plotted versus delay time. A complicated beating structure and the decay of the signal envelope are readily seen. The desired spectroscopic information is obtained by numerical Fourier transformation of the experimental points presented

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.)

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...

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

Science.gov (United States)

Milne, Chris J.; Pham, Van-Thai; Gawelda, Wojciech; van der Veen, Renske M.; El Nahhas, Amal; Johnson, Steven L.; Beaud, Paul; Ingold, Gerhard; Lima, Frederico; Vithanage, Dimali A.; Benfatto, Maurizio; Grolimund, Daniel; Borca, Camelia; Kaiser, Maik; Hauser, Andreas; Abela, Rafael; Bressler, Christian; Chergui, Majed

2009-11-01

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 Å. 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.

Time-resolved resonance fluorescence spectroscopy for study of chemical reactions in laser-induced plasmas.

Science.gov (United States)

Liu, Lei; Deng, Leimin; Fan, Lisha; Huang, Xi; Lu, Yao; Shen, Xiaokang; Jiang, Lan; Silvain, Jean-François; Lu, Yongfeng

2017-10-30

Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al 2 O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al 2 O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O 2 chemistry in air.

Biochemical applications of FT-IR spectroscopy

NARCIS (Netherlands)

Pistorius, A.M.A.

1996-01-01

This thesis describes the use of (FT-)IR spectroscopy in general biochemical research. In chapter 3, IR spectroscopy is used in the quantitation of residual detergent after reconstitution of an integral membrane protein in a pre-defined lipid matrix. This chapter discusses the choice of the

Frame-Transfer Gating Raman Spectroscopy for Time-Resolved Multiscalar Combustion Diagnostics

Science.gov (United States)

Nguyen, Quang-Viet; Fischer, David G.; Kojima, Jun

2011-01-01

Accurate experimental measurement of spatially and temporally resolved variations in chemical composition (species concentrations) and temperature in turbulent flames is vital for characterizing the complex phenomena occurring in most practical combustion systems. These diagnostic measurements are called multiscalar because they are capable of acquiring multiple scalar quantities simultaneously. Multiscalar diagnostics also play a critical role in the area of computational code validation. In order to improve the design of combustion devices, computational codes for modeling turbulent combustion are often used to speed up and optimize the development process. The experimental validation of these codes is a critical step in accepting their predictions for engine performance in the absence of cost-prohibitive testing. One of the most critical aspects of setting up a time-resolved stimulated Raman scattering (SRS) diagnostic system is the temporal optical gating scheme. A short optical gate is necessary in order for weak SRS signals to be detected with a good signal- to-noise ratio (SNR) in the presence of strong background optical emissions. This time-synchronized optical gating is a classical problem even to other spectroscopic techniques such as laser-induced fluorescence (LIF) or laser-induced breakdown spectroscopy (LIBS). Traditionally, experimenters have had basically two options for gating: (1) an electronic means of gating using an image intensifier before the charge-coupled-device (CCD), or (2) a mechanical optical shutter (a rotary chopper/mechanical shutter combination). A new diagnostic technology has been developed at the NASA Glenn Research Center that utilizes a frame-transfer CCD sensor, in conjunction with a pulsed laser and multiplex optical fiber collection, to realize time-resolved Raman spectroscopy of turbulent flames that is free from optical background noise (interference). The technology permits not only shorter temporal optical gating (down

Time resolved optical emission spectroscopy of cross-beam pulsed laser ablation on graphite targets

International Nuclear Information System (INIS)

Sangines, R.; Sanchez Ake, C.; Sobral, H.; Villagran-Muniz, M.

2007-01-01

Cross-beam pulsed laser ablation with two delayed lasers is performed on two perpendicular graphite targets. The time delay between lasers is varied by up to 5 μs, and physical changes on the second plasma, due to the interaction with the first generated one, are determined by time resolved optical emission spectroscopy

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

KAUST Repository

Dean, Jacob C.; Zhang, Ruomeng; Hallani, Rawad K.; Pensack, Ryan D.; Sanders, Samuel N.; Oblinsky, Daniel G.; Parkin, Sean R.; Campos, Luis M.; Anthony, John E.; Scholes, Gregory D.

2017-01-01

carried out in toluene and acetone solution via absorption and fluorescence spectroscopy, and their photo-initiated dynamics were investigated with time-resolved fluorescence (TRF) and transient absorption (TA) spectroscopy. In accordance

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...... photoconductivity compared to P3HT alone, consistent with efficient charge transfer. The photoconductivity dynamics show fast, picosecond trapping or recombination in the hybrid blend while the all-organic film shows no such loss of mobile charge over ns time scales. The ac conductivity for all samples is well...

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

International Nuclear Information System (INIS)

Kimura, Takaumi; Kato, Yoshiharu; Meinrath, G.; Yoshida, Zenko; Choppin, G.R.

1995-01-01

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)

Characterization of type I, II, III, IV, and V collagens by time-resolved laser-induced fluorescence spectroscopy

Science.gov (United States)

Marcu, Laura; Cohen, David; Maarek, Jean-Michel I.; Grundfest, Warren S.

2000-04-01

The relative proportions of genetically distinct collagen types in connective tissues vary with tissue type and change during disease progression, development, wound healing, aging. This study aims to 1) characterize the spectro- temporal fluorescence emission of fiber different types of collagen and 2) assess the ability of time-resolved laser- induced fluorescence spectroscopy to distinguish between collagen types. Fluorescence emission of commercially available purified samples was induced with nitrogen laser excitation pulses and detected with a MCP-PMT connected to a digital storage oscilloscope. The recorded time-resolved emission spectra displayed distinct fluorescence emission characteristics for each collagen type. The time domain information complemented the spectral domain intensity data for improved discrimination between different collagen types. Our results reveal that analysis of the fluorescence emission can be used to characterize different species of collagen. Also, the results suggest that time-resolved spectroscopy can be used for monitoring of connective tissue matrix composition changes due to various pathological and non-pathological conditions.

Time-resolved ultraviolet laser-induced breakdown spectroscopy for organic material analysis

Energy Technology Data Exchange (ETDEWEB)

Baudelet, Matthieu; Boueri, Myriam [Laboratoire de Spectrometrie Ionique et Moleculaire, Universite Claude Bernard Lyon 1, UMR CNRS 5579, 43, Bd. du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France); Yu Jin [Laboratoire de Spectrometrie Ionique et Moleculaire, Universite Claude Bernard Lyon 1, UMR CNRS 5579, 43, Bd. du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France)], E-mail: jin.yu@lasim.univ-lyon1.fr; Mao, Samuel S; Piscitelli, Vincent; Xianglei, Mao; Russo, Richard E [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2007-12-15

Ultraviolet pulses (266 nm) delivered by a quadrupled Nd:YAG laser were used to analyze organic samples with laser-induced breakdown spectroscopy (LIBS). We present characteristics of the spectra obtained from organic samples with special attentions on the emissions of organic elements, O and N, and molecular bonds CN. The choice of these atomic or molecular species is justified on one hand, by the importance of these species to specify organic or biological materials; and on the other hand by the possible interferences with ambient air when laser ablation takes place in the atmosphere. Time-resolved LIBS was used to determine the time-evolution of line intensity emitted from these species. We demonstrate different kinetic behaviors corresponding to different origins of emitters: native atomic or molecular species directly vaporized from the sample or those generated through dissociation or recombination due to interaction between laser-induced plasma and air molecules. Our results show the ability of time-resolved UV-LIBS for detection and identification of native atomic or molecular species from an organic sample.

Time-resolved fluorescence spectroscopy

International Nuclear Information System (INIS)

Gustavsson, Thomas; Mialocq, Jean-Claude

2007-01-01

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)

Time-resolved pump and probe x-ray absorption fine structure spectroscopy at beamline P11 at PETRA III

Energy Technology Data Exchange (ETDEWEB)

Göries, D., E-mail: dennis.goeries@desy.de; Roedig, P.; Stübe, N.; Meyer, J.; Warmer, M.; Weckert, E.; Meents, A., E-mail: alke.meents@desy.de [DESY Photon Science, Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg (Germany); Dicke, B.; Naumova, M.; Rübhausen, M. [Center for Free-Electron Laser Science (CFEL), Luruper Chaussee 149, 22761 Hamburg (Germany); Galler, A.; Gawelda, W.; Geßler, P.; Sotoudi Namin, H.; Beckmann, A. [European XFEL, Albert-Einstein Ring 19, 22761 Hamburg (Germany); Britz, A.; Bressler, C. [European XFEL, Albert-Einstein Ring 19, 22761 Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg (Germany); Schlie, M. [Institut für Experimentalphysik, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany)

2016-05-15

We report about the development and implementation of a new setup for time-resolved X-ray absorption fine structure spectroscopy at beamline P11 utilizing the outstanding source properties of the low-emittance PETRA III synchrotron storage ring in Hamburg. Using a high intensity micrometer-sized X-ray beam in combination with two positional feedback systems, measurements were performed on the transition metal complex fac-Tris[2-phenylpyridinato-C2,N]iridium(III) also referred to as fac-Ir(ppy){sub 3}. This compound is a representative of the phosphorescent iridium(III) complexes, which play an important role in organic light emitting diode (OLED) technology. The experiment could directly prove the anticipated photoinduced charge transfer reaction. Our results further reveal that the temporal resolution of the experiment is limited by the PETRA III X-ray bunch length of ∼103 ps full width at half maximum (FWHM).

Time-resolved x-ray laser induced photoelectron spectroscopy of isochoric heated copper

International Nuclear Information System (INIS)

Nelson, A.J.; Dunn, J.; Hunter, J.; Widmann, K.

2005-01-01

Time-resolved x-ray photoelectron spectroscopy is used to probe the nonsteady-state evolution of the valence band electronic structure of laser heated ultrathin (50 nm) copper. A metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.1-2.5 mJ laser energy focused in a large 500x700 μm 2 spot to create heated conditions of 0.07-1.8x10 12 W cm -2 intensity. Valence band photoemission spectra are presented showing the changing occupancy of the Cu 3d level with heating are presented. These picosecond x-ray laser induced time-resolved photoemission spectra of laser-heated ultrathin Cu foil show dynamic changes in the electronic structure. The ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials

Application of microfluidic devices for time resolved FTIR spectroscopy

International Nuclear Information System (INIS)

Wagner, C.

2012-01-01

Within this thesis, micro fluidic mixers, operated in continuous flow mode, were used for time resolved FTIR studies of chemical reactions in aqueous solution. Any chemical reaction, that can be started upon mixing two reagents, can be examined with this technique. The mixing channel also serves as the observation window for the IR measurements. The actual measurements take place at well defined spots along this channel, corresponding to specific reaction times: moving the measurement spot (100 × 100 μm 2 ) towards the entry yields shorter reaction times, moving it towards the channel's end gives longer reaction times. The temporal resolution of the experiment depends on the flow rate inside the mixing channel and the spacing between subsequent measurement points. Fast flow rates, limited by the back pressure of the mixer leading to leakages, allow time resolutions in the sub-millisecond time range using a standard FTIR microscope, whereas slow flow rates allow the measurement of reaction times up to 1000 ms. Evaluating the mixer using a fast chemical reaction resulted in mixing times of approximately 5 ms and a homogeneous distribution of the liquids across the width of the mixing channel. The mixer was then used for the measurement of the H/D exchange on carbohydrates, the complex formaldehyde sulfite clock reaction, and the folding of the protein ubiquitin from its native to the ''A'' state, induced by mixing it with an acidified methanol solution. For cleaning the mixer a software tool, called ATLAS, was developed in LabVIEW, which was used to automatize the necessary cleaning steps performed by a dedicated flow system. Additionally, the micro mixer technology was combined with the step scan measurement technique using a beam condenser focusing the IR beam of an FTIR spectrometer down to a spot size of 1 mm diameter and through the mixer. The laser light, initiating the chemical reaction inside the mixing channel, was coupled into the focusing unit using a

IR Cards: Inquiry-Based Introduction to Infrared Spectroscopy

Science.gov (United States)

Bennett, Jacqueline; Forster, Tabetha

2010-01-01

As infrared spectroscopy (IR) is frequently used in undergraduate organic chemistry courses, an inductive introduction to IR spectroscopy that uses index cards printed with spectra, structures, and chemical names is described. Groups of students are given an alphabetized deck of these "IR cards" to sort into functional groups. The students then…

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.

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

was studied with SF6 pressures of 5-1000 mbar at 298 K. Comparative studies were carried out by monitoring the decay kinetics of NO2 at 445 nm using pressures of 100-1000 mbar at 295 and 341 K. The observed pressure dependence is represented in terms of a fall-off curve with the following values......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...

Laser induced breakdown spectroscopy of the uranium including calcium. Time resolved measurement spectroscopic analysis (Contract research)

International Nuclear Information System (INIS)

Akaoka, Katsuaki; Maruyama, Youichiro; Oba, Masaki; Miyabe, Masabumi; Otobe, Haruyoshi; Wakaida, Ikuo

2010-05-01

For the remote analysis of low DF TRU (Decontamination Factor Transuranic) fuel, Laser Breakdown Spectroscopy (LIBS) was applied to uranium oxide including a small amount of calcium oxide. The characteristics, such as spectrum intensity and plasma excitation temperature, were measured using time-resolved spectroscopy. As a result, in order to obtain the stable intensity of calcium spectrum for the uranium spectrum, it was found out that the optimum observation delay time of spectrum is 4 microseconds or more after laser irradiation. (author)

Challenge for real-time and real-space resolved spectroscopy of surface chemical reactions. Aiming at trace of irreversible and inhomogeneous reactions

International Nuclear Information System (INIS)

Amemiya, Kenta

2015-01-01

A novel experimental technique, time-resolved wavelength-dispersive soft X-ray imaging spectroscopy, is proposed in order to achieve real-time and real-space resolved spectroscopy for the observation of irreversible and inhomogeneous surface chemical reactions. By combining the wavelength-dispersed soft X rays, in which the X-ray wavelength (photon energy) changes as a function of position on the sample, with the photoelectron emission microscope, the soft X-ray absorption spectra are separately obtained at different positions on the sample without scanning the X-ray monochromator. Therefore, the real-time resolved measurement of site-selective soft X-ray absorption spectroscopy is realized in one event without repeating the chemical reaction. It is expected that the spatial distribution of different chemical species is traced during the surface chemical reaction, which is essential to understand the reaction mechanism. (author)

Visualizing Infrared (IR) Spectroscopy with Computer Animation

Science.gov (United States)

Abrams, Charles B.; Fine, Leonard W.

1996-01-01

IR Tutor, an interactive, animated infrared (IR) spectroscopy tutorial has been developed for Macintosh and IBM-compatible computers. Using unique color animation, complicated vibrational modes can be introduced to beginning students. Rules governing the appearance of IR absorption bands become obvious because the vibrational modes can be visualized. Each peak in the IR spectrum is highlighted, and the animation of the corresponding normal mode can be shown. Students can study each spectrum stepwise, or click on any individual peak to see its assignment. Important regions of each spectrum can be expanded and spectra can be overlaid for comparison. An introduction to the theory of IR spectroscopy is included, making the program a complete instructional package. Our own success in using this software for teaching and research in both academic and industrial environments will be described. IR Tutor consists of three sections: (1) The 'Introduction' is a review of basic principles of spectroscopy. (2) 'Theory' begins with the classical model of a simple diatomic molecule and is expanded to include larger molecules by introducing normal modes and group frequencies. (3) 'Interpretation' is the heart of the tutorial. Thirteen IR spectra are analyzed in detail, covering the most important functional groups. This section features color animation of each normal mode, full interactivity, overlay of related spectra, and expansion of important regions. This section can also be used as a reference.

Spectroscopy and reactions of vibrationally excited transient molecules

Energy Technology Data Exchange (ETDEWEB)

Dai, H.L. [Univ. of Pennsylvania, Philadelphia (United States)

1993-12-01

Spectroscopy, energy transfer and reactions of vibrationally excited transient molecules are studied through a combination of laser-based excitation techniques and efficient detection of emission from the energized molecules with frequency and time resolution. Specifically, a Time-resolved Fourier Transform Emission Spectroscopy technique has been developed for detecting dispersed laser-induced fluorescence in the IR, visible and UV regions. The structure and spectroscopy of the excited vibrational levels in the electronic ground state, as well as energy relaxation and reactions induced by specific vibronic excitations of a transient molecule can be characterized from time-resolved dispersed fluorescence in the visible and UV region. IR emissions from highly vibrational excited levels, on the other hand, reveal the pathways and rates of collision induced vibrational energy transfer.

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

Science.gov (United States)

Alberding, Brian G.; Heilweil, Edwin J.

2015-09-01

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

Excited-State Dynamics of a DNA Duplex in a Deep Eutectic Solvent Probed by Femtosecond Time-Resolved IR Spectroscopy.

Science.gov (United States)

de La Harpe, Kimberly; Kohl, Forrest R; Zhang, Yuyuan; Kohler, Bern

2018-03-08

To better understand how the solvent influences excited-state deactivation in DNA strands, femtosecond time-resolved IR (fs-TRIR) pump-probe measurements were performed on a d(AT) 9 ·d(AT) 9 duplex dissolved in a deep eutectic solvent (DES) made from choline chloride and ethylene glycol in a 1:2 mol ratio. This solvent, known as ethaline, is a member of a class of ionic liquids capable of solubilizing DNA with minimal disruption to its secondary structure. UV melting analysis reveals that the duplex studied here melts at 18 °C in ethaline compared to 50 °C in aqueous solution. Ethaline has an excellent transparency window that facilitates TRIR measurements in the double-bond stretching region. Transient spectra recorded in deuterated ethaline at room temperature indicate that photoinduced intrastrand charge transfer occurs from A to T, yielding the same exciplex state previously detected in aqueous solution. This state decays via charge recombination with a lifetime of 380 ± 10 ps compared to the 300 ± 10 ps lifetime measured earlier in D 2 O solution. The TRIR data strongly suggest that the long-lived exciplex forms exclusively in the solvated duplex, and not in the denatured single strands, which appear to have little, if any, base stacking. The longer lifetime of the exciplex state in the DES compared to aqueous solution is suggested to arise from reduced stabilization of the charge transfer state, resulting in slower charge recombination on account of Marcus inverted behavior.

Ionic classification of Xe laser lines: A new approach through time resolved spectroscopy

International Nuclear Information System (INIS)

Schinca, D.; Duchowicz, R.; Gallardo, M.

1992-01-01

Visible and UV laser emission from a highly ionized pulsed Xe plasma was studied in relation to the ionic assignment of the laser lines. Time-resolved spectroscopy was used to determine the ionic origin of the studied lines. The results are in agreement with an intensity versus pressure analysis performed over the same wavelength range. From the temporal behaviour of the spontaneous emission, a probable classification can be obtained. (author). 7 refs, 7 figs, 1 tab

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 ...

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

National Research Council Canada - National Science Library

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

2007-01-01

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

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

Science.gov (United States)

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

2012-04-01

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

Isolated Gramicidin Peptides Probed by IR Spectroscopy

NARCIS (Netherlands)

Rijs, A. M.; Kabelac, M.; Abo-Riziq, A.; Hobza, P.; de Vries, M. S.

2011-01-01

We report double-resonant IR/UV ion-dip spectroscopy of neutral gramicidin peptides in the gas phase. The IR spectra of gramicidin A and C, recorded in both the 1000 cm(-1) to 1800 cm(-1) and the 2700 to 3750 cm(-1) region, allow structural analysis. By studying this broad IR range, various local

Time-resolved pump-probe X-ray absorption fine structure spectroscopy of Gaq3

International Nuclear Information System (INIS)

Dicke, Benjamin

2013-01-01

Gallium(tris-8-hydroxyquinoline) (Gaq 3 ) belongs to a class of metal organic compounds, used as electron transport layer and emissive layer in organic light emitting diodes. Many research activities have concentrated on the optical and electronic properties, especially of the homologue molecule aluminum(tris-8-hydroxyquinoline) (Alq 3 ). Knowledge of the first excited state S 1 structure of these molecules could provide deeper insight into the processes involved into the operation of electronic devices, such as OLEDs and, hence, it could further improve their efficiency and optical properties. Until now the excited state structure could not be determined experimentally. Most of the information about this structure mainly arises from theoretical calculations. X-ray absorption fine structure (XAFS) spectroscopy is a well developed technique to determine both, the electronic and the geometric properties of a sample. The connection of ultrashort pulsed X-ray sources with a pulsed laser system offers the possibility to use XAFS as a tool for studying the transient changes of a sample induced by a laser pulse. In the framework of this thesis a new setup for time-resolved pump-probe X-ray absorption spectroscopy at PETRA III beamline P11 was developed for measuring samples in liquid form. In this setup the sample is pumped into its photo-excited state by a femtosecond laser pump pulse with 343 nm wavelength and after a certain time delay probed by an X-ray probe pulse. In this way the first excited singlet state S 1 of Gaq 3 dissolved in benzyl alcohol was analyzed. A structural model for the excited state structure of the Gaq 3 molecule based on the several times reproduced results of the XAFS experiments is proposed. According to this model it was found that the Ga-N A bond length is elongated, while the Ga-O A bond length is shortened upon photoexcitation. The dynamics of the structural changes were not the focus of this thesis. Nevertheless the excited state lifetime

Time-resolved luminescent spectroscopy of YAG:Ce single crystal and single crystalline films

International Nuclear Information System (INIS)

Zorenko, Yu.; Gorbenko, V.; Savchyn, V.; Vozniak, T.; Puzikov, V.; Danko, A.; Nizhankovski, S.

2010-01-01

The peculiarities of the luminescence and energy transfer from YAG host to the emission centers formed by the Y Al antisite defects and Ce 3+ ions have been studied in YAG:Ce single crystals, grown from the melt by modified Bridgman method in Ar and CO 2 + H 2 atmospheres, and YAG:Ce single crystalline film, grown by liquid phase epitaxy method, using the comparative time-resolved luminescent spectroscopy under excitation by synchrotron radiation in the range of fundamental adsorption of this garnet.

Time-resolved resonance Raman spectroscopy of radiation-chemical processes

International Nuclear Information System (INIS)

Tripathi, G.N.R.

1983-01-01

A tunable pulsed laser Raman spectrometer for time resolved Raman studies of radiation-chemical processes is described. This apparatus utilizes the state of art optical multichannel detection and analysis techniques for data acquisition and electron pulse radiolysis for initiating the reactions. By using this technique the resonance Raman spectra of intermediates with absorption spectra in the 248-900 nm region, and mean lifetimes > 30 ns can be examined. This apparatus can be used to time resolve the vibrational spectral overlap between transients absorbing in the same region, and to follow their decay kinetics by monitoring the well resolved Raman peaks. For kinetic measurements at millisecond time scale, the Raman technique is preferable over optical absorption method where low frequency noise is quite bothersome. A time resolved Raman study of the pulse radiolytic oxidation of aqueous tetrafluorohydroquinone and p-methoxyphenol is briefly discussed. 15 references, 5 figures

NO kinetics in pulsed low-pressure nitrogen plasmas studied by time resolved quantum cascade laser absorption spectroscopy

NARCIS (Netherlands)

Welzel, S.; Guaitella, O.; Lazzaroni, C.; Pintassilgo, C.; Rousseau, A.; Röpcke, J.

2011-01-01

Time-resolved quantum cascade laser absorption spectroscopy at 1897 cm-1 (5.27 µm) has been applied to study the NO(X) kinetics on the micro- and millisecond time scale in pulsed low-pressure N2/NO dc discharges. Experiments have been performed under flowing and static gas conditions to infer the

Exploring the Dynamics of Superconductors by Time-Resolved Far-Infrared Spectroscopy

International Nuclear Information System (INIS)

Carr, G. L.; Lobo, R. P. S. M.; LaVeigne, J.; Reitze, D. H.; Tanner, D. B.

2000-01-01

We have examined the recombination of excess quasiparticles in superconducting Pb by time-resolved far-infrared spectroscopy using a pulsed synchrotron source. The energy gap shift calculated by Owen and Scalapino [Phys. Rev. Lett. 28, 1559 (1972)] is directly observed, as is the associated reduction in the Cooper pair density. The relaxation process involves a two-component decay; the faster (∼200 ps) is associated with the actual (effective) recombination process, while the slower (∼10 to 100ns) is due to heat transport across the film/substrate interface. The temperature dependence of the recombination process between 0.5T c and 0.85T c is in good agreement with theory

Time-resolved spectroscopy of plasma resonances in highly excited silicon and germanium

International Nuclear Information System (INIS)

Huang, C.Y.; Malvezzi, A.M.; Bloembergen, N.; Kurz, H.

1985-01-01

The dynamics of the electron-hole plasma in silicon and germanium samples irradiated by 20 ps. 532 nm laser pulses has been investigated in the near infrared by the time-resolved picosecond optical spectroscopy. The experimental reflectivities and transmission are compared with the predictions of the thermal model for degenerate carrier distributions through the Drude formalism. Above a certain fluence, a significant deviation between measured and calculated values indicates a strong increase of the recombination rate as soon as the plasma resonances become comparable with the band gaps. These new plasmon-aided recombination channels are particularly pronounced in germanium. 15 refs., 8 figs

Time-resolved X-ray photoelectron spectroscopy techniques for the study of interfacial charge dynamics

Energy Technology Data Exchange (ETDEWEB)

Neppl, Stefan, E-mail: sneppl@lbl.gov; Gessner, Oliver

2015-04-15

Highlights: • Ultrafast interfacial charge transfer is probed with atomic site specificity. • Femtosecond X-ray photoelectron spectroscopy using a free electron laser. • Efficient and flexible picosecond X-ray photoelectron pump–probe scheme using synchrotron radiation. - Abstract: X-ray photoelectron spectroscopy (XPS) is one of the most powerful techniques to quantitatively analyze the chemical composition and electronic structure of surfaces and interfaces in a non-destructive fashion. Extending this technique into the time domain has the exciting potential to shed new light on electronic and chemical dynamics at surfaces by revealing transient charge configurations with element- and site-specificity. Here, we describe prospects and challenges that are associated with the implementation of picosecond and femtosecond time-resolved X-ray photoelectron spectroscopy at third-generation synchrotrons and X-ray free-electron lasers, respectively. In particular, we discuss a series of laser-pump/X-ray-probe photoemission experiments performed on semiconductor surfaces, molecule-semiconductor interfaces, and films of semiconductor nanoparticles that demonstrate the high sensitivity of time-resolved XPS to light-induced charge carrier generation, diffusion and recombination within the space charge layers of these materials. Employing the showcase example of photo-induced electronic dynamics in a dye-sensitized semiconductor system, we highlight the unique possibility to probe heterogeneous charge transfer dynamics from both sides of an interface, i.e., from the perspective of the molecular electron donor and the semiconductor acceptor, simultaneously. Such capabilities will be crucial to improve our microscopic understanding of interfacial charge redistribution and associated chemical dynamics, which are at the heart of emerging energy conversion, solar fuel generation, and energy storage technologies.

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.)

Towards a Molecular Movie: Real Time Observation of Hydrogen Bond Breaking by Transient 2D-IR Spectroscopy in a Cyclic Peptide

Science.gov (United States)

Kolano, Christoph; Helbing, Jan; Sander, Wolfram; Hamm, Peter

Transient two-dimensional infrared spectroscopy (T2D-IR) has been used to observe in real time the non-equilibrium structural dynamics of intramolecular hydrogen bond breaking in a small cyclic disulfide-bridged peptide.

Development of time-resolved electron momentum spectroscopy. Toward real-time imaging of frontier electrons in molecular reactions

International Nuclear Information System (INIS)

Yamazaki, M.; Takahashi, M.

2016-01-01

This report will introduce a new experimental technique to readers, which we would like to propose towards advances in the field of molecular reaction dynamics. It is time-resolved electron momentum spectroscopy and aims to take in momentum space snapshots of the rapid change of molecular orbitals, which is the driving force behind any structural changes occurring in transient molecules. Following a description of the working principle of the technique, some preliminary result will be presented in order to illustrate the current performance of the apparatus. (author)

Rare Earth Elements as Potential Biosignatures on Mars in SuperCam Time Resolved Laser Fluorescence Spectroscopy Data

Science.gov (United States)

Ollila, A.; Beyssac, O.; Sharma, S. K.; Misra, A. K.; Clegg, S. M.; Gauthier, M.; Wiens, R. C.; Maurice, S.; Gasnault, O.; Lanza, N.

2017-12-01

The rare earth elements (REE, La to Lu) are a group of elements with similar chemical properties that are generally present in geologic materials at trace concentrations. REEs may be concentrated via processes such as igneous fractional crystallization in accessory minerals, e.g. apatite, zircon, and titanite. Additionally, however, concentrations of REE may serve to identify regions of high astrobiological interest. For example, Fe-oxyhydroxide deposits in hydrothermal vent systems and biologically related manganese nodules may be enriched in REEs. REEs have not been measured in situ on Mars, therefore their prevalence and distribution on Mars is as yet unknown, except as observed in martian meteorites. SuperCam is a survey instrument that will analyze materials around the Mars 2020 rover using a variety of spectral techniques including laser-induced breakdown spectroscopy (LIBS), Raman, VIS-IR, and time-resolved laser fluorescence (TRLF) spectroscopy. Recently, the SuperCam Engineering Development Unit was tested at the Los Alamos National Laboratory for its capabilities to detect REEs in minerals using TRLF spectroscopy. While this instrument was not designed to precisely replicate the flight model, the spectral resolution and light transmission was sufficient to obtain TRLF spectra on a number of minerals demonstrating a variety of REE luminescent centers. These include apatite (Sm3+, Nd3+, Eu3+, Dy3+), fluorite (Ho3+, Sm3+, Dy3+, Nd3+), and zircon (Er3+, Pr3+, Nd3+). Future work includes expanding this suite to include minerals associated with biological activities, for example Mn-oxides (desert varnish and manganese nodules), hydrothermal Fe-oxides, and stromatolite-associated carbonates. In this way and in combination with its other techniques, SuperCam may direct the rover team to perform further analyses of similar samples by the in situ chemical and mineralogical suite of instruments, or aid in prioritization for sample return.

Recent trends in spin-resolved photoelectron spectroscopy

Science.gov (United States)

Okuda, Taichi

2017-12-01

Since the discovery of the Rashba effect on crystal surfaces and also the discovery of topological insulators, spin- and angle-resolved photoelectron spectroscopy (SARPES) has become more and more important, as the technique can measure directly the electronic band structure of materials with spin resolution. In the same way that the discovery of high-Tc superconductors promoted the development of high-resolution angle-resolved photoelectron spectroscopy, the discovery of this new class of materials has stimulated the development of new SARPES apparatus with new functions and higher resolution, such as spin vector analysis, ten times higher energy and angular resolution than conventional SARPES, multichannel spin detection, and so on. In addition, the utilization of vacuum ultra violet lasers also opens a pathway to the realization of novel SARPES measurements. In this review, such recent trends in SARPES techniques and measurements will be overviewed.

Time-resolved absorption measurements on OMEGA

International Nuclear Information System (INIS)

Jaanimagi, P.A.; DaSilva, L.; Delettrez, J.; Gregory, G.G.; Richardson, M.C.

1986-01-01

Time-resolved measurements of the incident laser light that is scattered and/or refracted from targets irradiated by the 24 uv-beam OMEGA laser at LLE, have provided some interesting features related to time-resolved absorption. The decrease in laser absorption characteristic of irradiating a target that implodes during the laser pulse has been observed. The increase in absorption expected as the critical density surface moves from a low to a high Z material in the target has also been noted. The detailed interpretation of these results is made through comparisons with simulation using the code LILAC, as well as with streak data from time-resolved x-ray imaging and spectroscopy. In addition, time and space-resolved imaging of the scattered light yields information on laser irradiation uniformity conditions on the target. The report consists of viewgraphs

Charge transport in nanostructured materials for solar energy conversion studied by time-resolved terahertz spectroscopy

Czech Academy of Sciences Publication Activity Database

Němec, Hynek; Kužel, Petr; Sundström, V.

2010-01-01

Roč. 215, 2-3 (2010), s. 123-139 ISSN 1010-6030 R&D Projects: GA ČR(CZ) GP202/09/P099; GA AV ČR(CZ) IAA100100902; GA MŠk LC512 Institutional research plan: CEZ:AV0Z10100520 Keywords : time-resolved terahertz spectroscopy * ultrafast dynamics * bulk heterojunction * semiconductor nanostructures * transport * mobility Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.243, year: 2010

Time-resolved spectroscopy of the probe fluorescence in the study of human blood protein dynamic structure on SR beam

International Nuclear Information System (INIS)

Dobretsov, G.E.; Kurek, N.K.; Syrejshchikova, T.I.; Yakimenko, M.N.; Clarke, D.T.; Jones, G.R.; Munro, I.H.

2000-01-01

Time-resolved spectroscopy on the SRS of the Daresbury Laboratory was used for the study of the human serum lipoproteins and human blood albumins with fluorescent probes K-37 and K-35, developed in Russia. The probe K-37 was found sensitive to the difference in dynamic properties of the lipid objects. Two sets of the parameters were used for the description of lipid dynamic structure: (1) time-resolved fluorescence spectra and (2) time-resolved fluorescence depolarization as a function of rotational mobility of lipid molecules. Each measured dynamic parameter reflected the monotonous changes of dynamic properties in the range: lipid spheres-very low density lipoproteins-low density lipoproteins-high density lipoproteins-phospholipid liposomes. The range is characterized by the increase of the ratio polar/ nonpolar lipids. Thus, time-resolved fluorescence could be used to detect some structural modifications in lipoproteins related to atherosclerosis and subsequent cardiovascular diseases development

Photolytic interruptions of the bacteriorhodopsin photocycle examined by time-resolved resonance raman spectroscopy.

Science.gov (United States)

Grieger, I; Atkinson, G H

1985-09-24

An investigation of the photolytic conditions used to initiate and spectroscopically monitor the bacteriorhodopsin (BR) photocycle utilizing time-resolved resonance Raman (TR3) spectroscopy has revealed and characterized two photoinduced reactions that interrupt the thermal pathway. One reaction involves the photolytic interconversion of M-412 and M', and the other involves the direct photolytic conversion of the BR-570/K-590 photostationary mixture either to M-412 and M' or to M-like intermediates within 10 ns. The photolytic threshold conditions describing both reactions have been quantitatively measured and are discussed in terms of experimental parameters.

The application of time-resolved luminescence spectroscopy to a remote uranyl sensor

International Nuclear Information System (INIS)

Varineau, P.T.; Duesing, R.; Wangen, L.E.

1991-01-01

Time resolved luminescence spectroscopy is an effective method for the determination of a wide range of uranyl concentrations in aqueous samples. We have applied this technique to the development of a remote sensing device using fiber optic cables coupled with a micro flow cell in order to probe for uranyl in aqueous samples. This sensor incorporates a Nafion membrane through which UO 2 2+ can diffuse in to a reaction/analysis chamber which holds phosphoric acid, a reagent which enhances the uranyl luminescence intensity and lifetime. With this device, anionic and fluorescing organic interferences could be eliminated, allowing for the determination of uranyl over a concentration range of 10 4 to 10 -9 M. 17 refs., 5 figs

Photoinduced charge transfer in a transition metal complex investigated by time-resolved X-ray absorption fine structure spectroscopy. Setup and experiment

International Nuclear Information System (INIS)

Goeries, Dennis

2015-02-01

In the framework of this thesis the development of a time-resolved X-ray absorption spectroscopy experiment and its application to fac-Ir(ppy) 3 is described. Such experiments require a very stable setup in terms of spatial and temporal accuracy. Therefore, the stability properties of the present installation were investigated in detail and continuously improved, in particular the synchronization of the ultrashort pulse laser system to the storage ring as well as the spatial stability of both X-ray and laser beam. Experiments utilizing the laser pump and X-ray probe configuration were applied on the green phosphorescence emitter complex fac-Ir(ppy) 3 dissolved in dimethyl sulfoxide. Structural and electronic changes were triggered by photoexcitation of the metal-to-ligand charge transfer band with ultrashort laser pulses at a wavelength of 343 nm. The excited triplet state spectrum was extracted from the measured pump-probe X-ray absorption spectrum using an ionic approximation. The results con rm the anticipated metal-to-ligand charge transfer as shown by an ionization potential shift of the iridium atom. The symmetry of the complex was found to be pseudo-octahedral. This allowed the first experimental determination of the bond length of fac-Ir(ppy) 3 in an octahedral approximation and revealed a decrease of bond length of the first coordination shell in the triplet state. The first and second-order decay kinetics of the triplet state were investigated in a combination of X-ray and laser based experiments and revealed self-quenching as well as triplet-triplet annihilation rate constants.

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

Science.gov (United States)

Niedzwiedzki, Dariusz M; Fuciman, Marcel; Kobayashi, Masayuki; Frank, Harry A; Blankenship, Robert E

2011-10-01

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. © Springer Science+Business Media B.V. 2011

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

International Nuclear Information System (INIS)

Ressler, T.; Jentoft, R.E.; Wienold, J.; Girgsdies, F.; Neisius, T.; Timpe, O.

2003-01-01

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 MoO 3 in propene and in propene and oxygen

Decay time shortening of fluorescence from donor-acceptor pair proteins using ultrafast time-resolved fluorescence resonance energy transfer spectroscopy

International Nuclear Information System (INIS)

Baba, Motoyoshi; Suzuki, Masayuki; Ganeev, Rashid A.; Kuroda, Hiroto; Ozaki, Tsuneyuki; Hamakubo, Takao; Masuda, Kazuyuki; Hayashi, Masahiro; Sakihama, Toshiko; Kodama, Tatsuhiko; Kozasa, Tohru

2007-01-01

We improved an ultrafast time-resolved fluorescence resonance energy transfer (FRET) spectroscopy system and measured directly the decrease in the fluorescence decay time of the FRET signal, without any entanglement of components in the picosecond time scale from the donor-acceptor protein pairs (such as cameleon protein for calcium ion indicator, and ligand-activated GRIN-Go proteins pair). The drastic decrease in lifetime of the donor protein fluorescence under the FRET condition (e.g. a 47.8% decrease for a GRIN-Go protein pair) proves the deformation dynamics between donor and acceptor fluorescent proteins in an activated state of a mixed donor-acceptor protein pair. This study is the first clear evidence of physical contact of the GRIN-Go proteins pair using time-resolved FRET system. G protein-coupled receptors (GPCRs) are the most important protein family for the recognition of many chemical substances at the cell surface. They are the targets of many drugs. Simultaneously, we were able to observe the time-resolved spectra of luminous proteins at the initial stage under the FRET condition, within 10 ns from excitation. This new FRET system allows us to trace the dynamics of the interaction between proteins at the ligand-induced activated state, molecular structure change and combination or dissociation. It will be a key technology for the development of protein chip technology

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

Science.gov (United States)

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

2017-11-01

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

Time-resolved spectroscopy of nonequilibrium ionization in laser-produced plasmas

International Nuclear Information System (INIS)

Marjoribanks, R.S.

1988-01-01

The highly transient ionization characteristic of laser-produced plasmas at high energy densities has been investigated experimentally, using x-ray spectroscopy with time resolution of less than 20 ps. Spectroscopic diagnostics of plasma density and temperature were used, including line ratios, line profile broadening and continuum emission, to characterize the plasma conditions without relying immediately on ionization modeling. The experimentally measured plasma parameters were used as independent variables, driving an ionization code, as a test of ionization modeling, divorced from hydrodynamic calculations. Several state-of-the-art streak spectrographs, each recording a fiducial of the laser peak along with the time-resolved spectrum, characterized the laser heating of thin signature layers of different atomic numbers imbedded in plastic targets. A novel design of crystal spectrograph, with a conically curved crystal, was developed. Coupled with a streak camera, it provided high resolution (λ/ΔΛ > 1000) and a collection efficiency roughly 20-50 times that of planar crystal spectrographs, affording improved spectra for quantitative reduction and greater sensitivity for the diagnosis of weak emitters. Experimental results were compared to hydrocode and ionization code simulations, with poor agreement. The conclusions question the appropriateness of describing electron velocity distributions by a temperature parameter during the time of laser illumination and emphasis the importance of characterizing the distribution more generally

A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry

Energy Technology Data Exchange (ETDEWEB)

Jozwiak, Chris M.; Graff, Jeff; Lebedev, Gennadi; Andresen, Nord; Schmid, Andreas; Fedorov, Alexei; El Gabaly, Farid; Wan, Weishi; Lanzara, Alessandra; Hussain, Zahid

2010-04-13

We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90 degrees bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.

Time-resolved photoelectron spectroscopy using synchrotron radiation time structure

International Nuclear Information System (INIS)

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

2011-01-01

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

Time Resolved Detection of Infrared Synchrotron Radiation at DAΦNE

International Nuclear Information System (INIS)

Bocci, A.; Marcelli, A.; Drago, A.; Guidi, M. Cestelli; Pace, E.; Piccinini, M.; Sali, D.; Morini, P.; Piotrowski, J.

2007-01-01

Synchrotron radiation is characterized by a very wide spectral emission from IR to X-ray wavelengths and a pulsed structure that is a function of the source time structure. In a storage ring, the typical temporal distance between two bunches, whose duration is a few hundreds of picoseconds, is on the nanosecond scale. Therefore, synchrotron radiation sources are a very powerful tools to perform time-resolved experiments that however need extremely fast detectors. Uncooled IR devices optimized for the mid-IR range with sub-nanosecond response time, are now available and can be used for fast detection of intense IR sources such as synchrotron radiation storage rings. We present here different measurements of the pulsed synchrotron radiation emission at DAΦNE (Double Annular Φ-factory for Nice Experiments), the collider of the Laboratori Nazionali of Frascati (LNF) of the Istituto Nazionale di Fisica Nucleare (INFN), performed with very fast uncooled infrared detectors with a time resolution of a few hundreds of picoseconds. We resolved the emission time structure of the electron bunches of the DAΦNE collider when it works in a normal condition for high energy physics experiments with both photovoltaic and photoconductive detectors. Such a technology should pave the way to new diagnostic methods in storage rings, monitoring also source instabilities and bunch dynamics

Insights into the charge carrier terahertz mobility in polyfluorenes from large-scale atomistic simulations and time-resolved terahertz spectroscopy

Czech Academy of Sciences Publication Activity Database

Vukmirović, N.; Ponseca, C.S.; Němec, Hynek; Yartsev, A.; Sundström, V.

2012-01-01

Roč. 116, č. 37 (2012), s. 19665-1972 ISSN 1932-7447 Institutional research plan: CEZ:AV0Z10100520 Keywords : charge carrier mobility * time-resolved terahertz spectroscopy * multiscale atomistic calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.814, year: 2012

Linearly Polarized IR Spectroscopy Theory and Applications for Structural Analysis

CERN Document Server

Kolev, Tsonko

2011-01-01

A technique that is useful in the study of pharmaceutical products and biological molecules, polarization IR spectroscopy has undergone continuous development since it first emerged almost 100 years ago. Capturing the state of the science as it exists today, "Linearly Polarized IR Spectroscopy: Theory and Applications for Structural Analysis" demonstrates how the technique can be properly utilized to obtain important information about the structure and spectral properties of oriented compounds. The book starts with the theoretical basis of linear-dichroic infrared (IR-LD) spectroscop

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

Czech Academy of Sciences Publication Activity Database

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

2017-01-01

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

Observation of a Slater-type metal-to-insulator transition in Sr$_2$IrO$_4$ from time-resolved photo-carrier dynamics

OpenAIRE

Hsieh, D.; Mahmood, F.; Torchinsky, D. H.; Cao, G.; Gedik, N.

2012-01-01

We perform a time-resolved optical study of Sr$_2$IrO$_4$ to understand the influence of magnetic ordering on the low energy electronic structure of a strongly spin-orbit coupled $J_{eff}$=1/2 Mott insulator. By studying the recovery dynamics of photo-carriers excited across the Mott gap, we find that upon cooling through the N\\'{e}el temperature $T_N$ the system evolves continuously from a metal-like phase with fast ($\\sim$50 fs) and excitation density independent relaxation dynamics to a ga...

Communication: IR spectroscopy of neutral transition metal clusters through thermionic emission

NARCIS (Netherlands)

Lapoutre, V. J. F.; Haertelt, M.; Meijer, G.; Fielicke, A.; Bakker, J. M.

2013-01-01

The resonant multiple photon excitation of neutral niobium clusters using tunable infrared (IR) radiation leads to thermionic emission. By measuring the mass-resolved ionization yield as a function of IR wavenumber species selective IR spectra are obtained for Nb-n (n = 5-20) over the 200-350 cm(-1)

Ultrafast stimulated Raman spectroscopy in the near-infrared region

International Nuclear Information System (INIS)

Takaya, Tomohisa

2016-01-01

A number of electronic transitions in the near-infrared wavelength region are associated with migration or delocalization of electrons in large molecules or molecular systems. Time-resolved near-infrared Raman spectroscopy will be a powerful tool for investigating the structural dynamic of samples with delocalized electrons. However, the sensitivity of near-infrared spontaneous Raman spectrometers is significantly low due to an extremely small probability of Raman scattering and a low sensitivity of near-infrared detectors. Nonlinear Raman spectroscopy is one of the techniques that can overcome the sensitivity problems and enable us to obtain time-resolved Raman spectra in resonance with near-IR transitions. In this article, the author introduces recent progress of ultrafast time-resolved near-infrared stimulated Raman spectroscopy. Optical setup, spectral and temporal resolution, and applications of the spectrometer are described. (author)

Rapid high-resolution spin- and angle-resolved photoemission spectroscopy with pulsed laser source and time-of-flight spectrometer

Science.gov (United States)

Gotlieb, K.; Hussain, Z.; Bostwick, A.; Lanzara, A.; Jozwiak, C.

