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Sample records for adeep-ultraviolet resonance raman

  1. On the Increasing Fragility of Human Teeth with Age: ADeep-Ultraviolet Resonance Raman Study

    Energy Technology Data Exchange (ETDEWEB)

    Ager III, J.W.; Nalla, R.K.; Balooch, G.; Kim, G.; Pugach, M.; Habelitz, S.; Marshall, G.W.; Kinney, J.H.; Ritchie, R.O.

    2006-07-14

    Ultraviolet resonance Raman spectroscopy (UVRRS) using 244nm excitation was used to investigate the impact of aging on humandentin. The intensity of a spectroscopic feature from the peptide bondsin the collagen increases with tissue age, similar to a finding reportedpreviously for human cortical bone.

  2. Second order resonant Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Cristobal, A.; Catarero, A. [Valencia Univ. (Spain). Dept. de Fisica Aplicada; Trallero-Giner, C. [Instituto Politecnico Nacional, Mexico City (Mexico). Centro de Investigacion y de Estudios Avanzados

    1996-03-01

    A theoretical model for resonant Raman scattering by two optical phonons in zincblende-type semiconductors is presented. The effect of Coulomb interaction between electrons and holes is taken into account by introducing discrete and continuous excitonic intermediate states. The model can be applied for laser frequencies below and above the band gap. We consider deformation potential and Froehlich interaction for the electron-one-phonon coupling. The absolute value of the scattering efficiency is evaluated for the L-O-phonons, TO-plus LO-phonon and two-TO-photons Raman processes, around the E{sub o} absorption edge of II-VI compound semiconductors. Comparison with the electron-hole uncorrelated theory and experimental data emphasizes the role if the excitonic effects. (author). 10 refs., 2 figs.

  3. Resonance raman studies of phenylcyclopropane radical cations

    NARCIS (Netherlands)

    Godbout, J.T.; Zuilhof, H.; Heim, G.; Gould, I.R.; Goodman, J.L.; Dinnocenzo, J.P.; Myers Kelley, A.

    2000-01-01

    Resonance Raman spectra of the radical cations of phenylcyclopropane and trans-1-phenyl-2-methylcyclopropane are reported. A near-UV pump pulse excites a photosensitizer which oxidizes the species of interest, and a visible probe pulse delayed by 35 ns obtains the spectrum of the radical ion. The tr

  4. Resonance Raman Optical Activity and Surface Enhanced Resonance Raman Optical Activity analysis of Cytochrome C

    DEFF Research Database (Denmark)

    Johannessen, Christian; Abdali, Salim; White, Peter C.

    2007-01-01

    to resonance enhanced skeletal porphyrin vibrations, more pronounced than any contribution from the protein back-bone. Combining the intrinsic resonance enhancement of cytochrome c with surface plasmon enhancement by colloidal silver particles, the Surface Enhanced Resonance Raman Scattering (SERRS) and Chiral......, while some disparities were observed between the resonance ROA and ChERS spectra. The difference can be ascribed perturbations of the physical properties of the protein upon adhesion to the surface of the silver colloids....

  5. Ultraviolet Resonant Raman Enhancements in the Detection of Explosives

    Energy Technology Data Exchange (ETDEWEB)

    Short Jr., Billy Joe [Naval Postgraduate School, Monterey, CA (United States)

    2009-06-01

    Raman-based spectroscopy is potentially militarily useful for standoff detection of high explosives. Normal (non-resonance) and resonance Raman spectroscopies are both light scattering techniques that use a laser to measure the vibrational spectrum of a sample. In resonance Raman, the laser is tuned to match the wavelength of a strong electronic absorbance in the molecule of interest, whereas, in normal Raman the laser is not tuned to any strong electronic absorbance bands. The selection of appropriate excitation wavelengths in resonance Raman can result in a dramatic increase in the Raman scattering efficiency of select band(s) associated with the electronic transition. Other than the excitation wavelength, however, resonance Raman is performed experimentally the same as normal Raman. In these studies, normal and resonance Raman spectral signatures of select solid high explosive (HE) samples and explosive precursors were collected at 785 nm, 244 nm and 229 nm. Solutions of PETN, TNT, and explosive precursors (DNT & PNT) in acetonitrile solvent as an internal Raman standard were quantitatively evaluated using ultraviolet resonance Raman (UVRR) microscopy and normal Raman spectroscopy as a function of power and select excitation wavelengths. Use of an internal standard allowed resonance enhancements to be estimated at 229 nm and 244 nm. Investigations demonstrated that UVRR provided ~2000-fold enhancement at 244 nm and ~800-fold improvement at 229 nm while PETN showed a maximum of ~25-fold at 244 nm and ~190-fold enhancement at 229 nm solely from resonance effects when compared to normal Raman measurements. In addition to the observed resonance enhancements, additional Raman signal enhancements are obtained with ultraviolet excitation (i.e., Raman scattering scales as !4 for measurements based on scattered photons). A model, based partly on the resonance Raman enhancement results for HE solutions, is presented for estimating Raman enhancements for solid HE samples.

  6. Perspective: Two-dimensional resonance Raman spectroscopy

    Science.gov (United States)

    Molesky, Brian P.; Guo, Zhenkun; Cheshire, Thomas P.; Moran, Andrew M.

    2016-11-01

    Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in complex systems. The 2DRR method can leverage electronic resonance enhancement to selectively probe chromophores embedded in complex environments (e.g., a cofactor in a protein). In addition, correlations between the two dimensions of the 2DRR spectrum reveal information that is not available in traditional Raman techniques. For example, distributions of reactant and product geometries can be correlated in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this perspective article, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide and myoglobin. We also address key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopies. Most notably, it has been shown that these two techniques are subject to a tradeoff between sensitivity to anharmonicity and susceptibility to artifacts. Overall, recent experimental developments and applications of the 2DRR method suggest great potential for the future of the technique.

  7. Preventing Raman Lasing in High-Q WGM Resonators

    Science.gov (United States)

    Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry; Maleki, Lute

    2007-01-01

    A generic design has been conceived to suppress the Raman effect in whispering- gallery-mode (WGM) optical resonators that have high values of the resonance quality factor (Q). Although it is possible to exploit the Raman effect (even striving to maximize the Raman gain to obtain Raman lasing), the present innovation is intended to satisfy a need that arises in applications in which the Raman effect inhibits the realization of the full potential of WGM resonators as frequency-selection components. Heretofore, in such applications, it has been necessary to operate high-Q WGM resonators at unattractively low power levels to prevent Raman lasing. (The Raman-lasing thresholds of WGM optical resonators are very low and are approximately proportional to Q(sup -2)). Heretofore, two ways of preventing Raman lasting at high power levels have been known, but both entail significant disadvantages: A resonator can be designed so that the optical field is spread over a relatively large mode volume to bring the power density below the threshold. For any given combination of Q and power level, there is certain mode volume wherein Raman lasing does not start. Unfortunately, a resonator that has a large mode volume also has a high spectral density, which is undesirable in a typical photonic application. A resonator can be cooled to the temperature of liquid helium, where the Raman spectrum is narrower and, therefore, the Raman gain is lower. However, liquid-helium cooling is inconvenient. The present design overcomes these disadvantages, making it possible to operate a low-spectral-density (even a single-mode) WGM resonator at a relatively high power level at room temperature, without risk of Raman lasing.

  8. Time Resolved Resonance Raman Conference Royal Institution, London United Kingdom,

    Science.gov (United States)

    1983-01-01

    polar molecules. The rejection of fluorescence which is practically inherent _s most if not all resonance Raman experiments was discussed is great ...presented may be devided into two sections. 1) chemical processes presented in the rorninq and 2) biological in the afternoon. The resonance Raman spectra

  9. Triplet State Resonance Raman Spectrum of all-trans-diphenylbutadiene

    DEFF Research Database (Denmark)

    Wilbrandt, Robert Walter; Grossman, W.E.L.; Killough, P.M;

    1984-01-01

    The resonance Raman spectrum of all-trans-diphenylbutadiene (DPB) in its ground state and the resonance Raman spectrum (RRS) of DPB in its short-lived electronically excited triplet state are reported. Transient spectra were obtained by a pump-probe technique using two pulsed lasers. The prereson...

  10. Fast Resonance Raman Spectroscopy of Short-Lived Radicals

    DEFF Research Database (Denmark)

    Pagsberg, Palle Bjørn; Wilbrandt, Robert Walter; Hansen, Karina Benthin

    1976-01-01

    We report the first application of pulsed resonance Raman spectroscopy to the study of short-lived free radicals produced by pulse radiolysis. A single pulse from a flash-lamp pumped tunable dye laser is used to excite the resonance Raman spectrum of the p-terphenyl anion radical with an initial...

  11. Chemical state speciation by resonant Raman scattering

    CERN Document Server

    Karydas, A G; Zarkadas, C; Paradelis, T; Kallithrakas-Kontos, N

    2002-01-01

    In the resonant Raman scattering (RRS) process the emitted photon exhibits a continuous energy distribution with a high energy cutoff limit. This cutoff energy depends on the chemical state of the element under examination. In the present work, the possibility of identifying the chemical state of V atoms by employing RRS spectroscopy with a semiconductor Si(Li) detector is investigated. A proton induced Cr K alpha x-ray beam was used as the incident radiation, having a fixed energy lower than the V K-absorption edge. The net RRS distributions extracted from the energy dispersive spectra of metallic V and its compound targets were simulated by an appropriate theoretical model. The results showed the possibility of employing RRS spectroscopy with a semiconductor detector for chemical speciation studies.

  12. Resonance Raman excitation profiles of lycopene

    Science.gov (United States)

    Hoskins, L. C.

    1981-01-01

    The resonance Raman spectrum of lycopene has been examined in acetone solvent and excitation profiles of the three fundamentals ν1, ν2, and ν3 have been determined. The excitation data and the visible spectrum have been analyzed using two-mode and three-mode vibrational models, with the two-mode model involving virtual states of ν1 and ν2 giving the best fit to the data. This mode mixing or Duskinsky effect was not observed for β-carotene. The single-mode and three-mode theories which have been used to explain the corresponding data for β-carotene are shown to be inconsistent with the experimental data of lycopene. Equations for calculating excitation profiles and visible spectra are given.

  13. Resonant enhancement of Raman scattering in metamaterials with hybrid electromagnetic and plasmonic resonances

    CERN Document Server

    Guddala, Sriram; Ramakrishna, S Anantha

    2016-01-01

    A tri-layer metamaterial perfect absorber of light, consisting of (Al/ZnS/Al) films with the top aluminium layer patterned as an array of circular disk nanoantennas, is investigated for resonantly enhancing Raman scattering from C-60 fullerene molecules deposited on the metamaterial. The metamaterial is designed to have resonant bands due to plasmonic and electromagnetic resonances at the Raman pump frequency (725 nm) as well as Stokes emission bands. The Raman scattering from C60 on the metamaterial with resonantly matched bands is measured to be enhanced by an order of magnitude more than from C60 on metamaterials with off-resonant absorption bands peaked at 1090 nm. The Raman pump is significantly enhanced due to the resonance with a propagating surface plasmon band, while the highly impedance matched electromagnetic resonance is expected to couple out the Raman emission efficiently. The nature and hybridization of the plasmonic and electromagnetic resonances to form compound resonances are investigated by...

  14. Bithiophene radical cation: Resonance Raman spectroscopy and molecular orbital calculations

    DEFF Research Database (Denmark)

    Grage, M.M.-L.; Keszthelyi, T.; Offersgaard, J.F.

    1998-01-01

    The resonance Raman spectrum of the photogenerated radical cation of bithiophene is reported. The bithiophene radical cation was produced via a photoinduced electron transfer reaction between excited bithiophene and the electron acceptor fumaronitrile in a room temperature acetonitrile solution a...

  15. Transform analysis of the resonance Raman excitation profile of lycopene

    Science.gov (United States)

    Hoskins, L. C.

    1992-10-01

    The resonance Raman excitation profiles (RREPs) of the ν 1, ν 2 and ν 3 vibrations of lycopene in acetone, ethyl alcohol, toluene and carbon disulphide solvents have been analyzed using the transform method for calculating resonance Raman excitation profiles. The tests show excellent agreement between the calculated and observed profiles for the ν 2 and ν 3 RREPs, but greater difference between experiment and theory occurs for the ν 1 RREP, especially in carbon disulphide solvent.

  16. Transmission resonance Raman spectroscopy: experimental results versus theoretical model calculations.

    Science.gov (United States)

    Gonzálvez, Alicia G; González Ureña, Ángel

    2012-10-01

    A laser spectroscopic technique is described that combines transmission and resonance-enhanced Raman inelastic scattering together with low laser power (view, a model for the Raman signal dependence on the sample thickness is also presented. Essentially, the model considers the sample to be homogeneous and describes the underlying physics using only three parameters: the Raman cross-section, the laser-radiation attenuation cross-section, and the Raman signal attenuation cross-section. The model was applied successfully to describe the sample-size dependence of the Raman signal in both β-carotene standards and carrot roots. The present technique could be useful for direct, fast, and nondestructive investigations in food quality control and analytical or physiological studies of animal and human tissues.

  17. Periodontitis diagnostics using resonance Raman spectroscopy on saliva

    Science.gov (United States)

    Gonchukov, S.; Sukhinina, A.; Bakhmutov, D.; Biryukova, T.; Tsvetkov, M.; Bagratashvily, V.

    2013-07-01

    In view of its wealth of molecular information, Raman spectroscopy has been the subject of active biomedical research. The aim of this work is Raman spectroscopy (RS) application for the determination of molecular biomarkers in saliva with the objective of early periodontitis detection. As was shown in our previous study, carotenoids contained in saliva can be molecular fingerprint information for the periodontitis level. It is shown here that the carotenoid RS lines at wavenumbers of 1156 and 1524 cm-1 can be easily detected and serve as reliable biomarkers of periodontitis using resonance Raman spectroscopy of dry saliva.

  18. Resonance Raman Spectroscopy of Free Radicals Produced by Ionizing Radiation

    DEFF Research Database (Denmark)

    Wilbrandt, Robert Walter

    1984-01-01

    Applications of time-resolved resonance Raman spectroscopy to the study of short-lived free radicals produced by ionizing radiation are briefly reviewed. Potential advantages and limitations of this technique are discussed in the light of given examples. The reduction of p-nitrobenzylchloride and......Applications of time-resolved resonance Raman spectroscopy to the study of short-lived free radicals produced by ionizing radiation are briefly reviewed. Potential advantages and limitations of this technique are discussed in the light of given examples. The reduction of p......-nitrobenzylchloride and subsequent formation of the p-nitrobenzyl radical and the reaction of p-nitrotoluene with O– are studied by resonance Raman and optical absorption spectroscopy....

  19. Resonant Raman Scattering from Silicon Nanoparticles Enhanced by Magnetic Response

    CERN Document Server

    Dmitriev, Pavel A; Milichko, Valentin A; Makarov, Sergey V; Mukhin, Ivan S; Samusev, Anton K; Krasnok, Alexander E; Belov, Pavel A; Kivshar, Yuri S

    2016-01-01

    Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions.

  20. Proliferation detection using a remote resonance Raman chemical sensor

    Energy Technology Data Exchange (ETDEWEB)

    Sedlacek, A.J.; Chen, C.L.; Dougherty, D.R.

    1993-08-01

    The authors discussed the potential of the resonance Raman chemical sensor as a remote sensor that can be used for gases, liquids or solids. This spectroscopy has the fundamental advantage that it is based on optical fingerprints that are insensitive to environmental perturbations or excitation frequency. By taking advantage of resonance enhancement, the inelastic scattering cross-section can increase anywhere from 4 to 6 orders of magnitude which translates into increased sensing range or lower detection limits. It was also shown that differential cross-sections as small as 10{sup {minus}27} cm{sup 2}/sr do not preclude the use of this technique as being an important component in one`s remote-sensing arsenal. The results obtained in the early 1970s on various pollutants and the more recent work on atmospheric water cast a favorable light on the prospects for the successful development of a resonance Raman remote sensor. Currently, of the 20 CW agent-related {open_quotes}signature{close_quotes} chemicals that the authors have investigated, 18 show enhancements ranging from 3 to 6 orders of magnitude. The absolute magnitudes of the measured resonance enhanced Raman cross-sections for these 18 chemicals suggest that detection and identification of trace quantities of the {open_quotes}signature{close_quotes} chemicals, through a remote resonance Raman chemical sensor, could be achieved.

  1. Resonant enhancement of Raman scattering in metamaterials with hybrid electromagnetic and plasmonic resonances

    Science.gov (United States)

    Guddala, Sriram; Narayana Rao, D.; Ramakrishna, S. Anantha

    2016-06-01

    A tri-layer metamaterial perfect absorber of light, consisting of (Al/ZnS/Al) films with the top aluminum layer patterned as an array of circular disk nanoantennas, is investigated for resonantly enhancing Raman scattering from C60 fullerene molecules deposited on the metamaterial. The metamaterial is designed to have resonant bands due to plasmonic and electromagnetic resonances at the Raman pump frequency (725 nm) as well as Stokes emission bands. The Raman scattering from C60 on the metamaterial with resonantly matched bands is measured to be enhanced by an order of magnitude more than C60 on metamaterials with off-resonant absorption bands peaking at 1090 nm. The Raman pump is significantly enhanced due to the resonance with a propagating surface plasmon band, while the highly impedance-matched electromagnetic resonance is expected to couple out the Raman emission efficiently. The nature and hybridization of the plasmonic and electromagnetic resonances to form compound resonances are investigated by numerical simulations.

  2. Resonance Raman spectroscopy in one-dimensional carbon materials

    Directory of Open Access Journals (Sweden)

    Dresselhaus Mildred S.

    2006-01-01

    Full Text Available Brazil has played an important role in the development and use of resonance Raman spectroscopy as a powerful characterization tool for materials science. Here we present a short history of Raman scattering research in Brazil, highlighting the important contributions to the field coming from Brazilian researchers in the past. Next we discuss recent and important contributions where Brazil has become a worldwide leader, that is on the physics of quasi-one dimensional carbon nanotubes. We conclude this article by presenting results from a very recent resonance Raman study of exciting new materials, that are strictly one-dimensional carbon chains formed by the heat treatment of very pure double-wall carbon nanotube samples.

  3. Fast Resonance Raman Spectroscopy of a Free Radical

    DEFF Research Database (Denmark)

    Wilbrandt, Robert Walter; Pagsberg, Palle Bjørn; Hansen, K. B.

    1975-01-01

    The resonance Raman spectrum of a 10−3 molar solution of the stable diphenyl-pikryl-hydrazyl radical in benzene was obtained using a single laser pulse of 10 mJ energy and 600 ns duration from a flashlamp pumped tunable dye laser. Spectra were recorded using an image intensifier coupled to a TV...

  4. Multiphonon Resonance Raman Scattering in InGaN

    Energy Technology Data Exchange (ETDEWEB)

    Ager III, J.W.; Walukiewicz, W.; Shan, W.; Yu, K.M.; Li, S.X.; Haller, E.E.; Lu, H.; Schaff, W.J.

    2005-06-28

    In In{sub x}Ga{sub 1-x}N epitaxial films with 0.37 < x < 1 and free electron concentrations in the 10{sup 18} cm{sup -3} range, strong resonant Raman scattering of A{sub 1}(LO) phonon is observed for laser excitation in Raman scattering when excited above the direct band gaps. Examination of films with direct band gaps between 0.7 and 1.9 eV using laser energies from 1.9 to 2.7 eV shows that the resonance is broad, extending to up to 2 eV above the direct gap. Multiphonon Raman scattering with up to 5 LO phonons is also observed for excitation close to resonance in alloy samples; this is the highest number of phonon overtones ever observed for multiphonon scattering in a III-V compound under ambient conditions. Coupling of the electron plasmon to the LO phonon to form a longitudinal plasmon coupled mode of the type which is observed in the Raman spectra of n-GaN, appears not to occur in In{sub x}Ga{sub 1-x}N for x > 0.37.

  5. Resonance electronic Raman scattering in rare earth crystals

    Energy Technology Data Exchange (ETDEWEB)

    Williams, G.M.

    1988-11-10

    The intensities of Raman scattering transitions between electronic energy levels of trivalent rare earth ions doped into transparent crystals were measured and compared to theory. A particle emphasis was placed on the examination of the effect of intermediate state resonances on the Raman scattering intensities. Two specific systems were studied: Ce/sup 3 +/(4f/sup 1/) in single crystals of LuPO/sub 4/ and Er/sup 3 +/(4f/sup 11/) in single crystals of ErPO/sub 4/. 134 refs., 92 figs., 33 tabs.

  6. Raman Scattering at Resonant or Near-Resonant Conditions: A Generalized Short-Time Approximation

    Institute of Scientific and Technical Information of China (English)

    Abdelsalam Mohammed; Yu-Ping Sun; Quan Miao; Hans (A)gren; Faris Gel'mukhanov

    2012-01-01

    We investigate the dynamics of resonant Raman scattering in the course of the frequency detuning.The dephasing in the time domain makes the scattering fast when the photon energy is tuned from the absorption resonance.This makes frequency detuning to act as a camera shutter with a regulated scattering duration and provides a practical tool of controlling the scattering time in ordinary stationary measurements.The theory is applied to resonant Raman spectra of a couple of few-mode model systems and to trans-1,3,5-hexatriene and guanine-cytosine (G-C) Watson-Crick base pairs (DNA) molecules.Besides some particular physical effects,the regime of fast scattering leads to a simplification of the spectrum as well as to the scattering theory itself.Strong overtones appear in the Raman spectra when the photon frequency is tuned in the resonant region,while in the mode of fast scattering,the overtones are gradually quenched when the photon frequency is tuned more than one vibrational quantum below the first absorption resonance.The detuning from the resonant region thus leads to a strong purification of the Raman spectrum from the contamination by higher overtones and soft modes and purifies the spectrum also in terms of avoidance of dissociation and interfering fluorescence decay of the resonant state.This makes frequency detuning a very useful practical tool in the analysis of the resonant Raman spectra of complex systems and considerably improves the prospects for using the Raman effect for detection of foreign substances at ultra-low concentrations.

  7. A Theoretical Distinction Between Time-Resolved Resonance Raman andResonance Fluorescence

    Institute of Scientific and Technical Information of China (English)

    LU Jing; DU Si-De; FAN Kang-Nian; Lee Soo-Ying

    2000-01-01

    Based on the time-dependent theory, an analysis of the distinction between resonance Raman (RR) and resonance fluorescence (RF) with pulse excitation was presented. The real population of the intermediate state gives two optical components-the independent time evolution of intermediate ket and bra states generates RR while RF originates from the phase coherent between ket and bra states. In cw limit, the transition probability of spontaneous emission with pulse excitation can be reduced to the classical theory.

  8. Brain metastasis detection by resonant Raman optical biopsy method

    Science.gov (United States)

    Zhou, Yan; Liu, Cheng-hui; Cheng, Gangge; Zhou, Lixin; Zhang, Chunyuan; Pu, Yang; Li, Zhongwu; Liu, Yulong; Li, Qingbo; Wang, Wei; Alfano, Robert R.

    2014-03-01

    Resonant Raman (RR) spectroscopy provides an effective way to enhance Raman signal from particular bonds associated with key molecules due to changes on a molecular level. In this study, RR is used for detection of human brain metastases of five kinds of primary organs of lung, breast, kidney, rectal and orbital in ex-vivo. The RR spectra of brain metastases cancerous tissues were measured and compared with those of normal brain tissues and the corresponding primary cancer tissues. The differences of five types of brain metastases tissues in key bio-components of carotene, tryptophan, lactate, alanine and methyl/methylene group were investigated. The SVM-KNN classifier was used to categorize a set of RR spectra data of brain metastasis of lung cancerous tissues from normal brain tissue, yielding diagnostic sensitivity and specificity at 100% and 75%, respectively. The RR spectroscopy may provide new moleculebased optical probe tools for diagnosis and classification of brain metastatic of cancers.

  9. Determination of resonance Raman cross-sections for use in biological SERS sensing with femtosecond stimulated Raman spectroscopy.

    Science.gov (United States)

    Silva, W Ruchira; Keller, Emily L; Frontiera, Renee R

    2014-08-05

    Surface-enhanced Raman spectroscopy (SERS) is a promising technique for in vivo bioanalyte detection, but accurate characterization of SERS biosensors can be challenging due to difficulties in differentiating resonance and surface enhancement contributions to the Raman signal. Here, we quantitate the resonance Raman cross-sections for a commonly used near-infrared SERS dye, 3,3'-diethylthiatricarbocyanine (DTTC). It is typically challenging to measure resonance Raman cross-sections for fluorescent dye molecules due to the overwhelming isoenergetic fluorescence signal. To overcome this issue, we used etalon-based femtosecond stimulated Raman spectroscopy, which is intrinsically designed to acquire a stimulated Raman signal without strong fluorescence or interference from signals resulting from other four-wave mixing pathways. Using this technique, we found that the cross-sections for most of the resonantly enhanced modes in DTTC exceed 10(-25) cm(2)/molecule. These cross-sections lead to high signal magnitude SERS signals from even weakly enhancing SERS substrates, as much of what appears to be a SERS signal is actually coming from the intrinsically strong resonance Raman signal. Our work will lead to a more accurate determination of SERS enhancement factors and SERS substrate characterization in the biologically relevant near-infrared region, ultimately leading to a more widespread use of SERS for biosensing and bioimaging applications.

  10. Resonant Raman Study Of ZnSe Epitaxial Layers Grown On GaAs Substrates

    Science.gov (United States)

    Djibladze, Merab I.; Dorosh, I. I.; Zlenko, A. A.; Kekelidze, George N.; Pashinin, Vladimir P.; Prokhorov, Kirill A.

    1989-05-01

    Quantitative difference between Raman and resonant Raman scattering spectra of thin ZnSe layers on GaAs substrates is presented. The dynamics of changing of Raman scattering properties while shortenning the exciting light wavelength for ZnSe/GaAs heterojunction is given. The difference in polarization spectra is demonstrated.

  11. [Effect on Fermi Resonance by Some External Fields: Investigation of Fermi Resonance According to Raman Spectra].

    Science.gov (United States)

    Jiang, Xiu-lan; Sun, Cheng-lin; Zhou, Mi; Li, Dong-fei; Men, Zhi-wei; Li, Zuo-wei; Gao, Shu-qin

    2015-03-01

    Fermi resonance is a phenomenon of molecular vibrational coupling and energy transfer occurred between different groups of a single molecule or neighboring molecules. Many properties of Fermi resonance under different external fields, the investigation method of Raman spectroscopy as well as the application of Fermi resonance, etc need to be developed and extended further. In this article the research results and development about Fermi resonance obtained by Raman spectral technique were introduced systematically according to our work and the results by other researchers. Especially, the results of the behaviors of intramolecular and intermolecular Fermi resonance of some molecules under some external fields such as molecular field, pressure field and temperature field, etc were investigated and demonstrated in detail according to the Raman spectra obtained by high pressure DAC technique, temperature variation technique as well as the methods we planed originally in our group such as solution concentration variation method and LCOF resonance Raman spectroscopic technique, and some novel properties of Fermi resonance were found firstly. Concretely, (1) Under molecular field. a. The Raman spectra of C5H5 N in CH3 OH and H2O indicates that solvent effect can influence Fermi resonance distinctly; b. The phenomena of the asymmetric movement of the Fermi resonance doublets as well as the fundamental involved is tuned by the Fermi resonance which had not been found by other methods were found firstly by our variation solution concentration method; c. The Fermi resonance properties can be influenced distinctly by the molecular group reorganization induced by the hydrogen bond and anti-hydrogen bond in solution; d. Fermi resonance can occurred between C7 H8 and m-C8H10, and the Fermi resonance properties behave quite differently with the solution concentration; (2) Under pressure field. a. The spectral lines shift towards high wavenumber with increasing pressure, and

  12. Unusual Raman spectra of para-nitroaniline by sequential Fermi resonances.

    Science.gov (United States)

    Xia, Jiarui; Zhu, Ling; Feng, Yanting; Li, Yongqing; Zhang, Zhenglong; Xia, Lixin; Liu, Liwei; Ma, Fengcai

    2014-01-01

    In this communication, we report the unusual Raman spectra of para-nitroaniline (PNA) by sequential Fermi resonances. The combinational mode 1292 cm(-1) in the experimental Raman spectrum indirectly gains the initial spectral weight at 1392 cm(-1) by three sequential Fermi resonances. These Fermi resonances result in the strong interaction between the donor group of NH2 and the acceptor group of NO2. Our theoretical calculations provide reasonable interpretation for the abnormal Raman spectra of PNA. Experimental surface enhanced Raman scattering (SERS) spectrum of PNA further confirmed our conclusion, where the strongest Raman peak at 1292 cm(-1) is very weak, while the Raman peak at 1392 cm(-1) becoming the strongest Raman peak, which is consistent with the theoretical simulations.

  13. Resonance Raman Scattering Studies of Gallium - - Aluminum-Arsenide Superlattices.

    Science.gov (United States)

    Gant, Thomas Andrew

    We have made resonance Raman scattering studies of folded LA phonons and quantized LO phonons in several GaAs-AlAs superlattices. The motivation for this work was to study the electronic structure and the electron -phonon interaction in these structures. The samples were not intentionally doped. The Raman spectra of optic phonons were usually taken at a temperature of 10 K or less. The folded acoustic phonon work was taken at temperatures ranging from 200-300 K in order to enhance the scattering by the thermal factor. Two samples in particular have received very close attention: sample 2292 (50 A GaAs- 20 A AlAs) and sample 3250 (20 A GaAs- 50 A AlAs). In sample 2292 we have made resonance studies of the folded LA phonons and the GaAs -like confined LO_2 mode near the second heavy hole exciton. The results on the folded acoustic phonons show a very strong resonance enhancement for the second order folded phonons, but very little for the first order. An interference between two different scattering channels (the n = 1 light hole and the n = 2 heavy hole subbands) seems to be responsible for this effect. The resonance profile for the LO_2 confined optic phonon in sample 2292 shows 4 peaks in the region from 1.8 eV to 2.05 eV. We have studied the dependence of this resonance profile on the power density. A higher power density was achieved by using the same laser power with a tighter focus. At the higher power density the peak at 1.93 eV (formerly the strongest peak present) vanished. This "bleaching" effect is related to screening due to the higher carrier density. In sample 3250 we have studied the polarization dependence of the resonance profiles of four peaks (LO _2, LO_4, LO_6, and an interface mode) near the lowest direct gap. The A_1 symmetry confined LO modes are seen in both polarized and depolarized geometries, in violation of the usual selection rule (polarized). A mechanism is proposed to explain this result, which has been previously observed by other

  14. Origin invariance in vibrational resonance Raman optical activity

    Energy Technology Data Exchange (ETDEWEB)

    Vidal, Luciano N., E-mail: lnvidal@utfpr.edu.br; Cappelli, Chiara, E-mail: chiara.cappelli@unipi.it [Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 3, 56124 Pisa (Italy); Egidi, Franco [Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States); Barone, Vincenzo [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy)

    2015-05-07

    A theoretical investigation on the origin dependence of the vibronic polarizabilities, isotropic and anisotropic rotational invariants, and scattering cross sections in Resonance Raman Optical Activity (RROA) spectroscopy is presented. Expressions showing the origin dependence of these polarizabilities were written in the resonance regime using the Franck-Condon (FC) and Herzberg-Teller (HT) approximations for the electronic transition moments. Differently from the far-from-resonance scattering regime, where the origin dependent terms cancel out when the rotational invariants are calculated, RROA spectrum can exhibit some origin dependence even for eigenfunctions of the electronic Hamiltonian. At the FC level, the RROA spectrum is completely origin invariant if the polarizabilities are calculated using a single excited state or for a set of degenerate states. Otherwise, some origin effects can be observed in the spectrum. At the HT level, RROA spectrum is origin dependent even when the polarizabilities are evaluated from a single excited state but the origin effect is expected to be small in this case. Numerical calculations performed for (S)-methyloxirane, (2R,3R)-dimethyloxirane, and (R)-4-F-2-azetidinone at both FC and HT levels using the velocity representation of the electric dipole and quadrupole transition moments confirm the predictions of the theory and show the extent of origin effects and the effectiveness of suggested ways to remove them.

  15. Elucidation of Chemical Reactions by Two-Dimensional Resonance Raman Spectroscopy

    Science.gov (United States)

    Moran, Andrew

    Two-dimensional (2D) Raman spectroscopies were proposed by Mukamel and Loring in1985 as a method for resolving line broadening mechanisms of vibrational motions in liquids. Significant technical issues challenged the development of both five- and seven-pulse 2D Raman spectroscopies. For this reason, 2D Raman experiments were largely abandoned in 2002 following the first demonstrations of 2D infrared spectroscopies (i.e., an alternate approach for obtaining similar information). We have recently shown that 2D Raman experiments conducted under electronically resonant conditions are much less susceptible to the problems encountered in the earlier 2D Raman work, which was carried out off-resonance. In effect, Franck-Condon activity obviates the problematic selection rules encountered under electronically off-resonant conditions. In this presentation, I will discuss applications of 2D resonance Raman spectroscopies to photodissocation reactions of triiodide and myoglobin. It will be shown that vibrational resonances of the reactants and products can be displayed in separate dimensions of a 2D resonance Raman spectrum when the photo-dissociation reaction is fast compared to the vibrational period. Such 2D spectra expose correlations between the nonequilibrium geometry of the reactant and the distribution of vibrational quanta in the product, thereby yielding insight in the photo-dissociation mechanism. Our results suggest that the ability of 2D resonance Raman spectroscopy to detect correlations between reactants and products will generalize to other ultrafast processes such as electron transfer and energy transfer.

  16. Resonance Raman spectra of black soap film containing dye molecule

    Institute of Scientific and Technical Information of China (English)

    梁映秋; 张韫宏

    1995-01-01

    Dye molecule brilliant yellow (BY) has been used as an acid-base probe in the study of the resonance Raman spectra of three kinds of microenvironments of the black soap film (BSF) containing BY, the BY-CTAB micellar solution, and the aqueous BY solution under various pH conditions. It has been revealed that BY bound to the sandwich interface of the BSF and that to the micellar interface show similar spectral changes, but the former owns the character of coexistence of acidic and basic structures in a relatively large range of pH values (neutral to basic). Further investigations have demonstrated that BSF exhibits the buffer effect that the pH value of the aqueous core is insensitive to the pH change of the bulk solution.

  17. Single-Molecule Surface-Enhanced Raman Scattering Spectrum of Non-Resonant Aromatic Amine Showing Raman Forbidden Bands

    CERN Document Server

    Yamamoto, Yuko S; Ozaki, Yukihiro; Zhang, Zhenglong; Kozu, Tomomi; Itoh, Tamitake; Nakanishi, Shunsuke

    2016-01-01

    We present the experimentally obtained single-molecule (SM) surface-enhanced Raman scattering (SERS) spectrum of 4-aminibenzenethiol (4-ABT), also known as para-aminothiophenol (PATP). Measured at a 4-ABT concentration of 8 * 10^-10 M, the spectra show Raman forbidden modes. The SM-SERS spectrum of 4-ABT obtained using a non-resonant visible laser is different from the previously reported SERS spectra of 4-ABT, and could not be reconstructed using quantum mechanical calculations. Careful classical assignments (not based on quantum-mechanical calculations) are reported, and indicate that differences in the reported spectra of 4-ABT are mainly due to the appearance of Raman forbidden bands. The presence of Raman forbidden bands can be explained by the charge-transfer (CT) effect of 4-ABT adsorbed on the silver nanostructures, indicating a breakdown of Raman selection rules at the SERS hotspot.

  18. The Role of Fermi Resonance in Formation of Valence Band of Water Raman Scattering

    Directory of Open Access Journals (Sweden)

    Sergey A. Burikov

    2008-01-01

    Full Text Available The role of Fermi resonance in formation of valence band of water Raman scattering was investigated. Simultaneous measurement of characteristics of bending and valence bands of water in D2O solutions, KBr, and KCl and using genetic algorithms in conjunction with variation methods allowed increasing accuracy of estimation of Fermi resonance coupling constant and of Fermi resonance contribution into formation of water Raman valence band.

  19. Rapidly reconfigurable slow-light system based on off-resonant Raman absorption

    Science.gov (United States)

    Vudyasetu, Praveen K.; Camacho, Ryan M.; Howell, John C.

    2010-11-01

    We present a slow-light system based on dual Raman absorption resonances in warm rubidium vapor. Each Raman absorption resonance is produced by a control beam in an off-resonant Λ system. This system combines all optical control of the Raman absorption and the low-dispersion broadening properties of the double Lorentzian absorption slow light. The bandwidth, group delay, and central frequency of the slow-light system can all be tuned dynamically by changing the properties of the control beam. We demonstrate multiple pulse delays with low distortion and show that such a system has fast switching dynamics and thus fast reconfiguration rates.

  20. High-sensitivity pesticide detection using particle-enhanced resonant Raman scattering

    Science.gov (United States)

    Ranjan, Bikas; Saito, Yuika; Verma, Prabhat

    2016-03-01

    The use of pesticides in agriculture has raised concerns, as even a small residual of pesticide on food can be harmful. It is therefore of great importance to develop a robust technique to detect tiny amounts of pesticides. Although Raman spectroscopy is frequently used for chemical identification, it is not suitable for extremely low molecular concentrations. We propose a technique called particle-enhanced resonant Raman spectroscopy to detect extremely low concentrations of pesticides, where gold nanoparticles of desired plasmonic resonance are synthesized to match the resonance in Raman scattering. We successfully demonstrated the detection of extremely low amounts of pesticides on oranges.

  1. Role of multipolar plasmon resonances during surface-enhanced Raman spectroscopy on Au micro-patches

    DEFF Research Database (Denmark)

    Dowd, Annette; Geisler, Mathias; Zhu, Shaoli;

    2016-01-01

    The enhancement of a Raman signal by multipolar plasmon resonances – as opposed to the more common practice of using dipolar resonances – is investigated. A wide range of gold stars, triangles, circles and squares with multipolar resonances in the visible region were designed and then produced...

  2. Strong overtones and combination bands in ultraviolet resonance Raman spectroscopy.

    Science.gov (United States)

    Efremov, Evtim V; Ariese, Freek; Mank, Arjan J G; Gooijer, Cees

    2006-05-01

    Ultraviolet resonance Raman spectroscopy is carried out using a continuous wave frequency-doubled argon ion laser operated at 229, 244, and 257 nm in order to characterize the overtones and combination bands for several classes of organic compounds in liquid solutions. Contrary to what is generally anticipated, for molecules such as pyrene and anthracene, strong overtones and combination bands can show up; it is demonstrated that their intensity depends critically on the applied laser wavelength. If the excitation wavelength corresponds with a purely electronic transition--this applies to a good approximation for 244-nm excitation in the case of pyrene and for 257-nm excitation in the case of anthracene--mostly fundamental vibrations (up to 1700 cm(-1)) are observed. Overtones and combination bands are detected but are rather weak. However, if the laser overlaps with the vibronic region--as holds for 229- and 257-nm excitation for pyrene and 244-nm excitation for anthracene--very strong bands are found in the region 1700-3400 cm(-1). As illustrated for pyrene at 257 nm, all these bands can be assigned to first overtones or binary combinations of fundamental vibrations. Their intensity distribution can roughly be simulated by multiplying the relative intensities of the fundamental bands. Significant bands can also be found in the region 3400-5000 cm(-1), corresponding with second overtones and ternary combinations. It is shown that these findings are not restricted to planar and rigid molecules with high symmetry. Substituted pyrenes exhibit similar effects, and relatively strong overtones are also observed for adenosine monophosphate and for abietic acid. The reasons for these observations are discussed, as well as the potential applicability for analytical purposes.

  3. Resonance Raman Probes for Organelle-Specific Labeling in Live Cells

    Science.gov (United States)

    Kuzmin, Andrey N.; Pliss, Artem; Lim, Chang-Keun; Heo, Jeongyun; Kim, Sehoon; Rzhevskii, Alexander; Gu, Bobo; Yong, Ken-Tye; Wen, Shangchun; Prasad, Paras N.

    2016-06-01

    Raman microspectroscopy provides for high-resolution non-invasive molecular analysis of biological samples and has a breakthrough potential for dissection of cellular molecular composition at a single organelle level. However, the potential of Raman microspectroscopy can be fully realized only when novel types of molecular probes distinguishable in the Raman spectroscopy modality are developed for labeling of specific cellular domains to guide spectrochemical spatial imaging. Here we report on the design of a next generation Raman probe, based on BlackBerry Quencher 650 compound, which provides unprecedentedly high signal intensity through the Resonance Raman (RR) enhancement mechanism. Remarkably, RR enhancement occurs with low-toxic red light, which is close to maximum transparency in the biological optical window. The utility of proposed RR probes was validated for targeting lysosomes in live cultured cells, which enabled identification and subsequent monitoring of dynamic changes in this organelle by Raman imaging.

  4. Signal enhancement of surface enhanced Raman scattering and surface enhanced resonance Raman scattering using in situ colloidal synthesis in microfluidics.

    Science.gov (United States)

    Wilson, Rab; Bowden, Stephen A; Parnell, John; Cooper, Jonathan M

    2010-03-01

    We demonstrate the enhanced analytical sensitivity of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) responses, resulting from the in situ synthesis of silver colloid in a microfluidic flow structure, where both mixing and optical interrogation were integrated on-chip. The chip-based sensor was characterized with a model Raman active label, rhodamine-6G (R6G), and had a limit of detection (LOD) of ca. 50 fM (equivalent to single molecule detection). The device was also used for the determination of the natural pigment, scytonemin, from cyanobacteria (as an analogue for extraterrestrial life existing in extreme environments). The observed LOD of approximately 10 pM (ca. microfluidic system than those measured using the same experimental parameters, with colloid synthesized off-chip, under quiescent conditions.

  5. Resonance Raman kinetic spectroscopy of bacteriorhodopsin on the microsecond time scale

    Energy Technology Data Exchange (ETDEWEB)

    Campion, A.; El-Sayed, M.A.; Terner, J.

    1977-12-01

    Using a rotating disk with a slit of variable width, a continuous wave argon ion laser, and an Optical Multichanel Analyzer for detection, a new technique is reported which should, in principle, be capable of recording resonance Raman spectra with time resolution of 100 ns. The resonance Raman spectra of the intermediates of the photosynthetic cycle of bacteriorhodopsin are recorded on the microsecond time scale. Both the kinetic results and the resonance enhancement profile suggest that deprotonation results in an intermediate preceding bM/sub 412/ that has an optical absorption maximum at a wavelength longer than that of bM/sub 412/.

  6. High-resolution inverse Raman and resonant-wave-mixing spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rahn, L.A. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    These research activities consist of high-resolution inverse Raman spectroscopy (IRS) and resonant wave-mixing spectroscopy to support the development of nonlinear-optical techniques for temperature and concentration measurements in combustion research. Objectives of this work include development of spectral models of important molecular species needed to perform coherent anti-Stokes Raman spectroscopy (CARS) measurements and the investigation of new nonlinear-optical processes as potential diagnostic techniques. Some of the techniques being investigated include frequency-degenerate and nearly frequency-degenerate resonant four-wave-mixing (DFWM and NDFWM), and resonant multi-wave mixing (RMWM).

  7. Nonlinearity in Intensity versus Concentration Dependence for the Deep UV Resonance Raman Spectra of Toluene and Heptane

    DEFF Research Database (Denmark)

    Liu, Chuan; Berg, Rolf W.

    2013-01-01

    by absorption and Resonance Raman effects. Raman spectra of toluene and heptane mixtures - with progressively increasing concentrations of heptane - were measured by use of 229 nm excitation. The results show that the characteristic band intensities are not directly proportional to the relative concentrations...... of the compounds and deviate due to absorption resonance effects. An approximated mathematical model is developed to demonstrate that the intensities of the normal Raman scattering bands are suppressed. An inhibition coefficient Ki is introduced to describe the situation and determine the penetration depth. Most......The relation between Raman scattering, resonance Raman scattering and absorption is reviewed to see to what extent quantitative analysis can be applied in Resonance Raman spectroscopy. In addition to this it is demonstrated experimentally that normal Raman spectra can be dramatically inhibited...

  8. Communication: Significant contributions of Albrecht's $A$ term to non-resonant Raman scattering processes

    CERN Document Server

    Duan, Sai; Luo, Yi

    2015-01-01

    The Raman intensity can be well described by the famous Albrecht equation that consists of $A$ and $B$ terms. It has become a textbook knowledge that the contribution from Albrecht's $A$ term can be neglected without loss of accuracy for non-resonant Raman scattering processes. However, as demonstrated in this study, we have found that this widely accepted long-standing assumption fails drastically for totally symmetric vibration modes of molecules. Perturbed first principles calculations for water molecule show that strong constructive interference between the $A$ and $B$ terms occurs for the Raman intensity of the symmetric O-H stretching mode, which can account for about 40% of the total intensity. Meanwhile, a minor destructive interference is found for the angle bending mode. The state to state mapping between the Albrecht's theory and the perturbation theory allows us to verify the accuracy of the widely employed perturbation method for the dynamic/resonant Raman intensities. The model calculations show...

  9. Boosting the Amount of Molecular Information Through Polarized Resolved Resonance Raman Scattering

    DEFF Research Database (Denmark)

    Hassing, Søren

    2017-01-01

    and near-infrared absorption spectroscopy, i.e. only the spectral distribution is analysed. The goal of the present chapter is to demonstrate that the amount of molecular information (also for solutions and powders) can be increased considerably by analysing also the polarization of the Raman and resonance......Vibrational Raman spectroscopy, one of the experimental techniques available, is applied for characterization and analysis of molecular samples in different areas such as medical, food and environmental analysis. Application of the Raman technique is mostly similar to the application of infrared...

  10. Multi-wavelength resonance Raman spectroscopy of bacteria to study the effects of growth condition

    Science.gov (United States)

    Kunapareddy, Nagapratima; Grun, Jacob; Lunsford, Robert; Gillis, David; Nikitin, Sergei; Wang, Zheng

    2012-06-01

    We will examine the use of multi-wavelength UV resonance-Raman signatures to identify the effects of growth phase on different types of bacteria. Gram positive and gram-negative species, Escherichia coli, Bacillus cereus, Citrobacter koseri and Citrobacter braakii were grown to logarithmic and stationary phases in different culture media. Raman spectra of bacteria were obtained by sequential illumination of samples between 220 and 260 nm; a range which encompasses the resonance frequencies of cellular components. In addition to the information contained in the single spectrum, this two-dimensional signature contains information reflecting variations in resonance cross sections with illumination wavelength. Results of our algorithms in identifying the differences between these germs are discussed. Preliminary results indicate that growth affects the Raman signature, but not to an extent that would negate identification of the species.

  11. Surface-enhanced resonance Raman spectroscopy of copper chlorophyllin on silver and gold colloids

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, P.; Spiro, T.G.

    1988-06-16

    Surface-enhanced resonance Raman spectra (SERRS) are reported for copper chlorophyllin a (CuChl) adsorbed on silver and gold colloids. The surface species are shown to be monomeric, by comparison with solution resonance Raman (RR) spectra, although lowering the pH of the gold colloid to 2.0 induces spectral changes suggestive of surface aggregation. The similarity of CuChl monomer RR and SERRS spectra is consistent with electromagnetic enhancement of the RR spectra via the metal particles, with no indication of a chemical interaction that would perturb the electronic states. The SERRS spectra change markedly with excitation wavelength in ways that can be explained on the basis of the different Raman enhancement pattern expected for resonance with the different chlorin excited states. The SERRS spectra are highly resolved and are useful in suggesting new assignments for chlorin vibrational modes.

  12. Multiwavelength Resonance Raman Characterization of the Effect of Growth Phase and Culture Medium on Bacteria.

    Science.gov (United States)

    Kunapareddy, Nagapratima; Grun, Jacob; Lunsford, Robert; Nikitin, Sergei; Wang, Zheng; Gillis, David

    2015-08-01

    We examine the use of multiwavelength ultraviolet (UV) resonance-Raman signatures to identify the effects of growth phase and growth medium on gram-positive and gram-negative bacteria. Escherichia coli (E. coli), Citrobacter koseri (C. koseri), Citrobacter braakii (C. braakii), and Bacillus cereus (B. cereus) were grown to logarithmic and stationary phases in nutrient broth and brain heart infusion broth. Resonance Raman spectra of bacteria were obtained at multiple wavelengths between 220 and 260 nm; a range that encompasses the resonance frequencies of cellular constituents. We find that spectra of the same bacterial species exhibit differences due to both growth condition and growth phase, but the larger differences reflect changes due to growth phase. The differences in the Raman spectra correlate with genetic differences among the species. Using a Pearson correlation based algorithm, we achieve successful identification of these bacteria in 83% of the cases.

  13. NONLINEAR OPTICS: Stimulated resonant hyper-Raman scattering of light by polaritons in alkali metal vapors

    Science.gov (United States)

    Galaĭchuk, Yu A.; Yashkir, Yu N.

    1989-12-01

    A theory is developed for the calculation of the gain g due to stimulated resonant hyper-Raman scattering of light by polaritons in gaseous media. It is shown that throughout the tuning range of the pump frequency (including one- and two-photon resonances) a maximum of g corresponds to a dispersion curve of polaritons plotted ignoring attenuation. Theoretical results are used to analyze characteristics of hyper-Raman scattering in sodium vapor. It is shown that under normal experimental conditions the splitting of polariton branches is considerable (amounting to tens of reciprocal centimeters on the frequency scale and several angular degrees). The value of g is estimated for two-photon resonances in the case when the pump frequency is tunable in a wide range. The optimal conditions for stimulated hyper-Raman scattering are identified.

  14. Resonance Raman measurements of carotenoids using light emitting diodes

    CERN Document Server

    Bergeson, S D; Eyring, N J; Fralick, J F; Stevenson, D N; Ferguson, S B

    2008-01-01

    We report on the development of a compact commercial instrument for measuring carotenoids in skin tissue. The instrument uses two light emitting diodes (LEDs) for dual-wavelength excitation and four photomultiplier tubes for multichannel detection. Bandpass filters are used to select the excitation and detection wavelengths. The f/1.3 optical system has high optical throughput and single photon sensitivity, both of which are crucial in LED-based Raman measurements. We employ a signal processing technique that compensates for detector drift and error. The sensitivity and reproducibility of the LED Raman instrument compares favorably to laser-based Raman spectrometers. This compact, portable instrument is used for non-invasive measurement of carotenoid molecules in human skin with a repeatability better than 10%.

  15. Effects of inhomogeneous broadening on the resonance Raman excitation profile of lycopene

    Science.gov (United States)

    Cotting, J. E.; Hoskins, L. C.; Levan, M. E.

    1982-08-01

    The resonance Raman excitation profiles for the ν1, ν2, and ν3 vibrations of lycopene in ethyl alcohol, toluene, and carbon disulfide solvents have been measured. The results are interpreted in terms of a three-mode vibrational theory which includes both homogeneous and inhomogeneous broadening effects. Excellent agreement between calculated and observed excitation profiles and visible spectra was found, thus emphasizing the need to interpret resonance Raman data using a multimode vibrational model. The results indicate that the major broadening mechanism is homogeneous broadening, with about a 25% contribution from inhomogeneous broadening. The excitation profiles in carbon disulfide gave the largest inhomogeneous broadening.

  16. Monitoring and trace detection of hazardous waste and toxic chemicals using resonance Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sedlacek, A.J. III; Dougherty, D.R.; Chen, C.L.

    1993-04-01

    Raman scattering is a coherent, inelastic, two-photon process, which shifts the frequency of an outgoing photon according to the vibrational structure of the irradiated species, thereby providing a unique fingerprint of the molecule. When involving an allowed electronic transition (resonance Raman), this scattering cross section can be enhanced by 10{sup 4} to 10{sup 6} and provides the basis for a viable technique that can monitor and detect trace quantities of hazardous wastes and toxic chemicals. Resonance Raman spectroscopy (RRS) possesses many of the ideal characteristics for monitoring and detecting of hazardous waste and toxic chemicals. Some of these traits are: (1) very high selectivity (chemical specific fingerprints); (2) independence from the excitation wavelength (ability to monitor in the solar blind region); (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk); (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid and solutions -- either bulk or aerosols); and (5) insensitivity of the Raman signature to environmental conditions (no quenching). Data from a few chemicals will be presented which illustrate these features. In cases where background fluorescence accompanies the Raman signals, an effective frequency modulation technique has been developed, which can completely eliminate this interference.

  17. Monitoring and trace detection of hazardous waste and toxic chemicals using resonance Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sedlacek, A.J. III; Dougherty, D.R.; Chen, C.L.

    1993-01-01

    Raman scattering is a coherent, inelastic, two-photon process, which shifts the frequency of an outgoing photon according to the vibrational structure of the irradiated species, thereby providing a unique fingerprint of the molecule. When involving an allowed electronic transition (resonance Raman), this scattering cross section can be enhanced by 10[sup 4] to 10[sup 6] and provides the basis for a viable technique that can monitor and detect trace quantities of hazardous wastes and toxic chemicals. Resonance Raman spectroscopy (RRS) possesses many of the ideal characteristics for monitoring and detecting of hazardous waste and toxic chemicals. Some of these traits are: (1) very high selectivity (chemical specific fingerprints); (2) independence from the excitation wavelength (ability to monitor in the solar blind region); (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk); (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid and solutions -- either bulk or aerosols); and (5) insensitivity of the Raman signature to environmental conditions (no quenching). Data from a few chemicals will be presented which illustrate these features. In cases where background fluorescence accompanies the Raman signals, an effective frequency modulation technique has been developed, which can completely eliminate this interference.

  18. Atmospheric absorption versus deep ultraviolet (pre-)resonance in Raman lidar measurements

    Science.gov (United States)

    Hallen, Hans D.; Willitsford, Adam H.; Neely, Ryan R.; Chadwick, C. Todd; Philbrick, C. Russell

    2016-05-01

    The Raman scattering of several liquids and solid materials has been investigated near the deep ultraviolet absorption features corresponding to the electron energy states of the chemical species present. It is found to provide significant enhancement, but is always accompanied by absorption due to that or other species along the path. We investigate this trade-off for water vapor, although the results for liquid water and ice will be quantitatively very similar. An optical parametric oscillator (OPO) was pumped by the third harmonic of a Nd:YAG laser, and the output frequency doubled to generate a tunable excitation beam in the 215-600 nm range. We use the tunable laser excitation beam to investigate pre-resonance and resonance Raman spectroscopy near an absorption band of ice. A significant enhancement in the Raman signal was observed. The A-term of the Raman scattering tensor, which describes the pre-resonant enhancement of the spectra, is also used to find the primary observed intensities as a function of incident beam energy, although a wide resonance structure near the final-state-effect related absorption in ice is also found. The results suggest that use of pre-resonant or resonant Raman LIDAR could increase the sensitivity to improve spatial and temporal resolution of atmospheric water vapor measurements. However, these shorter wavelengths also exhibit higher ozone absorption. These opposing effects are modeled using MODTRAN for several configurations relevant for studies of boundary layer water and in the vicinity of clouds. Such data could be used in studies of the measurement of energy flow at the water-air and cloud-air interface, and may help with understanding some of the major uncertainties in current global climate models.

  19. Phase-locking transition in Raman combs generated with whispering gallery mode resonators.

    Science.gov (United States)

    Lin, Guoping; Chembo, Yanne K

    2016-08-15

    We investigate the mechanisms leading to phase locking in Raman optical frequency combs generated with ultrahigh Q crystalline whispering gallery mode disk resonators. We show that several regimes can be triggered depending on the pumping conditions, such as single-frequency Raman lasing, multimode operation involving more than one family of cavity eigenmodes, and Kerr-assisted Raman frequency comb generation. The phase locking and coherence of the combs are experimentally monitored through the measurement of beat signal spectra. These phase-locked combs, which feature high coherence and wide spectral spans, are obtained with pump powers in the range of a few tens of mW. In particular, Raman frequency combs with multiple free-spectral range spacings are reported, and the measured beat signal in the microwave domain features a 3 dB linewidth smaller than 50 Hz, thereby indicating phase locking.

  20. Resonance raman and absorption spectra of isomeric retinals in their lowest excited triplet states

    DEFF Research Database (Denmark)

    Wilbrandt, Robert Walter; Jensen, N.-H.; Houee-Levin, C.

    1985-01-01

    implications about the size of the energy barriers separating the various triplet species are discussed. The resonance Raman spectra obtained by using either anthracene (ET = 177.7 kJ mol-1) or naphthalene (ET = 254.8 kJ mol-1) as sensitizers were virtually identical for the corresponding triplet states from...

  1. Electro-Optical Multichannel Spectrometer for Transient Resonance Raman and Absorption Spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Karina Benthin; Wilbrandt, Robert Walter; Pagsberg, Palle Bjørn

    1979-01-01

    An optical multichannel system is described, used for time‐dependent absorption measurements in the gas phase and the liquid phase and for resonance Raman spectroscopy of short‐lived transient species in the liquid phase in pulse radiolysis. It consists of either an image converter streak unit or...

  2. Resonance Raman Spectra of the Transient Cl2 and Br2 Radical Anions

    DEFF Research Database (Denmark)

    Wilbrandt, Robert Walter; Jensen, Niels-Henrik; Sillesen, Alfred Hegaard

    1984-01-01

    The resonance Raman spectra of the short-lived radical anions ClImage 2− and BrImage − in aqueous solution are reported. The observed wavenumbers of 279 cm−1 for ClImage − and 177 cm−1 for BrImage − are about 10% higher than those published for the corresponding species isolated in solid argon...

  3. Calculation of optical absorption and resonance Raman correlators using time-dependent recursion relationships

    DEFF Research Database (Denmark)

    Svendsen, Christian; Mortensen, O. Sonnich; Henriksen, Niels Engholm

    1996-01-01

    Time-dependent recursion relationships are derived for optical absorption and resonance Raman correlators in the multidimensional harmonic case using a second-quantization formalism. Furthermore, a procedure is given for the calculation of correlators involving a general analytic coordinate depen...... dependence of the transition dipole moment....

  4. Resonance Raman Spectroscopy of Beta-Carotene and Lycopene: A Physical Chemistry Experiment.

    Science.gov (United States)

    Hoskins, L. C.

    1984-01-01

    Discusses the theory of resonance Raman (RR) spectroscopy as it applies to beta-carotene and lycopene pigments (found in tomatoes and carrots, respectively). Also discusses an experiment which demonstrates the theoretical principles involved. The experiment has been tested over a three-year period and has received excellent acceptance by physical…

  5. Resonance Raman investigation of the radical cation of 1,3,5-hexatriene

    DEFF Research Database (Denmark)

    Keszhelyi, T.; Wilbrandt, R.; Cave, R.J.;

    1994-01-01

    of more than one rotamer has to be assumed to account for all the observed resonance Raman bands. The bands are assigned to a mixture of the two rotamers, calculated at lowest energy, the ttt and tct rotamers, on the basis of ab initio ROHF/6-31G calculated harmonic frequencies. The spectrum indicates...

  6. Resonance Raman Spectroscopic and Theoretical Study of Geometry Distortion of Thiourea in 21A State

    Institute of Scientific and Technical Information of China (English)

    Hai-bo Zhang; Yan-ying Zhao; Xu-ming Zheng

    2012-01-01

    The A-band resonance Raman spectra of thiourea were obtained in water and acetonitrile solution.B3LYP/6-311++G(3df,3pd) and RCIS/6-311++G(3df,3pd) calculations were done to elucidate the ultraviolet electronic transitions,the distorted geometry structure and the saddle point of thiourea in 21A excited state,respectively.The resonance Raman spectra were assigned.The absorption spectrum and resonance Raman intensities were modeled using Heller's time-dependent wavepacket approach to resonance Raman scattering.The results indicate that largest change in the displacement takes place with the C=S stretch mode v6 (|Δ|=0.95) and noticeable changes appear in the HsN3H6+H8N4H7 wag v5 (|Δ|=0.19),NCN symmetric stretch+C=S stretch+N3H6+H8N4 wag v4 (|Δ|=0.18),while the moderate intensities of 2v15 and 4v15 are mostly due to the large excited state frequency changes of v15,but not due to its significant change in the normal mode displacement.The mechanism of the appearance of even overtones of the S=CN2 out of plane deformation is explored.The results indicate that a Franck-Condon region saddle point is the driving force for the quadric phonon mechanism within the standard A-term of resonance Raman scattering,which leads to the pyramidalization of the carbon center and the geometry distortion of thiourea molecule in 21A excited state.

  7. Raman scattering enhancement in photon-plasmon resonance mediated metal-dielectric microcavity

    Science.gov (United States)

    Guddala, Sriram; Dwivedi, Vindesh K.; Vijaya Prakash, G.; Narayana Rao, D.

    2013-12-01

    Here, we report the photon-plasmon interaction scheme and enhanced field strengths resulted into the amplification of phonon in a novel microcavity. A metal-dielectric microcavity, with unified cavity photonic mode and localized surface plasmon resonances, is visualized by impregnating the gold nanoparticles into the deep see-through nano-sized pores of porous silicon microcavity. The intense optical field strengths resulting from the photon-plasmon interactions are probed by both resonant and non-resonant Raman scattering experiments. Due to photon-plasmon-phonon interaction mechanism, several orders of enhancement in the intensity of scattered Raman Stokes photon (at 500 cm-1) are observed. Our metal nanoparticle-microcavity hybrid system shows the potential to improve the sensing figure of merit as well as the applications of plasmonics for optoelectronics, photovoltaics, and related technologies.

  8. Raman scattering enhancement in photon-plasmon resonance mediated metal-dielectric microcavity

    Energy Technology Data Exchange (ETDEWEB)

    Guddala, Sriram; Narayana Rao, D., E-mail: dnr.laserlab@gmail.com, E-mail: dnrsp@uohyd.ernet.in [School of Physics, University of Hyderabad, Hyderabad 500 046 (India); Dwivedi, Vindesh K.; Vijaya Prakash, G. [Nanophotonics Laboratory, Department of Physics, IIT Delhi, New Delhi 110 016 (India)

    2013-12-14

    Here, we report the photon-plasmon interaction scheme and enhanced field strengths resulted into the amplification of phonon in a novel microcavity. A metal-dielectric microcavity, with unified cavity photonic mode and localized surface plasmon resonances, is visualized by impregnating the gold nanoparticles into the deep see-through nano-sized pores of porous silicon microcavity. The intense optical field strengths resulting from the photon-plasmon interactions are probed by both resonant and non-resonant Raman scattering experiments. Due to photon-plasmon-phonon interaction mechanism, several orders of enhancement in the intensity of scattered Raman Stokes photon (at 500 cm{sup −1}) are observed. Our metal nanoparticle-microcavity hybrid system shows the potential to improve the sensing figure of merit as well as the applications of plasmonics for optoelectronics, photovoltaics, and related technologies.

  9. Effect of atomic diffusion on the Raman-Ramsey CPT resonances

    CERN Document Server

    Kuchina, Elena; Novikova, Irina

    2015-01-01

    We experimentally investigated the characteristics of two-photon transmission resonances in Rb vapor cells with different amount of buffer gas under the conditions of steady-state coherent population trapping (CPT) and pulsed Raman-Ramsey (RR-) CPT interrogation scheme. We particularly focused on the influence of the Rb atoms diffusing in and out of the laser beam. We showed that this effect modifies the shape of both CPT and Raman-Ramsey resonances, as well as their projected performance for CPT clock applications. In particular we found that at moderate buffer gas pressures RR-CPT did not improved the projected atomic clock stability compare to the regular steady-state CPT resonance.

  10. Resonance-Enhanced Raman Spectroscopy on Explosives Vapor at Standoff Distances

    Directory of Open Access Journals (Sweden)

    Anneli Ehlerding

    2012-01-01

    Full Text Available Resonance-enhanced Raman spectroscopy has been used to perform standoff measurements on nitromethane (NM, 2,4-DNT, and 2,4,6-TNT in vapor phase. The Raman cross sections for NM, DNT, and TNT in vapor phase have been measured in the wavelength range 210–300 nm under laboratory conditions, in order to estimate how large resonance enhancement factors can be achieved for these explosives. The results show that the signal is enhanced up to 250,000 times for 2,4-DNT and up to 60,000 times for 2,4,6-TNT compared to the nonresonant signal at 532 nm. Realistic outdoor measurements on NM in vapor phase at 13 m distance were also performed, which indicate a potential for resonance Raman spectroscopy as a standoff technique for detection of vapor phase explosives. In addition, the Raman spectra of acetone, ethanol, and methanol were measured at the same wavelengths, and their influence on the spectrum from NM was investigated.

  11. Resonance Raman scattering and excitonic spectra in TlInS{sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zalamai, V.V. [Institute of Applied Physics, Academy of Sciences of Moldova, 5 Academy Street, 2028 Chisinau, Republic of Moldova (Moldova, Republic of); Stamov, I.G. [T.G. Shevchenko State University of Pridnestrovie, 25 Oktyabrya Street 107, 3300 Tiraspol, Republic of Moldova (Moldova, Republic of); Syrbu, N.N., E-mail: sirbunn@yahoo.com [Technical University of Moldova, 168 Stefan cel Mare Avenue, 2004 Chisinau, Republic of Moldova (Moldova, Republic of); Ursaki, V.V. [Institute of Applied Physics, Academy of Sciences of Moldova, 5 Academy Street, 2028 Chisinau, Republic of Moldova (Moldova, Republic of); Dorogan, V. [Technical University of Moldova, 168 Stefan cel Mare Avenue, 2004 Chisinau, Republic of Moldova (Moldova, Republic of)

    2015-04-15

    The excitons ground and excited states for E∥a and E∥b polarizations in absorption and reflection spectra of TlInS{sub 2} crystals were detected. The fundamental parameters of excitons and bands were determined at k=0. The resonance Raman spectra were investigated in the region of excitons transitions. The resonance Raman scattering spectra with participation of optical phonons that are active at the center of Brillouin zone were identified. The Raman scattering in Y(YX)Z and Y(ZX)Z geometries at 10 K with excitation by He–Ne laser was researched. Energies of phonons with A{sub g} and B{sub g} symmetries were determined. It was shown that the number of modes at 10 K was two times lower than expected according to theoretical calculations. - Highlights: • The resonance Raman scattering in geometry Y(YX)Z and Y(ZX)Z at 10 K was investigated. • Energies of phonons with A{sub g} and B{sub g} symmetries were determined. • The experimental and theoretical calculations completely conform if crystals are described by symmetry group D{sub 4h}{sup 15}. • The main parameters of excitons and bands were determined. • The model of electron transitions in k=0 was suggested.

  12. Development of a fiber based Raman probe compatible with interventional magnetic resonance imaging

    Science.gov (United States)

    Ashok, Praveen C.; Praveen, Bavishna B.; Rube, Martin; Cox, Benjamin; Melzer, Andreas; Dholakia, Kishan

    2014-02-01

    Raman spectroscopy has proven to be a powerful tool for discriminating between normal and abnormal tissue types. Fiber based Raman probes have demonstrated its potential for in vivo disease diagnostics. Combining Raman spectroscopy with Magnetic Resonance Imaging (MRI) opens up new avenues for MR guided minimally invasive optical biopsy. Although Raman probes are commercially available, they are not compatible with a MRI environment due to the metallic components which are used to align the micro-optic components such as filters and lenses at the probe head. Additionally they are not mechanically compatible with a typical surgical environment as factors such as sterility and length of the probe are not addressed in those designs. We have developed an MRI compatible fiber Raman probe with a disposable probe head hence maintaining sterility. The probe head was specially designed to avoid any material that would cause MR imaging artefacts. The probe head that goes into patient's body had a diameter biopsy needles and catheters. The probe has been tested in MR environment and has been proven to be capable of obtaining Raman signal while the probe is under real-time MR guidance.

  13. Demonstration of resonant backward Raman amplification in high-density gas-jet plasma

    Science.gov (United States)

    Wu, Z. H.; Zhou, K. N.; Zheng, X. M.; Wei, X. F.; Zhu, Q. H.; Su, J. Q.; Xie, N.; Jiao, Z. H.; Peng, H.; Wang, X. D.; Sun, L.; Li, Q.; Huang, Z.; Zuo, Y. L.

    2016-10-01

    Backward Raman amplification was observed in a 0.7 mm-long high-density gas jet plasma. The 800 nm 30 fs seed pulse was amplified by a factor  ∼28, with an output energy of 2.8 mJ. The output spectra showed that the waveband around 800 nm was significantly amplified. The experimental result demonstrated that the resonant Raman amplification can be realized in high-density plasma against strong plasma instability.

  14. One phonon resonant Raman scattering in semiconductor quantum wires: Magnetic field effect

    Energy Technology Data Exchange (ETDEWEB)

    Betancourt-Riera, Re., E-mail: rbriera@posgrado.cifus.uson.mx [Instituto Tecnologico de Hermosillo, Avenida Tecnologico S/N, Colonia Sahuaro, C.P. 83170, Hermosillo, Sonor, (Mexico); Departamento de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, C.P. 83190, Hermosillo, Sonora (Mexico); Betancourt-Riera, Ri. [Instituto Tecnologico de Hermosillo, Avenida Tecnologico S/N, Colonia Sahuaro, C.P. 83170, Hermosillo, Sonora (Mexico); Nieto Jalil, J.M. [Tecnologico de Monterrey-Campus Sonora Norte, Bulevar Enrique Mazon Lopez No. 965, C.P. 83000, Hermosillo, Sonora (Mexico); Riera, R. [Departamento de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, C.P. 83190, Hermosillo, Sonora (Mexico)

    2013-02-01

    We have developed a theory of one phonon resonant Raman scattering in a semiconductor quantum wire of cylindrical geometry in the presence of an external magnetic field distribution, parallel to the cylinder axis. The effect of the magnetic field in the electron and hole states, and in the Raman scattering efficiency, is determinate. We consider the electron-phonon interaction using a Froehlich-type Hamiltonian, deduced for the case of complete confinement phonon modes by Comas and his collaborators. We also assume T=0 K, a single parabolic conduction and valence bands. The spectra are discussed for different magnetic field values and the selection rules for the processes are also studied.

  15. Quantum State Absorptions Coupled To Resonance Raman Spectroscopy Could Result In A General Explanation of TERS

    CERN Document Server

    Schultz, Zachary D; Dekhter, Rimma; Anestopoulos, Dimitris; Grammatikopoulos, Spyridon; Papagelis, Kostantinos; Marr, James M; Lewis, David; Galiotis, Costas; Lev, Dimtry; Lewis, Aaron

    2016-01-01

    Tip enhanced Raman scattering (TERS) amplifies the intensity of vibrational Raman scattering by employing the tip of a probe interacting, in ultra close proximity, with a surface. Although a general understanding of the TERS process is still to be fully elucidated, scanning tunneling microscopy (STM) feedback is often applied with success in TERS to keep a noble metal probe in intimate proximity with a noble metal substrate. Since such STM TERS is a common modality, the possible implications of plasmonic fields that may be induced by the tunneling process are investigated and reported. In addition, TERS of a 2D resonant molecular system, a MoS2 bilayer crystal and a 2D non-resonant, lipid molecular bilayer is compared. Data with multiple excitation wavelengths and surfaces for the resonant system in the near- (TERS) and far-field regimes are reported. An interpretation based on weak coupling interactions within the framework of conventional resonance Raman scattering can explain the observed TERS enhancements...

  16. Shifted excitation resonance Raman difference spectroscopy using a microsystem light source at 488 nm

    Science.gov (United States)

    Maiwald, M.; Sowoidnich, K.; Schmidt, H.; Sumpf, B.; Erbert, G.; Kronfeldt, H.-D.

    2010-04-01

    Experimental results in shifted excitation resonance Raman difference spectroscopy (SERRDS) at 488 nm will be presented. A novel compact diode laser system was used as excitation light source. The device is based on a distributed feedback (DFB) diode laser as a pump light source and a nonlinear frequency doubling using a periodically poled lithium niobate (PPLN) waveguide crystal. All elements including micro-optics are fixed on a micro-optical bench with a footprint of 25 mm × 5 mm. An easy temperature management of the DFB laser and the crystal was used for wavelength tuning. The second harmonic generation (SHG) provides an additional suppression of the spontaneous emission. Raman spectra of polystyrene demonstrate that no laser bandpass filter is needed for the Raman experiments. Resonance-Raman spectra of the restricted food colorant Tartrazine (FD&C Yellow 5, E 102) in distilled water excited at 488 nm demonstrate the suitability of this light source for SERRDS. A limit of detection (LOD) of 0.4 μmol.l-1 of E102 enables SERRDS at 488 nm for trace detection in e.g. food safety control as an appropriate contactless spectroscopic technique.

  17. Resonant Raman scattering theory for Kitaev models and their Majorana fermion boundary modes

    Science.gov (United States)

    Perreault, Brent; Knolle, Johannes; Perkins, Natalia B.; Burnell, F. J.

    2016-09-01

    We study the inelastic light scattering response in two- (2D) and three-dimensional (3D) Kitaev spin-liquid models with Majorana spinon band structures in the symmetry classes BDI and D leading to protected gapless surface modes. We present a detailed calculation of the resonant Raman/Brillouin scattering vertex relevant to iridate and ruthenate compounds whose low-energy physics is believed to be proximate to these spin-liquid phases. In the symmetry class BDI, we find that while the resonant scattering on thin films can detect the gapless boundary modes of spin liquids, the nonresonant processes do not couple to them. For the symmetry class D, however, we find that the coupling between both types of light-scattering processes and the low-energy surface states is strongly suppressed. Additionally, we describe the effect of weak time-reversal symmetry breaking perturbations on the bulk Raman response of these systems.

  18. Nonadiabaticity in a Jahn-Teller system probed by absorption and resonance Raman scattering.

    Science.gov (United States)

    Pae, K; Hizhnyakov, V

    2013-03-14

    A theory of absorption and resonance Raman scattering of impurity centers in crystals with E⊗e-type Jahn-Teller effect in the excited state is presented. The vibronic interaction with non-totally symmetric local or pseudolocal modes and with a continuum of bath modes (phonons) is considered. A number of specific quantum effects, such as the nonadiabaticity-induced enhancement of the Raman scattering at high-energy excitation, the size effect of the final state, the interference of different channels of scattering, the Fermi resonances in the conical intersection, and others, were shown to become apparent in the calculated spectra. The vibronic interaction with phonons essentially determines the structure of the spectra.

  19. Quantitative detection of astaxanthin and cantaxanthin in Atlantic salmon by resonance Raman spectroscopy

    Science.gov (United States)

    Ermakov, Igor V.; Ermakova, Maia R.; Gellermann, Werner

    2006-02-01

    Two major carotenoids species found in salmonids muscle tissues are astaxanthin and cantaxanthin. They are taken up from fish food and are responsible for the attractive red-orange color of salmon filet. Since carotenoids are powerful antioxidants and biomarkers of nutrient consumption, they are thought to indicate fish health and resistance to diseases in fish farm environments. Therefore, a rapid, accurate, quantitative optical technique for measuring carotenoid content in salmon tissues is of economic interest. We demonstrate the possibility of using fast, selective, quantitative detection of astaxanthin and cantaxanthin in salmon muscle tissues, employing resonance Raman spectroscopy. Analyzing strong Raman signals originating from the carbon-carbon double bond stretch vibrations of the carotenoid molecules under blue laser excitation, we are able to characterize quantitatively the concentrations of carotenoids in salmon muscle tissue. To validate the technique, we compared Raman data with absorption measurements of carotenoid extracts in acetone. A close correspondence was observed in absorption spectra for tissue extract in acetone and a pure astaxanthin solution. Raman results show a linear dependence between Raman and absorption data. The proposed technique holds promise as a method of rapid screening of carotenoid levels in fish muscle tissues and may be attractive for the fish farm industry to assess the dietary status of salmon, risk for infective diseases, and product quality control.

  20. Absolute determination of cross sections for resonant Raman scattering on silicon

    Science.gov (United States)

    Müller, Matthias; Beckhoff, Burkhard; Ulm, Gerhard; Kanngießer, Birgit

    2006-07-01

    We studied the resonant Raman scattering of x rays in the vicinity of the K absorption edge of silicon. The investigation was carried out at the plane grating monochromator beamline for undulator radiation of the PTB laboratory at BESSY II in Berlin. Cross sections were determined absolutely for a wide energy range of incident photons with small relative uncertainties employing calibrated instrumentation avoiding any reference samples. The experimentally determined values differ clearly from the theoretical ones found in the literature.

  1. Raman Theory for a Molecule in a Vibrating Microcavity Oscillating in Fundamental Resonance

    Institute of Scientific and Technical Information of China (English)

    YANG XiaoXue; WU Ying

    2001-01-01

    We propose a model to describe the energy structure and dynamics of a system of a molecule interacting with infinite photon modes in a vibrating microcavity whose boundary oscillates in the fundamental resonance. By constructing an so(2,1) Lie algebra for the infinite photon modes, we obtain analytical expressions of the energy eigenstates, energy eigenvalues and the system's evolution operator for this Raman model under certain conditions.``

  2. Anisotropy of electron-phonon interaction in nanoscale CdSe platelets as seen via off-resonant and resonant Raman spectroscopy

    Science.gov (United States)

    Cherevkov, S. A.; Fedorov, A. V.; Artemyev, M. V.; Prudnikau, A. V.; Baranov, A. V.

    2013-07-01

    The off-resonant and resonant Raman spectra of optical phonons in colloidal CdSe nanoplatelets (NPLs) with the thickness of 4, 5, and 6 CdSe monolayers are analyzed. These spectra are dominated by SO and LO phonon bands of CdSe whose frequencies are thickness independent in the off-resonant Raman but demonstrate evident thickness dependence similar to that observed for confined optical phonons in CdSe quantum dots in the resonant Raman. The results show that conventional optical phonons propagating along the NPL lateral planes contribute mainly to the off-resonant Raman while confined optical phonons propagating in the perpendicular direction dominate the Raman spectra excited in the resonance with confined exciton transitions of CdSe NPLs. An anisotropic electron-phonon interaction is proposed to be responsible for this effect in the CdSe NPLs. A formation of Cd-S monolayer on the surface of CdSe NPLs treated by thiol-containing ligands is also detected in Raman spectra.

  3. Electronic Raman scattering and the Fano resonance in metallic carbon nanotubes

    Science.gov (United States)

    Hasdeo, Eddwi H.; Nugraha, Ahmad R. T.; Sato, Kentaro; Dresselhaus, Mildred S.; Saito, Riichiro

    2013-09-01

    The Fano resonance spectra for the G band in metallic carbon nanotubes are calculated as a function of laser excitation energy, in which the origin of the resonance is given by an interference between the continuous electronic Raman spectra and the discrete phonon spectra. We found that the second-order scattering process of the q≠0 electron-electron interaction is more relevant to the continuous spectra rather than the q=0 first-order process because the q=0 direct Coulomb interaction vanishes due to the symmetry of the two sublattices of a carbon nanotube.

  4. Solitons and frequency combs in silica microring resonators: Interplay of the Raman and higher-order dispersion effects

    CERN Document Server

    Milián, Carles; Taki, Majid; Yulin, Alexey V; Skryabin, Dmitry V

    2015-01-01

    The influence of Raman scattering and higher order dispersions on solitons and frequency comb generation in silica microring resonators is investigated. The Raman effect introduces a threshold value in the resonator quality factor above which the frequency locked solitons can not exist and, instead, a rich dynamics characterized by generation of self-frequency shift- ing solitons and dispersive waves is observed. A mechanism of broadening of the Cherenkov radiation through Hopf instability of the frequency locked solitons is also reported.

  5. Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Junwei [Iowa State Univ., Ames, IA (United States)

    1999-11-08

    Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO2 were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO2, large photoelectrocatalytic effect for the reduction of CO2 was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO2 in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.

  6. Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Junwei

    1999-11-08

    Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO{sub 2} were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO{sub 2}, large photoelectrocatalytic effect for the reduction of CO{sub 2} was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO{sub 2} in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.

  7. Application of resonance Raman spectroscopy as a nuclear proliferation detection technology

    Energy Technology Data Exchange (ETDEWEB)

    Sedlacek, A.J. III; Chen, C.L.; Dougherty, D.R.

    1993-01-01

    Resonance Raman spectroscopy (RRS) potentially possesses many of the characteristics of an ideal verification technology. Some of these ideal traits are: very high selectivity and specificity to allow the deconvolution of a mixture of the chemicals of interest, high sensitivity in order to measure a species at trace levels, high reliability and long-term durability, applicability to a wide range of chemicals capability for sensing in a variety of environmental conditions, independence of the physical state of the chemical capability for quantitative analysis, and finally, but no less important capability for full signal development within seconds. In this presentation, the potential of RRS as a detection/identification technology for chemicals pertinent to nuclear materials production and processing will be assessed. A review of the basic principles behind this technique, both theoretical and experimental, will be discussed along with some recent results obtained in this laboratory. Raman scattering is a coherent, inelastic, two-photon scattering process where an exciting photon of energy hv promotes a molecule to a virtual level and the subsequently emitted photon is shifted in frequency in accordance with the rotational-vibrational structure of the irradiated species, therefore providing a unique fingerprint of the molecule. The enhancement of a Raman signal occurs when the excitation frequency is isoenergetic with an allowed electronic transition. Under resonance conditions, scattering cross-sections have been enhanced up to 6 orders of magnitude, thereby allowing the measurement of resonance Raman spectra from concentrations as dilute as 20 ppb for PAHs (with the potential of pptr). In detection/verification programs, this condition translates to increased sensitivity (ppm/ppb) and increased probing distance (m/km).

  8. Application of resonance Raman spectroscopy as a nuclear proliferation detection technology

    Energy Technology Data Exchange (ETDEWEB)

    Sedlacek, A.J. III; Chen, C.L.; Dougherty, D.R.

    1993-03-01

    Resonance Raman spectroscopy (RRS) potentially possesses many of the characteristics of an ideal verification technology. Some of these ideal traits are: very high selectivity and specificity to allow the deconvolution of a mixture of the chemicals of interest, high sensitivity in order to measure a species at trace levels, high reliability and long-term durability, applicability to a wide range of chemicals capability for sensing in a variety of environmental conditions, independence of the physical state of the chemical capability for quantitative analysis, and finally, but no less important capability for full signal development within seconds. In this presentation, the potential of RRS as a detection/identification technology for chemicals pertinent to nuclear materials production and processing will be assessed. A review of the basic principles behind this technique, both theoretical and experimental, will be discussed along with some recent results obtained in this laboratory. Raman scattering is a coherent, inelastic, two-photon scattering process where an exciting photon of energy hv promotes a molecule to a virtual level and the subsequently emitted photon is shifted in frequency in accordance with the rotational-vibrational structure of the irradiated species, therefore providing a unique fingerprint of the molecule. The enhancement of a Raman signal occurs when the excitation frequency is isoenergetic with an allowed electronic transition. Under resonance conditions, scattering cross-sections have been enhanced up to 6 orders of magnitude, thereby allowing the measurement of resonance Raman spectra from concentrations as dilute as 20 ppb for PAHs (with the potential of pptr). In detection/verification programs, this condition translates to increased sensitivity (ppm/ppb) and increased probing distance (m/km).

  9. Resonance Raman spectra of phthalocyanine monolayers on different supports. A normal mode analysis of zinc phthalocyanine by means of the MNDO method

    NARCIS (Netherlands)

    Palys, Barbara J.; Ham, van den Dirk M.W.; Briels, Wim; Feil, Dirk

    1995-01-01

    Resonance Raman spectra of monolayers of transition metal phthalocyanines reveal specific interaction with the support. To elucidate its mechanism, Raman spectra of zinc phthalocyanine monolayers were studied. The analysis was based largely on the results of MNDO calculations. Calculated wavenumbers

  10. UV resonance Raman investigation of the aqueous solvation dependence of primary amide vibrations.

    Science.gov (United States)

    Punihaole, David; Jakubek, Ryan S; Dahlburg, Elizabeth M; Hong, Zhenmin; Myshakina, Nataliya S; Geib, Steven; Asher, Sanford A

    2015-03-12

    We investigated the normal mode composition and the aqueous solvation dependence of the primary amide vibrations of propanamide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanamide. We examined the aqueous solvation dependence of the primary amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetamide, all of the resonance enhanced primary amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar (-)O-C═NH2(+) resonance structure over the neutral O═C-NH2 resonance structure. Thus, vibrations with large C-N stretching show increased UVRR cross sections because the C-N displacement between the electronic ground and excited state increases along the C-N bond. In contrast, vibrations dominated by C═O stretching, such as the AmI, show a decreased displacement between the electronic ground and excited state, which result in a decreased UVRR cross section upon aqueous solvation. The UVRR primary amide vibrations can be used as sensitive spectroscopic markers to study the local dielectric constant and hydrogen bonding environments of the primary amide side chains of glutamine (Gln) and asparagine (Asn).

  11. Analysis of structure-function relationships in cytochrome c oxidase and its biomimetic analogs via resonance Raman and surface enhanced resonance Raman spectroscopies.

    Science.gov (United States)

    Weidinger, Inez M

    2015-01-01

    Cytochrome c oxidase (CcO) catalyzes the four electron reduction of molecular oxygen to water while avoiding the formation of toxic peroxide; a quality that is of high relevance for the development of oxygen-reducing catalysts. Resonance Raman spectroscopy has been used since many years as a technique to identify electron transfer pathways in cytochrome c oxidase and to identify the key intermediates in the catalytic cycle. This information can be compared to artificial systems such as modified heme-copper enzymes, molecular heme-copper catalysts or CcO/electrode complexes in order to shed light into the reaction mechanism of these non-natural systems. Understanding the structural commonalities and differences of CcO with its non-natural analogs is of great value for designing efficient oxygen-reducing catalysts. In this review therefore Raman spectroscopic measurements on artificial heme-copper enzymes and model complexes are summarized and compared to the natural enzyme cytochrome c oxidase. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.

  12. Resonant-Raman Intensities of N-layer Transition Metal Dichalcogenides from First Principles

    Science.gov (United States)

    Miranda, Henrique; Froehlicher, Guillaume; Lorchat, Ettienne; Fernique, François; Molina-Sánchez, Alejandro; Berciaud, Stéphane; Wirtz, Ludger

    Transition metal dichalcogenides (TMDs) have interesting optical and electronic properties that make them good candidates for nano-engineering applications. Raman spectroscopy provides information about the vibrational modes and optical spectrum at the same time: when the laser energy is close to an electronic transition, the intensity is increased due to resonance. We investigate these effects combining different ab initio methods: we obtain ground-state and vibrational properties from density functional theory and the optical absorption spectrum using GW corrections and the Bethe-Salpeter equation to account for the excitonic effects which are known to play an important role in TMDs. Using a quasi-static finite differences approach, we calculate the dielectric susceptibility for different light polarizations and different phonon modes in order to determine the Raman tensor of TMDs, in particular of multi-layer and bulk MoTe2. We explain recent experimental results for the splitting of high-frequency modes and deviations from the non-resonant Raman model. We also give a brief outlook on possible improvements of the methodology.

  13. Resonant Raman detectors for noninvasive assessment of carotenoid antioxidants in human tissue

    Science.gov (United States)

    Gellermann, Werner; Sharifzadeh, Mohsen; Ermakova, Maia R.; Ermakov, Igor V.; Bernstein, P. S.

    2003-07-01

    Carotenoid antioxidants form an important part of the human body's anti-oxidant system and are thought to play an important role in disease prevention. Studies have shown an inverse correlation between high dietary intake of carotenoids and risk of certain cancers, heart disease and degenerative diseases. For example, the carotenoids lutein and zeaxanthin, which are present in high concentrations in the human retina, are thought to prevent age-related macular degeneration, the leading cause of blindness in the elderly in the Western world. We have developed various clinical prototype instruments, based on resonance Raman spectroscopy, that are able to measure carotenoid levels directly in the tissue of interest. At present we use the Raman technology to quantify carotenoid levels in the human retina, in skin, and in the oral cavity. We use resonant excitation of the π-conjugated molecules in the visible wavelength range and detect the molecules' carbon-carbon stretch frequencies. The spectral properties of the various carotenoids can be explored to selectively measure in some cases individual carotenoid species linked ot the prevention of cancer, in human skin. The instrumentation involves home-built, compact, high-throughput Raman systems capable of measuring physiological carotenoid concentrations in human subjects rapidly and quantitatively. The instruments have been demonstrated for field use and screening of tissue carotenoid status in large populations. In Epidemiology, the technology holds promise as a novel, noninvasive and objective biomarker of fruit and vegetable uptake.

  14. Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

    Institute of Scientific and Technical Information of China (English)

    Zhou Zeng-Hui; Liu Li; Wang Gui-Ying; Xu Zhi-Zhan

    2006-01-01

    Surface-enhanced resonance Raman scattering (SERRS) of Rhodamine 6G (R6G) adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even "breathing" of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.

  15. Resonance Raman and theoretical investigation of the photodissociation dynamics of benzamide in S3 state.

    Science.gov (United States)

    Pei, Ke-Mei; Ma, Yufang; Zheng, Xuming

    2008-06-14

    Resonance Raman spectra were obtained for benzamide in methanol and acetonitrile solutions with excitation wavelengths in resonance with the S(3) state. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with the motions mainly along the benzene ring C[Double Bond]C stretch nu(9), the Ph-CO-NH(2) and ring benzene stretch nu(14), the CCH in plane bend nu(17), the Ph-CO-NH(2) stretch and NH(2) rock nu(19), the ring trigonal bend nu(23), and the ring deformation and Ph-CO-NH(2) stretch nu(29). A preliminary resonance Raman intensity analysis was done, and the results were compared to those previously reported for acetophenone to examine the substituent effect. Solvent effect on the short-time photodissociation dynamics of benzamide was also examined. A conical intersection point S(2)S(3) between S(3) and S(2) potential energy surfaces of benzamide was determined by using a complete active space self-consistent field theory computations. The structural differences and similarities between S(3)S(2) point and S(0) were examined, and the results were used to correlate to the Franck-Condon photodissociation dynamics of benzamide in S(3) state.

  16. Al-doped MgB2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    Science.gov (United States)

    Bateni, Ali; Erdem, Emre; Repp, Sergej; Weber, Stefan; Somer, Mehmet

    2016-05-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB2. Above a certain level of Al doping, enhanced conductive properties of MgB2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  17. Resonance Raman study on distorted symmetry of porphyrin in nickel octaethyl porphyrin

    Indian Academy of Sciences (India)

    S Tewari; R Das; A Chakraborty; Ramendu Bhattacharjee

    2004-11-01

    The resonance Raman (RR) spectra of nickel octaethyl porphyrin, Ni(OEP), in CH2Cl2 (solvent) at different excitations such as 514.5, 488.0, 441.6 and 406.7 nm are recorded and analysed. The results of the theory of distortion-induced RR intensity is applied to the observed spectra to determine the excited electronic state symmetry of porphyrin in Ni(OEP). It is concluded that the porphyrin molecule (D4h structure) attains a non-polar distorted structure of D2 symmetry rather than S4 symmetry in CH2Cl2 solution.

  18. Measurements of vitamin B12 in human blood serum using resonance Raman spectroscopy

    Science.gov (United States)

    Tsiminis, G.; Schartner, E. P.; Brooks, J. L.; Hutchinson, M. R.

    2016-12-01

    Vitamin B12 (cobalamin and its derivatives) deficiency has been identified as a potential modifiable risk factor for dementia and Alzheimer's disease. Chronic deficiency of vitamin B12 has been significantly associated with an increased risk of cognitive decline. An effective and efficient method for measuring vitamin B12 concentration in human blood would enable ongoing tracking and assessment of this potential modifiable risk factor. In this work we present an optical sensor based on resonance Raman spectroscopy for rapid measurements of vitamin B12 in human blood serum. The measurement takes less than a minute and requires minimum preparation (centrifuging) of the collected blood samples.

  19. Resonant femtosecond stimulated Raman spectroscopy with an intense actinic pump pulse: Application to conical intersections

    Science.gov (United States)

    Rao, B. Jayachander; Gelin, Maxim F.; Domcke, Wolfgang

    2017-02-01

    We theoretically investigate the feasibility of characterizing conical intersections with time-resolved resonant femtosecond stimulated Raman spectroscopy (FSRS) using an intense actinic pump pulse. We perform nonperturbative numerical simulations of FSRS signals for a three-electronic-state two-vibrational-mode model, which is inspired by the S 2 ( π π * )- S 1 ( n π * ) conical intersection in pyrazine. Our results show that moderately strong actinic pulses increase the intensity of vibrational fingerprint lines in FSRS transients. They facilitate the extraction of useful spectroscopic information by enhancing peaks revealing the coupling and tuning modes of the conical intersection.

  20. Resonance Raman Spectrum of the Transient (SCN)2 Free Radical Anion

    DEFF Research Database (Denmark)

    Wilbrandt, Robert Walter; Jensen, N. H.; Pagsberg, Palle Bjørn

    1979-01-01

    The resonance Raman spectrum of the transient species (λmax = 475 nm, τ½ = 1.6 μs) formed by pulse radiolysis of aqueous solutions of thiocyanate, SCN2−, is reported. The spectrum is discussed in terms of the previous assignment of this transient to the radical anion, (SCN)−2. The observed...... vibrational frequencies of the radical anion are consistent with substantial weakening of the S---S and the Ctriple bond; length as m-dashN bonds are compared with neutral thiocyanogen....

  1. Excited state structures and decay dynamics of 1,3-dimethyluracils in solutions: resonance Raman and quantum mechanical calculation study.

    Science.gov (United States)

    Li, Ming-Juan; Liu, Ming-Xia; Zhao, Yan-Ying; Pei, Ke-Mei; Wang, Hui-Gang; Zheng, Xuming; Fang, Wei Hai

    2013-10-03

    The resonance Raman spectroscopic study of the excited state structural dynamics of 1,3-dimethyluracil (DMU), 5-bromo-1,3-dimethyluracil (5BrDMU), uracil, and thymine in water and acetonitrile were reported. Density functional theory calculations were carried out to help elucidate the ultraviolet electronic transitions associated with the A-, and B-band absorptions and the vibrational assignments of the resonance Raman spectra. The effect of the methylation at N1, N3 and C5 sites of pyrimidine ring on the structural dynamics of uracils in different solvents were explored on the basis of the resonance Raman intensity patterns. The relative resonance Raman intensities of DMU and 5BrDMU are computed at the B3LYP-TD level. Huge discrepancies between the experimental resonance Raman intensities and the B3LYP-TD predicted ones were observed. The underlying mechanism was briefly discussed. The decay channel through the S1((1)nπ*)/S2((1)ππ*) conical intersection and the S1((1)nπ*)/T1((3)ππ*) intersystem crossing were revealed by using the CASSCF(8,7)/6-31G(d) level of theory calculations.

  2. Investigating the phase-dependent photochemical reaction dynamics of chlorine dioxide using resonance Raman spectroscopy

    Science.gov (United States)

    Hayes, Sophia C.; Wallace, Paul M.; Bolinger, Josh C.; Reid, Philip J.

    Recent progress in understanding the phase-dependent reactivity demonstrated by halooxides is outlined. Specifically, resonance Raman intensity analysis (RRIA) and time-resolved resonance Raman (TRRR) studies of chlorine dioxide (OClO) photochemistry in solution are presented. Using RRIA, it has been determined that the excited-state structural evolution that occurs along the asymmetric-stretch coordinate in the gas phase is restricted in solution. The absence of evolution along this coordinate results in the preservation of groundstate symmetry in the excited state. The role of symmetry in defining the reaction coordinate and the solvent-solute interactions responsible for modification of the excited-state potential energy surface are discussed. TRRR studies are presented which demonstrate that geminate recombination of the primary photoproducts resulting in the reformation of ground-state OClO is a central feature of OClO photochemistry in solution. These studies also demonstrate that a fraction of photoexcited OClO undergoes photoisomerization to form ClOO, with the ground-state thermal decomposition of this species resulting in Cl production on the subnanosecond timescale. Finally, time-resolved anti-Stokes experiments are presented which demonstrate that the OClO vibrational-relaxation dynamics are solvent dependent. The current picture of OClO photochemistry derived from these studies is discussed, and future directions for study are outlined.

  3. Solvatochromism of 9,10-phenanthrenequinone: an electronic and resonance Raman spectroscopic study.

    Science.gov (United States)

    Ravi Kumar, Venkatraman; Rajkumar, Nagappan; Umapathy, Siva

    2015-01-14

    Solvent effects play a vital role in various chemical, physical, and biological processes. To gain a fundamental understanding of the solute-solvent interactions and their implications on the energy level re-ordering and structure, UV-VIS absorption, resonance Raman spectroscopic, and density functional theory calculation studies on 9,10-phenanthrenequinone (PQ) in different solvents of diverse solvent polarity has been carried out. The solvatochromic analysis of the absorption spectra of PQ in protic dipolar solvents suggests that the longest (1n-π(1)*; S1 state) and the shorter (1π-π(1)*; S2 state) wavelength band undergoes a hypsochromic and bathochromic shift due to intermolecular hydrogen bond weakening and strengthening, respectively. It also indicates that hydrogen bonding plays a major role in the differential solvation of the S2 state relative to the ground state. Raman excitation profiles of PQ (400-1800 cm(-1)) in various solvents followed their corresponding absorption spectra therefore the enhancements on resonant excitation are from single-state rather than mixed states. The hyperchromism of the longer wavelength band is attributed to intensity borrowing from the nearby allowed electronic transition through vibronic coupling. Computational calculation with C2ν symmetry constraint on the S2 state resulted in an imaginary frequency along the low-frequency out-of-plane torsional modes involving the C=O site and therefore, we hypothesize that this mode could be involved in the vibronic coupling.

  4. Resonance Raman study on indoleamine 2,3-dioxygenase: Control of reactivity by substrate-binding

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Sachiko; Hara, Masayuki [Graduate School of Life Science and Picobiology Institute, University of Hyogo, Koto 3-2-1, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Sugimoto, Hiroshi; Shiro, Yoshitsugu [Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Koto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Ogura, Takashi, E-mail: ogura@sci.u-hyogo.ac.jp [Graduate School of Life Science and Picobiology Institute, University of Hyogo, Koto 3-2-1, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

    2013-06-20

    Highlights: • Indoleamine 2,3-dioygenase has been studied by resonance Raman spectroscopy. • Trp-binding to the enzyme induces high frequency shift of the Fe–His stretching mode. • Increased imidazolate character of histidine promotes the O–O bond cleavage step. • A fine-tuning of the reactivity of the O–O bond cleavage reaction is identified. • The results are consistent with the sequential oxygen-atom-transfer mechanism. - Abstract: Resonance Raman spectra of ligand-bound complexes including the 4-phenylimidazole complex and of free and L-Trp-bound forms of indoleamine 2, 3-dioxygenase in the ferric state were examined. Effects on the vinyl and propionate substituent groups of the heme were detected in a ligand-dependent fashion. The effects of phenyl group of 4-phenylimidazole on the vinyl and propionate Raman bands were evident when compared with the case of imidazole ligand. Substrate binding to the ferrous protein caused an upshift of the iron–histidine stretching mode by 3 cm{sup −1}, indicating an increase in negativity of the imidazole ring, which favors the O–O bond cleavage. The substrate binding event is likely to be communicated from the heme distal side to the iron–histidine bond through heme substituent groups and the hydrogen-bond network which includes water molecules, as identified in an X-ray structure of a 4-phenylimidazole complex. The results provide evidence for fine-tuning of the reactivity of O–O bond cleavage by the oxygenated heme upon binding of L-Trp.

  5. Vibrational techniques applied to photosynthesis: Resonance Raman and fluorescence line-narrowing.

    Science.gov (United States)

    Gall, Andrew; Pascal, Andrew A; Robert, Bruno

    2015-01-01

    Resonance Raman spectroscopy may yield precise information on the conformation of, and the interactions assumed by, the chromophores involved in the first steps of the photosynthetic process. Selectivity is achieved via resonance with the absorption transition of the chromophore of interest. Fluorescence line-narrowing spectroscopy is a complementary technique, in that it provides the same level of information (structure, conformation, interactions), but in this case for the emitting pigment(s) only (whether isolated or in an ensemble of interacting chromophores). The selectivity provided by these vibrational techniques allows for the analysis of pigment molecules not only when they are isolated in solvents, but also when embedded in soluble or membrane proteins and even, as shown recently, in vivo. They can be used, for instance, to relate the electronic properties of these pigment molecules to their structure and/or the physical properties of their environment. These techniques are even able to follow subtle changes in chromophore conformation associated with regulatory processes. After a short introduction to the physical principles that govern resonance Raman and fluorescence line-narrowing spectroscopies, the information content of the vibrational spectra of chlorophyll and carotenoid molecules is described in this article, together with the experiments which helped in determining which structural parameter(s) each vibrational band is sensitive to. A selection of applications is then presented, in order to illustrate how these techniques have been used in the field of photosynthesis, and what type of information has been obtained. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.

  6. In situ monitoring of polymer redox states by resonance µRaman spectroscopy and its applications in polymer modified microfluidic channels

    NARCIS (Netherlands)

    Logtenberg, Hella; Jellema, Laurens-Jan C.; Lopez-Martinez, Maria J.; Areephong, Jetsuda; Verpoorte, Elisabeth; Feringa, Ben L.; Browne, Wesley R.

    2012-01-01

    We report the application of multi-wavelength resonance Raman (rR) spectroscopy for the characterisation of vinyl-bridged polysexithiophene films formed by electropolymerisation on gold electrodes. Resonance Raman spectroscopy of the neutral, polaronic and bipolaronic states of the polymer were dete

  7. Molecular structure and vibrational spectra of spin-crossover complexes in solution and colloidal media: resonance Raman and time-resolved resonance Raman studies.

    Science.gov (United States)

    Brady, Clare; Callaghan, Philip L; Ciunik, Zbigniew; Coates, Colin G; Døssing, Anders; Hazell, Alan; McGarvey, John J; Schenker, Sabine; Toftlund, Hans; Trautwein, Alfred X; Winkler, Heiner; Wolny, Juliusz A

    2004-07-12

    The spin-crossover system [Fe(btpa)](PF(6))(2) (btpa = N,N,N',N'-tetrakis(2-pyridylmethyl)-6,6'-bis(aminomethyl)-2,2'-bipyridine) and the predominantly low-spin species [Fe(b(bdpa))](PF(6))(2) ((b(bdpa) = N,N'-bis(benzyl)-N,N'-bis(2-pyridylmethyl)-6,6'-bis(aminomethyl)-2,2'-bipyridine) have been characterized by means of X-ray diffraction. The unit cell of [Fe(btpa)](PF(6))(2) contains two crystallographically independent molecules revealing octahedral low-spin and quasi-seven-coordinated high-spin structures. The unit cell of [Fe(b(bdpa))](PF(6))(2) contains two crystallographically independent molecules one of which corresponds to a low-spin structure, while the other reveals a disordering. On the basis of magnetic susceptibility and Mössbauer measurements, it has been proposed that this disorder involves low-spin and high-spin six-coordinated molecules. The structures of [Zn(btpa)](PF(6))(2) and [Ru(btpa)](PF(6))(2) have been determined also. Pulsed laser photoperturbation, coupled here with time-resolved resonance Raman spectroscopy (TR(3)), has been used to investigate, for the first time by this technique, the relaxation dynamics in solution on nanosecond and picosecond time scales of low-spin, LS ((1)A) --> high-spin, HS ((5)T) electronic spin-state crossover in these Fe(II) complexes. For the nanosecond experiments, use of a probe wavelength at 321 nm, falling within the pi-pi transition of the polypyridyl backbone of the ligands, enabled the investigation of vibrational modes of both LS and HS isomers, through coupling to spin-state-dependent angle changes of the backbone. Supplementary investigations of the spin-crossover (SCO) equilibrium in homogeneous solution and in colloidal media assisted the assignment of prominent features in the Raman spectra of the LS and HS isomers. The relaxation data from the nanosecond studies confirm and extend earlier spectrophotometric findings, (Schenker, S.; Stein, P. C.; Wolny, J. A.; Brady, C.; McGarvey, J. J

  8. Gold split-ring resonators (SRRs) as substrates for surface-enhanced raman scattering

    KAUST Repository

    Yue, Weisheng

    2013-10-24

    We used gold split ring resonators (SRRs) as substrates for surface-enhanced Raman scattering (SERS). The arrays of SRRs were fabricated by electron-beam lithography in combination with plasma etching. In the detection of rhodamine 6G (R6G) molecules, SERS enhancement factors of the order of 105 was achieved. This SERS enhancement increased as the size of the split gap decrease as a consequence of the matching between the resonance wavelength of the SRRs and the excitation wavelength of SERS. As the size of the split gap decreased, the localized surface plasmon resonance shifted to near the excitation wavelength and, thus, resulted in the increase in the electric field on the nanostructures. We used finite integration method (FIT) to simulate numerically the electromagnetic properties of the SRRs. The results of the simulation agreed well with our experimental observations. We anticipate this work will provide an approach to manipulate the SERS enhancement by modulating the size of split gap with SRRs without affecting the area and structural arrangement. © 2013 American Chemical Society.

  9. Stimulated Raman spectroscopy and nanoscopy of molecules using near field photon induced forces without resonant electronic enhancement gain

    Science.gov (United States)

    Tamma, Venkata Ananth; Huang, Fei; Nowak, Derek; Kumar Wickramasinghe, H.

    2016-06-01

    We report on stimulated Raman spectroscopy and nanoscopy of molecules, excited without resonant electronic enhancement gain, and recorded using near field photon induced forces. Photon-induced interaction forces between the sharp metal coated silicon tip of an Atomic Force Microscope (AFM) and a sample resulting from stimulated Raman excitation were detected. We controlled the tip to sample spacing using the higher order flexural eigenmodes of the AFM cantilever, enabling the tip to come very close to the sample. As a result, the detection sensitivity was increased compared with previous work on Raman force microscopy. Raman vibrational spectra of azobenzene thiol and l-phenylalanine were measured and found to agree well with published results. Near-field force detection eliminates the need for far-field optical spectrometer detection. Recorded images show spatial resolution far below the optical diffraction limit. Further optimization and use of ultrafast pulsed lasers could push the detection sensitivity towards the single molecule limit.

  10. In Vitro Polarized Resonance Raman Study of N719 and N719-TBP in Dye Sensitized Solar Cells

    DEFF Research Database (Denmark)

    Hassig, Søren; Jernshøj, Kit; Phuong, Nguyen Tuyet;

    2016-01-01

    The working efficiency of dye-sensitized solar cells (DSCs) depends on the long-term stability of the dye itself and on the microscopic structure of the dye-semiconductor interface. Previous experimental studies of DSCs based on ruthenium dye with bipyridine ligands (N719) adsorbed to the TiO2......substrate applied FTIR,un-polarized Raman (RS) and un-polarized resonance Raman (RRS) spectroscopy. In the un-polarized RRS studies of N719/TiO2 – DSCs the discussion of the adsorption of N719 was based on the rather weak carbonyl or carboxyl group stretching vibrations and on minor spectral changes...... of overlapping Raman modes, whereas conclusions about the dye-stability was based on the observation that fresh and aged DSCs had almost identical RRS spectra. In the present paper we address the problems mentioned above, by utilizing the unique property of Raman scattering that the polarization of the scattered...

  11. Identification of metalloporphyrins with high sensitivity using graphene-enhanced resonance Raman scattering.

    Science.gov (United States)

    Kim, Bo-Hyun; Kim, Daechul; Song, Sungho; Park, DongHyuk; Kang, Il-Suk; Jeong, Dae Hong; Jeon, Seokwoo

    2014-03-18

    Graphene-enhanced resonance Raman scattering (GERRS) was performed for the detection of three different metallo-octaethylporphyrins (M-OEPs; M = 2H, FeCl, and Pt) homogeneously thermal vapor deposited on a graphene surface. GERRS of M-OEPs were measured using three different excitation wavelengths, λ(ex) = 405, 532, and 633 nm, and characterized detail vibrational bands for the identification of M-OEPs. The GERRS spectra of Pt-OEP at λ(ex) = 532 nm showed ~29 and ~162 times signal enhancement ratio on graphene and on graphene with Ag nanoclusters, respectively, compared to the spectra from bare SiO2 substrate. This enhancement ratio, however, was varied with M-OEPs and excitation wavelengths. The characteristic peaks and band shapes of GERRS for each M-OEP were measured with high sensitivity (100 pmol of thermal vapor deposited Pt-OEP), and these facilitate the selectively recognition of molecules. Also, the peaks shift and broadening provide the evidence of the interaction between graphene and M-OEPs through the charge transfer and π-orbital interaction. The increase of graphene layer induced the decrease of signal intensity and GERRS effect was almost not observed on the thick graphite flakes. Further experiments with various substrates demonstrated that the interaction of single layer of graphene with molecule is the origin of the Raman signal enhancement of M-OEPs. In this experiment, we proved the graphene is a good alternative substrate of Raman spectroscopy for the selective detection of various metalloporphyrins with high sensitivity.

  12. Low skin carotenoid concentration measured by resonance Raman spectroscopy is associated with metabolic syndrome in adults.

    Science.gov (United States)

    Holt, Edward W; Wei, Esther K; Bennett, Nancy; Zhang, Laura M

    2014-10-01

    Oxidative stress is increased in patients with metabolic syndrome (MS). Antioxidants, including carotenoids, are decreased in MS. We hypothesized that a low skin carotenoid score (SCS), calculated using resonance Raman spectroscopy, would correlate with the presence of MS. We retrospectively reviewed consecutive patients referred for dietary assessment between 2010 and 2012. For each patient, a nutrition history, medical history, and SCS were recorded. χ(2) and Student t test were used to determine factors associated with MS. Multivariate logistic regression was used to identify factors associated with MS. One hundred fifty-five patients were included. The mean age was 54.1 ± 13.1 years, and the mean body mass index was 28.3 ± 6.1 kg/m(2). Metabolic syndrome was present in 43.9% of patients. The mean SCS was 28 084 ± 14 006 Raman counts (RC), including 23 058 ± 9812 RC for patients with MS and 32 011 ± 15 514 RC for patients without MS (P = .0001). In a multivariate analysis, SCS less than 25 000 RC (odds ratio, 3.71; 95% confidence interval, 1.36-10.7; P = .01) was independently associated with MS. A higher number of MS components was associated with a progressively lower SCS (P = .004). In a consecutive sample of patients referred for dietary assessment, a noninvasively measured SCS was lower among patients with MS.

  13. Distinguishing Unfolding and Functional Conformational Transitions of Calmodulin Using Ultraviolet Resonance Raman Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Eric M.; Balakrishnan, G.; Squier, Thomas C.; Spiro, Thomas

    2014-06-14

    Calmodulin (CaM) is a ubiquitous moderator protein for calcium signaling in all eukaryotic cells. This small calcium-binding protein exhibits a broad range of structural transitions, including domain opening and folding-unfolding, that allow it to recognize a wide variety of binding partners in vivo. While the static structures of CaM associated with its various binding activities are fairly well known, it has been challenging to examine the dynamics of transition between these structures in real-time, due to a lack of suitable spectroscopic probes of CaM structure. In this paper, we examine the potential of ultraviolet resonance Raman (UVRR) spectroscopy for clarifying the nature of structural transitions in CaM. We find that the UVRR spectral change (with 229 nm excitation) due to thermal unfolding of CaM is qualitatively different from that associated with opening of the C-terminal domain in response to Ca2+ binding. This spectral difference is entirely due to differences in teritary contacts at the inter-domain tyrosine residue Tyr138, toward which other spectroscopic methods are not sensitive. We conclude that UVRR is ideally suited to identifying the different types of structural transitions in CaM and other proteins with conformation-sensitive tyrosine residues, opening a path to time-resolved studies of CaM dynamics using Raman spectroscopy.

  14. Optical pathology study of human abdominal aorta tissues using confocal micro resonance Raman spectroscopy

    Science.gov (United States)

    Liu, Cheng-hui; Boydston-White, Susie; Wang, Wubao; Sordillo, Laura A.; Shi, Lingyan; Weisberg, Arel; Tomaselli, Vincent P.; Sordillo, Peter P.; Alfano, Robert R.

    2016-03-01

    Resonance Raman (RR) spectroscopic technique has a high potential for label-free and in-situ detection of biomedical lesions in vivo. This study evaluates the ability of RR spectroscopy method as an optical histopathology tool to detect the atherosclerotic plaque states of abdominal aorta in vitro. This part demonstrates the RR spectral molecular fingerprint features from different sites of the atherosclerotic abdominal aortic wall tissues. Total 57 sites of five pieces aortic samples in intimal and adventitial wall from an autopsy specimen were examined using confocal micro Raman system of WITec 300R with excitation wavelength of 532nm. The preliminary RR spectral biomarkers of molecular fingerprints indicated that typical calcified atherosclerotic plaque (RR peak at 964cm-1) tissue; fibrolipid plaque (RR peaks at 1007, 1161, 1517 and 2888cm-1) tissue, lipid pool with the fatty precipitation cholesterol) with collagen type I (RR peaks at 864, 1452, 1658, 2888 and 2948cm-1) in the soft tissue were observed and investigated.

  15. In situ resonant Raman scattering and reversible photoinduced structural change in YBa2Cu3O6+x

    DEFF Research Database (Denmark)

    Osada, M.; Käll, M.; Bäckström, J.;

    2005-01-01

    or absence of a specific Raman scattering resonance. A comparison of the spectral efficiencies for this photoswitching with analogous data for the persistent photoconductivity and photoconductivity quenching effects suggests that the two phenomena have the same microscopic origin. We argue that the effects...

  16. Potential energy surfaces of short polyenes in the state T1 : analysis of time resolved resonance Raman spectra

    NARCIS (Netherlands)

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

    1993-01-01

    The analysis of T1 resonance Raman spectra of some conjugated compounds is discussed making use of semiempirical quantum chemical calculations. Information obtained about T1 potential energy curve indicates that in short polyenes the perpendicular form is roughly degenerate with the trans isomer. Pr

  17. Surface-Enhanced Resonance Raman Scattering and Visible Extinction Spectroscopy of Copper Chlorophyllin: An Upper Level Chemistry Experiment

    Science.gov (United States)

    Schnitzer, Cheryl S.; Reim, Candace Lawson; Sirois, John J.; House, Paul G.

    2010-01-01

    Advanced chemistry students are introduced to surface-enhanced resonance Raman scattering (SERRS) by studying how sodium copper chlorophyllin (CuChl) adsorbs onto silver colloids (CuChl/Ag) as a function of pH. Using both SERRS and visible extinction spectroscopy, the extent of CuChl adsorption and colloidal aggregation are monitored. Initially at…

  18. 13C Solid State Nuclear Magnetic Resonance and µ-Raman Spectroscopic Characterization of Sicilian Amber.

    Science.gov (United States)

    Barone, Germana; Capitani, Donatella; Mazzoleni, Paolo; Proietti, Noemi; Raneri, Simona; Longobardo, Ugo; Di Tullio, Valeria

    2016-08-01

    (13)C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) and µ-Raman spectroscopy were applied to characterize Sicilian amber samples. The main goal of this work was to supply a complete study of simetite, highlighting discriminating criteria useful to distinguish Sicilian amber from fossil resins from other regions and laying the foundations for building a spectroscopic database of Sicilian amber. With this aim, a private collection of unrefined simetite samples and fossil resins from the Baltic region and Dominican Republic was analyzed. Overall, the obtained spectra permitted simetite to be distinguished from the other resins. In addition, principal component analysis (PCA) was applied to the spectroscopic data, allowing the clustering of simetite samples with respect to the Baltic and Dominican samples and to group the simetite samples in two sets, depending on their maturity. Finally, the analysis of loadings allowed for a better understanding of the spectral features that mainly influenced the discriminating characteristics of the investigated ambers.

  19. Operational electrochemical stability of thiophene-thiazole copolymers probed by resonant Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wade, Jessica; Wood, Sebastian; Kim, Ji-Seon, E-mail: ji-seon.kim@imperial.ac.uk [Department of Physics and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ (United Kingdom); Beatrup, Daniel; Hurhangee, Michael; McCulloch, Iain; Durrant, James R. [Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AY (United Kingdom); Bronstein, Hugo [Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AY (United Kingdom); Department of Chemistry, University College London, London WC1H 0AJ (United Kingdom)

    2015-06-28

    We report on the electrochemical stability of hole polarons in three conjugated polymers probed by resonant Raman spectroscopy. The materials considered are all isostructural to poly(3-hexyl)thiophene, where thiazole units have been included to systematically deepen the energy level of the highest occupied molecular orbital (HOMO). We demonstrate that increasing the thiazole content planarizes the main conjugated backbone of the polymer and improves the electrochemical stability in the ground state. However, these more planar thiazole containing polymers are increasingly susceptible to electrochemical degradation in the polaronic excited state. We identify the degradation mechanism, which targets the C=N bond in the thiazole units and results in disruption of the main polymer backbone conjugation. The introduction of thiazole units to deepen the HOMO energy level and increase the conjugated backbone planarity can be beneficial for the performance of certain optoelectronic devices, but the reduced electrochemical stability of the hole polaron may compromise their operational stability.

  20. Resonance Raman and quantum chemical studies of short polyene radical cations

    DEFF Research Database (Denmark)

    Keszthelyi, T.; Wilbrandt, R.; Bally, T.

    1997-01-01

    The results of our investigations of the geometric and vibrational structures of some short conjugated polyene radical cations are reported. The radical cations of 1,3-butadiene and three of its deuterated isotopomers, trans- and cis-1,3-pentadiene, 2-methyl-1,3-butadiene, and E- and Z-1,3,5-hexa......The results of our investigations of the geometric and vibrational structures of some short conjugated polyene radical cations are reported. The radical cations of 1,3-butadiene and three of its deuterated isotopomers, trans- and cis-1,3-pentadiene, 2-methyl-1,3-butadiene, and E- and Z-1...... and to assist assignment of the resonance Raman spectra. A new and improved scaled quantum mechanical force field for the butadiene radical cation was also determined. The presence of more than one rotamer was observed in all the polyene radical cations we investigated. (C) 1997 Elsevier Science B.V....

  1. Harmonic-seeded resonant Raman amplification in strong-field ionized nitrogen molecules

    CERN Document Server

    Yao, Jinping; Tian, Chuanshan; Li, Ziting; Wang, Zhanshan; Cheng, Ya

    2016-01-01

    Generation of free-space laser-like emissions of high spatiotemporal coherence and narrow bandwidth in atmosphere opens promising opportunities for remote spectroscopic sensing. Here, we report on generation of such laser-like emissions, which results from the combined contributions of perturbative and non-perturbative nonlinear optical effects in nitrogen molecules exposed to intense mid-infrared laser fields. We systematically investigate the dependence of the generated free-space laser spectrum on wavelength and power of the driver laser. It is revealed that the free-space laser is produced by resonant Raman amplification of the fifth harmonic of the driver pulses in rotational wavepacket of the molecular nitrogen ions.

  2. Time Dependent Coupled Cluster Approach to Resonance Raman Excitation Profiles from General Anharmonic Surfaces

    Directory of Open Access Journals (Sweden)

    M. Durga Prasad

    2002-05-01

    Full Text Available Abstract: A time dependent coupled cluster approach to the calculation of Resonance Raman excitation profiles on general anharmonic surfaces is presented. The vibrational wave functions on the ground electronic surface are obtained by the coupled cluster method (CCM. It is shown that the propagation of the vibrational ground state on the upper surface is equivalent to propagation of the vacuum state by an effective hamiltonian generated by the similarity transformation of the vibrational hamiltonian of that surface by the CCM wave operator of the lower surface up to a normalization constant. This time propagation is carried out by the time-dependent coupled cluster method in a time dependent frame. Numerical studies are presented to asses the validity of the approach.

  3. "Parallel factor analysis of multi-excitation ultraviolet resonance Raman spectra for protein secondary structure determination".

    Science.gov (United States)

    Oshokoya, Olayinka O; JiJi, Renee D

    2015-09-10

    Protein secondary structural analysis is important for understanding the relationship between protein structure and function, or more importantly how changes in structure relate to loss of function. The structurally sensitive protein vibrational modes (amide I, II, III and S) in deep-ultraviolet resonance Raman (DUVRR) spectra resulting from the backbone C-O and N-H vibrations make DUVRR a potentially powerful tool for studying secondary structure changes. Experimental studies reveal that the position and intensity of the four amide modes in DUVRR spectra of proteins are largely correlated with the varying fractions of α-helix, β-sheet and disordered structural content of proteins. Employing multivariate calibration methods and DUVRR spectra of globular proteins with varying structural compositions, the secondary structure of a protein with unknown structure can be predicted. A disadvantage of multivariate calibration methods is the requirement of known concentration or spectral profiles. Second-order curve resolution methods, such as parallel factor analysis (PARAFAC), do not have such a requirement due to the "second-order advantage." An exceptional feature of DUVRR spectroscopy is that DUVRR spectra are linearly dependent on both excitation wavelength and secondary structure composition. Thus, higher order data can be created by combining protein DUVRR spectra of several proteins collected at multiple excitation wavelengths to give multi-excitation ultraviolet resonance Raman data (ME-UVRR). PARAFAC has been used to analyze ME-UVRR data of nine proteins to resolve the pure spectral, excitation and compositional profiles. A three factor model with non-negativity constraints produced three unique factors that were correlated with the relative abundance of helical, β-sheet and poly-proline II dihedral angles. This is the first empirical evidence that the typically resolved "disordered" spectrum represents the better defined poly-proline II type structure.

  4. Solvatochromism of 9,10-phenanthrenequinone: An electronic and resonance Raman spectroscopic study

    Energy Technology Data Exchange (ETDEWEB)

    Ravi Kumar, Venkatraman; Rajkumar, Nagappan; Umapathy, Siva, E-mail: umapathy@ipc.iisc.ernet.in

    2015-01-14

    Solvent effects play a vital role in various chemical, physical, and biological processes. To gain a fundamental understanding of the solute-solvent interactions and their implications on the energy level re-ordering and structure, UV-VIS absorption, resonance Raman spectroscopic, and density functional theory calculation studies on 9,10-phenanthrenequinone (PQ) in different solvents of diverse solvent polarity has been carried out. The solvatochromic analysis of the absorption spectra of PQ in protic dipolar solvents suggests that the longest (1n-π{sup 1}*; S{sub 1} state) and the shorter (1π-π{sup 1}*; S{sub 2} state) wavelength band undergoes a hypsochromic and bathochromic shift due to intermolecular hydrogen bond weakening and strengthening, respectively. It also indicates that hydrogen bonding plays a major role in the differential solvation of the S{sub 2} state relative to the ground state. Raman excitation profiles of PQ (400–1800 cm{sup −1}) in various solvents followed their corresponding absorption spectra therefore the enhancements on resonant excitation are from single-state rather than mixed states. The hyperchromism of the longer wavelength band is attributed to intensity borrowing from the nearby allowed electronic transition through vibronic coupling. Computational calculation with C{sub 2ν} symmetry constraint on the S{sub 2} state resulted in an imaginary frequency along the low-frequency out-of-plane torsional modes involving the C=O site and therefore, we hypothesize that this mode could be involved in the vibronic coupling.

  5. Resonance raman spectroscopic study of alumina-supported vanadium oxide catalysts with 220 and 287 nm excitation.

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H. S.; Stair, P. C.; Chemical Sciences and Engineering Division; Northwestern Univ.

    2009-01-01

    We present detailed resonance Raman spectroscopic results excited at 220 and 287 nm for alumina-supported VO{sub x} catalysts. The anharmonic constant, harmonic wavenumber, anharmonic force constant, bond dissociation energy, and bond length change in the excited state for double bonded V{double_bond}O and single bonded V-O were obtained from fundamental and overtone frequencies. Totally symmetric and nontotally symmetric modes could be discerned and assigned on the basis of the overtone and combination progressions found in the resonance Raman spectra. Selective resonance enhancement of two different vibrational modes with two different excitation wavelengths was observed. This allowed us to establish a linear relationship between charge transfer energy and VO bond length and, consequently, to assign the higher-energy charge transfer band centered around 210?250 nm in the UV?vis spectra to the V{double_bond}O transition.

  6. Resonance Raman mapping as a tool to monitor and manipulate Si nanocrystals in Si-SiO{sub 2} nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Ekta; Ingale, Alka A., E-mail: alka@rrcat.gov.in [Laser Physics Applications Section, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Homi Bhabha National Institute, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Chaturvedi, A. [Laser Material Processing Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Joshi, M. P.; Kukreja, L. M. [Homi Bhabha National Institute, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Laser Material Processing Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India)

    2015-10-19

    Specially designed laser heating experiment along with Raman mapping on Si-SiO{sub 2} nanocomposites elucidates the contribution of core and surface/interface in the intermediate frequency range (511–514 cm{sup −1}) Si phonons. The contribution of core to surface/interface increases with the size of Si nanocrystal, which itself increases on laser irradiation. Further, it is found that resonance Raman is crucial to the observance of surface/interface phonons and wavelength dependent Raman mapping can be corroborated with band edges observed in absorption spectra. This understanding can be gainfully used to manipulate and characterize Si-SiO{sub 2} nanocomposite, simultaneously for photovoltaic device applications.

  7. A magnetic-field enriched surface-enhanced resonance Raman spectroscopy strategy towards the early diagnosis of malaria

    Science.gov (United States)

    Yuen, Clement; Liu, Quan

    2012-03-01

    Early malaria diagnosis is important because malaria disease can develop into fatal illness within hours upon the appearance of the first symptom. The low concentration of the diagnosis biomarker, hemozoin, at the early stage of malaria disease makes early diagnosis difficult. In this paper, we present a magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) strategy for the sensitive detection of β - hematin crystals, which is equivalent to hemozoin in the characteristics of Raman spectrum, by using magnetic nanoparticles. We observe several orders of magnitude enhancement in the SERRS signal of enriched β - hematin in comparison to the Raman signal of β - hematin in the cases of SERRS alone or magnetic enrichment alone, showing the great potential of this method towards early malaria diagnosis.

  8. FTIR difference and resonance Raman spectroscopy of rhodopsins with applications to optogenetics

    Science.gov (United States)

    Saint Clair, Erica C.

    The major aim of this thesis is to investigate the molecular basis for the function of several types of rhodopsins with special emphasis on their application to the new field of optogenetics. Rhodopsins are transmembrane biophotonic proteins with 7 alpha-helices and a retinal chromophore. Studies included Archaerhodopsin 3 (AR3), a light driven proton pump similar to the extensively studied bacteriorhodopsin (BR); channelrhodopsins 1 and 2, light-activated ion channels; sensory rhodopsin II (SRII), a light-sensing protein that modulates phototaxis used in archaebacteria; and squid rhodopsins (sRho), the major photopigment in squid vision and a model for human melanopsin, which controls circadian rhythms. The primary techniques used in these studies were FTIR difference spectroscopy and resonance Raman spectroscopy. These techniques, in combination with site directed mutagenesis and other biochemical methodologies produced new knowledge regarding the structural changes of the retinal chromophore, the location and function of internal water molecules as well as specific amino acids and peptide backbone. Specialized techniques were developed that allowed rhodopsins to be studied in intact membrane environments and in some cases in vivo measurements were made on rhodopsin heterologously expressed in E. coli thus allowing the effects of interacting proteins and membrane potential to be investigated. Evidence was found that the local environment of one or more internal water molecules in SRII is altered by interaction with its cognate transducer, HtrII, and is also affected by the local lipid environment. In the case of AR3, many of the broad IR continuum absorption changes below 3000 cm -1, assigned to networks of water molecules involved in proton transport through cytoplasmic and extracellular portions in BR, were found to be very similar to BR. Bands assigned to water molecules near the Schiff base postulated to be involved in proton transport were, however, shifted

  9. Elucidating photoinduced structural changes in phytochromes by the combined application of resonance Raman spectroscopy and theoretical methods

    Science.gov (United States)

    Mroginski, M. A.; von Stetten, D.; Kaminski, S.; Escobar, F. Velazquez; Michael, N.; Daminelli-Widany, G.; Hildebrandt, P.

    2011-05-01

    Phytochromes constitute a family of red-light sensing photoreceptors in plants and microorganisms. The photoactive cofactor is an open-chain methine-bridged tetrapyrrole that, upon light absorption, undergoes a double bond isomerisation followed by series thermal relaxation processes which eventually lead to the functional structural change of the protein. Resonance Raman spectroscopy has contributed significantly to the understanding of the molecular functioning of these proteins although both the experiments and the interpretation of the spectra represent a considerable challenge. This account is dedicated to describe achievements, potential and limitations of combined resonance Raman spectroscopic and theoretical approaches for elucidating cofactor structures in phytochromes. Experimental approaches are discussed paying specific attention on strategies to overcome unwanted photochemical and photophysical processes when probing the various states of the photoinduced reaction cycle of phytochromes. The most comprehensive set of experimental data on phytochromes, including engineered protein variants and adducts formed with isotopically labelled tetrapyrroles, has been obtained by resonance Raman spectroscopy with near-infrared excitation that also allows probing phytochrome crystals without photo-induced destruction. Quantum mechanical calculations of Raman spectra of model compounds represent a first approximation for determining the methine bridge geometry of the protein-bound tetrapyrroles and constitute the basis for the identification of marker bands for specific structural properties such as the protonation state of the cofactor. Drawbacks of this theoretical method that inevitably neglects the protein environment have become evident with the first determinations of three-dimensional structures of phytochromes. These structural models can now be used for employing hybrid methods that combine quantum mechanical and molecular mechanics calculations of the

  10. Resonance Raman imaging as a tool to assess the atmospheric pollution level: carotenoids in Lecanoraceae lichens as bioindicators.