2013-09-01

A high-efficiency spin- and angle-resolved photoemission spectroscopy (spin-ARPES) spectrometer is coupled with a laboratory-based laser for rapid high-resolution measurements. The spectrometer combines time-of-flight (TOF) energy measurements with low-energy exchange scattering spin polarimetry for high detection efficiencies. Samples are irradiated with fourth harmonic photons generated from a cavity-dumped Ti:sapphire laser that provides high photon flux in a narrow bandwidth, with a pulse timing structure ideally matched to the needs of the TOF spectrometer. The overall efficiency of the combined system results in near-EF spin-resolved ARPES measurements with an unprecedented combination of energy resolution and acquisition speed. This allows high-resolution spin measurements with a large number of data points spanning multiple dimensions of interest (energy, momentum, photon polarization, etc.) and thus enables experiments not otherwise possible. The system is demonstrated with spin-resolved energy and momentum mapping of the L-gap Au(111) surface states, a prototypical Rashba system. The successful integration of the spectrometer with the pulsed laser system demonstrates its potential for simultaneous spin- and time-resolved ARPES with pump-probe based measurements.

Time-resolved photoelectron spectrometry of a dephasing process in pyrazine

International Nuclear Information System (INIS)

Pavlov, R.L.; Pavlov, L.I.; Delchev, Ya.I.; Pavlova, S.I.

2001-01-01

The first femtosecond time-resolved photoelectron imaging (PEI) is presented. The method is characterized by photoionization of NO and further applied to ultrafast dephasing in pyrazine. Intermediate case behaviour in radiationless transition is clearly observed in time-resolved photoelectron kinetic energy distribution. Femtosecond PEI is with much improved efficiency than conventional photoelectron spectroscopies. It is anticipated that the unifield approach of time-resolved photoelectron and photoion imaging opens the possibility of observing photon-induced dynamics in real time

Bond Shortening (1.4 Å) in the Singlet and Triplet Excited States of [Ir2(dimen)4]2+ in Solution Determined by Time-Resolved X-ray Scattering

DEFF Research Database (Denmark)

Haldrup, Martin Kristoffer; Harlang, Tobias; Christensen, Morten

2011-01-01

Ground- and excited-state structures of the bimetallic, ligand-bridged compound Ir2(dimen)42+ are investigated in acetonitrile by means of time-resolved X-ray scattering. Following excitation by 2 ps laser pulses at 390 nm, analysis of difference scattering patterns obtained at eight different ti...

Noninvasive observation of skeletal muscle contraction using near-infrared time-resolved reflectance and diffusing-wave spectroscopy

Science.gov (United States)

Belau, Markus; Ninck, Markus; Hering, Gernot; Spinelli, Lorenzo; Contini, Davide; Torricelli, Alessandro; Gisler, Thomas

2010-09-01

We introduce a method for noninvasively measuring muscle contraction in vivo, based on near-infrared diffusing-wave spectroscopy (DWS). The method exploits the information about time-dependent shear motions within the contracting muscle that are contained in the temporal autocorrelation function g(1)(τ,t) of the multiply scattered light field measured as a function of lag time, τ, and time after stimulus, t. The analysis of g(1)(τ,t) measured on the human M. biceps brachii during repetitive electrical stimulation, using optical properties measured with time-resolved reflectance spectroscopy, shows that the tissue dynamics giving rise to the speckle fluctuations can be described by a combination of diffusion and shearing. The evolution of the tissue Cauchy strain e(t) shows a strong correlation with the force, indicating that a significant part of the shear observed with DWS is due to muscle contraction. The evolution of the DWS decay time shows quantitative differences between the M. biceps brachii and the M. gastrocnemius, suggesting that DWS allows to discriminate contraction of fast- and slow-twitch muscle fibers.

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

NARCIS (Netherlands)

Mesu, J. Gerbrand; Beale, Andrew M.; de Groot, Frank M. F.; Weckhuysen, Bert M.

2006-01-01

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

Mid IR-fiber spectroscopy in the 2-17μm range

Science.gov (United States)

Artyushenko, Viatcheslav G.; Bocharnikov, A.; Colquhoun, Gary; Leach, Clive A.; Lobachov, Vladimir; Pirogova, Lyudmila; Sakharova, Tatjana; Savitskij, Dmitrij; Ezhevskaya, Tatjana; Bublikov, Alexandr

2007-10-01

The latest development in IR-fibre optics enables us to expand the spectral range of process spectroscopy from 2μm out to 17μm (5000 to 600cm-1) i.e. into the most informative "finger-print" part of the spectrum. Mid-IR wavelength ranges from 2 to 6-10μm may be covered by Chalcogenide IR-glass CIR-fibres while Polycrystalline PIR-fibres made of Silver Halides solid solutions transmit 4-17 μm wavelength radiation. PIR-fibre immersion ATR probes and Transmission/Reflection probes had been manufactured and successfully tested with different FTIR spectrometers in the field of remote spectroscopy for forensic substances identification, chemical reaction control, and monitoring of exhaust or exhalation gases. Using these techniques no sample preparation is necessary for fibre probes to measure evanescent, reflection and transmission spectra, in situ and in real time. QCL spectrometer may be used as a portable device for multispectral gas analysis at 1ppb level of detectivity for various applications in environmental pollution monitoring.

Study of the Bulk Charge Carrier Dynamics in Anatase and Rutile TiO2 Single Crystals by Femtosecond Time Resolved Spectroscopy

KAUST Repository

Maity, Partha; Mohammed, Omar F.; Katsiev, Khabiboulakh; Idriss, Hicham

2018-01-01

as the best model for fundamental studies. Their ultrafast charge carrier dynamics especially on TiO2 anatase single crystal (the most active phase) are unresolved. Here femtosecond time resolved spectroscopy (TRS) was carried out to explore the dynamics

Distortion dependent intersystem crossing: A femtosecond time-resolved photoelectron spectroscopy study of benzene, toluene, and p-xylene

Directory of Open Access Journals (Sweden)

Anne B. Stephansen

2017-07-01

Full Text Available The competition between ultrafast intersystem crossing and internal conversion in benzene, toluene, and p-xylene is investigated with time-resolved photoelectron spectroscopy and quantum chemical calculations. By exciting to S2 out-of-plane symmetry breaking, distortions are activated at early times whereupon spin-forbidden intersystem crossing becomes (partly allowed. Natural bond orbital analysis suggests that the pinnacle carbon atoms distorting from the aromatic plane change hybridization between the planar Franck-Condon geometry and the deformed (boat-shaped S2 equilibrium geometry. The effect is observed to increase in the presence of methyl-groups on the pinnacle carbon-atoms, where largest extents of σ and π orbital-mixing are observed. This is fully consistent with the time-resolved spectroscopy data: Toluene and p-xylene show evidence for ultrafast triplet formation competing with internal conversion, while benzene appears to only decay via internal conversion within the singlet manifold. For toluene and p-xylene, internal conversion to S1 and intersystem crossing to T3 occur within the time-resolution of our instrument. The receiver triplet state (T3 is found to undergo internal conversion in the triplet manifold within ≈100–150 fs (toluene or ≈180–200 fs (p-xylene as demonstrated by matching rise and decay components of upper and lower triplet states. Overall, the effect of methylation is found to both increase the intersystem crossing probability and direct the molecular axis of the excited state dynamics.

Chemical profiling and adulteration screening of Aquilariae Lignum Resinatum by Fourier transform infrared (FT-IR) spectroscopy and two-dimensional correlation infrared (2D-IR) spectroscopy

Science.gov (United States)

Qu, Lei; Chen, Jian-bo; Zhang, Gui-Jun; Sun, Su-qin; Zheng, Jing

2017-03-01

As a kind of expensive perfume and valuable herb, Aquilariae Lignum Resinatum (ALR) is often adulterated for economic motivations. In this research, Fourier transform infrared (FT-IR) spectroscopy is employed to establish a simple and quick method for the adulteration screening of ALR. First, the principal chemical constituents of ALR are characterized by FT-IR spectroscopy at room temperature and two-dimensional correlation infrared (2D-IR) spectroscopy with thermal perturbation. Besides the common cellulose and lignin compounds, a certain amount of resin is the characteristic constituent of ALR. Synchronous and asynchronous 2D-IR spectra indicate that the resin (an unstable secondary metabolite) is more sensitive than cellulose and lignin (stable structural constituents) to the thermal perturbation. Using a certified ALR sample as the reference, the infrared spectral correlation threshold is determined by 30 authentic samples and 6 adulterated samples. The spectral correlation coefficient of an authentic ALR sample to the standard reference should be not less than 0.9886 (p = 0.01). Three commercial adulterated ALR samples are identified by the correlation threshold. Further interpretation of the infrared spectra of the adulterated samples indicates the common adulterating methods - counterfeiting with other kind of wood, adding ingredient such as sand to increase the weight, and adding the cheap resin such as rosin to increase the content of resin compounds. Results of this research prove that FT-IR spectroscopy can be used as a simple and accurate quality control method of ALR.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-04-15

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

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.

Ultrafast optical responses of β-carotene and lycopene probed by sub-20-fs time-resolved coherent spectroscopy

International Nuclear Information System (INIS)

Fujiwara, M.; Sugisaki, M.; Gall, A.; Robert, B.; Cogdell, R.J.; Hashimoto, H.

2009-01-01

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 β-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 β-ionone ring and polyene backbone, whereas the other high-frequency modes do not show such dependency on the structural distortions.

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.

Time- and Space-Resolved Spectroscopic Investigation on Pi-Conjugated Nanostructures - 2

Science.gov (United States)

2016-01-12

Defocused wide-field fluorescence (DWFI) microscopy suggests that molecular heterogeneities and flexibilities clearly depend on ring size and that site... Confocal   Microscopy   Setup Wild‐field  Microscopy   Setup Femtosecond Z‐scan  experiment Setup Figure 3. Instruments of Time- and space-resolved...approved for public release. 3. Space-Resolved Laser Spectroscopy - Confocal Microscopy - Wild-field Microscopy 4. Non-Linear Spectroscopy

Anisotropy in Bone Demineralization Revealed by Polarized Far-IR Spectroscopy

Directory of Open Access Journals (Sweden)

Roman Schuetz

2015-04-01

Full Text Available Bone material is composed of an organic matrix of collagen fibers and apatite nanoparticles. Previously, vibrational spectroscopy techniques such as infrared (IR and Raman spectroscopy have proved to be particularly useful for characterizing the two constituent organic and inorganic phases of bone. In this work, we tested the potential use of high intensity synchrotron-based far-IR radiation (50–500 cm−1 to gain new insights into structure and chemical composition of bovine fibrolamellar bone. The results from our study can be summarized in the following four points: (I compared to far-IR spectra obtained from synthetic hydroxyapatite powder, those from fibrolamellar bone showed similar peak positions, but very different peak widths; (II during stepwise demineralization of the bone samples, there was no significant change neither to far-IR peak width nor position, demonstrating that mineral dissolution occurred in a uniform manner; (III application of external loading on fully demineralized bone had no significant effect on the obtained spectra, while dehydration of samples resulted in clear differences. (IV using linear dichroism, we showed that the anisotropic structure of fibrolamellar bone is also reflected in anisotropic far-IR absorbance properties of both the organic and inorganic phases. Far-IR spectroscopy thus provides a novel way to functionally characterize bone structure and chemistry, and with further technological improvements, has the potential to become a useful clinical diagnostic tool to better assess quality of collagen-based tissues.

Chemical profiling and adulteration screening of Aquilariae Lignum Resinatum by Fourier transform infrared (FT-IR) spectroscopy and two-dimensional correlation infrared (2D-IR) spectroscopy.

Science.gov (United States)

Qu, Lei; Chen, Jian-Bo; Zhang, Gui-Jun; Sun, Su-Qin; Zheng, Jing

2017-03-05

As a kind of expensive perfume and valuable herb, Aquilariae Lignum Resinatum (ALR) is often adulterated for economic motivations. In this research, Fourier transform infrared (FT-IR) spectroscopy is employed to establish a simple and quick method for the adulteration screening of ALR. First, the principal chemical constituents of ALR are characterized by FT-IR spectroscopy at room temperature and two-dimensional correlation infrared (2D-IR) spectroscopy with thermal perturbation. Besides the common cellulose and lignin compounds, a certain amount of resin is the characteristic constituent of ALR. Synchronous and asynchronous 2D-IR spectra indicate that the resin (an unstable secondary metabolite) is more sensitive than cellulose and lignin (stable structural constituents) to the thermal perturbation. Using a certified ALR sample as the reference, the infrared spectral correlation threshold is determined by 30 authentic samples and 6 adulterated samples. The spectral correlation coefficient of an authentic ALR sample to the standard reference should be not less than 0.9886 (p=0.01). Three commercial adulterated ALR samples are identified by the correlation threshold. Further interpretation of the infrared spectra of the adulterated samples indicates the common adulterating methods - counterfeiting with other kind of wood, adding ingredient such as sand to increase the weight, and adding the cheap resin such as rosin to increase the content of resin compounds. Results of this research prove that FT-IR spectroscopy can be used as a simple and accurate quality control method of ALR. Copyright © 2016 Elsevier B.V. All rights reserved.

Study on Angelica and its different extracts by Fourier transform infrared spectroscopy and two-dimensional correlation IR spectroscopy

Science.gov (United States)

Liu, Hong-xia; Sun, Su-qin; Lv, Guang-hua; Chan, Kelvin K. C.

2006-05-01

In order to develop a rapid and effective analysis method for studying integrally the main constituents in the medicinal materials and their extracts, discriminating the extracts from different extraction process, comparing the categories of chemical constituents in the different extracts and monitoring the qualities of medicinal materials, we applied Fourier transform infrared spectroscopy (FT-IR) associated with second derivative infrared spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR) to study the main constituents in traditional Chinese medicine Angelica and its different extracts (extracted by petroleum ether, ethanol and water in turn). The findings indicated that FT-IR spectrum can provide many holistic variation rules of chemical constituents. Use of the macroscopical fingerprint characters of FT-IR and 2D-IR spectrum can not only identify the main chemical constituents in medicinal materials and their different extracts, but also compare the components differences among the similar samples. This analytical method is highly rapid, effective, visual and accurate for pharmaceutical research.

Femtosecond time-resolved transient absorption spectroscopy of xanthophylls.

Science.gov (United States)

Niedzwiedzki, Dariusz M; Sullivan, James O; Polívka, Tomás; Birge, Robert R; Frank, Harry A

2006-11-16

Xanthophylls are a major class of photosynthetic pigments that participate in an adaptation mechanism by which higher plants protect themselves from high light stress. In the present work, an ultrafast time-resolved spectroscopic investigation of all the major xanthophyll pigments from spinach has been performed. The molecules are zeaxanthin, lutein, violaxanthin, and neoxanthin. beta-Carotene was also studied. The experimental data reveal the inherent spectral properties and ultrafast dynamics including the S(1) state lifetimes of each of the pigments. In conjunction with quantum mechanical computations the results address the molecular features of xanthophylls that control the formation and decay of the S* state in solution. The findings provide compelling evidence that S* is an excited state with a conformational geometry twisted relative to the ground state. The data indicate that S* is formed via a branched pathway from higher excited singlet states and that its yield depends critically on the presence of beta-ionylidene rings in the polyene system of pi-electron conjugated double bonds. The data are expected to be beneficial to researchers employing ultrafast time-resolved spectroscopic methods to investigate the mechanisms of both energy transfer and nonphotochemical quenching in higher plant preparations.

Quantitative analysis of time-resolved infrared stimulated luminescence in feldspars

DEFF Research Database (Denmark)

Pagonis, Vasilis; Ankjærgaard, Christina; Jain, Mayank

2016-01-01

Time-resolved infrared-stimulated luminescence (TR-IRSL) from feldspar samples is of importance in the field of luminescence dating, since it provides information on the luminescence mechanism in these materials. In this paper we present new analytical equations which can be used to analyze TR-IR...

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-28

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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.

Development of wide-band, time and energy resolving, optical photon detectors with application to imaging astronomy

International Nuclear Information System (INIS)

Miller, A.J.; Cabrera, B.; Romani, R.W.; Figueroa-Feliciano, E.; Nam, S.W.; Clarke, R.M.

2000-01-01

Superconducting transition edge sensors (TESs) are showing promise for the wide-band spectroscopy of individual photons from the mid-infrared (IR), through the optical, and into the near ultraviolet (UV). Our TES sensors are ∼20 μm square, 40 nm thick tungsten (W) films with a transition temperature of about 80 mK. We typically attain an energy resolution of 0.15 eV FWHM over the optical range with relative timing resolution of 100 ns. Single photon events with sub-microsecond risetimes and few microsecond falltimes have been achieved allowing count rates in excess of 30 kHz per pixel. Additionally, tungsten is approximately 50% absorptive in the optical (dropping to 10% in the IR) giving these devices an intrinsically high quantum efficiency. These combined traits make our detectors attractive for fast spectrophotometers and photon-starved applications such as wide-band, time and energy resolved astronomical observations. We present recent results from our work toward the fabrication and testing of the first TES optical photon imaging arrays

Isotope effect on hydrated electron relaxation dynamics studied with time-resolved liquid jet photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Elkins, Madeline H.; Williams, Holly L. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Neumark, Daniel M., E-mail: dneumark@berkeley.edu [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2016-05-14

The excited state relaxation dynamics of the solvated electron in H{sub 2}O and D{sub 2}O are investigated using time-resolved photoelectron spectroscopy in a liquid microjet. The data show that the initial excited state decays on a time scale of 75 ± 12 fs in H{sub 2}O and 102 ± 8 fs in D{sub 2}O, followed by slower relaxation on time scales of 400 ± 70 fs and 390 ± 70 fs that are isotopically invariant within the precision of our measurements. Based on the time evolution of the transient signals, the faster and slower time constants are assigned to p → s internal conversion (IC) of the hydrated electron and relaxation on the ground electronic state, respectively. This assignment is consistent with the non-adiabatic mechanism for relaxation of the hydrated electron and yields an isotope effect of 1.4 ± 0.2 for IC of the hydrated electron.

Isotope effect on hydrated electron relaxation dynamics studied with time-resolved liquid jet photoelectron spectroscopy

Science.gov (United States)

Elkins, Madeline H.; Williams, Holly L.; Neumark, Daniel M.

2016-05-01

The excited state relaxation dynamics of the solvated electron in H2O and D2O are investigated using time-resolved photoelectron spectroscopy in a liquid microjet. The data show that the initial excited state decays on a time scale of 75 ± 12 fs in H2O and 102 ± 8 fs in D2O, followed by slower relaxation on time scales of 400 ± 70 fs and 390 ± 70 fs that are isotopically invariant within the precision of our measurements. Based on the time evolution of the transient signals, the faster and slower time constants are assigned to p → s internal conversion (IC) of the hydrated electron and relaxation on the ground electronic state, respectively. This assignment is consistent with the non-adiabatic mechanism for relaxation of the hydrated electron and yields an isotope effect of 1.4 ± 0.2 for IC of the hydrated electron.

Impulsive IR-multiphoton dissociation of acrolein: observation of non-statistical product vibrational excitation in CO ( v=1-12) by time resolved IR fluorescence spectroscopy

Science.gov (United States)

Chowdhury, P. K.

2000-10-01

On IR-multiphoton excitation, vibrationally highly excited acrolein molecules undergo concerted dissociation generating CO and ethylene. The vibrationally excited products, CO and ethylene, are detected immediately following the CO 2 laser pulse by observing IR fluorescence at 4.7 and 3.2 μm, respectively. The nascent CO is formed with significant vibrational excitation, with a Boltzmann population distribution for v=1-12 levels corresponding to T v=12 950±50 K. The average vibrational energy in the product CO is found to be 26 kcal mol -1, in contrast to its statistical share of 5 kcal mol -1, available from the product energy distribution. The nascent vibrationally excited ethylene either dissociates by absorbing further infrared laser photons from the tail of the CO 2 laser pulse or relaxes by collisional deactivation. Ethylene IR-fluorescence excitation spectrum showed a structure in the quasi-continuum, with a facile resonance at 10.53 μm corresponding to the 10P(14) CO 2 laser line, which explains the higher acetylene yield observed at a higher pressure. A hydrogen atom transfer mechanism followed by C-C impulsive break in the acrolein transition state may be responsible for such non-statistical product energy distribution.

Direct angle resolved photoemission spectroscopy and ...

Indian Academy of Sciences (India)

Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (< 30 nm) cuprate films. Specifically, we probe low-energy electronic structure and properties of high-c superconductors (HTSC) under different degrees of epitaxial (compressive vs. tensile) strain.

Time resolved measurement of laser-ablated particles by LAPXAS (Laser Plasma Soft X-ray Absorption Spectroscopy)

International Nuclear Information System (INIS)

Miyashita, Atsumi; Yoda, Osamu; Murakami, Kouichi

1999-01-01

The time- and spatially-resolved properties of laser ablated carbon, boron and silicon particles were measured by LAPXAS (Laser Plasma Soft X-ray Absorption Spectroscopy). The maximum speed of positively charged ions is higher than those of neutral atoms and negatively charged ions. The spatial distributions of the laser-ablated particles in the localized rare gas environment were measured. In helium gas environment, by the helium cloud generated on the top of ablation plume depressed the ablation plume. There is no formation of silicon clusters till 15 μs after laser ablation in the argon gas environment. (author)

Assessment of Azithromycin in Pharmaceutical Formulation by Fourier-transform Infrared (FT-IR Transmission Spectroscopy

Directory of Open Access Journals (Sweden)

Muhammad Ali Mallah

2011-12-01

Full Text Available A simple, rapid and economical method for azithromycin quantification in solid tablet and capsule formulations has been developed by applying Fourier-transform Infrared (FT-IR transmission spectroscopy for regular quality monitoring. The newly developed method avoids the sample preparation, except grinding for pellet formation and does not involve consumption of any solvent as it absolutely eliminates the need of extraction. KBr pellets were employed for the appraisal of azithromycin while acquiring spectra of standards as well as samples on FT-IR. By selecting the FT-IR carbonyl band (C=O in the region 1,744–1,709 cm−1 the calibration model was developed based on simple Beer’s law. The excellent regression coefficient (R2 0.999 was accomplished for calibration set having standard error of calibration equal to 0.01 mg. The current work exposes that transmission FT-IR spectroscopy can definitely be applied to determine the exact amount of azithromycin to control the processing and quality of solid formulations with reduced cost and short analysis time.

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.

Creation of free excitons in solid krypton investigated by time-resolved luminescence spectroscopy

International Nuclear Information System (INIS)

Kisand, Vambola; Kirm, Marco; Negodin, Evgeni; Sombrowski, Elke; Steeg, Barbara; Vielhauer, Sebastian; Zimmerer, Georg

2003-01-01

The creation and relaxation of secondary excitons in solid Kr was investigated using energy-and time-resolved luminescence spectroscopy in the vacuum ultraviolet region. The spectrally selected emission of the free exciton (FE) was used as a probe for an investigation of the different exciton creation processes. Delayed FE creation via electron-hole recombination and 'prompt' (in terms of the time-resolution of the experiment) creation of excitons were separated. The 'prompt' creation of a FE appears in the region above threshold energy E th , which is equal to the sum of the band gap energy and the free exciton energy. 'Prompt' creation of excitons above E th is ascribed to a superposition of two processes: (i) creation of the electronic polaron complex (one-step process) and (ii) inelastic scattering of photoelectrons described in the framework of the multiple-parabolic-branch band model (two-step process). In addition, the ratio spectrum of the time-integrated FE and self-trapped exciton (STE) emission was analysed. The behaviour of the ratio spectrum is a proof that electron-hole recombination leads to STE states through FE states as precursors

Time-resolved tunable diode laser absorption spectroscopy of excited argon and ground-state titanium atoms in pulsed magnetron discharges

Czech Academy of Sciences Publication Activity Database

Sushkov, V.; Do, H.T.; Čada, Martin; Hubička, Zdeněk; Hippler, R.

2013-01-01

Roč. 22, č. 1 (2013), 1-10 ISSN 0963-0252 R&D Projects: GA ČR(CZ) GAP205/11/0386; GA ČR GAP108/12/2104 Institutional research plan: CEZ:AV0Z10100522 Keywords : absorption spectroscopy * diode laser * magnetron * argon metastable * HiPIMS * titanium * time-resolved Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.056, year: 2013 http://iopscience.iop.org/0963-0252/22/1/015002/

Dynamics of Al/Fe{sub 2}O{sub 3} MIC combustion from short single-pulse photothermal initiation and time-resolved spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Stiegman, Albert E.; Park, Chi-Dong; Mileham, Melissa; Van de Burgt, Lambertus J. [Department of Chemistry and Biochemistry, Florida State University Tallahassee, FL (United States); Kramer, Michael P. [AFRL/MNME Eglin AFB, FL (United States)

2009-08-15

Time-resolved spectroscopy was used to study the dynamics of the photothermal ignition of Al/Fe{sub 2}O{sub 3} metastable intermolecular composites after single short-pulse laser initiation. The dynamics were recorded in several time domains from nanosecond to microsecond to quantify the dynamics from initial laser excitation to combustion. Time-averaged spectral data were also collected for the overall emission occurring during combustion. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

Isolated Gramicidin Peptides Probed by IR Spectroscopy

Czech Academy of Sciences Publication Activity Database

Rijs, A. M.; Kabeláč, Martin; Abo-Riziq, A.; Hobza, Pavel; de Vries, M. S.

2011-01-01

Roč. 12, č. 10 (2011), s. 1816-1821 ISSN 1439-4235 R&D Projects: GA MŠk LC512; GA AV ČR IAA400550808 Institutional research plan: CEZ:AV0Z40550506 Keywords : density functional calculations * gramicidin * IR spectroscopy * protein folding Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.412, year: 2011

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

Science.gov (United States)

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

2017-10-01

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

SmB6 electron-phonon coupling constant from time- and angle-resolved photoelectron spectroscopy

Science.gov (United States)

Sterzi, A.; Crepaldi, A.; Cilento, F.; Manzoni, G.; Frantzeskakis, E.; Zacchigna, M.; van Heumen, E.; Huang, Y. K.; Golden, M. S.; Parmigiani, F.

2016-08-01

SmB6 is a mixed valence Kondo system resulting from the hybridization between localized f electrons and delocalized d electrons. We have investigated its out-of-equilibrium electron dynamics by means of time- and angle-resolved photoelectron spectroscopy. The transient electronic population above the Fermi level can be described by a time-dependent Fermi-Dirac distribution. By solving a two-temperature model that well reproduces the relaxation dynamics of the effective electronic temperature, we estimate the electron-phonon coupling constant λ to range from 0.13 ±0.03 to 0.04 ±0.01 . These extremes are obtained assuming a coupling of the electrons with either a phonon mode at 10 or 19 meV. A realistic value of the average phonon energy will give an actual value of λ within this range. Our results provide an experimental report on the material electron-phonon coupling, contributing to both the electronic transport and the macroscopic thermodynamic properties of SmB6.

Magnetometry of buried layers—Linear magnetic dichroism and spin detection in angular resolved hard X-ray photoelectron spectroscopy

International Nuclear Information System (INIS)

Gloskovskii, Andrei; Stryganyuk, Gregory; Fecher, Gerhard H.; Felser, Claudia; Thiess, Sebastian; Schulz-Ritter, Heiko; Drube, Wolfgang; Berner, Götz; Sing, Michael; Claessen, Ralph; Yamamoto, Masafumi

2012-01-01

Highlights: ► Newly commissioned HAXPES instrument at P09 beamline of the PETRA III ring at DESY. ► We report HAXPES studies on buried magnetic nanolayers in a multi-layer sample. ► Linear magnetic dichroism of photoelectrons from buried CoFe–Ir 78 Mn 22 layers. ► Spin-resolved HAXPES measurements on buried magnetic multilayers using Mott detector. - Abstract: The electronic properties of buried magnetic nano-layers were studied using the linear magnetic dichroism in the angular distribution of photoemitted Fe, Co, and Mn 2p electrons from a CoFe–Ir 78 Mn 22 multi-layered sample. The buried layers were probed using hard X-ray photoelectron spectroscopy, HAXPES, at the undulator beamline P09 of the 3rd generation storage ring PETRA III. The results demonstrate that this magnetometry technique can be used as a sensitive element specific probe for magnetic properties suitable for application to buried ferromagnetic and antiferromagnetic magnetic materials and multilayered spintronics devices. Using the same instrument, spin-resolved Fe 2p HAXPES spectra were obtained from the buried layer with good signal quality.

Time resolved infrared spectroscopy of femtosecond proton dynamics in the liquid phase

International Nuclear Information System (INIS)

Amir, W.

2003-12-01

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 2 O for reasons of experimental and theoretical suitability. However this is not water. Pure water H 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)

Coherent spectroscopies on ultrashort time and length scales

Directory of Open Access Journals (Sweden)

Schneider C.

2013-03-01

Full Text Available Three spectroscopic techniques are presented that provide simultaneous spatial and temporal resolution: modified confocal microscopy with heterodyne detection, space-time-resolved spectroscopy using coherent control concepts, and coherent two-dimensional nano-spectroscopy. Latest experimental results are discussed.

Time- and angle-resolved photoemission spectroscopy with optimized high-harmonic pulses using frequency-doubled Ti:Sapphire lasers

International Nuclear Information System (INIS)

Eich, S.; Stange, A.; Carr, A.V.; Urbancic, J.; Popmintchev, T.; Wiesenmayer, M.; Jansen, K.; Ruffing, A.; Jakobs, S.; Rohwer, T.; Hellmann, S.; Chen, C.; Matyba, P.; Kipp, L.; Rossnagel, K.; Bauer, M.; Murnane, M.M.; Kapteyn, H.C.; Mathias, S.; Aeschlimann, M.

2014-01-01

Highlights: • We present a scheme to generate high intensity XUV pulses from HHG with variable time-bandwidth product. • Shorter-wavelength driven high-harmonic XUV trARPES provides higher photon flux and increased energy resolution. • High-quality high-harmonic XUV trARPES data with sub 150 meV energy and sub 30 fs time resolution is presented. - Abstract: Time- and angle-resolved photoemission spectroscopy (trARPES) using femtosecond extreme ultraviolet high harmonics has recently emerged as a powerful tool for investigating ultrafast quasiparticle dynamics in correlated-electron materials. However, the full potential of this approach has not yet been achieved because, to date, high harmonics generated by 800 nm wavelength Ti:Sapphire lasers required a trade-off between photon flux, energy and time resolution. Photoemission spectroscopy requires a quasi-monochromatic output, but dispersive optical elements that select a single harmonic can significantly reduce the photon flux and time resolution. Here we show that 400 nm driven high harmonic extreme-ultraviolet trARPES is superior to using 800 nm laser drivers since it eliminates the need for any spectral selection, thereby increasing photon flux and energy resolution to <150 meV while preserving excellent time resolution of about 30 fs

Photodissociation Spectroscopy of Cold Protonated Synephrine: Surprising Differences between IR-UV Hole-Burning and IR Photodissociation Spectroscopy of the O-H and N-H Modes.

Science.gov (United States)

Nieuwjaer, N; Desfrançois, C; Lecomte, F; Manil, B; Soorkia, S; Broquier, M; Grégoire, G

2018-04-19

We report the UV and IR photofragmentation spectroscopies of protonated synephrine in a cryogenically cooled Paul trap. Single (UV or IR) and double (UV-UV and IR-UV) resonance spectroscopies have been performed and compared to quantum chemistry calculations, allowing the assignment of the lowest-energy conformer with two rotamers depending on the orientation of the phenol hydroxyl (OH) group. The IR-UV hole burning spectrum exhibits the four expected vibrational modes in the 3 μm region, i.e., the phenol OH, C β -OH, and two NH 2 + stretches. The striking difference is that, among these modes, only the free phenol OH mode is active through IRPD. The protonated amino group acts as a proton donor in the internal hydrogen bond and displays large frequency shifts upon isomerization expected during the multiphoton absorption process, leading to the so-called IRMPD transparency. More interestingly, while the C β -OH is a proton acceptor group with moderate frequency shift for the different conformations, this mode is still inactive through IRPD.

Determination of quenching coefficients by time resolved emission spectroscopy

International Nuclear Information System (INIS)

Gans, T.; Schulz-von der Gathen, V.; Doebele, H.F.

2001-01-01

Capacitively coupled RF discharges (CCRF discharges) at 13.56 MHz in hydrogen exhibit a field reversal phase of about 10 ns during which an intense electron current provides collisional excitation, within the sheath region. After this strongly dominant short pulsed electron impact excitation, it is possible to determine quenching coefficients from the lifetime of the fluorescence at various pressures by time resolved OES even for high energy levels and without any restrictions of optical selection rules. This novel technique allows the measurement of quenching coefficients for atomic and molecular emission lines of hydrogen itself, as well as for emission lines of small admixtures (e.g. noble gases) to the hydrogen discharge, since with a fast gate-able ICCD camera operating at 13.56 MHz it is possible to measure even faint emission lines temporally resolved

Determination of quenching coefficients by time resolved emission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Gans, T.; Schulz-von der Gathen, V.; Doebele, H.F. [Essen Univ. (Gesamthochschule) (Germany). Inst. fuer Laser- und Plasmaphysik

2001-07-01

Capacitively coupled RF discharges (CCRF discharges) at 13.56 MHz in hydrogen exhibit a field reversal phase of about 10 ns during which an intense electron current provides collisional excitation, within the sheath region. After this strongly dominant short pulsed electron impact excitation, it is possible to determine quenching coefficients from the lifetime of the fluorescence at various pressures by time resolved OES even for high energy levels and without any restrictions of optical selection rules. This novel technique allows the measurement of quenching coefficients for atomic and molecular emission lines of hydrogen itself, as well as for emission lines of small admixtures (e.g. noble gases) to the hydrogen discharge, since with a fast gate-able ICCD camera operating at 13.56 MHz it is possible to measure even faint emission lines temporally resolved.

Nanomechanical IR spectroscopy for fast analysis of liquid-dispersed engineered nanomaterials

DEFF Research Database (Denmark)

Andersen, Alina Joukainen; Yamada, Shoko; Ek, Pramod Kumar

2016-01-01

The proliferated use of engineered nanomaterials (ENMs), e.g. in nanomedicine, calls for novel techniques allowing for fast and sensitive analysis of minute samples. Here we present nanomechanical IR spectroscopy (NAM-IR) for chemical analysis of picograms of ENMs. ENMs are nebulized directly from...

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Cahoon, James Francis [Univ. of California, Berkeley, CA (United States)

2008-12-01

One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO)₃ and CpFe(CO)₂ have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO)₅[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO)₅ have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.

Highly Resolved Sub-Terahertz Vibrational Spectroscopy of Biological Macromolecules and Bacteria Cells

Science.gov (United States)

2016-07-01

HIGHLY RESOLVED SUB-TERAHERTZ VIBRATIONAL SPECTROSCOPY OF BIOLOGICAL MACROMOLECULES AND BACTERIA CELLS ECBC...SUBTITLE Highly Resolved Sub-Terahertz Vibrational Spectroscopy of Biological Macromolecules and Bacteria Cells 5a. CONTRACT NUMBER W911SR-14-P...22 4.3 Bacteria THz Study

Resolving molecular vibronic structure using high-sensitivity two-dimensional electronic spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Bizimana, Laurie A.; Brazard, Johanna; Carbery, William P.; Gellen, Tobias; Turner, Daniel B., E-mail: dturner@nyu.edu [Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003 (United States)

2015-10-28

Coherent multidimensional optical spectroscopy is an emerging technique for resolving structure and ultrafast dynamics of molecules, proteins, semiconductors, and other materials. A current challenge is the quality of kinetics that are examined as a function of waiting time. Inspired by noise-suppression methods of transient absorption, here we incorporate shot-by-shot acquisitions and balanced detection into coherent multidimensional optical spectroscopy. We demonstrate that implementing noise-suppression methods in two-dimensional electronic spectroscopy not only improves the quality of features in individual spectra but also increases the sensitivity to ultrafast time-dependent changes in the spectral features. Measurements on cresyl violet perchlorate are consistent with the vibronic pattern predicted by theoretical models of a highly displaced harmonic oscillator. The noise-suppression methods should benefit research into coherent electronic dynamics, and they can be adapted to multidimensional spectroscopies across the infrared and ultraviolet frequency ranges.

Detecting aromatic compounds on planetary surfaces using ultraviolet time-resolved fluorescence spectroscopy

Science.gov (United States)

Eshelman, E.; Daly, M. G.; Slater, G.; Cloutis, E.

2018-02-01

Many aromatic organic molecules exhibit strong and characteristic fluorescence when excited with ultraviolet radiation. As laser excitation in the ultraviolet generates both fluorescence and resonantly enhanced Raman scattering of aromatic vibrational modes, combined Raman and fluorescence instruments have been proposed to search for organic compounds on Mars. In this work the time-resolved fluorescence of a suite of 24 compounds composed of 2-5 ringed alternant, non-alternant, and heterocyclic PAHs was measured. Fluorescence instrumentation with similar specifications to a putative flight instrument was capable of observing the fluorescence decay of these compounds with a sub-ns resolution. Incorporating time-resolved capabilities was also found to increase the ability to discriminate between individual PAHs. Incorporating time-resolved fluorescence capabilities into an ultraviolet gated Raman system intended for a rover or lander can increase the ability to detect and characterize PAHs on planetary surfaces.

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

Science.gov (United States)

Bennett, Kochise; Kowalewski, Markus; Mukamel, Shaul

2016-02-09

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.

Nanomechanical IR spectroscopy for fast analysis of liquid-dispersed engineered nanomaterials

OpenAIRE

Andersen, Alina Joukainen; Yamada, Shoko; Ek, Pramod Kumar; Andresen, Thomas Lars; Boisen, Anja; Schmid, Silvan

2016-01-01

The proliferated use of engineered nanomaterials (ENMs), e.g. in nanomedicine, calls for novel techniques allowing for fast and sensitive analysis of minute samples. Here we present nanomechanical IR spectroscopy (NAM-IR) for chemical analysis of picograms of ENMs. ENMs are nebulized directly from dispersion and efficiently collected on nanomechanical string resonators through a non-diffusion limited sampling method. Even very small amounts of sample can convert absorbed IR light into a measu...

Time-resolved materials science opportunities using synchrotron x-ray sources

International Nuclear Information System (INIS)

Larson, B.C.; Tischler, J.Z.

1995-06-01

The high brightness, high intensity, and pulsed time-structure of synchrotron sources provide new opportunities for time-resolved x-ray diffraction investigations. With third generation synchrotron sources coming on line, high brilliance and high brightness are now available in x-ray beams with the highest flux. In addition to the high average flux, the instantaneous flux available in synchrotron beams is greatly enhanced by the pulsed time structure, which consists of short bursts of x-rays that are separated by ∼tens to hundreds of nanoseconds. Time-resolved one- and two-dimensional position sensitive detection techniques that take advantage of synchrotron radiation for materials science x-ray diffraction investigations are presented, and time resolved materials science applications are discussed in terms of recent diffraction and spectroscopy results and materials research opportunities

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

International Nuclear Information System (INIS)

Nakaema, Walter Morinobu

2010-01-01

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 2 O (polyads 4υ, 4υ + δ) and O 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)

Studies of the reactions of hydrogen atoms by time-resolved E. S. R. spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Fessenden, R W; Verma, N C [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Chemistry

1977-01-01

Time-resolved e.s.r. spectroscopy has been used to follow directly the reactions of H atoms produced by pulse radiolysis of acid solutions. Detailed analysis of the time profile of the e.s.r. signal was carried out by means of modified Bloch equations. The increased signal found when a scavenger for OH such as t-butyl alcohol is present is shown to be mainly the result of slower H atom decay by radical-radical reaction. The reaction H + OH does not appear to produce any signal polarization. The decay curves observed in the presence of solute are readily accounted for by the treatment, and good plots of pseudo first-order rate constant against solute concentration are obtained. The absolute rate constants for reaction with H atoms are for methanol 2.5 x10/sup 6/, for ethanol 2.1 X 10/sup 7/, for isopropanol 6.8 x 10/sup 7/, and for succinic acid 3.0 x 10/sup 6/ dm/sup 3/ mol/sup -1/s/sup -1/. These values are in good agreement with the earlier chemical measurements.

Molecular orientation in aligned electrospun polyimide nanofibers by polarized FT-IR spectroscopy.

Science.gov (United States)

Yang, Haoqi; Jiang, Shaohua; Fang, Hong; Hu, Xiaowu; Duan, Gaigai; Hou, Haoqing

2018-07-05

Quantitative explanation on the improved mechanical properties of aligned electrospun polyimide (PI) nanofibers as the increased imidization temperatures is highly required. In this work, polarized FT-IR spectroscopy is applied to solve this problem. Based on the polarized FT-IR spectroscopy and the molecular model in the fibers, the length of the repeat unit of PI molecule, the angle between the fiber axis and the symmetric stretching direction of carbonyl group on the imide ring, and the angle between the PI molecular axis and fiber axis are all investigated. The Mark-Howink equation is used to calculate the number-average molar mass of PI molecules. The orientation states of PI molecules in the electrospun nanofibers are studied from the number-average molar mass of PI molecules and the average fiber diameter. Quantitative analysis of the orientation factor of PI molecules in the electrospun nanofibers is performed by polarized FT-IR spectroscopy. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

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

International Nuclear Information System (INIS)

Badaut, V.; Schlegel, M.L.; Descostes, M.; Moutiers, G.

2012-01-01

The reduction oxidation-reaction between aqueous selenite (SeO 3 2- ) and siderite (FeCO 3 (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)

Drift and transmission FT-IR spectroscopy of forest soils: an approach to determine decomposition processes of forest litter

International Nuclear Information System (INIS)

Haberhauer, G.; Gerzabek, M.H.

1999-06-01

A method is described to characterize organic soil layers using Fourier transformed infrared spectroscopy. The applicability of FT-IR, either dispersive or transmission, to investigate decomposition processes of spruce litter in soil originating from three different forest sites in two climatic regions was studied. Spectral information of transmission and diffuse reflection FT-IR spectra was analyzed and compared. For data evaluation Kubelka Munk (KM) transformation was applied to the DRIFT spectra. Sample preparation for DRIFT is simpler and less time consuming in comparison to transmission FT-IR, which uses KBr pellets. A variety of bands characteristics of molecular structures and functional groups has been identified for these complex samples. Analysis of both transmission FT-IR and DRIFT, showed that the intensity of distinct bands is a measure of the decomposition of forest litter. Interferences due to water adsorption spectra were reduced by DRIFT measurement in comparison to transmission FT-IR spectroscopy. However, data analysis revealed that intensity changes of several bands of DRIFT and transmission FT-IR were significantly correlated with soil horizons. The application of regression models enables identification and differentiation of organic forest soil horizons and allows to determine the decomposition status of soil organic matter in distinct layers. On the basis of the data presented in this study, it may be concluded that FT-IR spectroscopy is a powerful tool for the investigation of decomposition dynamics in forest soils. (author)

Excited-state relaxation dynamics of Re(I) tricarbonyl complexes with macrocyclic phenanthroline ligands studied by time-resolved IR spectroscopy

Czech Academy of Sciences Publication Activity Database

Blanco-Rodríguez, A. M.; Towrie, M.; Collin, J.; P.; Záliš, Stanislav; Vlček, Antonín

-, č. 20 (2009), s. 3941-3949 ISSN 1477-9226 R&D Projects: GA MŠk OC09043; GA MŠk OC 139 Institutional research plan: CEZ:AV0Z40400503 Keywords : Raman spectroscopy * molecular machine prototypes * infrared spectroscopy Subject RIV: CG - Electrochemistry Impact factor: 4.081, year: 2009

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)

Marczynski-Buehlow, Martin

2012-01-01

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

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

Time-resolved spectroscopy of laser-induced breakdown in water

Science.gov (United States)

Thomas, Robert J.; Hammer, Daniel X.; Noojin, Gary D.; Stolarski, David J.; Rockwell, Benjamin A.; Roach, William P.

1996-05-01

Laser pulses of 60-ps and 80-ps at a wavelength of 532-nm and 1064-nm respectively were used to produce laser induced breakdown in triple-distilled water. The resulting luminescent flash from the plasma was captured with an imaging spectrograph coupled to a streak camera with a 5-ps time resolution. The wavelength range was 350 to 900-nm. We present the resulting experimental data which gives plasma duration and time-resolved spectral information. Plasma temperature is also computed from the data. All parameters are presented at a pulse energy of 1-mJ and are compared with time-integrated spectra at the same pulse duration and at 5 to 7-ns pulse duration in a similar energy range.

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...

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

Energy Technology Data Exchange (ETDEWEB)

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

2008-07-01

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

Ultrafast time-resolved spectroscopy of lead halide perovskite films

Science.gov (United States)

Idowu, Mopelola A.; Yau, Sung H.; Varnavski, Oleg; Goodson, Theodore

2015-09-01

Recently, lead halide perovskites which are organic-inorganic hybrid structures, have been discovered to be highly efficient as light absorbers. Herein, we show the investigation of the excited state dynamics and emission properties of non-stoichiometric precursor formed lead halide perovskites grown by interdiffusion method using steady-state and time-resolved spectroscopic measurements. The influence of the different ratios of the non-stoichiometric precursor solution was examined. The observed photoluminescence properties were correlated with the femtosecond transient absorption measurements.

Proposals of electronic-vibrational energy relaxation studies by using laser pulses synchronized with IR-SR pulses

International Nuclear Information System (INIS)

Nakagawa, Hideyuki

2000-01-01

Synchrotron radiation is expected to be the sharp infrared light source for the advanced experiments on IR and FIR spectroscopy in wide research fields. Especially, synchronized use of SR with VIS and/or UV laser light is to be a promising technique for the research on the dynamical properties of the photo-excited states in condensed materials. Some proposals are attempted for high resolution IR spectroscopy to elucidate fine interaction of molecular ions in crystalline solids with their environmental field and for time-resolved IR spectroscopic studies on the electronic and vibrational energy relaxation by using laser pulses synchronized with IR-SR pulses. Several experimental results are presented in relevance to the subjects; on high-resolution FTIR spectra of cyanide ions and metal cyanide complexes in cadmium halide crystals, on the energy up-conversion process among the vibrational levels of cyanide ions in alkali halide crystals, and on the electronic-to-vibrational energy conversion process in metal cyanide complexes. (author)

The study of the curing of the polyurethane coating by method of IR spectroscopy

Directory of Open Access Journals (Sweden)

N. A. Korshunova

2016-12-01

Full Text Available The results of the study of the curing process of polyurethane compositions with participation of two different catalysts by the method of IR spectroscopy are given. The time dependences of curing of polyurethane coatings from concentrations of catalysts were determined, on the basis of which the most effective catalyst was selected.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-10-15

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

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

International Nuclear Information System (INIS)

Reduzzi, Maurizio; Carpeggiani, Paolo; Kühn, Sergei; Calegari, Francesca; Nisoli, Mauro; Stagira, Salvatore; Vozzi, Caterina; Dombi, Peter; Kahaly, Subhendu; Tzallas, Paris; Charalambidis, Dimitris; Varju, Katalin; Osvay, Karoly

2015-01-01

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

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.