    Science.gov (United States)

    Ibarrondo, I; Prieto-Taboada, N; Martínez-Arkarazo, I; Madariaga, J M

    2016-04-01

    Raman spectroscopy differentiation of carotenoids has traditionally been based on the ν 1 position (C = C stretching vibrations in the polyene chain) in the 1500-1600 cm(-1) range, using a 785 nm excitation laser. However, when the number of conjugated double bonds is similar, as in the cases of zeaxanthin and β-carotene, this distinction is still ambiguous due to the closeness of the Raman bands. This work shows the Raman results, obtained in resonance conditions using a 514 mm laser, on Lecanora campestris and Lecanora atra species, which can be used to differentiate and consequently characterize carotenoids. The presence of the carotenoid found in Lecanoraceae lichens has been demonstrated to depend on the atmospheric pollution level of the environment they inhabit. Astaxanthin, a superb antioxidant, appears as the principal xanthophyll in highly polluted sites, usually together with the UV screening pigment scytonemin; zeaxanthin is the major carotenoid in medium polluted environments, while β-carotene is the major carotenoid in cleaner environments. Based on these observations, an indirect classification of the stress suffered in a given environment can be assessed by simply analysing the carotenoid content in the Lecanoraceae lichens by using resonance Raman imaging.

  11. Resonance Raman Spectra of o-Safranin Dye, Free and Adsorbed on Silver Nanoparticles: Experiment and Density Functional Theory Calculation.

    Science.gov (United States)

    Ricci, Marilena; Platania, Elena; Lofrumento, Cristiana; Castellucci, Emilio M; Becucci, Maurizio

    2016-07-14

    The properties of o-Safranin (SO) dye in the first electronic excited state were studied with combined experimental and theoretical methods. The electronic absorption spectra of SO molecules are measured in water solution and in the presence of silver nanoparticles. The normal Raman (NRS) and resonance Raman (RR) spectra of solid SO and the surface enhanced Raman (SERS) and surface enhanced resonance Raman (SE[R]RS) spectra of SO adsorbed on silver nanoparticles are measured at different excitation energies. The enhancement factors for selected vibrational bands of the RR, SERS, and SE[R]RS spectra of SO have been obtained with respect to the NRS spectra of the solid after a careful evaluation of the experimental conditions. The data furnished useful information on the excited electronic states and the interactions of SO with silver nanoparticles. The experimental results are discussed on the basis of DFT and TD-DFT calculations (B3LYP/6-311+G(d,p)) on the isolated SO molecule.

  12. A polyene chain of canthaxanthin investigated by temperature-dependent resonance Raman spectra and density functional theory (DFT) calculations

    Institute of Scientific and Technical Information of China (English)

    Chen Yuan-Zheng; Li Shuo; Zhou Mi; Li Zuo-Wei; Sun Cheng-Lin

    2013-01-01

    We report on a temperature-dependent resonance Raman spectral characterization of the polyene chain of canthaxanthin.It is observed that all vibrational intensities of the polyene chain are inversely proportional to temperature,which is analyzed by the resonance Raman effect and the coherent weakly damped electron/lattice vibrations.The increase in intensity of the CC overtone/combination relative to the fundamental with temperature decreasing is detected and discussed in terms of electron/phonon coupling and the activation energy Uop.Moreover,the polyene chain studies using the density functional theory B3LYP/6-31G* level reveal a prominent peak at 1525 cm-1 consisting of two closely spaced modes that are both dominated by C=C stretching coordinates of the polyene chain.

  13. Directly probing redox-linked quinones in photosystem II membrane fragments via UV resonance Raman scattering.

    Science.gov (United States)

    Chen, Jun; Yao, Mingdong; Pagba, Cynthia V; Zheng, Yang; Fei, Liping; Feng, Zhaochi; Barry, Bridgette A

    2015-01-01

    In photosynthesis, photosystem II (PSII) harvests sunlight with bound pigments to oxidize water and reduce quinone to quinol, which serves as electron and proton mediators for solar-to-chemical energy conversion. At least two types of quinone cofactors in PSII are redox-linked: QA, and QB. Here, we for the first time apply 257-nm ultraviolet resonance Raman (UVRR) spectroscopy to acquire the molecular vibrations of plastoquinone (PQ) in PSII membranes. Owing to the resonance enhancement effect, the vibrational signal of PQ in PSII membranes is prominent. A strong band at 1661 cm(-1) is assigned to ring CC/CO symmetric stretch mode (ν8a mode) of PQ, and a weak band at 469 cm(-1) to ring stretch mode. By using a pump-probe difference UVRR method and a sample jet technique, the signals of QA and QB can be distinguished. A frequency difference of 1.4 cm(-1) in ν8a vibrational mode between QA and QB is observed, corresponding to ~86 mV redox potential difference imposed by their protein environment. In addition, there are other PQs in the PSII membranes. A negligible anharmonicity effect on their combination band at 2130 cm(-1) suggests that the 'other PQs' are situated in a hydrophobic environment. The detection of the 'other PQs' might be consistent with the view that another functional PQ cofactor (not QA or QB) exists in PSII. This UVRR approach will be useful to the study of quinone molecules in photosynthesis or other biological systems.

  14. High resolution AFM and single cell resonance Raman spectroscopy of Geobacter sulfurreducens biofilms early in growth.

    Directory of Open Access Journals (Sweden)

    Nikolai eLebedev

    2014-08-01

    Full Text Available AFM and confocal resonance Raman microscopy (CRRM of single-cells were used to study the transition of anode-grown Geobacter sulfurreducens biofilms from lag phase (initial period of low current to exponential phase (subsequent period of rapidly increasing current. Results reveal that lag phase biofilms consist of lone cells and tightly packed single-cell thick clusters crisscrossed with extracellular linear structures that appear to be comprised of nodules approximately 20 nm in diameter aligned end to end. By early exponential phase cell clusters expand laterally and a second layer of closely packed cells begins to form on top of the first. Abundance of c-type cytochromes (c-Cyt is > 3-fold greater in 2-cell thick regions than in 1-cell thick regions. The results indicate that early biofilm growth involves two transformations. The first is from lone cells to 2-dimensionally associated cells during lag phase when current remains low. This is accompanied by formation of extracellular linear structures. The second is from 2- to 3-dimensionally associated cells during early exponential phase when current begins to increases rapidly. This is accompanied by a dramatic increase in c-Cyt abundance.

  15. Accurate Simulation of Resonance-Raman Spectra of Flexible Molecules: An Internal Coordinates Approach.

    Science.gov (United States)

    Baiardi, Alberto; Bloino, Julien; Barone, Vincenzo

    2015-07-14

    The interpretation and analysis of experimental resonance-Raman (RR) spectra can be significantly facilitated by vibronic computations based on reliable quantum-mechanical (QM) methods. With the aim of improving the description of large and flexible molecules, our recent time-dependent formulation to compute vibrationally resolved electronic spectra, based on Cartesian coordinates, has been extended to support internal coordinates. A set of nonredundant delocalized coordinates is automatically generated from the molecular connectivity thanks to a new general and robust procedure. In order to validate our implementation, a series of molecules has been used as test cases. Among them, rigid systems show that normal modes based on Cartesian and delocalized internal coordinates provide equivalent results, but the latter set is much more convenient and reliable for systems characterized by strong geometric deformations associated with the electronic transition. The so-called Z-matrix internal coordinates, which perform well for chain molecules, are also shown to be poorly suited in the presence of cycles or nonstandard structures.

  16. An ultraviolet resonance Raman study of dehydrogenase enzymes and their interactions with coenzymes and substrates.

    Science.gov (United States)

    Austin, J C; Wharton, C W; Hester, R E

    1989-02-21

    Ultraviolet resonance Raman (UVRR) spectra, with 260-nm excitation, are reported for oxidized and reduced nicotinamide adenine dinucleotides (NAD+ and NADH, respectively). Corresponding spectra are reported for these coenzymes when bound to the enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and liver and yeast alcohol dehydrogenases (LADH and YADH). The observed differences between the coenzyme spectra are interpreted in terms of conformation, hydrogen bonding, and general environment polarity differences between bound and free coenzymes and between coenzymes bound to different enzymes. The possibility of adenine protonation is discussed. UVRR spectra with 220-nm excitation also are reported for holo- and apo-GAPDH (GAPDH-NAD+ and GAPDH alone, respectively). In contrast with the 260-nm spectra, these show only bands due to vibrations of aromatic amino acid residues of the protein. The binding of coenzyme to GAPDH has no significant effect on the aromatic amino acid bands observed. This result is discussed in the light of the known structural change of GAPDH on binding coenzyme. Finally, UVRR spectra with 240-nm excitation are reported for GAPDH and an enzyme-substrate intermediate of GAPDH. Perturbations are reported for tyrosine and tryptophan bands on forming the acyl enzyme.

  17. Resonance Raman spectroscopic evaluation of skin carotenoids as a biomarker of carotenoid status for human studies.

    Science.gov (United States)

    Mayne, Susan T; Cartmel, Brenda; Scarmo, Stephanie; Jahns, Lisa; Ermakov, Igor V; Gellermann, Werner

    2013-11-15

    Resonance Raman spectroscopy (RRS) is a non-invasive method that has been developed to assess carotenoid status in human tissues including human skin in vivo. Skin carotenoid status has been suggested as a promising biomarker for human studies. This manuscript describes research done relevant to the development of this biomarker, including its reproducibility, validity, feasibility for use in field settings, and factors that affect the biomarker such as diet, smoking, and adiposity. Recent studies have evaluated the response of the biomarker to controlled carotenoid interventions, both supplement-based and dietary [e.g., provision of a high-carotenoid fruit and vegetable (F/V)-enriched diet], demonstrating consistent response to intervention. The totality of evidence supports the use of skin carotenoid status as an objective biomarker of F/V intake, although in the cross-sectional setting, diet explains only some of the variation in this biomarker. However, this limitation is also a strength in that skin carotenoids may effectively serve as an integrated biomarker of health, with higher status reflecting greater F/V intake, lack of smoking, and lack of adiposity. Thus, this biomarker holds promise as both a health biomarker and an objective indicator of F/V intake, supporting its further development and utilization for medical and public health purposes.

  18. Molecular effects of high-pressure processing on food studied by resonance Raman.

    Science.gov (United States)

    Tintchev, Filip; Wackerbarth, Hainer; Kuhlmann, Uwe; Toepfl, Stefan; Knorr, Dietrich; Hildebrandt, Peter; Heinz, Volker

    2010-02-01

    Pressurization may cause unwanted side effects including color or texture changes of fish and meat. The color changes of poultry, pork, and smoked salmon were studied by CIE L*, a*, b* system, and resonance Raman (RR). High-pressure processing (HPP) of pork and chicken meat resulted in significant color modification at pressures higher than 270 and 280 MPa, respectively. RR spectra were taken after a high-pressure treatment of pork meat. According to the RR-data, deoxymyoglobin is the dominating myoglobin species in pork meat. High-pressure treatment causes conformational changes resulting in a stabile nonnative ferrous myoglobin species while the ferrous myoglobin state is maintained. High-pressure treatment causes a decrease of the relative RR intensities of astaxanthin by salmon as probed with 514 nm. RR spectra excited at 413 nm revealed a heterogeneous broadening of astaxanthin bands accompanied by the formation of deoxymyoglobin or deoxyhemoglobin. The broadening is interpreted as the degradation products of astaxanthin. Obviously, the high-pressure treatment of smoked salmon triggers redox processes of astaxanthin and the heme protein.

  19. Effect of TiO2 particles on normal and resonance Raman spectra of coumarin 343: a theoretical investigation.

    Science.gov (United States)

    Yang, Linzhi; Wu, Wenpeng; Zhao, Yi

    2015-04-28

    It is well known that interfacial structures and charge transfer in dye-sensitized solar cells are extremely important for the enhancement of cell efficiency. Here, the normal Raman spectra (NRS) and resonance Raman spectra (RRS) of a C343-sensitized TiO2 cluster (Ti9O18) are theoretically predicted from combined electronic structure calculations and a vibrationally-resolved spectral method to reveal the relationship between interfacial geometries and excited-state dynamics. The results show that although the NRS of free C343 and the C343-TiO2 cluster correspond to the vibrational motions of C343 in a high frequency domain, their mode frequencies show obvious differences due to the interaction of the TiO2 cluster on C343, and several new Raman active fingerprint modes, such as bidentate chelating bonding modes, can be used to determine interfacial geometries. However, the resonance Raman activities of low-frequency modes are significantly enhanced and several modes from the TiO2 cluster can be observed, consistent with experimental measurements. Furthermore, the RRS from a locally excited state and a charge transfer state of C343-TiO2 are dramatically different, for instance, new Raman active modes with 1212 cm(-1), 1560 cm(-1) and 1602 cm(-1), corresponding to the motions of CH2 rocking, C=C/C-N/C=O stretching and C=O/C=C stretching, appear from the charge transfer state. The obtained information on mode-specific reorganization energies from these excited states is greatly helpful to understand and control interfacial electron transfer.

  20. Spatially resolved confocal resonant Raman microscopic analysis of anode-grown Geobacter sulfurreducens biofilms.

    Science.gov (United States)

    Lebedev, Nikolai; Strycharz-Glaven, Sarah M; Tender, Leonard M

    2014-02-03

    When grown on the surface of an anode electrode, Geobacter sulfurreducens forms a multi-cell thick biofilm in which all cells appear to couple the oxidation of acetate with electron transport to the anode, which serves as the terminal metabolic electron acceptor. Just how electrons are transported through such a biofilm from cells to the underlying anode surface over distances that can exceed 20 microns remains unresolved. Current evidence suggests it may occur by electron hopping through a proposed network of redox cofactors composed of immobile outer membrane and/or extracellular multi-heme c-type cytochromes. In the present work, we perform a spatially resolved confocal resonant Raman (CRR) microscopic analysis to investigate anode-grown Geobacter biofilms. The results confirm the presence of an intra-biofilm redox gradient whereby the probability that a heme is in the reduced state increases with increasing distance from the anode surface. Such a gradient is required to drive electron transport toward the anode surface by electron hopping via cytochromes. The results also indicate that at open circuit, when electrons are expected to accumulate in redox cofactors involved in electron transport due to the inability of the anode to accept electrons, nearly all c-type cytochrome hemes detected in the biofilm are oxidized. The same outcome occurs when a comparable potential to that measured at open circuit (-0.30 V vs. SHE) is applied to the anode, whereas nearly all hemes are reduced when an exceedingly negative potential (-0.50 V vs. SHE) is applied to the anode. These results suggest that nearly all c-type cytochrome hemes detected in the biofilm can be electrochemically accessed by the electrode, but most have oxidation potentials too negative to transport electrons originating from acetate metabolism. The results also reveal a lateral heterogeneity (x-y dimensions) in the type of c-type cytochromes within the biofilm that may affect electron transport to the

  1. Resonance Raman study of the active site of Coprinus cinereus peroxidase.

    Science.gov (United States)

    Smulevich, G; Feis, A; Focardi, C; Tams, J; Welinder, K G

    1994-12-27

    Resonance Raman (RR) spectra for the resting state ferric and the reduced ferrous forms of recombinant Coprinus cinereus peroxidase (CIP), obtained with different excitation wavelengths and in polarized light, are reported. The spectra are compared with those obtained previously for cytochrome c peroxidase expressed in Escherichia coli [(CCP(MI)] and horseradish peroxidase (HRP-C). Although the enzymic properties of CIP and HRP-C are similar, the RR data show that, in terms of the heme cavity structures, CIP and CCP(MI) are much more closely related to each other than to HRP-C. The ferric state of CIP at neutral pH is characteristic mainly of a five-coordinate high spin heme. However, the lower frequency of the v2 mode and a higher frequency of the v(C = C) vinyl stretching modes for CIP as compared to CCP, indicate a higher degree of vibrational coupling between the two modes in CIP. In addition, CIP is rather unstable under low laser power irradiation as an irreversible transition to a six-coordinate high spin heme followed by a second transition to a six-coordinate low spin heme is observed. This instability of CIP as compared to CCP(MI) is proposed to be a consequence of the presence of a distal Phe54 in CIP rather than the homologous Trp51 in CCP, as Trp51 is hydrogen-bonded to a distal water molecule located above the heme Fe thereby preventing its coordination in CCP. In CIP the FeII-His RR band has two components with frequencies at 230 and 211 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Resonant Raman spectroscopy study of swift heavy ion irradiated MoS2

    Science.gov (United States)

    Guo, Hang; Sun, Youmei; Zhai, Pengfei; Zeng, Jian; Zhang, Shengxia; Hu, Peipei; Yao, Huijun; Duan, Jinglai; Hou, Mingdong; Liu, Jie

    2016-08-01

    Molybdenum disulphide (MoS2) crystal samples were irradiated by swift heavy ions (209Bi and 56Fe). Hillock-like latent tracks were observed on the surface of irradiated MoS2 by atomic force microscopy. The modifications of properties of irradiated MoS2 were investigated by resonant Raman spectroscopy and ultraviolet-visible spectroscopy (UV-Vis). A new peak (E1u2, ∼385.7 cm-1) occurs near the in-plane E2g1 peak (∼383.7 cm-1) after irradiation. The two peaks shift towards lower frequency and broaden due to structural defects and stress with increasing fluence. When irradiated with high fluence, two other new peaks appear at ∼ 190 and ∼ 230 cm-1. The peak at ∼230 cm-1 is disorder-induced LA(M) mode. The presence of this mode indicates defects induced by irradiation. The feature at ∼460 cm-1 is composed of 2LA(M) (∼458 cm-1) and A2u (∼466 cm-1) mode. With increasing fluence, the integrated intensity ratio between 2LA(M) and A2u increases. The relative enhancement of 2LA(M) mode is in agreement with the appearance of LA(M) mode, which both demonstrate structural disorder in irradiated MoS2. The ∼423-cm-1 peak shifts toward lower frequency due to the decrease in exciton energy of MoS2, and this was demonstrated by the results of UV-Vis spectra. The decrease in exciton energy could be due to introduction of defect levels into band gap.

  3. Resonance Raman study of the oxygenation cycle of optically trapped single red blood cells in a microfluidic system

    Science.gov (United States)

    Ramser, Kerstin; Logg, Katarina; Enger, Jonas; Goksor, Mattias; Kall, Mikael; Hanstorp, Dag

    2004-10-01

    The average environmental response of red blood cells (RBCs) is routinely measured in ensemble studies, but in such investigations valuable information on the single cell level is obscured. In order to elucidate this hidden information is is important to enable the selection of single cells with certain properties while subsequent dynamics triggered by environmental stimulation are recorded in real time. It is also desirable to manipulate and control the cells under phsyiological conditions. As shown here, this can be achieved by combining optical tweezers with a confocal Raman set-up equipped with a microfluidic system. A micro-Raman set-up is combined with an optical trap with separate optical paths, lasers and objectives, which enables the acquisition of resonance Raman profils of single RBCs. The microfluidic system, giving full control over the media surrounding the cell, consists of a pattern of channels and reservoirs produced by electron beam lithography and moulded in PDMS. Fresh Hepes buffer or buffer containing sodium dithionite are transported through the channels using electro-osmotic flow, while the direct Raman response of the single optically trapped RBC is registered in another reservoir in the middle of the channel. Thus, it is possible to monitor the oxygenation cycle in a single cell and to study photo-induced chemistry. This experimental set-up has high potential for monitoring the drug response or conformational changes caused by other environmental stimuli for many types of single functional cells since "in vivo" conditions can be created.

  4. Single-molecule surface-enhanced Raman scattering of R6G in aqueous environment under non-resonance conditions

    Institute of Scientific and Technical Information of China (English)

    Enzhong Tan; Penggang Yin; Lidong Li; Lin Guo

    2011-01-01

    The single-molecule surface-enhanced Raman scattering (SERS) spectra of Rhodamine 6G (R6G) in an aqueous environment under non-resonance conditions are studied. Series of spectra are recorded in time-mapping mode, and intensity fluctuations of SERS signals and spectral diffusion are observed. The correlations between the presence frequency of SERS spectra and number of hot spots as well as the quantity of molecules in scattering volume are examined thoroughly. The results indicate that only molecules located at hot spots produce good signal-to-noise ratio Raman spectra and the origin of fluctuating SERS signals are mainly ascribed to the movement of hot spots.%@@ The single-molecule surface-enhanced Raman scattering(SERS) spectra of Rhodamine 6G(R6G) in anaqueous environment under non-resonance conditions are studied.Series of spectra are recorded in timemapping mode,and intensity fluctuations of SERS signals and spectral diffusion are observed.The correlations between the presence frequency of SERS spectra and number of hot spots as well as the quantity of molecules in scattering volume are examined thoroughly.

  5. Effective time-independent studies on resonance Raman spectroscopy of trans-stilbene including the Duschinsky effect

    Science.gov (United States)

    Lin, Na; Barone, Vincenzo; Cappelli, Chiara; Zhao, Xian; Ruud, Kenneth; Santoro, Fabrizio

    2013-07-01

    We simulate the resonance Raman spectra of trans-stilbene using a recently developed time-independent method that allows computations of the full two-dimensional spectrum as a function of the incident and scattered frequencies, including both the Franck-Condon and the Herzberg-Teller contributions. The potential energy surfaces (PESs) of the ground and resonant states are described in the harmonic approximation using density functional theory PBE0/6-31+G(d,p) calculations in gas phase and in cyclohexane. The simulated spectra are in good agreement with the experimental data [J. Chem. Phys. 83, 5000 (1985)] measured at four different excitation wavelengths, and allow us to unambiguously assign the main experimental bands. We perform an extensive comparison of the performance of four different vertical or adiabatic models for the PES of the resonant state, dissecting the effects of nuclear displacements and Duschinsky mixings on the spectra.

  6. Structure, spectra and antioxidant action of ascorbic acid studied by density functional theory, Raman spectroscopic and nuclear magnetic resonance techniques.

    Science.gov (United States)

    Singh, Gurpreet; Mohanty, B P; Saini, G S S

    2016-02-15

    Structure, vibrational and nuclear magnetic resonance spectra, and antioxidant action of ascorbic acid towards hydroxyl radicals have been studied computationally and in vitro by ultraviolet-visible, nuclear magnetic resonance and vibrational spectroscopic techniques. Time dependant density functional theory calculations have been employed to specify various electronic transitions in ultraviolet-visible spectra. Observed chemical shifts and vibrational bands in nuclear magnetic resonance and vibrational spectra, respectively have been assigned with the help of calculations. Changes in the structure of ascorbic acid in aqueous phase have been examined computationally and experimentally by recording Raman spectra in aqueous medium. Theoretical calculations of the interaction between ascorbic acid molecule and hydroxyl radical predicted the formation of dehydroascorbic acid as first product, which has been confirmed by comparing its simulated spectra with the corresponding spectra of ascorbic acid in presence of hydrogen peroxide.

  7. Structure, spectra and antioxidant action of ascorbic acid studied by density functional theory, Raman spectroscopic and nuclear magnetic resonance techniques

    Science.gov (United States)

    Singh, Gurpreet; Mohanty, B. P.; Saini, G. S. S.

    2016-02-01

    Structure, vibrational and nuclear magnetic resonance spectra, and antioxidant action of ascorbic acid towards hydroxyl radicals have been studied computationally and in vitro by ultraviolet-visible, nuclear magnetic resonance and vibrational spectroscopic techniques. Time dependant density functional theory calculations have been employed to specify various electronic transitions in ultraviolet-visible spectra. Observed chemical shifts and vibrational bands in nuclear magnetic resonance and vibrational spectra, respectively have been assigned with the help of calculations. Changes in the structure of ascorbic acid in aqueous phase have been examined computationally and experimentally by recording Raman spectra in aqueous medium. Theoretical calculations of the interaction between ascorbic acid molecule and hydroxyl radical predicted the formation of dehydroascorbic acid as first product, which has been confirmed by comparing its simulated spectra with the corresponding spectra of ascorbic acid in presence of hydrogen peroxide.

  8. Selective excitation of molecular mode in a mixture by femtosecond resonance-enhanced coherent anti-Stokes Raman scattering spectroscopy

    Institute of Scientific and Technical Information of China (English)

    He Ping; Li Si-Ning; Fan Rong-Wei; Li Xiao-Hui; Xia Yuan-Qin; Yu Xin; Chen De-Ying

    2012-01-01

    Femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy is used to investigate gaseous molecular dynamics.Due to the spectrally broad laser pulses,usually poorly resolved spectra result from this broad spectroscopy.However,it can be demonstrated that by the electronic resonance enhancement optimization control a selective excitation of specific vibrational mode is possible.Using an electronically resonance-enhanced effect,iodine molecule specific CARS spectroscopy can be obtained from a mixture of iodine-air at room temperature and a pressure of 1 atm (corresponding to a saturation iodine vapour as low as about 35 Pa).The dynamics on either the electronically excited state or the ground state of iodine molecules obtained is consistent with previous studies (vacuum,heated and pure iodine) in the femtosecond time resolved CARS spectroscopy,showing that an effective method of suppressing the non-resonant CARS background and other interferences is demonstrated.

  9. Chemical Enhancement on Surface-Enhanced Resonance Raman Scattering of Au3-1,4-BenzenedithioI-Au3 Junction

    Institute of Scientific and Technical Information of China (English)

    Xiu-rning Zhao; Xiao-rui Tian; Sha-sha Liu; Yuan-zuo Lia; Mao-du Chen

    2011-01-01

    Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) spectra of the 1,4-benzenedithiol molecule in the junction of two Au3 clusters have been calculated using density functional theory (DFT) and time-dependent DFT method.In order to investigate the contribution of charge transfer (CT) enhancement,the wavelengths of incident light are chosen to be at resonance with four representative excited states,which correspond to CT in four different forms.Compared with SERS spectrum,SERRS spectra are enhanced enormously with distinct enhancement factors,which can be attributed to CT resonance in different forms.

  10. Resonant Raman scattering in superconducting Ba1-xKxBiO3

    NARCIS (Netherlands)

    Menushenkov, AP; Troyan, IA; Eremets, MI

    2003-01-01

    The effect of the photon energy of the exciting laser radiation on the Raman spectra of Ba1 - xKxBiO3 with x = 0.25, 0.40, and 0.50 is studied. An increase in the laser wavelength from 488 to 750 nm scarcely affects the amplitudes and frequencies of the spectral lines in the Raman spectra of the non

  11. Raman E sub 1 , E sub 1 + DELTA sub 1 resonance in nonstressed quantum dots of germanium

    CERN Document Server

    Talochkin, A B; Efanov, A V; Kozhemyako, I G; Shumskij, V N

    2001-01-01

    The Raman light scattering on the optical phonons in the nonstressed Ge quantum dots, obtained in the GaAs/ZnSe/Ge/ZnSe structures is studied through the molecular-beam epitaxy. The E sub 1 , E sub 1 + DELTA sub 1 resonance energy shift, connected with quantization of the electron and hole states spectrum in the quantum dots is observed. Application of the simplest localization model with an account of the Ge electron states spectrum made it possible to explain the observed peculiarities

  12. A time-resolved resonance Raman study of chlorine dioxide photochemistry in water and acetonitrile

    Energy Technology Data Exchange (ETDEWEB)

    Hayes, S.C.; Philpott, M.P.; Mayer, S.G.; Reid, P.J. [Univ. of Washington, Seattle, WA (United States). Dept. of Chemistry

    1999-07-15

    The photochemistry of chlorine dioxide (OClO) has attracted much interest due to its participation in the atmospheric chlorine reservoir as well as its potential role in stratospheric ozone depletion. Since the environmental impact of OClO arises from its ability to produce atomic chlorine, understanding this phase-dependent reactivity is essential if models capable of predicting the environmental impact of OClO in both homogeneous and heterogeneous settings are to be obtained. The photochemistry of chlorine dioxide (OClO) in water and acetonitrile is investigated using time-resolved resonance Raman spectroscopy. Stokes and anti-Stokes spectra are measured as a function of time following photoexcitation using degenerate pump and probe wavelengths of 390 nm. For aqueous OClO, the time-dependent Stokes intensities are found to be consistent with the re-formation of ground-state OClO by subpicosecond geminate recombination of the primary ClO and O photofragments. This represents the first unequivocal demonstration of primary-photoproduct geminate recombination in the condensed-phase photochemistry of OClO. Anti-Stokes intensity corresponding to the OClO symmetric stretch is observed demonstrating that, following geminate recombination, excess vibrational energy is deposited along this coordinate. Analysis of the anti-Stokes decay kinetics demonstrates that, in water, intermolecular vibrational relaxation occurs with a time constant of {approximately}9 ps. For OClO dissolved in acetonitrile, the Stokes scattering intensities are consistent with a significant reduction in the geminate-recombination quantum yield relative to water. Comparison of the OClO anti-Stokes decay kinetics in acetonitrile and water demonstrates that the rate of intermolecular vibrational relaxation is {approximately}4 times smaller in acetonitrile. Finally, in both solvents the appearance of symmetric-stretch anti-Stokes intensity is significantly delayed relative to geminate recombination. This

  13. Optical pathology of human brain metastasis of lung cancer using combined resonance Raman and spatial frequency spectroscopies

    Science.gov (United States)

    Zhou, Yan; Liu, Cheng-hui; Pu, Yang; Cheng, Gangge; Zhou, Lixin; Chen, Jun; Zhu, Ke; Alfano, Robert R.

    2016-03-01

    Raman spectroscopy has become widely used for diagnostic purpose of breast, lung and brain cancers. This report introduced a new approach based on spatial frequency spectra analysis of the underlying tissue structure at different stages of brain tumor. Combined spatial frequency spectroscopy (SFS), Resonance Raman (RR) spectroscopic method is used to discriminate human brain metastasis of lung cancer from normal tissues for the first time. A total number of thirty-one label-free micrographic images of normal and metastatic brain cancer tissues obtained from a confocal micro- Raman spectroscopic system synchronously with examined RR spectra of the corresponding samples were collected from the identical site of tissue. The difference of the randomness of tissue structures between the micrograph images of metastatic brain tumor tissues and normal tissues can be recognized by analyzing spatial frequency. By fitting the distribution of the spatial frequency spectra of human brain tissues as a Gaussian function, the standard deviation, σ, can be obtained, which was used to generate a criterion to differentiate human brain cancerous tissues from the normal ones using Support Vector Machine (SVM) classifier. This SFS-SVM analysis on micrograph images presents good results with sensitivity (85%), specificity (75%) in comparison with gold standard reports of pathology and immunology. The dual-modal advantages of SFS combined with RR spectroscopy method may open a new way in the neuropathology applications.

  14. Understanding double-resonant Raman scattering in chiral carbon nanotubes: Diameter and energy dependence of the D mode

    Science.gov (United States)

    Herziger, Felix; Vierck, Asmus; Laudenbach, Jan; Maultzsch, Janina

    2015-12-01

    We present a theoretical model to describe the double-resonant scattering process in arbitrary carbon nanotubes (CNTs). We use this approach to investigate the defect-induced D mode in CNTs and unravel the dependence of the D -mode frequency on the CNT diameter and on the energy of the resonant optical transition. Our approach is based on the symmetry of the hexagonal lattice and geometric considerations; hence the method is independent of the exact model that is chosen to describe the electronic band structure or the phonon dispersion. We finally clarify the diameter dependence of this Raman mode that has been under discussion in the past and demonstrate that, depending on the experimental conditions, in general two different dependencies can be measured. We also prove that CNTs with an arbitrary chiral index can exhibit a D mode in their Raman spectrum, in contrast to previous symmetry-based arguments. Furthermore, we give a direct quantification of the curvature-induced phonon frequency corrections of the D mode in CNTs with respect to graphite.

  15. Silver Nanoparticle-Enhanced Resonance Raman Sensor of Chromium(III) in Seawater Samples.

    Science.gov (United States)

    Ly, Nguyễn Hoàng; Joo, Sang-Woo

    2015-04-29

    Tris(hydroxymethyl)aminomethane ethylenediaminetetraacetic acid (Tris-EDTA), upon binding Cr(III) in aqueous solutions at pH 8.0 on silver nanoparticles (AgNPs), was found to provide a sensitive and selective Raman marker band at ~563 cm-1, which can be ascribed to the metal-N band. UV-Vis absorption spectra also supported the aggregation and structural change of EDTA upon binding Cr(III). Only for Cr(III) concentrations above 500 nM, the band at ~563 cm-1 become strongly intensified in the surface-enhanced Raman scattering spectra. This band, due to the metal-EDTA complex, was not observed in the case of 50 mM of K+, Cd2+, Mg2+, Ca2+, Mn2+, Co2+, Na+, Cu2+, NH4+, Hg2+, Ni2+, Fe3+, Pb2+, Fe2+, and Zn2+ ions. Seawater samples containing K, Mg, Ca, and Na ion concentrations higher than 8 mM also showed the characteristic Raman band at ~563 cm-1 above 500 nM, validating our method. Our approach may be useful in detecting real water samples by means of AgNPs and Raman spectroscopy.

  16. UV resonance Raman spectroscopic studies of protein structure and dynamics (Conference Presentation)

    Science.gov (United States)

    Asher, Sanford A.; Punihaole, David; Dahlburg, Elizabeth M.; Jakubek, Ryan S.; Hong, Zhenmin

    2016-09-01

    UV Raman excitation into the 200 nm peptide bond electronic transitions enhance peptide bond amide vibrations of the backbone. A particular band (the amide III3) reports on the Ramachandran psi angle and peptide bond hydrogen bonding. This band is Raman scattered independently by each peptide bond with insignificant coupling between adjacent peptide bonds. Isotope editing of a peptide bond (by replacing the Calpha- H with Calpha- D) allows us to determine the frequency of individual peptide bonds within a peptide or protein to yield their psi angles. Consideration of the Boltzmann equilibria allows us to determine the psi angle Gibbs free energy landscape along the psi (un)folding coordinate that connects secondary structure conformations. The psi angle coordinate is the most important reaction coordinate necessary to understand mechanism(s) of protein folding. We have also discovered an analogous correlation for the primary amide sidechain of Gln. This allows us to monitor the hydrogen bonding and structure of this sidechain. We examine the details of peptide folding conformation dynamics with laser T-jumps where the water temperature is elevated by an 1.9 mM IR nsec laser pulse and we monitor the 200 nm UV Raman spectrum as a function of time. These spectra show the time evolution of conformation. We will discuss the role of salts on stabilizing conformations in solution

  17. Optically confined polarized resonance Raman studies in identifying crystalline orientation of sub-diffraction limited AlGaN nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Sivadasan, A. K., E-mail: sivankondazhy@gmail.com; Patsha, Avinash; Dhara, Sandip, E-mail: dhara@igcar.gov.in [Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2015-04-27

    An optical characterization tool of Raman spectroscopy with extremely weak scattering cross section tool is not popular to analyze scattered signal from a single nanostructure in the sub-diffraction regime. In this regard, plasmonic assisted characterization tools are only relevant in spectroscopic studies of nanoscale object in the sub-diffraction limit. We have reported polarized resonance Raman spectroscopic (RRS) studies with strong electron-phonon coupling to understand the crystalline orientation of a single AlGaN nanowire of diameter ∼100 nm. AlGaN nanowire is grown by chemical vapor deposition technique using the catalyst assisted vapor-liquid-solid process. The results are compared with the high resolution transmission electron microscopic analysis. As a matter of fact, optical confinement effect due to the dielectric contrast of nanowire with respect to that of surrounding media assisted with electron-phonon coupling of RRS is useful for the spectroscopic analysis in the sub-diffraction limit of 325 nm (λ/2N.A.) using an excitation wavelength (λ) of 325 nm and near ultraviolet 40× far field objective with a numerical aperture (N.A.) value of 0.50.

  18. A study on the Fermi resonance of phenol under the effects of pressure and temperature by Raman spectroscopy.

    Science.gov (United States)

    Li, DongFei; Hua, Zhong; Liu, ChengZhi; Fan, Cunbo; Sun, ChengLin; Li, ZuoWei; Chen, WanJin

    2015-02-05

    The ν1-ν18a Fermi resonance (FR) of phenol were investigated by pressure-dependent Raman spectroscopy from atmospheric up to P=15.2GPa and temperature-dependent Raman spectroscopy from 40 down to T=-180°C, respectively. In the case of pressure, we found the Fermi coupling coefficient W, which were calculated based on the FR theory, exposed a value turnover between 1.912 and 2.244GPa in the process of increasing the pressure. This turnover phenomenon of the Fermi coupling coefficient W has been ascribed to the crystal structure of phenol evolving towards a more symmetric structure with pressure, from a structure like a pseudo-threefold helical chain at ambient pressure to like a ribbon arrangement at 1.912GPa, then to adopt a herringbone arrangement at much higher pressure. On the other hand, we also found the Fermi coupling coefficient W exhibited monotonic reduction without turnover points appearing by decreasing the temperature. The tendencies of the Fermi coupling coefficient W with temperature were in good agreement with the pressure dependence of the Fermi coupling coefficient W in the region of ambient to 1.912GPa, indicating that the effect of pressure and temperature on the FR of phenol in this region might be the same. A conformation evolving induced by pressure and temperature on the ν1 and ν18a FR of phenol have been analyzed.

  19. A new combined nuclear magnetic resonance and Raman spectroscopic probe applied to in situ investigations of catalysts and catalytic processes

    Energy Technology Data Exchange (ETDEWEB)

    Camp, Jules C. J.; Mantle, Michael D. [Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA (United Kingdom); York, Andrew P. E. [Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH (United Kingdom); McGregor, James, E-mail: james.mcgregor@sheffield.ac.uk [Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2014-06-15

    Both Raman and nuclear magnetic resonance (NMR) spectroscopies are valuable analytical techniques capable of providing mechanistic information and thereby providing insights into chemical processes, including catalytic reactions. Since both techniques are chemically sensitive, they yield not only structural information but also quantitative analysis. In this work, for the first time, the combination of the two techniques in a single experimental apparatus is reported. This entailed the design of a new experimental probe capable of recording simultaneous measurements on the same sample and/or system of interest. The individual datasets acquired by each spectroscopic method are compared to their unmodified, stand-alone equivalents on a single sample as a means to benchmark this novel piece of equipment. The application towards monitoring reaction progress is demonstrated through the evolution of the homogeneous catalysed metathesis of 1‑hexene, with both experimental techniques able to detect reactant consumption and product evolution. This is extended by inclusion of magic angle spinning (MAS) NMR capabilities with a custom made MAS 7 mm rotor capable of spinning speeds up to 1600 Hz, quantified by analysis of the spinning sidebands of a sample of KBr. The value of this is demonstrated through an application involving heterogeneous catalysis, namely the metathesis of 2-pentene and ethene. This provides the added benefit of being able to monitor both the reaction progress (by NMR spectroscopy) and also the structure of the catalyst (by Raman spectroscopy) on the very same sample, facilitating the development of structure-performance relationships.

  20. Detection and imaging of quorum sensing in Pseudomonas aeruginosa biofilm communities by surface-enhanced resonance Raman scattering

    Science.gov (United States)

    Bodelón, Gustavo; Montes-García, Verónica; López-Puente, Vanesa; Hill, Eric H.; Hamon, Cyrille; Sanz-Ortiz, Marta N.; Rodal-Cedeira, Sergio; Costas, Celina; Celiksoy, Sirin; Pérez-Juste, Ignacio; Scarabelli, Leonardo; La Porta, Andrea; Pérez-Juste, Jorge; Pastoriza-Santos, Isabel; Liz-Marzán, Luis M.

    2016-11-01

    Most bacteria in nature exist as biofilms, which support intercellular signalling processes such as quorum sensing (QS), a cell-to-cell communication mechanism that allows bacteria to monitor and respond to cell density and changes in the environment. As QS and biofilms are involved in the ability of bacteria to cause disease, there is a need for the development of methods for the non-invasive analysis of QS in natural bacterial populations. Here, by using surface-enhanced resonance Raman scattering spectroscopy, we report rationally designed nanostructured plasmonic substrates for the in situ, label-free detection of a QS signalling metabolite in growing Pseudomonas aeruginosa biofilms and microcolonies. The in situ, non-invasive plasmonic imaging of QS in biofilms provides a powerful analytical approach for studying intercellular communication on the basis of secreted molecules as signals.

  1. Empirical Equation Based Chirality (n, m) Assignment of Semiconducting Single Wall Carbon Nanotubes from Resonant Raman Scattering Data

    Science.gov (United States)

    Arefin, Md Shamsul

    2012-01-01

    This work presents a technique for the chirality (n, m) assignment of semiconducting single wall carbon nanotubes by solving a set of empirical equations of the tight binding model parameters. The empirical equations of the nearest neighbor hopping parameters, relating the term (2n− m) with the first and second optical transition energies of the semiconducting single wall carbon nanotubes, are also proposed. They provide almost the same level of accuracy for lower and higher diameter nanotubes. An algorithm is presented to determine the chiral index (n, m) of any unknown semiconducting tube by solving these empirical equations using values of radial breathing mode frequency and the first or second optical transition energy from resonant Raman spectroscopy. In this paper, the chirality of 55 semiconducting nanotubes is assigned using the first and second optical transition energies. Unlike the existing methods of chirality assignment, this technique does not require graphical comparison or pattern recognition between existing experimental and theoretical Kataura plot.

  2. Empirical Equation Based Chirality (n, m Assignment of Semiconducting Single Wall Carbon Nanotubes from Resonant Raman Scattering Data

    Directory of Open Access Journals (Sweden)

    Md Shamsul Arefin

    2012-12-01

    Full Text Available This work presents a technique for the chirality (n, m assignment of semiconducting single wall carbon nanotubes by solving a set of empirical equations of the tight binding model parameters. The empirical equations of the nearest neighbor hopping parameters, relating the term (2n, m with the first and second optical transition energies of the semiconducting single wall carbon nanotubes, are also proposed. They provide almost the same level of accuracy for lower and higher diameter nanotubes. An algorithm is presented to determine the chiral index (n, m of any unknown semiconducting tube by solving these empirical equations using values of radial breathing mode frequency and the first or second optical transition energy from resonant Raman spectroscopy. In this paper, the chirality of 55 semiconducting nanotubes is assigned using the first and second optical transition energies. Unlike the existing methods of chirality assignment, this technique does not require graphical comparison or pattern recognition between existing experimental and theoretical Kataura plot.

  3. Resonance Raman spectra of TNT and RDX using vibronic theory, excited-state gradient, and complex polarizability approximations.

    Science.gov (United States)

    Al-Saidi, W A; Asher, Sanford A; Norman, Patrick

    2012-08-02

    Geometries, UV absorption bands, and resonance Raman (RR) cross sections of TNT and RDX are investigated using density functional theory (DFT) in conjunction with the Coulomb attenuated B3LYP exchange-correlation functional. The absorption and RR spectra are determined with use of vibronic (VB) theory, excited-state gradient, and complex polarizability (CPP) approximations. We examined low-energy isomers (two for TNT and four for RDX) whose energies differ by less than 1 kcal/mol, such that they would appreciably be populated at room temperature. The two TNT isomers differ by an internal rotation of the methyl group, while the four conformers of RDX differ by the arrangements of the nitro group relative to the ring. Our theoretical optical properties of the TNT and RDX isomers are in excellent agreement with experimental and recent CCSD-EOM results, respectively. For the two TNT isomers, the ultraviolet RR (UVRR) spectra are similar and in good agreement with recently measured experimental results. Additionally, the UVRR spectra computed using the excited-state and CPP approaches compare favorably with the VB theory results. On the other hand, the RR spectra of the RDX conformers differ from one another, reflecting the importance of the positioning of the NO2 groups with respect to the ring. In the gas phase or in solution, RDX would give a spectrum associated with a conformationally averaged structure. It is encouraging that the computed spectra of the conformers show similarities to recent measured RDX spectra in acetonitrile solution, and reproduce the 10-fold decrease in the absolute Raman cross sections of RDX compared to TNT for the observed 229 nm excitation. We show that in TNT and RDX vibrational bands that couple to NO2 or the ring are particularly resonance enhanced. Finally, the computed RDX spectra of the conformers present a benchmark for understanding the RR spectra of the solid-phase polymorphs of RDX.

  4. In Situ Resonance Raman Spectra of Organic Pigments in Momo Coral

    Institute of Scientific and Technical Information of China (English)

    Fan Luwei; Yang Mingxing

    2008-01-01

    In this study, Raman scattering measurements were obtained for momo corals covering their typical range of colors. Three different excitation wavelengths (785, 633, 514 nm) are used for the same samples at the same points. All the samples show the two major Raman features of polyenic compounds assigned to double carbon-carbon (C=C) stretching vibration at approximately 1 500 cm-1 and single carbon-carbon (C--C) stretching vibration at approximately 1 130 cm-1 bond stretching mode. These peaks are not detected in the corresponding white parts of momo corals. However, somechanges in intensities, shape, and position of C=C stretching vibrations of the same point are observed by using different excitation wavelengths. The exact position of C-C stretching vibration of polyenic molecules depends strongly on the number of double bonds contained in their polyenic chain. In addition, the number of double bonds contained in the polyenic chains shows that different colors of the red momo coral are caused by different mixtures of polyenic compounds.

  5. A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds of Scots pine ( Pinus sylvestris) wood . Part I: Lipophilic compounds

    Science.gov (United States)

    Nuopponen, M.; Willför, S.; Jääskeläinen, A.-S.; Sundberg, A.; Vuorinen, T.

    2004-11-01

    The wood resin in Scots pine ( Pinus sylvestris) stemwood and branch wood were studied using UV resonance Raman (UVRR) spectroscopy. UVRR spectra of the sapwood and heartwood hexane extracts, solid wood samples and model compounds (six resin acids, three fatty acids, a fatty acid ester, sitosterol and sitosterol acetate) were collected using excitation wavelengths of 229, 244 and 257 nm. In addition, visible Raman spectra of the fatty and resin acids were recorded. Resin compositions of heartwood and sapwood hexane extracts were determined using gas chromatography. Raman signals of both conjugated and isolated double bonds of all the model compounds were resonance enhanced by UV excitation. The oleophilic structures showed strong bands in the region of 1660-1630 cm -1. Distinct structures were enhanced depending on the excitation wavelength. The UVRR spectra of the hexane extracts showed characteristic bands for resin and fatty acids. It was possible to identify certain resin acids from the spectra. UV Raman spectra collected from the solid wood samples containing wood resin showed a band at ˜1650 cm -1 due to unsaturated resin components. The Raman signals from extractives in the resin rich branch wood sample gave even more strongly enhanced signals than the aromatic lignin.

  6. A Study of the Cis—Trans Isomers of β—Apo—12′—Carotenal By Resonance Raman Spectroscopy at Low Temperature

    Institute of Scientific and Technical Information of China (English)

    YingHu; TadashiMizoguchi; 等

    1995-01-01

    Resonance Raman spectroscopy is a powerful technique to study the cis-trans configurations and the intermolecular interactions of carotenoids bound to pigmentprotein complexes[1,2].In the present invertigation,we studied a set of cis-trans isomers of β-Apo-12′-carotenal,the conjugated chain of which has a length in -between those of β-carotene and retinal,to examine whether the configurational key Raman lines which have been established for β-carotene are still valid for β-Apo-12′-caotenal[3

  7. Structural characterization of titania by X-ray diffraction, photoacoustic, Raman spectroscopy and electron paramagnetic resonance spectroscopy.

    Science.gov (United States)

    Kadam, R M; Rajeswari, B; Sengupta, Arijit; Achary, S N; Kshirsagar, R J; Natarajan, V

    2015-02-25

    A titania mineral (obtained from East coast, Orissa, India) was investigated by X-ray diffraction (XRD), photoacoustic spectroscopy (PAS), Raman and Electron Paramagnetic Resonance (EPR) studies. XRD studies indicated the presence of rutile (91%) and anatase (9%) phases in the mineral. Raman investigation supported this information. Both rutile and anatase phases have tetragonal structure (rutile: space group P4(2)/mnm, a=4.5946(1) Å, c=2.9597(1) Å, V=62.48(1) (Å)(3), Z=2; anatase: space group I4(1)/amd, 3.7848(2) Å, 9.5098(11) Å, V=136.22(2) (Å)(3), Z=4). The deconvoluted PAS spectrum showed nine peaks around 335, 370, 415,485, 555, 605, 659, 690,730 and 785 nm and according to the ligand field theory, these peaks were attributed to the presence of V(4+), Cr(3+), Mn(4+) and Fe(3+) species. EPR studies revealed the presence of transition metal ions V(4+)(d(1)), Cr(3+)(d(3)), Mn(4+)(d(3)) and Fe(3+)(d(5)) at Ti(4+) sites. The EPR spectra are characterized by very large crystal filed splitting (D term) and orthorhombic distortion term (E term) for multiple electron system (s>1) suggesting that the transition metal ions substitute the Ti(4+) in the lattice which is situated in distorted octahedral coordination of oxygen. The possible reasons for observation of unusually large D and E term in the EPR spectra of transition metal ions (S=3/2 and 5/2) are discussed.

  8. Coherent anti-Stokes Raman spectroscopy in the presence of strong resonant signal from background molecules

    CERN Document Server

    Bitter, Martin

    2012-01-01

    Optical spectroscopy with broadband femtosecond laser pulses often involves simultaneous excitation of multiple molecular species with close resonance frequencies. Interpreting the collective optical response from molecular mixtures typically requires Fourier analysis of the detected time-resolved signal. We propose an alternative method of separating coherent optical responses from two molecular species with neighboring excitation resonances (here, vibrational modes of oxygen and carbon dioxide). We utilize ro-vibrational coupling as a mechanism of suppressing the strong vibrational response from the dominating molecular species (O$_{2}$). Coherent ro-vibrational dynamics lead to long "silence windows" of zero signal from oxygen molecules. In these silence windows, the detected signal stems solely from the minority species (CO$_{2}$) enabling background-free detection and characterization of the O$_2$/CO$_2$ mixing ratio. In comparison to a Fourier analysis, our technique does not require femtosecond time re...

  9. The effect of chemical variations on the structural polarity of relaxor ferroelectrics studied by resonance Raman spectroscopy.

    Science.gov (United States)

    Rohrbeck, A; de la Flor, G; Aroyo, M I; Gospodinov, M; Bismayer, U; Mihailova, B

    2016-11-30

    Resonance Raman spectroscopy was applied to doped PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 relaxor ferroelectrics, to better understand the effect of composition disorder on the mesoscopic-scale polar order in complex perovskite-type (ABO3) ferroelectrics. The excitation photon energy used was 3.8 eV, which is slightly above the energy gap and corresponds to the maximum of the optical dielectric permittivity. Group-theory analysis reveals that the resonance Raman scattering (RRS) observed under these conditions is allowed only in polar crystal classes. Therefore, RRS is dominated by the atomic dynamics of nanoregions with coherent polar distortions, which considerably facilitates the comparison of polar order in various compounds. The results show that A-site doping (Ba(2+), Sr(2+), La(3+), Bi(3+)) has significantly stronger effect on the structural polarity than the introduction of a third element at the B site (Nb(5+) or Sn(4+) doped in PbSc0.5Ta0.5O3). The A-site substitution by cations that in contrast to Pb(2+) have isotropic outermost electron shells disturbs the system of lone-pair electrons, thus reducing the correlation length of coupled polar distortions and the strength of the electric field associated with the mean polarization of polar nanoregions. A-site doping with larger cations (Ba(2+)) augments the polar deformation of the individual BO6 octahedra due to local elastic fields. As a result, such A-site doping intensifies the initial structural polarity at high temperatures and prevails the enlargement of the polar fraction at low temperatures. A-site doping with smaller cations (Sr(2+), La(3+)), regardless if they are isovalent or aliovalent to Pb(2+), increases the correlation length of antiferrodistortive order (BO6 tilts), which in turn assists the development of double-perovskite structure with coherent local polar distortions. A-site doping with aliovalent cations (Bi(3+)) having the same outermost electron shell and ionic radius as the host A

  10. The effect of chemical variations on the structural polarity of relaxor ferroelectrics studied by resonance Raman spectroscopy

    Science.gov (United States)

    Rohrbeck, A.; de la Flor, G.; Aroyo, M. I.; Gospodinov, M.; Bismayer, U.; Mihailova, B.

    2016-11-01

    Resonance Raman spectroscopy was applied to doped PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 relaxor ferroelectrics, to better understand the effect of composition disorder on the mesoscopic-scale polar order in complex perovskite-type (ABO3) ferroelectrics. The excitation photon energy used was 3.8 eV, which is slightly above the energy gap and corresponds to the maximum of the optical dielectric permittivity. Group-theory analysis reveals that the resonance Raman scattering (RRS) observed under these conditions is allowed only in polar crystal classes. Therefore, RRS is dominated by the atomic dynamics of nanoregions with coherent polar distortions, which considerably facilitates the comparison of polar order in various compounds. The results show that A-site doping (Ba2+, Sr2+, La3+, Bi3+) has significantly stronger effect on the structural polarity than the introduction of a third element at the B site (Nb5+ or Sn4+ doped in PbSc0.5Ta0.5O3). The A-site substitution by cations that in contrast to Pb2+ have isotropic outermost electron shells disturbs the system of lone-pair electrons, thus reducing the correlation length of coupled polar distortions and the strength of the electric field associated with the mean polarization of polar nanoregions. A-site doping with larger cations (Ba2+) augments the polar deformation of the individual BO6 octahedra due to local elastic fields. As a result, such A-site doping intensifies the initial structural polarity at high temperatures and prevails the enlargement of the polar fraction at low temperatures. A-site doping with smaller cations (Sr2+, La3+), regardless if they are isovalent or aliovalent to Pb2+, increases the correlation length of antiferrodistortive order (BO6 tilts), which in turn assists the development of double-perovskite structure with coherent local polar distortions. A-site doping with aliovalent cations (Bi3+) having the same outermost electron shell and ionic radius as the host A-site Pb2+ cations leads to

  11. Resonance Raman, electron paramagnetic resonance, and density functional theory calculations of a phenolate-bound iron porphyrin complex: electrostatic versus covalent contribution to bonding.

    Science.gov (United States)

    Das, Pradip Kumar; Dey, Abhishek

    2014-07-21

    Resonance Raman (rR), electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations of a phenolate-bound iron porphyrin complex are reported. The complex is found to exist in a five-coordinate high-spin state in a noncoordinating solvent and in a six-coordinate low-spin state in a coordinating solvent. The vibrations originating from the iron phenolate-bound chromophores reproduced those reported for heme tyrosine active sites in nature. The EPR parameters and iron-pyrrole (Fe-Npyr) vibrations of phenolate, thiolate, and imidazole ligated iron porphyrin complexes indicate that the phenolate axial ligand acts as a π anisotropic ligand, which is more covalent than a neutral imidazole ligand but less covalent than a thiolate axial ligand. While the Fe(III/II) potential of the phenolate compound in a noncoordinating solvent is 500 mV more negative than that of the imidazole-bound complex, it is also 110 mV more negative than that of the thiolate-bound complex. DFT calculations reproduce the geometry and vibrational frequencies and show that while both phenolate and thiolate axial ligands bear π and σ interaction with the ferric center, the former is significantly less covalent than the thiolate. The higher covalency of the thiolate ligand is responsible for the lower Fe-Npyr vibration and higher V/λ (from EPR) of the thiolate-bound complexes relative to those of the phenolate-bound complex, whereas the greater electrostatic stabilization of the Fe(III)-OPh bond is responsible for lowering the Fe(III/II) E° of the phenolate-bound complex relative to that of the thiolate-bound complex in a medium having a reasonable dielectric constant.

  12. Protonation state and structural changes of the tetrapyrrole chromophore during the Pr --> Pfr phototransformation of phytochrome: a resonance Raman spectroscopic study.

    Science.gov (United States)

    Kneip, C; Hildebrandt, P; Schlamann, W; Braslavsky, S E; Mark, F; Schaffner, K

    1999-11-16

    The photoconversion of phytochrome (phytochrome A from Avena satina) from the inactive (Pr) to the physiologically active form (Pfr) was studied by near-infrared Fourier transform resonance Raman spectroscopy at cryogenic temperatures, which allow us to trap the intermediate states. Nondeuterated and deuterated buffer solutions were used to determine the effect of H/D exchange on the resonance Raman spectra. For the first time, reliable spectra of the "bleached" intermediates meta-R(A) and meta-R(C) were obtained. The vibrational bands in the region 1300-1700 cm(-)(1), which is particularly indicative of structural changes in tetrapyrroles, were assigned on the basis of recent calculations of the Raman spectra of the chromophore in C-phycocyanin and model compounds [Kneip, C., Hildebrandt, P., Németh, K., Mark, F., Schaffner, K. (1999) Chem. Phys. Lett. 311, 479-485]. The experimental resonance Raman spectra Pr are compatible with the Raman spectra calculated for the protonated ZZZasa configuration, which hence is suggested to be the chromophore structure in this parent state of phytochrome. Furthermore, marker bands could be identified that are of high diagnostic value for monitoring structural changes in individual parts of the chromophore. Specifically, it could be shown that not only in the parent states Pr and Pfr but also in all intermediates the chromophore is protonated at the pyrroleninic nitrogen. The spectral changes observed for lumi-R confirm the view that the photoreaction of Pr is a Z --> E isomerization of the CD methine bridge. The subsequent thermal decay reaction to meta-R(A) includes relaxations of the CD methine bridge double bond, whereas the formation of meta-R(C) is accompanied by structural adaptations of the pyrrole rings B and C in the protein pocket. The far-reaching similarities between the chromophores of meta-R(A) and Pfr suggest that in the step meta-R(A) --> Pfr the ultimate structural changes of the protein matrix occur.

  13. Experimental and theoretical study of red-shifted solitonic resonant radiation in photonic crystal fibers and generation of radiation seeded Raman solitons

    CERN Document Server

    Bose, Surajit; Chattopadhyay, Rik; Pal, Mrinmay; Bhadra, Shyamal K

    2015-01-01

    The red shifted solitonic resonant radiation is a fascinating phase matching phenomenon that occurs when an optical pulse, launched in the normal dispersion regime of photonic crystal fiber, radiates across the zero dispersion wavelength. The formation of such phase-matched radiation is independent of the generation of any optical soliton and mainly governed by the leading edge of input pump which forms a shock front. The radiation is generated at the anomalous dispersion regime and found to be confined both in time and frequency domain. We experimentally investigate the formation of such radiations in photonic crystal fibers with detailed theoretical analysis. Our theoretical predictions corroborate well with experimental results. Further we extend our study for long length fiber and investigate the interplay between red-shifted solitonic resonant radiation and intrapulse Raman scattering (IPRS). It is observed that series of radiation-seeded Raman solitons are generated in anomalous dispersion regime.

  14. A resonance Raman spectroscopic and CASSCF investigation of the Franck-Condon region structural dynamics and conical intersections of thiophene.

    Science.gov (United States)

    Wu, Xian-Fang; Zheng, Xuming; Wang, Hui-Gang; Zhao, Yan-Yin; Guan, Xiangguo; Phillips, David Lee; Chen, Xuebo; Fang, Weihai

    2010-10-07

    Resonance Raman spectra were acquired for thiophene in cyclohexane solution with 239.5 and 266 nm excitation wavelengths that were in resonance with ∼240 nm first intense absorption band. The spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mostly along the reaction coordinates of six totally symmetry modes and three nontotally symmetry modes. The appearance of the nontotally symmetry modes, the C-S antisymmetry stretch +C-C=C bend mode ν(21)(B(2)) at 754 cm(-1) and the H(7)C(3)-C(4)H(8) twist ν(9)(A(2)) at 906 cm(-1), suggests the existence of two different types of vibronic-couplings or curve-crossings among the excited states in the Franck-Condon region. The electronic transition energies, the excited state structures, and the conical intersection points (1)B(1)/(1)A(1) and (1)B(2)/(1)A(1) between 2 (1)A(1) and 1 (1)B(2) or 1 (1)B(1) potential energy surfaces of thiophene were determined by using complete active space self-consistent field theory computations. These computational results were correlated with the Franck-Condon region structural dynamics of thiophene. The ring opening photodissociation reaction pathway through cleavage of one of the C-S bonds and via the conical intersection point (1)B(1)/(1)A(1) was revealed to be the predominant ultrafast reaction channel for thiophene in the lowest singlet excited state potential energy hypersurface, while the internal conversion pathway via the conical intersection point (1)B(2)/(1)A(1) was found to be the minor decay channel in the lowest singlet excited state potential energy hypersurface.

  15. Determination of Temperature-Dependent Stress State in Thin AlGaN Layer of AlGaN/GaN HEMT Heterostructures by Near-Resonant Raman Scattering

    Directory of Open Access Journals (Sweden)

    Yanli Liu

    2015-01-01

    Full Text Available The temperature-dependent stress state in the AlGaN barrier layer of AlGaN/GaN heterostructure grown on sapphire substrate was investigated by ultraviolet (UV near-resonant Raman scattering. Strong scattering peak resulting from the A1(LO phonon mode of AlGaN is observed under near-resonance condition, which allows for the accurate measurement of Raman shifts with temperature. The temperature-dependent stress in the AlGaN layer determined by the resonance Raman spectra is consistent with the theoretical calculation result, taking lattice mismatch and thermal mismatch into account together. This good agreement indicates that the UV near-resonant Raman scattering can be a direct and effective method to characterize the stress state in thin AlGaN barrier layer of AlGaN/GaN HEMT heterostructures.

  16. Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics

    Science.gov (United States)

    Kunnus, Kristjan; Josefsson, Ida; Rajkovic, Ivan; Schreck, Simon; Quevedo, Wilson; Beye, Martin; Grübel, Sebastian; Scholz, Mirko; Nordlund, Dennis; Zhang, Wenkai; Hartsock, Robert W.; Gaffney, Kelly J.; Schlotter, William F.; Turner, Joshua J.; Kennedy, Brian; Hennies, Franz; Techert, Simone; Wernet, Philippe; Odelius, Michael; Föhlisch, Alexander

    2016-10-01

    Ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbital and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)5 in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given—which will be covered experimentally by upcoming transform-limited x-ray sources.

  17. Single v. multiple measures of skin carotenoids by resonance Raman spectroscopy as a biomarker of usual carotenoid status

    Science.gov (United States)

    Scarmo, Stephanie; Cartmel, Brenda; Lin, Haiqun; Leffell, David J.; Ermakov, Igor V.; Gellermann, Werner; Bernstein, Paul S.; Mayne, Susan T.

    2013-01-01

    Resonance Raman spectroscopy (RRS) is a non-invasive method of assessing carotenoid status in the skin, which has been suggested as an objective indicator of fruit/vegetable intake. The present study assessed agreement and identified predictors of single v. multiple RRS measures of skin carotenoid status. A total of seventy-four participants had their skin carotenoid status measured in the palm of the hand by RRS at six time points over 6 months. Questionnaires were administered to collect information on demographic, lifestyle and dietary data. Mean age of the participants was 36.6 years, 62.2% were female, 83.8% Caucasian and 85.1% were non-smoking at baseline. There was a good agreement between a single measure of skin carotenoids by RRS and multiple measures (weighted κ = 0.80; 95% CI 0.72, 0.88). The same variables were significantly associated with carotenoid status based on single or multiple measures, including a positive association with intake of total carotenoids (Pseason of measurement (P≤0.05). The exception was recent sun exposure, which emerged as a significant predictor of lower carotenoid status only when using multiple RRS measures (P≤0.01). A single RRS measure was reasonably accurate at classifying usual skin carotenoid status. Researchers using RRS may want to take into account other factors that are associated with the biomarker, including season of measurement and recent sun exposure. PMID:23351238

  18. Investigation of the electronic structure of CuO by means of resonant X-ray Raman scattering

    CERN Document Server

    Doering, G

    2001-01-01

    excited state. By means of a perturbation theoretical treatment of the Coulomb interaction between the core-hole and the 3d-electrons an expression for the cross-section of the shakeup-process is derived. Thereby the observed excitation energy dependence of the shakeup-satellite's intensity and its position in the energy loss spectrum can be explained. Furthermore, its intensity shows a strong dependence on the scattering angle in certain scattering geometries. By means of a model calculation this dependence is attributed to a polarisation-effect. In this thesis the electronic structure of CuO is investigated utilizing resonant X-ray Raman Scattering. The special properties of this transition metal oxide are emphasized and the potential of the method is shown. First it is explained how one can draw conclusions about the unoccupied density of states of CuO and its symmetry from measurements of the copper K-alpha fluorescence by using an excitation energy of a few eV below the absorption threshold. By this mean...

  19. Single v. multiple measures of skin carotenoids by resonance Raman spectroscopy as a biomarker of usual carotenoid status.

    Science.gov (United States)

    Scarmo, Stephanie; Cartmel, Brenda; Lin, Haiqun; Leffell, David J; Ermakov, Igor V; Gellermann, Werner; Bernstein, Paul S; Mayne, Susan T

    2013-09-14

    Resonance Raman spectroscopy (RRS) is a non-invasive method of assessing carotenoid status in the skin, which has been suggested as an objective indicator of fruit/vegetable intake. The present study assessed agreement and identified predictors of single v. multiple RRS measures of skin carotenoid status. A total of seventy-four participants had their skin carotenoid status measured in the palm of the hand by RRS at six time points over 6 months. Questionnaires were administered to collect information on demographic, lifestyle and dietary data. Mean age of the participants was 36.6 years, 62.2% were female, 83.8% Caucasian and 85.1% were non-smoking at baseline. There was a good agreement between a single measure of skin carotenoids by RRS and multiple measures (weighted κ = 0.80; 95% CI 0.72, 0.88). The same variables were significantly associated with carotenoid status based on single or multiple measures, including a positive association with intake of total carotenoids (Pcarotenoid status only when using multiple RRS measures (P≤ 0.01). A single RRS measure was reasonably accurate at classifying usual skin carotenoid status. Researchers using RRS may want to take into account other factors that are associated with the biomarker, including season of measurement and recent sun exposure.

  20. Microanalysis of organic pigments and glazes in polychrome works of art by surface-enhanced resonance Raman scattering.

    Science.gov (United States)

    Leona, Marco

    2009-09-01

    Scientific studies of works of art are usually limited by severe sampling restrictions. The identification of organic colorants, a class of compounds relevant for attribution and provenance studies, is further complicated by the low concentrations at which these compounds are used and by the interference of the protein-, gum-, or oil-binding media present in pigment and glaze samples. Surface-enhanced resonance Raman scattering (SERRS) was successfully used to identify natural organic colorants in archaeological objects, polychrome sculptures, and paintings from samples smaller than 25 microm in diameter. The key factors in achieving the necessary sensitivity were a highly active stabilized silver colloid, obtained by the reproducible microwave-supported reduction of silver sulfate with glucose and sodium citrate, and a non-extractive hydrolysis sample treatment procedure that maximizes dye adsorption on the colloid. Among the examples presented are the earliest so far found occurrence of madder lake (in a 4,000 years old Egyptian object dating to the Middle Kingdom period), and the earliest known occurrence in Europe of the South Asian dyestuff lac (in the Morgan Madonna, a 12th century polychrome sculpture from Auvergne, France).

  1. Investigation of resonant Raman scattering in type II GaAs/AlAs superlattices

    CERN Document Server

    Choi, H

    2001-01-01

    GAMMA-related Type I outgoing RR spectra within several theoretical models. Thereby, the mechanisms of the Type II RR scattering, the origins of the RR lineshape and the polarisation dependence, are fully explained, clarifying the spectral features observed in the GaAs zone-centre optic phonon region. The Type II resonance also allows the observation of zone boundary (X-point) phonons from intervalley (IV) scattering. A model of the IV electron-phonon interaction involving X conduction band electrons and zone boundary phonons in Type II SLs is presented. With the predicted SL selection rules for IV scattering, the simultaneous observation of both the zone-boundary longitudinal acoustic and optic phonons can be understood and the spectral features quantitatively explained. As a consequence of the band alignment in GaAs/AIAs superlattices (SLs) and the indirect nature of bulk AIAs, quantum confinement can be used to engineer a Type II system. This produces an electron population in the AIAs longitudinal (X sub ...

  2. Probing the pigment binding sites in LHCII with resonance Raman spectroscopy: The effect of mutations at S123.

    Science.gov (United States)

    Kish, Elizabeth; Wang, Ke; Llansola-Portoles, Manuel J; Ilioaia, Cristian; Pascal, Andrew A; Robert, Bruno; Yang, Chunhong

    2016-09-01

    Resonance Raman spectroscopy was used to evaluate the structure of light-harvesting chlorophyll (Chl) a/b complexes of photosystem II (LHCII), reconstituted from wild-type (WT) and mutant apoproteins over-expressed in Escherichia coli. The point mutations involved residue S123, exchanged for either P (S123P) or G (S123G). In all reconstituted proteins, lutein 2 displayed a distorted conformation, as it does in purified LHCII trimers. Reconstituted WT and S123G also exhibited a conformation of bound neoxanthin (Nx) molecules identical to the native protein, while the S123P mutation was found to induce a change in Nx conformation. This structural change of neoxanthin is accompanied by a blue shift of the absorption of this carotenoid molecule. The interactions assumed by (and thus the structure of the binding sites of) the bound Chls b were found identical in all the reconstituted proteins, and only marginally perturbed as compared to purified LHCII. The interactions assumed by bound Chls a were also identical in purified LHCII and the reconstituted WT. However, the keto carbonyl group of one Chl a, originally free-from-interactions in WT LHCII, becomes involved in a strong H-bond with its environment in LHCII reconstituted from the S123P apoprotein. As the absorption in the Qy region of this protein is identical to that of the LHCII reconstituted from the WT apoprotein, we conclude that the interaction state of the keto carbonyl of Chl a does not play a significant role in tuning the binding site energy of these molecules.

  3. X-ray absorption and resonance raman spectroscopy of human myeloperoxidase at neutral and acid pH.

    Science.gov (United States)

    Yue, K T; Taylor, K L; Kinkade, J M; Sinclair, R B; Powers, L S

    1997-04-01

    Myeloperoxidase (MPO), an important enzyme in the oxygen-dependent host defense system of human polymorphonuclear leukocytes, utilizes hydrogen peroxide to catalyze the production of hypochlorous acid, an oxidizing bactericidal agent. While MPO shows significant sequence homology with other peroxidases and this homology is particularly striking among the active-site residues, MPO exhibits unusual spectral features and the unique ability to catalyze the oxidation of chloride ions. We have investigated the MPO active-site with X-ray absorption (XAS) and resonance Raman (RRS) spectroscopies at neutral pH and also at the physiological acidic pH (pH approximately 3) and have compared these results with those of horseradish peroxidase (HRP). At pH 7.5, XAS results show that the iron heme active site is 6-coordinate where the distal ligand is likely nitrogen or oxygen, but not sulfur. The heme is distorted compared to HRP, other peroxidases, and heme compounds, but at pH approximately 3, the distal ligand is lost and the heme is less distorted. RRS results under identical pH conditions show that the skeletal core-size sensitive modes and v3 are shifted to higher frequency at pH approximately 3 indicating a 6- to 5-coordination change of high spin ferric heme. In addition, a new band at 270 cm(-1) is observed at pH approximately 3 which is consistent with the loss of the sixth ligand. The higher symmetry of the heme at pH approximately 3 is reflected by a single v4 mode in the (RRS) spectrum. HRP also loses its loosely associated distal water at this pH, but little change in heme distortion is observed. This change suggests that loss of the distal ligand in MPO releases stress on the heme which may facilitate binding of chloride ion.

  4. Suppression of resonance Raman scattering via ground state depletion towards sub-diffraction-limited label-free microscopy

    NARCIS (Netherlands)

    Rieger, S.; Fischedick, M.; Boller, K-J.; Fallnich, C.

    2016-01-01

    We report on the first experimental demonstration of the suppression of spontaneous Raman scattering via ground state depletion. The concept of Raman suppression can be used to achieve sub-diffraction-limited resolution in label-free microscopy by exploiting spatially selective signal suppression wh

  5. A resonance Raman enhancement mechanism for axial vibrational modes in the pyridine adduct of myoglobin proximal cavity mutant (H93G).

    Science.gov (United States)

    Franzen, Stefan; Brown, Derek; Gaff, John; Delley, B

    2012-09-06

    The proximal cavity mutant of myoglobin consists of a mutation of the proximal histidine to glycine (H93G), which permits exogenous ligands to bind to the heme iron. A non-native pyridine ligand can ligate to the heme to yield a five-coordinate adduct, H93G(Pyr), that cannot be formed freely in solution since the six-coordinate bis-pyridine adduct is more stable than the five-coordinate adduct. We have used resonance Raman spectroscopy in the Soret band region of the heme to study the enhancement of axial vibrations of bound pyridine in the H93G(Pyr) adduct. The observation that the pyridine ring breathing mode (ν(1)) and the symmetric ring stretching (ν(3)) modes are enhanced under these conditions is explained by a computational approach that shows that coupling of the π-system of the heme with the p-orbitals of the pyridine is analogous to π-backbonding in diatomic ligand adducts of heme proteins. The result has the broader significance that it suggests that the resonance enhancement of pyridine modes could be an important aspect of Raman scattering of pyridine on conducting surfaces such as those studied in surface enhanced Raman scattering experiments.

  6. Role of ribose in the initial excited state structural dynamics of thymidine in water solution: a resonance Raman and density functional theory investigation.

    Science.gov (United States)

    Zhu, Xin-Ming; Wang, Hui-gang; Zheng, Xuming; Phillips, David Lee

    2008-12-11

    Resonance Raman spectra were obtained for thymidine and thymine with excitation wavelengths in resonance with the approximately 260 nm band absorption spectrum. The spectra indicate that the Franck-Condon (FC) region photodissociation dynamics of thymidine have multidimensional character with motion predominantly along the nominal C5=C6 stretch + C6-H bend nu17 (delta = 0.75, lambda = 468 cm(-1)), the nominal thymine ring stretch + C6-H bend + N1-C1, stretch nu29 (delta = 0.73, lambda = 363 cm(-1)), the nominal thymine ring stretch + C5-CH3/ N1-C1, stretch nu37 (delta = 0.69, lambda = 292 cm(-1)), and accompanied by the moderate and minor changes in the nu40, nu20 and nu23, nu55, nu60, nu61, nu63 modes. A preliminary resonance Raman intensity analysis was done, and these results for thymidine and thymine were compared to each other. The roles of ribose in the FC structure dynamics of thymidine were explored and the results were used to correlate to its lifetime constants tau1 and tau2 for two nonradiative decay channels. Spi/Sn conical intersection versus a distorted structure of Spi,min in the FC region was briefly discussed.

  7. Vibrational spectroscopy of the electronically excited state. 4. Nanosecond and picosecond time-resolved resonance Raman spectroscopy of carotenoid excited states

    Energy Technology Data Exchange (ETDEWEB)

    Dallinger, R.F.; Farquharson, S.; Woodruff, W.H.; Rodgers, M.A.J.

    1981-12-16

    Resonance Raman and electronic absorption spectra are reported for the S/sub 0/ and T/sub 1/ states of the carotenoids ..beta..-carotene, zeaxanthin, echinenone, canthaxanthin, dihydroxylycopene, astaxanthin, decapreno(C/sub 50/)-..beta..-carotene, ..beta..-apo-8'-carotenal, and ethyl ..beta..-apo-8'-carotenoate. The results reveal qualitatively similar ground-state spectra and similar frequency shifts in all observed resonance Raman modes between S/sub 0/ and T/sub 1/, regardless of carotenoid structure. Examinations of the relationship of the putative C--C and C==C frequencies in S/sub 0/ and T/sub 1/ reveals anomalous shifts to lower frequency in the ''single-bond'' mode upon electronic excitation. These shifts may be due to molecular distortions in the excited state which force changes in molecular motions comprising the observed modes. However, another possibility requiring no distortion is that the interaction (off-diagonal) force constants connecting the C--C and C==C modes change sign upon electronic excitation. This latter phenomenon may provide a unitary explanation for the ''anomalous'' frequency shifts in the C--C and C==C modes, both in the T/sub 1/ states of carotenoids and in the S/sub 1/ states of simpler polyenes, without postulating large, unpredicted structural changes upon excitation or general errors in existing vibrational or theoretical analyses. Resonance Raman and absorbance studies with 35-ps time resolution suggest that S/sub 1/ lifetime (of the /sup 1/B/sub u/ and/or the /sup 1/A/sub g/* states) of ..beta..-carotene in benzene is less than 1 ps.

  8. Water in the hydration shell of halide ions has significantly reduced Fermi resonance and moderately enhanced Raman cross section in the OH stretch regions.

    Science.gov (United States)

    Ahmed, Mohammed; Singh, Ajay K; Mondal, Jahur A; Sarkar, Sisir K

    2013-08-22

    Water in the presence of electrolytes plays an important role in biological and industrial processes. The properties of water, such as the intermolecular coupling, Fermi resonance (FR), hydrogen-bonding, and Raman cross section were investigated by measuring the Raman spectra in the OD and OH stretch regions in presence of alkali halides (NaX; X = F, Cl, Br, I). It is observed that the changes in spectral characteristics by the addition of NaX in D2O are similar to those obtained by the addition of H2O in D2O. The spectral width decreases significantly by the addition of NaX in D2O (H2O) than that in the isotopically diluted water. Quantitative estimation, on the basis of integrated Raman intensity, revealed that the relative Raman cross section, σ(H)/σ(b) (σ(H) and σ(b) are the average Raman cross section of water in the first hydration shell of X(-) and in bulk, respectively), in D2O and H2O is higher than those in the respective isotopically diluted water. These results suggest that water in the hydration shell has reduced FR and intermolecular coupling compared to those in bulk. In the isotopically diluted water, the relative Raman cross section increases with increase in size of the halide ions (σ(H)/σ(b) = 0.6, 1.1, 1.5, and 1.9 for F(-), Cl(-), Br(-), and I(-), respectively), which is assignable to the enhancement of Raman cross section by charge transfer from halide ions to the hydrating water. Nevertheless, the experimentally determined σ(H)/σ(b) is lower than the calculated values obtained on the basis of the energy of the charge transfer state of water. The weak enhancement of σ(H)/σ(b) signifies that the charge transfer transition in the hydration shell of halide ions causes little change in the OD (OH) bond lengths of hydrating water.

  9. Optimization of Fe3O4@Ag nanoshells in magnetic field-enriched surface-enhanced resonance Raman scattering for malaria diagnosis.

    Science.gov (United States)

    Yuen, Clement; Liu, Quan

    2013-11-07

    The great potential of magnetic field enriched surface enhanced resonance Raman spectroscopy (SERRS) for early malaria diagnosis has been demonstrated previously. This technique is able to detect β-hematin, which is equivalent to a malaria biomarker (hemozoin) in Raman features, at a concentration of 5 nM. In this study, we present the optimization of nanoparticles used in the magnetic field enriched SERRS by tuning the core size and shell thickness of nanoparticles with an iron oxide core and a silver shell (Fe3O4@Ag). The discrete dipole approximation (DDA) model was introduced to investigate the localized electromagnetic field distributions and extinction efficiencies of the aggregate of Fe3O4@Ag and β-hematin, in correlation with their magnetic field enriched SERRS performance. We find that the optimal core-shell size of Fe3O4@Ag leading to the effective aggregation of Fe3O4@Ag and β-hematin under an external magnetic field with superior extinction efficiencies is the key to realize highly augmented Raman signals in this strategy. Furthermore, it is noted that the optimized result differs from the case without the external magnetic field to that with the external magnetic field. Therefore, this work demonstrates experimentally and theoretically the potential of tuning the core-shell Fe3O4@Ag for achieving the efficient magnetic field-enriched SERRS detection of β-hematin for early malaria diagnosis.

  10. Predictive value of the surface-enhanced resonance Raman scattering-based MTT assay: a rapid and ultrasensitive method for cell viability in situ.

    Science.gov (United States)

    Mao, Zhu; Liu, Zhuo; Chen, Lei; Yang, Jin; Zhao, Bing; Jung, Young Mee; Wang, Xu; Zhao, Chun

    2013-08-06

    SERRS (surface-enhanced resonance Raman scattering) has been used to develop and optimize a novel and quantitative MTT assay for living cell viability. This highly sensitive method derives from two factors for formazan signal enhancing: the addition of Au nanoparticles and the resonance effect by 632.8 nm of excitation. The results show that the background elements, such as excessive MTT residues, serum, and the drug, did not interfere with the detection of formazan. Moreover, the detection limit of formazan is as low as 1 ng/mL. With the use of this method to quantify metabolically viable cells, dose-response curves of treated and untreated cells with the drug were constructed on the human lung cancer cell A549. The results also show that the Raman signal generated is dependent on the degree of activation of the cells. In comparison to the traditional method, the main advantages of this method are its rapidity (30 min), high-selectivity, high-precision, and cost-effectiveness (0.1 mg/mL MTT) without time-consuming steps and any modifying or labeling procedure. This work reports on an improved research tool that may help researchers apply this method for in situ cell assays.

  11. Resonance Raman Intensities Demonstrate that C5 Substituents Affect the Initial Excited-State Structural Dynamics of Uracil More than C6 Substituents.

    Science.gov (United States)

    Teimoory, Faranak; Loppnow, Glen R

    2016-05-04

    Resonance Raman derived initial excited-state structural dynamics provide insight into the photochemical mechanisms of pyrimidine nucleobases, in which the photochemistry appears to be dictated by the C5 and C6 substituents. The absorption and resonance Raman spectra and excitation profiles of 5,6-dideuterouracil were measured to further test this photochemical dependence on the C5 and C6 substituents. The resulting set of excited-state reorganization energies of the observed internal coordinates were calculated and compared to those of other 5- and 6-substituted uracils. The results show that the initial excited-state dynamics along the C5C6 stretch responds to changes in mass at C5 and C6 in the same manner but that the in-plane bends at C5 and C6 are more sensitive to substituents at the C5 position than at the C6 position. In addition, the presence of two deuterium substituents at C5 and C6 decreases the initial excited-state structural dynamics along these in-plane bends, in contrast to what is observed in the presence of two CH3 groups on C5 and C6. The results are discussed in the context of DNA nucleobase photochemistry.

  12. Excited state proton transfer dynamics of thioacetamide in S2(ππ*) state: resonance Raman spectroscopic and quantum mechanical calculations study.

    Science.gov (United States)

    Chen, Xiao; Zhao, Yanying; Zhang, Haibo; Xue, Jiadan; Zheng, Xuming

    2015-02-05

    The photophysics and photochemistry of thioacetamide (CH3CSNH2) after excitation to the S2 electronic state were investigated by using resonance Raman spectroscopy in conjunction with the complete active space self-consistent field (CASSCF) method and density functional theory (DFT) calculations. The A-band resonance Raman spectra in acetonitrile, methanol, and water were obtained at 299.1, 282.4, 266.0, 252.7, and 245.9 nm excitation wavelengths to probe the structural dynamics of thioacetamide in the S2 state. CASSCF calculations were done to determine the transition energies and structures of the lower-lying excited states, the conical intersection points CI(S2/S1) and CI(S1/S0), and intersystem crossing points. The structural dynamics of thioacetamide in the S2 state was revealed to be along eight Franck-Condon active vibrational modes ν15, ν11, ν14, ν10, ν8, ν12, ν18, and ν19, mostly in the CC/CS/CN stretches and the CNH8,9/CCH5,6,7/CCN/CCS in-plane bends as indicated by the corresponding normal mode descriptions. The S2 → S1 decay process via the S2/S1 conical intersection point as the major channel were excluded. The thione-thiol photoisomerization reaction mechanism of thioacetamide via the S2,FC → S'1,min excited state proton transfer (ESPT) reaction channel was proposed.

  13. Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: Resonance Raman and complete active space self-consistent field calculation study

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, Bing, E-mail: ouyangbing.zj@foxmail.com; Xue, Jia-Dan, E-mail: jenniexue@126.com; Zheng, Xuming, E-mail: zhengxuming126@126.com, E-mail: zxm@zstu.edu.cn, E-mail: fangwh@dnu.edu.cn [Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Fang, Wei-Hai, E-mail: zxm@zstu.edu.cn, E-mail: fangwh@dnu.edu.cn, E-mail: fangwh@dnu.edu.cn [Department of Chemistry, Beijing Normal University, Beijing 100875 (China)

    2014-05-21

    The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were very different. The conical intersection point CI(S{sub 2}/S{sub 1}) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S{sub 2}(A′) state: the radiative S{sub 2,min} → S{sub 0} transition and the nonradiative S{sub 2} → S{sub 1} internal conversion via CI(S{sub 2}/S{sub 1}). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S{sub 1}/T{sub 1}) in the excited state decay dynamics of PITC is evaluated.

  14. Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: resonance Raman and complete active space self-consistent field calculation study.

    Science.gov (United States)

    Ouyang, Bing; Xue, Jia-Dan; Zheng, Xuming; Fang, Wei-Hai

    2014-05-21

    The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S2(A'), S6(A'), and S7(A') excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S2(A'), S6(A'), and S7(A') excited states were very different. The conical intersection point CI(S2/S1) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S2(A') state: the radiative S(2,min) → S0 transition and the nonradiative S2 → S1 internal conversion via CI(S2/S1). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S1/T1) in the excited state decay dynamics of PITC is evaluated.

  15. Abnormal Raman spectral phenomenon of silicon nanowires

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Raman spectra of two one-dimensional silicon nanowire samples with different excitation wavelengths were measured and an abnormal phenomenon was discovered that the Raman spectral features change with the wavelengths of excitation. Closer analysis of the crystalline structure of samples and the changes in Raman spectral features showed that the abnormal behavior is the result of resonance Raman scattering selection effect.

  16. Rational Design of a Chalcogenopyrylium-Based Surface-Enhanced Resonance Raman Scattering-Nanoprobe with Attomolar Sensitivity

    Science.gov (United States)

    Wall, Matthew A.; Huang, Ruimin; Detty, Michael R.; Kircher, Moritz F.

    2015-01-01

    High sensitivity and specificity are two desirable features in biomedical imaging. Raman imaging has surfaced as a promising optical modality that offers both. Here, we report the design and synthesis of a group of near infrared absorbing 2-thienyl-substituted chalcogenopyrylium dyes tailored to have high affinity for gold. When adsorbed onto gold nanoparticles, these dyes produce biocompatible SERRS-nanoprobes with attomolar limits of detection amenable to ultrasensitive in vivo multiplexed tumor and disease marker detection. PMID:25800697

  17. Rational design of a chalcogenopyrylium-based surface-enhanced resonance Raman scattering nanoprobe with attomolar sensitivity

    Science.gov (United States)

    Harmsen, Stefan; Bedics, Matthew A.; Wall, Matthew A.; Huang, Ruimin; Detty, Michael R.; Kircher, Moritz F.

    2015-03-01

    High sensitivity and specificity are two desirable features in biomedical imaging. Raman imaging has surfaced as a promising optical modality that offers both. Here we report the design and synthesis of a group of near-infrared absorbing 2-thienyl-substituted chalcogenopyrylium dyes tailored to have high affinity for gold. When adsorbed onto gold nanoparticles, these dyes produce biocompatible SERRS nanoprobes with attomolar limits of detection amenable to ultrasensitive in vivo multiplexed tumour and disease marker detection.

  18. Protein dynamics in an intermediate state of myoglobin: optical absorption, resonance Raman spectroscopy, and x-ray structure analysis.

    OpenAIRE

    N. Engler; Ostermann, A; Gassmann, A.; Lamb, D C; Prusakov, V E; J. Schott; Schweitzer-Stenner, R; Parak, F. G.

    2000-01-01

    A metastable state of myoglobin is produced by reduction of metmyoglobin at low temperatures. This is done either by irradiation with x-rays at 80 K or by electron transfer from photoexcited tris(2, 2'-bipyridine)-ruthenium(II) at 20 K. At temperatures above 150 K, the conformational transition toward the equilibrium deoxymyoglobin is observed. X-ray crystallography, Raman spectroscopy, and temperature-dependent optical absorption spectroscopy show that the metastable state has a six-ligated ...

  19. The effect of the Fermi resonance on the Raman scattering cross sections of the Fermi doublet ν1 and 2ν2 of liquid carbon disulfide in benzene.

    Science.gov (United States)

    Li, Dong-Fei; Gao, Shu-Qin; Sun, Cheng-Lin; Jiang, Xiu-Lan; Li, Zuo-Wei

    2012-04-01

    The effect of the Fermi resonance (FR) on the Raman scattering cross sections (RSCSs) of the Fermi doublet ν1, 2ν2 of liquid CS2 in C6H6 using the method of changing the volume concentration of the solution is investigated. We have calculated the RSCSs of the Fermi doublet ν1, 2ν2 using Onsager's theory with the 992 cm(-1) Raman line of C6H6 as the internal standard. The result shows that the RSCS of the ν1 line decreases with decreasing the volume concentration of CS2, while that of the 2ν2 line unexpectedly increases. With decreasing the volume concentration of CS2, two main effects of the solvent effect (SE) and the FR in binary solution that can make the ν1, 2ν2 RSCSs change: the SE, as calculated, reduces both the ν1 and 2ν2 RSCSs; the FR plays a significant role in reducing the ν1 RSCS and enhancing the 2ν2 RSCS. In comparison with our previous investigation [J. Raman Spectrosc. 41 (2010) 776-779], it was found that the stronger the FR is, the more the RSCS of the ν1 decreases and the 2ν2 increases. Thus, we proposed that the result can be best explained by taking into account the effect of the FR on the RSCSs of the Fermi doublet. In addition, this paper also gives an explanation to the experimental results deviating from the theoretical results of the scattering coefficients of CS2 in solvent C6H6 as mentioned in Fini's paper.

  20. Structure and reactivity of thiazolium azo dyes: UV-visible, resonance Raman, NMR, and computational studies of the reaction mechanism in alkaline solution.

    Science.gov (United States)

    Abbott, Laurence C; Batchelor, Stephen N; Moore, John N

    2013-03-07

    UV-visible absorption, resonance Raman, and (1)H NMR spectroscopy, allied with density functional theory (DFT) calculations, have been used to study the structure, bonding, and alkaline hydrolysis mechanism of the cationic thiazloium azo dye, 2-[2-[4-(diethylamino)phenyl]diazenyl]-3-methyl-thiazolium (1a), along with a series of six related dyes with different 4-dialkylamino groups and/or other phenyl ring substituents (2a-c, 3a-c) and the related isothiazolium azo dye, 5-[2-[4-(dimethylamino)phenyl]diazenyl]-2-methyl-isothiazolium (4). These diazahemicyanine dyes are calculated to have a similar low-energy structure that is cis, trans at the (iso)thiazolium-azo group, and for which the calculated Raman spectra provide a good match with the experimental data; the calculations on these structures are used to assign and discuss the transitions giving rise to the experimental spectra, and to consider the bonding and its variation between the dyes. UV-visible, Raman, and NMR spectra recorded from minutes to several weeks after raising the pH of an aqueous solution of 1a to ca. 11.5 show that the dominant initial step in the reaction is loss of diethylamine to produce a quinonimine (ca. hours), with subsequent reactions occurring on longer time scales (ca. days to weeks); kinetic analyses give a rate constant of 2.6 × 10(-2) dm(3) mol(-1) s(-1) for reaction of 1a with OH(-). UV-visible spectra recorded on raising the pH of the other dyes in solution show similar changes that are attributed to the same general reaction mechanism, but with different rate constants for which the dependence on structure is discussed.

  1. Resonance Raman and absorption spectroscopy of the lowest triplet state of 1,3,5-hexatriene and deuteriated derivatives at 183 K : molecular structure in the T1 state

    NARCIS (Netherlands)

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

    1991-01-01

    Time-resolved resonance Raman (RR) spectra of the lowest excited triplet state T1 of (E)-1,3,5-hexatriene, (E)-3-deuterio-1,3,5-hexatriene, and (E)-1,1-dideuterio-1,3,5-hexatriene are obtained at 183 K. The T1 potential energy surface (PES), determining energy minima, equilibrium geometries, frequen

  2. Absorption and resonance Raman study of the {sup 2}B{sub 1}(X)-{sup 2}A{sub 2}(A) transition of chlorine dioxide in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Esposito, A.P.; Stedl, T.; Jonsson, H.; Reid, P.J. [Univ. of Washington, Seattle, WA (United States). Dept. of Chemistry; Peterson, K.A. [Washington State Univ., Pullman, WA (United States). Dept. of Chemistry

    1999-03-25

    The photochemical reaction dynamics of chlorine dioxide (OClO) are investigated using absorption and resonance Raman spectroscopy. The first Raman spectra of gaseous OClO obtained directly on resonance with the {sup 2}B{sub 1}-{sup 2}A{sub 2} electronic transition are reported. Significant scattering intensity is observed for all vibrational degrees of freedom (the symmetric stretch, bend, and asymmetric stretch), demonstrating that structural evolution occurs along all three normal coordinates following photoexcitation. The experimentally measured absorption and resonance Raman intensities are compared to the intensities predicted using both empirical and ab initio models for the optically active {sup 2}A{sub 2} surface. Comparison of the experimental and theoretical absorption spectra demonstrates that the frequencies and intensities of transitions involving the asymmetric stretch are well reproduced by the empirical model characterized by a double-minimum along the asymmetric stretch. However, the ab initio model is also found to reproduce a subset of the experimental intensities. In addition, the extremely large resonance Raman intensity of the asymmetric stretch overtone transition is predicted by both models. The results presented here taken in combination with the model for the {sup 2}A{sub 2} surface in condensed environments suggest that the phase-dependent photochemical reactivity of OClO is due to environment-dependent excited-state structural evolution along the asymmetric stretch coordinate.

  3. Non-invasive determination of the CO contents in tuna fish using polarization resolved resonance Raman scattering and/or Rayleigh spectroscopy

    DEFF Research Database (Denmark)

    Hassing, Søren

    2016-01-01

    Carbon monoxide (CO) is used for Modified Atmosphere Packaging of fresh fish and meat. CO is added because it binds to the Myoglobin of the muscle tissue with high affinity resulting in a bright, cherry-red colored carboxy-Myoglobin complex. The product will because of the red color appear to be ...... with polarization resolved resonance Raman spectra of these molecules, can form the basis of the development of a fast and non-invasive method for the screening of the presence of CO in tuna fish and meat.......Carbon monoxide (CO) is used for Modified Atmosphere Packaging of fresh fish and meat. CO is added because it binds to the Myoglobin of the muscle tissue with high affinity resulting in a bright, cherry-red colored carboxy-Myoglobin complex. The product will because of the red color appear...

  4. Fourier Transform Infrared (FTIR) Spectroscopy, Ultraviolet Resonance Raman (UVRR) Spectroscopy, and Atomic Force Microscopy (AFM) for Study of the Kinetics of Formation and Structural Characterization of Tau Fibrils.

    Science.gov (United States)

    Ramachandran, Gayathri

    2017-01-01

    Kinetic studies of tau fibril formation in vitro most commonly employ spectroscopic probes such as thioflavinT fluorescence and laser light scattering or negative stain transmission electron microscopy. Here, I describe the use of Fourier transform infrared (FTIR) spectroscopy, ultraviolet resonance Raman (UVRR) spectroscopy, and atomic force microscopy (AFM) as complementary probes for studies of tau aggregation. The sensitivity of vibrational spectroscopic techniques (FTIR and UVRR) to secondary structure content allows for measurement of conformational changes that occur when the intrinsically disordered protein tau transforms into cross-β-core containing fibrils. AFM imaging serves as a gentle probe of structures populated over the time course of tau fibrillization. Together, these assays help further elucidate the structural and mechanistic complexity inherent in tau fibril formation.

  5. Resonant excitation of Mn local vibrational modes in the higher order Raman spectra of nanocrystalline Ga{sub 1-x}Mn{sub x}N films

    Energy Technology Data Exchange (ETDEWEB)

    Dias da Silva, J H; Leite, D M G [Department of Physics, Advanced Materials Group, UNESP-Sao Paulo State University, Bauru SP, 17033-360 (Brazil); Zanatta, A R [Instituto de Fisica de Sao Carlos, USP, Sao Carlos 13560-250 (Brazil)], E-mail: jhdsilva@fc.unesp.br, E-mail: dmgleite@fc.unesp.br, E-mail: zanatta@ifsc.usp.br

    2008-06-25

    The effect of manganese on the vibrational properties of Ga{sub 1-x}Mn{sub x}N (0{<=}x{<=}0.18) films has been investigated by Raman scattering using 488.0 and 632.8 nm photon excitations. The first-order transverse and longitudinal optical GaN vibrational bands were observed in the whole composition range using both excitations, while the corresponding overtones, as well as a prominent peak located in 1238 cm{sup -1} (153.5 meV) were only observed in the Mn-containing films under 488.0 nm excitation. We propose that the peak observed at 1238 cm{sup -1} is due to resonant Mn local vibrational modes, the excitation process being related to electronic transitions involving the Mn acceptor band. (fast track communication)

  6. Towards combined electrochemistry and surface-enhanced resonance Raman of heme proteins: Improvement of diffusion electrochemistry of cytochrome c at silver electrodes chemically modified with 4-mercaptopyridine.

    Science.gov (United States)

    Millo, Diego; Ranieri, Antonio; Koot, Wynanda; Gooijer, Cees; van der Zwan, Gert

    2006-08-01

    To date, a successful combination of surface-enhanced resonance Raman spectroscopy (SERRS) and electrochemistry to study heme proteins is inhibited by the problems raised by the prerequisite to use silver as electrode metal. This paper indicates an approach to overcome these problems. It describes a quick and reproducible procedure to prepare silver electrodes chemically modified with 4-mercaptopyridine suitable to perform diffusion electrochemistry of cytochrome c (cyt c). The method involves the employment of a mechanical and a chemical treatment and avoids the use of alumina slurries and any electrochemical pretreatment. Cyclic voltammetry (CV) was used to test the electrochemical response of cyt c, and the CV signals were found identical with those obtained on gold electrodes under the same experimental conditions. Compared to previous literature, a significant improvement of the CV signal of cyt c at silver electrodes was achieved. Preliminary results show that this treatment can be also successfully employed for the preparation of SERRS-active electrodes.

  7. Effective approach to strengthen plasmon resonance localized on top surfaces of Ag nanoparticles and application in surface-enhanced Raman spectroscopy

    Science.gov (United States)

    Zhan, Zhibing; Xu, Rui; Zheng, Xianzheng; Fu, Qun; Wu, Minghong; Lei, Yong

    2016-11-01

    The spatial distribution of localized surface plasmon resonance (LSPR) plays a key role in many plasmonic applications. Based on the thermal stability of alumina templates, this work reports a novel approach to manipulate the distribution of LSPR and exhibits its significance for an important plasmonic application, the surface-enhanced Raman spectroscopy (SERS). A suitable thermal annealing sharpens the edges in top surfaces (far from the substrates) of Ag nanoparticles, which significantly strengthens the distal mode (DM) with the LSPR excited on the top surfaces. Because the top surface is the major place to adsorb probe molecules, this manipulation greatly improves the detection sensitivity of SERS. Our research provides a new way to improve the sensitivity of SERS, which also indicates that great care has to be taken on special LSPR mode which is largely responsible for a certain plasmonic application (e.g., the DM for SERS although it is not the major mode).

  8. Real-time measurements of the redox states of c-type cytochromes in electroactive biofilms: a confocal resonance Raman Microscopy study.

    Directory of Open Access Journals (Sweden)

    Bernardino Virdis

    Full Text Available Confocal Resonance Raman Microscopy (CRRM was used to probe variations of redox state of c-type cytochromes embedded in living mixed-culture electroactive biofilms exposed to different electrode polarizations, under potentiostatic and potentiodynamic conditions. In the absence of the metabolic substrate acetate, the redox state of cytochromes followed the application of reducing and oxidizing electrode potentials. Real-time monitoring of the redox state of cytochromes during cyclic voltammetry (CV in a potential window where cytochromes reduction occurs, evidenced a measurable time delay between the oxidation of redox cofactors probed by CV at the electrode interface, and oxidation of distal cytochromes probed by CRRM. This delay was used to tentatively estimate the diffusivity of electrons through the biofilm. In the presence of acetate, the resonance Raman spectra of young (10 days, j = 208 ± 49 µA cm(-2 and mature (57 days, j = 267 ± 73 µA cm(-2 biofilms show that cytochromes remained oxidized homogeneously even at layers as far as 70 µm from the electrode, implying the existence of slow metabolic kinetics that do not result in the formation of a redox gradient inside the biofilm during anode respiration. However, old biofilms (80 days, j = 190 ± 37 µA cm(-2 with thickness above 100 µm were characterized by reduced catalytic activity compared to the previous developing stages. The cytochromes in these biofilm were mainly in the reduced redox state, showing that only aged mixed-culture biofilms accumulate electrons during anode respiration. These results differ substantially from recent observations in pure Geobacter sulfurreducens electroactive biofilms, in which accumulation of reduced cytochromes is already observed in thinner biofilms, thus suggesting different bottlenecks in current production for mixed-culture and G. sulfurreducens biofilms.

  9. Control of surface plasmon resonance in out-diffused silver nanoislands for surface-enhanced Raman scattering

    Science.gov (United States)

    Piliugina, E. S.; Heisler, F.; Chervinskii, S. D.; Samusev, A. K.; Lipovskii, A. A.

    2015-12-01

    We present the studies of self-assembled silver nanoislands on the surface of silver ion-exchanged glasses. The nanoislands were formed by out-diffusion of reduced silver atoms from the bulk of the glass to its surface. Control of silver ions distribution in the glass by thermal poling after the ion exchange allowed formation of relatively big, up to 250 nm, isolated silver nanoislands while without the poling an ensemble of silver nanoislands with average size from several to tens of nanometers with random size distribution was formed. The nanoislands were characterized using atomic force microscopy and spectral measurements. We used optical absorption spectroscopy for “random” nanoislands and dark field scattering spectroscopy for isolated ones, corresponding spectra showed peaks in the vicinity of 450 nm and 600 nm, respectively. The “random” nanoislands significantly enhanced Raman scattering from Rhodamine 6G, also the modification of Raman signal from deposited on the surface of the samples bacteriorhodopsin in purple membranes was registered.

  10. Separation of multiple-quantum signals with different orders along with frequency axis in Raman magnetic resonance spectroscopy in heteronuclear systems

    Institute of Scientific and Technical Information of China (English)

    缪希茄; 卢广; 叶朝辉

    1997-01-01

    One-dimensional multiple-quantum spectroscopy with Raman magnetic resonance (RMR) in het-eronuclear systems was described by the product operator formalism in detail.The effects of the field strength and the frequency offset of the irradiation introduced during the detection period on the intensities and the resonant frequencies of the multiple-quantum signals in RMR spectra were investigated extensively by this product operator formalism.The results predicted by the formalism showed that the multiple-quantum signals in RMR spectroscopy had a higher sensitivity when a smaller frequency offset of irradiation field was employed.However,this situation would complicate the assignment and the separation of the multiple-quantum signals in different orders along the frequency axis in RMR spectra.On the other hand,a larger strength of the irradiation field would result in decoupling and therefore would obscure the detection of the multiple-quantum signals.In the meantime,a much weaker RF field might greatly dec

  11. Redox induced protonation of heme propionates in cytochrome c oxidase: Insights from surface enhanced resonance Raman spectroscopy and QM/MM calculations.

    Science.gov (United States)

    Sezer, Murat; Woelke, Anna-Lena; Knapp, Ernst Walter; Schlesinger, Ramona; Mroginski, Maria Andrea; Weidinger, Inez M

    2017-02-01

    Understanding the coupling between heme reduction and proton translocation in cytochrome c oxidase (CcO) is still an open problem. The propionic acids of heme a3 have been proposed to act as a proton loading site (PLS) in the proton pumping pathway, yet this proposal could not be verified by experimental data so far. We have set up an experiment where the redox states of the two hemes in CcO can be controlled via external electrical potential. Surface enhanced resonance Raman (SERR) spectroscopy was applied to simultaneously monitor the redox state of the hemes and the protonation state of the heme propionates. Simulated spectra based on QM/MM calculations were used to assign the resonant enhanced CH2 twisting modes of the propionates to the protonation state of the individual heme a and heme a3 propionates respectively. The comparison between calculated and measured H2OD2O difference spectra allowed a sound band assignment. In the fully reduced enzyme at least three of the four heme propionates were found to be protonated whereas in the presence of a reduced heme a and an oxidized heme a3 only protonation of one heme a3 propionates was observed. Our data supports the postulated scenario where the heme a3 propionates are involved in the proton pathway.

  12. In Vitro Polarized Resonance Raman Study of N719 and N719-TBP in Dye Sensitized Solar Cells

    DEFF Research Database (Denmark)

    Hassing, Søren; Jernshøj, Kit Drescher; Nguyen, Phuong Tuyet;

    2016-01-01

    the adsorption of the dye on TiO2 can be obtained. Furthermore it is found that the polarization fluorescence anisotropy is very different for adsorbed and non-adsorbed dye molecules. This information is automatically obtained when processing the Raman data. The conclusion is that if the polarization properties......Abstract: The working efficiency of dye-sensitized solar cells (DSCs) depends on the long-term stability of the dye itself and on the microscopic structure of the dye-semiconductor interface. Previous experimental studies of DSCs based on ruthenium dye with bipyridine ligands (N719) adsorbed...... on N719/TiO2 – DSCs that by combining an analysis of the wave number dependent polarization of these modes with the small shifts observed in the visible absorption spectra of adsorbed, non-adsorbed molecules and degradation products new and more reliable information about dye stability and about...

  13. Passively mode locked Raman laser

    CERN Document Server

    Liang, W; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L

    2010-01-01

    We report on the observation of a novel mode locked optical comb generated at the Raman offset (Raman comb) in an optically pumped crystalline whispering gallery mode resonator. Mode locking is confirmed via measurement of the radio-frequency beat note produced by the optical comb on a fast photodiode. Neither the conventional Kerr comb nor hyper-parametric oscillation is observed when the Raman comb is present.

  14. Resonances

    DEFF Research Database (Denmark)

    an impetus or drive to that account: change, innovation, rupture, or discontinuity. Resonances: Historical Essays on Continuity and Change explores the historiographical question of the modes of interrelation between these motifs in historical narratives. The essays in the collection attempt to realize...... theoretical consciousness through historical narrative ‘in practice’, by discussing selected historical topics from Western cultural history, within the disciplines of history, literature, visual arts, musicology, archaeology, philosophy, and theology. The title Resonances indicates the overall perspective...

  15. Distinct structures and environments for the three hemes of the cytochrome bc1 complex from Rhodospirillum rubrum. A resonance Raman study using B-band excitations.

    Science.gov (United States)

    Le Moigne, C; Schoepp, B; Othman, S; Verméglio, A; Desbois, A

    1999-01-19

    The B-band excited resonance Raman (RR) spectra (100-1700 cm-1) of the bacterial cytochrome bc1 complex purified from Rhodospirillum rubrum are reported. Four redox states, i.e., the persulfate-oxidized, "as prepared", and ascorbate- and dithionite-reduced states of the complex, were investigated with the laser excitations at 406.7, 413.1, and 441.6 nm. Following the different absorption properties of the b- and c-type hemes and the different resonance enhancements of the vibrational modes of oxidized and reduced hemes, RR contributions from the b- and c-type hemes were characterized. For the nu2, nu10, and nu8 porphyrin vibrational modes, individual contributions of hemes c1, bH, and bL were determined. The data show that the macrocycle conformation of the three hemes of the cytochrome bc1 complex is different. In particular, the frequencies assigned to ferrous heme bL (1580, 1610, and 352 cm-1, respectively) reveal that its porphyrin is more strongly distorted than that of ferrous heme bH (1584, 1614, and 344 cm-1, respectively). The frequencies of the nu11 modes (1543, 1536, and 1526 cm-1 for ferrous heme c1, heme bH, and heme bL, respectively) confirm that the axial histidylimidazole ligands of heme bL have a marked anionic character. Strong differences in the peripheral interactions of the three hemes with the proteins were also detected through the frequency differences of the nu5, nu13, nu14, and nu42 modes. Considering that hemes bH and bL are inserted into a four-helice bundle, the RR data are interpreted in the frame of a strong protein constraint on heme bL.

  16. Transient resonance Raman spectroscopy and density functional theory investigation of iso-CHBr 2Cl and iso-CCl 3Br photoproducts produced following ultraviolet excitation of CHBr 2Cl and CCl 3Br

    OpenAIRE

    Zheng, X; Lee, CW; Li, YL; Fang, WH; Phillips, DL

    2001-01-01

    Two polyhalomethanes that contain bromine and chlorine atoms (CHBr 2Cl and CCl 2Br) were studied. Transient resonance Raman spectra were obtained for the photoproducts produced after ultraviolet excitation of CHBr 2Cl and CCl 3Br in room temperature solutions and density functional theory calculations for species proposed to be products of the photodissociation reactions in the solution phase. It was found that the iso-CHBrCl-Br and iso-CHClBr-Br species are formed following ultraviolet excit...

  17. Anti-Stokes Resonance Raman of Ir Illuminated Dendrimer Iron (III)-Porphyrins%红外辐照下树枝状铁(iii)卟啉的反斯托克斯共振拉曼

    Institute of Scientific and Technical Information of China (English)

    MO Yu-jun; D.L.Jiang; M.Uymura; T.Aida; T.Kitagawa

    2005-01-01

    The benzene dendrimers of Fe(Ⅲ) tetraphenyl porphyrin chloride[LnFe(Ⅲ)TPPCl] with n = 3, 4, and 5 (n: number of layers) have been synthesized and the IR illumination effects at benzene bands were examined with anti- Stokes resonance Raman speetroseopy for their dioxane solutions.Boltzman temperatures were determined from the Stokes to anti - Stokes intensity ratio for the speetra excited at 413.1 nm in the presence and absence of IR illumination.

  18. Ultraviolet Resonance Raman spectroscopy used to study formulations of salmon calcitonin, a starch-peptide conjugate and TGF-β3.

    Science.gov (United States)

    Patois, E; Larmour, I A; Bell, S E J; Palais, C; Capelle, M A H; Gurny, R; Arvinte, T

    2012-06-01

    Ultraviolet Resonance Raman (UVRR) spectroscopy with excitation at 244 nm was investigated here as a possible useful tool for fast characterization of biopharmaceuticals. Studies were performed on three protein drugs: salmon calcitonin (sCT), starch-peptide conjugate, and transforming growth factor-β3 (TGF-β3) adsorbed onto solid granules of tricalcium phosphate (TCP). Secondary structure of sCT was investigated for solutions of 0.5mg/mL up to 200mg/mL, regardless of the turbidity or aggregation states. An increase in β-sheet content was detected when sCT solutions aggregated. UVRR spectroscopy also detected a small amount of residual organic solvent in a starch-peptide conjugate solution containing only 40 μg/mL of peptide. UVRR spectroscopy was then used to characterize a protein, TGF-β3, adsorbed onto solid granules of TCP at 50 and 250 μg/cm(3). This study shows that UVRR is suitable to characterize the protein formulations in a broad range of concentrations, in liquid, aggregated, and solid states.

  19. Resonance Raman spectroscopy of chemically modified and isotopically labelled purple membranes: I. A critical examination of the carbon-nitrogen vibrational modes

    Energy Technology Data Exchange (ETDEWEB)

    Ehrenberg, B. (Cornell Univ., Ithaca, NY); Lemley, A.T.; Lewis, A.; Zastrow, M.V.; Crespi, H.L.

    1980-01-01

    Resonance Raman spectra of bacteriorhodopsin are compared to the spectra of this protein modified in the following ways: (1) selective deuteration at the C-15 carbon atom of retinal, (2) full deuteration of the retinal, (3) the addition of a conjugated double bond in the ..beta..-ionone ring (3-dehydroretinal), (4) full deuteration of the protein and lipid components, (5) /sup 15/N enrichment of the entire membrane and (6) deuteration of the entire membrane. A detailed comparison of the /sup 15/N-enriched membrane and naturally occurring purple membrane from 800 cm/sup -1/ to 1700 cm/sup -1/ reveals that /sup 15/N enrichment affects the frequency of only two vibrational modes. These occur at 1642 cm/sup -1/ and 1620 cm/sup -1/ in naturally occurring purple membrane and at 1628 cm/sup -1/ and 1615 cm/sup -1/ in the /sup 15/N-enriched samples. Therefore, this pair of bands reflects the states of protonation of the Schiff base.

  20. Acquisition of pro-oxidant activity of fALS-linked SOD1 mutants as revealed using circular dichroism and UV-resonance Raman spectroscopy

    Science.gov (United States)

    Fujimaki, Nobuhiro; Nishiya, Ken; Miura, Takashi; Nakabayashi, Takakazu

    2016-11-01

    The acquisition of pro-oxidant activity of the mutated form of human Cu, Zn-superoxide dismutase (SOD1) has been investigated to clarify the relationship between mutations in SOD1 and the pathogenesis of amyotrophic lateral sclerosis (ALS). Ala4 → Val (A4V) and Gly93 → Ala (G93A) mutants, which are representative ALS-linked SOD1 mutants, have been found to exhibit both the denaturation and the gain of pro-oxidant activity after incubation in the apo-form at a physiological condition of 37 °C and pH 7.4 and the rebinding of Cu2+. These characteristics are similar to those previously reported for the His43 → Arg (H43R) mutant. UV-resonance Raman spectra indicated that the coordination structure of the Cu-binding site catalyzing the oxidation reaction is the same among the denatured A4V, G93A, and H43R. Since wild-type SOD1 does not exhibit the denaturation in its apo-form at 37 °C and pH 7.4, the instability of the protein structure due to mutation can be considered as a significant factor that induces the denaturation and the subsequent pro-oxidant activity.

  1. Comparison of simplified sum-over-state expressions to calculate resonance Raman intensities including Franck-Condon and Herzberg-Teller effects

    Science.gov (United States)

    Guthmuller, Julien

    2016-02-01

    Sum-over-state (SOS) expressions to simulate absorption spectroscopy and resonance Raman (RR) scattering including Franck-Condon (FC) and Herzberg-Teller (HT) effects are described. Starting from the general SOS method, several simplified SOS formulae are derived. In particular, within the so-called independent mode displaced harmonic oscillator model, it is shown that including the vibronic structure in the absorption and RR spectra only requires the calculation of FC overlap integrals of the type , where g, e, and v stand for the electronic ground state, excited state, and vibrational quantum number, respectively. Additionally, an approximation of the latter approach is introduced, referred as the simplified Φe method, in which the FC factors are neglected. This method is advantageous from the computational point of view and it is demonstrated that it reproduces the main characteristics of the more involved approaches. The merits and drawbacks of the different methods are discussed by applying them to the prototypical compound of Rhodamine 6G. Overall, this work intends to unravel and clarify some differences in the SOS theories of RR scattering.

  2. Observation of second-order hyper-Raman generation in LiNbO3 whispering-gallery mode disk resonators

    CERN Document Server

    Simons, Matt T

    2011-01-01

    In this manuscript we report experimental demonstration of nonlinear frequency conversion at several optical frequencies in a whispering-gallery mode resonator (WGMR). Due to the enhancement of nonlinear interactions inside a WGMR, interaction of a 1064 nm pump field with a LiNbO3 disk produced a weak, but measurable non-phase matched 532 nm second harmonic field at room temperature (>100C below the phase-matching temperature), for pump powers of a few tens of mW. For higher pump powers, we observed the generation of four additional fields at 545 nm, 559 nm, 573 nm, and 587 nm. The relative spectral shift between two consecutive fields corresponds to a 455 cm^-1 vibrational mode in LiNbO3 crystal. Our preliminary analysis indicates that these fields are the result of a multi-phonon hyper-Raman scattering, in which two photons of the pump field are converted into one photon of a higher-frequency field and one or several optical phonons.

  3. Observation of second-order hyper-Raman generation in LiNbO3 whispering-gallery mode disk resonators.

    Science.gov (United States)

    Simons, Matt T; Novikova, Irina

    2011-08-15

    In this Letter we report experimental demonstration of nonlinear frequency conversion at several optical frequencies in a whispering-gallery mode resonator (WGMR). Because of the enhancement of nonlinear interactions inside a WGMR, interaction of a 1064 nm pump field with a LiNbO(3) disk produced a weak but measurable non-phase-matched 532 nm second-harmonic field at room temperature (>100 °C below the phase-matching temperature) for pump powers of a few tens of milliwatts. For higher pump powers, we observed the generation of four additional fields at 545, 559, 573, and 587 nm. The relative spectral shift between two consecutive fields corresponds to a 455 cm(-1) vibrational mode in LiNbO(3) crystal. Our preliminary analysis indicates that these fields are the result of a multiphonon hyper-Raman scattering in which two photons of the pump field are converted into one photon of a higher-frequency field and one or several optical phonons.

  4. Au-Ag-Au double shell nanoparticles-based localized surface plasmon resonance and surface-enhanced Raman scattering biosensor for sensitive detection of 2-mercapto-1-methylimidazole.

    Science.gov (United States)

    Liao, Xue; Chen, Yanhua; Qin, Meihong; Chen, Yang; Yang, Lei; Zhang, Hanqi; Tian, Yuan

    2013-12-15

    In this paper, Au-Ag-Au double shell nanoparticles were prepared based on the reduction of the metal salts HAuCl4 and AgNO3 at the surface of seed particles. Due to the synergistic effect between Au and Ag, the hybrid nanoparticles are particularly stable and show excellent performances on the detection of 2-mercapto-1-methylimidazole (methimazole). The binding of target molecule at the surface of Au-Ag-Au double shell nanoparticles was demonstrated based on both localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS) spectra. The LSPR intensity is directly proportional to the methimazole concentration in the range of 0.10-3.00×10(-7) mol L(-1). The SERS spectrum can be applied in identification of methimazole molecule. The LSPR coupled with SERS based on the Au-Ag-Au double shell nanoparticles would be very attractive for the quantitative determination and qualitative analysis of the analytes in medicines.

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

    Science.gov (United States)

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

    2016-08-18

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

  6. Coupled electron-nuclear dynamics in resonant 1 σ →2 π x-ray Raman scattering of CO molecules

    Science.gov (United States)

    Couto, Rafael C.; Guarise, Marco; Nicolaou, Alessandro; Jaouen, Nicolas; Chiuzbǎian, Gheorghe S.; Lüning, Jan; Ekholm, Victor; Rubensson, Jan-Erik; Sâthe, Conny; Hennies, Franz; Guimarães, Freddy F.; Ågren, Hans; Gel'mukhanov, Faris; Journel, Loïc; Simon, Marc; Kimberg, Victor

    2016-03-01

    We present a detailed experimental-theoretical analysis of O K -edge resonant 1 σ -2 π inelastic x-ray scattering (RIXS) from carbon monoxide with unprecedented energy resolution. We employ high-level ab initio calculations to compute the potential energy curves of the states involved in the RIXS process and simulate the measured RIXS spectra using the wave-packet-propagation formalism, including Coulomb coupling in the final-state manifold. The theoretical analysis allows us to explain all the key features of the experimental spectra, including some that were not seen before. First, we clearly show the interference effect between different RIXS channels corresponding to the transition via orthogonal Π1x and Π1y core-excited states of CO. Second, the RIXS region of 13 eV energy loss presents a triple structure, revealed only by the high-resolution measurement. In previous studies, this region was attributed solely to a valence state. Here we show a strong Coulomb mixing of the Rydberg and valence final states, which opens the forbidden RIXS channels to the "dark" final Rydberg states and drastically changes the RIXS profile. Third, using a combination of high-resolution experiment and high-level theory, we improve the |4 σ-12 π1> final-state potential-energy curve by fitting its bottom part with the experiment. Also, the coupling constants between Rydberg and valence states were refined via comparison with the experiment. Our results illustrate the large potential of the RIXS technique for advanced studies of highly excited states of neutral molecules.

  7. The effect of an anti-hydrogen bond on Fermi resonance:A Raman spectroscopic study of the Fermi doublet v1-v12 of liquid pyridine

    Institute of Scientific and Technical Information of China (English)

    Li Dong-Fei; Gao Shu-Qin; Sun Cheng-Lin; Li Zuo-Wei

    2012-01-01

    The effects of an anti-hydrogen bond on the v1-v12 Fermi resonance (FR) of pyridine are experimentally investigated by using Raman scattering spectroscopy.Three systems,pyridine/water,pyridine/formamide,and pyridine/carbon tetrachloride,provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex.Water forms a stronger anti-hydrogen bond with pyridine than with formamide,and in the case of adding non-polar solvent carbon tetrachloride,which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine,the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce.The dilution studies are performed on the three systems.Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode v1 and triangle mode v12 of pyridine at different volume concentrations,which are calculated according to the Bertran equations,in three systems,we find that the solution with the strongest anti-hydrogen bond,water,shows the fastest change in thev1-v12 Fermi coupling coefficient W with the volume concentration varying,followed by the formamide and carbon tetrachloride solutions.These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the v1-v12 FR of pyridine.According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory,a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the v1 - v12 FR of pyridine is given.

  8. Structure of enzyme-bound substrates: resonance Raman and kinetic evidence for differential enzyme-substrate contacts in N-(Pentafluoro-benzoyl)glycine dithioacyl and thioacyl papain

    Science.gov (United States)

    Lee, H.; Angus, R. H.; Storer, A. C.; Carey, P. R.

    1989-12-01

    Resonance Raman (RR) spectroscopy is used to probe the structure of the substrate in the substrate-enzyme complex N-pentafluorobenzoyl) glycine (dithioacyl) papain (C 6F 5C(=O) NHCH 2C(=S)S-papain). This system was chosen since the high electron withdrawing capacity of the C 6F 5 group markedly affects electron density of the -NH- moiety which, in turn, is known to change catalytic activity. The RR spectrum of the enzyme-substrate complex is interpreted by reference to the model compound N-(pentafluorobenzoyl) glycine ethyl dithioester (C 6F 5(CO))NHCH 2C(=S)SC 2H 5. The RR spectra of this compound in aqueous or organic solvents can be understood in terms of the known conformational states of N-acylglycine dithioesters. Comparison of model with enzyme-substrate RR spectra shows that the substrate is binding in the active site in a conformer known as conformer B characterized by a small-NHCH 2CS(thiol) torsional angle and close N-to-S (thiol) contact. Kinetic rate-structure correlations are developed involving k3, the rate constant for deacylation, and the strength of the N-to-S (thiol) interaction. N-(Pentafluorobenzoyl) glycine dithioacyl papain fits the rate-structure correlation whereas the corresponding pentafluorobenzoyl glycine thiol intermediate does not. It is proposed that the difference in the size of the CS compared to the CO group brings about a small change in the dithioacyl papain compared to the thiolacyl papain conformation such that enzyme-substrate contacts involving ortho and meta F atoms in the thiol acyl enzyme case are weakened or removed in the case of the dithioacyl papain.

  9. 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.

  10. Spectroscopic studies of thiatri-, penta- and heptamethine cyanine dyes II. Infrared and resonance Raman spectra of thiatri-, penta- and heptamethine cyanine dyes

    Science.gov (United States)

    Fujimoto, Yasuhiko; Katayama, Norihisa; Ozaki, Yukihiro; Yasui, Shigeo; Iriyama, Keiji

    1992-11-01

    Infrared (IR) and resonance Raman (RR) spectra of thiatri-, penta- and heptamethine cyanine dyes in the solid state and in solution have been measured. Most of the intense bands observed in the 1600-1100 cm -1 region of the RR spectra may be assigned to totally symmetric stretching modes of the central conjugated system of the cyanines, while most of the strong IR bands in the 1600-1300 cm -1 region are probably due to antisymmetric stretching modes. The intense RR bands do not have their counterparts in the IR spectra and vice versa. A pseudo-mutual exclusion rule seems to be operative for the cyanine vibrational spectra in the 1600-1300 cm -1 region, indicating that the central conjugated systems of the cyanines have nearly symmetrical structure, i.e. the extended all-trans forms of the methine chains and the bond orders of 1.5 of the CC and CN bonds in both the solution and solid states. The IR spectra of 3-ethyl-2-[3-(3-ethyl-2-benzothiazolinylidene)-1-propenyl]benzothiazolium iodide (NK-76) and 3-ethyl-2-[7-(3-ethyl-2-benzothiazolinylidene)-1,3,5-heptatrienyl]benzothiazolium iodide (NK-126) change little between the solid and solution states while those of 3-octadecyl-2-[3-(3-octadecyl-2-benzothiazolinylidene)-1-propenyl]benzothiazolium iodide (NK-2560) and 3-octadecyl-2-[7-(3-octadecyl-2-benzothiazolinylidene)-1,3,5-heptatrienyl]benzothiazolium perchlorate (NK-2861) alter significantly between the two states in the frequencies of bands due to the stretching modes of their central conjugated systems. The results suggest that the electronic states of the central conjugated systems of NK-2560 and NK-2861 undergo appreciable changes on going from the solid to the solution states.

  11. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach.

    Science.gov (United States)

    Ma, HuiLi; Zhao, Yi; Liang, WanZhen

    2014-03-07

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI(-))), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI(-) although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm(-1) agrees well with the experimental measurement.

  12. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach

    Energy Technology Data Exchange (ETDEWEB)

    Ma, HuiLi [State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Institute of Fujian Provincial Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Zhao, Yi; Liang, WanZhen, E-mail: liangwz@xmu.edu.cn [State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Institute of Fujian Provincial Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China)

    2014-03-07

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI{sup −})), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI{sup −} although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm{sup −1} agrees well with the experimental measurement.

  13. Resonance Raman spectroscopy reveals pH-dependent active site structural changes of lactoperoxidase compound 0 and its ferryl heme O-O bond cleavage products.

    Science.gov (United States)

    Mak, Piotr J; Thammawichai, Warut; Wiedenhoeft, Dennis; Kincaid, James R

    2015-01-14

    The first step in the enzymatic cycle of mammalian peroxidases, including lactoperoxidase (LPO), is binding of hydrogen peroxide to the ferric resting state to form a ferric-hydroperoxo intermediate designated as Compound 0, the residual proton temporarily associating with the distal pocket His109 residue. Upon delivery of this "stored" proton to the hydroperoxo fragment, it rapidly undergoes O-O bond cleavage, thereby thwarting efforts to trap it using rapid mixing methods. Fortunately, as shown herein, both the peroxo and the hydroperoxo (Compound 0) forms of LPO can be trapped by cryoradiolysis, with acquisition of their resonance Raman (rR) spectra now permitting structural characterization of their key Fe-O-O fragments. Studies were conducted under both acidic and alkaline conditions, revealing pH-dependent differences in relative populations of these intermediates. Furthermore, upon annealing, the low pH samples convert to two forms of a ferryl heme O-O bond-cleavage product, whose ν(Fe═O) frequencies reflect substantially different Fe═O bond strengths. In the process of conducting these studies, rR structural characterization of the dioxygen adduct of LPO, commonly called Compound III, has also been completed, demonstrating a substantial difference in the strengths of the Fe-O linkage of the Fe-O-O fragment under acidic and alkaline conditions, an effect most reasonably attributed to a corresponding weakening of the trans-axial histidyl imidazole linkage at lower pH. Collectively, these new results provide important insight into the impact of pH on the disposition of the key Fe-O-O and Fe═O fragments of intermediates that arise in the enzymatic cycles of LPO, other mammalian peroxidases, and related proteins.

  14. Raman Spectroscopy for Homeland Security Applications

    Directory of Open Access Journals (Sweden)

    Gregory Mogilevsky

    2012-01-01

    Full Text Available Raman spectroscopy is an analytical technique with vast applications in the homeland security and defense arenas. The Raman effect is defined by the inelastic interaction of the incident laser with the analyte molecule’s vibrational modes, which can be exploited to detect and identify chemicals in various environments and for the detection of hazards in the field, at checkpoints, or in a forensic laboratory with no contact with the substance. A major source of error that overwhelms the Raman signal is fluorescence caused by the background and the sample matrix. Novel methods are being developed to enhance the Raman signal’s sensitivity and to reduce the effects of fluorescence by altering how the hazard material interacts with its environment and the incident laser. Basic Raman techniques applicable to homeland security applications include conventional (off-resonance Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS, resonance Raman spectroscopy, and spatially or temporally offset Raman spectroscopy (SORS and TORS. Additional emerging Raman techniques, including remote Raman detection, Raman imaging, and Heterodyne imaging, are being developed to further enhance the Raman signal, mitigate fluorescence effects, and monitor hazards at a distance for use in homeland security and defense applications.

  15. Wall-to-wall stress induced in (6,5) semiconducting nanotubes by encapsulation in metallic outer tubes of different diameters: a resonance Raman study of individual C60-derived double-wall carbon nanotubes.

    Science.gov (United States)

    Villalpando-Paez, Federico; Muramatsu, Hiroyuki; Kim, Yoong Ahm; Farhat, Hootan; Endo, Morinobu; Terrones, Mauricio; Dresselhaus, Mildred S

    2010-03-01

    We measure resonant Raman scattering from 11 individual C(60)-derived double-wall carbon nanotubes all having inner semiconducting (6,5) tubes and various outer metallic tubes. The Raman spectra show the radial breathing modes (RBM) of the inner and the outer tubes to be simultaneously in resonance with the same laser energy. We observe that an increase in the RBM frequency of the inner tubes is related to an increase in the RBM frequency of the outer tubes. The Raman spectra also contain a sharp G(-) feature that increases in frequency as the nominal diameter of the outer metallic tubes decreases. Finally, the one-phonon second-order D-band mode shows a two-way frequency splitting that decreases with decreasing nominal wall-to-wall distance. We suggest that the stress which increases with decreasing nominal wall-to-wall distance is responsible for the hardening that is observed in the frequencies of the RBM, D and G(-) modes of the inner (6,5) semiconducting tubes.