Quantitative analysis of time-resolved infrared stimulated luminescence in feldspars

DEFF Research Database (Denmark)

Pagonis, Vasilis; Ankjærgaard, Christina; Jain, Mayank

2016-01-01

Time-resolved infrared-stimulated luminescence (TR-IRSL) from feldspar samples is of importance in the field of luminescence dating, since it provides information on the luminescence mechanism in these materials. In this paper we present new analytical equations which can be used to analyze TR-IR....... The equations are applied to experimental TR-IRSL data of natural feldspars, and good agreement is found between experimental and modeling results....

Nanomechanical IR Spectroscopy for the fast analysis of picogram samples of engineered nanomaterials

DEFF Research Database (Denmark)

Andersen, Alina Joukainen; Ek, Pramod Kumar; Andresen, Thomas Lars

2014-01-01

The proliferation of engineered nanomaterials (ENMs), e.g. in nanomedicine, demands for novel sensitive techniques allowing for the analysis of minute samples. We present nanoelectromechanical system-based IR spectroscopy (NEMS-IR) of picograms of polymeric micelles. The micelles are nebulized...

Ultra-Broadband Infrared Pulses from a Potassium-Titanyl Phosphate Optical Parametric Amplifier for VIS-IR-SFG Spectroscopy

Science.gov (United States)

Isaienko, Oleksandr; Borguet, Eric

A non-collinear KTP-OPA to provide ultra-broadband mid-infrared pulses was designed and characterized. With proper pulse-front and phase correction, the system has a potential for high-time resolution vibrational VIS-IR-SFG spectroscopy.

Application of Fourier-transform infrared (FT-IR) spectroscopy for simple and easy determination of chylomicron-triglyceride and very low density lipoprotein-triglyceride.

Science.gov (United States)

Sato, Kenichi; Seimiya, Masanori; Kodera, Yoshio; Kitamura, Akihide; Nomura, Fumio

2010-02-01

Fourier-transform infrared (FT-IR) spectroscopy is a simple and reagent-free physicochemical analysis method, and is a potential alternative to more time-consuming and labor-intensive procedures. In this study, we aimed to use FT-IR spectroscopy to determine serum concentrations of chylomicron-triglyceride (TG) and very low density lipoprotein (VLDL)-TG. We analyzed a chylomicron fraction and VLDL fraction, which had been obtained by ultracentrifugation, to search for wavelengths to designate to each fraction. Then, partial least square (PLS) calibrations were developed using a training set of samples, for which TG concentrations had been determined by conventional procedures. Validation was conducted with another set of samples using the PLS model to predict serum TG concentrations on the basis of the samples' IR spectra. We analyzed a total of 150 samples. Serum concentrations of chylomicron-TG and VLDL-TG estimated by FT-IR spectroscopy agreed well with those obtained by the reference method (r=0.97 for both lipoprotein fractions). FT-IR spectrometric analysis required 15mul of serum and was completed within 1min. Serum chylomicron-TG and VLDL-TG concentrations can be determined with FT-IR spectroscopy. This rapid and simple test may have a great impact on the management of patients with dyslipidemia. Copyright 2009. Published by Elsevier B.V.

Frequency-resolved pump-probe characterization of femtosecond infrared pulses

NARCIS (Netherlands)

Yeremenko, S.; Baltuška, A.; Haan, F. de; Pshenichnikov, M.S.; Wiersma, D.A.

2002-01-01

A novel method for ultrashort IR pulse characterization is presented. The technique utilizes a frequency-resolved pump-probe geometry that is common in applications of ultrafast spectroscopy, without any modifications of the setup. The experimental demonstration of the method was carried out to

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

Science.gov (United States)

Zaleski, Daniel P.; Prozument, Kirill

2017-06-01

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

Spectrally- and Time-Resolved Sum Frequency Generation (STiR-SFG): a new tool for ultrafast hydrogen bond dynamics at interfaces.

Science.gov (United States)

Benderskii, Alexander; Bordenyuk, Andrey; Weeraman, Champika

2006-03-01

The recently developed spectrally- and time-resolved Sum Frequency Generation (STiR-SFG) is a surface-selective 3-wave mixing (IR+visible) spectroscopic technique capable of measuring ultrafast spectral evolution of vibrational coherences. A detailed description of this measurement will be presented, and a noniterative method or deconvolving the laser pulses will be introduced to obtain the molecular response function. STiR-SFG, combined with the frequency-domain SFG spectroscopy, was applied to study hydrogen bonding dynamics at aqueous interfaces (D2O/CaF2). Spectral dynamics of the OD-stretch on the 50-150 fs time scale provides real-time observation of ultrafast H-bond rearrangement. Tuning the IR wavelength to the blue or red side of the OD-stretch transition, we selectively monitor the dynamics of different sub-ensembles in the distribution of the H-bond structures. The blue-side excitation (weaker H-bonding) shows monotonic red-shift of the OD-frequency. In contrast, the red-side excitation (stronger H-bonding structures) produces a blue-shift and a recursion, which may indicate the presence of an underdamped intermolecular mode of interfacial water. Effect of electrolyte concentration on the H-bond dynamics will be discussed.

Equilibrium constants in aqueous lanthanide and actinide chemistry from time-resolved fluorescence spectroscopy: The role of ground and excited state reactions

International Nuclear Information System (INIS)

Billard, I.; Luetzenkirchen, K.

2003-01-01

Equilibrium constants for aqueous reactions between lanthanide or actinide ions and (in-) organic ligands contain important information for various radiochemical problems, such as nuclear reprocessing or the migration of radioelements in the geosphere. We study the conditions required to determine equilibrium constants by time-resolved fluorescence spectroscopy measurements. Based on a simulation study it is shown that the possibility to determine equilibrium constants depends upon the reaction rates in the photoexcited states of the lanthanide or actinide ions. (orig.)

Validation of a high-power, time-resolved, near-infrared spectroscopy system for measurement of superficial and deep muscle deoxygenation during exercise.

Science.gov (United States)

Koga, Shunsaku; Barstow, Thomas J; Okushima, Dai; Rossiter, Harry B; Kondo, Narihiko; Ohmae, Etsuko; Poole, David C

2015-06-01

Near-infrared assessment of skeletal muscle is restricted to superficial tissues due to power limitations of spectroscopic systems. We reasoned that understanding of muscle deoxygenation may be improved by simultaneously interrogating deeper tissues. To achieve this, we modified a high-power (∼8 mW), time-resolved, near-infrared spectroscopy system to increase depth penetration. Precision was first validated using a homogenous optical phantom over a range of inter-optode spacings (OS). Coefficients of variation from 10 measurements were minimal (0.5-1.9%) for absorption (μa), reduced scattering, simulated total hemoglobin, and simulated O2 saturation. Second, a dual-layer phantom was constructed to assess depth sensitivity, and the thickness of the superficial layer was varied. With a superficial layer thickness of 1, 2, 3, and 4 cm (μa = 0.149 cm(-1)), the proportional contribution of the deep layer (μa = 0.250 cm(-1)) to total μa was 80.1, 26.9, 3.7, and 0.0%, respectively (at 6-cm OS), validating penetration to ∼3 cm. Implementation of an additional superficial phantom to simulate adipose tissue further reduced depth sensitivity. Finally, superficial and deep muscle spectroscopy was performed in six participants during heavy-intensity cycle exercise. Compared with the superficial rectus femoris, peak deoxygenation of the deep rectus femoris (including the superficial intermedius in some) was not significantly different (deoxyhemoglobin and deoxymyoglobin concentration: 81.3 ± 20.8 vs. 78.3 ± 13.6 μM, P > 0.05), but deoxygenation kinetics were significantly slower (mean response time: 37 ± 10 vs. 65 ± 9 s, P ≤ 0.05). These data validate a high-power, time-resolved, near-infrared spectroscopy system with large OS for measuring the deoxygenation of deep tissues and reveal temporal and spatial disparities in muscle deoxygenation responses to exercise. Copyright © 2015 the American Physiological Society.

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

Science.gov (United States)

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

2017-08-16

Static and time-resolved mid-infrared spectroscopy of ferromagnetic single crystal Hg 0.95 Cd 0.05 Cr 2 Se 4 was performed below the absorption edge, in order to reveal the origin of the electronic transitions contributing to the magneto-optical properties of this material. The mid-infrared spectroscopy reveals a strong absorption peak around 0.236 eV which formerly was assigned to a transition within the selenide-chromium complexes ([Formula: see text] Se -Cr 2+ ). To reveal the sensitivity of the transition to the magnetic order, we performed the studies in a temperature range across the Curie temperature and magnetic fields across the value at which the saturation of ferromagnetic magnetization occurs. Despite the fact that the Curie temperature of this ferromagnetic semiconductor is around 107 K, the intensity of the mid-infrared transition reduces substantially increasing the temperature, so that already at 70 K the absorption peak is hardly visible. Such a dramatic decrease of the oscillator strength is observed simultaneously with the strong red-shift of the absorption edge in the magnetic semiconductor. Employing a time-resolved pump-and-probe technique enabled us to determine the lifetime of the electrons in the excited state of this optical transition. In the temperature range from 7 K to 80 K, the lifetime changes from 3 ps to 6 ps. This behavior agrees with the phenomenon of giant oscillator strength described earlier for weakly bound excitons in nonmagnetic semiconductors.

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...

Detection of metanil yellow contamination in turmeric using FT-Raman and FT-IR spectroscopy

Science.gov (United States)

Dhakal, Sagar; Chao, Kuanglin; Qin, Jianwei; Kim, Moon; Schmidt, Walter; Chan, Dian

2016-05-01

Turmeric is well known for its medicinal value and is often used in Asian cuisine. Economically motivated contamination of turmeric by chemicals such as metanil yellow has been repeatedly reported. Although traditional technologies can detect such contaminants in food, high operational costs and operational complexities have limited their use to the laboratory. This study used Fourier Transform Raman Spectroscopy (FT-Raman) and Fourier Transform - Infrared Spectroscopy (FT-IR) to identify metanil yellow contamination in turmeric powder. Mixtures of metanil yellow in turmeric were prepared at concentrations of 30%, 25%, 20%, 15%, 10%, 5%, 1% and 0.01% (w/w). The FT-Raman and FT-IR spectral signal of pure turmeric powder, pure metanil yellow powder and the 8 sample mixtures were obtained and analyzed independently to identify metanil yellow contamination in turmeric. The results show that FT-Raman spectroscopy and FT-IR spectroscopy can detect metanil yellow mixed with turmeric at concentrations as low as 1% and 5%, respectively, and may be useful for non-destructive detection of adulterated turmeric powder.

High-repetition-rate setup for pump-probe time-resolved XUV-IR experiments employing ion and electron momentum imaging

Science.gov (United States)

Pathak, Shashank; Robatjazi, Seyyed Javad; Wright Lee, Pearson; Raju Pandiri, Kanaka; Rolles, Daniel; Rudenko, Artem

2017-04-01

J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan KS, USA We report on the development of a versatile experimental setup for XUV-IR pump-probe experiments using a 10 kHz high-harmonic generation (HHG) source and two different charged-particle momentum imaging spectrometers. The HHG source, based on a commercial KM Labs eXtreme Ultraviolet Ultrafast Source, is capable of delivering XUV radiation of less than 30 fs pulse duration in the photon energy range of 17 eV to 100 eV. It can be coupled either to a conventional velocity map imaging (VMI) setup with an atomic, molecular, or nanoparticle target; or to a novel double-sided VMI spectrometer equipped with two delay-line detectors for coincidence studies. An overview of the setup and results of first pump-probe experiments including studies of two-color double ionization of Xe and time-resolved dynamics of photoionized CO2 molecule will be presented. This project is supported in part by National Science Foundation (NSF-EPSCOR) Award No. IIA-1430493 and in part by the Chemical science, Geosciences, and Bio-Science division, Office of Basic Energy Science, Office of science, U.S. Department of Energy. K.

Factors affecting measurement of optic parameters by time-resolved near-infrared spectroscopy in breast cancer

Science.gov (United States)

Yoshizawa, Nobuko; Ueda, Yukio; Mimura, Tetsuya; Ohmae, Etsuko; Yoshimoto, Kenji; Wada, Hiroko; Ogura, Hiroyuki; Sakahara, Harumi

2018-02-01

The purpose of this study was to evaluate the effects of the thickness and depth of tumors on hemoglobin measurements in breast cancer by optical spectroscopy and to demonstrate tissue oxygen saturation (SO2) and reduced scattering coefficient (μs‧) in breast tissue and breast cancer in relation to the skin-to-chest wall distance. We examined 53 tumors from 44 patients. Total hemoglobin concentration (tHb), SO2, and μs‧ were measured by time-resolved spectroscopy (TRS). The skin-to-chest wall distance and the size and depth of tumors were measured by ultrasonography. There was a positive correlation between tHb and tumor thickness, and a negative correlation between tHb and tumor depth. SO2 in breast tissue decreased when the skin-to-chest wall distance decreased, and SO2 in tumors tended to be lower than in breast tissue. In breast tissue, there was a negative correlation between μs‧ and the skin-to-chest wall distance, and μs‧ in tumors was higher than in breast tissue. Measurement of tHb in breast cancer by TRS was influenced by tumor thickness and depth. Although SO2 seemed lower and μs‧ was higher in breast cancer than in breast tissue, the skin-to-chest wall distance may have affected the measurements.

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

International Nuclear Information System (INIS)

Miyashita, Atsumi; Yoda, Osamu; Ohyanagi, T.; Murakami, K.

1995-01-01

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/cm 2 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 (C 0 ), C - , C + and C 2+ ions were observed. The absorption peak from C 0 was stronger as the probing position was closer to the sample surface and decreased rapidly with distance from the sample surface. The absorption peak C 2+ 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)

Time-Resolved Spectroscopy and Near Infrared Imaging for Prostate Cancer Detection: Receptor-targeted and Native Biomarker

Science.gov (United States)

Pu, Yang

Optical spectroscopy and imaging using near-infrared (NIR) light provides powerful tools for non-invasive detection of cancer in tissue. Optical techniques are capable of quantitative reconstructions maps of tissue absorption and scattering properties, thus can map in vivo the differences in the content of certain marker chromophores and/or fluorophores in normal and cancerous tissues (for example: water, tryptophan, collagen and NADH contents). Potential clinical applications of optical spectroscopy and imaging include functional tumor detection and photothermal therapeutics. Optical spectroscopy and imaging apply contrasts from intrinsic tissue chromophores such as water, collagen and NADH, and extrinsic optical contrast agents such as Indocyanine Green (ICG) to distinguish disease tissue from the normal one. Fluorescence spectroscopy and imaging also gives high sensitivity and specificity for biomedical diagnosis. Recent developments on specific-targeting fluorophores such as small receptor-targeted dye-peptide conjugate contrast agent offer high contrast between normal and cancerous tissues hence provide promising future for early tumour detection. This thesis focus on a study to distinguish the cancerous prostate tissue from the normal prostate tissues with enhancement of specific receptor-targeted prostate cancer contrast agents using optical spectroscopy and imaging techniques. The scattering and absorption coefficients, and anisotropy factor of cancerous and normal prostate tissues were investigated first as the basis for the biomedical diagnostic and optical imaging. Understanding the receptors over-expressed prostate cancer cells and molecular target mechanism of ligand, two small ICG-derivative dye-peptides, namely Cypate-Bombesin Peptide Analogue Conjugate (Cybesin) and Cypate-Octreotate Peptide Conjugate (Cytate), were applied to study their clinical potential for human prostate cancer detection. In this work, the steady-state and time-resolved

Differentiation of Leishmania species by FT-IR spectroscopy

Science.gov (United States)

Aguiar, Josafá C.; Mittmann, Josane; Ferreira, Isabelle; Ferreira-Strixino, Juliana; Raniero, Leandro

2015-05-01

Leishmaniasis is a parasitic infectious disease caused by protozoa that belong to the genus Leishmania. It is transmitted by the bite of an infected female Sand fly. The disease is endemic in 88 countries Desjeux (2001) [1] (16 developed countries and 72 developing countries) on four continents. In Brazil, epidemiological data show the disease is present in all Brazilian regions, with the highest incidences in the North and Northeast. There are several methods used to diagnose leishmaniasis, but these procedures have many limitations, are time consuming, have low sensitivity, and are expensive. In this context, Fourier Transform Infrared Spectroscopy (FT-IR) analysis has the potential to provide rapid results and may be adapted for a clinical test with high sensitivity and specificity. In this work, FT-IR was used as a tool to investigate the promastigotes of Leishmaniaamazonensis, Leishmaniachagasi, and Leishmaniamajor species. The spectra were analyzed by cluster analysis and deconvolution procedure base on spectra second derivatives. Results: cluster analysis found four specific regions that are able to identify the Leishmania species. The dendrogram representation clearly indicates the heterogeneity among Leishmania species. The band deconvolution done by the curve fitting in these regions quantitatively differentiated the polysaccharides, amide III, phospholipids, proteins, and nucleic acids. L. chagasi and L. major showed a greater biochemistry similarity and have three bands that were not registered in L. amazonensis. The L. amazonensis presented three specific bands that were not recorded in the other two species. It is evident that the FT-IR method is an indispensable tool to discriminate these parasites. The high sensitivity and specificity of this technique opens up the possibilities for further studies about characterization of other microorganisms.

Monitoring wine aging with Fourier transform infrared spectroscopy (FT-IR

Directory of Open Access Journals (Sweden)

Basalekou Marianthi

2015-01-01

Full Text Available Oak wood has commonly been used in wine aging but recently other wood types such as Acacia and Chestnut, have attracted the interest of the researchers due to their possible positive contribution to wine quality. However, only the use of oak and chestnut woods is approved by the International Enological Codex of the International Organisation of Vine and Wine. In this study Fourier Transform (FT-mid-infrared spectroscopy combined with Discriminant Analysis was used to differentiate wines aged in barrels made from French oak, American oak, Acacia and Chestnut and in tanks with oak chips, over a period of 12 months. Two red (Mandilaria, Kotsifali and two white (Vilana, Dafni native Greek grape varieties where used to produce four wines. The Fourier Transform Infrared (FT-IR spectra of the samples were recorded on a Zinc Selenide (ZnSe window after incubation at 40 °C for 30 min. A complete differentiation of the samples according to both the type of wood used and the contact time was achieved based on their FT-IR spectra.

Orbital Evolution and Orbital Phase Resolved Spectroscopy of the ...

Indian Academy of Sciences (India)

binary. We have carried out orbital phase resolved spectroscopy to mea- ... agreement with a simple model of a spherically symmetric stellar wind from the .... has a set of Narrow Field Instruments (NFI) comprising one Low Energy Concen-.

Application of FT-IR spectroscopy on breast cancer serum analysis

Science.gov (United States)

Elmi, Fatemeh; Movaghar, Afshin Fayyaz; Elmi, Maryam Mitra; Alinezhad, Heshmatollah; Nikbakhsh, Novin

2017-12-01

Breast cancer is regarded as the most malignant tumor among women throughout the world. Therefore, early detection and proper diagnostic methods have been known to help save women's lives. Fourier Transform Infrared (FT-IR) spectroscopy, coupled with PCA-LDA analysis, is a new technique to investigate the characteristics of serum in breast cancer. In this study, 43 breast cancer and 43 healthy serum samples were collected, and the FT-IR spectra were recorded for each one. Then, PCA analysis and linear discriminant analysis (LDA) were used to analyze the spectral data. The results showed that there were differences between the spectra of the two groups. Discriminating wavenumbers were associated with several spectral differences over the 950-1200 cm- 1(sugar), 1190-1350 cm- 1 (collagen), 1475-1710 cm- 1 (protein), 1710-1760 cm- 1 (ester), 2800-3000 cm- 1 (stretching motions of -CH2 & -CH3), and 3090-3700 cm- 1 (NH stretching) regions. PCA-LDA performance on serum IR could recognize changes between the control and the breast cancer cases. The diagnostic accuracy, sensitivity, and specificity of PCA-LDA analysis for 3000-3600 cm- 1 (NH stretching) were found to be 83%, 84%, 74% for the control and 80%, 76%, 72% for the breast cancer cases, respectively. The results showed that the major spectral differences between the two groups were related to the differences in protein conformation in serum samples. It can be concluded that FT-IR spectroscopy, together with multivariate data analysis, is able to discriminate between breast cancer and healthy serum samples.

Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing.

Science.gov (United States)

Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

2016-02-17

The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF₂ microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

Rapid identification of Chinese Sauce liquor from different fermentation positions with FT-IR spectroscopy

Science.gov (United States)

Li, Changwen; Wei, Jiping; Zhou, Qun; Sun, Suqin

2008-07-01

FT-IR and two-dimensional correlation spectroscopy (2D-IR) technology were applied to discriminate Chinese Sauce liquor from different fermentation positions (top, middle and bottom of fermentation cellar) for the first time. The liquors at top, middle and bottom of fermentation cellar, possessed the characteristic peaks at 1731 cm -1, 1733 cm -1 and 1602 cm -1, respectively. In the 2D correlation infrared spectra, the differences were amplified. A strong auto-peak at 1725 cm -1 showed in the 2D spectra of the Top Liquor, which indicated that the liquor might contain some ester compounds. Different from Top Liquor, three auto-peaks at 1695, 1590 and 1480 cm -1 were identified in 2D spectra of Middle Liquor, which were the characteristic absorption of acid, lactate. In 2D spectra of Bottom Liquor, two auto-peaks at 1570 and 1485 cm -1 indicated that lactate was the major component. As a result, FT-IR and 2D-IR correlation spectra technology provided a rapid and effective method for the quality analysis of the Sauce liquor.

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

Covariance J-resolved spectroscopy: Theory and application in vivo.

Science.gov (United States)

Iqbal, Zohaib; Verma, Gaurav; Kumar, Anand; Thomas, M Albert

2017-08-01

Magnetic resonance spectroscopy (MRS) is a powerful tool capable of investigating the metabolic status of several tissues in vivo. In particular, single-voxel-based 1 H spectroscopy provides invaluable biochemical information from a volume of interest (VOI) and has therefore been used in a variety of studies. Unfortunately, typical one-dimensional MRS data suffer from severe signal overlap and thus important metabolites are difficult to distinguish. One method that is used to disentangle overlapping resonances is the two-dimensional J-resolved spectroscopy (JPRESS) experiment. Due to the long acquisition duration of the JPRESS experiment, a limited number of points are acquired in the indirect dimension, leading to poor spectral resolution along this dimension. Poor spectral resolution is problematic because proper peak assignment may be hindered, which is why the zero-filling method is often used to improve resolution as a post-processing step. However, zero-filling leads to spectral artifacts, which may affect visualization and quantitation of spectra. A novel method utilizing a covariance transformation, called covariance J-resolved spectroscopy (CovJ), was developed in order to improve spectral resolution along the indirect dimension (F 1 ). Comparison of simulated data demonstrates that peak structures remain qualitatively similar between JPRESS and the novel method along the diagonal region (F 1 = 0 Hz), whereas differences arise in the cross-peak (F 1 ≠0 Hz) regions. In addition, quantitative results of in vivo JPRESS data acquired on a 3T scanner show significant correlations (r 2 >0.86, pCOVariance Spectral Evaluation of 1 H Acquisitions using Representative prior knowledge' (Cov-SEHAR), was developed in order to quantify γ-aminobutyric acid and glutamate from the CovJ spectra. These preliminary findings indicate that the CovJ method may be used to improve spectral resolution without hindering metabolite quantitation for J-resolved spectra

Near-Infrared Spatially Resolved Spectroscopy for Tablet Quality Determination.

Science.gov (United States)

Igne, Benoît; Talwar, Sameer; Feng, Hanzhou; Drennen, James K; Anderson, Carl A

2015-12-01

Near-infrared (NIR) spectroscopy has become a well-established tool for the characterization of solid oral dosage forms manufacturing processes and finished products. In this work, the utility of a traditional single-point NIR measurement was compared with that of a spatially resolved spectroscopic (SRS) measurement for the determination of tablet assay. Experimental designs were used to create samples that allowed for calibration models to be developed and tested on both instruments. Samples possessing a poor distribution of ingredients (highly heterogeneous) were prepared by under-blending constituents prior to compaction to compare the analytical capabilities of the two NIR methods. The results indicate that SRS can provide spatial information that is usually obtainable only through imaging experiments for the determination of local heterogeneity and detection of abnormal tablets that would not be detected with single-point spectroscopy, thus complementing traditional NIR measurement systems for in-line, and in real-time tablet analysis. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Advanced multivariate data evaluation for Fourier transform infrared spectroscopy

International Nuclear Information System (INIS)

Diewok, J.

2002-12-01

The objective of the presented dissertation was the evaluation, application and further development of advanced multivariate data evaluation methods for qualitative and quantitative Fourier transform infrared (FT-IR) measurements, especially of aqueous samples. The focus was set on 'evolving systems'; i.e. chemical systems that change gradually with a master variable, such as pH, reaction time, elution time, etc. and that are increasingly encountered in analytical chemistry. FT-IR measurements on such systems yield 2-way and 3-way data sets, i.e. data matrices and cubes. The chemometric methods used were soft-modeling techniques, like multivariate curve resolution - alternating least squares (MCR-ALS) or principal component analysis (PCA), hard modeling of equilibrium systems and two-dimensional correlation spectroscopy (2D-CoS). The research results are presented in six publications and comprise: A new combination of FT-IR flow titrations and second-order calibration by MCR-ALS for the quantitative analysis of mixture samples of organic acids and sugars. A novel combination of MCR-ALS with a hard-modeled equilibrium constraint for second-order quantitation in pH-modulated samples where analytes and interferences show very similar acid-base behavior. A detailed study in which MCR-ALS and 2D-CoS are directly compared for the first time. From the analysis of simulated and experimental acid-base equilibrium systems, the performance and interpretability of the two methods is evaluated. Investigation of the binding process of vancomycin, an important antibiotic, to a cell wall analogue tripeptide by time-resolved FT-IR spectroscopy and detailed chemometric evaluation. Determination of red wine constituents by liquid chromatography with FT-IR detection and MCR-ALS for resolution of overlapped peaks. Classification of red wine cultivars from FT-IR spectroscopy of phenolic wine extracts with hierarchical clustering and soft independent modeling of class analogy (SIMCA

Investigation of Co nanoparticle formation using time-dependent and spatially-resolved X-ray absorption spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Zinoveva, S

2008-04-15

A crucial step towards controlled synthesis of nanoparticles is the detailed understanding of the various chemical processes that take place during the synthesis. X-ray Absorption Spectroscopy (XAS) is especially suitable for elucidating the type and structure of the intermediate metal species. It is applicable to materials that have no long range order and provides information on both electronic and geometric structures. Here a comparative study is reported of the formation of cobalt nanoparticles via thermolysis of two organometallic precursors dicobalt octacarbonyl (DCO) and alkyne-bridged dicobalt hexacarbonyl (ADH) in the presence of aluminum organics. Using time-dependent XAS a reaction pathway different from both the atom based La Mer model and the Watzky and Finsky autocatalytic surface growth model is observed. Where prior to the nucleation several intermediates are formed and the initial nucleus is composed of Co atoms coordinated with ligands Co{sub n}(CO){sub m} with n=2-3, m=3-5. The formation of Co nanoparticles was also investigated using a reaction different from thermolysis of cobalt carbonyls, namely reduction of Co (II) acetate by sodium borohydrate. Here the combination of microreactor system and spatially resolved XAS allowed ''in situ'' monitoring of the wet chemical synthesis. Several steps of the reaction were spatially resolved in the microreactor. The vertical size of the X-ray beam (50 {mu}m) focused with Kirkpatrick-Baez mirror system, determines the time resolution (better than 2 ms). The results provide direct insight into rapid process of nanoparticles formation and demonstrate the potential of this new technique for the fundamental studies of such type of processes where miniaturization and timeresolution are important. Like in the carbonyls thermolysis no evidence for the reduction of the starting complex to isolated Co{sup 0} atoms followed by nucleation of Co{sup 0} atoms was observed. (orig.)

Investigation of Co nanoparticle formation using time-dependent and spatially-resolved X-ray absorption spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Zinoveva, S.

2008-04-15

A crucial step towards controlled synthesis of nanoparticles is the detailed understanding of the various chemical processes that take place during the synthesis. X-ray Absorption Spectroscopy (XAS) is especially suitable for elucidating the type and structure of the intermediate metal species. It is applicable to materials that have no long range order and provides information on both electronic and geometric structures. Here a comparative study is reported of the formation of cobalt nanoparticles via thermolysis of two organometallic precursors dicobalt octacarbonyl (DCO) and alkyne-bridged dicobalt hexacarbonyl (ADH) in the presence of aluminum organics. Using time-dependent XAS a reaction pathway different from both the atom based La Mer model and the Watzky and Finsky autocatalytic surface growth model is observed. Where prior to the nucleation several intermediates are formed and the initial nucleus is composed of Co atoms coordinated with ligands Co{sub n}(CO){sub m} with n=2-3, m=3-5. The formation of Co nanoparticles was also investigated using a reaction different from thermolysis of cobalt carbonyls, namely reduction of Co (II) acetate by sodium borohydrate. Here the combination of microreactor system and spatially resolved XAS allowed ''in situ'' monitoring of the wet chemical synthesis. Several steps of the reaction were spatially resolved in the microreactor. The vertical size of the X-ray beam (50 {mu}m) focused with Kirkpatrick-Baez mirror system, determines the time resolution (better than 2 ms). The results provide direct insight into rapid process of nanoparticles formation and demonstrate the potential of this new technique for the fundamental studies of such type of processes where miniaturization and timeresolution are important. Like in the carbonyls thermolysis no evidence for the reduction of the starting complex to isolated Co{sup 0} atoms followed by nucleation of Co{sup 0} atoms was observed. (orig.)

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.

Time-resolved imaging of purely valence-electron dynamics during a chemical reaction

DEFF Research Database (Denmark)

Hockett, Paul; Bisgaard, Christer Z.; Clarkin, Owen J.

2011-01-01

Chemical reactions are manifestations of the dynamics of molecular valence electrons and their couplings to atomic motions. Emerging methods in attosecond science can probe purely electronic dynamics in atomic and molecular systems(1-6). By contrast, time-resolved structural-dynamics methods...... such as electron(7-10) or X-ray diffraction(11) and X-ray absorption(12) yield complementary information about the atomic motions. Time-resolved methods that are directly sensitive to both valence-electron dynamics and atomic motions include photoelectron spectroscopy(13-15) and high-harmonic generation(16......,17): in both cases, this sensitivity derives from the ionization-matrix element(18,19). Here we demonstrate a time-resolved molecular-frame photoelectron-angular-distribution (TRMFPAD) method for imaging the purely valence-electron dynamics during a chemical reaction. Specifically, the TRMFPADs measured during...

Laser Spark Formamide Decomposition Studied by FT-IR Spectroscopy

Czech Academy of Sciences Publication Activity Database

Ferus, Martin; Kubelík, Petr; Civiš, Svatopluk

2011-01-01

Roč. 115, č. 44 (2011), s. 12132-12141 ISSN 1089-5639 R&D Projects: GA AV ČR IAA400400705; GA AV ČR IAAX00100903; GA ČR GAP208/10/2302 Institutional research plan: CEZ:AV0Z40400503 Keywords : FT-IR spectroscopy * high-power laser * induced dielectric-breakdown Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.946, year: 2011

IRMPD Spectroscopy Sheds New (Infrared) Light on the Sulfate Pattern of Carbohydrates.

Science.gov (United States)

Schindler, B; Barnes, L; Gray, C J; Chambert, S; Flitsch, S L; Oomens, J; Daniel, R; Allouche, A R; Compagnon, I

2017-03-16

IR spectroscopy of gas-phase ions is proposed to resolve positional isomers of sulfated carbohydrates. Mass spectrometric fingerprints and gas-phase vibrational spectra in the near and mid-IR regions were obtained for sulfated monosaccharides, yielding unambiguous signatures of sulfated isomers. We report the first systematic exploration of the biologically relevant but notoriously challenging deprotonated state in the near IR region. Remarkably, anions displayed very atypical vibrational profiles, which challenge the well-established DFT (Density Functionnal Theory) modeling. The proposed approach was used to elucidate the sulfate patterns in glycosaminoglycans, a ubiquitous class of mammalian carbohydrates, which is regarded as a major challenge in carbohydrate structural analysis. Isomeric glycosaminoglycan disaccharides from heparin and chondroitin sources were resolved, highlighting the potential of infrared multiple photon dissociation spectroscopy as a novel structural tool for carbohydrates.

Dissociation dynamics of CH3I in electric spark induced breakdown revealed by time-resolved laser induced breakdown spectroscopy

International Nuclear Information System (INIS)

Wang, Yang; Liu, Wei-long; Song, Yun-fei; Duo, Li-ping; Liu, Yu-qiang; Yang, Yan-qiang

2015-01-01

Highlights: • Emission of electric spark dissociation of CH 3 I is similar to its fs LIBS. • We use fs laser induced breakdown as a simulation for electric spark dissociation. • The I 2 molecule formation is directly observed in the time-resolved LIBS. • Bimolecular collision of I ∗ and CH 3 I is responsible for the formation of I 2 . - Abstract: The electric discharge spark dissociation of gas CH 3 I is found to be similar to its femtosecond laser photodissociation. The almost identical spectra of the two processes show that their initial ionization conditions are very similar. The initial ionization followed by molecular fragmentation is proposed as the dissociation mechanism, in which the characteristic emissions of I + , CH 3 , CH 2 , CH, H, and I 2 are identified as the dissociation products. The emission band of 505 nm I 2 is clearly observed in the time-resolved laser induced breakdown spectroscopy (LIBS). The dynamic curve indicates that I 2 ∗ molecules are formed after the delay time of ∼4.7 ns. The formation of I 2 ∗ molecule results from the bimolecular collision of the highly excited iodine atom I ∗ ( 4 P) and CH 3 I molecule. This dynamical information can help understand the process of electric discharge spark dissociation of CH 3 I

Time Resolved X-Ray Scattering of molecules in Solution

DEFF Research Database (Denmark)

Brandt van Driel, Tim

The dissertation describes the use of Time-Resolved X-ray Diffuse Scattering (TR-XDS) to study photo-induced structural changes in molecules in solution. The application of the technique is exemplified with experiments on two bimetallic molecules. The main focus is on the data-flow and process......)42+ obtained at European Synchrotron Radiation Facility (ESRF) are presented to exemplify TR-XDS at synchrotrons. Similarly, measurements on Ir2(dimen)42+ are used to show the XFEL data-flow and how it deviates from the prior. A method to identify and account for systematic fluctuations...

Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing

Directory of Open Access Journals (Sweden)

Simone Borri

2016-02-01

Full Text Available The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF2 microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

The discrimination of 72 nitrate, chlorate and perchlorate salts using IR and Raman spectroscopy

Science.gov (United States)

Zapata, Félix; García-Ruiz, Carmen

2018-01-01

Inorganic oxidizing energetic salts including nitrates, chlorates and perchlorates are widely used in the manufacture of not only licit pyrotechnic compositions, but also illicit homemade explosive mixtures. Their identification in forensic laboratories is usually accomplished by either capillary electrophoresis or ion chromatography, with the disadvantage of dissociating the salt into its ions. On the contrary, vibrational spectroscopy, including IR and Raman, enables the non-invasive identification of the salt, i.e. avoiding its dissociation. This study focuses on the discrimination of all nitrate, chlorate and perchlorate salts that are commercially available, using both Raman and IR spectroscopy, with the aim of testing whether every salt can be unequivocally identified. Besides the visual spectra comparison by assigning every band with the corresponding molecular vibrational mode, a statistical analysis based on Pearson correlation was performed to ensure an objective identification, either using Raman, IR or both. Positively, 25 salts (out of 72) were unequivocally identified using Raman, 30 salts when using IR and 44 when combining both techniques. Negatively, some salts were undistinguishable even using both techniques demonstrating there are some salts that provide very similar Raman and IR spectra.

Surface State Dynamics of Topological Insulators Investigated by Femtosecond Time- and Angle-Resolved Photoemission Spectroscopy

Directory of Open Access Journals (Sweden)

Hamoon Hedayat

2018-04-01

Full Text Available Topological insulators (TI are known for striking quantum phenomena associated with their spin-polarized topological surface state (TSS. The latter in particular forms a Dirac cone that bridges the energy gap between valence and conduction bands, providing a unique opportunity for prospective device applications. In TI of the BixSb2−xTeySe3−y (BSTS family, stoichiometry determines the morphology and position of the Dirac cone with respect to the Fermi level. In order to engineer specific transport properties, a careful tuning of the TSS is highly desired. Therefore, we have systematically explored BSTS samples with different stoichiometries by time- and angle-resolved photoemission spectroscopy (TARPES. This technique provides snapshots of the electronic structure and discloses the carrier dynamics in surface and bulk states, providing crucial information for the design of electro-spin current devices. Our results reveal the central role of doping level on the Dirac cone structure and its femtosecond dynamics. In particular, an extraordinarily long TSS lifetime is observed when the the vertex of the Dirac cone lies at the Fermi level.

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

International Nuclear Information System (INIS)

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

2004-01-01

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 (SmO 2 ) and total haemoglobin concentration (tHb) during dynamic plantar flexion exercise performed at 50% of the maximal voluntary contraction. At rest SmO 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 2 decreased (69.1 ± 1.8 and 63.8 ± 2.1% in MG and LG, respectively; P 2 and tHb

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

Science.gov (United States)

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

2015-06-22

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

Pump laser-induced space-charge effects in HHG-driven time- and angle-resolved photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Oloff, L.-P., E-mail: oloff@physik.uni-kiel.de; Hanff, K.; Stange, A.; Rohde, G.; Diekmann, F.; Bauer, M.; Rossnagel, K., E-mail: rossnagel@physik.uni-kiel.de [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel (Germany)

2016-06-14

With the advent of ultrashort-pulsed extreme ultraviolet sources, such as free-electron lasers or high-harmonic-generation (HHG) sources, a new research field for photoelectron spectroscopy has opened up in terms of femtosecond time-resolved pump-probe experiments. The impact of the high peak brilliance of these novel sources on photoemission spectra, so-called vacuum space-charge effects caused by the Coulomb interaction among the photoemitted probe electrons, has been studied extensively. However, possible distortions of the energy and momentum distributions of the probe photoelectrons caused by the low photon energy pump pulse due to the nonlinear emission of electrons have not been studied in detail yet. Here, we systematically investigate these pump laser-induced space-charge effects in a HHG-based experiment for the test case of highly oriented pyrolytic graphite. Specifically, we determine how the key parameters of the pump pulse—the excitation density, wavelength, spot size, and emitted electron energy distribution—affect the measured time-dependent energy and momentum distributions of the probe photoelectrons. The results are well reproduced by a simple mean-field model, which could open a path for the correction of pump laser-induced space-charge effects and thus toward probing ultrafast electron dynamics in strongly excited materials.

Rapid and economical data acquisition in ultrafast frequency-resolved spectroscopy using choppers and a microcontroller.

Science.gov (United States)

Guo, Liang; Monahan, Daniele M; Fleming, Graham

2016-08-08

Spectrometers and cameras are used in ultrafast spectroscopy to achieve high resolution in both time and frequency domains. Frequency-resolved signals from the camera pixels cannot be processed by common lock-in amplifiers, which have only a limited number of input channels. Here we demonstrate a rapid and economical method that achieves the function of a lock-in amplifier using mechanical choppers and a programmable microcontroller. We demonstrate the method's effectiveness by performing a frequency-resolved pump-probe measurement on the dye Nile Blue in solution.

Sensitivity enhancement of 13C nuclei in 2D J-resolved NMR spectroscopy using a recycled-flow system

International Nuclear Information System (INIS)

Ha, S.T.K.; Lee, R.W.K.; Wilkins, C.L.

1987-01-01

Recycled-flow nuclear magnetic resonance for sensitivity enhancement in 1/2 spin nuclei has been reported previously, achieving several-fold signal enhancement. The success of the method depends upon premagnetization of nuclei prior to flowing into the detector region, obviating the need for delays following data acquisition to allow spin-lattice relaxation and reduce experiment time. The actual gains of sensitivity enhancement for 13 C- 1 H 2D J-resolved NMR using a recycled-flow method are evaluated. Possible enhancements for two types of J-resolved measurements, namely, one-bond 13 C- 1 H and long range J-resolved spectroscopy, are estimated using a simple Carr-Purcell spin-echo approach to quantify the 13 C signals. The pulse sequence is simply 90 0 -t /sub 1/2/-180 0 -t/sub 1/2/-AT-t/sub d/, where t/sub 1/2/ is half the evolution time, AT is the acquisition time, and t/sub d/ the experiment repetition time. In a static 2D NMR experiment, t/sub d/ usually must be the same order of the longest spin-lattice relaxation time (T 1 ) of nuclei. Quantitative measurements using a recycled-flow system indicate t/dub d/ can be reduced to a fraction of T 1 ; hence significant time savings can be achieved. Time-savings of between 2 and 25 can be anticipated for 2D spectroscopy under flow measurement conditions used in the present study. Other types of 2D NMR spectroscopy (autocorrelation and double quantum NMR) are discussed

Combined IR-Raman vs vibrational sum-frequency heterospectral correlation spectroscopy

Science.gov (United States)

Roy, Sandra; Beutier, Clémentine; Hore, Dennis K.

2018-06-01

Vibrational sum-frequency generation spectroscopy is a valuable probe of surface structure, particularly when the same molecules are present in one of the adjacent bulk solid or solution phases. As a result of the non-centrosymmetric requirement of SFG, the signal generated is a marker of the extent to which the molecules are ordered in an arrangement that breaks the up-down symmetry at the surface. In cases where the accompanying changes in the bulk are of interest in understanding and interpreting the surface structure, simultaneous analysis of the bulk IR absorption or bulk Raman scattering is helpful, and may be used in heterospectral surface-bulk two-dimensional correlation. We demonstrate that, in such cases, generating a new type of bulk spectrum that combines the IR and Raman amplitudes is a better candidate than the individual IR and Raman spectra for the purpose of correlation with the SFG signal.

Two-dimensional infrared spectroscopy of vibrational polaritons.

Science.gov (United States)

Xiang, Bo; Ribeiro, Raphael F; Dunkelberger, Adam D; Wang, Jiaxi; Li, Yingmin; Simpkins, Blake S; Owrutsky, Jeffrey C; Yuen-Zhou, Joel; Xiong, Wei

2018-04-19

We report experimental 2D infrared (2D IR) spectra of coherent light-matter excitations--molecular vibrational polaritons. The application of advanced 2D IR spectroscopy to vibrational polaritons challenges and advances our understanding in both fields. First, the 2D IR spectra of polaritons differ drastically from free uncoupled excitations and a new interpretation is needed. Second, 2D IR uniquely resolves excitation of hybrid light-matter polaritons and unexpected dark states in a state-selective manner, revealing otherwise hidden interactions between them. Moreover, 2D IR signals highlight the impact of molecular anharmonicities which are applicable to virtually all molecular systems. A quantum-mechanical model is developed which incorporates both nuclear and electrical anharmonicities and provides the basis for interpreting this class of 2D IR spectra. This work lays the foundation for investigating phenomena of nonlinear photonics and chemistry of molecular vibrational polaritons which cannot be probed with traditional linear spectroscopy.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-09-15

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Spectroscopy of Molecules in Extreme Rotational States Using AN Optical Centrifuge

Science.gov (United States)

Mullin, Amy S.; Toro, Carlos; Echibiri, Geraldine; Liu, Qingnan

2012-06-01

Our lab has developed a high-power optical centrifuge that is capable of trapping and spinning large number densities of molecules into extreme rotational states. By coupling this device with high resolution transient IR absorption spectroscopy, we measure the time-resolved behavior and energy profiles of individual ro-vibrational states of molecules in very high rotational states. Recent results will be discussed on the spectroscopy of new rotational states, collisional dynamics in the optical centrifuge, spatially-dependent energy profiles and possibilities for new chemistry induced by centrifugal forces.

Ultrafast time-resolved spectroscopy of xanthophylls at low temperature.

Science.gov (United States)

Cong, Hong; Niedzwiedzki, Dariusz M; Gibson, George N; Frank, Harry A

2008-03-20

Many of the spectroscopic features and photophysical properties of xanthophylls and their role in energy transfer to chlorophyll can be accounted for on the basis of a three-state model. The characteristically strong visible absorption of xanthophylls is associated with a transition from the ground state S0 (1(1)Ag-) to the S2 (1(1)Bu+) excited state. The lowest lying singlet state denoted S1 (2(1)Ag-), is a state into which absorption from the ground state is symmetry forbidden. Ultrafast optical spectroscopic studies and quantum computations have suggested the presence of additional excited singlet states in the vicinity of S1 (2(1)Ag-) and S2 (1(1)Bu+). One of these is denoted S* and has been suggested in previous work to be associated with a twisted molecular conformation of the molecule in the S1 (2(1)Ag-) state. In this work, we present the results of a spectroscopic investigation of three major xanthophylls from higher plants: violaxanthin, lutein, and zeaxanthin. These molecules have systematically increasing extents of pi-electron conjugation from nine to eleven conjugated carbon-carbon double bonds. All-trans isomers of the molecules were purified by high-performance liquid chromatography (HPLC) and studied by steady-state and ultrafast time-resolved optical spectroscopy at 77 K. Analysis of the data using global fitting techniques has revealed the inherent spectral properties and ultrafast dynamics of the excited singlet states of each of the molecules. Five different global fitting models were tested, and it was found that the data are best explained using a kinetic model whereby photoexcitation results in the promotion of the molecule into the S2 (1(1)Bu+) state that subsequently undergoes decay to a vibrationally hot S1 (1(1)Ag-) state and with the exception of violaxanthin also to the S* state. The vibrationally hot S1 (1(1)Ag-) state then cools to a vibrationally relaxed S1 (2(1)Ag-) state in less than a picosecond. It was also found that a portion

Time-Resolved Diffuse Optical Spectroscopy and Imaging Using Solid-State Detectors: Characteristics, Present Status, and Research Challenges.