  16. Measurements of Rayleigh, Compton and resonant Raman scattering cross-sections for 59.536 keV {gamma}-rays

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Prem; Mehta, D.; Singh, N. E-mail: nsingh@pu.ac.in; Puri, S.; Shahi, J.S

    2004-09-01

    The K-L and K-M resonant Raman scattering (RRS) cross-sections have been measured for the first time at the 59.536 keV photon energy in the {sub 70}Yb (B{sub K}=61.332 keV), {sub 71}Lu (B{sub K}=63.316 keV) and {sub 72}Hf (B{sub K}=65.345 keV) elements; B{sub K} being the K-shell binding energy. The K-L and K-M RRS measurements have been performed at the 59 deg. and 133 deg. angles, respectively, to avoid interference of the Compton-scatter peak. The Rayleigh and Compton scattering cross-sections for the 59.536 keV {gamma}-rays have also been measured at both the angles in the atomic region 1{<=}Z{<=}92. Measurements were performed using the reflection-mode geometrical arrangements involving the {sup 241}Am radioisotope as photon source and planar Si(Li) and HPGe detectors. Ratios of the K-M and K-L RRS cross-sections in Yb, Lu and Hf are in general lower than that of the fluorescent K{beta}{sub 1,3,5} (K-M) and K{alpha} (K-L) X-ray transition probabilities. Theoretical Rayleigh scattering cross-sections based on the modified form-factors (MFs) corrected for the anomalous scattering factors (ASFs) and the S-matrix calculations are on an average {approx}15% and {approx}6% higher, respectively, at the 133 deg. angle and exhibit good agreement with the measured data at the 59 deg. angle. Larger deviations {approx}30% and {approx}20%, respectively, are observed at the 133 deg. angle for the {sub 64}Gd, {sub 66}Dy, {sub 67}Ho and {sub 70}Yb elements having the K-shell binding energy in vicinity of the incident photon energy. The measured Compton scattering cross-sections are in general agreement with those calculated using the Klein-Nishina cross-sections and the incoherent scattering function.

  17. Raman facility

    Data.gov (United States)

    Federal Laboratory Consortium — Raman scattering is a powerful light scattering technique used to diagnose the internal structure of molecules and crystals. In a light scattering experiment, light...

  18. La spectrométrie Raman de résonance résolue dans le temps : une puissante méthode d'investigation en temps réel de la réactivité photochimique Time Resolved Resonance Raman Spectrometry: a Powerful Method for the Real-Time Investigation of Photochemical Reactivity

    Directory of Open Access Journals (Sweden)

    Buntinx G.

    2006-11-01

    Full Text Available La spectroscopie Raman de résonance résolue dans le temps est une technique récente particulièrement bien adaptée à la caractérisation des intermédiaires réactionnels mis en jeu dans les réactions photochimiques (états excités, radicaux, paires d'ions, . . . . Elle permet de visualiser finement les variations de géométrie et de distribution électronique des espèces transitoires tout au long du chemin réactionnel. Nous présentons dans cet article une compilation des résultats obtenus dans notre laboratoire sur des molécules aromatiques dérivées du biphényle. Ces résultats constituent une bonne illustration des potentialités de cette technique à apporter des informations sur la réactivité de cette famille de composés. Après une partie consacrée à la description du dispositif expérimental utilisé dans de telles expériences, nous abordons l'étude structurale par spectrométrie Raman de résonance résolue dans le temps des radicaux cations et des états triplets de dérivés du biphényle. La dernière partie de cet article est consacrée à l'étude de la réactivité photochimique de dérivés de la pyridine (4,4'-bipyridine, 2,2'-bipyridine, 4-phénylpyridine, 2--phénylpyridine dans les solvants organiques par spectrométrie Raman de résonance résolue dans le temps. Time resolved resonance Raman spectroscopy is a recent technique that is particularly well suited for characterizing reaction intermediates involved in photochemical reactions (excited states, radicals, ion pair, etc. . It can finely visualize variations in geometry and electron distribution of transient species along the entire reaction path. This article describes a compilation of the results obtained in our laboratory on aromatic molecules derived from biphenyl. These results are a good illustration of the potentialities of this technique for providing information on the reactivity of this family of compounds. After a section devoted to

  19. One-phonon resonant electron Raman scattering in multilayer coaxial cylindrical AlxGa1-xAs/GaAs quantum cables

    Institute of Scientific and Technical Information of China (English)

    Zhong Qinghu; Yi Xuehua; Pu Shouliang; Yan Yuzhen

    2013-01-01

    We have presented a theoretical calculation of the differential cross section (DCS) for the electron Raman scattering (ERS) process associated with the interface optical (IO) and surface optical (SO) phonons in multilayer coaxial cylindrical AlxGa1-xAs/GaAs quantum cables (QC).We consider the Fr(o)hlich electron-phonon interaction in the framework of the dielectric continuum approach.The selection rules for the processes are studied.Singularities are found to be sensitively size-dependent and by varying the size of the QC,it is possible to control the frequency shift in the Raman spectra.A discussion of the phonon behavior for the QC with different size is presented.The numerical results are also compared with those of experiments.

  20. PULSED KGd(WO42 RAMAN LASER: TOWARDS EMISSION LINEWIDTH NARROWING

    Directory of Open Access Journals (Sweden)

    V. G. Savitski

    2015-01-01

    Full Text Available The linewidth of a KGd(WO42 pulsed Raman laser is analysed experimentally for different configurations of the Raman and pump resonators: with narrow and broadband pump emission profiles, with and without linewidth narrowing elements in the Raman laser resonator, with and without injection seeding into the Raman cavity. The benefits of a narrow linewidth pump source in combination with linewidth narrowing elements in the Raman laser cavity for the efficient linewidth narrowing of the Raman emission are explained. 20 kW peak-power pulses at 1156 nm with 0,43 cm -1 emission linewidth are demonstrated from an injection seeded KGW Raman laser. 

  1. Dynamics of an [Fe4S4(SPh)4]2- cluster explored via IR, Raman, and nuclear resonance vibrational spectroscopy (NRVS)-analysis using 36S substitution, DFT calculations, and empirical force fields.

    Science.gov (United States)

    Xiao, Yuming; Koutmos, Markos; Case, David A; Coucouvanis, Dimitri; Wang, Hongxin; Cramer, Stephen P

    2006-05-14

    We have used four vibrational spectroscopies--FT-IR, FT-Raman, resonance Raman, and 57Fe nuclear resonance vibrational spectroscopy (NRVS)--to study the normal modes of the Fe-S cluster in [(n-Bu)4N]2[Fe4S4(SPh)4]. This [Fe4S4(SR)4]2- complex serves as a model for the clusters in 4Fe ferredoxins and high-potential iron proteins (HiPIPs). The IR spectra exhibited differences above and below the 243 K phase transition. Significant shifts with 36S substitution into the bridging S positions were also observed. The NRVS results were in good agreement with the low temperature data from the conventional spectroscopies. The NRVS spectra were interpreted by normal mode analysis using optimized Urey-Bradley force fields (UBFF) as well as from DFT theory. For the UBFF calculations, the parameters were refined by comparing calculated and observed NRVS frequencies and intensities. The frequency shifts after 36S substitution were used as an additional constraint. A D 2d symmetry Fe4S4S'4 model could explain most of the observed frequencies, but a better match to the observed intensities was obtained when the ligand aromatic rings were included for a D 2d Fe4S4(SPh)4 model. The best results were obtained using the low temperature structure without symmetry constraints. In addition to stretching and bending vibrations, low frequency modes between approximately 50 and 100 cm(-1) were observed. These modes, which have not been seen before, are interpreted as twisting motions with opposing sides of the cube rotating in opposite directions. In contrast with a recent paper on a related Fe4S4 cluster, we find no need to assign a large fraction of the low frequency NRVS intensity to 'rotational lattice modes'. We also reassign the 430 cm(-1) band as primarily an elongation of the thiophenolate ring, with approximately 10% terminal Fe-S stretch character. This study illustrates the benefits of combining NRVS with conventional Raman and IR analysis for characterization of Fe-S centers. DFT

  2. Recent topics on single-molecule fluctuation analysis using blinking in surface-enhanced resonance Raman scattering: clarification by the electromagnetic mechanism.

    Science.gov (United States)

    Itoh, Tamitake; Yamamoto, Yuko S

    2016-08-15

    Surface-enhanced Raman scattering (SERS) spectroscopy has become an ultrasensitive tool for clarifying molecular functions on plasmonic metal nanoparticles (NPs). SERS has been used for in situ probing of detailed behaviors of few or single molecules (SMs) at plasmonic NP junctions. SM SERS signals are commonly observed with temporal and spectral changes known as "blinking", which are related to various physical and chemical interactions between molecules and NP junctions. These temporal and spectral changes simultaneously take place, therefore resulting in serious complexities in interpretations of the SM SERS results. Dual contributions of Raman enhancement mechanisms in SERS (i.e., electromagnetic (EM) and chemical enhancements) also make interpretations more difficult. To resolve these issues and reduce the degree of complexities in SM SERS analyses, the present review is focused on the recent studies of probing SM behaviors using SERS exclusively within the framework of the EM mechanism. The EM mechanism is briefly introduced, and several recent topics on SM SERS blinking analysis are discussed in light of the EM mechanism. This review will provide a basis for clarification of complex SERS fluctuations of various molecules.

  3. Fermi resonance and solvent dependence of the vC=O frequency shifts of Raman spectra: cyclohexanone and 2-cyclohexene-1-one

    CERN Document Server

    Nam, S I; Lee, M S; Jung, Y M

    2001-01-01

    The carbonyl stretching vibration, vC=O of 2-cyclohexene-1-one , is in Fermi resonance with a combination tone. The amount of Fermi resonance interaction between these two modes is dependent upon the amount of solute/solvent interaction due to hydrogen bonding between the carbonyl oxygen and the solvent proton. The corrected vC=O frequency of 2-cyclohexene-1-one occurs at a lower frequency than the observed vC=O mode of cyclohexanone, possibly caused by expanded conjugation effects. The carbonyl stretching modes of cyclic ketones were also affected by interaction with the ROH/CCl sub 4 mixed solvent system.

  4. Resonance Raman Spectroscopy of the Excited State Structural Dynamics of 6-N,N-Dimethyladenine%6-N,N-二甲基腺嘌呤激发态结构动力学的共振拉曼光谱

    Institute of Scientific and Technical Information of China (English)

    刘崇; 杜蕊; 赵彦英; 王惠钢; 郑旭明

    2011-01-01

    The A- and B-band electronic excitations and the excited state structural dynamics of 6-N, N-dimethyladenine (DMA) were studied by resonance Raman spectroscopy and density functional theory calculations.The πH→πL* transition is the main part of the A-band absorption and its calculated oscillator strength occupies 79% of the A-band absorption.n→Ryd and πH→Ryd transitions where Ryd denotes the diffuse Rydberg orbital play important roles in the B-band electronic transitions and their calculated oscillator strengths occupy about 62% of the B-band absorption.The oscillator strength for the πH→πL* transition, which dominates the A-band electronic transition only occupies about 33% of the B-band absorption.The foundamental vibrations of the purine ring deformation stretch plus the C8H/N9H bend mode ν23 and the 5 member ring deformation stretch plus the C8H bend mode ν13, and their overtones and combination bands occupy most of the A-band resonance Raman intensities.Therefore, the 1πHπL* excited state structural dynamics of DMA is mainly along the ν23 and ν13 reaction coordinates.The majority of the B-band resonance Raman intensities are dominated by the fundamental vibrations of ν10, ν29, ν21, ν26, ν40,and their overtones and combination bands.This suggests the B-band excited state structural dynamics of DMA is mostly along the purine ring deformation, the C6N10 stretch, the N9H/C8H/C2H bend and the N(CH3)2 antisymmetric stretch.The appearance of ν26 and ν12 in the A-band resonance Raman spectrum is correlated to the Franck-Condon region 1nπ*/1ππ* conical intersection.The activation of ν21 in the B-band resonance Raman spectrum is correlated to the Franck-Condon region 1ππ*/1πσ* N9H conical intersection.%采用共振拉曼光谱技术和密度泛函理论方法研究了6-N,N-二甲基腺嘌呤(DMA)的A带和B带电子激发和Franck-Condon区域结构动力学.πH→π*L跃迁是A带吸收的主体,其振子强

  5. Applications of Raman Spectroscopy to Virology and Microbial Analysis

    Science.gov (United States)

    Harz, Michaela; Stöckel, Stephan; Ciobotă, Valerian; Cialla, Dana; Rösch, Petra; Popp, Jürgen

    This chapter reports from the utilization of Raman spectroscopic techniques like Raman microscopy, Raman optical activity (ROA), UV-resonance Raman (UVRR)-spectroscopy, surface enhanced Raman spectroscopy (SERS), and tip-enhanced Raman spectroscopy (TERS) for the investigation of viruses and microorganisms, especially bacteria and yeasts for medical and pharmaceutical applications. The application of these Raman techniques allows for the analysis of chemical components of cells and subcellular regions, as well as the monitoring of chemical differences occurring as a result of the growth of microorganisms. In addition, the interaction of microorganisms with active pharmaceutical agents can be investigated. In combination with chemometric methods Raman spectroscopy can also be applied to identify microorganisms both in micro colonies and even on single cells.

  6. N-hydroxyguanidines as new heme ligands: UV-visible, EPR, and resonance Raman studies of the interaction of various compounds bearing a C=NOH function with microperoxidase-8.

    Science.gov (United States)

    Lefevre-Groboillot, D; Dijols, S; Boucher, J L; Mahy, J P; Ricoux, R; Desbois, A; Zimmermann, J L; Mansuy, D

    2001-08-21

    Interaction between microperoxidase-8 (MP8), a water-soluble hemeprotein model, and a wide range of N-aryl and N-alkyl N'-hydroxyguanidines and related compounds has been investigated using UV-visible, EPR, and resonance Raman spectroscopies. All the N-hydroxyguanidines studied bind to the ferric form of MP8 with formation of stable low-spin iron(III) complexes characterized by absorption maxima at 405, 535, and 560 nm. The complex obtained with N-(4-methoxyphenyl) N'-hydroxyguanidine exhibits EPR g-values at 2.55, 2.26, and 1.86. The resonance Raman (RR) spectrum of this complex is also in agreement with an hexacoordinated low-spin iron(III) structure. The dissociation constants (K(s)) of the MP8 complexes with mono- and disubstituted N-hydroxyguanidines vary between 15 and 160 microM at pH 7.4. Amidoximes also form low-spin iron(III) complexes of MP8, although with much larger dissociation constants. Under the same conditions, ketoximes, aldoximes, methoxyguanidines, and guanidines completely fail to form such complexes with MP8. The K(s) values of the MP8-N-hydroxyguanidine complexes decrease as the pH of the solution is increased, and the affinity of the N-hydroxyguanidines toward MP8 increases with the pK(a) of these ligands. Altogether these results show that compounds involving a -C(NHR)=NOH moiety act as good ligands of MP8-Fe(III) with an affinity that depends on the electron-richness of this moiety. The analysis of the EPR spectrum of the MP8-N-hydroxyguanidine complexes according to Taylor's equations shows a strong axial distortion of the iron, typical of those observed for hexacoordinated heme-Fe(III) complexes with at least one pi donor axial ligand (HO(-), RO(-), or RS(-)). These data strongly suggest that N-hydroxyguanidines bind to MP8 iron via their oxygen atom after deprotonation or weakening of their O-H bond. It thus seems that N-hydroxyguanidines could constitute a new class of strong ligands for hemeproteins and iron(III)-porphyrins.

  7. Competition between resonant Raman scattering and fluorescence at the L/sub 3/-edges with final 3s hole in CoO and in NiO

    CERN Document Server

    Borgatti, F; Brookes, N B; Ghiringhelli, G; Tagliaferri, A

    1999-01-01

    We present results on inelastic photon scattering in NiO and CoO in the L/sub 3/ threshold region ending with a final 3s hole i.e. 2p/sup 6/3d/sup n/ to 2p/sup 5/3d/sup n+1/ to 2p/sup 6/3d/sup n+1/3s/sup 1/. The spectra show the presence of Raman features dispersing with the incident photon energy and of a strong feature at constant outgoing photon energy. In CoO the results show that this constant energy feature is present only when the core excitation is 2-3 eV above the core absorption thresholds. This supports a simple model based on the energy loss due to the creation of electron hole pairs across the gap. This mechanism can convert the intermediate excited state into a state of lower energy decaying with the emission at constant photon energy. The implications of these results are briefly discussed. (9 refs).

  8. Raman spectral research on MPCVD diamond film

    Institute of Scientific and Technical Information of China (English)

    YAN Yan; ZHANG Shulin; ZHAO Xinsheng; HAN Yisong; HOU Li

    2003-01-01

    Raman spectra of MPCVD diamond film have been studied. Based on the resonance size selection effect, we think that there is no nano-crystalline diamond in the sample and the Raman peak at 1145 cm-1 can not be considered as the characteristic peak of nano-crystalline diamond though it has been used as the characteristic peak of nano-crystalline diamond widely for many years.

  9. Polarized and depolarized Raman spectra of liquid carbon disulfide in the pressure range 0-10 kbar. I. Vibration frequencies, C-S bond length, and Fermi resonance

    Science.gov (United States)

    Ikawa, S.; Whalley, Edward

    1986-09-01

    The effect of pressure on the polarized and depolarized Raman spectra of liquid carbon disulphide, i.e., the peak frequencies, bandwidths, and relative intensities of both the allowed ν1 and 2ν2 bands and the interaction-induced ν2 and ν3 bands, have been measured at 22 °C up to 10 kbar. This paper discusses the effect of pressure on the frequencies and on the relative isotropic intensity of the ν1 and 2ν2 bands. The frequency of the ν1 band increases linearly with pressure, within the experimental uncertainty, at the rate 0.16±0.01 cm-1 kbar-1, and the frequencies of the ν2, ν3, and 2ν2 bands decrease nonlinearly. The frequency shifts are described by second-order perturbation theory with the molecular anharmonicity and the intermolecular interaction as perturbations. The leading terms of the shifts consist of the same derivative of the interaction potential, multiplied by different anharmonicity constants, and the shifts of the ν1 and 2ν2 bands suggests that the C-S bond length decreases at the rate 2×10-4 Å kbar-1. The relative isotropic intensity of the 2ν2 and ν1 bands increases with pressure at the rate 0.050 kbar-1, whereas the anisotropic 2ν2 intensity relative to the isotropic ν1 intensity is independent of pressure to the experimental precision of ˜0.005. The effect of pressure on the second derivative of the isotropic and anisotropic parts of the polarizability with respect to the bend coordinate was estimated as 1.1×10-43 C m2 V-1 kbar-1 and ˜0, respectively, from these values.

  10. Study of the configurations of 3-aryl-substituted 1,5-diphenylformazans by resonance Raman and absorption spectroscopy: steric and conjugation effects of the substituent

    Science.gov (United States)

    Hiura, Hidefumi; Takahashi, Hiroaki

    1989-09-01

    3-Aryl-substituted 1,5-diphenylformazans exist as one of the following two isomeric species in the solid state; the yellow isomer having the trans-anti-s- trans configuration with respect to the NN, CN and CN bonds of the formazan skeleton and the red isomer having the trans-syn-s- cis configuration. The other red isomer having the trans-syn-s- trans configuration, which exists when the substituent is an alkyl group, is not detected. Two effects are considered to be operative in determining the relative stabilities of these configurations: (1) the resonance energy arising from the conjugation between the π-electron systems of the formazan skeleton and the aryl substituent, and (2) the steric repulsion between the formazan skeleton and the groups (or atoms) attached to the ortho positions of the aryl substituent. In solutions, these two isomers are in equilibrium, their relative populations being dependent on the nature of the solvent as well as on the bulkiness of the groups attached to the ortho positions of the aryl substituent.

  11. On-Line Multichannel Raman Spectroscopic Detection System For Capillary Zone Electrophoresis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An on-line multichannel Raman spectroscopic detection system for capillary electrophoresis was established by using an Ar+ laser and a cryogenically cooled ICCD. Resonant excitation Raman spectra of methyl red and methyl orange were employed to test the system. The result shows that it could yield on-line electrophoretogram and time series of Raman spectra.

  12. Mapping Chemical and Structural Composition of Pharmaceutical and Biological Samples by Raman, Surface-Enhanced Raman and Fluorescence Spectral Imaging

    Science.gov (United States)

    Chourpa, Igor; Cohen-Jonathan, Simone; Dubois, Pierre

    Raman spectroscopy is an analytical technique recognised for its structural and conformational specificity. The efficient discrimination of molecular species by Raman is particularly potent for multidimensional microscopic imaging of complex biological environment, as demonstrated in the present book. The commonly admitted problem of Raman, low sensitivity, can often be circumvented due to high output instruments and via approaches like RRS (resonance Raman scattering), SERS (surface-enhanced Raman scattering), TERS (tip-enhanced Raman scattering) or CARS (coherent anti-Stokes Raman scattering). In contrast to the latter, RRS and SERS are realizable with less sophisticated set-up based on common Raman systems. Although more invasive than RRS, SERS provides better sensitivity and quenching of fluorescence. SERRS (surface-enhanced resonance Raman scattering) spectroscopy can be used in coupling with fluorescence and competes in selectivity and sensitivity with spectrofluorimetry. In the chapter below, we use recent applications made in our group to illustrate the use of Raman and SERRS spectral imaging for characterization of biological samples (animal subcutaneous tissue, human cancer cells) and pharmaceutical samples (microparticles for drug delivery, fibres for wound dressing). After a brief description of experimental details on spectral imaging, the chapter will focus on results concerning (i) biocompatible pharmaceutical materials made of alginates and (ii) anticancer drugs in pharmaceutical forms and in biological systems.

  13. Ultraviolet resonance Raman studies reveal the environment of tryptophan and tyrosine residues in the native and partially folded states of the E colicin-binding immunity protein Im7.

    Science.gov (United States)

    Rodriguez-Mendieta, Iñigo R; Spence, Graham R; Gell, Christopher; Radford, Sheena E; Smith, D Alastair

    2005-03-01

    Understanding the nature of partially folded proteins is a challenging task that is best accomplished when several techniques are applied in combination. Here we present ultraviolet resonance Raman (UVRR) spectroscopy studies of the E colicin-binding immunity proteins, Im7* and Im9*, together with a series of variants of Im7* that are designed to trap a partially folded state at equilibrium. We show that the environments of the tryptophan and tyrosine residues in native wild-type Im7* and Im9* are indistinguishable, in contrast with models for their structures based on X-ray and NMR methods. In addition, we show that there is a general increase in the hydrophobicity in the environment of Trp75 in all of the variants compared with wild-type Im7*. These data suggest that a significant rearrangement of the tryptophan pocket occurs in the variants, which, together with an overall decrease in solvent accessibility of Trp75 as judged by time-resolved fluorescence lifetime measurements and fluorescence quenching experiments, rationalize the unusual fluorescence properties of the variants reported previously. The data highlight the power of UVRR in analyzing the structural properties of different conformational states of the same protein and reveal new information about the structural rearrangements occurring during Im7* folding, not possible using other spectroscopic methods alone. Finally, we describe a previously unreported dependence of the tryptophan Fermi doublet on excitation wavelength in the ultraviolet region revealed by these protein spectra. We corroborated this observation using tryptophan-containing model compounds and conclude that the conventional interpretation of this UVRR feature at these wavelengths is unreliable.

  14. Identification of the chromophore in the apatite pigment [Sr10(PO4)6(Cu(x)OH(1-x-y))2]: linear OCuO- featuring a resonance Raman effect, an extreme magnetic anisotropy, and slow spin relaxation.

    Science.gov (United States)

    Kazin, Pavel E; Zykin, Mikhail A; Zubavichus, Yan V; Magdysyuk, Oxana V; Dinnebier, Robert E; Jansen, Martin

    2014-01-03

    A new chromophore has been identified in copper-doped apatite pigments having the general composition [Sr(10)(PO(4))(6)(Cu(x)OH(1-x-y))(2)], in which x=0.1, 0.3 and y=0.01-0.42. By using X-ray absorption spectroscopy, low-temperature magnetization measurements, and synchrotron X-ray powder structure refinement, it has been shown that the oxygenated compounds contain simultaneously diamagnetic Cu(1+) and paramagnetic Cu(3+) with S=1. Cu(3+) is located at the same crystallographic position as Cu(1+), being linearly coordinated by two oxygen atoms and forming the OCuO(-) anion. The Raman spectroscopy study of [A(10)(PO(4))(6)(Cu(x)OH(1-x-y))(2)], in which A=Ca, Sr, Ba, reveals resonance bands at 651-656 cm(-1) assigned to the symmetric stretching vibration (ν(1)) of OCuO(-). The strontium apatite pigment exhibits a strong paramagnetic anisotropy with an unprecedentedly large negative zero-field splitting parameter (D) of ≈-400 cm(-1). The extreme magnetic anisotropy causes slow magnetization relaxation with relaxation times (τ) up to 0.3 s at T=2 K, which relates the compounds to single-ion magnets. At low temperature, τ is limited by a spin quantum-tunneling, whereas at high temperature a thermally activated relaxation prevails with U(eff)≈48 cm(-1). Strong dependence of τ on the paramagnetic center concentration at low temperature suggests that the spin-spin relaxation dominates in the spin quantum-tunneling process. The compound is the first example of a d-metal-based single-ion magnet with S=1, the smallest spin at which an energy barrier arises for the spin flipping.

  15. Vibrational imaging based on stimulated Raman scattering microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nandakumar, P; Kovalev, A; Volkmer, A [3. Physikalisches Institut, Universitaet Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany)], E-mail: a.volkmer@physik.uni-stuttgart.de

    2009-03-15

    A stimulated Raman scattering microscope with near-infrared picosecond laser pulses at high repetition rates (76 MHz) and radio-frequency lock-in detection is accomplished. Based on stimulated Raman loss detection, we demonstrate noninvasive point-by-point vibrational mapping of chemical and biological samples with high sensitivity and without the requirement for labeling of the sample with natural or artificial fluorophores. We experimentally demonstrate a major benefit of this technique, which is the capability to respond exclusively to the linear Raman-resonance properties of the sample, thus allowing a direct quantitative interpretation of image contrast in terms of the number density of Raman-active modes.

  16. Vibrational imaging based on stimulated Raman scattering microscopy

    Science.gov (United States)

    Nandakumar, P.; Kovalev, A.; Volkmer, A.

    2009-03-01

    A stimulated Raman scattering microscope with near-infrared picosecond laser pulses at high repetition rates (76 MHz) and radio-frequency lock-in detection is accomplished. Based on stimulated Raman loss detection, we demonstrate noninvasive point-by-point vibrational mapping of chemical and biological samples with high sensitivity and without the requirement for labeling of the sample with natural or artificial fluorophores. We experimentally demonstrate a major benefit of this technique, which is the capability to respond exclusively to the linear Raman-resonance properties of the sample, thus allowing a direct quantitative interpretation of image contrast in terms of the number density of Raman-active modes.

  17. Raman properties of GaSb nanoparticles embedded in SiO2 films

    Institute of Scientific and Technical Information of China (English)

    Liu Fa-Min; Wang Tian-Min; Zhang Li-De

    2004-01-01

    The Raman shifts of nanocrystalline GaSb excited by an Ar+ ion laser at wavelengths 514.5, 496.5, 488.0, 476.5,and 457.9nm are studied by an SPEX-1403 laser Raman spectrometer respectively, and they are explained by phonon confinement, tensile stress, resonant Raman scattering and quantum size effects. The Stokes and anti-Stokes Raman spectra of GaSb nanocrystals strongly support the Raman feature of GaSb nanocrystals. The calculated optical spectra compare well with experimental data on Raman scattering GaSb nanocrystals.

  18. UV Raman imaging--a promising tool for astrobiology: comparative Raman studies with different excitation wavelengths on SNC Martian meteorites.

    Science.gov (United States)

    Frosch, Torsten; Tarcea, Nicolae; Schmitt, Michael; Thiele, Hans; Langenhorst, Falko; Popp, Jürgen

    2007-02-01

    The great capabilities of UV Raman imaging have been demonstrated on the three Martian meteorites: Sayh al Uhaymir, Dar al Gani, and Zagami. Raman spectra without disturbing fluorescence and with high signal-to-noise-ratios and full of spectral features were derived. This result is of utmost importance for the development of powerful instruments for space missions. By point scanning the surfaces of the meteorite samples, it was possible for the first time to construct UV-Raman images out of the array of Raman spectra. Deep-UV Raman images are to the best of our knowledge presented for the first time. The images were used for a discussion of the chemical-mineralogical composition and texture of the meteorite surfaces. Comparative Raman studies applying visible and NIR Raman excitation wavelengths demonstrate a much better performance for UV Raman excitation. This comparative study of different Raman excitation wavelengths at the same sample spots was done by constructing a versatile, robust sample holder with a fixed micro-raster. The overall advantages of UV resonance Raman spectroscopy in terms of sensitivity and selectivity are demonstrated and discussed. Finally the application of this new technique for a UV Raman instrument for envisaged astrobiological focused space missions is suggested.

  19. Raman Spectroscopy of Ocular Tissue

    Science.gov (United States)

    Ermakov, Igor V.; Sharifzadeh, Mohsen; Gellermann, Warner

    excised tissue samples and synthetic preparations and thus to identify potential biomarkers for the onset of this disease. Using resonance Raman detection techniques, the concentration and spatial distribution of macular pigment, a protective compound, can be detected in the living human retina Useable in clinical settings for patient screening, the technology is suitable to investigate correlations between pigment concentration levels and risk for macular degeneration and to monitor increases in pigment levels occurring as a result of dietary intervention strategies.

  20. Coherently controlling Raman-induced grating in atomic media

    CERN Document Server

    Arkhipkin, V G; Timofeev, I V

    2015-01-01

    We consider dynamically controllable periodic structures, called Raman induced gratings, in three- and four-level atomic media, resulting from Raman interaction in a standing-wave pump. These gratings are due to periodic spatial modulation of the Raman nonlinearity and fundamentally differ from the ones based on electromagnetically induced transparency. The transmission and reflection spectra of such gratings can be simultaneously amplified and controlled by varying the pump field intensity. It is shown that a transparent medium with periodic spatial modulation of the Raman gain can be opaque near the Raman resonance and yet at the same time it can be a non-linear amplifying mirror. We also show that spectral properties of the Raman induced grating can be controlled with the help of an additional weak control field.

  1. Enhanced Raman Scattering by Molecular Nanoaggregates

    Directory of Open Access Journals (Sweden)

    Daniel L. Akins

    2014-02-01

    Full Text Available The formation of a molecular aggregate in a confined, nanodimensioned region of space leads to what might be termed a ‘molecular nanoaggregate’. The present review deals with a theoretical formulation termed ‘aggregation-enhanced Raman scattering’ (AERS, and its use in discussion of relative Raman band intensities and selection rules for nanoaggregates. AERs represents a concept for discussion of nanoaggregates that is different from those provided by resonance Raman scattering, surface-enhanced Raman scattering and Mie scattering, all of which ignore the impact of aggregation of molecules on Raman scattering. Beyond the theoretical formulation behind the AERS phenomenon, also outlined in this review are representative samples of the publications of other authors and researchers using AERS to provide explanations for experimental findings. In addition to clarifying issues regarding the use of nanocomposites involving aggregated molecules, it is found that increasing use of AERS concepts is being made to rationalize Raman spectral observations in a range of other disciplines that fall in both the physical sciences and the medical fields.

  2. Coherent Raman spectroscopy

    CERN Document Server

    Eesley, G L

    1981-01-01

    Coherent Raman Spectroscopy provides a unified and general account of the fundamental aspects of nonlinear Raman spectroscopy, also known as coherent Raman spectroscopy. The theoretical basis from which coherent Raman spectroscopy developed is described, along with its applications, utility, and implementation as well as advantages and disadvantages. Experimental data which typifies each technique is presented. This book is comprised of four chapters and opens with an overview of nonlinear optics and coherent Raman spectroscopy, followed by a discussion on nonlinear transfer function of matter

  3. Theory of Acoustic Raman Modes in Proteins

    Science.gov (United States)

    DeWolf, Timothy; Gordon, Reuven

    2016-09-01

    We present a theoretical analysis that associates the resonances of extraordinary acoustic Raman (EAR) spectroscopy [Wheaton et al., Nat. Photonics 9, 68 (2015)] with the collective modes of proteins. The theory uses the anisotropic elastic network model to find the protein acoustic modes, and calculates Raman intensity by treating the protein as a polarizable ellipsoid. Reasonable agreement is found between EAR spectra and our theory. Protein acoustic modes have been extensively studied theoretically to assess the role they play in protein function; this result suggests EAR spectroscopy as a new experimental tool for studies of protein acoustic modes.

  4. Waveguide-coupled directional Raman radiation for surface analysis.

    Science.gov (United States)

    Chen, Chen; Li, Jin-Yang; Wang, Li; Lu, Dan-Feng; Qi, Zhi-Mei

    2015-09-01

    Kretschmann-type waveguide structures, including Plasmon Waveguide (PW) and Resonant Mirror (RM), have been applied in interfacial Raman spectroscopy due to the following unique features: (1) unlike the classic surface enhanced Raman scattering (SERS) substrates made of either gold or silver, both PW and RM can be prepared using a large variety of inexpensive materials; (2) the field enhancement factors using these structures can be theoretically predicted and experimentally controlled, which enables us to manipulate the surface Raman sensitivity with high repeatability; (3) the use of transverse electric (TE) and transverse magnetic (TM) modes for Raman excitation allows us to evaluate the orientation of target molecules immobilized on the waveguide surface; (4) the unwanted impact of noble metals on the Raman fingerprints of target molecules, which is often observed for conventional SERS substrates, can be avoided upon the use of dielectric waveguides. In this paper, guided-mode-coupled directional Raman emission, which is an additional important feature of the waveguide Raman technique, was theoretically investigated based on the optical reciprocity theorem combined with the Fresnel equations. The simulation results indicate that the directional Raman emission from a dipole located within the field confinement and penetration depth of a guided mode depends on both the orientation of the dipole and its distance from the waveguide surface. Raman light from the TE-oriented dipoles is launched into the prism coupler at the TE-mode resonance angle and that from the non-TE-oriented dipoles propagates at the TM-mode resonance angle. The intensity of the guided-mode-excited Raman signal propagating at the mode resonance angle is proportional to the fourth power of the mode field (E(4)) at the depth of the dipole from the waveguide surface. This means that the guided-mode-excited and guided-mode-coupled directional Raman spectroscopy has a detection depth that is as

  5. Raman spectra of carotenoids in natural products

    Science.gov (United States)

    Withnall, Robert; Chowdhry, Babur Z.; Silver, Jack; Edwards, Howell G. M.; de Oliveira, Luiz F. C.

    2003-08-01

    Resonance Raman spectra of naturally occurring carotenoids have been obtained from nautilus, periwinkle ( Littorina littorea) and clam shells under 514.5 nm excitation and these spectra are compared with the resonance Raman spectra obtained in situ from tomatoes, carrots, red peppers and saffron. The tomatoes, carrots and red peppers gave rise to resonance Raman spectra exhibiting a ν1 band at ca. 1520 cm -1, in keeping with its assignment to carotenoids with ca. nine conjugated carboncarbon double bonds in their main chains, whereas the resonance Raman spectrum of saffron showed a ν1 band at 1537 cm -1 which can be assigned to crocetin, having seven conjugated carboncarbon double bonds. A correlation between ν1 wavenumber location and effective conjugated chain length has been used to interpret the data obtained from the shells, and the wavenumber position (1522 cm -1) of the ν1 band of the carotenoid in the orange clam shell suggests that it contains nine conjugated double bonds in the main chain. However, the black periwinkle and nautilus shells exhibit ν1 bands at 1504 and 1496 cm -1, respectively. On the basis of the correlation between ν1 wavenumber location and effective conjugated chain length, this indicates that they contain carotenoids with longer conjugated chains, the former having ca. 11 double bonds and the latter ca. 13 or even more. Raman spectra of the nautilus, periwinkle and clam shells also exhibited a strong band at 1085 cm -1 and a doublet with components at 701 and 705 cm -1, which can be assigned to biogenic calcium carbonate in the aragonite crystallographic form.

  6. Time—dependent Theory of Raman Scattering with Pulses—Application to Continuum Raman Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Soo-Y.Lee

    1995-01-01

    A theory of real-time dependence of Raman scattering for a pulse-mode laser is developed within second-order perturbation theory and using the wavepacket terminology.We apply the theory to continuum Raman scattering for short and long pulses and varying pulse carrier frequency,For an initial ground virational state,it is shown that the rate of Raman emission as a funcition of time and pulse carrier frequency is structureless for all pulses,and for pulses that are longer than the dissociation time the rate also decays with the pulses.This is contrary to recently reported resonance fluorescence type structures at long times (M.Shapiro,J.Chem.Phys.99,2453(1993),We explain why such structures are unphysical for continuum Raman scattering.

  7. Effect of axial ligands on the spectroelectrochemical properties of zinc phthalocyanine films. In situ Raman and electroreflection spectra

    NARCIS (Netherlands)

    Palys, B.J.; Ham, van den D.M.W.; Otto, C.

    1994-01-01

    Electroreflection and Raman spectra (in situ and ex situ) of zinc phthalocyanine (ZnPc) films (80 nm thick) have been studied. Raman spectra were resonantly and preresonantly enhanced. Both electroreflection and Raman experiments reveal the homogeneous inclusion of electrolyte anions upon oxidation

  8. Confocal Raman Microscopy

    CERN Document Server

    Dieing, Thomas; Toporski, Jan

    2011-01-01

    Confocal Raman Microscopy is a relatively new technique that allows chemical imaging without specific sample preparation. By integrating a sensitive Raman spectrometer within a state-of-the-art microscope, Raman microscopy with a spatial resolution down to 200nm laterally and 500nm vertically can be achieved using visible light excitation. Recent developments in detector and computer technology as well as optimized instrument design have reduced integration times of Raman spectra by orders of magnitude, so that complete images consisting of tens of thousands of Raman spectra can be acquired in seconds or minutes rather than hours, which used to be standard just one decade ago. The purpose of this book is to provide the reader a comprehensive overview of the rapidly developing field of Confocal Raman Microscopy and its applications.

  9. Raman Spectra of Glasses

    Science.gov (United States)

    1986-11-30

    17), Raman spectra, plus a , . theoretical treatment of the data, f complex fluorozirconate 14 I anions in ZBLAN glasses and melts (16), and...based ZBLAN glasses ) 17. ICORS (International Conference on Raman Spectroscopy) Proceedings, London, England. Conferencf 5-9 Sep 88. (Molten silica...RESEARCH FINAL REPORT DTIC CONTRACT N00014-81-K-0501 &JELECTE 1 MAY 81 -- 30 NOV 86 EJJAN041989 V "RAMAN SPECTRA OF GLASSES " 0 During the five years of the

  10. Versatility of heme coordination demonstrated in a fungal peroxidase. Absorption and resonance Raman studies of Coprinus cinereus peroxidase and the Asp245-->Asn mutant at various pH values.

    Science.gov (United States)

    Smulevich, G; Neri, F; Marzocchi, M P; Welinder, K G

    1996-08-13

    The pH dependence of the electronic absorption and resonance Raman (RR) spectra of FeIII and FeII forms of Coprinus cinereus peroxidase (CIP) and its Asp245-->Asn (D245N) mutant has been examined in detail. The spectral data were obtained in the pH range 3.8-12.0. These spectra were used to assess the spin and ligation states of the heme via the porphyrin marker band frequencies and the wavelengths of the absorption maxima, especially that of the band (CT1) due to the charge transfer from the porphyrin to the heme iron via the a' 2u(pi)-->eg (d pi) electronic transition. The RR spectra were obtained by using different excitation wavelengths and polarized light. The data obtained for ferric CIP show that two pH-induced structural transitions exist. At acid pH the Soret and the CT1 absorption maxima occur at 394 and 652 nm, respectively, compared with the values of 403 and 649 nm observed at neutral pH. The electronic data indicate that at acid pH the proximal Fe-Im bond might be weakened or ruptured, and the RR spectra show a new species (5-c HS) different from the normal neutral 5-coordinate high-spin (5-c HS) heme. At pH 12.0, the protein converts to a 6-coordinate low-spin (6-c LS) heme with a hydroxyl ligand coordinated in the sixth position of the heme iron and strongly hydrogen-bonded with the positively charged guanidinium group of the distal Arg51 residue. Replacement of the aspartate carboxylate group of Asp245, which acts as hydrogen-bond acceptor to the proximal His183 ligand of the heme Fe, with a carboxamide group of an asparagine residue has a profound influence on the heme coordination. The RR spectra of the Fe(II) form of this mutant at both neutral and alkaline pH values show a band at 204 cm-1 assigned to the Fe-His stretch associated with a fairly weak or non-hydrogen-bonded imidazole. The ferric form of the mutant shows a great variability in coordination and spin states upon pH titration. Between pH 8.8 and 3.8 the spectra are mainly

  11. Compact single-channel Raman detector for macular pigments

    Science.gov (United States)

    Ermakov, Igor V.; Ermakova, Maia R.; Gellermann, Werner

    2004-07-01

    Raman detection of macular pigments (MP) holds promise as a novel noninvasive technology for the quantification of lutein and zeaxanthin carotenoids, which are thought to prevent or delay the onset of age-related macular degeneration. Using resonant excitation in the visible, we measure the Raman signals that originate from the double-bond stretch vibrations of the p-conjugated carotenoid molecule's carbon backbone. In this paper we describe the construction and performance of a new, compact, and low-cost MP Raman instrument using dielectric, angle-tuned band-pass filters for wavelength selection and single-channel photo-multiplier detection of carotenoid Raman responses. MP concentration measurements are fast and accurate, as seen in experiments with model eyes and living human eyes. The ease and rapidity of Raman MP measurements, the relative simplicity of the instrumentation, the high accuracy of the measurements, and the lack of significant systematic errors should make this technology useful for widespread clinical research.

  12. Relaxation mechanism of β-carotene from S2 (1Bu(+)) state to S1 (2Ag(-)) state: femtosecond time-resolved near-IR absorption and stimulated resonance Raman studies in 900-1550 nm region.

    Science.gov (United States)

    Takaya, Tomohisa; Iwata, Koichi

    2014-06-12

    Carotenoids have two major low-lying excited states, the second lowest (S2 (1Bu(+))) and the lowest (S1 (2Ag(-))) excited singlet states, both of which are suggested to be involved in the energy transfer processes in light-harvesting complexes. Studying vibrational dynamics of S2 carotenoids requires ultrafast time-resolved near-IR Raman spectroscopy, although it has much less sensitivity than visible Raman spectroscopy. In this study, the relaxation mechanism of β-carotene from the S2 state to the S1 state is investigated by femtosecond time-resolved multiplex near-IR absorption and stimulated Raman spectroscopy. The energy gap between the S2 and S1 states is estimated to be 6780 cm(-1) from near-IR transient absorption spectra. The near-IR stimulated Raman spectrum of S2 β-carotene show three bands at 1580, 1240, and 1050 cm(-1). When excess energy of 4000 cm(-1) is added, the S1 C═C stretch band shows a large upshift with a time constant of 0.2 ps. The fast upshift is explained by a model that excess energy generated by internal conversion from the S2 state to the S1 state is selectively accepted by one of the vibronic levels of the S1 state and is redistributed among all the vibrational modes.

  13. Stochastic phenomena in a fiber Raman amplifier

    CERN Document Server

    Kalashnikov, Vladimir; Ania-Castanón, Juan Diego; Jacobsen, Gunnar; Popov, Sergei

    2016-01-01

    The interplay of such cornerstones of modern nonlinear fiber optics as a nonlinearity, stochasticity and polarization leads to variety of the noise induced instabilities including polarization attraction and escape phenomena harnessing of which is a key to unlocking the fiber optic systems specifications required in high resolution spectroscopy, metrology, biomedicine and telecommunications. Here, by using direct stochastic modeling, the mapping of interplay of the Raman scattering-based nonlinearity, the random birefringence of a fiber, and the pump-to-signal intensity noise transfer has been done in terms of the fiber Raman amplifier parameters, namely polarization mode dispersion, the relative intensity noise of the pump laser, fiber length, and the signal power. The obtained results reveal conditions for emergence of the random birefringence-induced resonance-like enhancement of the gain fluctuations (stochastic anti-resonance) accompanied by pulse broadening and rare events in the form of low power outpu...

  14. On-Chip Diamond Raman Laser

    CERN Document Server

    Latawiec, Pawel; Burek, Michael J; Hausmann, Birgit J M; Bulu, Irfan; Loncar, Marko

    2015-01-01

    Synthetic single-crystal diamond has recently emerged as a promising platform for Raman lasers at exotic wavelengths due to its giant Raman shift, large transparency window and excellent thermal properties yielding a greatly enhanced figure-of-merit compared to conventional materials. To date, diamond Raman lasers have been realized using bulk plates placed inside macroscopic cavities, requiring careful alignment and resulting in high threshold powers (~W-kW). Here we demonstrate an on-chip Raman laser based on fully-integrated, high quality-factor, diamond racetrack micro-resonators embedded in silica. Pumping at telecom wavelengths, we show Stokes output discretely tunable over a ~100nm bandwidth around 2-{\\mu}m with output powers >250 {\\mu}W, extending the functionality of diamond Raman lasers to an interesting wavelength range at the edge of the mid-infrared spectrum. Continuous-wave operation with only ~85 mW pump threshold power in the feeding waveguide is demonstrated along with continuous, mode-hop-fr...

  15. Enhanced Raman scattering of graphene on Ag nanoislands

    Institute of Scientific and Technical Information of China (English)

    HU Wei; HUANG ZhiYi; ZHOU YingHui; CAI WeiWei; KANG JunYong

    2014-01-01

    The effect of Ag nanoislands on the Raman of graphene was investigated in this work.Compared with that on the bare silicon wafer,Raman enhancement was observed in the graphene film that covered on Ag/Si surface with nanoscale Ag islands,which would be induced by the localized plasmon resonance in Ag nanostructures.The interaction between the graphene sheet and Ag/Si substrate was further studied.The peak shift and line shape of Raman spectroscopy indicated a nonuniform strain distribution in the Ag/Si supported graphene film.

  16. Raman modes in transferred bilayer CVD graphene

    Directory of Open Access Journals (Sweden)

    Niilisk Ahti

    2015-01-01

    Full Text Available A systematic experimental Raman spectroscopic study of twisted bilayer graphene (tBLG domains localized inside wide-area single layer graphene (SLG produced by low-pressure CVD on Cu foil and transferred onto SiO2/Si substrate has been performed. According to the Raman characterization the tBLG domains had a great variety of twisting angles θ between the bottom and top graphene layers (6° < θ < 25°. The twisting angle θ was estimated from the spectral position of the rotating R and R' modes in the Raman spectrum.Under G band resonance conditions the breathing mode ZO' with a frequency of 95- 97 cm−1 was detected, and a breathing mode ZO was found in the spectra between 804 cm−1 and 836 cm−1, its position depending on the twisting angle θ. An almost linear relationship was found between the frequencies ωZO and ωR. Also a few other spectral peculiarities were found, e.g. a high-energy excitation of the G band resonance, the 2G overtone appearing at 3170-3180 cm−1 by the G band resonance, revealing a linear dispersion of 80 cm−1/eV of the 2D band in tBLG

  17. Raman crystallography of RNA.

    Science.gov (United States)

    Gong, Bo; Chen, Jui-Hui; Yajima, Rieko; Chen, Yuanyuan; Chase, Elaine; Chadalavada, Durga M; Golden, Barbara L; Carey, Paul R; Bevilacqua, Philip C

    2009-10-01

    Raman crystallography is the application of Raman spectroscopy to single crystals. This technique has been applied to a variety of protein molecules where it has provided unique information about biopolymer folding, substrate binding, and catalysis. Here, we describe the application of Raman crystallography to functional RNA molecules. RNA represents unique opportunities and challenges for Raman crystallography. One issue that confounds studies of RNA is its tendency to adopt multiple non-functional folds. Raman crystallography has the advantage that it isolates a single state of the RNA within the crystal and can evaluate its fold, metal ion binding properties (ligand identity, stoichiometry, and affinity), proton binding properties (identity, stoichiometry, and affinity), and catalytic potential. In particular, base-specific stretches can be identified and then associated with the binding of metal ions and protons. Because measurements are carried out in the hanging drop at ambient, rather than cryo, conditions and because RNA crystals tend to be approximately 70% solvent, RNA dynamics and conformational changes become experimentally accessible. This review focuses on experimental setup and procedures, acquisition and interpretation of Raman data, and determination of physicochemical properties of the RNA. Raman crystallographic and solution biochemical experiments on the HDV RNA enzyme are summarized and found to be in excellent agreement. Remarkably, characterization of the crystalline state has proven to help rather than hinder functional characterization of functional RNA, most likely because the tendency of RNA to fold heterogeneously is limited in a crystalline environment. Future applications of Raman crystallography to RNA are briefly discussed.

  18. Portable raman explosives detection

    Energy Technology Data Exchange (ETDEWEB)

    Moore, David Steven [Los Alamos National Laboratory; Scharff, Robert J [Los Alamos National Laboratory

    2008-01-01

    Recent advances in portable Raman instruments have dramatically increased their application to emergency response and forensics, as well as homeland defense. This paper reviews the relevant attributes and disadvantages of portable Raman spectroscopy, both essentially and instrumentally, to the task of explosives detection in the field.

  19. Excited State Dynamics of γ-Crotonolactone:Resonance Raman Spectroscopy and Complete Active Space†Self-consistent Field(CASSCF) Study%γ-巴豆酰内酯激发态动力学的共振拉曼光谱和完全活性空间自洽场(CASSCF)计算研究

    Institute of Scientific and Technical Information of China (English)

    欧阳冰; 薛佳丹; 郑旭明

    2015-01-01

    The structural dynamics and decay mechanisms of γ-crotonolactone in the light-absorbing S2 excited states were studied by resonance Raman spectroscopy and complete active space self-consistent field(CASSCF) computations. The electronic spectra assignments and the vibrational assignments were done on the basis of the density-functional theory computations and the results of corresponding spectra. The reso-nance Raman spectra at four excitation wavelength which covered A-band were obtained. CASSCF method was carried out to determine the minimal excitation energies and excited geometries of S1,min , S2,min , T1,min , T2,min , T 3,min , as well as some conical intersection points. The relation between the structures of excited state S2,min as well as internal conversion point CI(S2 / S1 ) and the intensity mode of resonance Raman spectra was studied. The efficiency of various intersystem crossing is evaluated on the basis of the El-Sayed’s rule, and two major decay channels from S2,FC to ground state S0 were proposed. One is the internal conversion channel and the other is the intersystem crossing channel.%采用共振拉曼光谱和完全活性空间自洽场(CASSCF)方法研究了γ-巴豆酰内酯的光吸收 S2态的结构动力学和衰变机制。采用含时密度泛函理论方法结合光谱实验确认了紫外光谱和振动光谱。获得了涵盖A-带吸收的4个激发波长下的共振拉曼光谱。用 CASSCF 计算得到了 S1,min , S2,min , T1,min , T2,min和 T3,min及其相关势能面交叉点的结构与能量。研究了 A-带共振拉曼光谱强度模式与 S2,min和 CI(S2/ S1)交叉点结构的关系。借助 El-Sayed 规则分析了各系间窜跃路径的效率,提出了γ-巴豆酰内酯从 S2,FC弛豫到基态 S0的2条主要路径:内转换路径和系间窜跃路径。

  20. Continuous-wave Raman Lasing in Aluminum Nitride Microresonators

    CERN Document Server

    Liu, Xianwen; Xiong, Bing; Wang, Lai; Wang, Jian; Han, Yanjun; Hao, Zhibiao; Li, Hongtao; Luo, Yi; Yan, Jianchang; Wei, Tongbo; Zhang, Yun; Wang, Junxi

    2016-01-01

    We report the first investigation on continuous-wave Raman lasing in high-quality-factor aluminum nitride (AlN) microring resonators. Although wurtzite AlN is known to exhibit six Raman-active phonons, single-mode Raman lasing with low threshold and high slope efficiency is demonstrated. Selective excitation of A$_1^\\mathrm{TO}$ and E$_2^\\mathrm{high}$ phonons with Raman shifts of $\\sim$612 and 660 cm$^{-1}$ is observed by adjusting the polarization of the pump light. A theoretical analysis of Raman scattering efficiency within ${c}$-plane (0001) of AlN is carried out to help account for the observed lasing behavior. Bidirectional lasing is experimentally confirmed as a result of symmetric Raman gain in micro-scale waveguides. Furthermore, second-order Raman lasing with unparalleled output power of $\\sim$11.3 mW is obtained, which offers the capability to yield higher order Raman lasers for mid-infrared applications.

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

    CERN Document Server

    Ariunbold, Gombojav O

    2016-01-01

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

  2. The attosecond regime of impulsive stimulated electronic Raman excitation

    CERN Document Server

    Ware, Matthew R; Cryan, James P; Haxton, Daniel J

    2016-01-01

    We have calculated the resonant and nonresonant contributions to attosecond impulsive stimulated electronic Raman scattering (SERS) in regions of autoionizing transitions. Comparison with Multiconfiguration Time-Dependent Hartree-Fock (MCTDHF) calculations find that attosecond SERS is dominated by continuum transitions and not autoionizing resonances. These results agree quantitatively with a rate equation that includes second-order Raman and first-and second-order photoionization rates. Such rate models can be extended to larger molecular systems. Our results indicate that attosecond SERS transition probabilities may be understood in terms of two-photon generalized cross sections even in the high-intensity limit for extreme ultraviolet wavelengths.

  3. Raman spectroscopic determination of norbixin and tartrazine in sugar.

    Science.gov (United States)

    Uhlemann, Ute; Strelau, Katharina K; Weber, Karina; Da Costa Filho, Paulo Augusto; Rösch, Petra; Popp, Jürgen

    2012-08-01

    In this paper, a method for the detection of norbixin and tartrazine in sugar by means of resonance Raman spectroscopy is presented. The extraction was done in four steps using methanol and the measurements were performed in aqueous solution. The excitation wavelength was 514 nm for norbixin and 488 nm for tartrazine samples. The characteristic resonance Raman signals of the dyes were fitted by different functions. Depending on the R² values of the different fits, each spectrum was classified as positive or negative response. A detection limit of 250 ng g⁻¹ for norbixin and 989 ng g⁻¹ for tartrazine in solid sugar samples could be reached by logistic regression.

  4. Raman scattering in crystals

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, D.F.

    1988-09-30

    A tutorial presentation is given of Raman scattering in crystals. The physical concepts are emphasized rather than the detailed mathematical formalism. Starting with an introduction to the concepts of phonons and conservation laws, the effects of photon-phonon interactions are presented. This interaction concept is shown for a simple cubic crystal and is extended to a uniaxial crystal. The correlation table method is used for determining the number and symmetry of the Raman active modes. Finally, examples are given to illustrate the relative ease of using this group theoretical method and the predictions are compared with measured Raman spectra. 37 refs., 17 figs., 6 tabs.

  5. New Insight into Erythrocyte through In Vivo Surface-Enhanced Raman Spectroscopy

    DEFF Research Database (Denmark)

    Brazhe, Nadezda A.; Abdali, Salim; Brazhe, Alexey R.

    2009-01-01

    The article presents a noninvasive approach to the study of erythrocyte properties by means of a comparative analysis of signals obtained by surface-enhanced Raman spectroscopy (SERS) and resonance Raman spectroscopy (RS). We report step-by-step the procedure for preparing experimental samples co...

  6. Surface-enhanced Raman scattering on aluminum using near infrared and visible excitation

    DEFF Research Database (Denmark)

    Mogensen, Klaus Bo; Gühlke, Marina; Kneipp, Janina;

    2014-01-01

    We observed strong surface-enhanced Raman scattering on discontinuous nanostructured aluminum films using 785 nm excitation even though dielectric constants of this metal suggest plasmon supported spectroscopy in the ultraviolet range. The excitation of SERS correlates with plasmon resonances...

  7. Exploring many body interactions with Raman spectroscopy

    Science.gov (United States)

    Tian, Yao

    Many-body interactions are cornerstones of contemporary solid state physics research. Especially, phonon related interactions such as phonon-phonon coupling, spin-phonon coupling and electron-phonon coupling constantly present new challenges. To study phonon related many-body interactions, temperature dependent Raman spectroscopy is employed. Firstly, a new design and construction of a Raman microscope aimed at high collection eciency, positional and thermal stability is discussed. The application of the home-built Raman microscope is shown in the context of two types of novel materials; Cr2Ge2Te6 (spin-phonon coupling) and Bi2Te3-xSex (phonon-phonon coupling). Cr2Ge2Te6 is one of the rare class of ferromagnetic semiconductors and recent thermal transport studies suggest the spin and lattice are strongly coupled in its cousin compound Cr2Si2Te6. In this work, the spin-phonon coupling in Cr2Ge2Te6 has been revealed in multiple ways: we observed a split of two phonon modes due to the breaking of time reversal symmetry; the anomalous hardening of an additional three modes; and a dramatic enhancement of the phonon lifetimes. It is well-known that the phonon-phonon interaction plays a signicant role in determining the thermal transport properties of thermoelectrics. A comprehensive study of the phonon dynamics of Bi2Te3-xSex has been performed. We found that the unusual temperature dependence of dierent phonon modes originates from both cubic and quartic anharmonicity. These results are consistent with the resonance bonding mechanism, suggesting that the resonance bonding may be a common feature for conventional thermoelectrics. In the Raman spectra of Bi2Te2Se, the origin of the extra Raman feature has been debated for decades. Through a temperature dependent Raman study, we were able to prove the feature is generated by a Te-Se antisite induced local mode. The anomalous linewidth of the local mode as well as the anharmonic behavior were explained through a statistical

  8. Applications of Raman Spectroscopy to Inorganic Chemistry

    Institute of Scientific and Technical Information of China (English)

    RobinJHClarkFRS

    1995-01-01

    The renaissance in Raman spectroscopy some 25-30 years ago had particular and immediate impact on Inorganic Chemistry,viz in areas such as the study of deeply coloued compounds,structural changes on change of state,equilibria,vapour phase band contour analysis,Raman band intensities and the nature of the chemical bond,metal-metal bonding,species in melts,identification of species in solution and of radicals by time-resolved techniques,in bioinorganic chemistry,and of linear-chain semiconductors.More recently,much attention has been directed at the quantitative level at the evaluation of geometric changes in molecules on excitation by resonance Raman spectroscopy.At the qualitative level Raman microscopy is now recognised to be the most effective technique for the identification of pigments-particularly the inorganic ones-on medieval manuscripts and especially of the components(down to grain sizes of -1 um)of pigment mixtures,It is thus a very important technique at the Arts/Science borderling in conservation science.

  9. Shining light on neurosurgery diagnostics using Raman spectroscopy.

    Science.gov (United States)

    Broadbent, Brandy; Tseng, James; Kast, Rachel; Noh, Thomas; Brusatori, Michelle; Kalkanis, Steven N; Auner, Gregory W

    2016-10-01

    Surgical excision of brain tumors provides a means of cytoreduction and diagnosis while minimizing neurologic deficit and improving overall survival. Despite advances in functional and three-dimensional stereotactic navigation and intraoperative magnetic resonance imaging, delineating tissue in real time with physiological confirmation is challenging. Raman spectroscopy is a promising investigative and diagnostic tool for neurosurgery, which provides rapid, non-destructive molecular characterization in vivo or in vitro for biopsy, margin assessment, or laboratory uses. The Raman Effect occurs when light temporarily changes a bond's polarizability, causing change in the vibrational frequency, with a corresponding change in energy/wavelength of the scattered photon. The recorded inelastic scattering results in a "fingerprint" or Raman spectrum of the constituent under investigation. The amount, location, and intensity of peaks in the fingerprint vary based on the amount of vibrational bonds in a molecule and their ensemble interactions with each other. Distinct differences between various pathologic conditions are shown as different intensities of the same peak, or shifting of a peak based on the binding conformation. Raman spectroscopy has potential for integration into clinical practice, particularly in distinguishing normal and diseased tissue as an adjunct to standard pathologic diagnosis. Further, development of fiber-optic Raman probes that fit through the instrument port of a standard endoscope now allows researchers and clinicians to utilize spectroscopic information for evaluation of in vivo tissue. This review highlights the need for such an instrument, summarizes neurosurgical Raman work performed to date, and discusses the future applications of neurosurgical Raman spectroscopy.

  10. Stimulated Raman Scattering in Nanorod Silicon Carbide Films

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    When the film is excited by a very low excitation energy, the spontaneous Raman scattering emerges. The intensity of Raman scattering is proportional to the excitation power below the threshold excitation. When the excited power reaches the excitation threshold, the intensity of Stokes light strongly increases. Meanwhile an anti-Stokes light at 495nm and multiple order but small Stokes peaks occur. The intensity of Stokes light is much larger than that of anti-Stokes. The full width of half maximum (FWHM) of Stokes peak is reduced from 0.4nm to less than 0.2nm, the scattering angle between both Stokes and incident lights becomes less than 1°, and the angle between the Stokes and anti-Stokes lights is about 3°. When the exciting power is in excess of the threshold, anti-Stokes and multiple Raman scattering peaks reappear. These experiments can be unlimitedly repeated. From this experiment, we can exclude the possibility of spontaneous Raman scattering. It is suggested that the nanorods are a quantum line dimension having a large surface. There will be Raman differential scattering section so long as the nanorod films become very strong scattering media; the surface-enhanced Raman scattering will be produced, the nanorod films of SiC will form a strong multiple scattering resonance cavities so as to form the stimulated Raman scattering oscillation.

  11. Engineering Plasmonic Nanopillar Arrays for Surface-enhanced Raman Spectroscopy

    DEFF Research Database (Denmark)

    Wu, Kaiyu

    This Ph.D. thesis presents (i) an in-depth understanding of the localized surface plasmon resonances (LSPRs) in the nanopillar arrays (NPs) for surface-enhanced Raman spectroscopy (SERS), and (ii) systematic ways of optimizing the fabrication process of NPs to improve their SERS efficiencies. Thi...

  12. Raman microscopy investigation of beryllium materials

    Science.gov (United States)

    Pardanaud, C.; Rusu, M. I.; Giacometti, G.; Martin, C.; Addab, Y.; Roubin, P.; Lungu, C. P.; Porosnicu, C.; Jepu, I.; Dinca, P.; Lungu, M.; Pompilian, O. G.; Mateus, R.; Alves, E.; Rubel, M.; contributors, JET

    2016-02-01

    We report for the first time on the ability of Raman microscopy to give information on the structure and composition of Be related samples mimicking plasma facing materials that will be found in ITER. For that purpose, we investigate two types of material. First: Be, W, Be1W9, and Be5W5 deposits containing a few percents of D or N, and second: a Mo mirror exposed to plasma in the main JET chamber (in the framework of the first mirror test in JET with ITER-like wall). We performed atomic quantifications using ion beam analysis for the first samples. We also did atomic force microscopy. We found defect induced Raman bands in Be, Be1W9, and Be5W5 deposits. Molybdenum oxide has been identified showing an enhancement due to a resonance effect in the UV domain.

  13. Raman spectra of nitrogen-doped tetrahedral amorphous carbon from first principles

    Institute of Scientific and Technical Information of China (English)

    NIU Li; ZHU JiaQi; GAO Wei; HAN Xiao; DU ShanYi

    2009-01-01

    The non-resonant vibrational Raman spectra of nitrogen-doped tetrahedral amorphous carbon have been calculated from first principles, including the generation of s structural model, and the calculation of vibrational frequencies, vibrational eigenmodes and Raman coupling tensors. The calculated Raman spectra are in good agreement with the experimental results. The broad band at around 500 cm~(-1) arises from mixed bonds. The T peak originates from the vibrations of sp~3 carbon and the G peak comes from the stretching vibrations of sp~2-type bonding of C=C and C=N. The simulation results indicate the direct contribution of N vibrations to Raman spectra.

  14. Polarized multiplex coherent anti-Stokes Raman scattering using a picosecond laser and a fiber supercontinuum.

    Science.gov (United States)

    Michel, Sébastien; Courjaud, Antoine; Mottay, Eric; Finot, Christophe; Dudley, John; Rigneault, Hervé

    2011-02-01

    We perform multiplex coherent anti-Stokes Raman scattering (CARS) micro-spectroscopy with a picosecond pulsed laser and a broadband supercontinuum (SC) generated in photonic crystal fiber. CARS signal stability is achieved using an active fiber coupler that avoids thermal and mechanical drifts. We obtain multiplex CARS spectra for test liquids in the 600-2000 cm(-1) spectral range. In addition we investigate the polarization dependence of the CARS spectra when rotating the pump beam linear polarization state relative to the linearly polarized broad stokes SC. From these polarization measurements we deduce the Raman depolarization ratio, the resonant versus nonresonant contribution, the Raman resonance frequency, and the linewidth.

  15. Raman and surface enhanced Raman spectroscopic investigation on Lamiaceae plants

    Science.gov (United States)

    Rösch, P.; Popp, J.; Kiefer, W.

    1999-05-01

    The essential oils of Thymus vulgaris and Origanum vulgaris are studied by means of micro-Raman spectroscopy. The containing monoterpenes can be identified by their Raman spectra. Further the essential oils are investigated in their natural environment, the so-called oil cells of these Lamiaceae plants, with surface enhanced Raman spectroscopy (SERS). This method has the advantage to enhance Raman signals and furthermore the SERS effect leads to fluorescence quenching.

  16. Raman spectrum of asphaltene

    KAUST Repository

    Abdallah, Wael A.

    2012-11-05

    Asphaltenes extracted from seven different crude oils representing different geological formations from around the globe were analyzed using the Raman spectroscopic technique. Each spectrum is fitted with four main peaks using the Gaussian function. On the basis of D1 and G bands of the Raman spectrum, asphaltene indicated an ordered structure with the presence of boundary defected edges. The average aromatic sheet size of the asphaltene molecules is estimated within the range of 1.52-1.88 nm, which represents approximately seven to eight aromatic fused rings. This estimation is based on the integrated intensity of D1 and G bands, as proposed by Tunistra and Koenig. The results here are in perfect agreement with so many other used techniques and indicate the potential applicability of Raman measurements to determine the average aromatic ring size and its boundary. © 2012 American Chemical Society.

  17. Raman fiber lasers

    Science.gov (United States)

    Supradeepa, V. R.; Feng, Yan; Nicholson, Jeffrey W.

    2017-02-01

    High-power fiber lasers have seen tremendous development in the last decade, with output powers exceeding multiple kilowatts from a single fiber. Ytterbium has been at the forefront as the primary rare-earth-doped gain medium owing to its inherent material advantages. However, for this reason, the lasers are largely confined to the narrow emission wavelength region of ytterbium. Power scaling at other wavelength regions has lagged significantly, and a large number of applications rely upon the diversity of emission wavelengths. Currently, Raman fiber lasers are the only known wavelength agile, scalable, high-power fiber laser technology that can span the wavelength spectrum. In this review, we address the technology of Raman fiber lasers, specifically focused on the most recent developments. We will also discuss several applications of Raman fiber lasers in laser pumping, frequency conversion, optical communications and biology.

  18. Raman spectroscopy in astrobiology.

    Science.gov (United States)

    Jorge Villar, Susana E; Edwards, Howell G M

    2006-01-01

    Raman spectroscopy is proposed as a valuable analytical technique for planetary exploration because it is sensitive to organic and inorganic compounds and able to unambiguously identify key spectral markers in a mixture of biological and geological components; furthermore, sample manipulation is not required and any size of sample can be studied without chemical or mechanical pretreatment. NASA and ESA are considering the adoption of miniaturised Raman spectrometers for inclusion in suites of analytical instrumentation to be placed on robotic landers on Mars in the near future to search for extinct or extant life signals. In this paper we review the advantages and limitations of Raman spectroscopy for the analysis of complex specimens with relevance to the detection of bio- and geomarkers in extremophilic organisms which are considered to be terrestrial analogues of possible extraterrestial life that could have developed on planetary surfaces.

  19. The Discovery of Raman Scattering in HII Regions

    CERN Document Server

    Dopita, Michael A; Sutherland, Ralph S; Kewley, Lisa J; Groves, Brent A

    2016-01-01

    We report here on the discovery of faint extended wings of H\\alpha\\ observed out to an apparent velocity of ~ 7600 km/s in the Orion Nebula (M42) and in five HII regions in the Large and the Small Magellanic Clouds. We show that, these wings are caused by Raman scattering of both the O I and Si II resonance lines and stellar continuum UV photons with H I followed by radiative decay to the H I n=2 level. The broad wings also seen in H\\beta\\ and in H\\gamma\\ result from Raman scattering of the UV continuum in the H I n=4 and n=5 levels respectively.The Raman scattering fluorescence is correlated with the intensity of the narrow permitted lines of O I and Si II. In the case of Si II, this is explained by radiative pumping of the same 1023.7\\AA\\ resonance line involved in the Raman scattering by the Ly\\beta\\ radiation field. The subsequent radiative cascade produces enhanced Si II 5978.9, 6347.1$ and 6371.4\\AA\\ permitted transitions. Finally we show that in O I, radiative pumping of the 1025.76\\AA\\ resonance line ...

  20. Potential of Raman and Infrared Spectroscopy for Plant Analysis

    Science.gov (United States)

    Schulz, H.

    2008-11-01

    Various mid-infrared (MIR) and Raman spectroscopic methods applied to the analysis of valuable plant substances or quality parameters in selected horticultural and agricultural crops are presented. Generally, both spectroscopy techniques allow to identify simultaneously characteristic key bands of individual plant components (e.g. carotenoids, alkaloids, polyacetylenes, fatty acids, amino acids, terpenoids). In contrast to MIR methods Raman spectroscopy mostly does not need any sample pre-treatment; even fresh plant material can be analysed without difficulty because water shows only weak Raman scattering properties. In some cases a significant sensivity enhancement of Raman signals can be achieved if the exciting laser wavelength is adjusted to the absorption range of particular plant chromophores such as carotenoids (Resonance Raman effect). Applying FT-IR or FT Raman micro-spectroscopy the distribution of certain plant constituents in the cell wall can be identified without the need for any physical separation. Furthermore it is also possible to analyse secondary metabolites occurring in the cell vacuoles if significant key bands do not coincide with the spectral background of the plant matrix.

  1. Raman Imaging Techniques and Applications

    CERN Document Server

    2012-01-01

    Raman imaging has long been used to probe the chemical nature of a sample, providing information on molecular orientation, symmetry and structure with sub-micron spatial resolution. Recent technical developments have pushed the limits of micro-Raman microscopy, enabling the acquisition of Raman spectra with unprecedented speed, and opening a pathway to fast chemical imaging for many applications from material science and semiconductors to pharmaceutical drug development and cell biology, and even art and forensic science. The promise of tip-enhanced raman spectroscopy (TERS) and near-field techniques is pushing the envelope even further by breaking the limit of diffraction and enabling nano-Raman microscopy.

  2. Theory for the Acoustic Raman Modes of Proteins

    CERN Document Server

    DeWolf, Timothy

    2016-01-01

    We present a theoretical analysis that associates the resonances of extraordinary acoustic Raman (EAR) spectroscopy [Wheaton et al., Nat Photon 9, 68 (2015)] with the collective modes of proteins. The theory uses the anisotropic elastic network model to find the protein acoustic modes, and calculates Raman intensity by treating the protein as a polarizable ellipsoid. Reasonable agreement is found between EAR spectra and our theory. Protein acoustic modes have been extensively studied theoretically to assess the role they play in protein function; this result suggests EAR as a new experimental tool for studies of protein acoustic modes.

  3. High-pressure Raman study of Terephthalonitrile

    Science.gov (United States)

    Li, DongFei; Zhang, KeWei; Song, MingXing; Zhai, NaiCui; Sun, ChengLin; Li, HaiBo

    2017-02-01

    The in situ high-pressure Raman spectra of Terephthalonitrile (TPN) have been investigated from ambient to 12.6 GPa at room temperature. All the fundamental vibrational modes of TPN at ambient were assigned based on the first-principle calculations. A detailed Raman spectroscopy analysis revealed that TPN underwent a phase transition at 5.3 GPa. The frequencies of the TPN Raman peaks increase with increasing the pressure which can be attributed to the reduction in the interatomic distances and the escalation of effective force constants. The intensity of the C-C-C ring-out-plane deformation mode increases gradually as the frequency remains almost constant during the compression which can be explained by the existence of π-π interactions in TPN molecules. Additionally, the pressure-induced structural changes of TPN on the Fermi resonance between the C ≡ N out-of-plane vibration mode and the C - CN out-of-plane vibration mode have been analyzed.

  4. Raman spectroscopy an intensity approach

    CERN Document Server

    Guozhen, Wu

    2017-01-01

    This book summarizes the highlights of our work on the bond polarizability approach to the intensity analysis. The topics covered include surface enhanced Raman scattering, Raman excited virtual states and Raman optical activity (ROA). The first chapter briefly introduces the Raman effect in a succinct but clear way. Chapter 2 deals with the normal mode analysis. This is a basic tool for our work. Chapter 3 introduces our proposed algorithm for the Raman intensity analysis. Chapter 4 heavily introduces the physical picture of Raman virtual states. Chapter 5 offers details so that the readers can have a comprehensive idea of Raman virtual states. Chapter 6 demonstrates how this bond polarizability algorithm is extended to ROA intensity analysis. Chapters 7 and 8 offer details on ROA, showing many findings on ROA mechanism that were not known or neglected before. Chapter 9 introduces our proposed classical treatment on ROA which, as combined with the results from the bond polarizability analysis, leads to a com...

  5. Surface enhanced Raman scattering

    CERN Document Server

    Furtak, Thomas

    1982-01-01

    In the course of the development of surface science, advances have been identified with the introduction of new diagnostic probes for analytical characterization of the adsorbates and microscopic structure of surfaces and interfaces. Among the most recently de­ veloped techniques, and one around which a storm of controversy has developed, is what has now been earmarked as surface enhanced Raman scattering (SERS). Within this phenomenon, molecules adsorbed onto metal surfaces under certain conditions exhibit an anomalously large interaction cross section for the Raman effect. This makes it possible to observe the detailed vibrational signature of the adsorbate in the ambient phase with an energy resolution much higher than that which is presently available in electron energy loss spectroscopy and when the surface is in contact with a much larger amount of material than that which can be tolerated in infrared absorption experiments. The ability to perform vibrational spectroscopy under these conditions would l...

  6. Diamagnetic Raman Optical Activity of Chlorine, Bromine, and Iodine Gases.

    Science.gov (United States)

    Šebestík, Jaroslav; Kapitán, Josef; Pačes, Ondřej; Bouř, Petr

    2016-03-01

    Magnetic Raman optical activity of gases provides unique information about their electric and magnetic properties. Magnetic Raman optical activity has recently been observed in a paramagnetic gas (Angew. Chem. Int. Ed. 2012, 51, 11058; Angew. Chem. 2012, 124, 11220). In diamagnetic molecules, it has been considered too weak to be measurable. However, in chlorine, bromine and iodine vapors, we could detect a significant signal as well. Zeeman splitting of electronic ground-state energy levels cannot rationalize the observed circular intensity difference (CID) values of about 10(-4). These are explicable by participation of paramagnetic excited electronic states. Then a simple model including one electronic excited state provides reasonable spectral intensities. The results suggest that this kind of scattering by diamagnetic molecules is a general event observable under resonance conditions. The phenomenon sheds new light on the role of excited states in the Raman scattering, and may be used to probe molecular geometry and electronic structure.

  7. Optimally shaped narrowband picosecond pulses for femtosecond stimulated Raman spectroscopy.

    Science.gov (United States)

    Hoffman, David P; Valley, David; Ellis, Scott R; Creelman, Mark; Mathies, Richard A

    2013-09-09

    A comparison between a Fabry-Pérot etalon filter and a conventional grating filter for producing the picosecond (ps) Raman pump pulses for femtosecond stimulated Raman spectroscopy (FSRS) is presented. It is shown that for pulses of equal energy the etalon filter produces Raman signals twice as large as that of the grating filter while suppressing the electronically resonant background signal. The time asymmetric profile of the etalon-generated pulse is shown to be responsible for both of these observations. A theoretical discussion is presented which quantitatively supports this hypothesis. It is concluded that etalons are the ideal method for the generation of narrowband ps pulses for FSRS because of the optical simplicity, efficiency, improved FSRS intensity and reduced backgrounds.

  8. Raman Scattering of Inorganic Fibers

    OpenAIRE

    1985-01-01

    We have examined evolution of Raman spectra of carbon fibers and SiC fibers through structural transformations caused by heat treatment. Raman spectra of the SiC fibers indicate that the fibers consist of amorphous or microcrystalline SiC and graphitic microcrystals. We discuss the correlation between the tensile strength of the fibers and their microscopic structure deduced from the Raman data.

  9. Practical Raman spectroscopy an introduction

    CERN Document Server

    Vandenabeele, Peter

    2013-01-01

    This text offers an open-learning approach to Raman spectroscopy providing detail on instrumentation, applications and discussions questions throughout the book. It provides a valuable guide to assist with teaching Raman spectroscopy which is gaining attention in (analytical) chemistry, and as a consequence, teaching programs have followed. Today, education in Raman spectroscopy is often limited to theoretical aspects (e.g. selection rules), but practical aspects are usually disregarded. With these course notes, the author hopes to fill this gap and include information about Raman instrumentat

  10. [Research Progress of Raman Spectroscopy on Dyestuff Identification of Ancient Relics and Artifacts].

    Science.gov (United States)

    He, Qiu-ju; Wang, Li-qin

    2016-02-01

    As the birthplace of Silk Road, China has a long dyeing history. The valuable information about the production time, the source of dyeing material, dyeing process and preservation status were existed in organic dyestuff deriving from cultural relics and artifacts. However, because of the low contents, complex compositions and easily degraded of dyestuff, it is always a challenging task to identify the dyestuff in relics analyzing field. As a finger-print spectrum, Raman spectroscopy owns unique superiorities in dyestuff identification. Thus, the principle, characteristic, limitation, progress and development direction of micro-Raman spectroscopy (MRS/µ-Raman), near infrared reflection and Fourier transform Raman spectroscopy (NIR-FT-Raman), surface-enhanced Raman spectroscopy (SERS) and resonance raman spectroscopy (RRS) have been introduced in this paper. Furthermore, the features of Raman spectra of gardenia, curcumin and other natural dyestuffs were classified by MRS technology, and then the fluorescence phenomena of purpurin excitated with different wavelength laser was compared and analyzed. At last, gray green silver colloidal particles were made as the base, then the colorant of madder was identified combining with thin layer chromatography (TLC) separation technology and SERS, the result showed that the surface enhancement effect of silver colloidal particles could significantly reduce fluorescence background of the Raman spectra. It is pointed out that Raman spectroscopy is a rapid and convenient molecular structure qualitative methodology, which has broad application prospect in dyestuff analysis of cultural relics and artifacts. We propose that the combination of multi-Raman spectroscopy, separation technology and long distance transmission technology are the development trends of Raman spectroscopy.

  11. Raman-Suppressing Coupling for Optical Parametric Oscillator

    Science.gov (United States)

    Savchenkov, Anatoliy; Maleki, Lute; Matsko, Andrey; Rubiola, Enrico

    2007-01-01

    A Raman-scattering-suppressing input/ output coupling scheme has been devised for a whispering-gallery-mode optical resonator that is used as a four-wave-mixing device to effect an all-optical parametric oscillator. Raman scattering is undesired in such a device because (1) it is a nonlinear process that competes with the desired nonlinear four-wave conversion process involved in optical parametric oscillation and (2) as such, it reduces the power of the desired oscillation and contributes to output noise. The essence of the present input/output coupling scheme is to reduce output loading of the desired resonator modes while increasing output loading of the undesired ones.

  12. Time-dependent micro-Raman scattering studies of polyvinyl alcohol and silver nitrate thin films

    Indian Academy of Sciences (India)

    K Shadak Alee; D Narayana Rao

    2014-02-01

    In-situ monitoring of silver nanoparticle formation was studied in thin films of polyvinyl alcohol and silver nitrate. We proposed the observation of surface-enhanced Raman spectroscopy (SERS) as a novel and simple technique to record the growth of silver nanoparticles in polyvinyl alcohol thin films. Observed enhancement in the Raman bands of polyvinyl alcohol is explained through the localized surface plasmon resonance of silver nanoparticles. Influence of temperature generated by silver nanoparticles on the formation of nanoparticles is also discussed.

  13. Raman amplification in optical communication systems

    DEFF Research Database (Denmark)

    Kjær, Rasmus

    2008-01-01

    Fiber Raman amplifiers are investigated with the purpose of identifying new applications and limitations for their use in optical communication systems. Three main topics are investigated, namely: New applications of dispersion compensating Raman amplifiers, the use Raman amplification to increase...

  14. Simple Raman instrument for in vivo detection of macular pigments.

    Science.gov (United States)

    Ermakov, Igor V; Ermakova, Maia R; Gellermann, Werner

    2005-07-01

    Raman spectroscopy holds promise as a novel noninvasive technology for the quantification of the macular pigments (MP) lutein and zeaxanthin. These compounds, which are members of the carotenoid family, are thought to prevent or delay the onset of age-related macular degeneration, the leading cause of irreversible blindness in the elderly. It is highly likely that they achieve this protection through their function as optical filters and/or antioxidants. Using resonant excitation in the visible region, we measure and quantify the Raman signals that originate from the carbon double bond (C=C) stretch vibrations of the pi-conjugated molecule backbone. In this manuscript we describe the construction and performance of a novel compact MP Raman instrument utilizing dielectric angle-tuned band-pass filters for wavelength selection and a single-channel photo-multiplier for the detection of MP Raman responses. MP concentration measurements are fast and accurate, as seen in our experiments with model eyes and living human eyes. The ease and rapidity of Raman MP measurements, the simplicity of the instrumentation, the high accuracy of the measurements, and the lack of significant systematic errors should make this technology attractive for widespread clinical research.

  15. Cell Imaging by Spontaneous and Amplified Raman Spectroscopies

    Directory of Open Access Journals (Sweden)

    Giulia Rusciano

    2017-01-01

    Full Text Available Raman spectroscopy (RS is a powerful, noninvasive optical technique able to detect vibrational modes of chemical bonds. The high chemical specificity due to its fingerprinting character and the minimal requests for sample preparation have rendered it nowadays very popular in the analysis of biosystems for diagnostic purposes. In this paper, we first discuss the main advantages of spontaneous RS by describing the study of a single protozoan (Acanthamoeba, which plays an important role in a severe ophthalmological disease (Acanthamoeba keratitis. Later on, we point out that the weak signals that originated from Raman scattering do not allow probing optically thin samples, such as cellular membrane. Experimental approaches able to overcome this drawback are based on the use of metallic nanostructures, which lead to a huge amplification of the Raman yields thanks to the excitation of localized surface plasmon resonances. Surface-enhanced Raman scattering (SERS and tip-enhanced Raman scattering (TERS are examples of such innovative techniques, in which metallic nanostructures are assembled on a flat surface or on the tip of a scanning probe microscope, respectively. Herein, we provide a couple of examples (red blood cells and bacterial spores aimed at studying cell membranes with these techniques.

  16. Enhanced Raman scattering of biological molecules

    Science.gov (United States)

    Montoya, Joseph R.

    The results presented in this thesis, originate from the aspiration to develop an identification algorithm for Salmonella enterica Serovar Enteritidis (S. enterica), Escherichia coli (E. coli), Bacillus globigii ( B. globigii), and Bacillus megaterium ( B. megaterium) using "enhanced" Raman scattering. We realized our goal, with a method utilizing an immunoassay process in a spectroscopic technique, and the direct use of the enhanced spectral response due to bacterial surface elements. The enhanced Raman signal originates from Surface Enhanced Raman Scattering (SERS) and/or Morphological Dependent Resonances (MDR's). We utilized a modified Lee-Meisel colloidal production method to produce a SERS active substrate, which was applied to a SERS application for the amino acid Glycine. The comparison indicates that the SERS/FRACTAL/MDR process can produce an increase of 107 times more signal than the bulk Raman signal from Glycine. In the extension of the Glycine results, we studied the use of SERS related to S. enterica, where we have shown that the aromatic amino acid contribution from Phenylalanine, Tyrosine, and Tryptophan produces a SERS response that can be used to identify the associated SERS vibrational modes of a S. enterica one or two antibody complexes. The "fingerprint" associated with the spectral signature in conjunction with an enhanced Raman signal allows conclusions to be made: (1) about the orientation of the secondary structure on the metal; (2) whether bound/unbound antibody can be neglected; (3) whether we can lower the detection limit. We have lowered the detection limit of S. enterica to 106 bacteria/ml. We also show a profound difference between S. enterica and E. coli SERS spectra even when there exists non-specific binding on E. coli indicating a protein conformation change induced by the addition of the antigen S. enterica. We confirm TEM imagery data, indicating that the source of the aromatic amino acid SERS response is originating from

  17. Simple Raman Instrument for in Vivo Detection of Macular Pigments

    OpenAIRE

    Ermakov, Igor V.; Ermakova, Maia R.; Gellermann, Werner

    2005-01-01

    Raman spectroscopy holds promise as a novel noninvasive technology for the quantification of the macular pigments (MP) lutein and zeaxanthin. These compounds, which are members of the carotenoid family, are thought to prevent or delay the onset of age-related macular degeneration, the leading cause of irreversible blindness in the elderly. It is highly likely that they achieve this protection through their function as optical filters and/or antioxidants. Using resonant excitation in the visib...

  18. Spatial resolution of tip-enhanced Raman spectroscopy - DFT assessment of the chemical effect.

    Science.gov (United States)

    Latorre, Federico; Kupfer, Stephan; Bocklitz, Thomas; Kinzel, Daniel; Trautmann, Steffen; Gräfe, Stefanie; Deckert, Volker

    2016-05-21

    Experimental evidence of extremely high spatial resolution of tip-enhanced Raman scattering (TERS) has been recently demonstrated. Here, we present a full quantum chemical description (at the density functional level of theory) of the non-resonant chemical effects on the Raman spectrum of an adenine molecule mapped by a tip, modeled as a single silver atom or a small silver cluster. We show pronounced changes in the Raman pattern and its intensities depending on the conformation of the nanoparticle-substrate system, concluding that the spatial resolution of the chemical contribution of TERS can be in the sub-nm range.

  19. Feshbach-enhancement of Raman photoassociation in a Bose-Einstein condensate

    CERN Document Server

    Mackie, Matt; Boyce, Heather; Shinn, Mannix; Katz, Lev

    2011-01-01

    We model the formation of stable heteronuclear molecules via pulsed Raman photoassociation of a two-component Bose-Einstein condensate near a strong Feshbach resonance, for both counterintuitive and intuitive pulse sequencing. Compared to lasers alone, weak Raman photoassociation is enhanced by as much as a factor of ten (five) for a counterintuitive (intuitive) pulse sequence, whereas strong Raman photoassociation is barely enhanced at all--regardless of pulse sequence. Stronger intra-atom, molecule, or atom-molecule collisions lead to an expected decrease in conversion efficiency, but stronger ambient inter-atom collisions lead to an unexpected increase in the efficiency of stable molecule production.

  20. Noninvasive laser Raman detection of carotenoid antioxidants in living human skin

    Science.gov (United States)

    Gellermann, Werner; Ermakov, Igor V.; Ermakova, Maia R.; McClane, Robert W.

    2001-05-01

    We have used resonance Raman scattering as a novel non- invasive optical technology to measure carotenoid antioxidants in human skin of healthy volunteers. Using blue-green laser excitation, clearly distinguishable carotenoid Raman spectra are obtained which are superimposed on a large skin autofluorescence background. The Raman spectra are obtained rapidly, i.e. within about 30 seconds, and the required laser light exposure levels are well within safety standards. Our technique can be used for rapid screening of carotenoid antioxidant levels in large populations and may have applications for assessing the risk for cutaneous diseases.

  1. Raman Tweezers as a Diagnostic Tool of Hemoglobin-Related Blood Disorders

    Directory of Open Access Journals (Sweden)

    Giulia Rusciano

    2008-12-01

    Full Text Available This review presents the development of a Raman Tweezers system for detecting hemoglobin-related blood disorders at a single cell level. The study demonstrates that the molecular fingerprint insight provided by Raman analysis holds great promise for distinguishing between healthy and diseased cells in the field of biomedicine. Herein a Raman Tweezers system has been applied to investigate the effects of thalassemia, a blood disease quite diffuse in the Mediterranean Sea region. By resonant excitation of hemoglobin Raman bands, we examined the oxygenation capability of normal, alpha- and beta-thalassemic erythrocytes. A reduction of this fundamental red blood cell function, particularly severe for beta-thalassemia, has been found. Raman spectroscopy was also used to draw hemoglobin distribution inside single erythrocytes; the results confirmed the characteristic anomaly (target shape, occurring in thalassemia and some other blood disorders. The success of resonance Raman spectroscopy for thalassemia detection reported in this review provide an interesting starting point to explore the application of a Raman Tweezers system in the analysis of several blood disorders.

  2. Shape-dependent surface-enhanced Raman scattering in gold-Raman probe-silica sandwiched nanoparticles for biocompatible applications.

    Science.gov (United States)

    Li, Ming; Cushing, Scott K; Zhang, Jianming; Lankford, Jessica; Aguilar, Zoraida P; Ma, Dongling; Wu, Nianqiang

    2012-03-23

    To meet the requirement of Raman probes (labels) for biocompatible applications, a synthetic approach has been developed to sandwich the Raman-probe (malachite green isothiocyanate, MGITC) molecules between the gold core and the silica shell in gold-SiO₂ composite nanoparticles. The gold-MGITC-SiO₂ sandwiched structure not only prevents the Raman probe from leaking out but also improves the solubility of the nanoparticles in organic solvents and in aqueous solutions even with high ionic strength. To amplify the Raman signal, three types of core, gold nanospheres, nanorods and nanostars, have been chosen as the substrates of the Raman probe. The effect of the core shape on the surface-enhanced Raman scattering (SERS) has been investigated. The colloidal nanostars showed the highest SERS enhancement factor while the nanospheres possessed the lowest SERS activity under excitation with 532 and 785 nm lasers. Three-dimensional finite-difference time domain (FDTD) simulation showed significant differences in the local electromagnetic field distributions surrounding the nanospheres, nanorods, and nanostars, which were induced by the localized surface plasmon resonance (LSPR). The electromagnetic field was enhanced remarkably around the two ends of the nanorods and around the sharp tips of the nanostars. This local electromagnetic enhancement made the dominant contribution to the SERS enhancement. Both the experiments and the simulation revealed the order nanostars > nanorods > nanospheres in terms of the enhancement factor. Finally, the biological application of the nanostar-MGITC-SiO₂ nanoparticles has been demonstrated in the monitoring of DNA hybridization. In short, the gold–MGITC-SiO₂ sandwiched nanoparticles can be used as a Raman probe that features high sensitivity, good water solubility and stability, low-background fluorescence, and the absence of photobleaching for future biological applications.

  3. Anomalous lattice vibrations of monolayer MoS 2 probed by ultraviolet Raman scattering

    KAUST Repository

    Liu, Hsiang Lin

    2015-01-01

    We present a comprehensive Raman scattering study of monolayer MoS2 with increasing laser excitation energies ranging from the near-infrared to the deep-ultraviolet. The Raman scattering intensities from the second-order phonon modes are revealed to be enhanced anomalously by only the ultraviolet excitation wavelength 354 nm. We demonstrate theoretically that such resonant behavior arises from a strong optical absorption that forms near the Γ point and of the band structure and an inter-valley resonant electronic scattering by the M-point phonons. These results advance our understanding of the double resonance Raman scattering process in low-dimensional semiconducting nanomaterials and provide a foundation for the technological development of monolayer MoS2 in the ultraviolet frequency range. © the Owner Societies 2015.

  4. Isotopic gas analysis through Purcell cavity enhanced Raman scattering

    Science.gov (United States)

    Petrak, B.; Cooper, J.; Konthasinghe, K.; Peiris, M.; Djeu, N.; Hopkins, A. J.; Muller, A.

    2016-02-01

    Purcell enhanced Raman scattering (PERS) by means of a doubly resonant Fabry-Perot microcavity (mode volume ≈ 100 μm3 and finesse ≈ 30 000) has been investigated as a technique for isotopic ratio gas analysis. At the pump frequency, the resonant cavity supports a buildup of circulating power while simultaneously enabling Purcell spontaneous emission rate enhancement at the resonant Stokes frequency. The three most common isotopologues of CO2 gas were quantified, and a signal was obtained from 13C16O2 down to a partial pressure of 2 Torr. Due to its small size and low pump power needed (˜10 mW) PERS lends itself to miniaturization. Furthermore, since the cavity is resonant with the emission frequency, future improvements could allow it to serve as its own spectral analyzer and no separate spectroscopic device would be needed.

  5. Diffusion measurements by Raman spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Shapiro, Alexander; Berg, Rolf W.;

    Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt......Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt...

  6. All-Fiber Raman Probe

    DEFF Research Database (Denmark)

    Brunetti, Anna Chiara

    The design and development of an all-in-fiber probe for Raman spectroscopy are presented in this Thesis. Raman spectroscopy is an optical technique able to probe a sample based on the inelastic scattering of monochromatic light. Due to its high specificity and reliability and to the possibility...... for the realization of flexible and minimally-invasive devices, able to reach remote or hardly accessible samples, and to perform in-situ analyses in hazardous environments. The work behind this Thesis focuses on the proof-of-principle demonstration of a truly in-fiber Raman probe, where all parts are realized...... to perform real-time measurements with little or no sample preparation, Raman spectroscopy is now considered an invaluable analytical tool, finding application in several fields including medicine, defense and process control. When combined with fiber optics technology, Raman spectroscopy allows...

  7. Raman Spectroscopy for Clinical Oncology

    Directory of Open Access Journals (Sweden)

    Michael B. Fenn

    2011-01-01

    Full Text Available Cancer is one of the leading causes of death throughout the world. Advancements in early and improved diagnosis could help prevent a significant number of these deaths. Raman spectroscopy is a vibrational spectroscopic technique which has received considerable attention recently with regards to applications in clinical oncology. Raman spectroscopy has the potential not only to improve diagnosis of cancer but also to advance the treatment of cancer. A number of studies have investigated Raman spectroscopy for its potential to improve diagnosis and treatment of a wide variety of cancers. In this paper the most recent advances in dispersive Raman spectroscopy, which have demonstrated promising leads to real world application for clinical oncology are reviewed. The application of Raman spectroscopy to breast, brain, skin, cervical, gastrointestinal, oral, and lung cancers is reviewed as well as a special focus on the data analysis techniques, which have been employed in the studies.

  8. Blood analysis by Raman spectroscopy

    Science.gov (United States)

    Enejder, Annika M. K.; Koo, Tae-Woong; Oh, Jeankun; Hunter, Martin; Sasic, Slobodan; Feld, Michael S.; Horowitz, Gary L.

    2002-11-01

    Concentrations of multiple analytes were simultaneously measured in whole blood with clinical accuracy, without sample processing, using near-infrared Raman spectroscopy. Spectra were acquired with an instrument employing nonimaging optics, designed using Monte Carlo simulations of the influence of light-scattering-absorbing blood cells on the excitation and emission of Raman light in turbid medium. Raman spectra were collected from whole blood drawn from 31 individuals. Quantitative predictions of glucose, urea, total protein, albumin, triglycerides, hematocrit, and hemoglobin were made by means of partial least-squares (PLS) analysis with clinically relevant precision (r2 values >0.93). The similarity of the features of the PLS calibration spectra to those of the respective analyte spectra illustrates that the predictions are based on molecular information carried by the Raman light. This demonstrates the feasibility of using Raman spectroscopy for quantitative measurements of biomolecular contents in highly light-scattering and absorbing media.

  9. Raman spectroscopy as a tool in differentiating conjugated polyenes from synthetic and natural sources

    Science.gov (United States)

    Fernandes, Rafaella F.; Maia, Lenize F.; Couri, Mara R. C.; Costa, Luiz Antonio S.; de Oliveira, Luiz Fernando C.

    2015-01-01

    This work presents the Raman spectroscopic characterization of synthetic analogs of natural conjugated polyenals found in octocorals, focusing the unequivocal identification of the chemical species present in these systems. The synthetic material was produced by the autocondensation reaction of crotonaldehyde, generating a demethylated conjugated polyene containing 11 carbon-carbon double bonds, with just a methyl group on the end of the carbon chain. The resonance Raman spectra of such pigment has shown the existence of enhanced modes assigned to ν1(Cdbnd C) and ν2(Csbnd C) modes of the main chain. For the resonance Raman spectra of natural pigments from octocorals collected in the Brazilian coast, besides the previously cited bands, it could be also observed the presence of the ν4(Csbnd CH3), related to the vibrational mode who describes the vibration of the methyl group of the central carbon chain of carotenoids. Other interesting point is the observation of overtones and combination bands, which for carotenoids involves the presence of the ν4 mode, whereas for the synthetic polyene this band, besides be seen at a slightly different wavenumber position, does not appear as an enhanced mode and also as a combination, such as for the natural carotenoids. Theoretical molecular orbital analysis of polyenal-11 and lycopene has shown the structural differences which are also responsible for the resonance Raman data, based on the appearance of the (sbnd CH3) vibrational mode in the resonant transition only for lycopene. At last, the Raman band at ca. 1010 cm-1, assigned to the (sbnd CH3) vibrational mode, can be used for attributing the presence of each one of the conjugated polyenes: the resonance Raman spectrum containing the band at ca. 1010 cm-1 refers to the carotenoid (in this case lycopene), and the absence of such band in resonance conditions refers to the polyenal (in this case the polyenal-11).

  10. Ordered Gold Nanobowl Arrays as Substrates for Surface-Enhanced Raman Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    CHEN Ling; LIU Fan-Xin; ZHAN Peng; PAN Jian; WANG Zhen-Lin

    2011-01-01

    @@ We demonstrate that an interlinked gold half-shell array fabricated by metal deposition on a sacrificial twodimensional colloidal crystal template can show a large enhancement in surface-enhanced Raman spectroscopy at its main transmission resonance.It isfurther observed that Raman signal enhancement shows a noticeable difference when reversing the orientations of the Au nanobowls in relation to the underlying flat dielectric substrate.As the pump laser wavelength is tuned in the vicinity of the resonant plasmonic mode of the structure,the nhancement on an upward Au nanobowl array can be five-fold compared to that on a downward one.Numerical simulation confirms that for the upward nanobowls,a strong localized mode inside the Au nanobowls is formed at the resonant excitation wavelength,which helps to explain this observed extra enhancement in Raman scattering.%We demonstrate that an interlinked gold half-shell array fabricated by metal deposition on a sacrificial twodimensional colloidal crystal template can show a large enhancement in surface-enhanced Raman spectroscopy at its main transmission resonance.It is further observed that Raman signal enhancement shows a noticeable difference when reversing the orientations of the Au nanobowls in relation to the underlying flat dielectric substrate.As the pump laser wavelength is tuned in the vicinity of the resonant plasmonic mode of the structure, the enhancement on an upward Au nanobowl array can be five-fold compared to that on a downward one.Numerical simulation confirms that for the upward nanobowls, a strong localized mode inside the Au nanobowls is formed at the resonant excitation wavelength, which helps to explain this observed extra enhancement in Raman scattering.

  11. Influence of the ac Stark effect on stimulated hyper-Raman profiles in sodium vapor

    Energy Technology Data Exchange (ETDEWEB)

    Moore, M.A.; Garrett, W.R.; Payne, M.G.

    1988-08-01

    When pumping near the two-photon 3d resonance in pure sodium vapor and observing the backward hyper-Raman emission to the 3p substates, an asymmetry in ratios of 3p/sub 1/2/, 3p/sub 3/2/ associated emissions was observed dependent upon the direction of the initial laser detuning from the resonance. It has been determined that this asymmetry can be attributed to the ac Stark effect induced by the hyper-Raman emission itself. 3 refs., 3 figs.

  12. Raman imaging of extraterrestrial materials

    Science.gov (United States)

    Wang, Alian; Korotev, Randy L.; Jolliff, Bradley L.; Ling, Zongcheng

    2015-07-01

    Laser Raman Spectroscopy has been proposed and is under extensive development for surface exploration missions to planetary bodies of our Solar System. It reveals information on molecular structure and chemistry. The spatial distribution of molecular species in natural geological samples and planetary materials has significance for the geological processes by which they formed. Raman imaging is the best way to combine the molecular identification and characterization of geologic materials with their spatial distribution. This paper reports Raman imaging studies of five types of extraterrestrial materials and three terrestrial samples using a state-of-the-art Raman imaging system. The Raman spectral features of major, minor, and trace species in these samples, together with their spatial correlations revealed by these Raman imaging studies indicate the genetic relationships and the geological processes that these materials have been experienced. For robotic planetary surface exploration mission, a simple yet very useful molecular map of a sample can be generated by using line-scan or grid-scan of an in situ Raman system with tightly focused laser beam.

  13. Chemical aerosol Raman detector

    Science.gov (United States)

    Aggarwal, R. L.; Farrar, L. W.; Di Cecca, S.; Amin, M.; Perkins, B. G.; Clark, M. L.; Jeys, T. H.; Sickenberger, D. W.; D'Amico, F. M.; Emmons, E. D.; Christesen, S. D.; Kreis, R. J.; Kilper, G. K.

    2017-03-01

    A sensitive chemical aerosol Raman detector (CARD) has been developed for the trace detection and identification of chemical particles in the ambient atmosphere. CARD includes an improved aerosol concentrator with a concentration factor of about 40 and a CCD camera for improved detection sensitivity. Aerosolized isovanillin, which is relatively safe, has been used to characterize the performance of the CARD. The limit of detection (SNR = 10) for isovanillin in 15 s has been determined to be 1.6 pg/cm3, which corresponds to 6.3 × 109 molecules/cm3 or 0.26 ppb. While less sensitive, CARD can also detect gases. This paper provides a more detailed description of the CARD hardware and detection algorithm than has previously been published.

  14. Scanning angle Raman spectroscopy: Investigation of Raman scatter enhancement techniques for chemical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Matthew W. [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    This thesis outlines advancements in Raman scatter enhancement techniques by applying evanescent fields, standing-waves (waveguides) and surface enhancements to increase the generated mean square electric field, which is directly related to the intensity of Raman scattering. These techniques are accomplished by employing scanning angle Raman spectroscopy and surface enhanced Raman spectroscopy. A 1064 nm multichannel Raman spectrometer is discussed for chemical analysis of lignin. Extending dispersive multichannel Raman spectroscopy to 1064 nm reduces the fluorescence interference that can mask the weaker Raman scattering. Overall, these techniques help address the major obstacles in Raman spectroscopy for chemical analysis, which include the inherently weak Raman cross section and susceptibility to fluorescence interference.

  15. Raman Spectroscopy at High Pressures

    Directory of Open Access Journals (Sweden)

    Alexander F. Goncharov

    2012-01-01

    Full Text Available Raman spectroscopy is one of the most informative probes for studies of material properties under extreme conditions of high pressure. The Raman techniques have become more versatile over the last decades as a new generation of optical filters and multichannel detectors become available. Here, recent progress in the Raman techniques for high-pressure research and its applications in numerous scientific disciplines including physics and chemistry of materials under extremes, earth and planetary science, new materials synthesis, and high-pressure metrology will be discussed.

  16. Raaka-aineiden tunnistus Raman-spektroskopialla

    OpenAIRE

    2009-01-01

    Opinnäytetyön aiheena on Raman-spektroskopian käyttö raaka-aineiden tunnistuksessa. Raman-spektroskopia perustuu Raman-sirontaan, jonka Raman havaitsi 1928. Raman-sirontaa tapahtuu, kun molekyylin kemialliset sidokset kohtaavat valon fotonit ja fotonien energia muuttuu. Raman-sironta on hyvin heikkoa ja mittausta häiritsee huomattavasti voimakkaammat Rayleigh-sironta ja fluoresenssi. Vasta 1980-luvulla tekniikka oli riittävän kehittynyttä, että Raman-spektroskopiaa pystyttiin hyödyntämään käy...

  17. Validation model for Raman based skin carotenoid detection.

    Science.gov (United States)

    Ermakov, Igor V; Gellermann, Werner

    2010-12-01

    Raman spectroscopy holds promise as a rapid objective non-invasive optical method for the detection of carotenoid compounds in human tissue in vivo. Carotenoids are of interest due to their functions as antioxidants and/or optical absorbers of phototoxic light at deep blue and near UV wavelengths. In the macular region of the human retina, carotenoids may prevent or delay the onset of age-related tissue degeneration. In human skin, they may help prevent premature skin aging, and are possibly involved in the prevention of certain skin cancers. Furthermore, since carotenoids exist in high concentrations in a wide variety of fruits and vegetables, and are routinely taken up by the human body through the diet, skin carotenoid levels may serve as an objective biomarker for fruit and vegetable intake. Before the Raman method can be accepted as a widespread optical alternative for carotenoid measurements, direct validation studies are needed to compare it with the gold standard of high performance liquid chromatography. This is because the tissue Raman response is in general accompanied by a host of other optical processes which have to be taken into account. In skin, the most prominent is strongly diffusive, non-Raman scattering, leading to relatively shallow light penetration of the blue/green excitation light required for resonant Raman detection of carotenoids. Also, sizable light attenuation exists due to the combined absorption from collagen, porphyrin, hemoglobin, and melanin chromophores, and additional fluorescence is generated by collagen and porphyrins. In this study, we investigate for the first time the direct correlation of in vivo skin tissue carotenoid Raman measurements with subsequent chromatography derived carotenoid concentrations. As tissue site we use heel skin, in which the stratum corneum layer thickness exceeds the light penetration depth, which is free of optically confounding chromophores, which can be easily optically accessed for in vivo RRS

  18. Raman Studies of Carbon Nanostructures

    Science.gov (United States)

    Jorio, Ado; Souza Filho, Antonio G.

    2016-07-01

    This article reviews recent advances on the use of Raman spectroscopy to study and characterize carbon nanostructures. It starts with a brief survey of Raman spectroscopy of graphene and carbon nanotubes, followed by recent developments in the field. Various novel topics, including Stokes-anti-Stokes correlation, tip-enhanced Raman spectroscopy in two dimensions, phonon coherence, and high-pressure and shielding effects, are presented. Some consequences for other fields—quantum optics, near-field electromagnetism, archeology, materials and soil sciences—are discussed. The review ends with a discussion of new perspectives on Raman spectroscopy of carbon nanostructures, including how this technique can contribute to the development of biotechnological applications and nanotoxicology.

  19. Laser Raman Spectroscopy in studies of corrosion and electrocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Melendres, C.A.

    1988-01-01

    Laser Raman Spectroscopy (LRS) has become an important tool for the in-situ structural study of electrochemical systems and processes in recent years. Following a brief introduction of the experimental techniques involved in applying LRS to electrochemical systems, we survey the literature for examples of studies in the inhibition of electrode reactions by surface films (e.g., corrosion and passivation phenomena) as well as the acceleration of reactions by electro-sorbates (electrocatalysis). We deal mostly with both normal and resonance Raman effects on fairly thick surface films in contrast to surface-enhanced Raman investigations of monolayer adsorbates, which is covered in another lecture. Laser Raman spectroelectrochemical studies of corrosion and film formation on such metals as Pb, Ag, Fe, Ni, Co, Cr, Au, stainless steel, etc. in various solution conditions are discussed. Further extension of the technique to studies in high-temperature and high-pressure aqueous environments is demonstrated. Results of studies of the structure of corrosion inhibitors are also presented. As applications of the LRS technique in the area of electrocatalysis, we cite studies of the structure of transition metal macrocyclic compounds, i.e., phthalocyanines and porphyrins, used for catalysis of the oxygen reduction reaction. 104 refs., 20 figs.

  20. Raman measurement of carotenoid composition in human skin

    Science.gov (United States)

    Ermakov, Igor V.; Ermakova, Maia R.; Gellermann, Werner

    2004-07-01

    The carotenoids lycopene and beta-carotene are powerful antioxidants in skin and are thought to act as scavengers for free radicals and singlet oxygen. The role of carotenoid species in skin health is of strong current interest. We demonstrate the possibility to use Resonance Raman spectroscopy for fast, non-invasive, highly specific, and quantitative detection of beta-carotene and lycopene in human skin. Analyzing Raman signals originating from the carbon-carbon double bond stretch vibrations of the carotenoid molecules under blue and green laser excitation, we were able to characterize quantitatively the relative concentrations of each carotenoid species in-vivo. In the selective detection, we take advantage of different Raman cross-section spectral profiles for beta-carotene and lycopene molecules, and obtain a quantitative assessment of individual long-chain carotenoid species in the skin rather than their cumulative levels. Preliminary dual-wavelength Raman measurements reveal significant differences in the carotenoid composition of different subjects. The technique holds promise for rapid screening of carotenoid compositions in human skin in large populations and may be suitable in clinical studies for assessing the risk for cutaneous diseases.

  1. Revisiting the Young's double slit experiment for background-free nonlinear Raman spectroscopy and microscopy.

    Science.gov (United States)

    Gachet, David; Brustlein, Sophie; Rigneault, Hervé

    2010-05-28

    In the Young's double slit experiment, the spatial shift of the interference pattern projected onto a screen is directly related to the phase difference between the fields diffracted by the two slits. We apply this property to fields emitted by nonlinear processes and thus demonstrate background-free coherent anti-Stokes Raman scattering microscopy near an axial interface between a resonant and a nonresonant medium. This method is relevant to remove the nonresonant background in other coherent resonant processes.

  2. Photothermal resonance

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a method for detecting photo-thermal absorbance of a material utilising a mechanically temperature sensitive resonator (20) and a sample being arrange in thermal communication with the temperature sensitive resonator. The present invention further relates to an ap......The present invention relates to a method for detecting photo-thermal absorbance of a material utilising a mechanically temperature sensitive resonator (20) and a sample being arrange in thermal communication with the temperature sensitive resonator. The present invention further relates...... to an apparatus for detecting photo-thermal absorbance of a sample....

  3. Fast and reliable identification of microorganisms by means of Raman spectroscopy

    Science.gov (United States)

    Rösch, Petra; Harz, Michaela; Krause, Mario; Popp, Jürgen

    2007-07-01

    The identification of bacteria is necessary as fast as possible e.g. to provide an appropriate therapy for patients. Here the cultivation time should be kept to a minimum. Beside microbiological identification methods Raman spectroscopy is a valuable tool for bacteria identification. UV-resonance Raman spectroscopy enables selective monitoring of the cellular DNA/RNA content and allows for a genotaxonomic classification of the bacteria. Since UV excitation may lead to sample destruction the measurements are performed on rotated bacterial films. For a faster identification avoiding the cultivation step single bacteria analysis is necessary. Using micro-Raman spectroscopy a spatial resolution in the size range of the bacteria can be achieved. With this Raman excitation the chemical components of the whole cell are measured which leads to a phenotypic classification. For localization of bacteria inside complex matrices fluorescence labeling is achieved.

  4. Intense Raman bands and low luminescence of thin films of heme proteins on silica

    Science.gov (United States)

    Sonois, Vanessa; Bacsa, Wolfgang; Faller, Peter

    2009-08-01

    We use resonance Raman spectroscopy to study cytochrome c, hemoglobin and myoglobin from 50 μM solutions dried on a SiO 2 surface. Intense Raman spectra were observed with low luminescent background when excited at 488 nm with low laser power levels (0.6 mW) and relative short acquisition times (120 s). We estimate that 1 picogram of heme proteins can be detected. A polarization sensitive Raman band in cytochrome c near the edge of dried droplets suggests that the proteins line up in the ring deposit. This preferential orientation is suggested to contribute to the low luminescence back ground signal and to the larger Raman intensity compared to the heme proteins in powder form.

  5. Gold Nanoparticles as Probes for Nano-Raman Spectroscopy: Preliminary Experimental Results and Modeling

    Directory of Open Access Journals (Sweden)

    V. Le Nader

    2012-01-01

    Full Text Available This paper presents an effective Tip-Enhanced Raman Spectrometer (TERS in backscattering reflection configuration. It combines a tip-probe nanopositioning system with Raman spectroscope. Specific tips were processed by anchoring gold nanoparticles on the apex of tapered optical fibers, prepared by an improved chemical etching method. Hence, it is possible to expose a very small area of the sample (~20 nm2 to the very strong local electromagnetic field generated by the lightning rod effect. This experimental configuration was modelled and optimised using the finite element method, which takes into account electromagnetic effects as well as the plasmon resonance. Finally, TERS measurements on single-wall carbon nanotubes were successfully performed. These results confirm the high Raman scattering enhancement predicted by the modelling, induced by our new nano-Raman device.

  6. Surface-enhanced Raman scattering: a new optical probe in molecular biophysics and biomedicine

    DEFF Research Database (Denmark)

    Kneipp, J.; Wittig, B.; Bohr, Henrik

    2010-01-01

    Sensitive and detailed molecular structural information plays an increasing role in molecular biophysics and molecular medicine. Therefore, vibrational spectroscopic techniques, such as Raman scattering, which provide high structural information content are of growing interest in biophysical...... of the free electrons in the metal. This effect of surface-enhanced Raman scattering (SERS) allows us to push vibrational spectroscopy to new limits in detection sensitivity, lateral resolution, and molecular structural selectivity. This opens up exciting perspectives also in molecular biospectroscopy...... and biomedical research. Raman spectroscopy can be revolutionized when the inelastic scattering process takes place in the very close vicinity of metal nanostructures. Under these conditions, strongly increased Raman signals can be obtained due to resonances between optical fields and the collective oscillations...

  7. Raman spectroscopic measurements of beta-carotene and lycopene in human skin

    Science.gov (United States)

    Darvin, M. E.; Gerzonde, I.; Ey, S.; Brandt, Nikolai N.; Albrecht, Hansjoerg; Gonchukov, Sergei A.; Sterry, Wolfram; Lademann, Juergen

    2004-08-01

    The antioxidant β-carotene and lycopene substances were detected non-invasively, in vivo in human skin using resonance Raman spectroscopy. Both substances were detected simultaneously. To distinguish between the substances, the Raman signals were excited at 488 nm and 514,5 nm simultaneously using a multilane Ar+ laser. The application of a fiber based optical imaging system allowed the detection of β-carotene and lycopene on any skin area. The disturbance of the measurements because of non-homogeneous skin pigmentation was avoided by using a measuring area of 28 mm2. The minimum power density for registration of the Raman signals and their optimum relation was determined. The Raman spectroscopic method is well suited for the evaluation of the efficacy of topically or systematically applied amounts of β-carotene and lycopene.

  8. Resonance Raman Intensities and Structure of S2 State of Nickel(II) Porphyrin by Time-Dependent Approach%时间域方法分析镍卟啉的共振拉曼强度与S2激发态结构

    Institute of Scientific and Technical Information of China (English)

    陈东明; 丛涤非; 何天敬; 章应辉; 刘凡镇

    2001-01-01

    Resonance Raman intensities and UV-visible absorption spectrum of nickel(II) porphyrin (NiP) were analyzed with time-dependent formulas under standard approximations for Condon mechanism of enhancement. The resultant dimensionless displacements on S2 state are comparable with those obtained by Spiro et al. from Kramers-Kronig transform methods. It was deduced from the calculations that there are large dimensionless displacements on the excited state along ν8 and ν2 coordinates. These normal modes consist of relatively large components of CβCβ, Cα Cm bond stretching and CαCmCα bond bending motions. Compared with the ground state, the average bond-lengths of CβCβ, CαCm, and CαN bonds at S2 state increase respectively by 0.27, 0.14, and 0.07pm,while that of CαCβ bond decreases by 0.20pm,which are well in coincident with the SPMO calculations in literature.%研究了入射光波长与S0→S2跃迁共振的情形下,卟啉镍配合物(NiP)的振动拉曼光谱。用时间域方法计算了NiP的共振拉曼强度和吸收光谱。结果表明,相对于基态,S2态NiP的分子构型沿着ν8和ν2简正坐标有较大的位移。这些简正坐标主要涉及卟啉环的CαCm键和CβCβ键伸缩运动,以及CαCmCα变角运动。与基态相比, S2态的CβCβ、 CαCm和CαN键分别增大0.27、 0.14、 0.07 pm,而CαCβ键则减小0.20 pm,与前人的赝势分子轨道计算(SPMO)结果相近。还从RR强度角度讨论了S2态的Jahn-Teller畸变。

  9. Operating Regime for a Backward Raman Laser Amplifier in Preformed Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Daniel S. Clark; Nathaniel J. Fisch

    2003-02-06

    A critical issue in the generation of ultra-intense, ultra-short laser pulses by backward Raman scattering in plasma is the stability of the pumping pulse to premature backscatter from thermal fluctuations in the preformed plasma. Malkin et al. [V.M. Malkin, et al., Phys. Rev. Lett. 84 (6):1208-1211, 2000] demonstrated that density gradients may be used to detune the Raman resonance in such a way that backscatter of the pump from thermal noise can be stabilized while useful Raman amplification persists. Here plasma conditions for which the pump is stable to thermal Raman backscatter in a homogeneous plasma and the density gradients necessary to stabilize the pump for other plasma conditions are quantified. Other ancillary constraints on a Raman amplifier are also considered to determine a specific region in the Te-he plane where Raman amplification is feasible. By determining an operability region, the degree of uncertainty in density or temperature tolerable for an experimental Raman amplifier is thus also identified. The fluid code F3D, which includes the effects of thermal fluctuations, is used to verify these analytic estimates.

  10. Sum-Frequency-Generation-Based Laser Sidebands for Tunable Femtosecond Raman Spectroscopy in the Ultraviolet

    Directory of Open Access Journals (Sweden)

    Liangdong Zhu

    2015-04-01

    Full Text Available Femtosecond stimulated Raman spectroscopy (FSRS is an emerging molecular structural dynamics technique for functional materials characterization typically in the visible to near-IR range. To expand its applications we have developed a versatile FSRS setup in the ultraviolet region. We use the combination of a narrowband, ~400 nm Raman pump from a home-built second harmonic bandwidth compressor and a tunable broadband probe pulse from sum-frequency-generation-based cascaded four-wave mixing (SFG-CFWM laser sidebands in a thin BBO crystal. The ground state Raman spectrum of a laser dye Quinolon 390 in methanol that strongly absorbs at ~355 nm is systematically studied as a standard sample to provide previously unavailable spectroscopic characterization in the vibrational domain. Both the Stokes and anti-Stokes Raman spectra can be collected by selecting different orders of SFG-CFWM sidebands as the probe pulse. The stimulated Raman gain with the 402 nm Raman pump is >21 times larger than that with the 550 nm Raman pump when measured at the 1317 cm−1 peak for the aromatic ring deformation and ring-H rocking mode of the dye molecule, demonstrating that pre-resonance enhancement is effectively achieved in the unique UV-FSRS setup. This added tunability in the versatile and compact optical setup enables FSRS to better capture transient conformational snapshots of photosensitive molecules that absorb in the UV range.

  11. Tissue Oxygenation Monitoring using Resonance Raman Spectroscopy during Hemorrhage

    Science.gov (United States)

    2013-12-27

    by the fact that young swine are highly susceptible to iron-deficient anemia secondary to low tissue stores at birth and extremely rapid growth.40 The...venous oximetry and shock index in the emergency department: use in the evaluation of clinical shock. Am J Emerg Med. 1992;10:538 541. 38. Rivers EP

  12. Ultraviolet Resonance Raman Enhancements in the Detection of Explosives

    Science.gov (United States)

    2009-06-01

    R. P. Feynman , R. B. Leighton, R. B and M. L. Sands, The Feynman Lectures on Physics . Reading, Mass: Addison-Wesley Pub, 1963. [40] S. D...OF SCIENCE IN APPLIED PHYSICS from the NAVAL POSTGRADUATE SCHOOL June 2009 Author: Billy Joe Short, Jr. Approved by...Craig Smith Thesis Advisor J. Chance Carter Second Reader James Luscombe Chairman, Department of Physics iv THIS PAGE INTENTIONALLY

  13. Gold Nanostructures for Surface-Enhanced Raman Spectroscopy, Prepared by Electrodeposition in Porous Silicon

    Directory of Open Access Journals (Sweden)

    Yukio H. Ogata

    2011-04-01

    Full Text Available Electrodeposition of gold into porous silicon was investigated. In the present study, porous silicon with ~100 nm in pore diameter, so-called medium-sized pores, was used as template electrode for gold electrodeposition. The growth behavior of gold deposits was studied by scanning electron microscope observation of the gold deposited porous silicon. Gold nanorod arrays with different rod lengths were prepared, and their surface-enhanced Raman scattering properties were investigated. We found that the absorption peak due to the surface plasmon resonance can be tuned by changing the length of the nanorods. The optimum length of the gold nanorods was ~600 nm for surface-enhanced Raman spectroscopy using a He-Ne laser. The reason why the optimum length of the gold nanorods was 600 nm was discussed by considering the relationship between the absorption peak of surface plasmon resonance and the wavelength of the incident laser for Raman scattering.

  14. Raman sideband cooling of a 138Ba+ ion using a Zeeman interval

    CERN Document Server

    Seck, Christopher M; Dietrich, Matthew R; Odom, Brian C

    2016-01-01

    Motional ground state cooling and internal state preparation are important elements for quantum logic spectroscopy (QLS), a class of quantum information processing. Since QLS does not require the high gate fidelities usually associated with quantum computation and quantum simulation, it is possible to make simplifying choices in ion species and quantum protocols at the expense of some fidelity. Here, we report sideband cooling and motional state detection protocols for $^{138}$Ba$^+$ of sufficient fidelity for QLS without an extremely narrowband laser or the use of a species with hyperfine structure. We use the two S$_{1/2}$ Zeeman sublevels of $^{138}$Ba$^+$ to Raman sideband cool a single ion to the motional ground state. Because of the small Zeeman splitting, near-resonant Raman sideband cooling of $^{138}$Ba$^+$ requires only the Doppler cooling lasers and two additional AOMs. Observing the near-resonant Raman optical pumping fluorescence, we estimate a final average motional quantum number $\\bar{n}\\appro...

  15. Experimental and ab initio DFT calculated Raman Spectrum of Sudan I, a Red Dye

    DEFF Research Database (Denmark)

    Kunov-Kruse, Andreas Jonas; Kristensen, Steffen Buus; Liu, Chuan;

    2011-01-01

    . Comparison was made with other azo dyes in the literature on natural, abundant plant pigments. The results show that there is a possibility in foodstuff analysis to distinguish Sudan I from other dyes by using Raman spectroscopy with more than one laser wavelength for resonance enhancement of the different...

  16. Electron-phonon coupling in perovskites studied by Raman Scattering

    Science.gov (United States)

    Sathe, V. G.; Tyagi, S.; Sharma, G.

    2016-10-01

    Raman scattering is an unique technique for characterization and quantification of electron-phonon, spin-phonon and spin-lattice coupling in many of the currently prominent compounds like multiferroics and manganites. In manganites, it is understood now that a phase separated landscape with coexisting metallic and insulating regions exist in most of the compounds and application of small external perturbation causes an alteration in this landscape. In such scenario, local metallic regions grow suddenly at the expense of insulating regions below the magnetic ordering temperature. Such regions can be characterized effectively using Raman scattering measurements where delocalized electrons couple with the adjacent phonon peaks giving a Fano resonance in the form of asymmetric line shape.

  17. Ring-Down Spectroscopy for Characterizing a CW Raman Laser

    Science.gov (United States)

    Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute

    2007-01-01

    .A relatively simple technique for characterizing an all-resonant intracavity continuous-wave (CW) solid-state Raman laser involves the use of ring-down spectroscopy. As used here, characterizing signifies determining such parameters as threshold pump power, Raman gain, conversion efficiency, and quality factors (Q values) of the pump and Stokes cavity modes. Heretofore, in order to characterize resonant-cavity-based Raman lasers, it has usually been necessary to manipulate the frequencies and power levels of pump lasers and, in each case, to take several sets of measurements. In cases involving ultra-high-Q resonators, it also has been desirable to lock pump lasers to resonator modes to ensure the quality of measurement data. Simpler techniques could be useful. In the present ring-down spectroscopic technique, one infers the parameters of interest from the decay of the laser out of its steady state. This technique does not require changing the power or frequency of the pump laser or locking the pump laser to the resonator mode. The technique is based on a theoretical analysis of what happens when the pump laser is abruptly switched off after the Raman generation reaches the steady state. The analysis starts with differential equations for the evolution of the amplitudes of the pump and Stokes electric fields, leading to solutions for the power levels of the pump and Stokes fields as functions of time and of the aforementioned parameters. Among other things, these solutions show how the ring-down time depends, to some extent, on the electromagnetic energy accumulated in the cavity. The solutions are readily converted to relatively simple equations for the parameters as functions of quantities that can be determined from measurements of the time-dependent power levels. For example, the steady-state intracavity conversion efficiency is given by G1/G2 1 and the threshold power is given by Pin(G2/G1)2, where Pin is the steady-state input pump power immediately prior to

  18. Nonlinear resonances

    CERN Document Server

    Rajasekar, Shanmuganathan

    2016-01-01

    This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...

  19. Barium Nitrate Raman Laser Development for Remote Sensing of Ozone

    Science.gov (United States)

    McCray, Christopher L.; Chyba, Thomas H.

    1997-01-01

    In order to understand the impact of anthropogenic emissions upon the earth's environment, scientists require remote sensing techniques which are capable of providing range-resolved measurements of clouds, aerosols, and the concentrations of several chemical constituents of the atmosphere. The differential absorption lidar (DIAL) technique is a very promising method to measure concentration profiles of chemical species such as ozone and water vapor as well as detect the presence of aerosols and clouds. If a suitable DIAL system could be deployed in space, it would provide a global data set of tremendous value. Such systems, however, need to be compact, reliable, and very efficient. In order to measure atmospheric gases with the DIAL technique, the laser transmitter must generate suitable on-line and off-line wavelength pulse pairs. The on-line pulse is resonant with an absorption feature of the species of interest. The off-line pulse is tuned so that it encounters significantly less absorption. The relative backscattered power for the two pulses enables the range-resolved concentration to be computed. Preliminary experiments at NASA LaRC suggested that the solid state Raman shifting material, Ba(NO3)2, could be utilized to produce these pulse pairs. A Raman oscillator pumped at 532 nm by a frequency-doubled Nd:YAG laser can create first Stokes laser output at 563 nm and second Stokes output at 599 nm. With frequency doublers, UV output at 281 nm and 299 nm can be subsequently obtained. This all-solid state system has the potential to be very efficient, compact, and reliable. Raman shifting in Ba(NO3)2, has previously been performed in both the visible and the infrared. The first Raman oscillator in the visible region was investigated in 1986 with the configurations of plane-plane and unstable telescopic resonators. However, most of the recent research has focused on the development of infrared sources for eye-safe lidar applications.

  20. Resonance surface enhanced Raman optical activity of myoglobin as a result of optimized resonance surface enhanced Raman scattering conditions

    DEFF Research Database (Denmark)

    Abdali, Salim; Johannessen, Christian; Nygaard, Jesper;

    2007-01-01

    at single molecule level. The results of this work, using silver nanoparticles and a laser excitation of 532 nm, became only feasible when the concentrations of nanoparticles, aggregation agent NaCl and the studied molecule were optimized in a series of systematic optimization steps. The spectral analysis...... has shown that the SERS effect behaves consequently, depending on the concentration ratio of each component, i.e., myoglobin, Ag colloids and NaCl. Accordingly, it is shown here that SERS intensity has its maximum at certain concentration of these components, whereas below or above this value...

  1. Characterization of acid-treated carbon nanotube thin films by means of Raman spectroscopy and field-effect response

    Science.gov (United States)

    Zhang, Zhi-Bin; Li, Jiantong; Cabezas, Ana López; Zhang, Shi-Li

    2009-07-01

    By combining Raman spectroscopy with transistor transfer characteristics, acid treatment of single-walled carbon nanotubes (SWCNTs) in a mixture of concentrated HNO 3/H 2SO 4 has been characterized. The acid treatment results in a sharp decrease in the Raman resonant signals of the metallic SWCNTs but no observable change in those of the semiconducting SWCNTs. However, the acid treatment causes disappearing gate modulation of the thin-film transistors made of the SWCNTs, contrary to what would be expected referring to the Raman results. These experimental results suggest that the energy band of the semiconducting SWCNTs is significantly affected by absorbates induced by the acid treatment.