Science.gov (United States)

Alayed, Mrwan; Deen, M Jamal

2017-09-14

Diffuse optical spectroscopy (DOS) and diffuse optical imaging (DOI) are emerging non-invasive imaging modalities that have wide spread potential applications in many fields, particularly for structural and functional imaging in medicine. In this article, we review time-resolved diffuse optical imaging (TR-DOI) systems using solid-state detectors with a special focus on Single-Photon Avalanche Diodes (SPADs) and Silicon Photomultipliers (SiPMs). These TR-DOI systems can be categorized into two types based on the operation mode of the detector (free-running or time-gated). For the TR-DOI prototypes, the physical concepts, main components, figures-of-merit of detectors, and evaluation parameters are described. The performance of TR-DOI prototypes is evaluated according to the parameters used in common protocols to test DOI systems particularly basic instrumental performance (BIP). In addition, the potential features of SPADs and SiPMs to improve TR-DOI systems and expand their applications in the foreseeable future are discussed. Lastly, research challenges and future developments for TR-DOI are discussed for each component in the prototype separately and also for the entire system.

A Resolved and Asymmetric Ring of PAHs within the Young Circumstellar Disk of IRS 48

Energy Technology Data Exchange (ETDEWEB)

Schworer, Guillaume; Lacour, Sylvestre; Du Foresto, Vincent Coudé [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universits, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité (France); Huélamo, Nuria [Dpto. Astrofísica, Centro de Astrobiología (INTA-CSIC), ESAC Campus, P.O. Box 78, E-28691, Villanueva de la Cañada (Spain); Pinte, Christophe; Chauvin, Gaël [Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France CNRS, IPAG, F-38000 Grenoble (France); Ehrenreich, David [Observatoire de l’Université de Genève, 51 chemin des Maillettes, 1290 Versoix (Switzerland); Girard, Julien [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001 Vitacura, Santiago 19 (Chile); Tuthill, Peter [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia)

2017-06-20

For one decade, the spectral type and age of the ρ Oph object IRS-48 were subject to debate and mystery. Modeling its disk with mid-infrared to millimeter observations led to various explanations to account for the complex intricacy of dust holes and gas-depleted regions. We present multi-epoch high-angular-resolution interferometric near-infrared data of spatially resolved emissions in the first 15 au of IRS-48, known to have very strong polycyclic aromatic hydrocarbon (PAH) emissions within this dust-depleted region. We make use of new Sparse-Aperture-Masking data to instruct a revised radiative-transfer model, where spectral energy distribution fluxes and interferometry are jointly fitted. Neutral and ionized PAH, very small grains (VSG), and classical silicates are incorporated into the model; new stellar parameters and extinction laws are explored. A bright (42 L {sub ⊙}) and hence large (2.5 R {sub ⊙}) central star with A {sub v} = 12.5 mag and R {sub v} = 6.5 requires less near-infrared excess: the inner-most disk at ≈1 au is incompatible with the interferometric data. The revised stellar parameters place this system on a 4 Myr evolutionary track, four times younger than the previous estimations, which is in better agreement with the surrounding ρ Oph region and disk-lifetime observations. The disk-structure solution converges to a classical-grain outer disk from 55 au combined with an unsettled and fully resolved VSG and PAH ring, between 11 and 26 au. We find two overluminosities in the PAH ring at color-temperatures consistent with the radiative transfer simulations; one follows a Keplerian circular orbit at 14 au. We show a depletion of a factor of ≈5 of classical dust grains up to 0.3 mm compared to very small particles: the IRS-48 disk is nearly void of dust grains in the first 55 au. A 3.5 M {sub Jup} planet on a 40 au orbit can qualitatively explain the new disk structure.

Catalysis of GTP Hydrolysis by Small GTPases at Atomic Detail by Integration of X-ray Crystallography, Experimental, and Theoretical IR Spectroscopy*

Science.gov (United States)

Rudack, Till; Jenrich, Sarah; Brucker, Sven; Vetter, Ingrid R.; Gerwert, Klaus; Kötting, Carsten

2015-01-01

Small GTPases regulate key processes in cells. Malfunction of their GTPase reaction by mutations is involved in severe diseases. Here, we compare the GTPase reaction of the slower hydrolyzing GTPase Ran with Ras. By combination of time-resolved FTIR difference spectroscopy and QM/MM simulations we elucidate that the Mg2+ coordination by the phosphate groups, which varies largely among the x-ray structures, is the same for Ran and Ras. A new x-ray structure of a Ran·RanBD1 complex with improved resolution confirmed this finding and revealed a general problem with the refinement of Mg2+ in GTPases. The Mg2+ coordination is not responsible for the much slower GTPase reaction of Ran. Instead, the location of the Tyr-39 side chain of Ran between the γ-phosphate and Gln-69 prevents the optimal positioning of the attacking water molecule by the Gln-69 relative to the γ-phosphate. This is confirmed in the RanY39A·RanBD1 crystal structure. The QM/MM simulations provide IR spectra of the catalytic center, which agree very nicely with the experimental ones. The combination of both methods can correlate spectra with structure at atomic detail. For example the FTIR difference spectra of RasA18T and RanT25A mutants show that spectral differences are mainly due to the hydrogen bond of Thr-25 to the α-phosphate in Ran. By integration of x-ray structure analysis, experimental, and theoretical IR spectroscopy the catalytic center of the x-ray structural models are further refined to sub-Å resolution, allowing an improved understanding of catalysis. PMID:26272610

Time-resolved Fourier transform infrared spectrometry using a microfabricated continuous flow mixer: application to protein conformation study using the example of ubiquitin.

Science.gov (United States)

Kakuta, Masaya; Hinsmann, Peter; Manz, Andreas; Lendl, Bernhard

2003-05-01

We report on the use of time-resolved Fourier transform infrared spectroscopy (FT-IR) to study chemically induced conformational changes of proteins using the example of ubiquitin. For this purpose a micromachined mixer is coupled to a conventional IR transmission cell with a pathlength of 25 microm and operated in both the continuous and the stopped-flow mode. This experimental set-up allows the elucidation of reaction pathways in the time frame of about 500 milliseconds to seconds with little reagent consumption and low pressure. For continuous flow measurements employed in the time frame from 0.5 to 1.4 s the reaction time is determined by the flow rate used as the connection between the point of confluence in the micromixer and the flow cell was kept constant in all experiments. For stopped-flow experiments (>1.4 s) the time is determined by data acquisition of the rapid scanning infrared spectrometer. Ubiquitin, a small well-known protein with 76 amino acid residues, changes its conformation from native to A-state with the addition of methanol under low pH conditions. We investigated the conformational change in the time frame from 0.5 to 10 s by mixing ubiquitin (20% methanol-d(4)) with an 80% methanol-d(4) solution at pD 2 by evaluating the time dependent changes in the amide I band of the protein.

Sensitivity Analysis and Requirements for Temporally and Spatially Resolved Thermometry Using Neutron Resonance Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Fernandez, Juan Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Barnes, Cris William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mocko, Michael Jeffrey [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Zavorka, Lukas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2018-01-31

This report is intended to examine the use of neutron resonance spectroscopy (NRS) to make time- dependent and spatially-resolved temperature measurements of materials in extreme conditions. Specifically, the sensitivities of the temperature estimate on neutron-beam and diagnostic parameters is examined. Based on that examination, requirements are set on a pulsed neutron-source and diagnostics to make a meaningful measurement.

Time resolved FTIR study of the catalytic CO oxidation under periodic variation of the reactant concentration

Energy Technology Data Exchange (ETDEWEB)

Kritzenberger, J; Wokaun, A [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Oxidation of CO over palladium/zirconia catalyst obtained from an amorphous Pd{sub 25}Zr{sub 75} precursor was investigated by time resolved FTIR spectroscopy. Sine wave shaped modulation of the reactant concentration, i.e. variation of CO or O{sub 2} partial pressure, was used to induce variations of the IR signals of product (CO{sub 2}) and unconverted reactant (CO), which were detected in a multi-pass absorption cell. The phase shift {phi} between external perturbation and variation of the CO{sub 2} signal was examined in dependence on temperature (100{sup o}C{<=}T{<=}350{sup o}C) and modulation frequency (1.39x10{sup -4}Hz{<=}{omega}{<=}6.67x10{sup -2}Hz). From the phase shift values, a simple Eley-Rideal mechanism is excluded, and the rate limiting step of the Langmuir-Hinshelwood mechanism for the CO oxidation may be identified. Adsorption and possible surface movement of CO to the actual reaction site determine the rate of the CO oxidation on the palladium/zirconia catalyst used in our study. The introduction of an external perturbation is a first step towards the application of two-dimensional infrared spectroscopy to heterogeneous catalyzed reactions. (author) 3 figs., 4 refs.

Probing Gas Adsorption in Zeolites by Variable-Temperature IR Spectroscopy: An Overview of Current Research.

Science.gov (United States)

Garrone, Edoardo; Delgado, Montserrat R; Bonelli, Barbara; Arean, Carlos O

2017-09-15

The current state of the art in the application of variable-temperature IR (VTIR) spectroscopy to the study of (i) adsorption sites in zeolites, including dual cation sites; (ii) the structure of adsorption complexes and (iii) gas-solid interaction energy is reviewed. The main focus is placed on the potential use of zeolites for gas separation, purification and transport, but possible extension to the field of heterogeneous catalysis is also envisaged. A critical comparison with classical IR spectroscopy and adsorption calorimetry shows that the main merits of VTIR spectroscopy are (i) its ability to provide simultaneously the spectroscopic signature of the adsorption complex and the standard enthalpy change involved in the adsorption process; and (ii) the enhanced potential of VTIR to be site specific in favorable cases.

Solid Acid-Catalyzed Cellulose Hydrolysis Monitored by In Situ ATR-IR Spectroscopy

NARCIS (Netherlands)

Zakzeski, J.; Grisel, R.J.H.; Smit, A.T.; Weckhuysen, B.M.

2012-01-01

The solid acid-catalyzed hydrolysis of cellulose was studied under elevated temperatures and autogenous pressures using in situ ATR-IR spectroscopy. Standards of cellulose and pure reaction products, which include glucose, fructose, hydroxymethylfurfural (HMF), levulinic acid (LA), formic acid, and

Structure in nascent carbon nanotubes revealed by spatially resolved Raman spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Landois, Périne [CEA, IRAMIS, SPAM, Laboratoire Francis Perrin (CNRS URA 2453), 91191 Gif-sur-Yvette (France); Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris Sud 11, 91405 Orsay (France); Pinault, Mathieu [CEA, IRAMIS, SPAM, Laboratoire Francis Perrin (CNRS URA 2453), 91191 Gif-sur-Yvette (France); Huard, Mickaël [Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris Sud 11, 91405 Orsay (France); Reita, Valérie [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Rouzière, Stéphan; Launois, Pascale [Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris Sud 11, 91405 Orsay (France); Mayne-L' Hermite, Martine [CEA, IRAMIS, SPAM, Laboratoire Francis Perrin (CNRS URA 2453), 91191 Gif-sur-Yvette (France); Bendiab, Nedjma, E-mail: nedjma.bendiab@grenoble.cnrs.fr [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France)

2014-10-01

The understanding of carbon nanotube (CNT) growth is crucial for the control of their production. In particular, the identification of structural changes of carbon possibly occurring near the catalyst particle in the very early stages of their formation is of high interest. In this study, samples of nascent CNT obtained during nucleation step and samples of vertically aligned CNT obtained during growth step are analysed by combined spatially resolved Raman spectroscopy and X-ray diffraction measurements. Spatially resolved Raman spectroscopy reveals that iron-based phases and carbon phases are co-localized at the same position, and indicates that sp{sup 2} carbon nucleates preferentially on iron-based particles during this nucleation step. Depth scan Raman spectroscopy analysis, performed on nascent CNT, highlights that carbon structural organisation is significantly changing from defective graphene layers surrounding the iron-based particles at their base up to multi-walled nanotube structures in the upper part of iron-based particles. - Highlights: • Spatial co-localization of iron and carbon structures in nascent carbon nanotubes • Imaging local carbon structure changes along catalyst particles by Raman spectroscopy. • In nascent nanotubes, significant structural changes occur along catalyst particle.

Time-resolved far-infrared experiments at the National Synchrotron Light Source. Final report

International Nuclear Information System (INIS)

Tanner, D.B.; Reitze, D.H.; Carr, G.L.

1999-01-01

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 -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

The characterization of natural gemstones using non-invasive FT-IR spectroscopy: New data on tourmalines.

Science.gov (United States)

Mercurio, Mariano; Rossi, Manuela; Izzo, Francesco; Cappelletti, Piergiulio; Germinario, Chiara; Grifa, Celestino; Petrelli, Maurizio; Vergara, Alessandro; Langella, Alessio

2018-02-01

Fourteen samples of tourmaline from the Real Museo Mineralogico of Federico II University (Naples) have been characterized through multi-methodological investigations (EMPA-WDS, SEM-EDS, LA-ICP-MS, and FT-IR spectroscopy). The samples show different size, morphology and color, and are often associated with other minerals. Data on major and minor elements allowed to identify and classify tourmalines as follows: elbaites, tsilaisite, schorl, dravites, uvites and rossmanite. Non-invasive, non-destructive FT-IR and in-situ analyses were carried out on the same samples to validate this chemically-based identification and classification. The results of this research show that a complete characterization of this mineral species, usually time-consuming and expensive, can be successfully achieved through non-destructive FT-IR technique, thus representing a reliable tool for a fast classification extremely useful to plan further analytical strategies, as well as to support gemological appraisals. Copyright © 2017 Elsevier B.V. All rights reserved.

DFT and time-resolved IR investigation of electron transfer between photogenerated 17- and 19-electron organometallic radicals

Energy Technology Data Exchange (ETDEWEB)

Cahoon, James B.; Kling, Matthias F.; Sawyer, Karma R.; Andersen, Lars K.; Harris, Charles B.

2008-04-30

The photochemical disproportionation mechanism of [CpW(CO){sub 3}]{sub 2} in the presence of Lewis bases PR{sub 3} was investigated on the nano- and microsecond time-scales with Step-Scan FTIR time-resolved infrared spectroscopy. 532 nm laser excitation was used to homolytically cleave the W-W bond, forming the 17-electron radicals CpW(CO){sub 3} and initiating the reaction. With the Lewis base PPh{sub 3}, disproportionation to form the ionic products CpW(CO){sub 3}PPh{sub 3}{sup +} and CpW(CO){sub 3}{sup -} was directly monitored on the microsecond time-scale. Detailed examination of the kinetics and concentration dependence of this reaction indicates that disproportionation proceeds by electron transfer from the 19-electron species CpW(CO){sub 3}PPh{sub 3} to the 17-electron species CpW(CO){sub 3}. This result is contrary to the currently accepted disproportionation mechanism which predicts electron transfer from the 19-electron species to the dimer [CpW(CO){sub 3}]{sub 2}. With the Lewis base P(OMe){sub 3} on the other hand, ligand substitution to form the product [CpW(CO){sub 2}P(OMe){sub 3}]{sub 2} is the primary reaction on the microsecond time-scale. Density Functional Theory (DFT) calculations support the experimental results and suggest that the differences in the reactivity between P(OMe){sub 3} and PPh{sub 3} are due to steric effects. The results indicate that radical-to-radical electron transfer is a previously unknown but important process for the formation of ionic products with the organometallic dimer [CpW(CO){sub 3}]{sub 2} and may also be applicable to the entire class of organometallic dimers containing a single metal-metal bond.

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.

Experimental bandstructure of the 5 d transition metal oxide IrO2

Science.gov (United States)

Kawasaki, Jason; Nie, Yuefeng; Uchida, Masaki; Schlom, Darrell; Shen, Kyle

2015-03-01

In the 5 d iridium oxides the close energy scales of spin-orbit coupling and electron-electron correlations lead to emergent quantum phenomena. Much research has focused on the ternary iridium oxides, e.g. the Ruddlesden-Poppers An + 1BnO3 n + 1 , which exhibit behavior from metal to antiferromagnetic insulator ground states, share common features with the cuprates, and may host a number of topological phases. The binary rutile IrO2 is another important 5 d oxide, which has technological importance for spintronics due to its large spin Hall effect and also applications in catalysis. IrO2 is expected to share similar physics as its perovskite-based cousins; however, due to bond-length distortions of the IrO6 octahedra in the rutile structure, the extent of similarities remains an open question. Here we use angle-resolved photoemission spectroscopy to perform momentum-resolved measurements of the electronic structure of IrO2 . IrO2 thin films were grown by molecular beam epitaxy on TiO2 (110) substrates using an Ir e-beam source and distilled ozone. Films were subsequently transferred through ultrahigh vacuum to a connected ARPES system. Combined with first-principles calculations we explore the interplay of spin-orbit coupling and correlations in IrO2 .

Mesoporous silica nanoparticle supported PdIr bimetal catalyst for selective hydrogenation, and the significant promotional effect of Ir

Energy Technology Data Exchange (ETDEWEB)

Yang, Hui; Huang, Chao; Yang, Fan [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Yang, Xu [Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Du, Li [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Liao, Shijun, E-mail: chsjliao@scut.edu.cn [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China)

2015-12-01

Graphical abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction caused by the addition of Ir. - Highlights: • Mesoporous nanoparticles were synthesized and used as support for metal catalyst. • PdIr bimetallic catalyst exhibited significantly improved hydrogenation activity. • The strong promotion of Ir was recognized firstly and investigated intensively. • PdIr exhibits 18 times higher activity than Pd to the hydrogenation of nitrobenzene. - Abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction

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

Energy Technology Data Exchange (ETDEWEB)

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

2007-09-21

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

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

International Nuclear Information System (INIS)

Radu, L.; Mihailescu, I.; Radu, S.; Gazdaru, D.

2007-01-01

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

Time resolved techniques: An overview

International Nuclear Information System (INIS)

Larson, B.C.; Tischler, J.Z.

1990-06-01

Synchrotron sources provide exceptional opportunities for carrying out time-resolved x-ray diffraction investigations. The high intensity, high angular resolution, and continuously tunable energy spectrum of synchrotron x-ray beams lend themselves directly to carrying out sophisticated time-resolved x-ray scattering measurements on a wide range of materials and phenomena. When these attributes are coupled with the pulsed time-structure of synchrotron sources, entirely new time-resolved scattering possibilities are opened. Synchrotron beams typically consist of sub-nanosecond pulses of x-rays separated in time by a few tens of nanoseconds to a few hundred nanoseconds so that these beams appear as continuous x-ray sources for investigations of phenomena on time scales ranging from hours down to microseconds. Studies requiring time-resolution ranging from microseconds to fractions of a nanosecond can be carried out in a triggering mode by stimulating the phenomena under investigation in coincidence with the x-ray pulses. Time resolution on the picosecond scale can, in principle, be achieved through the use of streak camera techniques in which the time structure of the individual x-ray pulses are viewed as quasi-continuous sources with ∼100--200 picoseconds duration. Techniques for carrying out time-resolved scattering measurements on time scales varying from picoseconds to kiloseconds at present and proposed synchrotron sources are discussed and examples of time-resolved studies are cited. 17 refs., 8 figs

Energy- and angled-resolved photoelectron spectroscopy of negative ions

International Nuclear Information System (INIS)

Pegg, D.J.; Thompson, J.S.; Compton, R.N.; Alton, G.D.

1988-01-01

Energy- and angle-resolved photoelectron detachment spectroscopy is currently being used to investigate the structure of negative ions and their interaction with radiation. Measurements of the electron affinity of the Ca atom and the partial cross sections for photodetachment of the metastable negative ion, He - (1s2s2p 4 P), are reported. 5 refs., 5 figs

Fourier Transform Infrared Spectroscopy (FT-IR) and Simple Algorithm Analysis for Rapid and Non-Destructive Assessment of Developmental Cotton Fibers.

Science.gov (United States)

Liu, Yongliang; Kim, Hee-Jin

2017-06-22

With cotton fiber growth or maturation, cellulose content in cotton fibers markedly increases. Traditional chemical methods have been developed to determine cellulose content, but it is time-consuming and labor-intensive, mostly owing to the slow hydrolysis process of fiber cellulose components. As one approach, the attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy technique has also been utilized to monitor cotton cellulose formation, by implementing various spectral interpretation strategies of both multivariate principal component analysis (PCA) and 1-, 2- or 3-band/-variable intensity or intensity ratios. The main objective of this study was to compare the correlations between cellulose content determined by chemical analysis and ATR FT-IR spectral indices acquired by the reported procedures, among developmental Texas Marker-1 (TM-1) and immature fiber ( im ) mutant cotton fibers. It was observed that the R value, CI IR , and the integrated intensity of the 895 cm -1 band exhibited strong and linear relationships with cellulose content. The results have demonstrated the suitability and utility of ATR FT-IR spectroscopy, combined with a simple algorithm analysis, in assessing cotton fiber cellulose content, maturity, and crystallinity in a manner which is rapid, routine, and non-destructive.

Fingerprinting DNA oxidation processes: IR characterization of the 5-methyl-2'-deoxycytidine radical cation.

Science.gov (United States)

Bucher, Dominik B; Pilles, Bert M; Pfaffeneder, Toni; Carell, Thomas; Zinth, Wolfgang

2014-02-24

Methylated cytidine plays an important role as an epigenetic signal in gene regulation. Its oxidation products are assumed to be involved in active demethylation processes but also in damaging DNA. Here, we report the photochemical production of the 5-methyl-2'-deoxycytidine radical cation via a two-photon ionization process. The radical cation is detected by time-resolved IR spectroscopy and identified by band assignment using density functional theory calculations. Two final oxidation products are characterized with liquid chromatography coupled to mass spectrometry. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Femtosecond time-resolved transient absorption spectroscopy of xanthophylls

Czech Academy of Sciences Publication Activity Database

Niedzwiedzki, D.; Sullivan, J.O.; Polívka, Tomáš; Birge, R.R.; Frank, H.A.

2006-01-01

Roč. 110, č. 45 (2006), s. 22872-22885 ISSN 1520-6106 Institutional research plan: CEZ:AV0Z50510513 Keywords : xanthophyll * spectroscopy study Subject RIV: BO - Biophysics Impact factor: 4.115, year: 2006

IR spectroscopy at the ITO-organic interface

Energy Technology Data Exchange (ETDEWEB)

Alt, Milan [Karlsruher Institut fuer Technologie, Karlsruhe (Germany); Shazada, Ahmad [Max-Planck Institut fuer Polymerforschung, Mainz (Germany); Tamanai, Akemi; Trollmann, Jens; Glaser, Tobias; Beck, Sebastian; Tengeler, Sven; Pucci, Annemarie [Kirchhoff-Institut fuer Physik, Heidelberg (Germany)

2012-07-01

Thin films of P3HT have been prepared by spin coating and electrooxidative polymerization on platinum- and ITO-coated substrates. Additionally, P3HT-films on silicon substrates have been prepared by spin coating only. The measured IR spectra of the spin coated films allowed for an elaboration of a detailed optical model for P3HT, which has been used to simulate IR reflection-absorption spectra on ITO and Pt substrates. Comparison of simulated spectra with measurements revealed no substrate influence on the IR spectra for the spincoated films. In case of spincoated P3HT-films on ITO-substrate, the obtained IR spectra correspond to simulation data very well up to 6000 wavenumbers. In the electropolymerized P3HT films we have identified residuals of the electrolyte ionic liquid, acting as dopand for P3HT. While IR spectra of the electropolymerized P3HT films on Pt substrate could be explained reasonably well as a superposition of chemically doped P3HT and the ionic electrolyte, the IR spectra of electropolymerized P3HT films on ITO substrates showed strongly deposition-time dependent deviations. These were most likely related to varying properties of the ITO surface between reference and sample measurement due to an interaction of ITO and the electrolyte at the film-substrate interface.

IR-IR Conformation Specific Spectroscopy of Na+(Glucose) Adducts

Science.gov (United States)

Voss, Jonathan M.; Kregel, Steven J.; Fischer, Kaitlyn C.; Garand, Etienne

2018-01-01

We report an IR-IR double resonance study of the structural landscape present in the Na+(glucose) complex. Our experimental approach involves minimal modifications to a typical IR predissociation setup, and can be carried out via ion-dip or isomer-burning methods, providing additional flexibility to suit different experimental needs. In the current study, the single-laser IR predissociation spectrum of Na+(glucose), which clearly indicates contributions from multiple structures, was experimentally disentangled to reveal the presence of three α-conformers and five β-conformers. Comparisons with calculations show that these eight conformations correspond to the lowest energy gas-phase structures with distinctive Na+ coordination. [Figure not available: see fulltext.

Application of Fourier transform infrared (FT-IR) spectroscopy in determination of microalgal compositions.

Science.gov (United States)

Meng, Yingying; Yao, Changhong; Xue, Song; Yang, Haibo

2014-01-01

Fourier transform infrared spectroscopy (FT-IR) was applied in algal strain screening and monitoring cell composition dynamics in a marine microalga Isochrysis zhangjiangensis during algal cultivation. The content of lipid, carbohydrate and protein of samples determined by traditional methods had validated the accuracy of FT-IR method. For algal screening, the band absorption ratios of lipid/amide I and carbo/amide I from FT-IR measurements allowed for the selection of Isochrysis sp. and Tetraselmis subcordiformis as the most potential lipid and carbohydrate producers, respectively. The cell composition dynamics of I. zhangjiangensis measured by FT-IR revealed the diversion of carbon allocation from protein to carbohydrate and neutral lipid when nitrogen-replete cells were subjected to nitrogen limitation. The carbo/amide I band absorption ratio had also been demonstrated to depict physiological status under nutrient stress in T. subcordiformis. FT-IR serves as a tool for the simultaneous measurement of lipid, carbohydrate, and protein content in cell. Copyright © 2013 Elsevier Ltd. All rights reserved.

Hemodynamic measurements in deep brain tissues of humans by near-infrared time-resolved spectroscopy

Science.gov (United States)

Suzuki, Hiroaki; Oda, Motoki; Yamaki, Etsuko; Suzuki, Toshihiko; Yamashita, Daisuke; Yoshimoto, Kenji; Homma, Shu; Yamashita, Yutaka

2014-03-01

Using near-infrared time-resolved spectroscopy (TRS), we measured the human head in transmittance mode to obtain the optical properties, tissue oxygenation, and hemodynamics of deep brain tissues in 50 healthy adult volunteers. The right ear canal was irradiated with 3-wavelengths of pulsed light (760, 795, and 835nm), and the photons passing through the human head were collected at the left ear canal. Optical signals with sufficient intensity could be obtained from 46 of the 50 volunteers. By analyzing the temporal profiles based on the photon diffusion theory, we successfully obtained absorption coefficients for each wavelength. The levels of oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), total hemoglobin (tHb), and tissue oxygen saturation (SO2) were then determined by referring to the hemoglobin spectroscopic data. Compared with the SO2 values for the forehead measurements in reflectance mode, the SO2 values of the transmittance measurements of the human head were approximately 10% lower, and tHb values of the transmittance measurements were always lower than those of the forehead reflectance measurements. Moreover, the level of hemoglobin and the SO2 were strongly correlated between the human head measurements in transmittance mode and the forehead measurements in the reflectance mode, respectively. These results demonstrated a potential application of this TRS system in examining deep brain tissues of humans.

Catalysis of GTP hydrolysis by small GTPases at atomic detail by integration of X-ray crystallography, experimental, and theoretical IR spectroscopy.

Science.gov (United States)

Rudack, Till; Jenrich, Sarah; Brucker, Sven; Vetter, Ingrid R; Gerwert, Klaus; Kötting, Carsten

2015-10-02

Small GTPases regulate key processes in cells. Malfunction of their GTPase reaction by mutations is involved in severe diseases. Here, we compare the GTPase reaction of the slower hydrolyzing GTPase Ran with Ras. By combination of time-resolved FTIR difference spectroscopy and QM/MM simulations we elucidate that the Mg(2+) coordination by the phosphate groups, which varies largely among the x-ray structures, is the same for Ran and Ras. A new x-ray structure of a Ran·RanBD1 complex with improved resolution confirmed this finding and revealed a general problem with the refinement of Mg(2+) in GTPases. The Mg(2+) coordination is not responsible for the much slower GTPase reaction of Ran. Instead, the location of the Tyr-39 side chain of Ran between the γ-phosphate and Gln-69 prevents the optimal positioning of the attacking water molecule by the Gln-69 relative to the γ-phosphate. This is confirmed in the RanY39A·RanBD1 crystal structure. The QM/MM simulations provide IR spectra of the catalytic center, which agree very nicely with the experimental ones. The combination of both methods can correlate spectra with structure at atomic detail. For example the FTIR difference spectra of RasA18T and RanT25A mutants show that spectral differences are mainly due to the hydrogen bond of Thr-25 to the α-phosphate in Ran. By integration of x-ray structure analysis, experimental, and theoretical IR spectroscopy the catalytic center of the x-ray structural models are further refined to sub-Å resolution, allowing an improved understanding of catalysis. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

The TApIR experiment. IR absorption spectra of liquid hydrogen isotopologues; Das TApIR Experiment IR-Absorptionsspektren fluessiger Wasserstoffisotopologe

Energy Technology Data Exchange (ETDEWEB)

Groessle, Robin

2015-11-27

The scope of the thesis is the infrared absorption spectroscopy of liquid hydrogen isotopologues with the tritium absorption infrared spectroscopy (TApIR) experiment at the tritium laboratory Karlsruhe (TLK). The calibration process from the sample preparation to the reference measurements are described. A further issue is the classical evaluation of FTIR absorption spectra and the extension using the rolling circle filter (RCF) including the effects on statistical and systematical errors. The impact of thermal and nuclear spin temperature on the IR absorption spectra is discussed. An empirical based modeling for the IR absorption spectra of liquid hydrogen isotopologues is performed.

Direct Structural and Chemical Characterization of the Photolytic Intermediates of Methylcobalamin Using Time-Resolved X-ray Absorption Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Subramanian, Ganesh; Zhang, Xiaoyi; Kodis, Gerdenis; Kong, Qingyu; Liu, Cunming; Chizmeshya, Andrew; Weierstall, Uwe; Spence, John

2018-04-05

Cobalt−carbon bond cleavage is crucial to most natural and synthetic applications of the cobalamin class of compounds, and here we present the first direct electronic and geometric structural characteristics of intermediates formed following photoexcitation of methylcobalamin (MeCbl) using time-resolved X-ray absorption spectroscopy (XAS). We catch transients corresponding to two intermediates, in the hundreds of picoseconds and a few microseconds. Highlights of the picosecond intermediate, which is reduced in comparison to the ground state, are elongation of the upper axial Co−C bond and relaxation of the corrin ring. This is not so with the recombining photocleaved products captured at a few microseconds, where the Co−C bond almost (yet not entirely) reverts to its ground state configuration and a substantially elongated lower axial Co−NIm bond is observed. The reduced cobalt site here confirms formation of methyl radical as the photoproduct.

Investigations of lateral and vertical compositional gradients in Cu(In,Ga)Se{sub 2} by highly spatially, spectrally and time resolved cathodoluminescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Mueller, Mathias; Ribbe, Stefan; Hempel, Thomas; Bertram, Frank; Christen, Juergen [Institute for Experimental Physics, Otto-von-Guericke-University, Magdeburg (Germany); Witte, Wolfram; Hariskos, Dimitrios [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), Stuttgart (Germany)

2011-07-01

Luminescence properties of Cu(In,Ga)Se{sub 2} (CIGS) layers with different thicknesses were investigated by means of highly spatially, spectrally and time resolved cathodoluminescence (CL) spectroscopy at low temperature (T=5 K). A polycrystalline CIGS thin film with a thickness of 2.4 {mu}m was grown using an in-line co-evaporation process with a final Cu-poor composition on top of a sputtered Mo layer on a soda lime glass substrate. The layer thickness was then reduced by highly controlled bromine methanol etching. The typical grainy (d{sub average}=3 {mu}m) structure of the untouched sample develops thin longish structures under the influence of the etchant. Integral CL spectra of the samples are dominated by donor-acceptor pair (DAP) luminescence. The peak energies of these spectra are ranging from 1.13 eV to 1.22 eV with decreasing layer thickness. The lateral distribution of the luminescence is inhomogeneous regarding the intensity as well as the peak energy. Time resolved CL shows a strong dependence of the initial lifetime from the emission energy.

Effect of Water on HEMA Conversion by FT-IR Spectroscopy

Directory of Open Access Journals (Sweden)

TS. Jafarzadeh Kashi

2007-09-01

Full Text Available Objective: The use of HEMA as a biocompatible material in dentin bonding systems and its potential for clinical applications has been well established. Excess water can affect conversion of bonding resins. The aim of this study was to survey the effect of water on the degree of conversion of HEMA by Fourier Transform Infra-red Spectroscopy (FT-IR.Materials and Methods: In this experimental study, distilled water was added in amounts of 0, 0.05, 0.1, 0.2, and 0.4 ml to 1 ml of curable HEMA solution. Six repetitions per wa-ter ratio were made and investigated. Each sample was polymerized for 60 seconds. De-gree of conversion was obtained from the absorbance IR-Spectrum of the materials before and after polymerization by FT-IR spectroscopy. One way ANOVA and Tukey-HSD were carried out to compare and detect any differences among groups.Results: Statistical analysis indicates highly significant difference between pairs of groups at level (P<0.001. The results showed a trend of decreasing in HEMA conversion with increasing water. Degree of conversion changes significantly within the 0.05 ml to 0.2 ml water range. However, degree of conversion did not change after reaching 0.02 ml and before 0.05.Conclusion: Degree of conversion of HEMA decreased by increasing water. The most dramatic effect of water on the polymerization process occurs within a range which exists under clinical conditions. The reason that the degree of conversion did not show signifi-cant result before 0.05 ml may be related to the hydrophilic nature of HEMA.

Time-Resolved Synchronous Fluorescence for Biomedical Diagnosis

Science.gov (United States)

Zhang, Xiaofeng; Fales, Andrew; Vo-Dinh, Tuan

2015-01-01

This article presents our most recent advances in synchronous fluorescence (SF) methodology for biomedical diagnostics. The SF method is characterized by simultaneously scanning both the excitation and emission wavelengths while keeping a constant wavelength interval between them. Compared to conventional fluorescence spectroscopy, the SF method simplifies the emission spectrum while enabling greater selectivity, and has been successfully used to detect subtle differences in the fluorescence emission signatures of biochemical species in cells and tissues. The SF method can be used in imaging to analyze dysplastic cells in vitro and tissue in vivo. Based on the SF method, here we demonstrate the feasibility of a time-resolved synchronous fluorescence (TRSF) method, which incorporates the intrinsic fluorescent decay characteristics of the fluorophores. Our prototype TRSF system has clearly shown its advantage in spectro-temporal separation of the fluorophores that were otherwise difficult to spectrally separate in SF spectroscopy. We envision that our previously-tested SF imaging and the newly-developed TRSF methods will combine their proven diagnostic potentials in cancer diagnosis to further improve the efficacy of SF-based biomedical diagnostics. PMID:26404289

Time-resolved laser fluorescence spectroscopy of organic ligands by europium: Fluorescence quenching and lifetime properties

Science.gov (United States)

Nouhi, A.; Hajjoul, H.; Redon, R.; Gagné, J. P.; Mounier, S.

2018-03-01

Time-resolved Laser Fluorescence Spectroscopy (TRLFS) has proved its usefulness in the fields of biophysics, life science and geochemistry to characterize the fluorescence probe molecule with its chemical environment. The purpose of this study is to demonstrate the applicability of this powerful technique combined with Steady-State (S-S) measurements. A multi-mode factor analysis, in particular CP/PARAFAC, was used to analyze the interaction between Europium (Eu) and Humic substances (HSs) extracted from Saint Lawrence Estuary in Canada. The Saint Lawrence system is a semi-enclosed water stream with connections to the Atlantic Ocean and is an excellent natural laboratory. CP/PARAFAC applied to fluorescence S-S data allows introspecting ligands-metal interactions and the one-site 1:1 modeling gives information about the stability constants. From the spectral signatures and decay lifetimes data given by TRLFS, one can deduce the fluorescence quenching which modifies the fluorescence and discuss its mechanisms. Results indicated a relatively strong binding ability between europium and humic substances samples (Log K value varies from 3.38 to 5.08 at pH 7.00). Using the Stern-Volmer plot, it has been concluded that static and dynamic quenching takes places in the case of salicylic acid and europium interaction while for HSs interaction only a static quenching is observed.

Rapid identification of Pterocarpus santalinus and Dalbergia louvelii by FTIR and 2D correlation IR spectroscopy

Science.gov (United States)

Zhang, Fang-Da; Xu, Chang-Hua; Li, Ming-Yu; Huang, An-Min; Sun, Su-Qin

2014-07-01

Since Pterocarpus santalinus and Dalbergia louvelii, which are of precious Rosewood, are very similar in their appearance and anatomy characteristics, cheaper Hongmu D. louvelii is often illegally used to impersonate valuable P. santalinus, especially in Chinese furniture manufacture. In order to develop a rapid and effective method for easy confused wood furniture differentiation, we applied tri-step identification method, i.e., conventional infrared spectroscopy (FT-IR), second derivative infrared (SD-IR) spectroscopy and two-dimensional correlation infrared (2DCOS-IR) spectroscopy to investigate P. santalinus and D. louvelii furniture. According to FT-IR and SD-IR spectra, it has been found two unconditional stable difference at 848 cm-1 and 700 cm-1 and relative stable differences at 1735 cm-1, 1623 cm-1, 1614 cm-1, 1602 cm-1, 1509 cm-1, 1456 cm-1, 1200 cm-1, 1158 cm-1, 1055 cm-1, 1034 cm-1 and 895 cm-1 between D. louvelii and P. santalinus IR spectra. The stable discrepancy indicates that the category of extractives is different between the two species. Besides, the relative stable differences imply that the content of holocellulose in P. santalinus is more than that of D. louvelii, whereas the quantity of extractives in D. louvelii is higher. Furthermore, evident differences have been observed in their 2DCOS-IR spectra of 1550-1415 cm-1 and 1325-1030 cm-1. P. santalinus has two strong auto-peaks at 1459 cm-1 and 1467 cm-1, three mid-strong auto-peaks at 1518 cm-1, 1089 cm-1 and 1100 cm-1 and five weak auto-peaks at 1432 cm-1, 1437 cm-1, 1046 cm-1, 1056 cm-1 and 1307 cm-1 while D. louvelii has four strong auto-peaks at 1465 cm-1, 1523 cm-1, 1084 cm-1 and 1100 cm-1, four mid-strong auto-peaks at 1430 cm-1, 1499 cm-1, 1505 cm-1 and 1056 cm-1 and two auto-peaks at 1540 cm-1 and 1284 cm-1. This study has proved that FT-IR integrated with 2DCOS-IR could be applicable for precious wood furniture authentication in a direct, rapid and holistic manner.

Robustness of the charge-ordered phases in IrTe2 against photoexcitation

Science.gov (United States)

Monney, C.; Schuler, A.; Jaouen, T.; Mottas, M.-L.; Wolf, Th.; Merz, M.; Muntwiler, M.; Castiglioni, L.; Aebi, P.; Weber, F.; Hengsberger, M.

2018-02-01

We present a time-resolved angle-resolved photoelectron spectroscopy study of IrTe2, which undergoes two first-order structural and charge-ordered phase transitions on cooling below 270 K and below 180 K. The possibility of inducing a phase transition by photoexcitation with near-infrared femtosecond pulses is investigated in the charge-ordered phases. We observe changes of the spectral function occurring within a few hundreds of femtoseconds and persisting up to several picoseconds, which we interpret as a partial photoinduced phase transition (PIPT). The necessary time for photoinducing these spectral changes increases with increasing photoexcitation density and reaches time scales longer than the rise time of the transient electronic temperature. We conclude that the PIPT is driven by a transient increase of the lattice temperature following the energy transfer from the electrons. However, the photoinduced changes of the spectral function are small, which indicates that the low-temperature phase is particularly robust against photoexcitation. We suggest that the system might be trapped in an out-of-equilibrium state, for which only a partial structural transition is achieved.

Phase-Sensitive Control Of Molecular Dissociation Through Attosecond Pump/Strong-Field Mid-IR Probe Spectroscopy

Science.gov (United States)

2016-04-15

splitter (consisting of a thin, uncoated, silicon plate at brewsters angle) and the beams were focused onto the OPA crystal. For this work two...experiments in the future. These technologies include • Two-color driven (EUV/mid-IR) ion spectroscopy: we designed an interferometer combining EUV...isolated single-femtosecond EUV pulse generation: combining the use of low ionization threshold gas, an annual near-IR drive beam , polarization

Kinetics of methane-ethane gas replacement in clathrate-hydrates studied by time-resolved neutron diffraction and Raman spectroscopy.

Science.gov (United States)

Murshed, M Mangir; Schmidt, Burkhard C; Kuhs, Werner F

2010-01-14

The kinetics of CH(4)-C(2)H(6) replacement in gas hydrates has been studied by in situ neutron diffraction and Raman spectroscopy. Deuterated ethane structure type I (C(2)H(6) sI) hydrates were transformed in a closed volume into methane-ethane mixed structure type II (CH(4)-C(2)H(6) sII) hydrates at 5 MPa and various temperatures in the vicinity of 0 degrees C while followed by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. The role of available surface area of the sI starting material on the formation kinetics of sII hydrates was studied. Ex situ Raman spectroscopic investigations were carried out to crosscheck the gas composition and the distribution of the gas species over the cages as a function of structure type and compared to the in situ neutron results. Raman micromapping on single hydrate grains showed compositional and structural gradients between the surface and core of the transformed hydrates. Moreover, the observed methane-ethane ratio is very far from the one expected for a formation from a constantly equilibrated gas phase. The results also prove that gas replacement in CH(4)-C(2)H(6) hydrates is a regrowth process involving the nucleation of new crystallites commencing at the surface of the parent C(2)H(6) sI hydrate with a progressively shrinking core of unreacted material. The time-resolved neutron diffraction results clearly indicate an increasing diffusion limitation of the exchange process. This diffusion limitation leads to a progressive slowing down of the exchange reaction and is likely to be responsible for the incomplete exchange of the gases.

Luminescent chiral ionic Ir(III) complexes: Synthesis and photophysical properties

Energy Technology Data Exchange (ETDEWEB)

Ricciardi, Loredana, E-mail: loredana.ricciardi@unical.it [CNR NANOTEC-Istituto di Nanotecnologia U.O.S. Cosenza, 87036 Arcavacata di Rende (CS) (Italy); La Deda, Massimo; Ionescu, Andreea; Godbert, Nicolas; Aiello, Iolinda; Ghedini, Mauro [MAT-INLAB (Laboratorio di Materiali Molecolari Inorganici), LASCAMM and CR INSTM, Unità INSTM della Calabria, Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, 87036 Arcavacata di Rende (CS) (Italy); Fusè, Marco, E-mail: marco.fuse@unimi.it [Dipartimento di Scienze Farmaceutiche, Università di Milano, Via Golgi 19, 20133 Milano (Italy); Rimoldi, Isabella; Cesarotti, Edoardo [Dipartimento di Scienze Farmaceutiche, Università di Milano, Via Golgi 19, 20133 Milano (Italy)

2016-02-15

Three homologous series of luminescent octahedral ionic Ir(III) complexes (1–12) with a dual stereogenic center of general formula {sup Δ,Λ} {sup (R,S)}[(ppy){sub 2}Ir(R-campy)]X, where ppy=2-phenylpyridine, R-campy=2-methyl-5,6,7,8-tetrahydroquinolin-8-amine (Me-campy) or 8-amino-5,6,7,8-tetrahydroquinolines (H-campy) and as counterions X{sup −}=Cl{sup −} or CH{sub 3}COO{sup −} have been synthesized and characterized. The NMR characterization of each complex highlighted the diastereoisomeric purity and the absolute configuration has been confirmed by Electronic Circular Dichroism spectroscopy. The absorption and the luminescence properties of the compounds in solution and in solid state have been investigated by UV–vis, steady-state emission and time-correlated single-photon counting spectroscopy. The obtained results from the 12 compounds highlight the difficult to correlate photophysical properties in solution to the stereochemistry, while excited states decay studies of the solid state samples indicate a correlation between photophysics and packing mode which is affected by the different stereochemistry. - Highlights: • Luminescent chiral ionic Ir(III) complexes have been synthesized and characterized. • Presence in the same structure of two stereogenic centers. • Use of camphorsulfonate as resolving anion to obtain enantiomerically pure samples. • Stereoisomers produce aggregates with different emitting properties. • Lifetimes from solid samples show the presence of AIPE.