  2. Rashba realization: Raman with RF

    CERN Document Server

    Campbell, Daniel L

    2015-01-01

    We theoretically explore a Rashba spin-orbit coupling scheme which operates entirely in the absolute ground state manifold of an alkali atom, thereby minimizing all inelastic processes. An energy gap between ground eigenstates of the proposed coupling can be continuously opened or closed by modifying laser polarizations. Our technique uses far-detuned "Raman" laser coupling to create the Rashba potential, which has the benefit of low spontaneous emission rates. At these detunings, the Raman matrix elements that link $m_F$ magnetic sublevel quantum numbers separated by two are also suppressed. These matrix elements are necessary to produce the Rashba Hamiltonian within a single total angular momentum $f$ manifold. However, the far-detuned Raman couplings can link the three XYZ states familiar to quantum chemistry, which possess the necessary connectivity to realize the Rashba potential. We show that these XYZ states are essentially the hyperfine spin eigenstates of $^{87}\\text{Rb}$ dressed by a strong radio-fr...

  3. Raman spectroscopy under extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Goncharov, A F; Crowhurst, J C

    2004-11-05

    We report the results of Raman measurements of various materials under simultaneous conditions of high temperature and high pressure in the diamond anvil cell (DAC). High temperatures are generated by laser heating or internal resistive (ohmic) heating or a combination of both. We present Raman spectra of cubic boron nitride (cBN) to 40 GPa and up to 2300 K that show a continuous pressure and temperature shift of the frequency of the transverse optical mode. We have also obtained high-pressure Raman spectra from a new noble metal nitride, which we synthesized at approximately 50 GPa and 2000 K. We have obtained high-temperature spectra from pure nitrogen to 39 GPa and up to 2000 K, which show the presence of a hot band that has previously been observed in CARS measurements. These measurements have also allowed us to constrain the melting curve and to examine changes in the intramolecular potential with pressure.

  4. [Study of Fermi resonance by means of solution concentration variation].

    Science.gov (United States)

    Jiang, Xiu-lan; Li, Dong-fei; Chen, Yuan-zheng; Zhou, Mi; Sun, Cheng-lin; Yang, Guang; Li, Zuo-wei; Gao, Shu-qin

    2011-05-01

    The values of Raman scattering coefficients of some molecules in which Fermi resonance occurs vary with solution concentration variation. We measured the Raman spectra of some solvents such as CCl4, CS2, C6H6, etc by changing the concentration of the solutions ranging from 10% to 100% in volume. As a result, the authors obtained the general law of Fermi resonance. We found some weak Fermi resonance phenomena as well that the two bands of Raman spectrum shift asymmetrically and that the fundamental of overtone is tuned by Fermi resonance and moves towards the same direction with the overtone simultaneously, which is same as the results Bier K. D. obtained by means of high-pressure technique. By means of this method, the authors demonstrated the conclusion that only the fundamental in combinations which has the same symmetry as the fundamental involved in Fermi resonance directly can its intensity variation influence the Fermi resonance. In this article, the authors present a new method to study Fermi resonance. This method is valuable in the identification and the assignment of spectral lines of solutions, the determination of molecular configuration of enzyme, the discrimination of isomer, as well as the influences on the molecular structures and properties caused by hydrogen bond.

  5. Higher order mode optical fiber Raman amplifiers

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Friis, Søren Michael Mørk; Usuga Castaneda, Mario A.;

    2016-01-01

    We review higher order mode Raman amplifiers and discuss recent theoretical as well as experimental results including system demonstrations.......We review higher order mode Raman amplifiers and discuss recent theoretical as well as experimental results including system demonstrations....

  6. Size-Dependent Raman Shifts for nanocrystals.

    Science.gov (United States)

    Gao, Yukun; Zhao, Xinmei; Yin, Penggang; Gao, Faming

    2016-04-22

    Raman spectroscopy is a very sensitive tool for probing semiconductor nanocrystals. The underlying mechanism behind the size-dependent Raman shifts is still quite controversial. Here we offer a new theoretical method for the quantum confinement effects on the Raman spectra of semiconductor nanocrystals. We propose that the shift of Raman spectra in nanocrystals can result from two overlapping effects: the quantum effect shift and surface effect shift. The quantum effect shift is extracted from an extended Kubo formula, the surface effect shift is determined via the first principles calculations. Fairly good prediction of Raman shifts can be obtained without the use of any adjustable parameter. Closer analysis shows that the size-dependent Raman shifts in Si nanocrystals mainly result from the quantum effect shifts. For nanodiamond, the proportion of surface effect shift in Raman shift is up to about 40%. Such model can also provide a good baseline for using Raman spectroscopy as a tool to measure size.

  7. Synthesis, characterization, Raman, and surface enhanced Raman studies of semiconductor quantum dots

    Science.gov (United States)

    Pan, Yi

    The major contributions and discoveries of the dissertation include: (1) Homogeneous nucleation processes for the formation of nanocrystals can occur at low temperature and do not need to proceed at high temperature to overcome a high energy barrier. Monodisperse PbS quantum dots (QDs) obtained with nucleation and growth at 45°C support this finding. (2) Monodisperse single elemental Se QDs can be produced by simple solution crystallization from TDE (1-tetradecene) or ODE (1-octadecene). (3) TDE is a better non-coordinating solvent compare to ODE. STDE (S dissolved in TDE) and SeTDE (Se dissolved in TDE) are stable reagents with long storage time. They can be used as universal precursors for S-containing and Se-containing QDs. (4) QDs synthesis can be carried out at low temperature and relatively short reaction time using the simple, non-injection, one-pot synthetic method. (5) The one-pot method can be extended for the synthesis of QDs and graphene oxide nanocomposites and metal and graphene oxide nanocomposites. (6) PbCl2-OLA (oleylamine) is a universal system for the synthesis of Pb-chaclogenides QDs. (7) Surface enhanced Raman spectroscopy (SERS) is used to probe both size and wave length dependent quantum confinement effects (QCEs) of PbS QDs. (8) Raman spectroscopy is a powerful tool to elucidate crystal structure of Se nanoclusters with size of 1--2 nm. Semiconductor QDs have attracted considerable attention due to their potential for energy-efficient materials in optoelectronic and solar cell applications. When the radius of a QD is decreased to that of the exciton Bohr radius, the valence and conduction bands are known to split into narrower bands due to QCEs. QCEs are both size and wave length dependent. We have developed, synthesized and characterized a series of Pb-chaclogenide QDs, which all the sizes of the QDs are monodisperse and smaller than their respective exciton Bohr radius, to study the QCEs of these QDs. SERS is used as a crucial tool to

  8. Challenges in higher order mode Raman amplifiers

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Nielsen, Kristian; Friis, Søren Michael Mørk;

    2015-01-01

    A higher order Raman amplifier model that take random mode coupling into account ispresented. Mode dependent gain and signal power fluctuations at the output of the higher order modeRaman amplifier are discussed......A higher order Raman amplifier model that take random mode coupling into account ispresented. Mode dependent gain and signal power fluctuations at the output of the higher order modeRaman amplifier are discussed...

  9. Raman Optical Activity and Raman Spectra of Amphetamine Species

    DEFF Research Database (Denmark)

    Berg, Rolf W.; Shim, Irene; White, Peter Cyril

    2012-01-01

    Theoretical calculations and preliminary measurements of vibrational Raman optical activity (ROA) spectra of different species of amphetamine (amphetamine and amphetamine-H+) are reported for the first time. The quantum chemical calculations were carried out as hybrid ab initio DFT-molecular orbi...

  10. Correlation steering in the angularly multimode Raman atomic memory.

    Science.gov (United States)

    Mazelanik, Mateusz; Dąbrowski, Michał; Wasilewski, Wojciech

    2016-09-19

    We present the possibility of steering the direction of correlations between the off-resonant Raman scattered photons from the angularly multimode atomic memory based on warm rubidium vapors. Using acousto-optic deflectors (AOD) driven by different modulation frequencies, we experimentally change the angle of incidence of the laser beams on the atomic ensemble. By performing correlation measurements for various deflection angles, we verify that we can choose the anti-Stokes light propagation direction independently of the correlated Stokes scattered light in a continuous way. As a result we can select the spatial mode of photons retrieved from the memory, which may be important for future development of quantum information processing.

  11. Surface enhanced raman spectroscopy on chip

    DEFF Research Database (Denmark)

    Hübner, Jörg; Anhøj, Thomas Aarøe; Zauner, Dan;

    2007-01-01

    is projected onto a CCD element and visualized by a computer. To enhance the otherwise rather weak Raman signal, a nanosurface is prepared and a sample solutions is impregnated on this surface. The surface enhanced Raman signal is picked up using a Raman probe and coupled into the spectrometer via an optical...

  12. Raman probing of competitive laser heating and local recrystallization effect in ZnO nanocrystals.

    Science.gov (United States)

    Ye, J D; Parkinson, P; Ren, F F; Gu, S L; Tan, H H; Jagadish, C

    2012-10-01

    The competitive laser-induced local heating and recrystallization effects in ZnO nanocrystals embedded in a MgO/ZnO stack are reported via resonance Raman spectra. The dependence of the intensity, energy, and resonance effects of the longitudinal optical (LO) phonon on laser excitation condition are discussed in the context of Fröhlich interaction. Redistribution of defects, impurity-diffusion, and grain regrowth caused by thermal and photochemical effects lead to significant changes in coupling strength of electron-phonon interaction, and the resonance behaviors are strongly affected by the interplay of local heating, heat trapping, and local structural modification in such nanostructures.

  13. Raman spectroscopy as a tool for the characterization and classification of pollen; Raman-Spektroskopie als Werkzeug fuer die Charakterisierung und Klassifizierung von Pollen

    Energy Technology Data Exchange (ETDEWEB)

    Schulte, Franziska

    2010-09-20

    The chemical composition of pollen, the physiological containers that produce the male gametophytes of seed plants, has been a subject of research of plant physiologists, biochemists, and lately even material scientists for various reasons. The aim of this work was the analysis of whole pollen grains and pollen components by Raman Spectroscopy. These experiments were complemented by other techniques such as Enviromental Scanning Electron Microscopy (ESEM), High-Performance- Thin-Layer-Chromatography (HPTLC), Infrared Spectroscopy (IR) and Nuclear-Magnetic-Resonance Spectroscopy (NMR). As reported here, individual fresh pollen grains and their morphological constituents can be characterized and also classified in situ without prior preparation. Classification of pollen is based on their biochemical fingerprint revealed in their Raman spectrum. Raman spectroscopy is nondestructive and can be carried out with single pollen grains or fragments. It could be shown that the biochemical makeup of the pollen (as a part of the recognition/mating system) is altered during formation of a new biological species and that the species-specific chemical similarities and dissimilarities indeed reflect in the Raman spectral fingerprint. On the basis of the chemical information, unsupervised multivariate analysis consisting of hierarchical clustering revealed in most cases chemical similarities between species that were indicative of both phylogenetic relationship and matin behavior. Therefore experiments were conducted that gave the in situ Raman spectroscopic signatures ot the carotenoid molecules. As the data indicates, the in situ Raman spectra of the carotenoid molecules measured in single intact pollen grains provide in situ evidence of interspecies variations in pollen carotenoid content, structure, and/or assembly without prior purification. Results from HPTLC confirmed that carotenoid composition varied greatly between species and that the different in situ spectral

  14. Raman spectroscopy for nanomaterials characterization

    CERN Document Server

    2012-01-01

    First volume of a 40-volume series on nanoscience and nanotechnology, edited by the renowned scientist Challa S.S.R. Kumar. This handbook gives a comprehensive overview about Raman spectroscopy for the characterization of nanomaterials. Modern applications and state-of-the-art techniques are covered and make this volume essential reading for research scientists in academia and industry.

  15. Electronic Raman Scattering in Graphene

    Institute of Scientific and Technical Information of China (English)

    LU Hong-Yan; WANG Qiang-Hua

    2008-01-01

    Linear dispersion near the Dirac points in the band structure of graphenes can give rise to novel physical properties.We calculate the electronic contribution to the Raman spectra in graphenes, which also shows novel features.In the clean limit, the Raman spectrum in the undoped graphene is linear (with a universal slope against impurity scattering) at low energy due to the linear dispersion near the Dirac points, and it peaks at a position corresponding to the van Hove singularity in the band structure. In a doped graphene, the electronic Raman absorption is forbidden up to a vertical inter-band particle-hole gap. Beyond the gap the spectrum follows the undoped case. In the presence of impurities, absorption within the gap (in the otherwise clean case) is induced, which is identified as the intra-band contribution. The Drude-like intra-band contribution is seen to be comparable to the higher energy inter-band Raman peak. The results are discussed in connection to experiments.

  16. Photonics crystal fiber Raman sensors

    Science.gov (United States)

    Yang, Xuan; Bond, Tiziana C.; Zhang, Jin Z.; Li, Yat; Gu, Claire

    2012-11-01

    Hollow core photonic crystal fiber (HCPCF) employs a guiding mechanism fundamentally different from that in conventional index guiding fibers. In an HCPCF, periodic air channels in a glass matrix act as reflectors to confine light in an empty core. As a result, the interaction between light and glass can be very small. Therefore, HCPCF has been used in applications that require extremely low non-linearity, high breakdown threshold, and zero dispersion. However, their applications in optical sensing, especially in chemical and biological sensing, have only been extensively explored recently. Besides their well-recognized optical properties the hollow cores of the fibers can be easily filled with liquid or gas, providing an ideal sampling mechanism in sensors. Recently, we have demonstrated that by filling up a HCPCF with gas or liquid samples, it is possible to significantly increase the sensitivity of the sensors in either regular Raman or surface enhanced Raman scattering (SERS) applications. This is because the confinement of both light and sample inside the hollow core enables direct interaction between the propagating wave and the analyte. In this paper, we report our recent work on using HCPCF as a platform for Raman or SERS in the detection of low concentration greenhouse gas (ambient CO2), biomedically significant molecules (e.g., glucose), and bacteria. We have demonstrated that by filling up a HCPCF with gas or liquid samples, it is possible to significantly increase the sensitivity of the sensors in either regular Raman or SERS applications.

  17. Femtosecond stimulated Raman scattering for polyatomics with harmonic potentials: Application to rhodamine 6G

    Science.gov (United States)

    Niu, Kai; Cong, Shulin; Lee, Soo-Y.

    2009-08-01

    The perturbation theory of stimulated Raman scattering (SRS), with Raman pump on minus pump off and heterodyne detection along the probe direction, is reviewed. It has four third-order polarization terms, labeled as SRS or inverse Raman scattering (IRS): SRS(I), SRS(II), IRS(I), and IRS(II). These four polarizations have a wave packet interpretation. The polarizations, with homogenous and inhomogeneous broadening included, can be written as integrals over four-time correlation functions, and analytic formulas are derived for the latter for multidimensional harmonic potential surfaces with Franck-Condon displacements in the modes which facilitates the calculation of the SRS cross sections. The theory is applied to understand recent experimental results on the femtosecond SRS (FSRS) of a fluorescent dye, rhodamine 6G (R6G), where the Raman pump pulse is about 1 ps long, and the probe pulse is about 10 fs. The calculations compared very well with the R6G experimental results for off-resonance and resonance FSRS spectra spanning both Stokes and anti-Stokes bands, and for negative and positive pump-probe delay times on resonance.

  18. Raman scattering by phonons of Ga1-xAlxSb mixed crystals

    Science.gov (United States)

    Berdekas, D.

    2013-06-01

    We present calculations of the Raman scattering spectra by the long-wavelength vibrations of Ga1-xAlxSb mixed crystals for three different cation concentrations. Each mixed crystal is approached using a primitive cell 64 times larger than the primitive cell of the bulk constituents GaSb and AlSb. The phonon modes are calculated on the basis of an 11 parameter Rigid Ion Model and the Raman spectra are calculated using the Bond Polarizability Model (BPM), away from resonance conditions. The parameters of this model (BPM) are not arbitrarily approximated but we have obtained them on the basis of certain relations, involving directly measurable quantities, such as dielectric and elastooptic constants of the bulk crystal. It is shown that for small concentrations the Al ions are not randomly distributed over the whole crystal but almost all tend to concentrate in neighboring lattice planes. Further, we have reproduced the Raman spectra close to resonance conditions, assuming that the value of the first order polarizability of AlSb is increased by an amount of 50% close to resonance conditions. Finally it is shown that disorder produces asymmetric Raman lines spectra with the intensities of the two strongest peaks in the optic frequency ranges of the bulk constituents being concentration dependent.

  19. Broadband converging plasmon resonance at a conical nanotip

    OpenAIRE

    Wang, Yunshan; Plouraboué, Franck; Chang, Hsueh-Chia

    2013-01-01

    International audience; We propose an analytical theory which predicts that Converging Plasmon Resonance (CPR) at conical nanotips exhibits a red-shifted and continuous band of resonant frequencies and suggests potential application of conical nanotips in various fields, such as plasmonic solar cells, photothermal therapy, tip-enhanced Raman and other spectroscopies. The CPR modes exhibit superior confinement and ten times broader scattering bandwidth over the entire solar spectrum than smoot...

  20. 瞬态吸收和共振拉曼光谱研究硝基对联苯氮宾、氮宾离子反应活性的影响%Investigation of the Influence of Nitro-Substitution on the Reaction of Biphenyl-Nitrene and Nitrenium Ion by Transient Absorption and Resonance Raman Spectroscopic Techniques

    Institute of Scientific and Technical Information of China (English)

    李亚芳; 程博文; 沈超; 郑旭明; 薛佳丹; 杜勇; 汤文建

    2016-01-01

    利用光解芳基叠氮化合物得到单重态氮宾,运用纳秒瞬态吸收光谱、瞬态共振拉曼光谱实验手段,辅以密度泛函理论(DFT)计算,研究了4′-硝基-4-联苯氮宾在乙腈和水溶液中的光化学反应中间体。实验结果表明,在非质子溶剂中,4′-硝基-4-联苯氮宾发生系间窜越反应生成三线态氮宾;在质子溶剂中,单重态氮宾可被质子化产生氮宾离子。与4-联苯氮宾和氮宾离子相比,硝基对单重态氮宾系间窜越反应路径影响很小;降低了氮宾离子与水和叠氮阴离子的反应活性,却提高了其与鸟苷的反应活性。%Arylnitrenes and arylnitrenium ions are both short-lived intermediates that are highly reactive. In this work, nanosecond transient absorption and transient resonance Raman spectroscopic measurements were used to detect and identify the intermediates generated from the singlet 4′-nitro-4-biphenylnitrene after photolysis of the corresponding aryl azide in acetonitrile and aqueous solution. Combined with the density functional theory (DFT) simulation results, the structural and electronic characteristics of the above experimental intermediates were specified. The spectral results indicate that in aprotic solvents (such as acetonitrile), the singlet 4′-nitro-4-biphenylnitrene undergoes intersystem crossing (ISC) to the triplet nitrene. In contrast, in a protic solvent (such as the mixed aqueous solution used in this work), the singlet 4′-nitro-4-biphenylnitrene can be protonated to produce the nitrenium ion. Compared with its un-substituted counterpart, the nitro substitution has little influence on the ISC reaction pathway of the singlet 4-biphenylnitrene. With regard to the un-substituted nitrenium ion, the nitro group decreases its reactivity towards water and azide anion, while accelerating its reaction rate towards 2′-deoxyguanosine based on the different quench reaction rates between the nitrenium ion and

  1. Raman spectroscopy of bone metastasis

    Science.gov (United States)

    Esmonde-White, Karen A.; Sottnik, Joseph; Morris, Michael; Keller, Evan

    2012-02-01

    Raman spectroscopy of bone has been used to characterize chemical changes occurring in diseases such as osteoporosis, osteoarthritis and osteomyelitis. Metastasis of cancer into bone causes changes to bone quality that are similar to those observed in osteoporosis, such as decreased bone strength, but with an accelerated timeframe. In particular, osteolytic (bone degrading) lesions in bone metastasis have a marked effect on patient quality of life because of increased risk of fractures, pain, and hypercalcemia. We use Raman spectroscopy to examine bone from two different mouse models of osteolytic bone metastasis. Raman spectroscopy measures physicochemical information which cannot be obtained through standard biochemical and histological measurements. This study was reviewed and approved by the University of Michigan University Committee on the Care and Use of Animals. Two mouse models of prostate cancer bone metastasis, RM1 (n=3) and PC3-luc (n=4) were examined. Tibiae were injected with RM1 or PC3-luc cancer cells, while the contralateral tibiae received a placebo injection for use as controls. After 2 weeks of incubation, the mice were sacrificed and the tibiae were examined by Raman microspectroscopy (λ=785 nm). Spectroscopic markers corresponding to mineral stoichiometry, bone mineralization, and mineral crystallinity were compared in spectra from the cancerous and control tibiae. X-ray imaging of the tibia confirmed extensive osteolysis in the RM1 mice, with tumor invasion into adjoining soft tissue and moderate osteolysis in the PC3-luc mice. Raman spectroscopic markers indicate that osteolytic lesions are less mineralized than normal bone tissue, with an altered mineral stoichiometry and crystallinity.

  2. Visible wavelength surface-enhanced Raman spectroscopy from In-InP nanopillars for biomolecule detection

    Science.gov (United States)

    Murdoch, B. J.; Portoles, J. F.; Tardio, S.; Barlow, A. J.; Fletcher, I. W.; Cumpson, P. J.

    2016-12-01

    Visible wavelength surface-enhanced Raman spectroscopy (SERS) has been observed from bovine serum albumin (BSA) using In-InP nanopillars synthesised by Ar gas cluster ion beam sputtering of InP wafers. InP provides a high local refractive index for plasmonic In structures, which increases the wavelength of the In surface plasmon resonance. The Raman scattering signal was determined to be up to 285 times higher for BSA deposited onto In-InP nanopillars when compared with Si wafer substrates. These substrates demonstrate the label-free detection of biomolecules by visible wavelength SERS, without the use of noble metal particles.

  3. Investigation of SOI Raman Lasers for Mid-Infrared Gas Sensing

    Science.gov (United States)

    Passaro, Vittorio M.N.; De Leonardis, Francesco

    2009-01-01

    In this paper, the investigation and detailed modeling of a cascaded Raman laser, operating in the midwave infrared region, is described. The device is based on silicon-on-insulator optical waveguides and a coupled resonant microcavity. Theoretical results are compared with recent experiments, demonstrating a very good agreement. Design criteria are derived for cascaded Raman lasers working as continuous wave light sources to simultaneously sense two types of gases, namely C2H6 and CO2, at a moderate power level of 130 mW. PMID:22408481

  4. Raman lasing and Fano lineshapes in a packaged fiber-coupled whispering-gallerymode microresonator

    CERN Document Server

    Zhao, Guangming; Wang, Tao; Xu, Linhua; Long, Gui-lu; Yang, Lan

    2016-01-01

    We report Raman lasing and the optical analog of electromagnetically-induced-transparency (EIT) in a whispering-gallerymode (WGM) microtoroid resonator embedded in a low refractive index polymer matrix together with a tapered fiber coupler. The Raman laser supports both single and multimode operation with low power thresholds. Observations of Fano and EIT-like pheonomena in a packaged microresonator will enable high resolution sensors and can be used in networks where slow light process is needed. These results open the way for portable, robust, and stable WGM microlasers and laserbased sensors for applications in various environments.

  5. Raman characteristics of hydrocarbon and hydrocarbon inclusions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Nai; TIAN ZuoJi; LENG YingYing; WANG HuiTong; SONG FuQing; MENG JianHua

    2007-01-01

    The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm-1 to 2970 cm-1); (2)branch methyl has the particular peak of 748 cm-1±; (3) six cyclic has the particular peak of 804 cm-1±; (4)phenyl has two particular peaks of 988 cm-1± and 3058 cm-1± and the 988 cm-1± peak is stronger than the 3058 cm-1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm-1±, 1635 cm-1± and 2996 cm-1±, with the 1635 cm-1± peak being the strongest, showing that the number of carbon in hydrocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclusions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydrocarbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram.And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion,saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion.

  6. Raman characteristics of hydrocarbon and hydrocarbon inclusions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm-1 to 2970 cm-1); (2) branch methyl has the particular peak of 748 cm-1±; (3) six cyclic has the particular peak of 804 cm-1±; (4) phenyl has two particular peaks of 988 cm-1± and 3058 cm-1± and the 988 cm-1± peak is stronger than the 3058 cm-1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm-1±, 1635 cm-1± and 2996 cm-1±, with the 1635 cm-1± peak being the strongest, showing that the number of carbon in hy-drocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclu-sions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydro-carbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram. And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion, saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion.

  7. Time-Encoded Raman: Fiber-based, hyperspectral, broadband stimulated Raman microscopy

    CERN Document Server

    Karpf, Sebastian; Wieser, Wolfgang; Klein, Thomas; Huber, Robert

    2014-01-01

    Raman sensing and Raman microscopy are amongst the most specific optical technologies to identify the chemical compounds of unknown samples, and to enable label-free biomedical imaging with molecular contrast. However, the high cost and complexity, low speed, and incomplete spectral information provided by current technology are major challenges preventing more widespread application of Raman systems. To overcome these limitations, we developed a new method for stimulated Raman spectroscopy and Raman imaging using continuous wave (CW), rapidly wavelength swept lasers. Our all-fiber, time-encoded Raman (TICO-Raman) setup uses a Fourier Domain Mode Locked (FDML) laser source to achieve a unique combination of high speed, broad spectral coverage (750 cm-1 - 3150 cm-1) and high resolution (0.5 cm-1). The Raman information is directly encoded and acquired in time. We demonstrate quantitative chemical analysis of a solvent mixture and hyperspectral Raman microscopy with molecular contrast of plant cells.

  8. Raman and coherent anti-Stokes Raman scattering microspectroscopy for biomedical applications

    Science.gov (United States)

    Krafft, Christoph; Dietzek, Benjamin; Schmitt, Michael; Popp, Jürgen

    2012-04-01

    A tutorial article is presented for the use of linear and nonlinear Raman microspectroscopies in biomedical diagnostics. Coherent anti-Stokes Raman scattering (CARS) is the most frequently applied nonlinear variant of Raman spectroscopy. The basic concepts of Raman and CARS are introduced first, and subsequent biomedical applications of Raman and CARS are described. Raman microspectroscopy is applied to both in-vivo and in-vitro tissue diagnostics, and the characterization and identification of individual mammalian cells. These applications benefit from the fact that Raman spectra provide specific information on the chemical composition and molecular structure in a label-free and nondestructive manner. Combining the chemical specificity of Raman spectroscopy with the spatial resolution of an optical microscope allows recording hyperspectral images with molecular contrast. We also elaborate on interfacing Raman spectroscopic tools with other technologies such as optical tweezing, microfluidics and fiber optic probes. Thereby, we aim at presenting a guide into one exciting branch of modern biophotonics research.

  9. Multiquark resonances

    Science.gov (United States)

    Esposito, A.; Pilloni, A.; Polosa, A. D.

    2017-01-01

    Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.

  10. Multiquark Resonances

    CERN Document Server

    Esposito, A.; Polosa, A.D.

    2016-01-01

    Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties has been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.

  11. Resonating Statements

    DEFF Research Database (Denmark)

    Hjelholt, Morten; Jensen, Tina Blegind

    2015-01-01

    IT projects are often complex arrangements of technological components, social actions, and organizational transformation that are difficult to manage in practice. This paper takes an analytical discourse perspective to explore the process of legitimizing IT projects. We introduce the concept...... of resonating statements to highlight how central actors navigate in various discourses over time. Particularly, the statements and actions of an IT project manager are portrayed to show how individuals can legitimize actions by connecting statements to historically produced discourses. The case study...... of an IT project in a Danish local government spans a two-year time period and demonstrates a double-loop legitimization process. First, resonating statements are produced to localize a national IT initiative to support the specificity of a local government discourse. Second, the resonating statements are used...

  12. Baryon Resonances

    CERN Document Server

    Oset, E; Sun, Bao Xi; Vacas, M J Vicente; Ramos, A; Gonzalez, P; Vijande, J; Torres, A Martinez; Khemchandani, K

    2009-01-01

    In this talk I show recent results on how many excited baryon resonances appear as systems of one meson and one baryon, or two mesons and one baryon, with the mesons being either pseudoscalar or vectors. Connection with experiment is made including a discussion on old predictions and recent results for the photoproduction of the $\\Lambda(1405)$ resonance, as well as the prediction of one $1/2^+$ baryon state around 1920 MeV which might have been seen in the $\\gamma p \\to K^+ \\Lambda$ reaction.

  13. Baryon Resonances

    Energy Technology Data Exchange (ETDEWEB)

    Oset, E. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Sarkar, S. [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700064 (India); Sun Baoxi [Institute of Theoretical Physics, College of Applied Sciences, Beijing University of Technology, Beijing 100124 (China); Vicente Vacas, M.J. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Ramos, A. [Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos, Universitat de Barcelona, 08028 Barcelona (Spain); Gonzalez, P. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Vijande, J. [Departamento de Fisica Atomica Molecular y Nuclear and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Martinez Torres, A. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Khemchandani, K. [Centro de Fisica Computacional, Departamento de Fisica, Universidade de Coimbra, P-3004-516 Coimbra (Portugal)

    2010-04-01

    In this talk I show recent results on how many excited baryon resonances appear as systems of one meson and one baryon, or two mesons and one baryon, with the mesons being either pseudoscalar or vectors. Connection with experiment is made including a discussion on old predictions and recent results for the photoproduction of the {lambda}(1405) resonance, as well as the prediction of one 1/2{sup +} baryon state around 1920 MeV which might have been seen in the {gamma}p{yields}K{sup +}{lambda} reaction.

  14. Neuroaesthetic Resonance

    DEFF Research Database (Denmark)

    Brooks, Anthony Lewis

    2013-01-01

    sessions are achieved via adaptive action-analyzed activities. These interactive virtual environments are designed to empower patients’ creative and/or playful expressions via digital feedback stimuli. Unconscious self- pushing of limits result from innate distractive mechanisms offered by the alternative...... the unencumbered motion-to-computer-generated activities - ‘Music Making’, ‘Painting’, ‘Robotic’ and ‘Video Game’ control. A focus of this position paper is to highlight how Aesthetic Resonance, in this context, relates to the growing body of research on Neuroaesthetics to evolve Neuroaesthetic Resonance....

  15. Autostereogram resonators

    Science.gov (United States)

    Leavey, Sean; Rae, Katherine; Murray, Adam; Courtial, Johannes

    2012-09-01

    Autostereograms, or "Magic Eye" pictures, are repeating patterns designed to give the illusion of depth. Here we discuss optical resonators that create light patterns which, when viewed from a suitable position by a monocular observer, are autostereograms of the three-dimensional shape of one of the mirror surfaces.

  16. Transcutaneous Raman Spectroscopy of Bone

    Science.gov (United States)

    Maher, Jason R.

    Clinical diagnoses of bone health and fracture risk typically rely upon measurements of bone density or structure, but the strength of a bone is also dependent upon its chemical composition. One technology that has been used extensively in ex vivo, exposed-bone studies to measure the chemical composition of bone is Raman spectroscopy. This spectroscopic technique provides chemical information about a sample by probing its molecular vibrations. In the case of bone tissue, Raman spectra provide chemical information about both the inorganic mineral and organic matrix components, which each contribute to bone strength. To explore the relationship between bone strength and chemical composition, our laboratory has contributed to ex vivo, exposed-bone animal studies of rheumatoid arthritis, glucocorticoid-induced osteoporosis, and prolonged lead exposure. All of these studies suggest that Raman-based predictions of biomechanical strength may be more accurate than those produced by the clinically-used parameter of bone mineral density. The utility of Raman spectroscopy in ex vivo, exposed-bone studies has inspired attempts to perform bone spectroscopy transcutaneously. Although the results are promising, further advancements are necessary to make non-invasive, in vivo measurements of bone that are of sufficient quality to generate accurate predictions of fracture risk. In order to separate the signals from bone and soft tissue that contribute to a transcutaneous measurement, we developed an overconstrained extraction algorithm that is based upon fitting with spectral libraries derived from separately-acquired measurements of the underlying tissue components. This approach allows for accurate spectral unmixing despite the fact that similar chemical components (e.g., type I collagen) are present in both soft tissue and bone and was applied to experimental data in order to transcutaneously detect, to our knowledge for the first time, age- and disease-related spectral

  17. Phase Matching of Diverse Modes in a WGM Resonator

    Science.gov (United States)

    Savchenkov, Anatoliy; Strekalov, Dmitry; Yu, Nan; Matsko, Andrey; Mohageg, Makan; Maleki, Lute

    2008-01-01

    Phase matching of diverse electromagnetic modes (specifically, coexisting optical and microwave modes) in a whispering-gallery-mode (WGM) resonator has been predicted theoretically and verified experimentally. Such phase matching is necessary for storage of microwave/terahertz and optical electromagnetic energy in the same resonator, as needed for exploitation of nonlinear optical phenomena. WGM resonators are used in research on nonlinear optical phenomena at low optical intensities and as a basis for design and fabrication of novel optical devices. Examples of nonlinear optical phenomena recently demonstrated in WGM resonators include low-threshold Raman lasing, optomechanical oscillations, frequency doubling, and hyperparametric oscillations. The present findings regarding phase matching were made in research on low-threshold, strongly nondegenerate parametric oscillations in lithium niobate WGM resonators. The principle of operation of such an oscillator is rooted in two previously observed phenomena: (1) stimulated Raman scattering by polaritons in lithium niobate and (2) phase matching of nonlinear optical processes via geometrical confinement of light. The oscillator is partly similar to terahertz oscillators based on lithium niobate crystals, the key difference being that a novel geometrical configuration of this oscillator supports oscillation in the regime. The high resonance quality factors (Q values) typical of WGM resonators make it possible to achieve oscillation at a threshold signal level much lower than that in a non-WGM-resonator lithium niobate crystal.

  18. [Preparation, characterization and surface-enhanced Raman properties of agarose gel/gold nanoparticles hybrid].

    Science.gov (United States)

    Ma, Xiao-yuan; Liu, Ying; Wang, Zhou-ping

    2014-08-01

    Agarose gel/gold nanoparticles hybrid was prepared by adding gold nanoparticles to preformed agarose gel. Naniocomposite structures and properties were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV-Vis-NIR absorption spectroscopy. Experimental data indicated a uniform distribution of gold nanoparticles adsorbed on agarose gel network And the excellent optical absorption properties were shown. Based on the swelling-contraction characteristics of agarose gel and the adjustable localized surface plasmon resonance (LSPR) of the gold nanoparticles, the nano-composites were used as surface enhanced Raman scattering (SERS) substrate to detect the Raman signal molecules Nile blue A. Results revealed that the porous structure of the agarose gel provided a good carrier for the enrichment of the gold nanoparticles. The gold nanoparticles dynamic hot-spot effect arising from the agarose gel contraction loss of water in the air greatly enhanced the Raman signal.

  19. Surface Plasmons and Surface Enhanced Raman Spectra of Aggregated and Alloyed Gold-Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    Y. Fleger

    2009-01-01

    Full Text Available Effects of size, morphology, and composition of gold and silver nanoparticles on surface plasmon resonance (SPR and surface enhanced Raman spectroscopy (SERS are studied with the purpose of optimizing SERS substrates. Various gold and silver films made by evaporation and subsequent annealing give different morphologies and compositions of nanoparticles and thus different position of the SPR peak. SERS measurements of 4-mercaptobenzoic acid obtained from these films reveal that the proximity of the SPR peak to the exciting laser wavelength is not the only factor leading to the highest Raman enhancement. Silver nanoparticles evaporated on top of larger gold nanoparticles show higher SERS than gold-silver alloyed nanoparticles, in spite of the fact that the SPR peak of alloyed nanoparticles is narrower and closer to the excitation wavelength. The highest Raman enhancement was obtained for substrates with a two-peak particle size distribution for excitation wavelengths close to the SPR.

  20. Diffusion Raman et luminescence dans des aerogels de silice purs ou dopes Dy

    Science.gov (United States)

    Guerri, F.; Fabre, F.; Zwick, A.; Bournett, D.

    1994-02-01

    Light scattering studies of pure and Dy doped aerogels are presented. Careful examination of Stokes and anti-Stokes spectra allow the discrimination between Raman and luminescence processes. It is shown that in pure aerogels, scattered intensity is due to Raman processes only, and the density of vibrational states does not exhibit any singularity. The fractal properties of the structure imply modifications not only in the spectral distribution of the low frequency modes (usually labelled phonons and fractons) but alsoin the high frequency one, at least up to 600 cm-1. In Dy-doped dense silica, coupling between electronic and vibronic excitations is evidenced by the presence of anti-Stokes luminescence. In Dy-doped aerogels, the enlarged Dy3+ electronic levels, strongly coupled with vibrational states give rise to emission processes traducing the response of the sample as a whole, rather than resonant Raman scattering or luminescence processes.

  1. Observation of the reduction of methylviologen at Ag and. beta. -ZnP/sub 2/ electrodes by raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Blatter-Moerke, I.; von Kaenal, H.; Wachter, P.

    1987-01-29

    The reduction of MV/sup 2 +/ to MV/sup +/ at Ag electrodes in aqueous solutions of 1 mM MV/sup 2 +/ + 0.1 M KCl was monitored by resonant Raman Scattering. Apart from dissolved MV/sup +/ a second, adsorbed species was found both by cyclic voltammetry and by Raman scattering. Roughening of the Ag electrode electrochemically enabled the detection of surface-enhanced Raman spectra from the oxidized component MV/sup 2 +/. On p-type ..beta..-ZnP/sub 2/ the incident laser beam produces a photocurrent which sets in at approx. -0.2 V/sub SCE/ and reduces the MV/sup 2 +/ ions present in the electrolyte. This reduction is monitored as function of applied voltage. The Raman intensities are found to proportional to the photocurrent.

  2. Increased wavelength options in the visible and ultraviolet for Raman lasers operating on dual Raman modes.

    Science.gov (United States)

    Mildren, R P; Piper, J A

    2008-03-01

    We report increased wavelength options from Raman lasers for Raman media having two Raman modes of similar gain coefficient. For an external-cavity potassium gadolinium tungstate Raman laser pumped at 532 nm, we show that two sets of Stokes orders are generated simultaneously by appropriate orientation of the Raman crystal, and also wavelengths that correspond to sums of the two Raman modes. Up to 14 visible Stokes lines were observed in the wavelength range 555-675 nm. The increase in Stokes wavelengths also enables a much greater selection of wavelengths to be accessed via intracavity nonlinear sum frequency and difference frequency mixing. For example, we demonstrate 30 output wavelength options for a wavelength-selectable 271-321 nm Raman laser with intracavity sum frequency mixing in BBO. We also present a theoretical analysis that enables prediction of wavelength options for dual Raman mode systems.

  3. 2 nm continuously tunable 488nm micro-integrated diode-laser-based SHG light source for Raman spectroscopy

    Science.gov (United States)

    Braune, M.; Maiwald, M.; Sumpf, B.; Tränkle, G.

    2016-04-01

    Raman spectroscopy in the visible spectral range is of great interest due to resonant Raman effects. Nevertheless, fluorescence and ambient light can mask the weak Raman lines. Shifted excitation Raman difference spectroscopy is a demonstrated tool to overcome this drawback. To apply this method, a light source with two alternating wavelengths is necessary. The spectral distance between these two wavelengths has to be adapted to the width of the Raman signal. According to the sample under investigation the width of the Raman signal could be in the range of 3 cm-1 - 12 cm-1. In this work, a micro-integrated light source emitting at 488 nm with a continuous wavelength tuning range up to 2 nm (83 cm-1) is presented. The pump source, a DFB laser emitting at 976 nm, and a periodically poled lithium niobate (PPLN) ridge waveguide crystal is used for the second harmonic generation (SHG). Both components are mounted on a μ-Peltier-element for temperature control. Here, a common wavelength tuning of the pump wavelength and the acceptance bandwidth of the SHG crystal via temperature is achieved. With the results the light source is suitable for portable Raman and SERDS experiments with a flexible spectral distance between both excitation wavelengths for SERDS with respect to the sample under investigation.

  4. Recent Advances in Biophysical/Biochemical/Biomedical Application of Raman Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    NaitengYu; XiaoyuanLi

    1995-01-01

    Examples of some important biophysical,biochemical and biomedical problems that have been uniquely solved by Raman spectroscopy will be illustrated and discussed.The first example concerns the electronic structure,metal-ligand bonding,and reactivity of metalloporphyrins,the synthetic models for the ubiquitous chromophore in hemoproteins.we will demonstrate how off-resonance scattering,electronic resonance enhanced scattering,as well as nonlinear hyper-Raman(three-photon)scattering can provide a highly complementary picture about the effective electronic symmetry and bonding of metalloporphyrins in its electronic ground and excited states.we will illustrate how the bonding information otained from the Raman effect can be useful in understanding the chemical behavior of metalloporhyrin such as its affinity toward exogenous ligand and its preference for the orientation of planar axial ligand(such as imidazole from histidine's sidechain).Some paradoxical misconception about the relationship between bond strength and ligand binding affinity will be discussed.Raman spectroscopy,particular with near infraed laser excitation to avoid fluorescence,has been applied successfully to extract significant biochemical information from intact eye lenses.The long-standing cotroversy over the exact nature of the involvement of disulfide cross-linking in lens aging and cataract formation has been settled by the Raman spectroscopy because of its ability for monitoring the sulfhydryl to disulfide reaction of an intact lens in a nondestructive and noninvasive manner.A more recent contribution to the lens biochemistry is the use of Raman spectroscopy for a clear demonstration of the biochemical changes induced by near ultraviolet light in the lens of an animal model,resembling the changes observed in human lens aging and cataract formation.

  5. Raman spectroscopy in pharmaceutical product design

    DEFF Research Database (Denmark)

    Paudel, Amrit; Raijada, Dhara; Rantanen, Jukka

    2015-01-01

    molecular-based drug discovery, design of innovative drug delivery systems and quality control of finished products. This review presents concise accounts of various conventional and emerging Raman instrumentations including associated hyphenated tools of pharmaceutical interest. Moreover, relevant...... application cases of Raman spectroscopy in early and late phase pharmaceutical development, process analysis and micro-structural analysis of drug delivery systems are introduced. Finally, potential areas of future advancement and application of Raman spectroscopic techniques are discussed....

  6. Ab initio study of coherent anti-Stokes Raman scattering (CARS) of the 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) explosive

    Science.gov (United States)

    Mohammed, Abdelsalam; Ågren, Hans; Thorvaldsen, Andreas J.; Ruud, Kenneth

    2010-01-01

    Coherent anti-Stokes Raman scattering (CARS) of the 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) C 3H 6N 6O 6 molecule is studied by ab initio methods. The results are compared to available experimental observations and against calculations and experimental observations of the conventional non-resonant Raman spectrum for RDX. It is found that all intense bands in the observed CARS spectrum and all Raman differential cross sections are well reproduced by the calculations. The features of the resonant CARS signal vary strongly from the corresponding Raman signal, and are obtained with a considerably larger cross section, a fact that could further facilitate the use of CARS spectroscopy in applications of stand-off detection of gaseous samples at ultra-low concentrations.

  7. Broadband converging plasmon resonance at a conical nanotip.

    Science.gov (United States)

    Wang, Yunshan; Plouraboue, Franck; Chang, Hsueh-Chia

    2013-03-11

    We propose an analytical theory which predicts that Converging Plasmon Resonance (CPR) at conical nanotips exhibits a red-shifted and continuous band of resonant frequencies and suggests potential application of conical nanotips in various fields, such as plasmonic solar cells, photothermal therapy, tip-enhanced Raman and other spectroscopies. The CPR modes exhibit superior confinement and ten times broader scattering bandwidth over the entire solar spectrum than smooth nano-structures. The theory also explicitly connects the optimal angles and resonant optical frequencies to the material permittivities, with a specific optimum half angle that depends only on the real permittivity for high-permittivity and low-loss materials.

  8. Self-assembled microtubes and rhodamine 6G functionalized Raman-active gold microrods from 1-hydroxybenzotriazole

    Indian Academy of Sciences (India)

    Ravula Thirupathi; Erode N Prabhakaran

    2011-05-01

    1-Hydroxybenzotriazole spontaneously self-assembles to form hollow, linear microtubes initiated by controlled evaporation from water. The tube cavities act as thermo-labile micromoulds for the synthesis of linear gold microrods. Rhodamine 6G-labelled gold microrods, exhibiting surface enhanced resonance Raman activity, have been synthesized using the HOBT microtubes.

  9. Raman Tensor Formalism for Optically Anisotropic Crystals.

    Science.gov (United States)

    Kranert, Christian; Sturm, Chris; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-03-25

    We present a formalism for calculating the Raman scattering intensity dependent on the polarization configuration for optically anisotropic crystals. It can be applied to crystals of arbitrary orientation and crystal symmetry measured in normal incidence backscattering geometry. The classical Raman tensor formalism cannot be used for optically anisotropic materials due to birefringence causing the polarization within the crystal to be depth dependent. We show that in the limit of averaging over a sufficiently large scattering depth, the observed Raman intensities converge and can be described by an effective Raman tensor given here. Full agreement with experimental results for uniaxial and biaxial crystals is demonstrated.

  10. Raman Spectroscopy and Related Techniques in Biomedicine

    Directory of Open Access Journals (Sweden)

    Alistair Elfick

    2010-03-01

    Full Text Available In this review we describe label-free optical spectroscopy techniques which are able to non-invasively measure the (biochemistry in biological systems. Raman spectroscopy uses visible or near-infrared light to measure a spectrum of vibrational bonds in seconds. Coherent anti-Stokes Raman (CARS microscopy and stimulated Raman loss (SRL microscopy are orders of magnitude more efficient than Raman spectroscopy, and are able to acquire high quality chemically-specific images in seconds. We discuss the benefits and limitations of all techniques, with particular emphasis on applications in biomedicine—both in vivo (using fiber endoscopes and in vitro (in optical microscopes.

  11. Raman Spectroscopy and its Application in Nanostructures

    CERN Document Server

    Zhang, Shu-Lin

    2012-01-01

    Raman Spectroscopy and its Application in Nanostructures is an original and timely contribution to a very active area of physics and materials science research. This book presents the theoretical and experimental phenomena of Raman spectroscopy, with specialized discussions on the physical fundamentals, new developments and main features in low-dimensional systems of Raman spectroscopy. In recent years physicists, materials scientists and chemists have devoted increasing attention to low-dimensional systems and as Raman spectroscopy can be used to study and analyse such materials as carbon nan

  12. What Good is Raman Water Vapor Lidar?

    Science.gov (United States)

    Whitman, David

    2011-01-01

    Raman lidar has been used to quantify water vapor in the atmosphere for various scientific studies including mesoscale meteorology and satellite validation. Now the international networks of NDACC and GRUAN have interest in using Raman water vapor lidar for detecting trends in atmospheric water vapor concentrations. What are the data needs for addressing these very different measurement challenges. We will review briefly the scientific needs for water vapor accuracy for each of these three applications and attempt to translate that into performance specifications for Raman lidar in an effort to address the question in the title of "What good is Raman water vapor Iidar."

  13. Design of an 1800nm Raman amplifier

    DEFF Research Database (Denmark)

    Svane, Ask Sebastian; Rottwitt, Karsten

    2013-01-01

    We present the experimental results for a Raman amplifier that operates at 1810 nm and is pumped by a Raman fiber laser at 1680 nm. Both the pump laser and the Raman amplifier is polarization maintaining. A challenge when scaling Raman amplifiers to longer wavelengths is the increase...... performance of the amplifier is also investigated for both configurations. Our results show an on/off gain exceeding 20 dB at 1810 nm for which the obtained effective noise figure is below 3 dB....

  14. Miniature standoff Raman probe for neurosurgical applications

    Science.gov (United States)

    Stevens, Oliver A. C.; Hutchings, Joanne; Gray, William; Vincent, Rosa Louise; Day, John C.

    2016-08-01

    Removal of intrinsic brain tumors is a delicate process, where a high degree of specificity is required to remove all of the tumor tissue without damaging healthy brain. The accuracy of this process can be greatly enhanced by intraoperative guidance. Optical biopsies using Raman spectroscopy are a minimally invasive and lower-cost alternative to current guidance methods. A miniature Raman probe for performing optical biopsies of human brain tissue is presented. The probe allows sampling inside a conventional stereotactic brain biopsy system: a needle of length 200 mm and inner diameter of 1.8 mm. By employing a miniature stand-off Raman design, the probe removes the need for any additional components to be inserted into the brain. Additionally, the probe achieves a very low internal silica background while maintaining good collection of Raman signal. To illustrate this, the probe is compared with a Raman probe that uses a pair of optical fibers for collection. The miniature stand-off Raman probe is shown to collect a comparable number of Raman scattered photons, but the Raman signal to background ratio is improved by a factor of five at Raman shifts below ˜500 cm-1. The probe's suitability for use on tissue is demonstrated by discriminating between different types of healthy porcine brain tissue.

  15. Research on the photochemical kinetics process of gold nanoparticle-doped photopolymer system using Raman spectroscopy

    Science.gov (United States)

    Li, Ruoping; Yang, Jingliang; Li, Yanmeng; Han, Junhe; Huang, Mingju

    2016-10-01

    A photopolymer system doped with gold nanoparticles (Au NPs) was studied using Surface Enhanced Raman Scattering (SERS) technique in this work. In the system, polyvinyl alcohol is a binder, acrylamide and methylene-bisacrylamide are two monomers, methylene blue (MB) is a photosensitizer and triethanolamine is an initiator. Two types of Au NPs-- bare Au NPs with 13nm and 25nm diameter, and their corresponding SiO2 shell-isolated Au (Au@SiO2) NPs with 2nm shell thickness, were prepared and doped into the photopolymer for reducing the shrinkage of holograms. The shield of SiO2 shell avoids the dark reaction originating from electron transfer between Au NPs and MB molecules. More importantly, under 633nm laser excitation, the resonance Raman scattering of MB can be triggered, and the Raman signal of MB can be enhanced greatly due to the local enhanced electromagnetic field by Au@SiO2 NPs. Both of them made the in-situ Raman detection of the photopolymer more feasible. The experimental results not only show the excitation process of MB but also display the polymerization process of the photopolymer. In addition, the excitation rate of MB and the polymerization rate of monomers can also be obtained using their time Raman spectra. This provides an experimental tool for detecting the photochemical kinetics process of the photopolymer.

  16. Single-pulse coherent anti-Stokes Raman spectroscopy via fiber Bragg grating

    Science.gov (United States)

    Oh, Seung Ryeol; Park, Joo Hyun; Kwon, Won Sik; Kim, Jin Hwan; Kim, Kyung-Soo; Lee, Jae Yong; Kim, Soohyun

    2016-03-01

    Fiber Bragg grating is used in a variety of applications. In this study, we suggest compact, cost-effective coherent anti- Stokes Raman spectroscopy which is based on the pulse shaping methods via commercialized fiber Bragg grating. The experiment is performed incorporating a commercialized femtosecond pulse laser system (MICRA, Coherent) with a 100 mm length of 780-HP fiber which is inscribed 50 mm of Bragg grating. The pump laser for coherent anti-Stokes Raman spectroscopy has a bandwidth of 90 nm and central wavelength of 815 nm with a notch shaped at 785 nm. The positive chirped pulse is compensated by chirped mirror set. We compensate almost 14000 fs2 of positive group delay dispersion for the transform-limited pulse at the sample position. The pulse duration was 15 fs with average power of 50 mW, and showed an adequate notch shape. Finally, coherent anti-Stokes Raman signals are observed using a spectrometer (Jobin Yvon Triax320 and TE-cooled Andor Newton EMCCD). We obtained coherent anti-Stokes Raman signal of acetone sample which have Raman peak at the spectral finger-print region. In conclusion, the proposed method is more simple and cost-effective than the methods of previous research which use grating pairs and resonant photonic crystal slab. Furthermore, the proposed method can be used as endoscope application.

  17. A subcutaneous Raman needle probe.

    Science.gov (United States)

    Day, John C C; Stone, Nicholas

    2013-03-01

    Raman spectroscopy is a powerful tool for studying the biochemical composition of tissues and cells in the human body. We describe the initial results of a feasibility study to design and build a miniature, fiber optic probe incorporated into a standard hypodermic needle. This probe is intended for use in optical biopsies of solid tissues to provide valuable information of disease type, such as in the lymphatic system, breast, or prostate, or of such tissue types as muscle, fat, or spinal, when identifying a critical injection site. The optical design and fabrication of this probe is described, and example spectra of various ex vivo samples are shown.

  18. Raman spectroscopy of 'Bisphenol A'

    Science.gov (United States)

    Ullah, Ramzan; Zheng, Yuxiang

    2016-03-01

    Raman spectra (95 - 3000 cm-1) of 'Bisphenol A' are presented. Absorption peaks have been assigned by Density Functional Theory (DFT) with B3LYP 6 - 311 ++ G (3df, 3pd) and wB97XD 6 - 311 ++ G (3df, 3pd). B3LYP 6 - 311 ++ G (3df, 3pd) gives frequencies which are nearer to experimental frequencies than wB97XD 6 - 311 ++ G (3df, 3pd) which involves empirical dispersion. Scale factor for wB97XD 6 - 311 ++ G (3df, 3pd) is found out to be 0.95008 by least squares fit.

  19. Two-Photon Raman Gain in a Laser Driven Potassium Vapor

    Science.gov (United States)

    1996-02-01

    Stokes wave. With powerful laser beams, Raman scattering involving multiple pump and probe photons can appear, producing light at the subharmonics of the...laser fre- quency drifts. High-speed cavity length variations are corrected using a piezo - electrically driven mirror, while a rotating Brewsters...emergence of resonances at subharmonics of the ground-state splitting. I attribute these intensity dependent spectral features 8Recall that working with small

  20. Entangled valence electron-hole dynamics revealed by stimulated attosecond x-ray Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Healion, Daniel; Zhang, Yu; Biggs, Jason D.; Govind, Niranjan; Mukamel, Shaul

    2012-09-06

    We show that broadband x-ray pulses can create wavepackets of valence electrons and holes localized in the vicinity of a selected atom (nitrogen, oxygen or sulfur in cysteine) by resonant stimulated Raman scattering. The subsequent dynamics reveals highly correlated motions of entangled electrons and hole quasiparticles. This information goes beyond the time-dependent total charge density derived from x-ray diffraction.

  1. Raman investigation of ro-vibrational modes of interstitial H2 in Si

    Science.gov (United States)

    Koch, S. G.; Lavrov, E. V.; Weber, J.

    2012-08-01

    A Raman scattering study of ro-vibrational transitions Q(J) of the interstitial H2 in Si is presented. It is shown that the Q(2) mode of para hydrogen is coupled to the TAX phonon of Si. The mode appears in the spectra at temperatures above 200 K. The results presented also suggest that the Q(3) transition of ortho hydrogen is resonantly coupled to the OΓ phonon.

  2. Raman investigation of ro-vibrational modes of interstitial H{sub 2} in Si

    Energy Technology Data Exchange (ETDEWEB)

    Koch, S.G., E-mail: sandro.koch@physik.tu-dresden.de [Technische Universitaet Dresden, 01062 Dresden (Germany); Lavrov, E.V.; Weber, J. [Technische Universitaet Dresden, 01062 Dresden (Germany)

    2012-08-01

    A Raman scattering study of ro-vibrational transitions Q(J) of the interstitial H{sub 2} in Si is presented. It is shown that the Q(2) mode of para hydrogen is coupled to the TA{sub X} phonon of Si. The mode appears in the spectra at temperatures above 200 K. The results presented also suggest that the Q(3) transition of ortho hydrogen is resonantly coupled to the O{sub {Gamma}} phonon.

  3. Surface Plasmon Resonance Sensors Based on Polymer Optical Fiber

    Institute of Scientific and Technical Information of China (English)

    Rong-Sheng Zheng; Yong-Hua Lu; Zhi-Guo Xie; Jun Tao; Kai-Qun Lin; Hai Ming

    2008-01-01

    Surface Plasmon Resonance (SPR) is a powerful technique for directly sensing in biological studies, chemical detection and environmental pollution monitoring. In this paper, we present polymer optical fiber application in SPR sensors, including wavelength interrogation surface enhanced Raman scattering SPR sensor and surface enhanced Raman scattering (SERS) probe.Long-period fiber gratings are fabricated on single mode polymer optical fiber (POF) with 120 μm period and 50% duty cycle. The polarization characteristic of this kind of birefringent grating is studied. Theoretical analysis shows it will be advantageous in SPR sensing applications.

  4. Population transfer of a NaH molecule via stimulated Raman adiabatic passage

    Science.gov (United States)

    Zai, Jing-Bo; Zhan, Wei-Shen; Wang, Shuo; Dang, Hai-Ping; Han, Xiao

    2016-09-01

    The population transfer of a NaH molecule from the ground state {{X}1}{Σ+} to the target state {{A}1}{Σ+} via stimulated Raman adiabatic passage (STIRAP) is investigated. The results show that the intensity, delay time and detuning have a significant effect on population transfer. A large population transfer is observed with increased pump and Stokes intensity, especially when the pump and Stokes intensity match. Population transfer also depends on the delay time between the pump laser pulse and the Stokes laser pulse. The detuning of the two pulses influences the population transfer. Efficient population transfer can be realized under the resonant or two-photon resonant condition.

  5. Measurement of Wigner function via atomic beam deflection in Raman- Nath regime

    CERN Document Server

    Khosa, A H; Khosa, Ashfaq Hussain

    2002-01-01

    We propose a method for the reconstruction of photon statistics and hence the Wigner function of a quantized cavity field. The method is based on the measurement of momentum distribution of two level atoms after atom- field interaction in Raman-Nath regime. We reconstruct the photon statistics of the cavity field both the cases of resonant and off- resonant atom field interaction.. For the measurement of Wigner function we propose to displace the photon statistics of the cavity field. We successfully reconstruct the Wigner function of the Schrodinger-cat state in a straightforward manner by employing the proposed method without much mathematical manipulation of the experimental data.

  6. Raman Spectroscopic Studies of Methane Gas Hydrates

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.

    2009-01-01

    A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory.......A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory....

  7. Self-pulsation in Raman fiber amplifiers

    DEFF Research Database (Denmark)

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.......Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated....

  8. RAMAN-SPECTRA OF HUMAN DENTAL CALCULUS

    NARCIS (Netherlands)

    TSUDA, H; ARENDS, J

    1993-01-01

    Raman spectra of human dental calculus have been observed for the first time by use of micro-Raman spectroscopy. The spectral features of calculus were influenced easily by heating caused by laser irradiation. Therefore, the measurements were carried out at relatively low power (5 mW, 1-mu m spot si

  9. Raman spectroscopy: the gateway into tomorrow's virology.

    Science.gov (United States)

    Lambert, Phelps J; Whitman, Audy G; Dyson, Ossie F; Akula, Shaw M

    2006-06-28

    In the molecular world, researchers act as detectives working hard to unravel the mysteries surrounding cells. One of the researchers' greatest tools in this endeavor has been Raman spectroscopy. Raman spectroscopy is a spectroscopic technique that measures the unique Raman spectra for every type of biological molecule. As such, Raman spectroscopy has the potential to provide scientists with a library of spectra that can be used to unravel the makeup of an unknown molecule. However, this technique is limited in that it is not able to manipulate particular structures without disturbing their unique environment. Recently, a novel technology that combines Raman spectroscopy with optical tweezers, termed Raman tweezers, evades this problem due to its ability to manipulate a sample without physical contact. As such, Raman tweezers has the potential to become an incredibly effective diagnostic tool for differentially distinguishing tissue, and therefore holds great promise in the field of virology for distinguishing between various virally infected cells. This review provides an introduction for a virologist into the world of spectroscopy and explores many of the potential applications of Raman tweezers in virology.

  10. Raman spectroscopy: the gateway into tomorrow's virology

    Directory of Open Access Journals (Sweden)

    Dyson Ossie F

    2006-06-01

    Full Text Available Abstract In the molecular world, researchers act as detectives working hard to unravel the mysteries surrounding cells. One of the researchers' greatest tools in this endeavor has been Raman spectroscopy. Raman spectroscopy is a spectroscopic technique that measures the unique Raman spectra for every type of biological molecule. As such, Raman spectroscopy has the potential to provide scientists with a library of spectra that can be used to unravel the makeup of an unknown molecule. However, this technique is limited in that it is not able to manipulate particular structures without disturbing their unique environment. Recently, a novel technology that combines Raman spectroscopy with optical tweezers, termed Raman tweezers, evades this problem due to its ability to manipulate a sample without physical contact. As such, Raman tweezers has the potential to become an incredibly effective diagnostic tool for differentially distinguishing tissue, and therefore holds great promise in the field of virology for distinguishing between various virally infected cells. This review provides an introduction for a virologist into the world of spectroscopy and explores many of the potential applications of Raman tweezers in virology.

  11. Raman spectroscopy and its urological applications

    Directory of Open Access Journals (Sweden)

    Vishwanath S Hanchanale

    2008-01-01

    Conclusion: Raman spectroscopy is an exciting tool for real-time diagnosis and in vivo evaluation of living tissue. The potential applications of Raman spectroscopy may herald a new future in the management of various malignant, premalignant, and other benign conditions in urology.

  12. Raman spectra of human dentin mineral

    NARCIS (Netherlands)

    Tsuda, H; Ruben, J; Arends, J

    1996-01-01

    Human dentin mineral has been investigated by using micro-Raman spectroscopy. Fluorescence and thermal problems were largely avoided by preparing dentin samples by grinding and ultrasonic agitation in acetone. The Raman spectral features were consistent with those of impure hydroxyapatite containing

  13. Rashba realization: Raman with RF

    Science.gov (United States)

    Campbell, D L; Spielman, I B

    2016-01-01

    We theoretically explore a Rashba spin–orbit coupling scheme which operates entirely in the absolute ground state manifold of an alkali atom, thereby minimizing all inelastic processes. An energy gap between ground eigenstates of the proposed coupling can be continuously opened or closed by modifying laser polarizations. Our technique uses far-detuned ‘Raman’ laser coupling to create the Rashba potential, which has the benefit of low spontaneous emission rates. At these detunings, the Raman matrix elements that link mF magnetic sublevel quantum numbers separated by two are also suppressed. These matrix elements are necessary to produce the Rashba Hamiltonian within a single total angular momentum f manifold. However, the far-detuned Raman couplings can link the three XYZ states familiar to quantum chemistry, which possess the necessary connectivity to realize the Rashba potential. We show that these XYZ states are essentially the hyperfine spin eigenstates of 87Rb dressed by a strong radio-frequency magnetic field. PMID:27524933

  14. Applications of Raman spectroscopy to gemology.

    Science.gov (United States)

    Bersani, Danilo; Lottici, Pier Paolo

    2010-08-01

    Being nondestructive and requiring short measurement times, a low amount of material, and no sample preparation, Raman spectroscopy is used for routine investigation in the study of gemstone inclusions and treatments and for the characterization of mounted gems. In this work, a review of the use of laboratory Raman and micro-Raman spectrometers and of portable Raman systems in the gemology field is given, focusing on gem identification and on the evaluation of the composition, provenance, and genesis of gems. Many examples are shown of the use of Raman spectroscopy as a tool for the identification of imitations, synthetic gems, and enhancement treatments in natural gemstones. Some recent developments are described, with particular attention being given to the semiprecious stone jade and to two important organic materials used in jewelry, i.e., pearls and corals.

  15. Raman-gain induced loss-compensation in whispering-gallery-microresonators and single-nanoparticle detection with whispering-gallery Raman-microlasers

    CERN Document Server

    Ozdemir, Sahin Kaya; Yang, Xu; Peng, Bo; Yilmaz, Huzeyfe; He, Lina; Monifi, Faraz; Long, Gui Lu; Yang, Lan

    2014-01-01

    Recently optical whispering-gallery-mode resonators (WGMRs) have emerged as promising platforms to achieve label-free detection of nanoscale objects and to reach single molecule sensitivity. The ultimate detection performance of WGMRs are limited by energy dissipation in the material they are fabricated from. Up to date, to improve detection limit, either rare-earth ions are doped into the WGMR to compensate losses or plasmonic resonances are exploited for their superior field confinement. Here, we demonstrate, for the first time, enhanced detection of single-nanoparticle induced mode-splitting in a silica WGMR via Raman-gain assisted loss-compensation and WGM Raman lasing. Notably, we detected and counted individual dielectric nanoparticles down to a record low radius of 10 nm by monitoring a beatnote signal generated when split Raman lasing lines are heterodyne-mixed at a photodetector. This dopant-free scheme retains the inherited biocompatibility of silica, and could find widespread use for sensing in bio...