The Fourteenth International Meeting on Time-Resolved Vibrational Spectroscopy (TRVS XIV)

Science.gov (United States)

2010-02-03

conferences covering the use of advanced vibrational spectroscopy for the use of studying time-dependent molecular processes in chemistry, physics ...Netherlands a.huertaviga@uva.nl Neil Hunt Dept of  Physics , University of Strathclyde United Kingdom nhunt@phys.strath.ac Koichi Iwata Gakushuin University...Dasgupta Mark Creelman Sangdeok Shim Biochemical Reaction Dynamics, , , UC B k ler e ey 11:50 AM C W. Zinth, W. J. Schreier, J. Kubon, N. Regner, K

Collaborative Student Laboratory Exercise Using FT-IR Spectroscopy for the Kinetics Study of a Biotin Analogue

Science.gov (United States)

Leong, Jhaque; Ackroyd, Nathan C.; Ho, Karen

2014-01-01

The synthesis of N-methoxycarbonyl-2-imidazolidone, an analogue of biotin, was conducted by organic chemistry students and confirmed using FT-IR and H NMR. Spectroscopy students used FT-IR to measure the rate of hydrolysis of the product and determined the rate constant for the reaction using the integrated rate law. From the magnitude of the rate…

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

KAUST Repository

Dean, Jacob C.

2017-08-18

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

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.

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

International Nuclear Information System (INIS)

Wu, Guorong; Neville, Simon P.; Schalk, Oliver; Sekikawa, Taro; Ashfold, Michael N. R.; Worth, Graham A.; Stolow, Albert

2016-01-01

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 2 (πσ ∗ ) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B 1 (π3p y ) Rydberg state, followed by prompt internal conversion to the A 2 (πσ ∗ ) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A 2 (πσ ∗ ) 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 2 (πσ ∗ ) state, facilitating wavepacket motion around the potential barrier in the N–CH 3 dissociation coordinate

Preliminary study of corrosion mechanisms of actinides alloys: calibration of FT-IR spectroscopy

International Nuclear Information System (INIS)

Magnien, Veronique; Cadignan, Marx; Faivret, Olivier; Rosa, Gaelle

2008-01-01

In situ analyzes of gaseous atmospheres could be performed by FT-IR spectroscopy in order to study the corrosion reactions of actinides. Nevertheless experimental conditions and the nature of studied species have a strong effect on IR absorption laws. Thus a prior calibration of our set-up is required to obtain an accurate estimation of gas concentration. For this purpose, the behavior of several air pure gases has been investigated according to their concentration from IR spectra. Reproducible results revealed subsequent increases of the most significant peak areas with gas pressure and small deviations from Beer Lambert's law. This preliminary work allowed to determine precise absorption laws for each studied pure gas in our in situ experimental conditions. Besides our FT-IR set-up was well suitable to quantitative analysis of gaseous atmosphere during corrosion reactions. Finally the effect of foreign gas will be investigated through more complex air mixtures to obtain a complete calibration network. (authors)

Quasiparticle dynamics across the full Brillouin zone of Bi2Sr2CaCu2O8+δ traced with ultrafast time and angle-resolved photoemission spectroscopy

Directory of Open Access Journals (Sweden)

Georgi L. Dakovski

2015-09-01

Full Text Available A hallmark in the cuprate family of high-temperature superconductors is the nodal-antinodal dichotomy. In this regard, angle-resolved photoemission spectroscopy (ARPES has proven especially powerful, providing band structure information directly in energy-momentum space. Time-resolved ARPES (trARPES holds great promise of adding ultrafast temporal information, in an attempt to identify different interaction channels in the time domain. Previous studies of the cuprates using trARPES were handicapped by the low probing energy, which significantly limits the accessible momentum space. Using 20.15 eV, 12 fs pulses, we show for the first time the evolution of quasiparticles in the antinodal region of Bi2Sr2CaCu2O8+δ and demonstrate that non-monotonic relaxation dynamics dominates above a certain fluence threshold. The dynamics is heavily influenced by transient modification of the electron-phonon interaction and phase space restrictions, in stark contrast to the monotonic relaxation in the nodal and off-nodal regions.

Adding a dimension to the infrared spectra of interfaces: 2D SFG spectroscopy via mid-IR pulse shaping

Science.gov (United States)

Zanni, Martin

2012-02-01

Sum-frequency generation spectroscopy provides an infrared spectrum of interfaces and thus has widespread use in the materials and chemical sciences. In this presentation, I will present our recent work in developing a 2D pulse sequence to generate 2D SFG spectra of interfaces, in analogy to 2D infrared spectra used to measure bulk species. To develop this spectroscopy, we have utilized many of the tricks-of-the-trade developed in the 2D IR and 2D Vis communities in the last decade, including mid-IR pulse shaping. With mid-IR pulse shaping, the 2D pulse sequence is manipulated by computer programming in the desired frequency resolution, rotating frame, and signal pathway. We believe that 2D SFG will become an important tool in the interfacial sciences in an analogous way that 2D IR is now being used in many disciplines.

A time resolved microfocus XEOL facility at the Diamond Light Source

International Nuclear Information System (INIS)

Mosselmans, J F W; Taylor, R P; Quinn, P D; Cibin, G; Gianolio, D; Finch, A A; Sapelkin, A V

2013-01-01

We have constructed a Time-Resolved X-ray Excited Optical Luminescence (TR-XEOL) detection system at the Microfocus Spectroscopy beamline I18 at the Diamond Light Source. Using the synchrotron in h ybrid bunch mode , the data collection is triggered by the RF clock, and we are able to record XEOL photons with a time resolution of 6.1 ps during the 230 ns gap between the hybrid bunch and the main train of electron bunches. We can detect photons over the range 180-850 nm using a bespoke optical fibre, with X-ray excitation energies between 2 and 20 keV. We have used the system to study a range of feldspars. The detector is portable and has also been used on beamline B18 to collect Optically Determined X-ray Absorption Spectroscopy (OD-XAS) in QEXAFS mode.

A time resolved microfocus XEOL facility at the Diamond Light Source

Science.gov (United States)

Mosselmans, J. F. W.; Taylor, R. P.; Quinn, P. D.; Finch, A. A.; Cibin, G.; Gianolio, D.; Sapelkin, A. V.

2013-03-01

We have constructed a Time-Resolved X-ray Excited Optical Luminescence (TR-XEOL) detection system at the Microfocus Spectroscopy beamline I18 at the Diamond Light Source. Using the synchrotron in "hybrid bunch mode", the data collection is triggered by the RF clock, and we are able to record XEOL photons with a time resolution of 6.1 ps during the 230 ns gap between the hybrid bunch and the main train of electron bunches. We can detect photons over the range 180-850 nm using a bespoke optical fibre, with X-ray excitation energies between 2 and 20 keV. We have used the system to study a range of feldspars. The detector is portable and has also been used on beamline B18 to collect Optically Determined X-ray Absorption Spectroscopy (OD-XAS) in QEXAFS mode.

Site-Specific Characterization of Cytochrome P450cam Conformations by Infrared Spectroscopy.

Science.gov (United States)

Basom, Edward J; Maj, Michał; Cho, Minhaeng; Thielges, Megan C

2016-06-21

Conformational changes are central to protein function but challenging to characterize with both high spatial and temporal precision. The inherently fast time scale and small chromophores of infrared (IR) spectroscopy are well-suited for characterization of potentially rapidly fluctuating environments, and when frequency-resolved probes are incorporated to overcome spectral congestion, enable characterization of specific sites in proteins. We selectively incorporated p-cyanophenylalanine (CNF) as a vibrational probe at five distinct locations in the enzyme cytochrome P450cam and used IR spectroscopy to characterize the environments in substrate and/or ligand complexes reflecting those in the catalytic cycle. Molecular dynamics (MD) simulations were performed to provide a structural basis for spectral interpretation. Together the experimental and simulation data suggest that the CN frequencies are sensitive to both long-range influences, resulting from the particular location of a residue within the enzyme, as well as short-range influences from hydrogen bonding and packing interactions. The IR spectra demonstrate that the environments and effects of substrate and/or ligand binding are different at each position probed and also provide evidence that a single site can experience multiple environments. This study illustrates how IR spectroscopy, when combined with the spectral decongestion and spatial selectivity afforded by CNF incorporation, provides detailed information about protein structural changes that underlie function.

Complementary online aerosol mass spectrometry and offline FT-IR spectroscopy measurements: Prospects and challenges for the analysis of anthropogenic aerosol particle emissions

Science.gov (United States)

Faber, Peter; Drewnick, Frank; Bierl, Reinhard; Borrmann, Stephan

2017-10-01

The aerosol mass spectrometer (AMS) is well established in investigating highly time-resolved dynamics of submicron aerosol chemical composition including organic aerosol (OA). However, interpretation of mass spectra on molecular level is limited due to strong fragmentation of organic substances and potential reactions inside the AMS ion chamber. Results from complementary filter-based FT-IR absorption measurements were used to explain features in high-resolution AMS mass spectra of different types of OA (e.g. cooking OA, cigarette smoking OA, wood burning OA). Using this approach some AMS fragment ions were validated in this study as appropriate and rather specific markers for a certain class of organic compounds for all particle types under investigation. These markers can therefore be used to get deeper insights in the chemical composition of OA based on AMS mass spectra in upcoming studies. However, the specificity of other fragment ions such as C2H4O2+ (m/z 60.02114) remains ambiguous. In such cases, complementary FT-IR measurements allow the interpretation of highly time-resolved AMS mass spectra at the level of molecular functional groups. Furthermore, this study discusses the challenges in reducing inorganic interferences (e.g. from water and ammonium salts) in FT-IR spectra of atmospheric aerosols to decrease spectral uncertainties for better comparisons and, thus, to get more robust results.

Nonlinear optical response of chalcogenide glassy semiconductors in the IR and THz ranges studied with the femtosecond resolution in time

DEFF Research Database (Denmark)

Romanova, E.; Guizard, S.; Wang, Tianwu

2017-01-01

Two time-resolved experimental methods have been used for characterization of the non-linear optical response of chalcogenide glasses of the system As-S-Se-Te in IR and THz ranges upon excitation by femtosecond laser pulses at 800 nm wavelength. Photoinduced conductivity and refractivity were stu...

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

Science.gov (United States)

Smith, Adam W

2015-01-01

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

Time-resolved laser spectroscopy in the UV/VUV spectral region

International Nuclear Information System (INIS)

Bengtsson, J.

1992-01-01

Radiative lifetimes ranging from 3 to 500 ns were measured on various states of Ag, N, Se, Te and As, by recording the fluorescence light decay after excitation by a laser pulse. Ag was supplied by a collimated atomic beam while Se, Te and As were contained in quartz cells. Pulsed laser radiation, with a wavelength down to 185 nm, was generated by different set-ups, using Nd-YAG pumped dye lasers combined with non-linear crystals and Raman shifting. Short laser pulses were produced by a nitrogen laser or a distributed feedback dye laser. Two-photon processes and stepwise excitation were used to populate high-lying levels. Depletion spectroscopy, quantum-beat spectroscopy and optical double resonance spectroscopy were also performed

Comb-Resolved Dual-Comb Spectroscopy Stabilized by Free-Running Continuous-Wave Lasers

Science.gov (United States)

Kuse, Naoya; Ozawa, Akira; Kobayashi, Yohei

2012-11-01

We demonstrate dual-comb spectroscopy with relatively phase-locked two frequency combs, instead of frequency combs firmly fixed to the absolute frequency references. By stabilizing two beat frequencies between two mode-locked lasers at different wavelengths observed via free-running continuous-wave (CW) lasers, two combs are tightly phase locked to each other. The frequency noise of the CW lasers barely affects the performance of dual-comb spectroscopy because of the extremely fast common-mode noise rejection. Transform-limited comb-resolved dual-comb spectroscopy with a 6 Hz radio frequency linewidth is demonstrated by the use of Yb-fiber oscillators.

Chemical sensitivity of InP/In0.48Ga0.52P surface quantum dots studied by time-resolved photoluminescence spectroscopy

International Nuclear Information System (INIS)

De Angelis, Roberta; Casalboni, Mauro; De Matteis, Fabio; Hatami, Fariba; Masselink, William T.; Zhang, Hong; Prosposito, Paolo

2015-01-01

InP/InGaP surface quantum dots represent an attractive material for optical chemical sensors since they show a remarkable near infra-red emission at room temperature, whose intensity increases rapidly and reversibly depending on the composition of the environmental atmosphere. We show here their emission properties by time resolved photoluminescence spectroscopy investigation. Photoluminescence transients with and without chemical solvent vapours (methanol, clorophorm, acetone and water) were fitted with a 3-exponential decay law with times of about 0.5 ns, 2 ns and 7 ns. The measurements revealed a weak effect on clorophorm, acetone and water, while the initial decay time of InP surface quantum dots increases (up to 15%) upon methanol vapour exposure, indicating that the organic molecules efficiently saturate QD non-radiative surface states. - Highlights: • InP SQDs emission depends on the presence of solvent vapours in the atmosphere. • TR photoluminescence transients were fitted with a 3-exponential decay law. • The initial decay time increases (up to 15%) upon methanol vapour exposure. • Organic molecules efficiently saturate QD non-radiative surface states.

Monitoring lipase-catalyzed interesterification for bulky fats modification with FT-IR/NIR spectroscopy

DEFF Research Database (Denmark)

Chang, Tinghong; Lai, Xuxin; Zhang, Hong

2005-01-01

This work demonstrates the application of FT-IR and FT-NIR spectroscopy to monitor the enzymatic interesterification process for bulky fat modification. The reaction was conducted between palm stearin and coconut oil (70/30, w/w) with the catalysis of Lipozyme TL IM at 70°C in a batch reactor...

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

Energy Technology Data Exchange (ETDEWEB)

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

2010-04-30

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

The structure of salt bridges between Arg(+) and Glu(-) in peptides investigated with 2D-IR spectroscopy: Evidence for two distinct hydrogen-bond geometries.

Science.gov (United States)

Huerta-Viga, Adriana; Amirjalayer, Saeed; Domingos, Sérgio R; Meuzelaar, Heleen; Rupenyan, Alisa; Woutersen, Sander

2015-06-07

Salt bridges play an important role in protein folding and in supramolecular chemistry, but they are difficult to detect and characterize in solution. Here, we investigate salt bridges between glutamate (Glu(-)) and arginine (Arg(+)) using two-dimensional infrared (2D-IR) spectroscopy. The 2D-IR spectrum of a salt-bridged dimer shows cross peaks between the vibrational modes of Glu(-) and Arg(+), which provide a sensitive structural probe of Glu(-)⋯Arg(+) salt bridges. We use this probe to investigate a β-turn locked by a salt bridge, an α-helical peptide whose structure is stabilized by salt bridges, and a coiled coil that is stabilized by intra- and intermolecular salt bridges. We detect a bidentate salt bridge in the β-turn, a monodentate one in the α-helical peptide, and both salt-bridge geometries in the coiled coil. To our knowledge, this is the first time 2D-IR has been used to probe tertiary side chain interactions in peptides, and our results show that 2D-IR spectroscopy is a powerful method for investigating salt bridges in solution.

Ultrafast time-resolved faraday rotation in EuO thin films.

Science.gov (United States)

Liu, F; Makino, T; Yamasaki, T; Ueno, K; Tsukazaki, A; Fukumura, T; Kong, Y; Kawasaki, M

2012-06-22

We have investigated the ultrafast spin dynamics in EuO thin films by time-resolved Faraday rotation spectroscopy. The photoinduced magnetization is found to be increased in a transient manner, accompanied with subsequent demagnetization. The dynamical magnetization enhancement showed a maximum slightly below the Curie temperature with prolonged tails toward both lower and higher temperatures and dominates the demagnetization counterpart at 55 K. The magnetization enhancement component decays in ~1 ns. The realization of the transient collective ordering is attributable to the enhancement of the f-d exchange interaction.

Atomic column resolved electron energy-loss spectroscopy

International Nuclear Information System (INIS)

Duscher, G.; Pennycook, S.J.; Browning, N.D.

1998-01-01

Spatially resolved electron energy-loss spectroscopy (EELS) is rapidly developing into a unique and powerful tool to characterize internal interfaces. Because atomic column resolved Z-contrast imaging can be performed simultaneously with EELS in the scanning transmission electron microscope, this combination allows the atomic structure to be correlated with the electronic structure, and thus the local properties of interfaces or defects can be determined directly. However, the ability to characterize interfaces and defects at that level requires not only high spatial resolution but also the exact knowledge of the beam location, from where the spectrum is obtained. Here we discuss several examples progressing from cases where the limitation in spatial resolution is given by the microscopes or the nature of the sample, to one example of impurity atoms at a grain boundary, which show intensity and fine structure changes from atomic column to atomic column. Such data can be interpreted as changes in valence of the impurity, depending on its exact site in the boundary plane. Analysis ofthis nature is a valuable first step in understanding the microscopic structural, optical and electronic properties of materials. (orig.)

Exciplex formation in bimolecular photoinduced electron-transfer investigated by ultrafast time-resolved infrared spectroscopy.

Science.gov (United States)

Koch, Marius; Letrun, Romain; Vauthey, Eric

2014-03-12

The dynamics of bimolecular photoinduced electron-transfer reactions has been investigated with three donor/acceptor (D/A) pairs in tetrahydrofuran (THF) and acetonitrile (ACN) using a combination of ultrafast spectroscopic techniques, including time-resolved infrared absorption. For the D/A pairs with the highest driving force of electron transfer, all transient spectroscopic features can be unambiguously assigned to the excited reactant and the ionic products. For the pair with the lowest driving force, three additional transient infrared bands, more intense in THF than in ACN, with a time dependence that differs from those of the other bands are observed. From their frequency and solvent dependence, these bands can be assigned to an exciplex. Moreover, polarization-resolved measurements point to a relatively well-defined mutual orientation of the constituents and to a slower reorientational time compared to those of the individual reactants. Thanks to the minimal overlap of the infrared signature of all transient species in THF, a detailed reaction scheme including the relevant kinetic and thermodynamic parameters could be deduced for this pair. This analysis reveals that the formation and recombination of the ion pair occur almost exclusively via the exciplex.

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

Directory of Open Access Journals (Sweden)

Alexander Boreham

2016-12-01

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

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

Science.gov (United States)

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

2016-12-24

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

Detecting infrared luminescence and non-chemical signaling of living cells: single cell mid-IR spectroscopy in cryogenic environments

Science.gov (United States)

Pereverzev, Sergey

2017-02-01

Many life-relevant interaction energies are in IR range, and it is reasonable to believe that some biochemical reactions inside cells can results in emission of IR photons. Cells can use this emission for non-chemical and non-electrical signaling. Detecting weak infrared radiation from live cells is complicated because of strong thermal radiation background and absorption of radiation by tissues. A microfluidic device with live cells inside a vacuum cryogenic environment should suppress this background, and thereby permit observation of live cell auto-luminescence or signaling in the IR regime. One can make IR-transparent windows not emitting in this range, so only the cell and a small amount of liquid around it will emit infrared radiation. Currently mid-IR spectroscopy of single cells requires the use of a synchrotron source to measure absorption or reflection spectra. Decreasing of thermal radiation background will allow absorption and reflection spectroscopy of cells without using synchrotron light. Moreover, cell auto-luminescence can be directly measured. The complete absence of thermal background radiation for cryogenically cooled samples allows the use IR photon-sensitive detectors and obtaining single molecule sensitivity in IR photo-luminescence measurements. Due to low photon energies, photo-luminescence measurements will be non-distractive for pressures samples. The technique described here is based upon US patent 9366574.

Time resolved plasma characterization in a long conduction time planar plasma opening switch

International Nuclear Information System (INIS)

Adler, L.K.; Greenly, J.B.; Qi, N.; Hammer, D.A.

1989-01-01

The authors discuss additional experiments in which the plasma dynamics and properties will be monitored in detail before and during opening. Space and time resolved density, temperature and motion information about the plasma and neutrals is given by emission spectroscopy and streak photography and correlated to the current and voltage traces. Specifically, we will look for the effects of neutrals evolving off of surfaces, stagnation of the switch plasma, and rvec J x rvec B motion of the plasma downstream of the switch. Diagnostics include current and voltage monitors, a multi-aperture biased Faraday cup, emission spectroscopy and streak photography. Pairs of B dot loops are positioned in the stripline just upstream and downstream of the POS. Also, two single B loops were placed further downstream to look for bulk plasma motion. An inductive monitor gives the voltage at the upstream side of the POS and the Faraday cup monitors the gun plasma consistency from shot to shot

Characterization by Fourier transform infrared spectroscopy (FT-IR) and 2D IR correlation spectroscopy of a carbosilane dendrimer with peripheral ammonium groups

Energy Technology Data Exchange (ETDEWEB)

Popescu, Maria-Cristina, E-mail: cpopescu@icmpp.ro [' Petru Poni' Institute of Macromolecular Chemistry (Romania); Gomez, Rafael; Mata, Fco Javier de la; Rasines, Beatriz [Universidad de Alcala, Departamento de Quimica Inorganica (Spain); Simionescu, Bogdan C. [' Petru Poni' Institute of Macromolecular Chemistry (Romania)

2013-06-15

Fourier transform infrared spectroscopy and 2D correlation spectroscopy were used to study the microstructural changes occurring on heating of a new carbosilane dendrimer with peripheral ammonium groups. Temperature-dependent spectral variations in the 3,010-2,710, 1,530-1,170, and 1,170-625 cm{sup -1} regions were monitored during the heating process. The dependence, on temperature, of integral absorptions and position of spectral bands was established and the spectral modifications associated with molecular conformation rearrangements, allowing molecular shape changes, were found. Before 180 Degree-Sign C, the studied carbosilane dendrimer proved to be stable, while at higher temperatures it oxidizes and Si-O groups appear. 2D IR correlation spectroscopy gives new information about the effect of temperature on the structure and dynamics of the system. Synchronous and asynchronous spectra indicate that, at low temperature, conformational changes of CH{sub 3} and CH{sub 3}-N{sup +} groups take place first. With increasing temperature, the intensity variation of the CH{sub 2}, C-N, Si-C and C-C groups from the dendritic core is faster than that of the terminal units. This indicates that, with increasing temperature, the segments of the dendritic core obtain enough energy to change their conformation more easily as compared to the terminal units, due to their internal flexibility.

Characterization by Fourier transform infrared spectroscopy (FT-IR) and 2D IR correlation spectroscopy of a carbosilane dendrimer with peripheral ammonium groups

International Nuclear Information System (INIS)

Popescu, Maria-Cristina; Gómez, Rafael; Mata, Fco Javier de la; Rasines, Beatriz; Simionescu, Bogdan C.

2013-01-01

Fourier transform infrared spectroscopy and 2D correlation spectroscopy were used to study the microstructural changes occurring on heating of a new carbosilane dendrimer with peripheral ammonium groups. Temperature-dependent spectral variations in the 3,010–2,710, 1,530–1,170, and 1,170–625 cm −1 regions were monitored during the heating process. The dependence, on temperature, of integral absorptions and position of spectral bands was established and the spectral modifications associated with molecular conformation rearrangements, allowing molecular shape changes, were found. Before 180 °C, the studied carbosilane dendrimer proved to be stable, while at higher temperatures it oxidizes and Si–O groups appear. 2D IR correlation spectroscopy gives new information about the effect of temperature on the structure and dynamics of the system. Synchronous and asynchronous spectra indicate that, at low temperature, conformational changes of CH 3 and CH 3 –N + groups take place first. With increasing temperature, the intensity variation of the CH 2 , C–N, Si–C and C–C groups from the dendritic core is faster than that of the terminal units. This indicates that, with increasing temperature, the segments of the dendritic core obtain enough energy to change their conformation more easily as compared to the terminal units, due to their internal flexibility.

Proceedings of the Third Symposium Optical Spectroscopy SOS-84

International Nuclear Information System (INIS)

Fassler, D.; Feller, K.H.; Wilhelmi, B.

1985-01-01

The main topics of the symposium were: 1) new developments and applications of laser spectroscopy including time resolved UV/VIS spectroscopy, time resolved fluorescence spectroscopy, and laser Raman spectroscopy, 2) dynamics and photokinetics of molecular systems, and 3) spectroscopy and photoprocesses in organized biological systems

Chapter 1.1 Crystallinity of Nanocellulose Materials by Near-IR FT-Raman Spectroscopy

Science.gov (United States)

Umesh P. Agarwal; Richard S. Reiner; Sally A. Ralph

2013-01-01

Considering that crystallinity is one of the important properties that influence the end use of cellulose nanomaterials, it is important that the former be measured accurately. Recently, a new method based on near-IR FTRaman spectroscopy was proposed to determine cellulose I crystallinity. It was reported that in the Raman spectrum of cellulose materials, the...

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-12-20

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

Relationship between time-resolved and non-time-resolved Beer-Lambert law in turbid media.

Science.gov (United States)

Nomura, Y; Hazeki, O; Tamura, M

1997-06-01

The time-resolved Beer-Lambert law proposed for oxygen monitoring using pulsed light was extended to the non-time-resolved case in a scattered medium such as living tissues with continuous illumination. The time-resolved Beer-Lambert law was valid for the phantom model and living tissues in the visible and near-infrared regions. The absolute concentration and oxygen saturation of haemoglobin in rat brain and thigh muscle could be determined. The temporal profile of rat brain was reproduced by Monte Carlo simulation. When the temporal profiles of rat brain under different oxygenation states were integrated with time, the absorbance difference was linearly related to changes in the absorption coefficient. When the simulated profiles were integrated, there was a linear relationship within the absorption coefficient which was predicted for fractional inspiratory oxygen concentration from 10 to 100% and, in the case beyond the range of the absorption coefficient, the deviation from linearity was slight. We concluded that an optical pathlength which is independent of changes in the absorption coefficient is a good approximation for near-infrared oxygen monitoring.

Development of a method for the in situ measurement of polycyclic aromatic hydrocarbons with time resolved laser fluorescence spectroscopy. Final report

International Nuclear Information System (INIS)

Jaeger, E.; Weissbach, A.; Koenig, F.; Paul, T.

1994-01-01

A method was developed for the detection of polycyclic aromatic hydrocarbons (PAH) in water on the basis of time resolved laser fluorescence spectroscopy. The detection of the sum of PAH in ground- and surfacewater is possible with high sensitivity and selectivity. The fluorescence of other substances like chlorophyll or dissolved organic matter is suppressed by a special choice of spectral and temporal windows. The method works without any sample preparation and gives the results in a very short time. On the basis of this method a first device was built with a sensitivity of 0,1 μg/1 PAH in water. The measuring time was less than one minute. The on site use of this prototype is possible because of the use of a battery driven nitrogen laser together with a notebook computer for system control The application of fiberoptic cables up to 30 meter length makes it possible to use the system for screening and monitoring of polluted areas both in existing wells and without any well by using geological probe techniques. (orig.) [de

Noncontact blood species identification method based on spatially resolved near-infrared transmission spectroscopy

Science.gov (United States)

Zhang, Linna; Sun, Meixiu; Wang, Zhennan; Li, Hongxiao; Li, Yingxin; Li, Gang; Lin, Ling

2017-09-01

The inspection and identification of whole blood are crucially significant for import-export ports and inspection and quarantine departments. In our previous research, we proved Near-Infrared diffuse transmitted spectroscopy method was potential for noninvasively identifying three blood species, including macaque, human and mouse, with samples measured in the cuvettes. However, in open sampling cases, inspectors may be endangered by virulence factors in blood samples. In this paper, we explored the noncontact measurement for classification, with blood samples measured in the vacuum blood vessels. Spatially resolved near-infrared spectroscopy was used to improve the prediction accuracy. Results showed that the prediction accuracy of the model built with nine detection points was more than 90% in identification between all five species, including chicken, goat, macaque, pig and rat, far better than the performance of the model built with single-point spectra. The results fully supported the idea that spatially resolved near-infrared spectroscopy method can improve the prediction ability, and demonstrated the feasibility of this method for noncontact blood species identification in practical applications.

Excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene. I. Time-resolved photoelectron-photoion coincidence spectroscopy

Science.gov (United States)

Boguslavskiy, Andrey E.; Schalk, Oliver; Gador, Niklas; Glover, William J.; Mori, Toshifumi; Schultz, Thomas; Schuurman, Michael S.; Martínez, Todd J.; Stolow, Albert

2018-04-01

The ultrafast excited state dynamics of the smallest polyene, trans-1,3-butadiene, were studied by femtosecond time-resolved photoelectron-photoion coincidence (TRPEPICO) spectroscopy. The evolution of the excited state wavepacket, created by pumping the bright 1Bu (ππ*) electronic state at its origin of 216 nm, is projected via one- and two-photon ionization at 267 nm onto several ionization continua. The results are interpreted in terms of Koopmans' correlations and Franck-Condon factors for the excited and cationic states involved. The known predissociative character of the cation excited states is utilized to assign photoelectron bands to specific continua using TRPEPICO spectroscopy. This permits us to report the direct observation of the famously elusive S1(21Ag) dark electronic state during the internal conversion of trans 1,3-butadiene. Our phenomenological analysis permits the spectroscopic determination of several important time constants. We report the overall decay lifetimes of the 11Bu and 21Ag states and observe the re-appearance of the hot ground state molecule. We argue that the apparent dephasing time of the S2(11Bu) state, which leads to the extreme breadth of the absorption spectrum, is principally due to large amplitude torsional motion on the 1Bu surface in conjunction with strong non-adiabatic couplings via conical intersections, whereupon nuclear wavepacket revivals to the initial Franck-Condon region become effectively impossible. In Paper II [W. J. Glover et al., J. Chem. Phys. 148, 164303 (2018)], ab initio multiple spawning is used for on-the-fly computations of the excited state non-adiabatic wavepacket dynamics and their associated TRPEPICO observables, allowing for direct comparisons of experiment with theory.

Unfolding of Ubiquitin Studied by Picosecond Time-Resolved Fluorescence of the Tyrosine Residue

OpenAIRE

Noronha, Melinda; Lima, João C.; Bastos, Margarida; Santos, Helena; Maçanita, António L.

2004-01-01

The photophysics of the single tyrosine in bovine ubiquitin (UBQ) was studied by picosecond time-resolved fluorescence spectroscopy, as a function of pH and along thermal and chemical unfolding, with the following results: First, at room temperature (25°C) and below pH 1.5, native UBQ shows single-exponential decays. From pH 2 to 7, triple-exponential decays were observed and the three decay times were attributed to the presence of tyrosine, a tyrosine-carboxylate hydrogen-bonded complex, and...

Studies on Ternary Complex Formation of U(VI)-salicylate by Using Time-resolved Fluorescence Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Cha, Wan Sik; Cho, H. R.; Park, K. K.; Kim, W. H.; Jung, E. C. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2010-05-15

Organic ligands containing carboxylic and phenolic functional groups naturally occur in groundwater environment, particularly in forms of polyelectrolytes such as humic and fulvic acids, from microbial degradation of biomass, e.g., plant and animal tissues. These ligands play important roles in dissolution and migration of actinide radionuclide species since they can form stable ternary actinide complexes with common inorganic ions like hydroxides and carbonates. Therefore, model ternary complexes of lanthanides and actinides have been targets of studies to understand their chemical behaviors under near-neutral pH groundwater conditions. Previous model carboxylic ligands include phthalates, maleic acids, or alpha- substituted carboxylic acids. However, majority of previous studies investigated binary systems or used potentiometric titration method that requires high ligand concentration in mM levels. Recently, highly sensitive time-resolved laserinduced fluorescence spectroscopy (TRLFS) has been used to investigate lower concentration (e.g., a few {mu}M levels) reactions of binary complexes between of ligands and metal ions. This technique provides information regarding electronic structures and complexation constants as well as fluorescence quenching mechanism. In the present study, we studied the U(VI)-OH-salicylate (SA) ternary complex formation at higher pH (> 4) via TRLF spectrum and UV-Vis absorbance measurement. Preliminary studies show that the fluorescence (FL) intensity of hydroxouranyl species at pH 4.5 decreases as SA concentration elevates in aqueous solution. Fluorescence quenching mechanism by SA is suggested based on FL intensity (I) and lifetime (tau) measurement via TRLFS

Spatially resolved x-ray fluorescence spectroscopy of beryllium capsule implosions at the NIF

Science.gov (United States)

MacDonald, M. J.; Bishel, D. T.; Saunders, A. M.; Scott, H. A.; Kyrala, G.; Kline, J.; MacLaren, S.; Thorn, D. B.; Yi, S. A.; Zylstra, A. B.; Falcone, R. W.; Doeppner, T.

2017-10-01

Beryllium ablators used in indirectly driven inertial confinement fusion implosions are doped with copper to prevent preheat of the cryogenic hydrogen fuel. Here, we present analysis of spatially resolved copper K- α fluorescence spectra from the beryllium ablator layer. It has been shown that K- α fluorescence spectroscopy can be used to measure plasma conditions of partially ionized dopants in high energy density systems. In these experiments, K-shell vacancies in the copper dopant are created by the hotspot emission at stagnation, resulting in K-shell fluorescence at bang time. Spatially resolved copper K- α emission spectra are compared to atomic kinetics and radiation code simulations to infer density and temperature profiles. This work was supported by the US DOE under Grant No. DE-NA0001859, under the auspices of the US DOE by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344, and by Los Alamos National Laboratory under contract DE-AC52-06NA52396.

Thermo-oxidative degradation study of melt-processed polyethylene and its blend with polyamide using time-resolved rheometry

CSIR Research Space (South Africa)

Salehiyan, Reza

2017-05-01

Full Text Available Time-resolved mechanical spectroscopy (TRMS) was conducted to study the thermo-oxidative degradation of linear low density polyethylene (LLDPE) samples with different thermal histories and their blends with a polyamide (PA6) in the melt state. Neat...

Time-resolved study of formate on Ni( 1 1 1 ) by picosecond SFG spectroscopy

Science.gov (United States)

Kusafuka, K.; Noguchi, H.; Onda, K.; Kubota, J.; Domen, K.; Hirose, C.; Wada, A.

2002-04-01

Time-resolved vibrational measurements were carried out on formate (HCOO) adsorbed on Ni(1 1 1) surface by combining the sum-frequency generation method and picosecond laser system (time resolution of 6 ps). Rapid intensity decrease (within the time resolution) followed by intensity recovery (time constant of several tens of ps) of CH stretching signal was observed when picosecond 800 nm pulse was irradiated on the sample surface. From the results of temperature and pump fluence dependences of temporal behaviour of signal intensity, we concluded that the observed intensity change was induced by non-thermal process. Mechanism of the temporal intensity change was discussed.

Fast infrared spectroscopy in supercritical fluids

International Nuclear Information System (INIS)

Sun, X.

2000-05-01

Chapter 1: Introduction. A brief introduction to supercritical fluids is given, illustrating why supercritical fluids are unique solvents and why there is a wide application of supercritical fluids in industry and laboratories. Potential ways for solvation in supercritical fluids to affect reactivity are briefly reviewed. A general introduction to the photochemistry of organometallic complexes is also given. Chapter 2: Time resolved vibrational spectroscopy. Time resolved resonance Raman is introduced and compared with Time-resolved infrared spectroscopy (TRIR). The different approaches of TRIR, including microsecond, nanosecond, and ultrafast (picosecond and femtosecond) systems are discussed. The advantages and disadvantages of these systems are also compared. The TRIR apparatus using an IR diode laser used for work in this thesis are described in detail. Experimental procedures for supercritical fluid TRIR experiments are described with emphasis on handling the IR cell for supercritical fluids and preparation of supercritical fluid solutions. Chapter 3: Photochemistry of group VIB hexacarbonyl compounds in supercritical noble gases and CO 2 solutions. A systematic TRIR study of the photolysis of M(CO) 6 in supercritical Ar, Kr, Xe, and CO 2 and the observation of M(CO) 5 L (M = Cr, Mo, and W; L = Ar (W only), Kr, Xe, and CO 2 ) is described. The second-order rate constants for the reaction of M(CO) 5 L with CO have been evaluated and the reactivity for each metal is Kr > Xe ∼ CO 2 . For M(CO) 5 Kr, M(CO) 5 Xe, or M(CO) 5 (CO 2 ), the reactivity is Cr ∼ Mo > W. In supercritical Kr doped with either Xe or CO 2 , the M(CO) 5 moiety interacts with Xe or CO 2 in preference to Kr. The effect of solvent density on the rate of the reaction of W(CO) 5 (CO 2 ) with CO has been investigated. The reaction of W(CO) 5 (CO 2 ) with CO in scCO 2 is predominantly a dissociative process. The activation energies for the reaction of W(CO) 5 Xe and W(CO) 5 (CO 2 ) with CO and

IR Spectroscopy of Ethylene Glycol Solutions of Dimethylsulfoxide

Science.gov (United States)

Kononova, E. G.; Rodnikova, M. N.; Solonina, I. A.; Sirotkin, D. A.

2018-07-01

Features of ethylene glycol (EG) solutions of dimethylsulfoxide (DMSO) with low and moderate concentrations (from 2 to 50 mol % of DMSO) are studied by IR spectroscopy on a Bruker Tensor 37 FT-IR spectrometer in the wavenumber range of 400 to 4000 cm-1. The main monitored bands are the S=O stretching vibration band of DMSO (1057 cm-1) and the C-O (1086 and 1041 cm-1) and O-H (3350 cm-1) stretching vibration bands of EG. The obtained data show complex DMSO · 2EG to be present in all solutions with the studied concentrations due to formation of H-bonds between the S=O group of DMSO and the OH group of EG. In the concentration range of 6 to 25 mol % DMSO, the OH stretching vibration of EG is found to be broadened (by up to 70 cm-1), suggesting the strengthening of hydrogen bonds in the spatial network of the system due to the solvophobic effect of DMSO molecules and the formation of DMSO · 2EG. Starting from 25 mol % DMSO, narrowing of the OH stretching vibration is noted, and the bands of free DMSO appear along with the DMSO · 2EG complex, suggesting microseparation in the investigated system. At 50 mol % DMSO, the amounts of free and bound species in the system became comparable.

Using Fourier transform IR spectroscopy to analyze biological materials

Science.gov (United States)

Baker, Matthew J; Trevisan, Júlio; Bassan, Paul; Bhargava, Rohit; Butler, Holly J; Dorling, Konrad M; Fielden, Peter R; Fogarty, Simon W; Fullwood, Nigel J; Heys, Kelly A; Hughes, Caryn; Lasch, Peter; Martin-Hirsch, Pierre L; Obinaju, Blessing; Sockalingum, Ganesh D; Sulé-Suso, Josep; Strong, Rebecca J; Walsh, Michael J; Wood, Bayden R; Gardner, Peter; Martin, Francis L

2015-01-01

IR spectroscopy is an excellent method for biological analyses. It enables the nonperturbative, label-free extraction of biochemical information and images toward diagnosis and the assessment of cell functionality. Although not strictly microscopy in the conventional sense, it allows the construction of images of tissue or cell architecture by the passing of spectral data through a variety of computational algorithms. Because such images are constructed from fingerprint spectra, the notion is that they can be an objective reflection of the underlying health status of the analyzed sample. One of the major difficulties in the field has been determining a consensus on spectral pre-processing and data analysis. This manuscript brings together as coauthors some of the leaders in this field to allow the standardization of methods and procedures for adapting a multistage approach to a methodology that can be applied to a variety of cell biological questions or used within a clinical setting for disease screening or diagnosis. We describe a protocol for collecting IR spectra and images from biological samples (e.g., fixed cytology and tissue sections, live cells or biofluids) that assesses the instrumental options available, appropriate sample preparation, different sampling modes as well as important advances in spectral data acquisition. After acquisition, data processing consists of a sequence of steps including quality control, spectral pre-processing, feature extraction and classification of the supervised or unsupervised type. A typical experiment can be completed and analyzed within hours. Example results are presented on the use of IR spectra combined with multivariate data processing. PMID:24992094

Time-resolved x-ray spectra from laser-generated high-density plasmas

Science.gov (United States)

Andiel, U.; Eidmann, Klaus; Witte, Klaus-Juergen

2001-04-01

We focused frequency doubled ultra short laser pulses on solid C, F, Na and Al targets, K-shell emission was systematically investigated by time resolved spectroscopy using a sub-ps streak camera. A large number of laser shots can be accumulated when triggering the camera with an Auston switch system at very high temporal precision. The system provides an outstanding time resolution of 1.7ps accumulating thousands of laser shots. The time duration of the He-(alpha) K-shell resonance lines was observed in the range of (2-4)ps and shows a decrease with the atomic number. The experimental results are well reproduced by hydro code simulations post processed with an atomic kinetics code.

Time-resolved soft x-ray absorption setup using multi-bunch operation modes at synchrotrons

International Nuclear Information System (INIS)

Stebel, L.; Sigalotti, P.; Ressel, B.; Cautero, G.; Malvestuto, M.; Capogrosso, V.; Bondino, F.; Magnano, E.; Parmigiani, F.

2011-01-01

Here, we report on a novel experimental apparatus for performing time-resolved soft x-ray absorption spectroscopy in the sub-ns time scale using non-hybrid multi-bunch mode synchrotron radiation. The present setup is based on a variable repetition rate Ti:sapphire laser (pump pulse) synchronized with the ∼500 MHz x-ray synchrotron radiation bunches and on a detection system that discriminates and singles out the significant x-ray photon pulses by means of a custom made photon counting unit. The whole setup has been validated by measuring the time evolution of the L 3 absorption edge during the melting and the solidification of a Ge single crystal irradiated by an intense ultrafast laser pulse. These results pave the way for performing synchrotron time-resolved experiments in the sub-ns time domain with variable repetition rate exploiting the full flux of the synchrotron radiation.

Toward practical terahertz time-domain spectroscopy

Science.gov (United States)

Brigada, David J.

Terahertz time-domain spectroscopy is a promising technology for the identification of explosive and pharmaceutical substances in adverse conditions. It interacts strongly with intermolecular vibrational and rotational modes. Terahertz also passes through many common dielectric covering materials, allowing for the identification of substances in envelopes, wrapped in opaque plastic, or otherwise hidden. However, there are several challenges preventing the adoption of terahertz spectroscopy outside the laboratory. This dissertation examines the problems preventing widespread adoption of terahertz technology and attempts to resolve them. In order to use terahertz spectroscopy to identify substances, a spectrum measured of the target sample must be compared to the spectra of various known standard samples. This dissertation examines various methods that can be employed throughout the entire process of acquiring and transforming terahertz waveforms to improve the accuracy of these comparisons. The concepts developed in this dissertation directly apply to terahertz spectroscopy, but also carry implications for other spectroscopy methods, from Raman to mass spectrometry. For example, these techniques could help to lower the rate of false positives at airport security checkpoints. This dissertation also examines the implementation of several of these methods as a way to realize a fully self-contained, handheld, battery-operated terahertz spectrometer. This device also employs techniques to allow minimally-trained operators use terahertz to detect different substances of interest. It functions as a proof-of-concept of the true benefits of the improvements that have been developed in this dissertation.

Understanding optically stimulated charge movement in quartz and feldspar using time-resolved measurements

International Nuclear Information System (INIS)

Ankjaergaard, C.

2010-02-01

Thermoluminescence (TL) and optically stimulated luminescence (OSL) from quartz and feldspar are widely used in accident dosimetry and luminescence dating. In order to improve already existing methods or to develop new methods towards extending the current limits of the technique, it is important to understand the charge movement within these materials. Earlier studies have primarily focussed on examination of the trap behaviour; however, this only tells half of the story as OSL is a combination of charge stimulation and recombination. By using time-resolved OSL (TR-OSL), one can directly examine the recombination route(s), and thus obtain insight into the other half of the process involved in luminescence emission. This thesis studies the TR-OSL and optically stimulated phosphorescence signals from quartz and feldspars spanning several orders of magnitude in time (few ns to the seconds time scale) in order to identify various charge transport mechanisms in the different time regimes. The techniques employed are time-resolved OSL, continuous-wave OSL, TL, optically stimulated exo-electron (OSE) emission and time-resolved OSE. These different techniques are used in combination with variable thermal or optical stimulation energy. The thesis first delves into three main methodological developments, namely (i) research and development of the equipment for TR-OSL measurements, (ii) finding the best method for multiple-exponential analysis of a TR-OSL curve, and (iii) optimisation of the pulsing configuration for the best separation of quartz OSL from a mixed quarts-feldspar sample. It then proceeds to study the different charge transport mechanisms subsequent to an optical stimulation pulse in quartz and feldspars. The results obtained for quartz conclude that the main lifetime component in quartz represents an excited state lifetime of the recombination centre, and the more slowly decaying components on the millisecond to seconds time scale arise from charge recycling

Understanding optically stimulated charge movement in quartz and feldspar using time-resolved measurements

Energy Technology Data Exchange (ETDEWEB)

Ankjaergaard, C.

2010-02-15

Thermoluminescence (TL) and optically stimulated luminescence (OSL) from quartz and feldspar are widely used in accident dosimetry and luminescence dating. In order to improve already existing methods or to develop new methods towards extending the current limits of the technique, it is important to understand the charge movement within these materials. Earlier studies have primarily focussed on examination of the trap behaviour; however, this only tells half of the story as OSL is a combination of charge stimulation and recombination. By using time-resolved OSL (TR-OSL), one can directly examine the recombination route(s), and thus obtain insight into the other half of the process involved in luminescence emission. This thesis studies the TR-OSL and optically stimulated phosphorescence signals from quartz and feldspars spanning several orders of magnitude in time (few ns to the seconds time scale) in order to identify various charge transport mechanisms in the different time regimes. The techniques employed are time-resolved OSL, continuous-wave OSL, TL, optically stimulated exo-electron (OSE) emission and time-resolved OSE. These different techniques are used in combination with variable thermal or optical stimulation energy. The thesis first delves into three main methodological developments, namely (i) research and development of the equipment for TR-OSL measurements, (ii) finding the best method for multiple-exponential analysis of a TR-OSL curve, and (iii) optimisation of the pulsing configuration for the best separation of quartz OSL from a mixed quarts-feldspar sample. It then proceeds to study the different charge transport mechanisms subsequent to an optical stimulation pulse in quartz and feldspars. The results obtained for quartz conclude that the main lifetime component in quartz represents an excited state lifetime of the recombination centre, and the more slowly decaying components on the millisecond to seconds time scale arise from charge recycling

Study of the Pyrrol/Diphenylamine Copolymer by FT-IR spectroscopy and conductivity

Directory of Open Access Journals (Sweden)

Carlos Alberto Perez

2004-01-01

Full Text Available The main goal of this study was to analyze the physical properties of the copolymer formed by the electrochemical deposition of the polydiphenylamine (PDPA on polypyrrole (Ppy and Ppy on PDPA, in different conditions, through the characterization of the materials formed by the resonant Raman, FT-IR and conductivity techniques. The interactions among the species which are present in the new copolymer structure and the changes in electronic conductivity, were verified. The copolymer was also synthesized electrochemically in the presence of iodide species and the material was characterized by FT-IR spectroscopy and conductivity. The role of the dopant was studied in the process of charge transfer between the copolymer-dopant, acting in the stabilization of the species in the polymer backbone and the increase of the electronic conductivity.

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

Sequence-Dependent Mechanism of DNA Oligonucleotide Dehybridization Resolved through Infrared Spectroscopy.

Science.gov (United States)

Sanstead, Paul J; Stevenson, Paul; Tokmakoff, Andrei

2016-09-14

Despite its important role in biology and nanotechnology, many questions remain regarding the molecular mechanism and dynamics by which oligonucleotides recognize and hybridize to their complementary sequence. The thermodynamics and kinetics of DNA oligonucleotide hybridization and dehybridization are often assumed to involve an all-or-nothing two-state dissociation pathway, but deviations from this behavior can be considerable even for short sequences. We introduce a new strategy to characterize the base-pair-specific thermal dissociation mechanism of DNA oligonucleotides through steady-state and time-resolved infrared spectroscopy. Experiments are interpreted with a lattice model to provide a structure-specific interpretation. This method is applied to a model set of self-complementary 10-base-pair sequences in which the placement of GC base pairs is varied in an otherwise AT strand. Through a combination of Fourier transform infrared and two-dimensional infrared spectroscopy, experiments reveal varying degrees of deviation from simple two-state behavior. As the temperature is increased, duplexes dissociate through a path in which the terminal bases fray, without any significant contribution from loop configurations. Transient temperature jump experiments reveal time scales of 70-100 ns for fraying and 10-30 μs for complete dissociation near the melting temperature. Whether or not frayed states are metastable intermediates or short-lived configurations during the full dissociation of the duplex is dictated by the nucleobase sequence.

The TApIR experiment. IR absorption spectra of liquid hydrogen isotopologues

International Nuclear Information System (INIS)

Groessle, Robin

2015-01-01

The scope of the thesis is the infrared absorption spectroscopy of liquid hydrogen isotopologues with the tritium absorption infrared spectroscopy (TApIR) experiment at the tritium laboratory Karlsruhe (TLK). The calibration process from the sample preparation to the reference measurements are described. A further issue is the classical evaluation of FTIR absorption spectra and the extension using the rolling circle filter (RCF) including the effects on statistical and systematical errors. The impact of thermal and nuclear spin temperature on the IR absorption spectra is discussed. An empirical based modeling for the IR absorption spectra of liquid hydrogen isotopologues is performed.

An IR and XPS spectroscopy assessment of the physico-chemical surface properties of alumina–YAG nanopowders

Energy Technology Data Exchange (ETDEWEB)

Spina, Giulia; Bonelli, Barbara, E-mail: barbara.bonelli@polito.it; Palmero, Paola, E-mail: paola.palmero@polito.it; Montanaro, Laura

2013-12-16

Well-dispersed nano-crystalline transition alumina suspensions were mixed with yttrium chloride aqueous solutions, with the aim of producing by spray-drying Al{sub 2}O{sub 3}–Y{sub 3}Al{sub 5}O{sub 12} (YAG) composite powders of increasing YAG vol.%. Two samples were prepared, with different Y content, corresponding to 5 and 20 YAG vol.%, respectively. Both samples were then treated at either 600 or 1150 °C. The obtained powders were characterized by X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infra Red (FT-IR) spectroscopy and compared to three reference samples: commercial nano-crystalline transition alumina, YAG and Y{sub 2}O{sub 3}. YAG powders were obtained by co-precipitation route whereas Y{sub 2}O{sub 3} powders were yielded by spray-drying of a yttrium chloride aqueous solution. Modification of physico-chemical properties of the surface of alumina nanoparticles were assessed by combining XPS and FT-IR spectroscopies. On the basis of the results obtained, a possible model is proposed for the structure of the obtained composites, in which Y basically reacts with more acidic hydroxyls of alumina, by forming Y-rich surface grains, the extension of which depends on the thermal treatment. - Highlights: • Al{sub 2}O{sub 3}–Y{sub 3}Al{sub 5}O{sub 12} (YAG) composite nanopowders were prepared by spray drying. • Combined XPS and IR spectroscopy: effective tools to study surface modifications. • Y reacts with more acidic hydroxyls at alumina surface. • Y-rich surface grains form: their extension depends on the thermal treatment.

Gaz Phase IR and UV Spectroscopy of Neutral Contact Ion Pairs

Science.gov (United States)

Habka, Sana; Brenner, Valerie; Mons, Michel; Gloaguen, Eric

2016-06-01

Cations and anions, in solution, tend to pair up forming ion pairs. They play a crucial role in many fundamental processes in ion-concentrated solutions and living organisms. Despite their importance and vast applications in physics, chemistry and biochemistry, they remain difficult to characterize namely because of the coexistence of several types of pairing in solution. However, an interesting alternative consists in applying highly selective gas phase spectroscopy which can offer new insights on these neutral ion pairs. Our study consists in characterizing contact ion pairs (CIPs) in isolated model systems (M+, Ph-(CH2)n-COO- with M=Li, Na, K, Rb, Cs, and n=1-3), to determine their spectral signatures and compare them to ion pairs in solution. We have used laser desorption to vaporize a solid tablet containing the desired salt. Structural information for each system was obtained by mass-selective, UV and IR laser spectroscopy combined with high level quantum chemistry calculations1. Evidence of the presence of neutral CIPs was found by scanning the π-π* transition of the phenyl ring using resonant two-photon ionization (R2PI). Then, conformational selective IR/UV double resonance spectra were recorded in the CO2- stretch region for each conformation detected. The good agreement between theoretical data obtained at the BSSE-corrected-fullCCSD(T)/dhf-TZVPP//B97-D3/dhf-TZVPP level and experimental IR spectra led us to assign the 3D structure for each ion pair formed. Spectral signatures of (M+, Ph-CH2-COO-) pairs, were assigned to a bidentate CIPs between the alkali cation and the carboxylate group. In the case of (Li+, Ph-(CH2)3-COO-) pairs, the presence of a flexible side chain promotes a cation-π interaction leading to a tridentate O-O-π structure with its unique IR and UV signatures. IR spectra obtained on isolated CIPs were found very much alike the ones published on lithium and sodium acetate in solution2. However, in the case of sodium acetate, solution

Frontiers in Chemical Physics

Energy Technology Data Exchange (ETDEWEB)

Bowlan, Pamela Renee [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-05-02

These are slides dealing with frontiers in chemical physics. The following topics are covered: Time resolving chemistry with ultrashort pulses in the 0.1-40 THz spectral range; Example: Mid-infrared absorption spectrum of the intermediate state CH₂OO; Tracking reaction dynamics through changes in the spectra; Single-shot measurement of the mid-IR absorption dynamics; Applying 2D coherent mid-IR spectroscopy to learn more about transition states; Time resolving chemical reactions at a catalysis using mid-IR and THz pulses; Studying topological insulators requires a surface sensitive probe; Nonlinear phonon dynamics in Bi₂Se₃; THz-pump, SHG-probe as a surface sensitive coherent 2D spectroscopy; Nanometer and femtosecond spatiotemporal resolution mid-IR spectroscopy; Coherent two-dimensional THz/mid-IR spectroscopy with 10nm spatial resolution; Pervoskite oxides as catalysts; Functionalized graphene for catalysis; Single-shot spatiotemporal measurements; Spatiotemporal pulse measurement; Intense, broad-band THz/mid-IR generation with organic crystals.

Characterization of silicon-oxide interfaces and organic monolayers by IR-UV ellipsometry and FTIR spectroscopy

Science.gov (United States)

Hess, P.; Patzner, P.; Osipov, A. V.; Hu, Z. G.; Lingenfelser, D.; Prunici, P.; Schmohl, A.

2006-08-01

VUV-laser-induced oxidation of Si(111)-(1×1):H, Si(100):H, and a-Si:H at 157 nm (F II laser) in pure O II and pure H IIO atmospheres was studied between 30°C and 250°C. The oxidation process was monitored in real time by spectroscopic ellipsometry (NIR-UV) and FTIR spectroscopy. The ellipsometric measurements could be simulated with a three-layer model, providing detailed information on the variation of the suboxide interface with the nature of the silicon substrate surface. Besides the silicon-dioxide and suboxide layer, a dense, disordered, roughly monolayer thick silicon layer was included, as found previously by molecular dynamics calculations. The deviations from the classical Deal-Grove mechanism and the self-limited growth of the ultrathin dioxide layers (TMS) groups and n-alkylthiol monolayers on gold-coated silicon. The C-H stretching vibrations of the methylene and methyl groups could be identified by FTIR spectroscopy and IR ellipsometry.

Energy and angle resolved ion scattering spectroscopy: new possibilities for surface analysis

International Nuclear Information System (INIS)

Hellings, G.J.A.

1986-01-01

In this thesis the design and development of a novel, very sensitive and high-resolving spectrometer for surface analysis is described. This spectrometer is designed for Energy and Angle Resolved Ion Scattering Spectroscopy (EARISS). There are only a few techniques that are sensitive enough to study the outermost atomic layer of surfaces. One of these techniques, Low-Energy Ion Scattering (LEIS), is discussed in chapter 2. Since LEIS is destructive, it is important to make a very efficient use of the scattered ions. This makes it attractive to simultaneously carry out energy and angle dependent measurements (EARISS). (Auth.)

Application of two-dimensional J-resolved nuclear magnetic resonance spectroscopy to differentiation of beer

International Nuclear Information System (INIS)

Khatib, Alfi; Wilson, Erica G.; Kim, Hye Kyong; Lefeber, Alfons W.M.; Erkelens, Cornelis; Choi, Young Hae; Verpoorte, Robert

2006-01-01

A number of ingredients in beer that directly or indirectly affect its quality require an unbiased wide-spectrum analytical method that allows for the determination of a wide array of compounds for its efficient control. 1 H nuclear magnetic resonance (NMR) spectroscopy is a method that clearly meets this description as the broad range of compounds in beer is detectable. However, the resulting congestion of signals added to the low resolution of 1 H NMR spectra makes the identification of individual components very difficult. Among two-dimensional (2D) NMR techniques that increase the resolution, J-resolved NMR spectra were successfully applied to the analysis of 2-butanol extracts of beer as overlapping signals in 1 H NMR spectra were fully resolved by the additional axis of the coupling constant. Principal component analysis based on the projected J-resolved NMR spectra showed a clear separation between all of the six brands of pilsner beer evaluated in this study. The compounds responsible for the differentiation were identified by 2D NMR spectra including correlated spectroscopy and heteronuclear multiple bond correlation spectra together with J-resolved spectra. They were identified as nucleic acid derivatives (adenine, uridine and xanthine), amino acids (tyrosine and proline), organic acid (succinic and lactic acid), alcohol (tyrosol and isopropanol), cholines and carbohydrates

Picosecond Time-Resolved Temperature and Density Measurements with K-Shell Spectroscopy

Science.gov (United States)

Stillman, C. R.; Nilson, P. M.; Ivancic, S. T.; Mileham, C.; Froula, D. H.; Golovkin, I. E.

2017-10-01

The thermal x-ray emission from rapidly heated solid targets containing a buried-aluminum layer was measured to track the evolution of the bulk plasma conditions. The targets were driven by high-contrast 1 ω laser pulses at focused intensities up to 1 × 1019 W/cm2. A streaked x-ray spectrometer recorded the AlHeα and lithium-like satellite lines with 2-ps temporal resolution and moderate resolving power (E E ΔE 1000 ΔE 1000) . Time-integrated measurements over the same spectral range were used to correct the streaked data for variations in photocathode sensitivity. Linewidths and intensity ratios from the streaked data were interpreted using a collisional radiative atomic kinetics model to provide the average plasma conditions in the buried layer as a function of time. Experimental uncertainties in the measured plasma conditions are quantified within a consistent model-dependent framework. The data demonstrate the production of a 330 +/-56 eV, 0.9 +/-0.3 g/cm3 plasma that evolves slowly during peak Heα emission. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Attenuated total reflectance-FT-IR spectroscopy for gunshot residue analysis: potential for ammunition determination.

Science.gov (United States)

Bueno, Justin; Sikirzhytski, Vitali; Lednev, Igor K

2013-08-06

The ability to link a suspect to a particular shooting incident is a principal task for many forensic investigators. Here, we attempt to achieve this goal by analysis of gunshot residue (GSR) through the use of attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FT-IR) combined with statistical analysis. The firearm discharge process is analogous to a complex chemical process. Therefore, the products of this process (GSR) will vary based upon numerous factors, including the specific combination of the firearm and ammunition which was discharged. Differentiation of FT-IR data, collected from GSR particles originating from three different firearm-ammunition combinations (0.38 in., 0.40 in., and 9 mm calibers), was achieved using projection to latent structures discriminant analysis (PLS-DA). The technique was cross (leave-one-out), both internally and externally, validated. External validation was achieved via assignment (caliber identification) of unknown FT-IR spectra from unknown GSR particles. The results demonstrate great potential for ATR-FT-IR spectroscopic analysis of GSR for forensic purposes.

Real-time monitoring of airborne beryllium, at OSHA limit levels, by time-resolved laser-induced breakdown spectroscopy

International Nuclear Information System (INIS)

Radziemski, L.J.; Loree, T.R.; Cremers, D.A.

1982-01-01

Real-time detection of beryllium particulate is being investigated by the new technique of laser-induced breakdown spectroscopy. For beryllium detection we monitor the 313.1-nm feature of once ionized beryllium (Be II). Numerous publications describe the technique, our beryllium results, and other applications. Here we summarize the important points and describe our experiments with beryllium

Application of fourier-transform infrared (ft-ir) spectroscopy for determination of total phenolics of freeze dried lemon juices

International Nuclear Information System (INIS)

Sherazi, S.T.H.; Bhutto, A.A.; Mehesar, S.A.

2017-01-01

A cost effective and environmentally safe analytical method for rapid assessment of total phenolic content (TPC) in freeze dried lemon juice samples was developed using transmission Fourier-transform infrared spectroscopy (FT-IR) in conjunction with chemometric techniques. Two types of calibrations i.e. simple Beer's law and partial least square (PLS) were applied to investigate most accurate calibration model based on region from1420 to 1330 cm-1. The better analytical performance was obtained by PLS technique coefficient of determination (R2), root mean square error of calibration (RMSEC) with the value of 0.999 and 0.00864, respectively. The results of TPC in freeze dried lemon juice samples obtained by transmission FT-IR were compared with TPC observed by Folin-Ciocalteu (FC) assay and found to be comparable. Outcomes of the present study indicate that transmission FT-IR spectroscopic approach could be used as an alternative approach in place of Folin-Ciocalteu (FC) assay which is expensive and time-consuming conventional chemical methods for determination of the total phenolic content of lemon fruits. (author)

Time-resolved optical spectrometer based on a monolithic array of high-precision TDCs and SPADs

Science.gov (United States)

Tamborini, Davide; Markovic, Bojan; Di Sieno, Laura; Contini, Davide; Bassi, Andrea; Tisa, Simone; Tosi, Alberto; Zappa, Franco

2013-12-01

We present a compact time-resolved spectrometer suitable for optical spectroscopy from 400 nm to 1 μm wavelengths. The detector consists of a monolithic array of 16 high-precision Time-to-Digital Converters (TDC) and Single-Photon Avalanche Diodes (SPAD). The instrument has 10 ps resolution and reaches 70 ps (FWHM) timing precision over a 160 ns full-scale range with a Differential Non-Linearity (DNL) better than 1.5 % LSB. The core of the spectrometer is the application-specific integrated chip composed of 16 pixels with 250 μm pitch, containing a 20 μm diameter SPAD and an independent TDC each, fabricated in a 0.35 μm CMOS technology. In front of this array a monochromator is used to focus different wavelengths into different pixels. The spectrometer has been used for fluorescence lifetime spectroscopy: 5 nm spectral resolution over an 80 nm bandwidth is achieved. Lifetime spectroscopy of Nile blue is demonstrated.

Infrared spectroscopy of molecular submonolayers on surfaces by infrared scanning tunneling microscopy: tetramantane on Au111.

Science.gov (United States)

Pechenezhskiy, Ivan V; Hong, Xiaoping; Nguyen, Giang D; Dahl, Jeremy E P; Carlson, Robert M K; Wang, Feng; Crommie, Michael F

2013-09-20

We have developed a new scanning-tunneling-microscopy-based spectroscopy technique to characterize infrared (IR) absorption of submonolayers of molecules on conducting crystals. The technique employs a scanning tunneling microscope as a precise detector to measure the expansion of a molecule-decorated crystal that is irradiated by IR light from a tunable laser source. Using this technique, we obtain the IR absorption spectra of [121]tetramantane and [123]tetramantane on Au(111). Significant differences between the IR spectra for these two isomers show the power of this new technique to differentiate chemical structures even when single-molecule-resolved scanning tunneling microscopy (STM) images look quite similar. Furthermore, the new technique was found to yield significantly better spectral resolution than STM-based inelastic electron tunneling spectroscopy, and to allow determination of optical absorption cross sections. Compared to IR spectroscopy of bulk tetramantane powders, infrared scanning tunneling microscopy (IRSTM) spectra reveal narrower and blueshifted vibrational peaks for an ordered tetramantane adlayer. Differences between bulk and surface tetramantane vibrational spectra are explained via molecule-molecule interactions.

Mechanistic Insights into Growth of Surface‐Mounted Metal‐Organic Framework Films Resolved by Infrared (Nano‐) Spectroscopy

OpenAIRE

Delen, Guusje; Ristanović, Zoran; Mandemaker, Laurens D. B.; Weckhuysen, Bert M.

2017-01-01

Abstract Control over assembly, orientation, and defect‐free growth of metal‐organic framework (MOF) films is crucial for their future applications. A layer‐by‐layer approach is considered a suitable method to synthesize highly oriented films of numerous MOF topologies, but the initial stages of the film growth remain poorly understood. Here we use a combination of infrared (IR) reflection absorption spectroscopy and atomic force microscopy (AFM)‐IR imaging to investigate the assembly and gro...

Structure Determination of Unknown Organic Liquids Using NMR and IR Spectroscopy: A General Chemistry Laboratory

Science.gov (United States)

Pavel, John T.; Hyde, Erin C.; Bruch, Martha D.

2012-01-01

This experiment introduced general chemistry students to the basic concepts of organic structures and to the power of spectroscopic methods for structure determination. Students employed a combination of IR and NMR spectroscopy to perform de novo structure determination of unknown alcohols, without being provided with a list of possible…

Angle-resolved photoelectron spectroscopy of formaldehyde and methanol

Science.gov (United States)

Keller, P. R.; Taylor, J. W.; Grimm, F. A.; Carlson, Thomas A.

1984-10-01

Angle-resolved photoelectron spectroscopy was employed to obtain the angular distribution parameter, β, for the valence orbitals (IP < 21.1 eV) of formaldehyde and methanol over the 10-30 eV photon energy range using dispersed polarized synchrotron radiation as the excitation source. It was found that the energy dependence of β in the photoelectron energy range between 2 and 10 eV can be related to the molecular-orbital type from which ionization occurs. This generalized energy behavior is discussed with regard to earlier energy-dependence studies on molecules of different orbital character. Evidence is presented for the presence of resonance photoionization phenomena in formaldehyde in agreement with theoretical cross-section calculations.

Angle-resolved photoemission spectroscopy on iron-chalcogenide superconductors

Energy Technology Data Exchange (ETDEWEB)

Maletz, Janek; Zabolotnyy, Volodymyr; Evtushinsky, Daniil; Thirupathaiah, Setti; Wolter-Giraud, Anja; Harnagea, Luminita; Kordyuk, Alexander; Borisenko, Sergey [IFW Dresden (Germany); Yaresko, Alexander [MPI-FKF, Stuttgart (Germany); Vasiliev, Alexander [Moscow State University (Russian Federation); Chareev, Dimitri [RAS, Chernogolovka (Russian Federation); Rienks, Emile [Helmholtz-Zentrum Berlin (Germany); Buechner, Bernd [IFW Dresden (Germany); TU Dresden (Germany); Shermadini, Zurab; Luetkens, Hubertus; Sedlak, Kamil; Khasanov, Rustem; Amato, Alex; Krzton-Maziopa, Anna; Conder, Kazimierz; Pomjakushina, Ekaterina [Paul Scherrer Institute (Switzerland); Klauss, Hans-Henning [TU Dresden (Germany)

2014-07-01

The electronic structure of the iron chalcogenide superconductors FeSe{sub 1-x} and Rb{sub 0.77}Fe{sub 1.61}Se{sub 2} was investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES). The results were compared to DFT calculations and μSR measurements. Both compounds share ''cigar-shaped'' Fermi surface sheets in their electronic structure, that can be found in almost all iron-pnictide superconductors. These features originate from a strong interplay of two hole- and electron-like bands in the Brillouin zone center, leading to a pronounced singularity in the density of states just below the Fermi level. This facilitates the coupling to a bosonic mode responsible for superconductivity.

Amplifier with time-invariant trapezoidal shaping and shape-sensitive pileup rejector for high-rate spectroscopy

International Nuclear Information System (INIS)

Drndarevic, V.; Ryge, P.; Gozani, T.

1989-01-01

An amplifier with trapezoidal pulse shaping was developed for high-rate high-energy gamma spectroscopy using NaI(T1) scintillation detectors. It employs a double delay-line technique for producing a nearly triangular pulse shape combined with a linear circuit for producing a flattopped pulse. Good energy resolution and short resolving time make this amplifier especially suitable for high count rate gamma ray spectroscopy. To provide a versatile high-performance system, it includes a pileup rejector based on inspection of a pileup signal obtained by combining the slow output signal and fast-shaped input signal. The trapezoidal shape provides a short resolving time for minimal occurrence of pileup with a width suitable for presentation to a standard multichannel analyzer. The performance of the system was tested, and the results are presented

Time-resolved 3D pulmonary perfusion MRI: comparison of different k-space acquisition strategies at 1.5 and 3 T.

Science.gov (United States)

Attenberger, Ulrike I; Ingrisch, Michael; Dietrich, Olaf; Herrmann, Karin; Nikolaou, Konstantin; Reiser, Maximilian F; Schönberg, Stefan O; Fink, Christian

2009-09-01

Time-resolved pulmonary perfusion MRI requires both high temporal and spatial resolution, which can be achieved by using several nonconventional k-space acquisition techniques. The aim of this study is to compare the image quality of time-resolved 3D pulmonary perfusion MRI with different k-space acquisition techniques in healthy volunteers at 1.5 and 3 T. Ten healthy volunteers underwent contrast-enhanced time-resolved 3D pulmonary MRI on 1.5 and 3 T using the following k-space acquisition techniques: (a) generalized autocalibrating partial parallel acquisition (GRAPPA) with an internal acquisition of reference lines (IRS), (b) GRAPPA with a single "external" acquisition of reference lines (ERS) before the measurement, and (c) a combination of GRAPPA with an internal acquisition of reference lines and view sharing (VS). The spatial resolution was kept constant at both field strengths to exclusively evaluate the influences of the temporal resolution achieved with the different k-space sampling techniques on image quality. The temporal resolutions were 2.11 seconds IRS, 1.31 seconds ERS, and 1.07 VS at 1.5 T and 2.04 seconds IRS, 1.30 seconds ERS, and 1.19 seconds VS at 3 T.Image quality was rated by 2 independent radiologists with regard to signal intensity, perfusion homogeneity, artifacts (eg, wrap around, noise), and visualization of pulmonary vessels using a 3 point scale (1 = nondiagnostic, 2 = moderate, 3 = good). Furthermore, the signal-to-noise ratio in the lungs was assessed. At 1.5 T the lowest image quality (sum score: 154) was observed for the ERS technique and the highest quality for the VS technique (sum score: 201). In contrast, at 3 T images acquired with VS were hampered by strong artifacts and image quality was rated significantly inferior (sum score: 137) compared with IRS (sum score: 180) and ERS (sum score: 174). Comparing 1.5 and 3 T, in particular the overall rating of the IRS technique (sum score: 180) was very similar at both field

Time-resolved cathodoluminescence microscopy with sub-nanosecond beam blanking for direct evaluation of the local density of states

NARCIS (Netherlands)

Moerland, R.J.; Weppelman, I.G.C.; Garming, M.W.H.; Kruit, P.; Hoogenboom, J.P.

2016-01-01

We show cathodoluminescence-based time-resolved electron beam spectroscopy in order to directly probe the spontaneous emission decay rate that is modified by the local density of states in a nanoscale environment. In contrast to dedicated laser-triggered electron-microscopy setups, we use commercial

Continuous wave and time resolved spectroscopy of InAsN/GaAsN based quantum dots

International Nuclear Information System (INIS)

Taliercio, T.; Valvin, P.; Intartaglia, R.; Guillet, T.; Lefebvre, P.; Bretagnon, T.; Gil, B.; Sallet, V.; Harmand, J.C.

2005-01-01

We present a study of the optical properties of quantum dots based on a new family of semiconductors: III-V dilute nitrides such as (In,Ga)(N,As). Continuous wave and time resolved photoluminescence (PL) experiments allowed us to evaluate the impact of N incorporation during the growth of InAs/GaAs quantum dots. Previous work [V. Sallet et al., to be submitted to J. Cryst. Growth (2005); O. Schumann et al., J. Appl. Phys. 96, 2832 (2004)] showed that increasing the flux of N atoms into the growth chamber modifies drastically the size of the dots which leads to a bimodal growth. Two populations of dots with different sizes appear. The quantum dot PL line broadens and a second PL line appears at higher energy. Time resolved PL allows us to identify the nature of this second PL line: second population of quantum dots. A second decay time is observed which we interpret as being the consequence of the perturbation of the electronic states of the quantum dots. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Solid-phase nano-extraction and laser-excited time-resolved Shpol'skii spectroscopy for the analysis of polycyclic aromatic hydrocarbons in drinking water samples.

Science.gov (United States)

Wang, Huiyong; Yu, Shenjiang; Campiglia, Andres D

2009-02-15

A unique method for screening polycyclic aromatic hydrocarbons in drinking water samples is reported. Water samples (500 microl) are mixed and centrifuged with 950 microl of a commercial solution of 20 nm gold nanoparticles for pollutants extraction. The precipitate is treated with 2 microl of 1-pentanethiol and 48 microl of n-octane, and the supernatant is then analyzed via laser-excited time-resolved Shpol'skii spectroscopy. Fifteen priority pollutants are directly determined at liquid helium temperature (4.2 K) with the aid of a cryogenic fiber-optic probe. Unambiguous pollutant determination is carried out via spectral and lifetime analysis. Limits of detection are at the parts-per-trillion level. Analytical recoveries are similar to those obtained via high-performance liquid chromatography. The simplicity of the experimental procedure, use of microliters of organic solvent, short analysis time, selectivity, and excellent analytical figures of merit demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.

Spatially resolved sulfur K-edge XANES spectroscopy of wheat leaves infected by Puccinia triticina

International Nuclear Information System (INIS)

Lichtenberg, H; Prange, A; Hormes, J; Steiner, U; Oerke, E-C

2009-01-01

In this study, wheat leaves infected with brown rust, a plant disease of serious economic concern caused by the fungus Puccinia triticina, were investigated using spatially resolved XANES (X-ray Absorption Near Edge Structure) spectroscopy at the sulfur K-absorption edge.

Spatially resolved sulfur K-edge XANES spectroscopy of wheat leaves infected by Puccinia triticina

Energy Technology Data Exchange (ETDEWEB)

Lichtenberg, H; Prange, A; Hormes, J [CAMD, Louisiana State University, 6980 Jefferson Hwy, Baton Rouge, LA 70806 (United States); Steiner, U; Oerke, E-C, E-mail: lichtenberg@lsu.ed [INRES-Phytomedicine, University of Bonn, Nussallee 9, 53115 Bonn (Germany)

2009-11-15

In this study, wheat leaves infected with brown rust, a plant disease of serious economic concern caused by the fungus Puccinia triticina, were investigated using spatially resolved XANES (X-ray Absorption Near Edge Structure) spectroscopy at the sulfur K-absorption edge.

Identification and characterization of salmonella serotypes using DNA spectral characteristics by fourier transform infrared (FT-IR) spectroscopy

Science.gov (United States)

Analysis of DNA samples of Salmonella serotypes (Salmonella Typhimurium, Salmonella Enteritidis, Salmonella Infantis, Salmonella Heidelberg and Salmonella Kentucky) were performed using Fourier transform infrared spectroscopy (FT-IR) spectrometer by placing directly in contact with a diamond attenua...

Space-resolved vacuum ultra-violet spectroscopy on T.F.R. Tokamak plasmas

International Nuclear Information System (INIS)

1978-01-01

Results are reported of space-resolved vacuum-ultraviolet spectroscopy (between 100 A and 2000A) on T.F.R. Tokamak plasmas and examples are given of profiles for both heavy and light impurity ions. The experimental method and the associated uncertainties and problems are stressed. The great importance of numerical calculations in the interpretation of the impurity profiles is pointed out. (author)

Study on high-silicon boron-containing zeolite by thermogravimetric and IR-spectroscopy techniques

International Nuclear Information System (INIS)

Chukin, G.D.; Nefedov, B.K.; Surin, S.A.; Polinina, E.V.; Khusid, B.L.; Sidel'kovskaya, V.G.

1985-01-01

The structure identity of initial Na-forms of boron-containing and aluminosilicate high-silicon zeolites is established by thermogravimetric and IR-spectroscopy methods. The presence of boron in Na-forms of high-silicon zeolites is shown to lead to reduction of structure thermal stability. It is noted that thermal stability of the H-form of both high-silicon boron-containing and boron-free zeolites is practically equal and considerably higher than that of Na-forms

Detection and classification of salmonella serotypes using spectral signatures collected by fourier transform infrared (FT-IR) spectroscopy

Science.gov (United States)

Spectral signatures of Salmonella serotypes namely Salmonella Typhimurium, Salmonella Enteritidis, Salmonella Infantis, Salmonella Heidelberg and Salmonella Kentucky were collected using Fourier transform infrared spectroscopy (FT-IR). About 5-10 µL of Salmonella suspensions with concentrations of 1...

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.

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...

Numerical simulations of time-resolved quantum electronics

International Nuclear Information System (INIS)

Gaury, Benoit; Weston, Joseph; Santin, Matthieu; Houzet, Manuel; Groth, Christoph; Waintal, Xavier

2014-01-01

Numerical simulation has become a major tool in quantum electronics both for fundamental and applied purposes. While for a long time those simulations focused on stationary properties (e.g. DC currents), the recent experimental trend toward GHz frequencies and beyond has triggered a new interest for handling time-dependent perturbations. As the experimental frequencies get higher, it becomes possible to conceive experiments which are both time-resolved and fast enough to probe the internal quantum dynamics of the system. This paper discusses the technical aspects–mathematical and numerical–associated with the numerical simulations of such a setup in the time domain (i.e. beyond the single-frequency AC limit). After a short review of the state of the art, we develop a theoretical framework for the calculation of time-resolved observables in a general multiterminal system subject to an arbitrary time-dependent perturbation (oscillating electrostatic gates, voltage pulses, time-varying magnetic fields, etc.) The approach is mathematically equivalent to (i) the time-dependent scattering formalism, (ii) the time-resolved non-equilibrium Green’s function (NEGF) formalism and (iii) the partition-free approach. The central object of our theory is a wave function that obeys a simple Schrödinger equation with an additional source term that accounts for the electrons injected from the electrodes. The time-resolved observables (current, density, etc.) and the (inelastic) scattering matrix are simply expressed in terms of this wave function. We use our approach to develop a numerical technique for simulating time-resolved quantum transport. We find that the use of this wave function is advantageous for numerical simulations resulting in a speed up of many orders of magnitude with respect to the direct integration of NEGF equations. Our technique allows one to simulate realistic situations beyond simple models, a subject that was until now beyond the simulation

Developments in time-resolved x-ray research at APS beamline 7ID

Energy Technology Data Exchange (ETDEWEB)

Walko, D. A., E-mail: d-walko@anl.gov; Adams, B. W.; Doumy, G.; Dufresne, E. M.; Li, Yuelin; March, A. M.; Sandy, A. R.; Wang, Jin; Wen, Haidan; Zhu, Yi [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States)

2016-07-27

The 7ID beamline of the Advanced Photon Source (APS) is dedicated to time-resolved research using x-ray imaging, scattering, and spectroscopy techniques. Time resolution is achieved via gated detectors and/or mechanical choppers in conjunction with the time structure of the x-ray beam. Three experimental hutches allow for a wide variety of experimental setups. Major areas of research include atomic, molecular, and optical physics; chemistry; condensed matter physics in the bulk, thin film, and surface regimes; and fluid-spray dynamics. Recent developments in facilities at 7ID include a high-power, high-repetition-rate picosecond laser to complement the 1 kHz ultrafast laser. For the ultrafast laser, a newly commissioned optical parametric amplifier provides pump wavelength from 0.2 to 15 µm with energy per pulse up to 200 µJ. A nanodiffraction station has also been commissioned, using Fresnel zone-plate optics to achieve a focused x-ray spot of 300 nm. This nanoprobe is not only used to spatially resolve the evolution of small features in samples after optical excitation, but also has been combined with an intense THz source to study material response under ultrafast electric fields.

Applications of a table-top time-resolved luminescence spectrometer with nanosecond soft X-ray pulse excitation

Czech Academy of Sciences Publication Activity Database

Brůža, P.; Pánek, D.; Fidler, V.; Benedikt, P.; Čuba, V.; Gbur, T.; Boháček, Pavel; Nikl, Martin

2014-01-01

Roč. 61, č. 1 (2014), s. 448-451 ISSN 0018-9499 R&D Projects: GA ČR GA13-09876S Institutional support: RVO:68378271 Keywords : LiCaAlF 6 * luminescence * scintillators * soft x-ray * SrHfO 3 * time-resolved spectroscopy * ZnO :Ga Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.283, year: 2014

Novel lanthanide doped micro- and mesoporous solids. Characterization of ion-host-interactions, species distribution and luminescence properties using time-resolved luminescence spectroscopy

International Nuclear Information System (INIS)

Gessner, Andre

2010-12-01

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 5 D 0 - 7 F 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 mesopores. Lanthanide ions located here, are

Impact of Humidity on Quartz-Enhanced Photoacoustic Spectroscopy Based CO Detection Using a Near-IR Telecommunication Diode Laser

Directory of Open Access Journals (Sweden)

Xukun Yin

2016-01-01

Full Text Available A near-IR CO trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS is evaluated using humidified nitrogen samples. Relaxation processes in the CO-N2-H2O system are investigated. A simple kinetic model is used to predict the sensor performance at different gas pressures. The results show that CO has a ~3 and ~5 times slower relaxation time constant than CH4 and HCN, respectively, under dry conditions. However, with the presence of water, its relaxation time constant can be improved by three orders of magnitude. The experimentally determined normalized detection sensitivity for CO in humid gas is 1.556 × 10 − 8   W ⋅ cm − 1 / Hz 1 / 2 .

Raman and IR-ATR spectroscopy studies of heteroepitaxial structures with a GaN:C top layer

Science.gov (United States)

Cerqueira, M. F.; Vieira, L. G.; Alves, A.; Correia, R.; Huber, M.; Andreev, A.; Bonanni, A.; Vasilevskiy, M. I.

2017-09-01

This work, motivated by the technologically important task of determination of carbon dopant location in the GaN crystal lattice, employed Raman spectroscopy, with both resonant and non-resonant excitation, and infrared (IR) spectroscopy, in the attenuated total reflection (ATR) configuration, to study lattice vibration modes in a set of carbon-doped GaN (GaN:C) epilayers grown by metalorganic vapour phase epitaxy. We analyse Raman and IR-ATR spectra from the point of view of possible effects of the carbon doping, namely: (i) local vibration mode of C atoms in the nitrogen sublattice (whose frequency we theoretically estimate as 768 cm-1 using an isotope defect model), and (ii) shift in the positions of longitudinal modes owing to the phonon-plasmon coupling. We find only indirect hints of the doping effect on the resonant Raman spectra. However, we show theoretically and confirm experimentally that the IR-ATR spectroscopy can be a much more sensitive tool for this purpose, at least for the considered structures. A weak perturbation of the dielectric function of GaN:C, caused by the substitutional carbon impurity, is shown to produce a measurable dip in the ATR reflectivity spectra at  ≈770 cm-1 for both p- and s-polarizations. Moreover, it influences a specific (guided-wave type) mode observed at  ≈737 cm-1, originating from the GaN layer, which appears in the narrow frequency window where the real parts of the two components of the dielectric tensor of the hexagonal crystal have opposite signs. This interpretation is supported by our modelling of the whole multilayer structure, using a transfer matrix formalism.

Comparative investigation of Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) in the determination of cotton fiber crystallinity.

Science.gov (United States)

Liu, Yongliang; Thibodeaux, Devron; Gamble, Gary; Bauer, Philip; VanDerveer, Don

2012-08-01

Despite considerable efforts in developing curve-fitting protocols to evaluate the crystallinity index (CI) from X-ray diffraction (XRD) measurements, in its present state XRD can only provide a qualitative or semi-quantitative assessment of the amounts of crystalline or amorphous fraction in a sample. The greatest barrier to establishing quantitative XRD is the lack of appropriate cellulose standards, which are needed to calibrate the XRD measurements. In practice, samples with known CI are very difficult to prepare or determine. In a previous study, we reported the development of a simple algorithm for determining fiber crystallinity information from Fourier transform infrared (FT-IR) spectroscopy. Hence, in this study we not only compared the fiber crystallinity information between FT-IR and XRD measurements, by developing a simple XRD algorithm in place of a time-consuming and subjective curve-fitting process, but we also suggested a direct way of determining cotton cellulose CI by calibrating XRD with the use of CI(IR) as references.

Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

Energy Technology Data Exchange (ETDEWEB)

Lastras-Martínez, A., E-mail: alm@cactus.iico.uaslp.mx, E-mail: alastras@gmail.com; Ortega-Gallegos, J.; Guevara-Macías, L. E.; Nuñez-Olvera, O.; Balderas-Navarro, R. E.; Lastras-Martínez, L. F. [Instituto de Investigación en Comunicación Optica, Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, San Luis Potosí, SLP 78000 (Mexico); Lastras-Montaño, L. A. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Lastras-Montaño, M. A. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California 93106 (United States)

2014-03-01

We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

Real-time visualization of the vibrational wavepacket dynamics in electronically excited pyrimidine via femtosecond time-resolved photoelectron imaging

Science.gov (United States)

Li, Shuai; Long, Jinyou; Ling, Fengzi; Wang, Yanmei; Song, Xinli; Zhang, Song; Zhang, Bing

2017-07-01

The vibrational wavepacket dynamics at the very early stages of the S1-T1 intersystem crossing in photoexcited pyrimidine is visualized in real time by femtosecond time-resolved photoelectron imaging and time-resolved mass spectroscopy. A coherent superposition of the vibrational states is prepared by the femtosecond pump pulse at 315.3 nm, resulting in a vibrational wavepacket. The composition of the prepared wavepacket is directly identified by a sustained quantum beat superimposed on the parent-ion transient, possessing a frequency in accord with the energy separation between the 6a1 and 6b2 states. The dephasing time of the vibrational wavepacket is determined to be 82 ps. More importantly, the variable Franck-Condon factors between the wavepacket components and the dispersed cation vibrational levels are experimentally illustrated to identify the dark state and follow the energy-flow dynamics on the femtosecond time scale. The time-dependent intensities of the photoelectron peaks originated from the 6a1 vibrational state exhibit a clear quantum beating pattern with similar periodicity but a phase shift of π rad with respect to those from the 6b2 state, offering an unambiguous picture of the restricted intramolecular vibrational energy redistribution dynamics in the 6a1/6b2 Fermi resonance.

Time-resolved studies. Ch. 9

International Nuclear Information System (INIS)

Mills, Dennis M.; Argonne National Lab., IL

1991-01-01

Synchrotron radiation, with its unique properties, offers 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. Wide-bandpass 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 'parallel data collection' 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 data-collection time. Perhaps the most exciting advances in time-resolved X-ray studies will be made by those methods that exploit the pulsed nature of the radiation emitted from storage rings. Pulsed techniques have had an enormous impact in the study of the temporal evolution of transient phenomena. The extension from continuous to modulated sources for use in time-resolved work has been carried over in a host of fields that use both pulsed particle and pulsed electro-magnetic beams. In this chapter the new experimental techniques are reviewed and illustrated with some experiments. (author). 98 refs.; 20 figs.; 5 tabs

β-Isocyanoalanine as an IR probe: comparison of vibrational dynamics between isonitrile and nitrile-derivatized IR probes.

Science.gov (United States)

Maj, Michał; Ahn, Changwoo; Kossowska, Dorota; Park, Kwanghee; Kwak, Kyungwon; Han, Hogyu; Cho, Minhaeng

2015-05-07

An infrared (IR) probe based on isonitrile (NC)-derivatized alanine 1 was synthesized and the vibrational properties of its NC stretching mode were investigated using FTIR and femtosecond IR pump-probe spectroscopy. It is found that the NC stretching mode is very sensitive to the hydrogen-bonding ability of solvent molecules. Moreover, its transition dipole strength is larger than that of nitrile (CN) in nitrile-derivatized IR probe 2. The vibrational lifetime of the NC stretching mode is found to be 5.5 ± 0.2 ps in both D2O and DMF solvents, which is several times longer than that of the azido (N3) stretching mode in azido-derivatized IR probe 3. Altogether these properties suggest that the NC group can be a very promising sensing moiety of IR probes for studying the solvation structure and dynamics of biomolecules.

Deflection evaluation using time-resolved radiography

International Nuclear Information System (INIS)

Fry, D.A.; Lucero, J.P.

1990-01-01

Time-resolved radiography is the creation of an x-ray image for which both the start-exposure and stop-exposure times are known with respect to the event under study. The combination of image and timing are used to derive information about the event. The authors have applied time-resolved radiography to evaluate motions of explosive-driven events. In the particular application discussed in this paper, the author's intent is to measure maximum deflections of the components involved. Exposures are made during the time just before to just after the event of interest occurs. A smear or blur of motion out to its furthest extent is recorded on the image. Comparison of the dynamic images with static images allows deflection measurements to be made

Rutile IrO2/TiO2 superlattices: A hyperconnected analog to the Ruddelsden-Popper structure

Science.gov (United States)

Kawasaki, Jason K.; Baek, David; Paik, Hanjong; Nair, Hari P.; Kourkoutis, Lena F.; Schlom, Darrell G.; Shen, Kyle M.

2018-05-01

Dimensionality and connectivity among octahedra play important roles in determining the properties, electronic structure, and phase transitions of transition-metal oxides. Here we demonstrate the epitaxial growth of (110)-oriented alternating layers of IrO2 and TiO2, both of which have the rutile structure. These (IrO2)n/(TiO2)2 superlattices consist of IrO6 and TiO6 octahedra tiled in a hyperconnected, edge- and corner-sharing network. Despite the large lattice mismatch between constituent layers (Δ d∥=-2.1 % and Δ c =+6.6 % ), our reactive molecular-beam epitaxy-grown superlattices show high structural quality as determined by x-ray diffraction and sharp interfaces as observed by transmission electron microscopy. The large strain at the interface is accommodated by an ordered interfacial reconstruction. The superlattices show persistent metallicity down to n =3 atomic layers, and angle-resolved photoemission spectroscopy measurements reveal quantized sub-bands with signatures of IrO2-IrO2 interlayer coupling.

[A new measurement method of time-resolved spectrum].

Science.gov (United States)

Shi, Zhi-gang; Huang, Shi-hua; Liang, Chun-jun; Lei, Quan-sheng

2007-02-01

A new method for measuring time-resolved spectrum (TRS) is brought forward. Programming with assemble language controlled the micro-control-processor (AT89C51), and a kind of peripheral circuit constituted the drive circuit, which drived the stepping motor to run the monochromator. So the light of different kinds of expected wavelength could be obtained. The optical signal was transformed to electrical signal by optical-to-electrical transform with the help of photomultiplier tube (Hamamatsu 1P28). The electrical signal of spectrum data was transmitted to the oscillograph. Connecting the two serial interfaces of RS232 between the oscillograph and computer, the electrical signal of spectrum data could be transmitted to computer for programming to draw the attenuation curve and time-resolved spectrum (TRS) of the swatch. The method for measuring time-resolved spectrum (TRS) features parallel measurement in time scale but serial measurement in wavelength scale. Time-resolved spectrum (TRS) and integrated emission spectrum of Tb3+ in swatch Tb(o-BBA)3 phen were measured using this method. Compared with the real time-resolved spectrum (TRS). It was validated to be feasible, credible and convenient. The 3D spectra of fluorescence intensity-wavelength-time, and the integrated spectrum of the swatch Tb(o-BBA)3 phen are given.

Using FT-IR Spectroscopy to Elucidate the Structures of Ablative Polymers

Science.gov (United States)

Fan, Wendy

2011-01-01

The composition and structure of an ablative polymer has a multifaceted influence on its thermal, mechanical and ablative properties. Understanding the molecular level information is critical to the optimization of material performance because it helps to establish correlations with the macroscopic properties of the material, the so-called structure-property relationship. Moreover, accurate information of molecular structures is also essential to predict the thermal decomposition pathways as well as to identify decomposition species that are fundamentally important to modeling work. In this presentation, I will describe the use of infrared transmission spectroscopy (FT-IR) as a convenient tool to aid the discovery and development of thermal protection system materials.