  16. Classification of oral cancers using Raman spectroscopy of serum

    Science.gov (United States)

    Sahu, Aditi; Talathi, Sneha; Sawant, Sharada; Krishna, C. Murali

    2014-03-01

    Oral cancers are the sixth most common malignancy worldwide, with low 5-year disease free survival rates, attributable to late detection due to lack of reliable screening modalities. Our in vivo Raman spectroscopy studies have demonstrated classification of normal and tumor as well as cancer field effects (CFE), the earliest events in oral cancers. In view of limitations such as requirement of on-site instrumentation and stringent experimental conditions of this approach, feasibility of classification of normal and cancer using serum was explored using 532 nm excitation. In this study, strong resonance features of β-carotenes, present differentially in normal and pathological conditions, were observed. In the present study, Raman spectra of sera of 36 buccal mucosa, 33 tongue cancers and 17 healthy subjects were recorded using Raman microprobe coupled with 40X objective using 785 nm excitation, a known source of excitation for biomedical applications. To eliminate heterogeneity, average of 3 spectra recorded from each sample was subjected to PC-LDA followed by leave-one-out-cross-validation. Findings indicate average classification efficiency of ~70% for normal and cancer. Buccal mucosa and tongue cancer serum could also be classified with an efficiency of ~68%. Of the two cancers, buccal mucosa cancer and normal could be classified with a higher efficiency. Findings of the study are quite comparable to that of our earlier study, which suggest that there exist significant differences, other than β- carotenes, between normal and cancerous samples which can be exploited for the classification. Prospectively, extensive validation studies will be undertaken to confirm the findings.

  17. Influence of the ordered structure of short-chain polymer molecule all-trans-β-carotene on Raman scattering cross section in liquid

    Institute of Scientific and Technical Information of China (English)

    Qu Guan-Nan; OuYang Shun-Li; Wang Wei-Wei; Li Zuo-Wei; Sun Cheng-Lin; Men Zhi-Wei

    2011-01-01

    We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures. The results demonstrated that the Raman scattering cross section (RSCS) of short-chain polymer all-trans-β-carotene is extremely high in liquid. Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions. Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure. All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties, which lead to large RSCS in the solvent with large density and low concentration at low temperature.

  18. CuO-chain Raman scattering and photoinduced metastability in YBa2Cu3Ox

    DEFF Research Database (Denmark)

    Käll, M.; Osada, M.; Kakihana, M.

    1998-01-01

    superconductivity effects, indicating photon-assisted oxygen ordering or electron vacancy capture. By comparing Raman and x-ray diffraction data we establish a correlation between the stability of the photoinduced state and the oxygen-ordering kinetics in the CuO chains.......Raman measurements in YBa2Cu3Ox (x=6.72-6.82) high-T-c superconductors reveal intense phonon scattering due to an electronic resonance localized near oxygen vacancies on the CuO chains. Below room temperature the resonance can be photobleached in a manner similar to reported persistent photoinduced...

  19. Fourier transform Raman approach to structural correlation in hemoglobin derivatives.

    Science.gov (United States)

    Venkatesh, B; Ramasamy, S; Mylrajan, M; Asokan, R; Manoharan, P T; Rifkind, J M

    1999-07-01

    In order to obtain information on the structural aspects of hemoglobin (Hb), Fourier transform Raman (FT-R) measurements on various ferrous, ferric derivatives and nickel reconstituted Hb (NiHb) has been made. FT-R spectra for these derivatives were obtained by laser excitation in the near infrared region (NIR) (1064 nm) whereby the wave-number region (600-1700 cm-1) related to both porphyrin ring modes and some globin modes were monitored. Comparison of various modes was made based on previous resonance Raman (RR) results. The wave-number shifts with respect to changes in oxidation state and spin state are very similar to those observed by RR. Additional bands at 1654, 1459, and 1003 cm-1 for deoxyHb and at 1656, 1454, and 1004 cm-1 for oxy Hb can be correlated to globin modes. The shift in the position of these bands for the binding of oxygen can be related to changes in conformation during the transformation. The presence of two distinct sites in NiHb could be monitored by the use of FT-R technique.

  20. Surface enhanced Raman scattering (SERS) fabrics for trace analysis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jun [National Engineering Laboratory for Advanced Yarn and Fabric Formation and Clean Production, Wuhan Textile University, Wuhan 430073 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials & Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education & College of Chemistry & Chemical Engineering, Hubei University, Wuhan 430062 (China); Zhou, Ji [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials & Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education & College of Chemistry & Chemical Engineering, Hubei University, Wuhan 430062 (China); Tang, Bin, E-mail: bin.tang@deakin.edu.au [National Engineering Laboratory for Advanced Yarn and Fabric Formation and Clean Production, Wuhan Textile University, Wuhan 430073 (China); Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216 (Australia); Zeng, Tian; Li, Yaling [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials & Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education & College of Chemistry & Chemical Engineering, Hubei University, Wuhan 430062 (China); Li, Jingliang [Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216 (Australia); Ye, Yong, E-mail: yeyong@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials & Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education & College of Chemistry & Chemical Engineering, Hubei University, Wuhan 430062 (China); Wang, Xungai [National Engineering Laboratory for Advanced Yarn and Fabric Formation and Clean Production, Wuhan Textile University, Wuhan 430073 (China); Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216 (Australia)

    2016-11-15

    Highlights: • Gold nanoparticles are in-situ synthesized on silk fabrics by heating. • Flexible silk fabrics with gold nanoparticles are used for surface-enhanced Raman scattering (SERS). • SERS activities of silk fabrics with different gold contents are investigated. - Abstract: Flexible SERS active substrates were prepared by modification of silk fabrics with gold nanoparticles. Gold nanoparticles were in-situ synthesized after heating the silk fabrics immersed in gold ion solution. Localized surface plasmon resonance (LSPR) properties of the treated silk fabrics varied as the concentration of gold ions changed, in relation to the morphologies of gold nanoparticles on silk. In addition, X-ray diffraction (XRD) was used to observe the structure of the gold nanoparticle treated silk fabrics. The SERS enhancement effect of the silk fabrics treated with gold nanoparticles was evaluated by collecting Raman signals of different concentrations of p-aminothiophenol (PATP), 4-mercaptopyridine (4-MPy) and crystal violet (CV) solutions. The results demonstrate that the silk fabrics corresponding to 0.3 and 0.4 mM of gold ions possess high SERS activity compared to the other treated fabrics. It is suggested that both the gold content and morphologies of gold nanoparticles dominate the SERS effect of the treated silk fabrics.

  1. Wide-field Raman imaging for bone detection in tissue.

    Science.gov (United States)

    Papour, Asael; Kwak, Jin Hee; Taylor, Zach; Wu, Benjamin; Stafsudd, Oscar; Grundfest, Warren

    2015-10-01

    Inappropriate bone growth in soft tissue can occur after trauma to a limb and can cause a disruption to the healing process. This is known as Heterotopic Ossification (HO) in which regions in the tissue start to mineralize and form microscopic bone-like structures. These structures continue to calcify and develop into large, non-functional bony masses that cause pain, limit limb movement, and expose the tissue to reoccurring infections; in the case of open wounds this can lead to amputation as a result of a failed wound. Both Magnetic Resonance Imaging (MRI) and X-ray imaging have poor sensitivity and specificity for the detection of HO, thus delaying therapy and leading to poor patient outcomes. We present a low-power, fast (1 frame per second) optical Raman imaging system with a large field of view (1 cm(2)) that can differentiate bone tissue from soft tissue without spectroscopy, this in contrast to conventional Raman microscopy systems. This capability may allow for the development of instrumentation which permits bedside diagnosis of HO.

  2. Coherent anti-Stokes Raman scattering under electric field stimulation

    Science.gov (United States)

    Capitaine, Erwan; Ould Moussa, Nawel; Louot, Christophe; Lefort, Claire; Pagnoux, Dominique; Duclère, Jean-René; Kaneyasu, Junya F.; Kano, Hideaki; Duponchel, Ludovic; Couderc, Vincent; Leproux, Philippe

    2016-12-01

    We introduce an experiment using electro-CARS, an electro-optical method based on the combination of ultrabroadband multiplex coherent anti-Stokes Raman scattering (M-CARS) spectroscopy and electric field stimulation. We demonstrate that this method can effectively discriminate the resonant CARS signal from the nonresonant background owing to a phenomenon of molecular orientation in the sample medium. Such molecular orientation is intrinsically related to the induction of an electric dipole moment by the applied static electric field. Evidence of the electro-CARS effect is obtained with a solution of n -alkanes (CnH2 n +2 , 15 ≤n ≤40 ), for which an enhancement of the CARS signal-to-noise ratio is achieved in the case of CH2 and CH3 symmetric/asymmetric stretching vibrations. Additionally, an electric-field-induced second-harmonic generation experiment is performed in order to corroborate the orientational organization of molecules due to the electric field excitation. Finally, we use a simple mathematical approach to compare the vibrational information extracted from electro-CARS measurements with spontaneous Raman data and to highlight the impact of electric stimulation on the vibrational signal.

  3. Efficient Raman Sideband Generation in a Coherent Atomic Medium

    CERN Document Server

    Huss, A F; Lammegger, R; Korsunsky, E A; Windholz, L

    2000-01-01

    We demonstrate the efficient generation of Raman sidebands in a medium coherently prepared in a dark state by continuous-wave low-intensity laser radiation. Our experiment is performed in sodium vapor excited in $\\Lambda $ configuration on the D$_{1}$ line by two laser fields of resonant frequencies $\\omega_{1}$ and $\\omega_{2}$, and probed by a third field $% \\omega_{3}$. First-order sidebands for frequencies $\\omega_{1}$, $\\omega_{2}$ and up to the third-order sidebands for frequency $\\omega_{3}$ are observed. The generation starts at a power as low as 10 microwatt for each input field. Dependencies of the intensities of both input and generated waves on the frequency difference ($\\omega_{1}-\\omega_{2}$), on the frequency $\\omega_{3}$ and on the optical density are investigated.

  4. Raman free-electron laser with a coaxial wiggler

    Science.gov (United States)

    Farokhi, B.; Maraghechi, B.; Willett, J. E.

    2000-10-01

    A one-dimensional theory of the stimulated Raman scattering mechanism for a coaxial free-electron laser (FEL) is developed. The beam-frame FEL dispersion relation and a formula for the lab-frame spatial growth rate are derived. A numerical study of the growth rate for the coaxial wiggler is made and compared with that for the helical wiggler. Except for a part of the group II orbits, the growth rate is found to be less than the helical wiggler. Relativistic effects due to the transverse oscillation of electrons in the wiggler field prevent the FEL operation from approaching magnetoresonance. In the absence of these relativistic mass effects, the calculations show a magnetoresonance associated with the first spatial harmonic and a much narrower resonance at the third spatial harmonic.

  5. Coherent anti-Stokes Raman scattering microscopy of single nanodiamonds.

    Science.gov (United States)

    Pope, Iestyn; Payne, Lukas; Zoriniants, George; Thomas, Evan; Williams, Oliver; Watson, Peter; Langbein, Wolfgang; Borri, Paola

    2014-11-01

    Nanoparticles have attracted enormous attention for biomedical applications as optical labels, drug-delivery vehicles and contrast agents in vivo. In the quest for superior photostability and biocompatibility, nanodiamonds are considered one of the best choices due to their unique structural, chemical, mechanical and optical properties. So far, mainly fluorescent nanodiamonds have been utilized for cell imaging. However, their use is limited by the efficiency and costs in reliably producing fluorescent defect centres with stable optical properties. Here, we show that single non-fluorescing nanodiamonds exhibit strong coherent anti-Stokes Raman scattering (CARS) at the sp(3) vibrational resonance of diamond. Using correlative light and electron microscopy, the relationship between CARS signal strength and nanodiamond size is quantified. The calibrated CARS signal in turn enables the analysis of the number and size of nanodiamonds internalized in living cells in situ, which opens the exciting prospect of following complex cellular trafficking pathways quantitatively.

  6. Coherent anti-Stokes Raman scattering microscopy of single nanodiamonds

    Science.gov (United States)

    Pope, Iestyn; Payne, Lukas; Zoriniants, George; Thomas, Evan; Williams, Oliver; Watson, Peter; Langbein, Wolfgang; Borri, Paola

    2014-11-01

    Nanoparticles have attracted enormous attention for biomedical applications as optical labels, drug-delivery vehicles and contrast agents in vivo. In the quest for superior photostability and biocompatibility, nanodiamonds are considered one of the best choices due to their unique structural, chemical, mechanical and optical properties. So far, mainly fluorescent nanodiamonds have been utilized for cell imaging. However, their use is limited by the efficiency and costs in reliably producing fluorescent defect centres with stable optical properties. Here, we show that single non-fluorescing nanodiamonds exhibit strong coherent anti-Stokes Raman scattering (CARS) at the sp3 vibrational resonance of diamond. Using correlative light and electron microscopy, the relationship between CARS signal strength and nanodiamond size is quantified. The calibrated CARS signal in turn enables the analysis of the number and size of nanodiamonds internalized in living cells in situ, which opens the exciting prospect of following complex cellular trafficking pathways quantitatively.

  7. Q-branch Raman scattering and modern kinetic thoery

    Energy Technology Data Exchange (ETDEWEB)

    Monchick, L. [The Johns Hopkins Univ., Laurel, MD (United States)

    1993-12-01

    The program is an extension of previous APL work whose general aim was to calculate line shapes of nearly resonant isolated line transitions with solutions of a popular quantum kinetic equation-the Waldmann-Snider equation-using well known advanced solution techniques developed for the classical Boltzmann equation. The advanced techniques explored have been a BGK type approximation, which is termed the Generalized Hess Method (GHM), and conversion of the collision operator to a block diagonal matrix of symmetric collision kernels which then can be approximated by discrete ordinate methods. The latter method, which is termed the Collision Kernel method (CC), is capable of the highest accuracy and has been used quite successfully for Q-branch Raman scattering. The GHM method, not quite as accurate, is applicable over a wider range of pressures and has proven quite useful.

  8. Finite-duration Seeding Effects in Powerful Backward Raman Amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    N.A. Yampolsky; V.M. Malkin; N.J. Fisch

    2003-07-14

    In the process of backward Raman amplification (BRA), the leading layers of the seed laser pulse can shadow the rear layers, thus weakening the effective seeding power and affecting parameters of output pulses in BRA. We study this effect numerically and also analytically by approximating the pumped pulse by the ''*-pulse'' manifold of self-similar solutions. We determine how the pumped pulse projection moves within the *-pulse manifold, and describe quantitatively the effective seeding power evolution. Our results extend the quantitative theory of BRA to regimes where the effective seeding power varies substantially during the amplification. These results might be of broader interest, since the basic equations, are general equations for resonant 3-wave interactions.

  9. Dependence of Raman and absorption spectra of stacked bilayer MoS2 on the stacking orientation.

    Science.gov (United States)

    Park, Seki; Kim, Hyun; Kim, Min Su; Han, Gang Hee; Kim, Jeongyong

    2016-09-19

    Stacked bilayer molybdenum disulfide (MoS2) exhibits interesting physical properties depending on the stacking orientation and interlayer coupling strength. Although optical properties, such as photoluminescence, Raman, and absorption properties, are largely dependent on the interlayer coupling of stacked bilayer MoS2, the origin of variations in these properties is not clearly understood. We performed comprehensive confocal Raman and absorption mapping measurements to determine the dependence of these spectra on the stacking orientation of bilayer MoS2. The results indicated that with 532-nm laser excitation, the Raman scattering intensity gradually increased upon increasing the stacking angle from 0° to 60°, whereas 458-nm laser excitation resulted in the opposite trend of decreasing Raman intensity with increasing stacking angle. This opposite behavior of the Raman intensity dependence was explained by the varying resonance condition between the Raman excitation wavelength and C exciton absorption energy of bilayer MoS2. Our work sheds light on the intriguing effect of the subtle interlayer interaction in stacked MoS2 bilayers on the resulting optical properties.

  10. Characterization of Small-Diameter Carbon Nanotubes and Carbon Nanocaps on SiC(000\\bar{1}) Using Raman Spectroscopy

    Science.gov (United States)

    Maruyama, Takahiro; Shiraiwa, Tomoyuki; Fujita, Naomi; Kawamura, Yasuyuki; Naritsuka, Shigeya; Kusunoki, Michiko

    2006-09-01

    The Raman spectra of carbon nanotubes (CNTs) formed on a 6H-SiC(000\\bar{1}) C-face substrate by surface decomposition were acquired using a 1064 nm Nd:YAG laser as the excitation source. Intense radial-breathing-mode Raman bands were successfully detected under resonant excitation from CNTs formed by the surface decomposition of SiC. Fine CNTs having diameters between 0.7 and 1.3 nm were observed on SiC after heating at 1700 °C in a vacuum electric furnace. These diameters are considerably smaller than those previously observed for CNTs grown by this technique.

  11. Rotating samples in FT-RAMAN spectrometers

    Science.gov (United States)

    De Paepe, A. T. G.; Dyke, J. M.; Hendra, P. J.; Langkilde, F. W.

    1997-11-01

    It is customary to rotate samples in Raman spectroscopy to avoid absorption or sample heating. In FT-Raman experiments the rotation is always shown (typically 30-60 rpm) because higher speeds are thought to generate noise in the spectra. In this article we show that more rapid rotation is possible. A tablet containing maleic acid and one made up of sub-millimetre silica particles with metoprolol succinate as active ingredient were rotated at different speeds, up to 6760 rpm. The FT-Raman spectra were recorded and studied. We conclude that it is perfectly acceptable to rotate samples up to 1500 rpm.

  12. Implementation of Deep Ultraviolet Raman Spectroscopy

    DEFF Research Database (Denmark)

    Liu, Chuan

    spectrometer that could be obtained for the available amount of money. Compared with a traditional Raman system working in the range of visible or near Infrared, the chosen DUV Raman system requires more stringent conditions for the optical components. The various DUV optical components have been described...... spectra of the gasoline samples. It is virtually unimportant what the rest of the sample consisted of. The most intense characteristic band is located at 1381 cm-1. The Raman spectra of home-made artificial gasoline mixtures - with gradually increasing Naphthalene contents - can be used to determine...

  13. Raman spectroscopy as a tool for reagent free estimation

    CERN Document Server

    Kumar, S

    2014-01-01

    We present results of Raman spectroscopic studies of urine to determine the suitability of near-infrared Raman spectroscopy for quantitative estimation of urinary urea. The Raman spectra were acquired from the urine samples with an inbuilt Raman spectroscopy setup that employs a 785-nm diode laser as the Raman excitation source. A multivariate algorithm based on partial least square (PLS) regression was developed to predict the concentration of urea depending on the measured sets of Raman spectra and the reference urea concentration. The computed results shows that Raman spectroscopy in amalgamation with PLS-based multivariate chemometric algorithm can detect urea in urine samples with an accuracy of >90 %.

  14. Experiments with Helmholtz Resonators.

    Science.gov (United States)

    Greenslade, Thomas B., Jr.

    1996-01-01

    Presents experiments that use Helmholtz resonators and have been designed for a sophomore-level course in oscillations and waves. Discusses the theory of the Helmholtz resonator and resonance curves. (JRH)

  15. MRI (Magnetic Resonance Imaging)

    Science.gov (United States)

    ... and Procedures Medical Imaging MRI (Magnetic Resonance Imaging) MRI (Magnetic Resonance Imaging) Share Tweet Linkedin Pin it More sharing options ... usually given through an IV in the arm. MRI Research Programs at FDA Magnetic Resonance Imaging (MRI) ...

  16. Raman and surface-enhanced Raman scattering (SERS) studies of the thrombin-binding aptamer.

    Science.gov (United States)

    Wu, Tsai-Chin; Vasudev, Milana; Dutta, Mitra; Stroscio, Michael A

    2013-06-01

    Surface-enhanced Raman scattering is used to study the Raman spectra and peak shifts the thrombin-binding aptamer (TBA) on substrates having two different geometries; one with a single stranded sequence and one with double stranded sequence. The Raman signals of the deoxyribonucleic acids on both substrates are enhanced and specific peaks of bases are identified. These results are highly reproducible and have promising applications in low cost nucleic acid detection.

  17. Regenerative feedback resonant circuit

    Science.gov (United States)

    Jones, A. Mark; Kelly, James F.; McCloy, John S.; McMakin, Douglas L.

    2014-09-02

    A regenerative feedback resonant circuit for measuring a transient response in a loop is disclosed. The circuit includes an amplifier for generating a signal in the loop. The circuit further includes a resonator having a resonant cavity and a material located within the cavity. The signal sent into the resonator produces a resonant frequency. A variation of the resonant frequency due to perturbations in electromagnetic properties of the material is measured.

  18. Optical nanoantennas for multiband surface-enhanced infrared and raman spectroscopy

    KAUST Repository

    D'Andrea, Cristiano

    2013-04-23

    In this article we show that linear nanoantennas can be used as shared substrates for surface-enhanced Raman and infrared spectroscopy (SERS and SEIRS, respectively). This is done by engineering the plasmonic properties of the nanoantennas, so to make them resonant in both the visible (transversal resonance) and the infrared (longitudinal resonance), and by rotating the excitation field polarization to selectively take advantage of each resonance and achieve SERS and SEIRS on the same nanoantennas. As a proof of concept, we have fabricated gold nanoantennas by electron beam lithography on calcium difluoride (1-2 μm long, 60 nm wide, 60 nm high) that exhibit a transverse plasmonic resonance in the visible (640 nm) and a particularly strong longitudinal dipolar resonance in the infrared (tunable in the 1280-3100 cm -1 energy range as a function of the length). SERS and SEIRS detection of methylene blue molecules adsorbed on the nanoantenna\\'s surface is accomplished, with signal enhancement factors of 5 × 102 for SERS (electromagnetic enhancement) and up to 105 for SEIRS. Notably, we find that the field enhancement provided by the transverse resonance is sufficient to achieve SERS from single nanoantennas. Furthermore, we show that by properly tuning the nanoantenna length the signals of a multitude of vibrational modes can be enhanced with SEIRS. This simple concept of plasmonic nanosensor is highly suitable for integration on lab-on-a-chip schemes for label-free chemical and biomolecular identification with optimized performances. © 2013 American Chemical Society.

  19. Design of an 1800 nm Raman Amplifier

    DEFF Research Database (Denmark)

    Svane, Ask Sebastian; Rottwitt, Karsten

    in the pump power requirement and deteriorated noise properties. Here we demonstrate a Raman amplifier designed for signal wavelengths around 1800 nm. The amplification fiber is an OFS PM Raman fiber, and is pumped by a Raman fiber laser emitting at 1680 nm [4]. The amplifier was pumped co......-polarized and backward, with respect to the singal. In Fig. 2 a measured Raman on/off gain exceeding 9 dB for 285 mW of injected pump power is obtained in a 4.35 km long fiber. A broadband supercontinuum source was used as a signal from 1700 nm to 1900 nm.......Different approaches are being explored to increase the capacity of communication systems [1,2], both long and short range systems. One approach is by exploiting new optical wavelength bands, outside the conventional communication window from 1530 nm to 1625 nm. Hollow core fibers have been...

  20. High pressure Raman scattering of silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Khachadorian, Sevak; Scheel, Harald; Thomsen, Christian [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, 10623 Berlin (Germany); Papagelis, Konstantinos [Materials Science Department, University of Patras, 26504 Patras (Greece); Colli, Alan [Nokia Research Centre, 21 J J Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Ferrari, Andrea C, E-mail: khachadorian@physik.tu-berlin.de [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom)

    2011-05-13

    We study the high pressure response, up to 8 GPa, of silicon nanowires (SiNWs) with {approx} 15 nm diameter, by Raman spectroscopy. The first order Raman peak shows a superlinear trend, more pronounced compared to bulk Si. Combining transmission electron microscopy and Raman measurements we estimate the SiNWs' bulk modulus and the Grueneisen parameters. We detect an increase of Raman linewidth at {approx} 4 GPa, and assign it to pressure induced activation of a decay process into LO and TA phonons. This pressure is smaller compared to the {approx} 7 GPa reported for bulk Si. We do not observe evidence of phase transitions, such as discontinuities or change in the pressure slopes, in the investigated pressure range.

  1. Self-pulsation in Raman fiber amplifiers

    OpenAIRE

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.

  2. Mobile Raman spectroscopy in astrobiology research.

    Science.gov (United States)

    Vandenabeele, Peter; Jehlička, Jan

    2014-12-13

    Raman spectroscopy has proved to be a very useful technique in astrobiology research. Especially, working with mobile instrumentation during fieldwork can provide useful experiences in this field. In this work, we provide an overview of some important aspects of this research and, apart from defining different types of mobile Raman spectrometers, we highlight different reasons for this research. These include gathering experience and testing of mobile instruments, the selection of target molecules and to develop optimal data processing techniques for the identification of the spectra. We also identify the analytical techniques that it would be most appropriate to combine with Raman spectroscopy to maximize the obtained information and the synergy that exists with Raman spectroscopy research in other research areas, such as archaeometry and forensics.

  3. Raman assisted lightwave synthesized frequency sweeper

    DEFF Research Database (Denmark)

    Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2010-01-01

    We present a Lightwave Synthesized Frequency Sweeper comprising a Raman amplifier for loss compensation. The generated pulse train contains 123 pulses and has a flat signal level as well as a low noise level.......We present a Lightwave Synthesized Frequency Sweeper comprising a Raman amplifier for loss compensation. The generated pulse train contains 123 pulses and has a flat signal level as well as a low noise level....

  4. PM Raman fiber laser at 1679 nm

    DEFF Research Database (Denmark)

    Svane, Ask Sebastian; Rottwitt, Karsten

    2012-01-01

    We demonstrate a PM Raman fiber laser emitting light at 1679 nm. The laser has an slope efficiency of 67 % and an output power of more than 275mWwith a 27 pm linewidth.......We demonstrate a PM Raman fiber laser emitting light at 1679 nm. The laser has an slope efficiency of 67 % and an output power of more than 275mWwith a 27 pm linewidth....

  5. Raman Model Predicting Hardness of Covalent Crystals

    OpenAIRE

    Zhou, Xiang-Feng; Qian, Quang-Rui; Sun, Jian; Tian, Yongjun; Wang, Hui-Tian

    2009-01-01

    Based on the fact that both hardness and vibrational Raman spectrum depend on the intrinsic property of chemical bonds, we propose a new theoretical model for predicting hardness of a covalent crystal. The quantitative relationship between hardness and vibrational Raman frequencies deduced from the typical zincblende covalent crystals is validated to be also applicable for the complex multicomponent crystals. This model enables us to nondestructively and indirectly characterize the hardness o...

  6. Ice thickness measurements by Raman scattering

    CERN Document Server

    Pershin, Sergey M; Klinkov, Vladimir K; Yulmetov, Renat N; Bunkin, Alexey F

    2014-01-01

    A compact Raman LIDAR system with a spectrograph was used for express ice thickness measurements. The difference between the Raman spectra of ice and liquid water is employed to locate the ice-water interface while elastic scattering was used for air-ice surface detection. This approach yields an error of only 2 mm for an 80-mm-thick ice sample, indicating that it is promising express noncontact thickness measurements technique in field experiments.

  7. Single-pulse stimulated Raman scattering spectroscopy

    CERN Document Server

    Frostig, Hadas; Natan, Adi; Silberberg, Yaron

    2010-01-01

    We demonstrate the acquisition of stimulated Raman scattering spectra with the use of a single femtosecond pulse. High resolution vibrational spectra are obtained by shifting the phase of a narrow band of frequencies in the broadband input pulse spectrum, using spectral shaping. The vibrational spectrum is resolved by examining the amplitude features formed in the spectrum after interaction with the sample. Using this technique, low frequency Raman lines (<100cm^-1) are resolved in a straightforward manner.

  8. Raman spectroscopy of single quantum well wires

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    We used the micro-Raman spectroscopy to investigate the V-grooved quantum well wires (QWWs), and first observed and assigned the Raman spectra of single QWW. They were the disorder induced modes at 223 and 243 cm-1, confined LO mode of GaAs QWW at 267 cm1, and higher order peaks of disorder induced modes at 488 and 707 cm-1.

  9. Monitoring lipid accumulation in the green microalga Botryococcus braunii with frequency-modulated stimulated Raman scattering

    Science.gov (United States)

    Wang, Chun-Chin; Chandrappa, Dayananda; Smirnoff, Nicholas; Moger, Julian

    2015-03-01

    The potential of microalgae as a source of renewable energy has received considerable interest because they can produce lipids (fatty acids and isoprenoids) that can be readily converted into biofuels. However, significant research in this area is required to increase yields to make this a viable renewable source of energy. An analytical tool that could provide quantitative in situ spectroscopic analysis of lipids synthesis in individual microalgae would significantly enhance our capability to understand the synthesis process at the cellular level and lead to the development of strategies for increasing yield. Stimulated Raman scattering (SRS) microscopy has great potential in this area however, the pump-probe signal from two-color two-photon absorption of pigments (chlorophyll and carotenoids) overwhelm the SRS signal and prevent its application. Clearly, the development of a background suppression technique is of significant value for this important research area. To overcome the limitation of SRS in pigmented specimens, we establish a frequency-modulated stimulated Raman scattering (FM-SRS) microscopy that eliminates the non-Raman background by rapidly toggling on-and-off the targeted Raman resonance. Moreover, we perform the background-free imaging and analysis of intracellular lipid droplets and extracellular hydrocarbons in a green microalga with FM-SRS microscopy. We believe that FM-SRS microscopy demonstrates the potential for many applications in pigmented cells and provides the opportunity for improved selective visualization of the chemical composition of algae and plants

  10. Experimental and Theoretical Study on the Surface Enhanced Raman Mechanism of Pristine and Chemically Doped Graphene

    Science.gov (United States)

    Feng, Simin; Dos Santos, Maria C.; Lu, Ruitao; Elias, Ana L.; Perea-Lopez, Nestor; Terrones, Mauricio

    2014-03-01

    It is demonstrated that graphene could be used as an efficient surface-enhanced Raman spectroscopy (SERS) substrate. Recently, our group has also shown that chemically doped graphene can improve the SERS signal of pristine graphene. Here we present an experimental and theoretical study on the SERS mechanism for both pristine (PG) and Nitrogen-doped graphene (NG). Large-area and highly-crystalline monolayer PG and NG sheets have been synthesized. Common molecules, such as Rhodamine B, Crystal Violet, Methylene Blue and Melamine were used as Raman probes using different laser excitation energies. It was observed that for each molecule, specific laser energy exhibits large intensity Raman signals when compared to others. More importantly, some signals can be detected even for concentrations as low as 10-8 M, which provides excellent molecular sensing properties. Then the system was modeled using DFT-B3LYP/6-31(d,p) and the Mulliken population analysis was used to calculate the net charge on the adsorbed molecules. By comparing the cases of PG and NG, our preliminary results suggest that stronger Raman enhancement of NG would likely be coming from the resonance of EF of graphene and the LUMO level of the adsorbed molecules.

  11. Raman spectroscopy of organic dyes adsorbed on pulsed laser deposited silver thin films

    Energy Technology Data Exchange (ETDEWEB)

    Fazio, E.; Neri, F. [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universitá di Messina, V.le F. Stagno d’Alcontres 31, I-98166, Messina, Italy. (Italy); Valenti, A. [Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Universitá di Messina, V.le F. Stagno d’Alcontres 31, I-98166, Messina, Italy. (Italy); Ossi, P.M., E-mail: paolo.ossi@polimi.it [Dipartimento di Energia, Politecnico di Milano, via Ponzio 34-3, 20133 Milano, Italy. (Italy); Trusso, S.; Ponterio, R.C. [CNR-Istituto per i Processi Chimico-Fisici Sede di Messina, V.le F. Stagno d’Alcontres 37, I-98158 Messina, Italy. (Italy)

    2013-08-01

    The results of a surface-enhanced Raman scattering (SERS) study performed on representative organic and inorganic dyes adsorbed on silver nanostructured thin films are presented and discussed. Silver thin films were deposited on glass slides by focusing the beam from a KrF excimer laser (wavelength 248 nm, pulse duration 25 ns) on a silver target and performing the deposition in a controlled Ar atmosphere. Clear Raman spectra were acquired for dyes such as carmine lake, garanza lake and brazilwood overcoming their fluorescence and weak Raman scattering drawbacks. UV–visible absorption spectroscopy measurements were not able to discriminate among the different chromophores usually referred as carmine lake (carminic, kermesic and laccaic acid), as brazilwood (brazilin and brazilein) and as garanza lake (alizarin and purpurin). SERS measurements showed that the analyzed samples are composed of a mixture of different chromophores: brazilin and brazilein in brazilwood, kermesic and carminic acid in carmine lake, alizarin and purpurin in garanza lake. Detection at concentration level as low as 10{sup −7} M in aqueous solutions was achieved. Higher Raman intensities were observed using the excitation line of 632.8 nm wavelength with respect to the 785 nm, probably due to a pre-resonant effect with the molecular electronic transitions of the dyes.

  12. Analysis of strain and stress in ceramic, polymer and metal matrix composites by Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Colomban, P. [LADIR, Nanophases and Heterogeneous Solids Group, UMR 7075 CNRS and Universite Pierre et Marie Curie, 2 rue Henry-Dunant, 94320 Thiais (France)

    2002-08-01

    Raman scattering is a unique tool providing information on the structure and short-range order of matter. Stress-induced Raman shifts can be used to determine the stress/strain in films, fibres, particulate composites and, more generally, in any phase a few microns or more in scale. Quantitative results follow from a wavenumber calibration as a function of tensile strains or pressures applied to reference fibres or crystals. Furthermore, if the material is coloured, (near) resonant Raman scattering occurs, which enhances the scattered light intensity and simplifies the spectra - especially for harmonics - but drastically reduces the analysed volume (in-depth penetration {proportional_to}10-100 nm). This paper discusses the effective and potential advantages/drawbacks of Raman micro-spectrometry technique. The procedures to improve the sensitivity, the legibility and the reliability will be addressed. Examples will be chosen among (aramid, C, SiC) fibre- reinforced ceramic (CMCs), polymer (PMCs) or metal matrix (MMCs) composites. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  13. In situ Raman mapping of art objects

    Science.gov (United States)

    Lauwers, D.; Brondeel, Ph.; Moens, L.; Vandenabeele, P.

    2016-12-01

    Raman spectroscopy has grown to be one of the techniques of interest for the investigation of art objects. The approach has several advantageous properties, and the non-destructive character of the technique allowed it to be used for in situ investigations. However, compared with laboratory approaches, it would be useful to take advantage of the small spectral footprint of the technique, and use Raman spectroscopy to study the spatial distribution of different compounds. In this work, an in situ Raman mapping system is developed to be able to relate chemical information with its spatial distribution. Challenges for the development are discussed, including the need for stable positioning and proper data treatment. To avoid focusing problems, nineteenth century porcelain cards are used to test the system. This work focuses mainly on the post-processing of the large dataset which consists of four steps: (i) importing the data into the software; (ii) visualization of the dataset; (iii) extraction of the variables; and (iv) creation of a Raman image. It is shown that despite the challenging task of the development of the full in situ Raman mapping system, the first steps are very promising. This article is part of the themed issue "Raman spectroscopy in art and archaeology".

  14. Investigation of L(+)-Ascorbic Acid with Raman Spectroscopy in Visible and UV Light

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    2015-01-01

    Abstract: Raman spectroscopy investigations of l(+)-ascorbic acid and its mono- and di-deprotonated anions (AH(-) and A(2-)) are reviewed and new measurements reported with several wavelengths, 229, 244, 266, 488, and 532nm. Results are interpreted, assisted by new DFT/B3LYP quantum chemical...... calculations with 6-311++G(d,p) basis sets for several conformations of ascorbic acid and the anions. Raman spectra were measured during titration with NaOH base in an oxygen-poor environment to avoid fluorescence when solutions were alkaline. The ultraviolet (UV) absorption band for ascorbic acid in aqueous...... solution at similar to 247nm was found to cause strong resonance enhancement for the ring C-C stretching mode (called B) at similar to 1692cm(-1). The ascorbate mono-anion absorbs at similar to 264.8nm giving Raman resonance enhancement for the same ring C-C bond stretching, downshifted to similar to 1591...

  15. Improving resolution in quantum subnanometre-gap tip-enhanced Raman nanoimaging.

    Science.gov (United States)

    Zhang, Yingchao; Voronine, Dmitri V; Qiu, Shangran; Sinyukov, Alexander M; Hamilton, Mary; Liege, Zachary; Sokolov, Alexei V; Zhang, Zhenrong; Scully, Marlan O

    2016-05-25

    Two-dimensional (2D) materials beyond graphene such as transition metal dichalcogenides (TMDs) have unique mechanical, optical and electronic properties with promising applications in flexible devices, catalysis and sensing. Optical imaging of TMDs using photoluminescence and Raman spectroscopy can reveal the effects of structure, strain, doping, edge states, and surface functionalization from materials to bioscience. However, Raman signals are inherently weak and so far have been limited in spatial resolution in TMDs to a few hundred nanometres which is much larger than the intrinsic scale of these effects. Here we overcome the diffraction limit by using resonant tip-enhanced Raman scattering (TERS) of few-layer MoS2, and obtain nanoscale optical images with ~20 nm spatial resolution. This becomes possible due to electric field enhancement in an optimized subnanometre-gap resonant tip-substrate configuration. We investigate the limits of signal enhancement by varying the tip-sample gap with sub-Angstrom precision and observe a quantum quenching behavior, as well as a Schottky-Ohmic transition, for subnanometre gaps, which enable surface mapping based on this new contrast mechanism. This quantum regime of plasmonic gap-mode enhancement with a few nanometre thick MoS2 junction may be used for designing new quantum optoelectronic devices and sensors with a wide range of applications.

  16. The effect of aqueous solution in Raman spectroscopy

    Science.gov (United States)

    Kang, Jian; Yuan, Xiaojuan; Dong, Xiao; Gu, Huaimin

    2009-08-01

    In Raman detection, the most popular solution for the samples is tri-distilled water. But the effect of aqueous solution is barely studied in Raman spectroscopy. In fact Raman spectroscopy of solid-state and liquid-state are obvious different. In addition, FWHM of Raman spectral peaks also change evidently. In this paper, several samples were selected for the experiment; including sodium nitrate, sodium nitrite, glucose and caffeine. By comparing the Raman spectroscopy of samples at different concentrations, it is found that the concentration of the sample can affect the strength of Raman spectroscopy, but it can hardly impact FWHM of Raman spectral peaks. By comparing the Raman spectroscopy of liquid-state with the Raman spectroscopy of solid-state, it is observed that the FWHM of some Raman spectral peaks varied obviously; that may be because when the sample was dissolved into the water, the crystal lattice structure was broken, and for some samples atom form became ion form in aqueous solution. Those structural variations caused the variation of the FWHM. The Raman spectroscopy of caffeine aqueous solution at very low concentration was also detected and analyzed. Compared with the Raman spectra of solid-state samples, it is found that some Raman spectral peaks disappeared when the sample was dissolved in water. It is possible that the low concentration of the sample result in the weakening of Raman signals and the disappearing of some weak Raman spectral peaks. Then Ag nanoparticles were added into the caffeine aqueous solution, the results suggest that surface enhanced Raman spectroscopy (SERS) not only can enhance the Raman spectral signal, but also can reduce the effect of aqueous solution. It is concluded that the concentration of sample only affects the strength of Raman spectroscopy; the aqueous solution can affect the FWHM of Raman spectral peaks; and SERS can reduce the effect of aqueous solution.

  17. Raman study of N bonding in AlGaAs/InGaAsN multiquantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Lazic, S.; Calleja, J.M. [Dept. Fisica de Materiales, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Hey, R.; Ploog, K. [Paul-Drude Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2006-06-15

    We report resonant Raman scattering measurements on InGaAsN/AlGaAs multiquantum wells grown by plasma-assisted molecular beam epitaxy. Sharp vibration modes have been observed at 323, 402, 454 and 501 cm{sup -1}. They are resonant in the energy range 1.81-1.87 eV at decreasing energies for increasing N concentration. The resonance energies reveal the influence of the N concentration on the barrier gap at the multiquantum well interfaces. The peaks are interpreted in terms of local vibrations involving GaN and AlN units and pairs. They seem to form mostly at the quantum well interfaces due to preferential N bonding to Al. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Human cardiac troponin I sensor based on silver nanoparticle doped microsphere resonator

    Science.gov (United States)

    Saliminasab, Maryam; Bahrampour, Alireza; Zandi, Mohammad Hossein

    2012-12-01

    Human cardiac troponin I (cTnI) is a specific biomarker for diagnosis of acute myocardial infarction (AMI). In this paper, a composite sensing system of an optical microsphere resonator and silver nanoparticles based on surface enhanced Raman scattering (SERS) and stimulated Raman scattering (SRS) techniques towards a point of care diagnostic system for AMI using the cTnI biomarker in HEPES buffered solution (HBS) is proposed. Pump and Raman signals enter the optical fiber coupling into the microsphere, and then SRS occurs in the microsphere. The presence of silver nanoparticles on the microsphere surface provides a tremendous enhancement of the resulting Raman signal through an electromagnetic enhancement of both the laser excitation and Stokes-shifted light of the order of 1010. This enhancement occurs in metals as surface plasmon resonance (SPR), which increases the Raman gain through the SERS effect. Our simulation results show that this sensor presents a linear response for cTnI detection. The calculated enhanced Raman signal can be employed to detect the cTnI molecules around the microsphere.

  19. Surface-enhanced Raman nanodomes

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Charles J; Xu Zhida; Wu, Hsin-Yu; Liu, Gang Logan; Cunningham, Brian T, E-mail: bcunning@illinois.edu [Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801 (United States)

    2010-10-15

    We demonstrate a surface-enhanced Raman scattering (SERS) substrate consisting of a closely spaced metal nanodome array fabricated on flexible plastic film. We used a low-cost, large-area replica molding process to produce a two-dimensional periodic array of cylinders that is subsequently overcoated with SiO{sub 2} and silver thin films to form dome-shaped structures. Finite element modeling was used to investigate the electromagnetic field distribution of the nanodome array structure and the effect of the nanodome separation distance on the electromagnetic field enhancement. The SERS enhancement from the nanodome array substrates was experimentally verified using rhodamine 6G as the analyte. With a separation distance of 17 nm achieved between adjacent domes using a process that is precisely controlled during thin film deposition, a reproducible SERS enhancement factor of 1.37 x 10{sup 8} was demonstrated. The nanoreplica molding process presented in this work allows for simple, low-cost, high-throughput fabrication of uniform nanoscale SERS substrates over large surface areas without the requirement for high resolution lithography or defect-free deposition of spherical microparticle monolayer templates.

  20. Spatially offset Raman spectroscopy based on a line-scan hyperspectral Raman system

    Science.gov (United States)

    Spatially offset Raman spectroscopy (SORS) is a technique that can obtain subsurface layered information by collecting Raman spectra from a series of surface positions laterally offset from the excitation laser. The current methods of SORS measurement are typically either slow due to mechanical move...

  1. Laser Raman Spectroscopy with Different Excitation Sources and Extension to Surface Enhanced Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    Md. Wahadoszamen

    2015-01-01

    Full Text Available A dispersive Raman spectrometer was used with three different excitation sources (Argon-ion, He-Ne, and Diode lasers operating at 514.5 nm, 633 nm, and 782 nm, resp.. The system was employed to a variety of Raman active compounds. Many of the compounds exhibit very strong fluorescence while being excited with a laser emitting at UV-VIS region, hereby imposing severe limitation to the detection efficiency of the particular Raman system. The Raman system with variable excitation laser sources provided us with a desired flexibility toward the suppression of unwanted fluorescence signal. With this Raman system, we could detect and specify the different vibrational modes of various hazardous organic compounds and some typical dyes (both fluorescent and nonfluorescent. We then compared those results with the ones reported in literature and found the deviation within the range of ±2 cm−1, which indicates reasonable accuracy and usability of the Raman system. Then, the surface enhancement technique of Raman spectrum was employed to the present system. To this end, we used chemically prepared colloidal suspension of silver nanoparticles as substrate and Rhodamine 6G as probe. We could observe significant enhancement of Raman signal from Rhodamine 6G using the colloidal solution of silver nanoparticles the average magnitude of which is estimated to be 103.

  2. [Raman spectra of monkey cerebral cortex tissue].

    Science.gov (United States)

    Zhu, Ji-chun; Guo, Jian-yu; Cai, Wei-ying; Wang, Zu-geng; Sun, Zhen-rong

    2010-01-01

    Monkey cerebral cortex, an important part in the brain to control action and thought activities, is mainly composed of grey matter and nerve cell. In the present paper, the in situ Raman spectra of the cerebral cortex of the birth, teenage and aged monkeys were achieved for the first time. The results show that the Raman spectra for the different age monkey cerebral cortex exhibit most obvious changes in the regions of 1000-1400 and 2800-3000 cm(-1). With monkey growing up, the relative intensities of the Raman bands at 1313 and 2885 cm(-1) mainly assigned to CH2 chain vibrational mode of lipid become stronger and stronger whereas the relative intensities of the Raman bands at 1338 and 2932 cm(-1) mainly assigned to CH3 chain vibrational mode of protein become weaker and weaker. In addition, the two new Raman bands at 1296 and 2850 cm(-1) are only observed in the aged monkey cerebral cortex, therefore, the two bands can be considered as a character or "marker" to differentiate the caducity degree with monkey growth In order to further explore the changes, the relative intensity ratios of the Raman band at 1313 cm(-1) to that at 1338 cm(-1) and the Raman band at 2885 cm(-1) to that at 2 932 cm(-1), I1313/I1338 and I2885/I2932, which are the lipid-to-protein ratios, are introduced to denote the degree of the lipid content. The results show that the relative intensity ratios increase significantly with monkey growth, namely, the lipid content in the cerebral cortex increases greatly with monkey growth. So, the authors can deduce that the overmuch lipid is an important cause to induce the caducity. Therefore, the results will be a powerful assistance and valuable parameter to study the order of life growth and diagnose diseases.

  3. Vibrational dynamics (IR, Raman, NRVS) and DFT study of new antitumor tetranuclearstannoxanecluster, Sn(IV)$-$oxo$-${di$-$o$-$vanillin} dimethyl dichloride

    Energy Technology Data Exchange (ETDEWEB)

    Arjmand, F. [Aligarh Muslim Univ., Aligarh (India). Dept. of Chemistry; Sharma, S. [Aligarh Muslim Univ., Aligarh (India). Dept. of Chemistry; Usman, M. [Aligarh Muslim Univ., Aligarh (India). Dept. of Chemistry; Leu, B. M. [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Hu, M. Y. [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Toupet, L. [Univ. de Rennes, Rennes (France). Inst. de Physique de Rennes; Gosztola, David J. [Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials; Tabassum, S. [Aligarh Muslim Univ., Aligarh (India). Dept. of Chemistry

    2016-06-21

    The vibrational dynamics of a newly synthesized tetrastannoxane was characterized with a combination of experimental (Raman, IR and tin-based nuclear resonance vibrational spectroscopy) and computational (DFT/B3LYP) methods, with an emphasis on the vibrations of the tin sites. The cytotoxic activity revealed a significant regression selectively against the human pancreatic cell lines.

  4. Time-resolved broadband Raman spectroscopies; A unified six-wave-mixing representation

    CERN Document Server

    Dorfman, Konstantin E; Mukamel, Shaul

    2013-01-01

    Excited-state vibrational dynamics in molecules can be studied by an electronically off-resonant Raman process induced by a probe pulse with variable delay with respect to an actinic pulse. We establish the connection between several variants of the technique that involve either spontaneous or stimulated Raman detection and different pulse configurations. By using loop diagrams in the frequency domain we show that all signals can be described as six wave mixing which depend on the same four point molecular correlation functions involving two transition dipoles and two polarizabilities and accompanied by a different gating. Simulations for the stochastic two-state-jump model illustrate the origin of the absorptive and dispersive features observed experimentally.

  5. Immunoassay utilizing biochemistry reaction product via surface-enhanced Raman scattering in near field

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Haiying; NI; Yi; JIANG; Wei; LUO; Peiqing; HUANG; Mei

    2005-01-01

    We propose here a kind of applications of surface-enhanced Raman scattering (SERS) to immunology. It is a new enzyme immunoassay based on SERS. In the proposed system, antibody immobilized on a solid substrate reacts with antigen, which binds with another antibody labeled with peroxidase. If this immunocomplex is subjected to reaction with o-phenylenediamine and hydrogenperoxide, azoaniline is generated. This azo compound is adsorbed on a silver colloid and only the azo compound gives a strong surface-enhanced resonance Raman (SERRS) spectrum. A linear relationship was observed between the peak intensity of the N=N stretching band and the concentration of antigen, revealing that one can determine the concentration of antigen by the SERRS measurement of the reaction product. The detection limit of this SERS enzyme immunoassay method was found to be about 10-15 mol/L.

  6. Spin-orbit-induced resonances and threshold anomalies in a reduced dimension Fermi gas

    CERN Document Server

    Wang, Su-Ju

    2016-01-01

    We calculate the reflection and transmission probabilities in a one-dimensional Fermi gas with an equal mixing of the Rashba and Dresselhaus spin-orbit coupling (RD-SOC) produced by an external Raman laser field. These probabilities are computed over multiple relevant energy ranges within the pseudo-potential approximation. Strong scattering resonances are found whenever the incident energy approaches either a scattering threshold or a quasi-bound state attached to one of the energetically closed higher dispersion branches. A striking difference is demonstrated between two very different regimes set by the Raman laser intensity, namely between scattering for the single- minimum dispersion versus the double-minimum dispersion at the lowest threshold. The presence of RD-SOC together with the Raman field fundamentally changes the scattering behavior and enables the realization of very different one-dimensional theoretical models in a single experimental setup when combined with a confinement-induced resonance.

  7. Plasmonic nano-protrusions: hierarchical nanostructures for single-molecule Raman spectroscopy

    Science.gov (United States)

    Basuray, Sagnik; Pathak, Avinash; Bok, Sangho; Chen, Biyan; Hamm, Steven C.; Mathai, Cherian J.; Guha, Suchismita; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

    2017-01-01

    Classical methods for enhancing the electromagnetic field from substrates for spectroscopic applications, such as surface-enhanced Raman spectroscopy (SERS), have involved the generation of hotspots through directed self-assembly of nanoparticles or by patterning nanoscale features using expensive nanolithography techniques. A novel large-area, cost-effective soft lithographic technique involving glancing angle deposition (GLAD) of silver on polymer gratings is reported here. This method produces hierarchical nanostructures with high enhancement factors capable of analyzing single-molecule SERS. The uniform ordered and patterned nanostructures provide extraordinary field enhancements that serve as excitatory hotspots and are herein interrogated by SERS. The high spatial homogeneity of the Raman signal and signal enhancement over a large area from a self-assembled monolayer (SAM) of 2-naphthalenethiol demonstrated the uniformity of the hotspots. The enhancement was shown to have a critical dependence on the underlying nanostructure via the surface energy landscape and GLAD angles for a fixed deposition thickness, as evidenced by atomic force microscopy and scanning electron microscopy surface analysis of the substrate. The nanostructured surface leads to an extremely concentrated electromagnetic field at sharp nanoscale peaks, here referred to as ‘nano-protrusions’, due to the coupling of surface plasmon resonance (SPR) with localized SPR. These nano-protrusions act as hotspots which provide Raman enhancement factors as high as 108 over a comparable SAM on silver. Comparison of our substrate with the commercial substrate Klarite™ shows higher signal enhancement and minimal signal variation with hotspot spatial distribution. By using the proper plasmon resonance angle corresponding to the laser source wavelength, further enhancement in signal intensity can be achieved. Single-molecule Raman spectra for rhodamine 6G are obtained from the best SERS substrate (a

  8. Backward Raman Amplifier for Laser Wakefield Accelerator

    Science.gov (United States)

    Ludwig, Joshua; Masson-Laborde, Paul-Edouard; Huller, Stefan; Rozmus, Wojciech; Wilks, Scott C.

    2016-10-01

    Particle in cell simulations via SCPIC and theoretical work on Raman amplification and laser wake field acceleration will be presented. Laser energy depletion has been shown to be a limiting factor during wake field acceleration. This work focuses on optimizing parameters for Raman amplification to work in conjunction with wake field acceleration in order in order to sustain an accelerating laser pulse as it generates plasma waves. It has been shown that laser pulses undergo red shifting during wake generation. Our work demonstrates that this red shifting results in a detuning between pump and seed in the backward Raman Amplifier. This detuning limits the amount of energy that can be transferred from the pump to the seed, and places new limits on backward Raman amplification. To overcome this limiting factor, this study makes use of a chirped pump allowing for extended coupling to the accelerating pulse. Three wave coupling model of Raman amplifier with a frequency shift term due to wake field will also be discussed and compared with PIC simulations.

  9. Raman spectroscopy of selected carbonaceous samples

    Energy Technology Data Exchange (ETDEWEB)

    Kwiecinska, Barbara [University of Science and Technology-AGH, Faculty of Geology, Geophysics and Environmental Protection, Krakow (Poland); Suarez-Ruiz, Isabel [Instituto Nacional del Carbon, (INCAR-CSIC), Oviedo (Spain); Paluszkiewicz, Czeslawa [University of Science and Technology-AGH, Faculty of Materials Science and Technology, Krakow (Poland); Rodriques, Sandra [Universidade do Porto, Faculdade de Ciencias, Dept. de Geologia (Portugal)

    2010-12-01

    This paper presents the results of Raman spectra measured on carbonaceous materials ranging from greenschist facies to granulite-facies graphite (Anchimetamorphism and Epimetamorphism zones). Raman spectroscopy has come to be regarded as a more appropriate tool than X-ray diffraction for study of highly ordered carbon materials, including chondritic matter, soot, polycyclic aromatic hydrocarbons and evolved coal samples. This work demonstrates the usefulness of the Raman spectroscopy analysis in determining internal crystallographic structure (disordered lattice, heterogeneity). Moreover, this methodology permits the detection of differences within the meta-anthracite rank, semi-graphite and graphite stages for the samples included in this study. In the first order Raman spectra, the bands located near to c.a. 1350 cm{sup -1} (defects and disorder mode A{sub 1g}) and 1580 cm{sup -1} (in plane E{sub 2g} zone - centre mode) contribute to the characterization and determination of the degree of structural evolution and graphitization of the carbonaceous samples. The data from Raman spectroscopy were compared with parameters obtained by means of structural, chemical and optical microscopic analysis carried out on the same carbonaceous samples. The results revealed some positive and significant relationships, although the use of reflectance as a parameter for following the increase in structural order in natural graphitized samples was subject to limitations. (author)

  10. Studies on structure and Raman spectroscopy of Ni-doped copper phthalocyanine thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, XueYan, E-mail: wxyadeline@163.com; Zheng, JianBang; Qiao, Kai; Qu, JunRong; Cao, ChongDe

    2014-04-01

    Highlights: • CuPc films with and without Ni-doping were prepared in high vacuum chamber. • The morphology, crystallinity, crystallite dimension and optical properties of these mixed films changed gradually with the increase of proportion of Ni-doping, but CuPc still kept their original α-phase crystal. • Raman intensities of all the vibration modes in RRS are not enhanced in the same way but are enhanced selectively. • The amorphous nickel atoms clusters had a noticeable light absorption and reflectivity loss. - Abstract: Ni-doped copper phthalocyanine (CuPc) organic films with different mixing ratios were prepared in high vacuum (HV) chamber. The results of AFM, XRD, UV–vis and Raman spectroscopy indicated that the surface morphologies of the films were found to be flater and the structures of the CuPc films still kept their original α-phase crystal, with only the crystallinity or crystallite sizes being changed and the versatile structure or charge transport being modified with the increase of Ni-doping ratios. Moreover, 514 nm-visible-light-excited normal Raman spectra (NRS), 325 nm-ultraviolet-excited and 633 nm-excited resonance Raman spectra (RRS) were analyzed by comparison and by density functional theory (DFT) calculations of the amorphous nickel atoms clusters, confirming that there were no chemical changes between CuPc molecules and nickel atoms; and the amorphous nickel atoms clusters had a noticeable light absorption loss, offering us an insightful structural understanding of the Raman effect of the different concentrations of Ni-doped CuPc films.

  11. Gold nanorods combine photoacoustic and Raman imaging for detection and treatment of ovarian cancer

    Science.gov (United States)

    Jokerst, Jesse V.; Cole, Adam J.; Bohndiek, Sarah E.; Gambhir, Sanjiv S.

    2014-03-01

    Gold nanorods (GNRs) were synthesized with surfactant templating and coated with IR792 to produce surface-enhanced Raman signal (SERS). Subcutaneous and orthotopic tumor models were created in nude mice using the OV2008 cell line, and a Nexus128 scanner from Endra LifeSciences was used to collect the photoacoustic data. We used GNRs with resonance at 756 nm, and the Raman signal was 10-fold larger than 60 nm gold core/silica shell nanoparticles. This signal was stable for over 24 hours in 50% serum. The batch-to-batch reproducibility was 15.5% and 3.6% in the SERS and photoacoustic modalities for n=4 batches. Animals were injected with 200 μL of 2.5, 5.4, and 16.8 nM GNRs. Relative to baseline photoacoustic signal, these concentrations increased tumor signal 1.3-, 1.6-, and 2.5-fold, respectively. The maximum signal increase occurred within 2 hours of injection persisted for at least 24 hours and was significant at p0.90) between tumor gold concentration and photoacoustic signal. By 24 hours, free GNRs had been sequestered to the liver and spleen with 2%ID/g immobilized in the tumor. The same GNRs produced SERS signal, and Raman maps were created with least squares analysis. We used the Raman signal to identify tumor margins and also to monitor resection and ensure complete removal of tumor tissue. Thus, the GNRs allow pre-surgical photoacoustic visualization for tumor staging and intra-operative Raman imaging to guide resection. Future work will study GNRs targeted to cell surface proteins to increase tumor accumulation.

  12. Resonance and Neck Length for a Spherical Resonator

    Directory of Open Access Journals (Sweden)

    Emily Corning

    2011-06-01

    Full Text Available The relationship between the neck length of a spherical resonator and its period of fundamental resonance was investigated. This was done by measuring the frequency of fundamental resonance of the resonator at 6 different neck lengths. It was found that its resonance resembled Helmholtz resonance but was not that of ideal Helmholtz resonance.

  13. Profiling the Near field of Nanoshells Using Surface Enhanced Raman Spectroscopy

    Science.gov (United States)

    Lal, Surbhi

    2005-03-01

    There is tremendous interest in the enhancement of electromagnetic fields near metal surfaces. The spatial extent of the near field as a function of distance from the metal surface is of particular interest for applications such as surface enhanced Raman spectroscopy. By using specially designed molecular scaffolds with Raman-active constituents, we measure the profile of this fringing field at a nanoshell surface. Nanoshells are colloidal particles composed of a silica core covered by a gold shell, which exhibit a tunable plasmon resonance; close to this resonance there is a strong enhancement of the electromagnetic near field. The molecular scaffolds consist of polyadenine DNA strands as tethers with a terminal fluorescein molecule. By varying the length of the DNA strand, the fluorescein molecule is placed at controlled distances from the nanoshell surface. Both the DNA scaffold and the terminal fluorescein molecule provide us with independent SERS Stokes modes whose relative intensities permit us to map the average spatial decay length of the near field of the nanoparticle at its plasmon resonance.

  14. Drug stability analysis by Raman spectroscopy.

    Science.gov (United States)

    Shende, Chetan; Smith, Wayne; Brouillette, Carl; Farquharson, Stuart

    2014-12-22

    Pharmaceutical drugs are available to astronauts to help them overcome the deleterious effects of weightlessness, sickness and injuries. Unfortunately, recent studies have shown that some of the drugs currently used may degrade more rapidly in space, losing their potency before their expiration dates. To complicate matters, the degradation products of some drugs can be toxic. Here, we present a preliminary investigation of the ability of Raman spectroscopy to quantify mixtures of four drugs; acetaminophen, azithromycin, epinephrine, and lidocaine, with their primary degradation products. The Raman spectra for the mixtures were replicated by adding the pure spectra of the drug and its degradant to determine the relative percent contributions using classical least squares. This multivariate approach allowed determining concentrations in ~10 min with a limit of detection of ~4% of the degradant. These results suggest that a Raman analyzer could be used to assess drug potency, nondestructively, at the time of use to ensure crewmember safety.

  15. Drug Stability Analysis by Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    Chetan Shende

    2014-12-01

    Full Text Available Pharmaceutical drugs are available to astronauts to help them overcome the deleterious effects of weightlessness, sickness and injuries. Unfortunately, recent studies have shown that some of the drugs currently used may degrade more rapidly in space, losing their potency before their expiration dates. To complicate matters, the degradation products of some drugs can be toxic. Here, we present a preliminary investigation of the ability of Raman spectroscopy to quantify mixtures of four drugs; acetaminophen, azithromycin, epinephrine, and lidocaine, with their primary degradation products. The Raman spectra for the mixtures were replicated by adding the pure spectra of the drug and its degradant to determine the relative percent contributions using classical least squares. This multivariate approach allowed determining concentrations in ~10 min with a limit of detection of ~4% of the degradant. These results suggest that a Raman analyzer could be used to assess drug potency, nondestructively, at the time of use to ensure crewmember safety.

  16. Subsurface Raman analysis of thin painted layers.

    Science.gov (United States)

    Conti, Claudia; Colombo, Chiara; Realini, Marco; Zerbi, Giuseppe; Matousek, Pavel

    2014-01-01

    Here we present, for the first time, an extension of spatially offset Raman spectroscopy to thin (tens of micrometers thick), highly turbid stratified media such as those encountered in paintings. The method permits the non-destructive interrogation of painted layers in situations where conventional Raman microscopy is not applicable due to high turbidity of the top layer(s). The concept is demonstrated by recovering the pure Raman spectra of paint sub-layers that are completely obscured by paint over-layers. Potential application areas include the analysis of paintings in art preservation and restoration avoiding the cross-sectional analysis used currently with this type of samples. The technique also holds promise for the development as a non-destructive subsurface tool for in situ analysis using portable instruments.

  17. Characterization of Kevlar Using Raman Spectroscopy

    Science.gov (United States)

    Washer, Glenn; Brooks, Thomas; Saulsberry, Regor

    2007-01-01

    This paper explores the characterization of Kevlar composite materials using Raman spectroscopy. The goal of the research is to develop and understand the Raman spectrum of Kevlar materials to provide a foundation for the development of nondestructive evaluation (NDE) technologies based on the interaction of laser light with the polymer Kevlar. The paper discusses the fundamental aspects of experimental characterization of the spectrum of Kevlar, including the effects of incident wavelength, polarization and laser power. The effects of environmental exposure of Kevlar materials on certain characteristics of its Raman spectrum are explored, as well as the effects of applied stress. This data may provide a foundation for the development of NDE technologies intended to detect the in-situ deterioration of Kevlar materials used for engineering applications that can later be extended to other materials such as carbon fiber composites.

  18. Raman spectroscopy of hydrogen molecules in germanium

    Energy Technology Data Exchange (ETDEWEB)

    Hiller, M. [Technische Universitaet Dresden, 01062 Dresden (Germany)]. E-mail: martin.hiller@physik.phy.tu-dresden.de; Lavrov, E.V. [Technische Universitaet Dresden, 01062 Dresden (Germany); Weber, J. [Technische Universitaet Dresden, 01062 Dresden (Germany)

    2006-04-01

    Single-crystalline germanium samples exposed to hydrogen and/or deuterium plasma are studied by Raman scattering. Two bands at 1980 and 4155cm{sup -1} are assigned to local vibrational modes of Ge-H and H{sub 2}, respectively. Polarization sensitive Raman scattering spectra suggest that the plasma treatment results in {l_brace}111{r_brace} platelets whose basic units are Ge-H bonds. The signal at 4155cm{sup -1} is shown to result from molecular hydrogen trapped within these platelets. Another broad Raman signal around 3930cm{sup -1} seems to be due to H{sub 2} trapped in some other type of voids formed during the plasma treatment. Two sharp peaks at 3826 and 3834cm{sup -1} are assigned to ortho- and para-H{sub 2} trapped at the interstitial T site.

  19. Integral resonator gyroscope

    Science.gov (United States)

    Shcheglov, Kirill V. (Inventor); Challoner, A. Dorian (Inventor); Hayworth, Ken J. (Inventor); Wiberg, Dean V. (Inventor); Yee, Karl Y. (Inventor)

    2008-01-01

    The present invention discloses an inertial sensor having an integral resonator. A typical sensor comprises a planar mechanical resonator for sensing motion of the inertial sensor and a case for housing the resonator. The resonator and a wall of the case are defined through an etching process. A typical method of producing the resonator includes etching a baseplate, bonding a wafer to the etched baseplate, through etching the wafer to form a planar mechanical resonator and the wall of the case and bonding an end cap wafer to the wall to complete the case.

  20. The Raman spectrum of monetite, CaHPO 4

    Science.gov (United States)

    Casciani, F.; Condrate, R. A.

    1980-10-01

    The Raman spectrum was measured for monetite, CaHPO 4. A consistent set of band assignments were made for both the Raman and infrared spectra. The effects of factor group and two-site effect are discussed.