New approaches for a time- and position-resolved detector for positron annihilation spectroscopy at PLEPS

Energy Technology Data Exchange (ETDEWEB)

Ackermann, Ulrich; Egger, Werner; Sperr, Peter; Loewe, Benjamin; Ravelli, Luca; Koegel, Gottfried; Dollinger, Guenther [Universitaet der Bundeswehr Muenchen, LRT2 (Germany); Jagutzki, Ottmar [Universitaet Frankfurt, RoentDek GmbH (Germany)

2013-07-01

The pulsed low energy positron system PLEPS at NEPOMUC at the FRM II is a tool for depth resolved positron lifetime measurements. Besides positron lifetime measurements 2D-AMOC (two dimensional age momentum correlation) experiments are also possible. 2D-AMOC provides in coincidence the lifetime of the positron and the longitudinal momentum distribution of the annihilating electron. It would be of great scientific concern to measure simultaneously the entire 3D-momentum distribution of the annihilating electron and the corresponding lifetime of the positron (4D-AMOC). To perform 4D-AMOC measurements, a time and spatially resolving detector with a time resolution of about 100 ps (FWHM) and a spatial resolution of circa 2 mm over an area of about 12 cm{sup 2} is required in coincidence with a pixelated Ge-detector and currently under development at our institute. It is intended to use a MCP-based UV-light detector with two MCP-stages coupled to a BaF{sub 2} scintillator. To achieve the spatial resolution the centroid information of the photoelectron-cloud is detected with a position sensitive anode installed outside the housing of the MCP detector. As an alternative to a MCP-based detector, silicon photomultipliers are also envisaged.

Time-Resolved Soft X-ray Diffraction Reveals Transient Structural Distortions of Ternary Liquid Crystals

Directory of Open Access Journals (Sweden)

Klaus Mann

2009-11-01

Full Text Available Home-based soft X-ray time-resolved scattering experiments with nanosecond time resolution (10 ns and nanometer spatial resolution were carried out at a table top soft X-ray plasma source (2.2–5.2 nm. The investigated system was the lyotropic liquid crystal C16E7/paraffin/glycerol/formamide/IR 5. Usually, major changes in physical, chemical, and/or optical properties of the sample occur as a result of structural changes and shrinking morphology. Here, these effects occur as a consequence of the energy absorption in the sample upon optical laser excitation in the IR regime. The liquid crystal shows changes in the structural response within few hundred nanoseconds showing a time decay of 182 ns. A decrease of the Bragg peak diffracted intensity of 30% and a coherent macroscopic movement of the Bragg reflection are found as a response to the optical pump. The Bragg reflection movement is established to be isotropic and diffusion controlled (1 μs. Structural processes are analyzed in the Patterson analysis framework of the time-varying diffraction peaks revealing that the inter-lamellar distance increases by 2.7 Å resulting in an elongation of the coherently expanding lamella crystallite. The present studies emphasize the possibility of applying TR-SXRD techniques for studying the mechanical dynamics of nanosystems.

Time-resolved studies at PETRA III with a highly repetitive synchronized laser system

Energy Technology Data Exchange (ETDEWEB)

Schlie, Mortiz

2013-09-15

Atomic and molecular processes can nowadays be directly followed in the time domain. This is a core technique for a better understanding of the involved fundamental physics, thus auguring new applications in the future as well. Usually the so-called pump-probe technique making use of two synchronized ultrashort light pulses is utilized to obtain this time-resolved data. In this work, the development and characterization of a synchronization system enabling such pump-probe studies at the storage ring PETRA III in combination with an external, then synchronized fs-laser system is described. The synchronization is based on an extended PLL approach with three interconnected feedback loops allowing to monitor short-time losses of the lock and thus prevent them. This way, the jitter between the laser PHAROS and the PETRA III reference signal is reduced to {sigma} <5 ps. Thus the system allows to conduct experiments at a repetition rate of 130 kHz with a temporal resolution limited only by the X-ray pulse length. A major emphasis in the fundamental introductory chapters is an intuitive explanation of the basic principles of phase locked loops and the different aspects of phase noise to allow a deeper understanding of the synchronization. Furthermore, first pump-probe experiments conducted at different beamlines at PETRA III are presented, demonstrating the usability of the laser system in a scientific environment as well. In first characterizing experiments the pulse duration of PETRA III X-ray pulses has been measured to be 90 ps FWHM. In particular, there have been time resolved X-ray absorption spectroscopy experiments on Gaq3 and Znq2 conducted at beamline P11. First results show dynamics of the electronic excitation on the timescale of a few hundred pico seconds up to a few nano seconds and provide a basic understanding for further research on those molecules. For Gaq3 this data is analyzed in detail and compared with visible fluorescence measurements suggesting at

Time-resolved studies at PETRA III with a highly repetitive synchronized laser system

International Nuclear Information System (INIS)

Schlie, Mortiz

2013-09-01

Atomic and molecular processes can nowadays be directly followed in the time domain. This is a core technique for a better understanding of the involved fundamental physics, thus auguring new applications in the future as well. Usually the so-called pump-probe technique making use of two synchronized ultrashort light pulses is utilized to obtain this time-resolved data. In this work, the development and characterization of a synchronization system enabling such pump-probe studies at the storage ring PETRA III in combination with an external, then synchronized fs-laser system is described. The synchronization is based on an extended PLL approach with three interconnected feedback loops allowing to monitor short-time losses of the lock and thus prevent them. This way, the jitter between the laser PHAROS and the PETRA III reference signal is reduced to σ <5 ps. Thus the system allows to conduct experiments at a repetition rate of 130 kHz with a temporal resolution limited only by the X-ray pulse length. A major emphasis in the fundamental introductory chapters is an intuitive explanation of the basic principles of phase locked loops and the different aspects of phase noise to allow a deeper understanding of the synchronization. Furthermore, first pump-probe experiments conducted at different beamlines at PETRA III are presented, demonstrating the usability of the laser system in a scientific environment as well. In first characterizing experiments the pulse duration of PETRA III X-ray pulses has been measured to be 90 ps FWHM. In particular, there have been time resolved X-ray absorption spectroscopy experiments on Gaq3 and Znq2 conducted at beamline P11. First results show dynamics of the electronic excitation on the timescale of a few hundred pico seconds up to a few nano seconds and provide a basic understanding for further research on those molecules. For Gaq3 this data is analyzed in detail and compared with visible fluorescence measurements suggesting at least

FT-IR reflection spectra of single crystals: resolving phonons of different symmetry without using polarised radiation

Directory of Open Access Journals (Sweden)

METODIJA NAJDOSKI

2000-07-01

Full Text Available Fourier-transform infrared (FT-IR reflection spectra, asquired at nearnormal incidence, were recorded from single crystals belonging to six crystal systems: CsCr(SO42.12H2O (alum, cubic, K2CuCl2·2H2O (Mitscherlichite, tetragonal, CaCO3 (calcite, hexagonal, KHSO4 (mercallite, orthorhombic, CaSO4·2H2O (gypsum, monoclinic and CuSO4·5H2O (chalcantite, triclinic. The acquired IR reflection spectra were further transformed into absorption spectra, employing the Kramers-Kronig transformation. Except for the cubic alums, the spectra strongly depend on the crystal face from which they were recorded; this is a consequence of anisotropy. Phonons of a given symmetry (E-species, in tetragonal/hexagonal and B-species, in monoclinic crystals may be resolved without using a polariser. The spectrum may be simplified in the case of an orthorhombic crystal, as well. The longitudinal-optical (LO and transversal-optical (TO mode frequencies were calculated in the case of optically isotropic and the simplified spectra of optically uniaxial crystals.

Direct observation of superconducting gaps in MgB 2 by angle-resolved photoemission spectroscopy

Science.gov (United States)

Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J. C.; Sasaki, S.; Kadowaki, K.

2004-08-01

High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2. We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2.

Direct observation of superconducting gaps in MgB2 by angle-resolved photoemission spectroscopy

International Nuclear Information System (INIS)

Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J.C.; Sasaki, S.; Kadowaki, K.

2004-01-01

High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2 . We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2

Combining FT-IR spectroscopy and multivariate analysis for qualitative and quantitative analysis of the cell wall composition changes during apples development.

Science.gov (United States)

Szymanska-Chargot, M; Chylinska, M; Kruk, B; Zdunek, A

2015-01-22

The aim of this work was to quantitatively and qualitatively determine the composition of the cell wall material from apples during development by means of Fourier transform infrared (FT-IR) spectroscopy. The FT-IR region of 1500-800 cm(-1), containing characteristic bands for galacturonic acid, hemicellulose and cellulose, was examined using principal component analysis (PCA), k-means clustering and partial least squares (PLS). The samples were differentiated by development stage and cultivar using PCA and k-means clustering. PLS calibration models for galacturonic acid, hemicellulose and cellulose content from FT-IR spectra were developed and validated with the reference data. PLS models were tested using the root-mean-square errors of cross-validation for contents of galacturonic acid, hemicellulose and cellulose which was 8.30 mg/g, 4.08% and 1.74%, respectively. It was proven that FT-IR spectroscopy combined with chemometric methods has potential for fast and reliable determination of the main constituents of fruit cell walls. Copyright © 2014 Elsevier Ltd. All rights reserved.

Time-resolved X-ray absorption spectroscopy for laser-ablated silicon particles in xenon gas

International Nuclear Information System (INIS)

Makimura, Tetsuya; Sakuramoto, Tamaki; Murakami, Kouichi

1996-01-01

We developed a laboratory-scale in situ apparatus for soft X-ray absorption spectroscopy with a time resolution of 10 ns and a space resolution of 100 μm. Utilizing this spectrometer, we have investigated the dynamics of silicon atoms formed by laser ablation in xenon gas. It was found that 4d-electrons in the xenon atoms are excited through collision with electrons in the laser-generated silicon plasma. (author)

Weak carbonyl-methyl intermolecular interactions in acetone clusters explored by IR plus VUV spectroscopy

International Nuclear Information System (INIS)

Guan, Jiwen; Hu, Yongjun; Xie, Min; Bernstein, Elliot R.

2012-01-01

Highlights: ► The carbonyl overtone of acetone clusters is observed by IR-VUV spectroscopy. ► Acetone molecules in the dimer are stacked with an antiparallel way. ► The structure of the acetone trimer and the tetramer are the cyclic structures. ► The carbonyl groups would interact with the methyl groups in acetone clusters. ► These weak interactions are further confirmed by H/D substitution experiment. -- Abstract: Size-selected IR–VUV spectroscopy is employed to detect vibrational characteristics in the region 2850 ∼ 3550 cm −1 of neutral acetone and its clusters (CH 3 COCH 3 ) n (n = 1–4). Features around 3440 cm −1 in the spectra of acetone monomer and its clusters are assigned to the carbonyl stretch (CO) overtone. These features red-shift from 3455 to 3433 cm −1 as the size of the clusters increases from the monomer to the tetramer. Based on calculations, the experimental IR spectra in the C=O overtone region suggest that the dominant structures for the acetone trimer and tetramer should be cyclic in the supersonic expansion sample. This study also suggests that the carbonyl groups interact with the methyl groups in the acetone clusters. These weak interactions are further confirmed by the use of deuterium substitution.

Time-resolved photoluminescence of Ga(NAsP) multiple quantum wells grown on Si substrate: Effects of rapid thermal annealing

Energy Technology Data Exchange (ETDEWEB)

Woscholski, R., E-mail: ronja.woscholski@physik.uni-marburg.de; Shakfa, M.K.; Gies, S.; Wiemer, M.; Rahimi-Iman, A.; Zimprich, M.; Reinhard, S.; Jandieri, K.; Baranovskii, S.D.; Heimbrodt, W.; Volz, K.; Stolz, W.; Koch, M.

2016-08-31

Time-resolved photoluminescence (TR-PL) spectroscopy has been used to study the impact of rapid thermal annealing (RTA) on the optical properties and carrier dynamics in Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates. TR-PL measurements reveal an enhancement in the PL efficiency when the RTA temperature is increased up to 925 °C. Then, the PL intensity dramatically decreases with the annealing temperature. This behavior is explained by the variation of the disorder degree in the studied structures. The analysis of the low-temperature emission-energy-dependent PL decay time enables us to characterize the disorder in the Ga(NAsP) MQWHs. The theoretically extracted energy-scales of disorder confirm the experimental observations. - Highlights: • Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates • Impact of rapid thermal annealing on the optical properties and carrier dynamics • Time resolved photoluminescence spectroscopy was applied. • PL transients became continuously faster with increasing annealing temperature. • Enhancement in the PL efficiency with increasing annealing temperature up to 925 °C.

Time-resolved photoluminescence of Ga(NAsP) multiple quantum wells grown on Si substrate: Effects of rapid thermal annealing

International Nuclear Information System (INIS)

Woscholski, R.; Shakfa, M.K.; Gies, S.; Wiemer, M.; Rahimi-Iman, A.; Zimprich, M.; Reinhard, S.; Jandieri, K.; Baranovskii, S.D.; Heimbrodt, W.; Volz, K.; Stolz, W.; Koch, M.

2016-01-01

Time-resolved photoluminescence (TR-PL) spectroscopy has been used to study the impact of rapid thermal annealing (RTA) on the optical properties and carrier dynamics in Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates. TR-PL measurements reveal an enhancement in the PL efficiency when the RTA temperature is increased up to 925 °C. Then, the PL intensity dramatically decreases with the annealing temperature. This behavior is explained by the variation of the disorder degree in the studied structures. The analysis of the low-temperature emission-energy-dependent PL decay time enables us to characterize the disorder in the Ga(NAsP) MQWHs. The theoretically extracted energy-scales of disorder confirm the experimental observations. - Highlights: • Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates • Impact of rapid thermal annealing on the optical properties and carrier dynamics • Time resolved photoluminescence spectroscopy was applied. • PL transients became continuously faster with increasing annealing temperature. • Enhancement in the PL efficiency with increasing annealing temperature up to 925 °C

Time-resolved emission from laser-ablated uranium

International Nuclear Information System (INIS)

Stoffels, E.; Mullen, J. van der; Weijer, P. van de

1991-01-01

Time-resolved emission spectra from the plasma, induced by laser ablation of uranium samples have been studied. The dependence of the emission intensity on time is strongly affected by the nature and pressure of the buffer gas. Air and argon have been used in the pressure range 0.002 to 5 mbar. The emission intensity as a function of time displays three maxima, indicating that three different processes within the expanding plasma plume are involved. On basis of the time-resolved spectra we propose a model that explains qualitatively the phenomena that are responsible for this time behaviour. (author)

An x-ray detector for time-resolved studies

International Nuclear Information System (INIS)

Rodricks, B.; Brizard, C.; Clarke, R.; Lowe, W.

1992-01-01

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

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.

Site-Specific Measurement of Water Dynamics in the Substrate Pocket of Ketosteroid Isomerase Using Time-Resolved Vibrational Spectroscopy

Science.gov (United States)

Jha, Santosh Kumar; Ji, Minbiao; Gaffney, Kelly J.; Boxer, Steven G.

2012-01-01

Little is known about the reorganization capacity of water molecules at the active sites of enzymes and how this couples to the catalytic reaction. Here, we study the dynamics of water molecules at the active site of a highly proficient enzyme, Δ5-3-ketosteroid isomerase (KSI), during a light-activated mimic of its catalytic cycle. Photo-excitation of a nitrile containing photo-acid, coumarin183 (C183), mimics the change in charge density that occurs at the active site of KSI during the first step of the catalytic reaction. The nitrile of C183 is exposed to water when bound to the KSI active site, and we used time-resolved vibrational spectroscopy as a site-specific probe to study the solvation dynamics of water molecules in the vicinity of the nitrile. We observed that water molecules at the active site of KSI are highly rigid, during the light-activated catalytic cycle, compared to the solvation dynamics observed in bulk water. Based upon this result we hypothesize that rigid water dipoles at the active site might help in the maintenance of the pre-organized electrostatic environment required for efficient catalysis. The results also demonstrate the utility of nitrile probes in measuring the dynamics of local (H-bonded) water molecules in contrast to the commonly used fluorescence methods which measure the average behavior of primary and subsequent spheres of solvation. PMID:22931297

Photodissociation of gaseous CH3COSH at 248 nm by time-resolved Fourier-transform infrared emission spectroscopy: Observation of three dissociation channels

International Nuclear Information System (INIS)

Hu, En-Lan; Tsai, Po-Yu; Fan, He; Lin, King-Chuen

2013-01-01

Upon one-photon excitation at 248 nm, gaseous CH 3 C(O)SH is dissociated following three pathways with the products of (1) OCS + CH 4 , (2) CH 3 SH + CO, and (3) CH 2 CO + H 2 S that are detected using time-resolved Fourier-transform infrared emission spectroscopy. The excited state 1 (n O , π * CO ) has a radiative lifetime of 249 ± 11 ns long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of collision-induced internal conversion is estimated to be 1.1 × 10 −10 cm 3 molecule −1 s −1 . Among the primary dissociation products, a fraction of the CH 2 CO moiety may undergo further decomposition to CH 2 + CO, of which CH 2 is confirmed by reaction with O 2 producing CO 2 , CO, OH, and H 2 CO. Such a secondary decomposition was not observed previously in the Ar matrix-isolated experiments. The high-resolution spectra of CO are analyzed to determine the ro-vibrational energy deposition of 8.7 ± 0.7 kcal/mol, while the remaining primary products with smaller rotational constants are recognized but cannot be spectrally resolved. The CO fragment detected is mainly ascribed to the primary production. A prior distribution method is applied to predict the vibrational distribution of CO that is consistent with the experimental findings.

Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

Directory of Open Access Journals (Sweden)

A. Lastras-Martínez

2014-03-01

Full Text Available We report on real time-resolved Reflectance-difference (RD spectroscopy of GaAs(001 grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

Matrix isolation FT-IR spectroscopy and molecular orbital study of sarcosine methyl ester

OpenAIRE

Gómez-Zavaglia, Andrea; Fausto, R.

2004-01-01

N-methylglycine methyl ester (sarcosine-Me) has been studied by matrix isolation FT-IR spectroscopy and molecular orbital calculations undertaken at the DFT/B3LYP and MP2 levels of theory with the 6-311++G(d,p) and 6-31++G(d,p) basis set, respectively. Twelve different conformers were located in the potential energy surface of the studied compound, with the ASC conformer being the ground conformational state. This form is analogous to the dimethylglycine methyl ester most stable conformer and...

Time-resolved laser-excited Shpol'skii spectrometry with a fiber-optic probe and ICCD camera

International Nuclear Information System (INIS)

Bystol, Adam J.; Campiglia, Andres D.; Gillispie, Gregory D.

2000-01-01

Improved methodology for chemical analysis via laser-excited Shpol'skii spectrometry is reported. The complications of traditional methodology for measurements at liquid nitrogen temperature are avoided by freezing the distal end of a bifurcated fiber-optic probe directly into the sample matrix. Emission wavelength-time matrices were rapidly collected by automatically incrementing the gate delay of an intensified charge-coupled device (ICCD) camera relative to the laser excitation pulse. The excitation source is a compact frequency-doubled tunable dye laser whose bandwidth (<0.03 nm) is well matched for Shpol'skii spectroscopy. Data reproducibility for quantitative analysis purposes and analytical figures of merit are demonstrated for several polycyclic aromatic hydrocarbons at 77 K. Although not attempted in this study, time-resolved excitation-emission matrices could easily be collected with this instrumental system. (c) 2000 Society for Applied Spectroscopy

Nanosecond retinal structure changes in K-590 during the room-temperature bacteriorhodopsin photocycle: picosecond time-resolved coherent anti-stokes Raman spectroscopy

OpenAIRE

Weidlich, O.; Ujj, L.; Jäger, F.; Atkinson, G.H.

1997-01-01

Time-resolved vibrational spectra are used to elucidate the structural changes in the retinal chromophore within the K-590 intermediate that precedes the formation of the L-550 intermediate in the room-temperature (RT) bacteriorhodopsin (BR) photocycle. Measured by picosecond time-resolved coherent anti-Stokes Raman scattering (PTR/CARS), these vibrational data are recorded within the 750 cm-1 to 1720 cm-1 spectral region and with time delays of 50-260 ns after the RT/BR photocycle is optical...

Discrimination of edible oils and fats by combination of multivariate pattern recognition and FT-IR spectroscopy: A comparative study between different modeling methods

Science.gov (United States)

Javidnia, Katayoun; Parish, Maryam; Karimi, Sadegh; Hemmateenejad, Bahram

2013-03-01

By using FT-IR spectroscopy, many researchers from different disciplines enrich the experimental complexity of their research for obtaining more precise information. Moreover chemometrics techniques have boosted the use of IR instruments. In the present study we aimed to emphasize on the power of FT-IR spectroscopy for discrimination between different oil samples (especially fat from vegetable oils). Also our data were used to compare the performance of different classification methods. FT-IR transmittance spectra of oil samples (Corn, Colona, Sunflower, Soya, Olive, and Butter) were measured in the wave-number interval of 450-4000 cm-1. Classification analysis was performed utilizing PLS-DA, interval PLS-DA, extended canonical variate analysis (ECVA) and interval ECVA methods. The effect of data preprocessing by extended multiplicative signal correction was investigated. Whilst all employed method could distinguish butter from vegetable oils, iECVA resulted in the best performances for calibration and external test set with 100% sensitivity and specificity.

Development of a method for determination of fatty acid using FT-IR spectroscopy

Directory of Open Access Journals (Sweden)

Dimas Augusto Morozin Zaia

2011-05-01

Full Text Available In the present paper a new methodology has been developed for determination of fatty acids in biological systems using FT-IR spectroscopy. For this method is not necessary chromophore reagent or pre sample preparation. Palmitic acid was chosen as standard, because it is found in several biological systems. The FT-IR spectrum of palmitic acid showed two absorption bands in the region of 2852 and 2920 cm-1 attributed to CH stretching. The results for these bands showed that the Beer-Lambert Law was followed in wide range of concentration of palmitic acid (14 to 257 mmol L-1. Potassium ferricyanide (K3[Fe(CN6] was used as internal standard. Several interferents were tested and only cholesterol, ferric chloride (higher concentration, mixture of amino acids for the band at 2919 cm-1 (higher concentration and triglyceride could be interferent if they appear in high concentration. Thus, this new methodology has advantage to be not expensive and simple.

A Polarization-Adjustable Picosecond Deep-Ultraviolet Laser for Spin- and Angle-Resolved Photoemission Spectroscopy

International Nuclear Information System (INIS)

Zhang Feng-Feng; Yang Feng; Zhang Shen-Jin; Wang Zhi-Min; Xu Feng-Liang; Peng Qin-Jun; Zhang Jing-Yuan; Xu Zu-Yan; Wang Xiao-Yang; Chen Chuang-Tian

2012-01-01

We report on a polarization-adjustable picosecond deep-ultraviolet (DUV) laser at 177.3 nm. The DUV laser was produced by second harmonic generation from a mode-locked laser at 355 nm in nonlinear optical crystal KBBF. The laser delivered a maximum average output power of 1.1 mW at 177.3 nm. The polarization of the 177.3 nm beam was adjusted with linear and circular polarization by means of λ/4 and λ/2 wave plates. To the best of our knowledge, the laser has been employed as the circularly polarized and linearly polarized DUV light source for a spin- and angle-resolved photoemission spectroscopy with high resolution for the first time. (fundamental areas of phenomenology(including applications))

Spatially resolved positron annihilation spectroscopy on friction stir weld induced defects.

Science.gov (United States)

Hain, Karin; Hugenschmidt, Christoph; Pikart, Philip; Böni, Peter

2010-04-01

A friction stir welded (FSW) Al alloy sample was investigated by Doppler broadening spectroscopy (DBS) of the positron annihilation line. The spatially resolved defect distribution showed that the material in the joint zone becomes completely annealed during the welding process at the shoulder of the FSW tool, whereas at the tip, annealing is prevailed by the deterioration of the material due to the tool movement. This might be responsible for the increased probability of cracking in the heat affected zone of friction stir welds. Examination of a material pairing of steel S235 and the Al alloy Silafont36 by coincident Doppler broadening spectroscopy (CDBS) indicates the formation of annealed steel clusters in the Al alloy component of the sample. The clear visibility of Fe in the CDB spectra is explained by the very efficient trapping at the interface between steel cluster and bulk.

Real time observation of proteolysis with Fourier transform infrared (FT-IR) and UV-circular dichroism spectroscopy: Watching a protease eat a protein

Science.gov (United States)

Güler, Günnur; Džafić, Enela; Vorob'ev, Mikhail M.; Vogel, Vitali; Mäntele, Werner

2011-06-01

Fourier transform infrared (FT-IR)- and UV-circular dichroism (UV-CD) spectroscopy have been used to study real-time proteolytic digestion of β-lactoglobulin (β-LG) and β-casein (β-CN) by trypsin at various substrate/enzyme ratios in D 2O-buffer at 37 °C. Both techniques confirm that protein substrate looses its secondary structure upon conversion to the peptide fragments. This perturbation alters the backbone of the protein chain resulting in conformational changes and degrading of the intact protein. Precisely, the most significant spectral changes which arise from digestion take place in the amide I and amide II regions. The FT-IR spectra for the degraded β-LG show a decrease around 1634 cm -1, suggesting a decrease of β-sheet structure in the course of hydrolysis. Similarly, the intensity around the 1654 cm -1 band decreases for β-CN digested by trypsin, indicating a reduction in the α-helical part. On the other hand, the intensity around ˜1594 cm -1 and ˜1406 cm -1 increases upon enzymatic breakdown of both substrates, suggesting an increase in the antisymmetric and symmetric stretching modes of free carboxylates, respectively, as released digestion products. Observation of further H/D exchange in the course of digestion manifests the structural opening of the buried groups and accessibility to the core of the substrate. On the basis of the UV-CD spectra recorded for β-LG and β-CN digested by trypsin, the unordered structure increases concomitant with a decrease in the remaining structure, thus, revealing breakdown of the intact protein into smaller fragments. This model study in a closed reaction system may serve as a basis for the much more complex digestion processes in an open reaction system such as the stomach.

Metalation of positively charged water soluble mesoporphyrins studied via time-resolved SERRS spectroscopy

Science.gov (United States)

Procházka, Marek; Hanzliková, Jana; Štěpánek, Josef; Baumruk, Vladimir

1997-06-01

Time-resolved SERRS spectra of 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]21 H,23 H-porphine (TMAP) were recorded (using a multichannel Raman spectrometer) in various SERS-active Ag colloid/porphyrin systems. Data treatment based on a factor analysis was used to decompose all the SERRS spectra into two main components: SERRS spectrum of the free base TMAP and that of its Ag metalated form. The metalation kinetics obtained in this way was found to be highly dependent on the presence of phosphate anions, citrate and/or Triton X-100 in the colloidal system. The results are analogous to those previously obtained for 5,10,15,20-tetrakis(1-methyl-4-pyridyl)21 H,23 H-porphine, a porphyrin with a substantially stronger tendency towards metalation.

Simple methods via Mid-IR or {sup 1}H NMR spectroscopy for the determination of the iodine value of vegetable oils

Energy Technology Data Exchange (ETDEWEB)

Shimamoto, Gustavo G.; Favaro, Martha M.A.; Tubino, Matthieu, E-mail: tubino@iqm.unicamp.br [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Instituto de Química

2015-07-01

Two methods for determining the iodine value in vegetable oils are described. One employs mid-infrared (mid-IR) spectroscopy and the other uses hydrogen nuclear magnetic resonance ({sup 1}H NMR). The determination of the iodine value is based on either the transmittance intensity of mid-IR signals or on the {sup 1}H NMR signal integration and multivariate calibration. Both of the methods showed adequate coefficients of determination (r{sup 2} = 0.9974 and 0.9978, respectively) when compared to Wijs method, which is recommended by the norm EN 14111. A statistical comparison between the results from the proposed methods and from Wijs method shows that both instrumental methods offer equivalent results and greater precision compared to Wijs method. The regressions obtained from the constructed models were considered statistically significant and useful for making predictions. The proposed methods present several advantages compared to Wijs method because they significantly reduce analysis time, reagent consumption and waste generation. Furthermore, an analyst can choose between the mid-IR or {sup 1}H NMR to determine the iodine value. (author)

Study of the deuterated albumin by FT-IR spectroscopy

International Nuclear Information System (INIS)

Stoenescu, Daniela; Sahini, V.E.

2000-01-01

The albumin is a protein from the soluble or corpuscular protein class, which exists in cells, in dissolved state or in form of a hydrated gel. Proteins are essential constituents beside water, inorganic salts, lipids, carbon hydrates, vitamins, enzymes. The albumin is also a protein soluble in water and in diluted electrolyte solutions (acids, bases and salts). The investigation of the vibration isotopic effect has a great importance both for the diatomic molecules and for the polyatomic molecules. This paper is the first from a series of works which are intended to study the physico-chemical properties of the deuterated albumin and of the albumin solutions in heavy water by an isotopic exchange method. To put in evidence H-D exchange, the FT-IR spectroscopy is used when the deuterated albumin has different layer thickness. It is also of interest to elucidate the isotopic exchange between the hydrogen and oxygen atoms in bovine serum albumin macromolecules. (authors)

Rapid discrimination of sea buckthorn berries from different H. rhamnoides subspecies by multi-step IR spectroscopy coupled with multivariate data analysis

Science.gov (United States)

Liu, Yue; Zhang, Ying; Zhang, Jing; Fan, Gang; Tu, Ya; Sun, Suqin; Shen, Xudong; Li, Qingzhu; Zhang, Yi

2018-03-01

As an important ethnic medicine, sea buckthorn was widely used to prevent and treat various diseases due to its nutritional and medicinal properties. According to the Chinese Pharmacopoeia, sea buckthorn was originated from H. rhamnoides, which includes five subspecies distributed in China. Confusion and misidentification usually occurred due to their similar morphology, especially in dried and powdered forms. Additionally, these five subspecies have vital differences in quality and physiological efficacy. This paper focused on the quick classification and identification method of sea buckthorn berry powders from five H. rhamnoides subspecies using multi-step IR spectroscopy coupled with multivariate data analysis. The holistic chemical compositions revealed by the FT-IR spectra demonstrated that flavonoids, fatty acids and sugars were the main chemical components. Further, the differences in FT-IR spectra regarding their peaks, positions and intensities were used to identify H. rhamnoides subspecies samples. The discrimination was achieved using principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA). The results showed that the combination of multi-step IR spectroscopy and chemometric analysis offered a simple, fast and reliable method for the classification and identification of the sea buckthorn berry powders from different H. rhamnoides subspecies.

Evaluation of Turmeric Powder Adulterated with Metanil Yellow Using FT-Raman and FT-IR Spectroscopy

Directory of Open Access Journals (Sweden)

Sagar Dhakal

2016-05-01

Full Text Available Turmeric powder (Curcuma longa L. is valued both for its medicinal properties and for its popular culinary use, such as being a component in curry powder. Due to its high demand in international trade, turmeric powder has been subject to economically driven, hazardous chemical adulteration. This study utilized Fourier Transform-Raman (FT-Raman and Fourier Transform-Infra Red (FT-IR spectroscopy as separate but complementary methods for detecting metanil yellow adulteration of turmeric powder. Sample mixtures of turmeric powder and metanil yellow were prepared at concentrations of 30%, 25%, 20%, 15%, 10%, 5%, 1%, and 0.01% (w/w. FT-Raman and FT-IR spectra were acquired for these mixture samples as well as for pure samples of turmeric powder and metanil yellow. Spectral analysis showed that the FT-IR method in this study could detect the metanil yellow at the 5% concentration, while the FT-Raman method appeared to be more sensitive and could detect the metanil yellow at the 1% concentration. Relationships between metanil yellow spectral peak intensities and metanil yellow concentration were established using representative peaks at FT-Raman 1406 cm−1 and FT-IR 1140 cm−1 with correlation coefficients of 0.93 and 0.95, respectively.

Secondary Structures in Phe-Containing Isolated Dipeptide Chains: Laser Spectroscopy vs Quantum Chemistry.

Science.gov (United States)

Loquais, Yohan; Gloaguen, Eric; Habka, Sana; Vaquero-Vara, Vanesa; Brenner, Valérie; Tardivel, Benjamin; Mons, Michel

2015-06-11

The intrinsic conformational landscape of two phenylalanine-containing protein chain models (-Gly-Phe- and -Ala-Phe- sequences) has been investigated theoretically and experimentally in the gas phase. The near UV spectroscopy (first ππ* transition of the Phe ring) is obtained experimentally under jet conditions where the conformational features can be resolved. Single-conformation IR spectroscopy in the NH stretch region is then obtained by IR/UV double resonance in the ground state, leading to resolved vibrational spectra that are assigned in terms of conformation and H-bonding content from comparison with quantum chemistry calculations. For the main conformer, whose UV spectrum exhibits a significant Franck-Condon activity in low frequency modes involving peptide backbone motions relative to the Phe chromophore, excited state IR spectroscopy has also been recorded in a UV/IR/UV experiment. The NH stretch spectral changes observed in such a ππ* labeling experiment enable us to determine those NH bonds that are coupled to the phenyl ring; they are compared to CC2 excited state calculations to quantify the geometry change upon ππ* excitation. The complete and consistent series of data obtained enable us to propose an unambiguous assignment for the gallery of conformers observed and to demonstrate that, in these two sequences, three conceptually important local structural motifs of proteins (β-strands, 27 ribbons, and β-turns) are represented. The satisfactory agreement between the experimental conformational distribution and the predicted landscape anticipated from the DFT-D approach demonstrates the capabilities of a theoretical method that accounts for dispersive interactions. It also shows that the flaws, inherent to a resonant two-photon ionization detection scheme, often evoked for aromatic chromophores, do not seem to be significant in the case of Phe.

NMR and IR Spectroscopy for the Structural Characterization of Edible Fats and Oils: An Instrumental Analysis Laboratory

Science.gov (United States)

Crowther, Molly W.

2008-01-01

This article describes an upper-level instrumental laboratory for undergraduates that explores the complementary nature of IR and NMR spectroscopy for analysis of several edible fats and oils that are structurally similar but differ in physical properties and health implications. Five different fats and oils are analyzed for average chain length,…

Direct observation of superconducting gaps in MgB{sub 2} by angle-resolved photoemission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J.C.; Sasaki, S.; Kadowaki, K

2004-08-01

High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB{sub 2}. We observed three bands crossing the Fermi level, which are ascribed to B2p-{sigma}, {pi} and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of {sigma} and surface bands are 6.5 {+-} 0.5 and 6.0 {+-} 0.5 meV, respectively, while that of the {pi} band is much smaller (1.5 {+-} 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB{sub 2}.

Discrimination of Chinese Sauce liquor using FT-IR and two-dimensional correlation IR spectroscopy

Science.gov (United States)

Sun, Su-Qin; Li, Chang-Wen; Wei, Ji-Ping; Zhou, Qun; Noda, Isao

2006-11-01

We applied the three-step IR macro-fingerprint identification method to obtain the IR characteristic fingerprints of so-called Chinese Sauce liquor (Moutai liquor and Kinsly liquor) and a counterfeit Moutai. These fingerprints can be used for the identification and discrimination of similar liquor products. The comparison of their conventional IR spectra, as the first step of identification, shows that the primary difference in Sauce liquor is the intensity of characteristic peaks at 1592 and 1225 cm -1. The comparison of the second derivative IR spectra, as the second step of identification, shows that the characteristic absorption in 1400-1800 cm -1 is substantially different. The comparison of 2D-IR correlation spectra, as the third and final step of identification, can discriminate the liquors from another direction. Furthermore, the method was successfully applied to the discrimination of a counterfeit Moutai from the genuine Sauce liquor. The success of the three-step IR macro-fingerprint identification to provide a rapid and effective method for the identification of Chinese liquor suggests the potential extension of this technique to the identification and discrimination of other wine and spirits, as well.

Multidimensional high harmonic spectroscopy

International Nuclear Information System (INIS)

Bruner, Barry D; Soifer, Hadas; Shafir, Dror; Dudovich, Nirit; Serbinenko, Valeria; Smirnova, Olga

2015-01-01

High harmonic generation (HHG) has opened up a new frontier in ultrafast science where attosecond time resolution and Angstrom spatial resolution are accessible in a single measurement. However, reconstructing the dynamics under study is limited by the multiple degrees of freedom involved in strong field interactions. In this paper we describe a new class of measurement schemes for resolving attosecond dynamics, integrating perturbative nonlinear optics with strong-field physics. These approaches serve as a basis for multidimensional high harmonic spectroscopy. Specifically, we show that multidimensional high harmonic spectroscopy can measure tunnel ionization dynamics with high precision, and resolves the interference between multiple ionization channels. In addition, we show how multidimensional HHG can function as a type of lock-in amplifier measurement. Similar to multi-dimensional approaches in nonlinear optical spectroscopy that have resolved correlated femtosecond dynamics, multi-dimensional high harmonic spectroscopy reveals the underlying complex dynamics behind attosecond scale phenomena. (paper)

Vibrational spectroscopy of proteins

International Nuclear Information System (INIS)

Schwaighofer, A.

2013-01-01

Two important steps for the development of a biosensor are the immobilization of the biological component (e.g. protein) on a surface and the enhancement of the signal to improve the sensitivity of detection. To address these subjects, the present work describes Fourier transform infrared (FTIR) investigations of several proteins bound to the surface of an attenuated total reflection (ATR) crystal. Furthermore, new nanostructured surfaces for signal enhancement were developed for use in FTIR microscopy. The mitochondrial redox-protein cytochrome c oxidase (CcO) was incorporated into a protein-tethered bilayer lipid membrane (ptBLM) on an ATR crystal featuring a roughened two-layer gold surface for signal enhancement. Electrochemical excitation by periodic potential pulses at different modulation frequencies was followed by time-resolved FTIR spectroscopy. Phase sensitive detection was used for deconvolution of the IR spectra into vibrational components. A model based on protonation-dependent chemical reaction kinetics could be fitted to the time evolution of IR bands attributed to several different redox centers of the CcO. Further investigations involved the odorant binding protein 14 (OBP14) of the honey bee (Apis mellifera), which was studied using ATR-FTIR spectroscopy and circular dichroism. OBP14 was found to be thermally stable up to 45 °C, thus permitting the potential application of this protein for the fabrication of biosensors. Thermal denaturation measurements showed that odorant binding increases the thermal stability of the OBP-odorant complex. In another project, plasmonic nanostructures were fabricated that enhance the absorbance in FTIR microscopy measurements. The nanostructures are composed of an array of round-shaped insulator and gold discs on top of a continuous gold layer. Enhancement factors of up to ⁓125 could be observed with self-assembled monolayers of dodecanethiol molecules immobilized on the gold surface (author) [de

Application of Fourier transform infrared (FT-IR) spectroscopy to the study of the modification of epoxidized sunflower oil by acrylation.

Science.gov (United States)

Irinislimane, Ratiba; Belhaneche-Bensemra, Naima

2012-12-01

Commercial sunflower oil was epoxidized at the laboratory-scale. The epoxidized sunflower oil (ESFO) was modified following the acrylation reaction. Modification was carried out simultaneously using acrylic acid (AA) and triethylamine (TEA). To optimize the reaction conditions, the effects of four temperatures (40, 60, 80, and 100 °C), the ESFO:AA (100:100) ratio, and 0.2% TEA were investigated. The rate of conversion was analyzed with both FT-IR and titration of the oxirane ring. After that, the temperature with the highest conversion was selected and used throughout for all modification reactions. Then, four ratios (100:100, 100:90, 100:80, and 100:75) of ESFO:AA were analyzed at four different concentrations of TEA (0.2, 0.3, 0.4, and 0.5%) to determine the best estimate for both the ESFO:AA ratio and the catalyst concentration. Conversion rate was analyzed using FT-IR spectroscopy by measuring the concentrations of ester, carbonyl, and alcohol groups. Moreover, oxirane-ring concentration was estimated using the titration method (with gentian violet as indicator) and FT-IR spectroscopy (epoxy ring absorptions at 1270 cm(-1) and 877 cm(-1)). Based on conversion yield, the optimum ESFO:AA ratio corresponds to 100:80; the best temperature reaction was at 60 °C, and the best TEA concentration was 0.2%. The critical amounts of reactants needed to reach maximum conversion were established. The final acid value of the acrylated ESFO after washing (pH = 7) was 2.1 mg potassium hydroxide (KOH)·g(-1). All results show that FT-IR spectroscopy is a simple, low-cost, rapid method for investigating the kinetics of a reaction.

Femtosecond time-resolved two-photon photoemission study of organic semiconductor copper phthalocyanine film

International Nuclear Information System (INIS)

Tanaka, A.; Tohoku University; University of Rochester, NY; Yan, L.; Watkins, N.J.; Gao, Y.

2004-01-01

Full text: Organic semiconductors are recently attracting much interest from the viewpoints of both device and fundamental physics. These organic semiconductors are considered to be important constituents of the future devices, such as organic light-emitting diode, organic field effect transistor, and organic solid-state injection laser. In order to elucidate their detailed physical properties and to develop the future devices, it is indispensable to understand their excited-state dynamics as well as their electronic structures. The femtosecond time-resolved two-photon photoemission (TR-2PPE) spectroscopy is attracting much interest because of its capability to observe the energy-resolved excited electron dynamics. In this work, we have carried out a TR-2PPE study of the organic semiconductor copper phthalocyanine (CuPc) film. Furthermore, we have investigated the detailed electronic structure of CuPc film using the photoemission (PES) and inverse photoemission (IPES) spectroscopies. From the simultaneous PES and IPES measurements for CuPc film with a thickness of 100 nm, the lowest unoccupied molecular orbital (LUMO), highest occupied molecular orbital, and ionization potential of CuPc film have been directly determined. The observed two-photon photoemission (2PPE) spectrum of the present CuPc film, measured with photon energy of about hv=3.3 eV, exhibits a broad feature. From the energy diagram of CuPc film determined by the PES and IPES measurements, the intermediate state observed in the present 2PPE spectrum of CuPc film corresponds to the energy region between about 0.4 and 1.7 eV above the LUMO energy. From the time-resolved pump-probe measurements, it is found that the relaxation lifetimes of excited states in the present CuPc films are very short (all below 50 fs) and monotonously become faster with increasing excitation energy. We attribute this extremely fast relaxation process of photoexcitation to a rapid internal conversion process. From these results

Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test

Directory of Open Access Journals (Sweden)

Tahereh-Sadat Jafarzadeh

2015-12-01

Full Text Available Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm. Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-μm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan was performed at the top and bottom (depth=2 mm surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness.

Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test.

Science.gov (United States)

Jafarzadeh, Tahereh-Sadat; Erfan, Mohammad; Behroozibakhsh, Marjan; Fatemi, Mostafa; Masaeli, Reza; Rezaei, Yashar; Bagheri, Hossein; Erfan, Yasaman

2015-01-01

Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR) spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm). Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length) were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-μm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan) was performed at the top and bottom (depth=2 mm) surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness.

Time-resolved photoion imaging spectroscopy: Determining energy distribution in multiphoton absorption experiments

Science.gov (United States)

Qian, D. B.; Shi, F. D.; Chen, L.; Martin, S.; Bernard, J.; Yang, J.; Zhang, S. F.; Chen, Z. Q.; Zhu, X. L.; Ma, X.

2018-04-01

We propose an approach to determine the excitation energy distribution due to multiphoton absorption in the case of excited systems following decays to produce different ion species. This approach is based on the measurement of the time-resolved photoion position spectrum by using velocity map imaging spectrometry and an unfocused laser beam with a low fluence and homogeneous profile. Such a measurement allows us to identify the species and the origin of each ion detected and to depict the energy distribution using a pure Poisson's equation involving only one variable which is proportional to the absolute photon absorption cross section. A cascade decay model is used to build direct connections between the energy distribution and the probability to detect each ionic species. Comparison between experiments and simulations permits the energy distribution and accordingly the absolute photon absorption cross section to be determined. This approach is illustrated using C60 as an example. It may therefore be extended to a wide variety of molecules and clusters having decay mechanisms similar to those of fullerene molecules.

Development of C-lignin with G/S-lignin and lipids in orchid seed coats – an unexpected diversity exposed by ATR-FT-IR spectroscopy

DEFF Research Database (Denmark)

Barsberg, Søren Talbro; Lee, Y.-I.; Rasmussen, Hanne Nina

2018-01-01

Cite this article: Barsberg ST, Lee Y-I, Rasmussen HN. Development of C-lignin with G/S-lignin and lipids in orchid seed coats – an unexpected diversity exposed by ATR-FT-IR spectroscopy. Seed Science Research https:// doi.org/10.1017/S0960258517000344......Cite this article: Barsberg ST, Lee Y-I, Rasmussen HN. Development of C-lignin with G/S-lignin and lipids in orchid seed coats – an unexpected diversity exposed by ATR-FT-IR spectroscopy. Seed Science Research https:// doi.org/10.1017/S0960258517000344...

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...... lifetime, allowing the detection of an ultrafast change in bulk solvent density. An analysis approach directly utilizing the spectroscopic data in the XDS analysis effectively reduces the number of free parameters, and both combined permit extraction of information about the ultrafast structural dynamics...

Highly Stable, All-fiber, High Power ZBLAN Supercontinuum Source Reaching 4.75 µm used for Nanosecond mid-IR Spectroscopy

DEFF Research Database (Denmark)

Moselund, Peter M.; Petersen, Christian; Leick, Lasse

2013-01-01

We demonstrate compact all-fiber mid-IR supercontinuum generation up to 4.75 μm with 1.2 W output power during hundreds of hours. This source is applied to upconversion spectroscopy using the energy corresponding to a single pulse....

Efficient calculation of open quantum system dynamics and time-resolved spectroscopy with distributed memory HEOM (DM-HEOM).

Science.gov (United States)

Kramer, Tobias; Noack, Matthias; Reinefeld, Alexander; Rodríguez, Mirta; Zelinskyy, Yaroslav

2018-06-11

Time- and frequency-resolved optical signals provide insights into the properties of light-harvesting molecular complexes, including excitation energies, dipole strengths and orientations, as well as in the exciton energy flow through the complex. The hierarchical equations of motion (HEOM) provide a unifying theory, which allows one to study the combined effects of system-environment dissipation and non-Markovian memory without making restrictive assumptions about weak or strong couplings or separability of vibrational and electronic degrees of freedom. With increasing system size the exact solution of the open quantum system dynamics requires memory and compute resources beyond a single compute node. To overcome this barrier, we developed a scalable variant of HEOM. Our distributed memory HEOM, DM-HEOM, is a universal tool for open quantum system dynamics. It is used to accurately compute all experimentally accessible time- and frequency-resolved processes in light-harvesting molecular complexes with arbitrary system-environment couplings for a wide range of temperatures and complex sizes. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

FT-IR spectroscopy: A powerful tool for studying the inter- and intraspecific biodiversity of cultivable non-Saccharomyces yeasts isolated from grape must.

Science.gov (United States)

Grangeteau, Cédric; Gerhards, Daniel; Terrat, Sebastien; Dequiedt, Samuel; Alexandre, Hervé; Guilloux-Benatier, Michèle; von Wallbrunn, Christian; Rousseaux, Sandrine

2016-02-01

The efficiency of the FT-IR technique for studying the inter- and intra biodiversity of cultivable non-Saccharomyces yeasts (NS) present in different must samples was examined. In first, the capacity of the technique FT-IR to study the global diversity of a given sample was compared to the pyrosequencing method, used as a reference technique. Seven different genera (Aureobasidium, Candida, Cryptococcus, Hanseniaspora, Issatchenkia, Metschnikowia and Pichia) were identified by FT-IR and also by pyrosequencing. Thirty-eight other genera were identified by pyrosequencing, but together they represented less than 6% of the average total population of 6 musts. Among the species identified, some of them present organoleptic potentials in winemaking, particularly Starmerella bacillaris (synonym Candidazemplinina). So in a second time, we evaluated the capacity of the FT-IR technique to discriminate the isolates of this species because few techniques were able to study intraspecific NS yeast biodiversity. The results obtained were validated by using a classic method as ITS sequencing. Biodiversity at strain level was high: 19 different strains were identified from 58 isolates. So, FT-IR spectroscopy seems to be an accurate and reliable method for identifying major genera present in the musts. The two biggest advantages of the FT-IR are the capacity to characterize intraspecific biodiversity of non-Saccharomyces yeasts and the possibility to discriminate a lot of strains. Copyright © 2015 Elsevier B.V. All rights reserved.

Low pressure-induced secondary structure transitions of regenerated silk fibroin in its wet film studied by time-resolved infrared spectroscopy.

Science.gov (United States)

He, Zhipeng; Liu, Zhao; Zhou, Xiaofeng; Huang, He

2018-06-01

The secondary structure transitions of regenerated silk fibroin (RSF) under different external perturbations have been studied extensively, except for pressure. In this work, time-resolved infrared spectroscopy with the attenuated total reflectance (ATR) accessory was employed to follow the secondary structure transitions of RSF in its wet film under low pressure. It has been found that pressure alone is favorable only to the formation of β-sheet structure. Under constant pressure there is an optimum amount of D 2 O in the wet film (D 2 O : film = 2:1) so as to provide the optimal condition for the reorganization of the secondary structure and to have the largest formation of β-sheet structure. Under constant amount of D 2 O and constant pressure, the secondary structure transitions of RSF in its wet film can be divided into three stages along with time. In the first stage, random coil, α-helix, and β-turn were quickly transformed into β-sheet. In the second stage, random coil and β-turn were relatively slowly transformed into β-sheet and α-helix, and the content of α-helix was recovered to the value prior to the application of pressure. In the third and final stage, no measurable changes can be found for each secondary structure. This study may be helpful to understand the secondary structure changes of silk fibroin in silkworm's glands under hydrostatic pressure. © 2018 Wiley Periodicals, Inc.

Electronic structure of Sr2RuO4 studied by angle-resolved photoemission spectroscopy

International Nuclear Information System (INIS)

Iwasawa, H.; Aiura, Y.; Saitoh, T.; Yoshida, Y.; Hase, I.; Ikeda, S.I.; Bando, H.; Kubota, M.; Ono, K.

2007-01-01

Electronic structure of the monolayer strontium ruthenate Sr 2 RuO 4 was investigated by high-resolution angle-resolved photoemission spectroscopy. We present photon-energy (hν) dependence of the electronic structure near the Fermi level along the ΓM line. The hν dependence has shown a strong spectral weight modulation of the Ru 4d xy and 4d zx bands

Terahertz time-domain spectroscopy of edible oils

Science.gov (United States)

Dinovitser, Alex; Valchev, Dimitar G.; Abbott, Derek

2017-06-01

Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05-2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min.

A versatile optical microscope for time-dependent single-molecule and single-particle spectroscopy

Science.gov (United States)

Li, Hao; Yang, Haw

2018-03-01

This work reports the design and implementation of a multi-function optical microscope for time-dependent spectroscopy on single molecules and single nanoparticles. It integrates the now-routine single-object measurements into one standalone platform so that no reconfiguration is needed when switching between different types of sample or spectroscopy modes. The illumination modes include evanescent field through total internal reflection, dark-field illumination, and epi-excitation onto a diffraction-limited spot suitable for confocal detection. The detection modes include spectrally resolved line imaging, wide-field imaging with dual-color capability, and two-color single-element photon-counting detection. The switch between different spectroscopy and data acquisition modes is fully automated and executed through computer programming. The capability of this microscope is demonstrated through selected proof-of-principle experiments.

A versatile optical microscope for time-dependent single-molecule and single-particle spectroscopy.

Science.gov (United States)

Li, Hao; Yang, Haw

2018-03-28

This work reports the design and implementation of a multi-function optical microscope for time-dependent spectroscopy on single molecules and single nanoparticles. It integrates the now-routine single-object measurements into one standalone platform so that no reconfiguration is needed when switching between different types of sample or spectroscopy modes. The illumination modes include evanescent field through total internal reflection, dark-field illumination, and epi-excitation onto a diffraction-limited spot suitable for confocal detection. The detection modes include spectrally resolved line imaging, wide-field imaging with dual-color capability, and two-color single-element photon-counting detection. The switch between different spectroscopy and data acquisition modes is fully automated and executed through computer programming. The capability of this microscope is demonstrated through selected proof-of-principle experiments.

Bogoliubov Angle, Particle-Hole Mixture and Angular Resolved Photoemission Spectroscopy in Superconductors

Energy Technology Data Exchange (ETDEWEB)

Balatsky, A.

2010-05-04

Superconducting excitations - Bogoliubov quasiparticles - are the quantum mechanical mixture of negatively charged electron (-e) and positively charged hole (+e). We propose a new observable for Angular Resolved Photoemission Spectroscopy (ARPES) studies that is the manifestation of the particle-hole entanglement of the superconducting quasiparticles. We call this observable a Bogoliubov angle. This angle measures the relative weight of particle and hole amplitude in the superconducting (Bogoliubov) quasiparticle. We show how this quantity can be measured by comparing the ratio of spectral intensities at positive and negative energies.

Improvements in brain activation detection using time-resolved diffuse optical means

Science.gov (United States)

Montcel, Bruno; Chabrier, Renee; Poulet, Patrick

2005-08-01

An experimental method based on time-resolved absorbance difference is described. The absorbance difference is calculated over each temporal step of the optical signal with the time-resolved Beer-Lambert law. Finite element simulations show that each step corresponds to a different scanned zone and that cerebral contribution increases with the arrival time of photons. Experiments are conducted at 690 and 830 nm with a time-resolved system consisting of picosecond laser diodes, micro-channel plate photo-multiplier tube and photon counting modules. The hemodynamic response to a short finger tapping stimulus is measured over the motor cortex. Time-resolved absorbance difference maps show that variations in the optical signals are not localized in superficial regions of the head, which testify for their cerebral origin. Furthermore improvements in the detection of cerebral activation is achieved through the increase of variations in absorbance by a factor of almost 5 for time-resolved measurements as compared to non-time-resolved measurements.

The electronically excited states of LH2 complexes from Rhodopseudomonas acidophila strain 10050 studied by time-resolved spectroscopy and dynamic Monte Carlo simulations. I. Isolated, non-interacting LH2 complexes.

Science.gov (United States)

Pflock, Tobias J; Oellerich, Silke; Southall, June; Cogdell, Richard J; Ullmann, G Matthias; Köhler, Jürgen

2011-07-21

We have employed time-resolved spectroscopy on the picosecond time scale in combination with dynamic Monte Carlo simulations to investigate the photophysical properties of light-harvesting 2 (LH2) complexes from the purple photosynthetic bacterium Rhodopseudomonas acidophila. The variations of the fluorescence transients were studied as a function of the excitation fluence, the repetition rate of the excitation and the sample preparation conditions. Here we present the results obtained on detergent solubilized LH2 complexes, i.e., avoiding intercomplex interactions, and show that a simple four-state model is sufficient to grasp the experimental observations quantitatively without the need for any free parameters. This approach allows us to obtain a quantitative measure for the singlet-triplet annihilation rate in isolated, noninteracting LH2 complexes.

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)

Angle-resolved photoemission spectroscopy of liquid water at 29.5 eV.

Science.gov (United States)

Nishitani, Junichi; West, Christopher W; Suzuki, Toshinori

2017-07-01

Angle-resolved photoemission spectroscopy of liquid water was performed using extreme ultraviolet radiation at 29.5 eV and a time-of-flight photoelectron spectrometer. SiC/Mg coated mirrors were employed to select the single-order 19th harmonic from laser high harmonics, which provided a constant photon flux for different laser polarizations. The instrument was tested by measuring photoemission anisotropy for rare gases and water molecules and applied to a microjet of an aqueous NaI solution. The solute concentration was adjusted to eliminate an electric field gradient around the microjet. The observed photoelectron spectra were analyzed considering contributions from liquid water, water vapor, and an isotropic background. The anisotropy parameters of the valence bands (1 b 1 , 3 a 1 , and 1 b 2 ) of liquid water are considerably smaller than those of gaseous water, which is primarily attributed to electron scattering in liquid water.

HIGH-RESOLUTION IR ABSORPTION SPECTROSCOPY OF POLYCYCLIC AROMATIC HYDROCARBONS: THE REALM OF ANHARMONICITY

Energy Technology Data Exchange (ETDEWEB)

Maltseva, Elena; Buma, Wybren Jan [University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Tielens, Alexander G. G. M. [Leiden Observatory, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Huang, Xinchuan; Lee, Timothy J. [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Oomens, Jos, E-mail: w.j.buma@uva.nl, E-mail: petrignani@strw.leidenuniv.nl [Radboud University, Toernooiveld 7, 6525 ED Nijmegen (Netherlands)

2015-11-20

We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3-μm CH stretching region of polycyclic aromatic hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (∼4 K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main bands that fall within 0.5% of the experimental frequencies. The implications for the aromatic infrared bands, specifically the 3-μm band, are discussed.

High-Resolution IR Absorption Spectroscopy of Polycyclic Aromatic Hydrocarbons: The Realm of Anharmonicity

Science.gov (United States)

Maltseva, Elena; Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Huang, Xinchuan; Lee, Timothy J.; Tielens, Alexander G. G. M.; Oomens, Jos; Buma, Wybren Jan

2016-01-01

We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micrometers CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold ((is) approximately 4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main modes that fall within 0.5% of the experimental frequencies. The implications for the Aromatic Infrared Bands, specifically the 3-m band are discussed.

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)

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 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)

IR Spectroscopy. An introduction

International Nuclear Information System (INIS)

Guenzler, H.; Gremlich, H.U.

2002-01-01

The following topics are dealt with: absorption and molecular design, spectrometers, sample preparation, qualitative spectral interpretation and assertions, near-infrared and far-infrared spectroscopy, reference spectra and expert systems

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.

Coordination-resolved local bond relaxation, electron binding-energy shift, and Debye temperature of Ir solid skins

Energy Technology Data Exchange (ETDEWEB)

Bo, Maolin [Key Laboratory of Low-Dimensional Materials and Application Technologies, Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105 (China); Wang, Yan [Key Laboratory of Low-Dimensional Materials and Application Technologies, Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105 (China); School of Information and Electronic Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201 (China); Huang, Yongli, E-mail: huangyongli@xtu.edu.cn [Key Laboratory of Low-Dimensional Materials and Application Technologies, Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105 (China); Yang, Xuexian [Department of Physics, Jishou University, Jishou, Hunan 416000 (China); Yang, Yezi [Key Laboratory of Low-Dimensional Materials and Application Technologies, Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105 (China); Li, Can [Center for Coordination Bond Engineering, School of Materials Science and Engineering, China Jiliang University, Hangzhou 330018 (China); Sun, Chang Q., E-mail: ecqsun@ntu.edu.sg [Key Laboratory of Low-Dimensional Materials and Application Technologies, Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105 (China); NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

2014-11-30

Highlights: • Cohesive energy of the representative bond determines the core-level shift. • XPS derives the energy level of an isolated atom and its bulk shift. • XPS derives the local bond length, bond energy, binding energy density. • Thermal XPS resolves the Debye temperature and atomic cohesive energy. - Abstract: Numerical reproduction of the measured 4f{sub 7/2} energy shift of Ir(1 0 0), (1 1 1), and (2 1 0) solid skins turns out the following: (i) the 4f{sub 7/2} level of an isolated Ir atom shifts from 56.367 eV to 60.332 eV by 3.965 eV upon bulk formation; (ii) the local energy density increases by up to 130% and the atomic cohesive energy decreases by 70% in the skin region compared with the bulk values. Numerical match to observation of the temperature dependent energy shift derives the Debye temperature that varies from 285.2 K (Surface) to 315.2 K (Bulk). We clarified that the shorter and stronger bonds between under-coordinated atoms cause local densification and quantum entrapment of electron binding energy, which perturbs the Hamiltonian and the core shifts in the skin region.

Fibre-Optic IR-Spectroscopy for Biomedical Diagnostics

OpenAIRE

Bindig, Uwe; Gersonde, Ingo; Meinke, Martina; Becker, Yukiyo; Müller, Gerhard

2003-01-01

The use of microscopy is a valuable means of gaining vital information for medical diagnostics. Due to a number of recent technological developments advances have been made in IR microscopy and in particular, rapid detection methods. Microscopic examination methods usually involve sampling followed by a method of sample purification or preparation. The advantages of the IR analytical method are that it is based on a direct, non‒destructive measurement of sample material and that the resulting...

Time-resolved Femtosecond Photon Echo Probes Bimodal Solvent Dynamics

NARCIS (Netherlands)

Pshenichnikov, M.S; Duppen, K.; Wiersma, D. A.

1995-01-01

We report on time-resolved femtosecond photon echo experiments of a dye molecule in a polar solution. The photon echo is time resolved by mixing the echo with a femtosecond gate pulse in a nonlinear crystal. It is shown that the temporal profile of the photon echo allows separation of the

A tunable low-energy photon source for high-resolution angle-resolved photoemission spectroscopy

International Nuclear Information System (INIS)

Harter, John W.; Monkman, Eric J.; Shai, Daniel E.; Nie Yuefeng; Uchida, Masaki; Burganov, Bulat; Chatterjee, Shouvik; King, Philip D. C.; Shen, Kyle M.

2012-01-01

We describe a tunable low-energy photon source consisting of a laser-driven xenon plasma lamp coupled to a Czerny-Turner monochromator. The combined tunability, brightness, and narrow spectral bandwidth make this light source useful in laboratory-based high-resolution photoemission spectroscopy experiments. The source supplies photons with energies up to ∼7 eV, delivering under typical conditions >10 12 ph/s within a 10 meV spectral bandwidth, which is comparable to helium plasma lamps and many synchrotron beamlines. We first describe the lamp and monochromator system and then characterize its output, with attention to those parameters which are of interest for photoemission experiments. Finally, we present angle-resolved photoemission spectroscopy data using the light source and compare its performance to a conventional helium plasma lamp.

Spatially resolved Raman spectroscopy study of transformed zones in magnesia-partially-stabilized zirconia

International Nuclear Information System (INIS)

Davskardt, R.H.; Veirs, D.K.; Ritchie, R.O.

1989-01-01

Raman vibrational spectroscopy provides an effective phase characterization technique in materials systems containing particle dispersions of the tetragonal and monoclinic polymorphs of zirconia, each of which yields a unique Raman spectrum. An investigation is reported to assess a novel, spatially resolved Raman spectroscopy system in the study of transformed zones surrounding cracks in partially stabilized MgO-ZrO 2 (PSZ). The experimental arrangement uses an imaging (two-dimensional) photomultiplier tube to produce a one-dimensional Raman profile of phase compositions along a slitlike laser beam without translation of either the sample or the laser beam and without scanning the spectrometer. Results from phase characterization studies of the size, frontal morphology, and extent of transformation of transformation zones surrounding cracks produced under monotonic and cyclic loading conditions are presented

The analysis of time-resolved optically stimulated luminescence: I. Theoretical considerations

International Nuclear Information System (INIS)

Chithambo, M L

2007-01-01

This is the first of two linked papers on the analysis of time-resolved optically stimulated luminescence. This paper focusses on a theoretical basis of analytical methods and on methods for interpretation of time-resolved luminescence spectra and calculation of luminescence throughput. Using a comparative analysis of the principal features of time-resolved luminescence and relevant analogues from steady state optical stimulation, formulae for configuring a measurement system for optimum performance are presented. We also examine the possible use of stretched-exponential functions for analysis of time-resolved optically stimulated luminescence spectra

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...

Spatially resolved NEXAFS spectroscopy of siderophores in biological matrices

International Nuclear Information System (INIS)

Thieme, J; Kilcoyne, D; Tyliszczak, T; Haselwandter, K

2013-01-01

Iron is an essential nutrient for almost all forms of life. In the presence of oxygen iron is present in its ferric form which precipitates under formation of rather insoluble oxide-hydroxide polymers. Hence the bioavailability of iron is extremely low ( −17 M at pH 7 for Fe 3+ ). Under such conditions almost all microorganisms synthesize siderophores as iron chelating agents, thus solubilizing ferric iron from rather insoluble iron sources. Siderophores form soluble complexes with Fe 3+ . The present study aims at developing a methodology that would allow for the specific detection and localization of such iron chelators in their natural environment. The applicability of spatially resolved NEXAFS spectroscopy in the soft X-ray energy (E < 1 keV) range was evaluated for localization of typical fungal hydroxamate siderophores like ferrichrome or coprogen, which can be present in various biological materials. Results obtained with the scanning transmission X-ray microscopes at beamlines 11.0.2 and 5.3.2 of the ALS have shown characteristic signatures for siderophores. Thus NEXAFS spectroscopy at the carbon K-edge, nitrogen K-edge and iron L-edge with high spatial resolution has proven to be extremely useful for their identification in their natural environment. Spectra of different siderophores as well as spectra and images of biological material containing siderophores are presented

Study of the Bulk Charge Carrier Dynamics in Anatase and Rutile TiO2 Single Crystals by Femtosecond Time Resolved Spectroscopy

KAUST Repository

Maity, Partha

2018-04-02

Understanding of the fundamentals behind charge carriers of photo-catalytic materials are still illusive hindering progress in our quest for renewable energy. TiO2 anatase and rutile are the most understood phases in photo-catalysis and serve as the best model for fundamental studies. Their ultrafast charge carrier dynamics especially on TiO2 anatase single crystal (the most active phase) are unresolved. Here femtosecond time resolved spectroscopy (TRS) was carried out to explore the dynamics of photo-excited charge carriers’ recombination in anatase single crystal, for the first time using pump fluence effects, and compares it to that of the rutile single crystal. A significant difference in charge carrier recombination rates between both crystals is observed. We found that the time constants for carrier recombination are two orders of magnitude slower for anatase (101) when compared to those of rutile (110). Moreover, bulk defects introduced by reduction of the samples via annealing in ultra-high vacuum resulted in faster recombination rates for both polymorphs. Both states (fresh and reduced) probed by pump fluence dependence measurements revealed that the major recombination channel in fresh and reduced anatase and reduced rutile is the first-order Shockley–Reed mediated. However, for fresh rutile, third-body Auger recombination was observed, attributed to the presence of higher density of intrinsic charge carriers. At all excitation wavelengths and fluence investigated, anatase (101) single crystal show longer charge carrier lifetime when compared to rutile (110) single. This may explain the superiority of the anatase phase for the electron transfer H+ reduction to molecular hydrogen.

Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

Science.gov (United States)

Bromberger, H.; Ermolov, A.; Belli, F.; Liu, H.; Calegari, F.; Chávez-Cervantes, M.; Li, M. T.; Lin, C. T.; Abdolvand, A.; Russell, P. St. J.; Cavalleri, A.; Travers, J. C.; Gierz, I.

2015-08-01

A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi2Se3 with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

Time-resolved CT angiography in aortic dissection

International Nuclear Information System (INIS)

Meinel, Felix G.; Nikolaou, Konstantin; Weidenhagen, Rolf; Hellbach, Katharina; Helck, Andreas; Bamberg, Fabian; Reiser, Maximilian F.; Sommer, Wieland H.

2012-01-01

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.

Infrared multiphoton dissociation of acrolein. Time-resolved observation of CO ( v = 1) IR emission at 4.7 μm

Science.gov (United States)

Chowdhury, P. K.; Rama Rao, K. V. S.; Mittal, J. P.

1994-02-01

In contrast to the photochemistry of electronically excited acrolein producing vinyl and formyl radicals via CC bond rupture, multiphoton vibrationally excited molecules undergo concerted dissociation generating CO and ethylene. Vibrational excitation in the CO product is detected immediately following the CO 2 laser pulse by observing IR emission at 4.7 μm. The decay of the IR emission was studied as a function of acrolein pressure. A vibrational-vibrational relaxation rate constant of CO ( v=1) by acrolein is found to be 1240 ± 200 Torr -1 s -1.

Vibrational Micro-Spectroscopy of Human Tissues Analysis: Review.

Science.gov (United States)

Bunaciu, Andrei A; Hoang, Vu Dang; Aboul-Enein, Hassan Y

2017-05-04

Vibrational spectroscopy (Infrared (IR) and Raman) and, in particular, micro-spectroscopy and micro-spectroscopic imaging have been used to characterize developmental changes in tissues, to monitor these changes in cell cultures and to detect disease and drug-induced modifications. The conventional methods for biochemical and histophatological tissue characterization necessitate complex and "time-consuming" sample manipulations and the results are rarely quantifiable. The spectroscopy of molecular vibrations using mid-IR or Raman techniques has been applied to samples of human tissue. This article reviews the application of these vibrational spectroscopic techniques for analysis of biological tissue published between 2005 and 2015.

Spectroscopy of hexafluorides with an odd number of electrons; Spectroscopie des hexafluorures a nombre impair d'electrons

Energy Technology Data Exchange (ETDEWEB)

Boudon, V

1995-05-01

From a theoretical point of view, a tensorial formalism adapted to the study of molecules or octahedral ions with a half-integer angular momentum has been developed for the first time. We have used here the method of projective representations, more consistent than that of double groups. A complete set of coupling coefficients and formulas, as well as the corresponding computing programs have been elaborated. This has firstly allowed us to write a simple model describing the vibronic structure of colored hexafluorides. Then, some applications of this formalism to the study of ro-vibronic couplings of XY{sub 6} molecules in a fourfold degenerate electronic state have been considered, especially concerning operators associated to dynamic Jahn-Teller effect. From an experimental point of view, we have considered IrF{sub 6}, for which we have mastered the synthesis, purification and conservation processes. A first study at low resolution (absorption and Raman scattering) has been performed for this molecule. We have then set up two high resolution spectroscopic devices in the visible region (saturated absorption - tested with an iodine cell- and simple absorption with multiple pass). These especially use a dye laser. They should now allow the spectroscopy of the visible band of IrF{sub 6} in order to resolve for the first time its fine rotational structure. (author)

Angle-resolved photoemission spectroscopy of liquid water at 29.5 eV

Directory of Open Access Journals (Sweden)

Junichi Nishitani

2017-07-01

Full Text Available Angle-resolved photoemission spectroscopy of liquid water was performed using extreme ultraviolet radiation at 29.5 eV and a time-of-flight photoelectron spectrometer. SiC/Mg coated mirrors were employed to select the single-order 19th harmonic from laser high harmonics, which provided a constant photon flux for different laser polarizations. The instrument was tested by measuring photoemission anisotropy for rare gases and water molecules and applied to a microjet of an aqueous NaI solution. The solute concentration was adjusted to eliminate an electric field gradient around the microjet. The observed photoelectron spectra were analyzed considering contributions from liquid water, water vapor, and an isotropic background. The anisotropy parameters of the valence bands (1b1, 3a1, and 1b2 of liquid water are considerably smaller than those of gaseous water, which is primarily attributed to electron scattering in liquid water.

A new Density Functional Theory (DFT) based method for supporting the assignment of vibrational signatures of mannan and cellulose—Analysis of palm kernel cake hydrolysis by ATR-FT-IR spectroscopy as a case study

DEFF Research Database (Denmark)

Barsberg, Søren Talbro; Sanadi, Anand Ramesh; Jørgensen, Henning

2011-01-01

Attenuated Total Reflectance (ATR) FT-IR spectroscopy gives in situ information on molecular concentration, organization and interactions in plant cell walls. We demonstrate its potential for further developments by a case study which combines ATR-FT-IR spectroscopy with a recently published DFT...... a decreasing degree of polymerization to be a plausible cause, although others may interfere. Keywords: Cellulose; Mannan; FT-IR; DFT; Molecular modelling; Palm kernel...

Element-resolved x-ray ferrimagnetic and ferromagnetic resonance spectroscopy

International Nuclear Information System (INIS)

Boero, G; Mouaziz, S; Rusponi, S; Bencok, P; Nolting, F; Stepanow, S; Gambardella, P

2008-01-01

We report on the measurement of element-specific magnetic resonance spectra at gigahertz frequencies using x-ray magnetic circular dichroism (XMCD). We investigate the ferrimagnetic precession of Gd and Fe ions in Gd-substituted yttrium iron garnet, showing that the resonant field and linewidth of Gd precisely coincide with Fe up to the nonlinear regime of parametric excitations. The opposite sign of the Gd x-ray magnetic resonance signal with respect to Fe is consistent with dynamic antiferromagnetic alignment of the two ionic species. Further, we investigate a bilayer metal film, Ni 80 Fe 20 (5 nm)/Ni(50 nm), where the coupled resonance modes of Ni and Ni 80 Fe 20 are separately resolved, revealing shifts in the resonance fields of individual layers but no mutual driving effects. Energy-dependent dynamic XMCD measurements are introduced, combining x-ray absorption and magnetic resonance spectroscopies

The Influence of Cholesterol on Fast Dynamics Inside of Vesicle and Planar Phospholipid Bilayers Measured with 2D IR Spectroscopy.

Science.gov (United States)

Kel, Oksana; Tamimi, Amr; Fayer, Michael D

2015-07-23

Phospholipid bilayers are frequently used as models for cell membranes. Here the influence of cholesterol on the structural dynamics in the interior of 1,2-dilauroyl-sn-glycero-3-phosphocholine (dilauroylphosphatidylcholine, DLPC) vesicles and DLPC planar bilayers are investigated as a function of cholesterol concentration. 2D IR vibrational echo spectroscopy was performed on the antisymmetric CO stretch of the vibrational probe molecule tungsten hexacarbonyl, which is located in the interior alkyl regions of the bilayers. The 2D IR experiments measure spectral diffusion, which is caused by the structural fluctuations of the bilayers. The 2D IR measurements show that the bilayer interior alkyl region dynamics occur on time scales ranging from a few picoseconds to many tens of picoseconds. These are the time scales of the bilayers' structural dynamics, which act as the dynamic solvent bath for chemical processes of membrane biomolecules. The results suggest that at least a significant fraction of the dynamics arise from density fluctuations. Samples are studied in which the cholesterol concentration is varied from 0% to 40% in both the vesicles (72 nm diameter) and fully hydrated planar bilayers in the form of aligned multibilayers. At all cholesterol concentrations, the structural dynamics are faster in the curved vesicle bilayers than in the planar bilayers. As the cholesterol concentration is increased, at a certain concentration there is a sudden change in the dynamics, that is, the dynamics abruptly slow down. However, this change occurs at a lower concentration in the vesicles (between 10% and 15% cholesterol) than in the planar bilayers (between 25% and 30% cholesterol). The sudden change in the dynamics, in addition to other IR observables, indicates a structural transition. However, the results show that the cholesterol concentration at which the transition occurs is influenced by the curvature of the bilayers.

New methods and applications in time-resolved X-ray absorption spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Stoetzel, Jan Eric

2012-07-01

Recent experimental advances and developments in the QEXAFS technique were presented along with new applications in the disciplines of catalysis and surface science. Both performance and user-friendliness of the QEXAFS method were significantly improved, while the applicability of QEXAFS was extended by newly designed mechanics. The application of a fast angular encoder proved to be capable to sample the continuously changing Bragg angle of the monochromator crystal synchronized to the acquired absorption data. A new data acquisition system was designed, based on a multifunctional ADC board, which provides high acquisition frequencies, while low noise acquisition could be achieved due to the provided differential acquisition mode. Additionally, control of all experimental devices as current amplifiers, monochromator motors and sample stages were implemented to further increase the efficiency of the experimental setup for QEFAS measurements. In order to simplify the processing of the huge generated QEXAFS raw data files, a completely new software tool for data analysis was designed, which provides not only the basic procedures of QEXAFS data analysis, but also many approaches customized for time-resolved data. Apart from technical advances, various experiments were performed with QEXAFS to gain new insights into the complex processes of several catalytic reactions, the thermal decomposition of metal oxalates, as well as layer growth processes and reactions on rough surfaces. Supported Pd catalysts were investigated during catalytic partial oxidation of methane, whereby oscillations in the conversion were linked to structural changes of the catalyst. Kinetic oscillations were also investigated on a supported Pt catalyst during the extinction of CO oxidation induced by decreasing temperature. Modulated experiments were investigated (i) on supported Pt-Rh/Al{sub 2}O{sub 3} catalysts during active catalytic partial oxidation in switching gas atmospheres of methane and

An overview on the research of Sr2IrO4-based system probed by X-ray absorption spectroscopy

Science.gov (United States)

Cheng, Jie; Zhu, Chaomin; Ma, Jingyuan; Wang, Yu; Liu, Shengli

2018-03-01

Investigations of materials with 5d transition metal ions have opened up new paradigms in condensed-matter physics because of their large spin-orbit coupling (SOC) interactions. The typical compound is Sr2IrO4, which attracted much attention due to its similarities to the parent compound of high-Tc cuprate superconductor La2CuO4. Theoretical calculations predicted that the unconventional superconductivity can occur in carrier doped-Sr2IrO4 system. Until now, hundreds of experimental methods were devoted to investigate the carrier doping effect on Sr2IrO4. Synchrotron radiation-based X-ray absorption spectroscopy (XAS) made great contributions to the local lattice and electronic structure, and also the intimate relationship between the local structure and physical properties induced by carrier doping. The aim of this review is a short introduction to the progress of research on Sr2IrO4-based system probed by the unique technique — XAS, including the strength of the SOC, valence changes upon doping and even local lattice structure with atomic level for this Sr2IrO4-based family.

Dynamical interactions between solute and solvent studied by nonlinear infrared spectroscopy

International Nuclear Information System (INIS)

Ohta, K.; Tominaga, K.

2006-01-01

Interactions between solute and solvent play an important role in chemical reaction dynamics and in many relaxation processes in condensed phases. Recently third-order nonlinear infrared (IR) spectroscopy has shown to be useful to investigate solute-solvent interaction and dynamics of the vibrational transition. These studies provide detailed information on the energy relaxation of the vibrationally excited state, and the time scale and the magnitude of the time correlation functions of the vibrational frequency fluctuations. In this work we have studied vibrational energy relaxation (VER) of solutions and molecular complexes by nonlinear IR spectroscopy, especially IR pump-probe method, to understand the microscopic interactions in liquids. (authors)

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.

Time-resolved UV spectroscopy on ammonia excited by a pulsed CO2 laser

International Nuclear Information System (INIS)

Holbach, H.

1980-07-01

This work investigates the excitation of ammonia by a pulsed CO 2 laser, in particular the processes associated with collisions with argon. It was prompted by two previous observations: the previously reported infrared multiphoton dissociation of NH 3 under nearly collisionless conditions, and the ill understood excitation mechanism of apparently nonresonant low vibrational levels in the presence of Ar. Based on recent spectroscopic data, all vibrational-rotational levels were determined which are simultaneously excited by different CO 2 laser lines. Transitions between the 1 + and 2 - vibrational levels were also taken into account. The linewidth in these calculations was dominated by power broadening, which generates a half width at half maximum of 0.36 cm -1 at the typical power density of 10 MW/cm 2 . In order to reproduce published experimental absorption data, it proved necessary to take account all transitions within a distance of 20 cm -1 from the laser line. This fact implies in most cases the simultaneous population of a large number of vibrational-rotational levels. The population of levels by absorption or by subsequent collisional processes was probed by time-resolved absorption measurement of vibrational bands and their rotational envelope in the near UV. Time resolution (5...10) was sufficient to observe rotational relaxation within individual vibrational levels. Characteristic differences were found for the various excitation lines. (orig.) [de

Time-resolved soft x-ray spectra from laser-produced Cu plasma

International Nuclear Information System (INIS)

Cone, K.V.; Dunn, J.; Baldis, H.A.; May, M.J.; Purvis, M.A.; Scott, H.A.; Schneider, M.B.

2012-01-01

The volumetric heating of a thin copper target has been studied with time resolved x-ray spectroscopy. The copper target was heated from a plasma produced using the Lawrence Livermore National Laboratory's Compact Multipulse Terrawatt (COMET) laser. A variable spaced grating spectrometer coupled to an x-ray streak camera measured soft x-ray emission (800-1550 eV) from the back of the copper target to characterize the bulk heating of the target. Radiation hydrodynamic simulations were modeled in 2-dimensions using the HYDRA code. The target conditions calculated by HYDRA were post-processed with the atomic kinetics code CRETIN to generate synthetic emission spectra. A comparison between the experimental and simulated spectra indicates the presence of specific ionization states of copper and the corresponding electron temperatures and ion densities throughout the laser-heated copper target.

Femtosecond Time-resolved Optical Polarigraphy (FTOP)

International Nuclear Information System (INIS)

Aoshima, S.; Fujimoto, M.; Hosoda, M.; Tsuchiya, Y.

2000-01-01

A novel time-resolved imaging technique named FTOP (Femtosecond Time-resolved Optical Polarigraphy) for visualizing the ultrafast propagation dynamics of intense light pulses in a medium has been proposed and demonstrated. Femtosecond snapshot images can be created with a high spatial resolution by imaging only the polarization components of the probe pulse; these polarization components change due to the instantaneous birefringence induced by the pump pulse in the medium. Ultrafast temporal changes in the two-dimensional spatial distribution of the optical pulse intensity were clearly visualized in consecutive images by changing the delay between the pump and probe. We observe that several filaments appear and then come together before the vacuum focus due to nonlinear effects in air. We also prove that filamentation dynamics such as the formation position and the propagation behavior are complex and are strongly affected by the pump energy. The results collected clearly show that this method FTOP succeeds for the first time in directly visualizing the ultrafast dynamics of the self-modulated nonlinear propagation of light. (author)

Resolving the HD 100546 Protoplanetary System with the Gemini Planet Imager: Evidence for Multiple Forming, Accreting Planets

OpenAIRE

Currie, Thayne; Cloutier, Ryan; Brittain, Sean; Grady, Carol; Burrows, Adam; Muto, Takayuki; Kenyon, Scott J.; Kuchner, Marc J.

2015-01-01

We report Gemini Planet Imager H band high-contrast imaging/integral field spectroscopy and polarimetry of the HD 100546, a 10 $Myr$-old early-type star recently confirmed to host a thermal infrared bright (super)jovian protoplanet at wide separation, HD 100546 b. We resolve the inner disk cavity in polarized light, recover the thermal-infrared (IR) bright arm, and identify one additional spiral arm. We easily recover HD 100546 b and show that much of its emission originates an unresolved, po...

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.

FT-IR microscopical analysis with synchrotron radiation: The microscope optics and system performance

International Nuclear Information System (INIS)

Reffner, J.A.; Martoglio, P.A.; Williams, G.P.

1995-01-01

When a Fourier transform infrared (FT-IR) microspectrometer was first interfaced with the National Synchrotron Light Source (NSLS) in September 1993, there was an instant realization that the performance at the diffraction limit had increased 40-100 times. The synchrotron source transformed the IR microspectrometer into a true IR microprobe, providing high-quality IR spectra for probe diameters at the diffraction limit. The combination of IR microspectroscopy and synchrotron radiation provides a powerful new tool for molecular spectroscopy. The ability to perform IR microspectroscopy with synchrotron radiation is still under development at Brookhaven National Laboratory, but several initial studies have been completed that demonstrate the broad-ranging applications of this technology and its potential for materials characterization

FT-IR microscopical analysis with synchrotron radiation: The microscope optics and system performance

Energy Technology Data Exchange (ETDEWEB)

Reffner, J.A.; Martoglio, P.A. [Spectra-Tech, Inc., Shelton, CT (United States); Williams, G.P. [Brookhaven National Lab., Upton, NY (United States)

1995-01-01

When a Fourier transform infrared (FT-IR) microspectrometer was first interfaced with the National Synchrotron Light Source (NSLS) in September 1993, there was an instant realization that the performance at the diffraction limit had increased 40-100 times. The synchrotron source transformed the IR microspectrometer into a true IR microprobe, providing high-quality IR spectra for probe diameters at the diffraction limit. The combination of IR microspectroscopy and synchrotron radiation provides a powerful new tool for molecular spectroscopy. The ability to perform IR microspectroscopy with synchrotron radiation is still under development at Brookhaven National Laboratory, but several initial studies have been completed that demonstrate the broad-ranging applications of this technology and its potential for materials characterization.

Nonlinear Optical Spectroscopy in the Time Domain: Studies of Ultrafast Molecular Processes in the Condensed Phase.

Science.gov (United States)

Joo, Taiha

Ultrafast molecular processes in the condensed phase at room temperature are studied in the time domain by four wave mixing spectroscopy. The structure/dynamics of various quantum states can be studied by varying the time ordering of the incident fields, their polarization, their colors, etc. In one, time-resolved coherent Stokes Raman spectroscopy of benzene is investigated at room temperature. The reorientational correlation time of benzene as well as the T_2 time of the nu _1 ring-breathing mode have been measured by using two different polarization geometries. Bohr frequency difference beats have also been resolved between the nu_1 modes of ^ {12}C_6H_6 and ^{12}C_5^{13 }CH_6.. The dephasing dynamics of the nu _1 ring-breathing mode of neat benzene is studied by time-resolved coherent anti-Stokes Raman scattering. Ultrafast time resolution reveals deviation from the conventional exponential decay. The correlation time, tau _{rm c}, and the rms magnitude, Delta, of the Bohr frequency modulation are determined for the process responsible for the vibrational dephasing by Kubo dephasing function analysis. The electronic dephasing of two oxazine dyes in ethylene glycol at room temperature is investigated by photon echo experiments. It was found that at least two stochastic processes are responsible for the observed electronic dephasing. Both fast (homogeneous) and slow (inhomogeneous) dynamics are recovered using Kubo line shape analysis. Moreover, the slow dynamics is found to spectrally diffuse over the inhomogeneous distribution on the time scale around a picosecond. Time-resolved degenerate four wave mixing signal of dyes in a population measurement geometry is reported. The vibrational coherences both in the ground and excited electronic states produced strong oscillations in the signal together with the usual population decay from the excited electronic state. Absolute frequencies and their dephasing times of the vibrational modes at ~590 cm^{-1} are obtained

Spectroscopy of hexafluorides with an odd number of electrons; Spectroscopie des hexafluorures a nombre impair d'electrons

Energy Technology Data Exchange (ETDEWEB)

Boudon, V

1995-05-01

From a theoretical point of view, a tensorial formalism adapted to the study of molecules or octahedral ions with a half-integer angular momentum has been developed for the first time. We have used here the method of projective representations, more consistent than that of double groups. A complete set of coupling coefficients and formulas, as well as the corresponding computing programs have been elaborated. This has firstly allowed us to write a simple model describing the vibronic structure of colored hexafluorides. Then, some applications of this formalism to the study of ro-vibronic couplings of XY{sub 6} molecules in a fourfold degenerate electronic state have been considered, especially concerning operators associated to dynamic Jahn-Teller effect. From an experimental point of view, we have considered IrF{sub 6}, for which we have mastered the synthesis, purification and conservation processes. A first study at low resolution (absorption and Raman scattering) has been performed for this molecule. We have then set up two high resolution spectroscopic devices in the visible region (saturated absorption - tested with an iodine cell- and simple absorption with multiple pass). These especially use a dye laser. They should now allow the spectroscopy of the visible band of IrF{sub 6} in order to resolve for the first time its fine rotational structure. (author)

Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

Energy Technology Data Exchange (ETDEWEB)

Bromberger, H., E-mail: Hubertus.Bromberger@mpsd.mpg.de; Liu, H.; Chávez-Cervantes, M.; Gierz, I. [Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg (Germany); Ermolov, A.; Belli, F.; Abdolvand, A.; Russell, P. St. J.; Travers, J. C. [Max Planck Institute for the Science of Light, Günther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Calegari, F. [Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg (Germany); Institute for Photonics and Nanotechnologies, IFN-CNR, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Li, M. T.; Lin, C. T. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Cavalleri, A. [Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg (Germany); Clarendon Laboratory, Department of Physics, University of Oxford, Parks Rd. Oxford OX1 3PU (United Kingdom)

2015-08-31

A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi{sub 2}Se{sub 3} with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

International Nuclear Information System (INIS)

Bromberger, H.; Liu, H.; Chávez-Cervantes, M.; Gierz, I.; Ermolov, A.; Belli, F.; Abdolvand, A.; Russell, P. St. J.; Travers, J. C.; Calegari, F.; Li, M. T.; Lin, C. T.; Cavalleri, A.

2015-01-01

A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi 2 Se 3 with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials

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

Science.gov (United States)

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

1994-07-01

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

Differentiation of Body Fluid Stains on Fabrics Using External Reflection Fourier Transform Infrared Spectroscopy (FT-IR) and Chemometrics.

Science.gov (United States)

Zapata, Félix; de la Ossa, Ma Ángeles Fernández; García-Ruiz, Carmen

2016-04-01

Body fluids are evidence of great forensic interest due to the DNA extracted from them, which allows genetic identification of people. This study focuses on the discrimination among semen, vaginal fluid, and urine stains (main fluids in sexual crimes) placed on different colored cotton fabrics by external reflection Fourier transform infrared spectroscopy (FT-IR) combined with chemometrics. Semen-vaginal fluid mixtures and potential false positive substances commonly found in daily life such as soaps, milk, juices, and lotions were also studied. Results demonstrated that the IR spectral signature obtained for each body fluid allowed its identification and the correct classification of unknown stains by means of principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). Interestingly, results proved that these IR spectra did not show any bands due to the color of the fabric and no substance of those present in daily life which were analyzed, provided a false positive. © The Author(s) 2016.

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

Science.gov (United States)

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

2013-03-01

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

Determination of alkaloids in capsules, milk and ethanolic extracts of poppy (Papaver somniferum L.) by ATR-FT-IR and FT-Raman spectroscopy.

Science.gov (United States)

Schulz, Hartwig; Baranska, Malgorzata; Quilitzsch, Rolf; Schütze, Wolfgang

2004-10-01

Fourier transform (FT) infrared spectroscopy using a diamond composite ATR crystal and NIR-FT-Raman spectroscopy techniques were applied for the simultaneous identification and quantification of the most important alkaloids in poppy capsules. Most of the characteristic Raman signals of the alkaloids can be identified in poppy milk isolated from unripe capsules. But also poppy extracts present specific bands relating clearly to the alkaloid fraction. Raman spectra obtained by excitation with a Nd:YAG laser at 1064 nm show no disturbing fluorescence effects; therefore the plant tissue can be recorded without any special preparation. The used diamond ATR technique allows to measure very small sample amounts (5-10 microL or 2-5 mg) without the necessity to perform time-consuming pre-treatments. When applying cluster analysis a reliable discrimination of "low-alkaloid" and "high-alkaloid" poppy single-plants can be easily achieved. The examples presented in this study provide clear evidence of the benefits of Raman and ATR-IR spectroscopy in efficient quality control, forensic analysis and high-throughput evaluation of poppy breeding material.

ATR FT-IR spectroscopy on Vmh2 hydrophobin self-assembled layers for Teflon membrane bio-functionalization

International Nuclear Information System (INIS)

Portaccio, M.; Gravagnuolo, A.M.; Longobardi, S.; Giardina, P.; Rea, I.; De Stefano, L.; Cammarota, M.; Lepore, M.

2015-01-01

Graphical abstract: - Highlights: • Hydrophobin self-assembled layers on Teflon in different preparation conditions were investigated. • ATR collection data geometry allowed samples examination without any particular preparation. • Amide content, lipid/amide and carbohydrate/amide ratios of the protein layer were estimated. • Secondary structure of protein was determined for the examined samples. • FT-IR demonstrated to be of extreme relevance in monitoring hydrophobin self-assembled layers preparation. - Abstract: Surface functionalization by layers of hydrophobins, amphiphilic proteins produced by fungi offers a promising and green strategy for fabrication of biomedical and bioanalytical devices. The layering process of the Vmh2 hydrophobin from Pleurotus ostreatus on Teflon membrane has been investigated by Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) spectroscopy. In particular, protein layers obtained with hydrophobin purified with two different procedures and in various coating conditions have been examined. The layers have been characterized by quantifying the amide I and amide II band area together with the lipid/amide ratio and carbohydrate/amide ratio. This characterization can be very useful in evaluating the best purification strategy and coating conditions. Moreover the analysis of the secondary structure of the layered protein using the deconvolution procedure of amide I band indicate the prevalent contribution from β-sheet state. The results inferred by infrared spectroscopy have been also confirmed by scanning electron microscopy imaging