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Sample records for raman spectra cyclohexanone

  1. Cyclohexanone

    Integrated Risk Information System (IRIS)

    Cyclohexanone ; CASRN 108 - 94 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Eff

  2. Spectroscopic (infrared, Raman, UV and NMR) analysis, Gaussian hybrid computational investigation (MEP maps/HOMO and LUMO) on cyclohexanone oxime

    NASA Astrophysics Data System (ADS)

    Ramalingam, S.; Karabacak, M.; Periandy, S.; Puviarasan, N.; Tanuja, D.

    2012-10-01

    In the present analysis, FT-IR/FT-Raman spectra of the cyclohexanone oxime (CHO, C6H11NO) are recorded. The observed vibrational frequencies are assigned and the computational calculations are carried out by HF and DFT (B3LYP and B3PW91) methods with 6-311++G(d,p) basis set and the corresponding results are tabulated. In order to yield good coherence with observed values, the calculated frequencies are scaled by appropriate scale factors. The complete assignments are performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The alternation of structure of cyclohexanone due to the substitution of NOH is investigated. The vibrational sequence pattern of the molecule related to the substitutions is analyzed. Comparison of the observed fundamental vibrational frequencies of CHO and calculated results by density functional (B3LYP and B3PW91) and HF methods indicates that B3LYP is superior to the scaled HF and B3PW91 approach for molecular vibrational problems. Moreover, 13C NMR and 1H NMR chemical shifts are calculated by using the gauge independent atomic orbital (GIAO) method with HF/B3LYP/B3PW91 methods and the same basis set. A study on the electronic properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, are performed by HF and DFT methods. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. NLO properties and Mulliken charges of the CHO was also calculated and interpreted. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures are calculated in gas phase.

  3. Spectroscopic (infrared, Raman, UV and NMR) analysis, Gaussian hybrid computational investigation (MEP maps/HOMO and LUMO) on cyclohexanone oxime.

    PubMed

    Ramalingam, S; Karabacak, M; Periandy, S; Puviarasan, N; Tanuja, D

    2012-10-01

    In the present analysis, FT-IR/FT-Raman spectra of the cyclohexanone oxime (CHO, C(6)H(11)NO) are recorded. The observed vibrational frequencies are assigned and the computational calculations are carried out by HF and DFT (B3LYP and B3PW91) methods with 6-311++G(d,p) basis set and the corresponding results are tabulated. In order to yield good coherence with observed values, the calculated frequencies are scaled by appropriate scale factors. The complete assignments are performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The alternation of structure of cyclohexanone due to the substitution of NOH is investigated. The vibrational sequence pattern of the molecule related to the substitutions is analyzed. Comparison of the observed fundamental vibrational frequencies of CHO and calculated results by density functional (B3LYP and B3PW91) and HF methods indicates that B3LYP is superior to the scaled HF and B3PW91 approach for molecular vibrational problems. Moreover, (13)C NMR and (1)H NMR chemical shifts are calculated by using the gauge independent atomic orbital (GIAO) method with HF/B3LYP/B3PW91 methods and the same basis set. A study on the electronic properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, are performed by HF and DFT methods. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. NLO properties and Mulliken charges of the CHO was also calculated and interpreted. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures are calculated in gas phase.

  4. Raman spectra of lignin model compounds

    Treesearch

    Umesh P. Agarwal; Richard S. Reiner; Ashok K. Pandey; Sally A. Ralph; Kolby C. Hirth; Rajai H. Atalla

    2005-01-01

    To fully exploit the value of Raman spectroscopy for analyzing lignins and lignin containing materials, a detailed understanding of lignins’ Raman spectra needs to be achieved. Although advances made thus far have led to significant growth in application of Raman techniques, further developments are needed to improve upon the existing knowledge. Considering that lignin...

  5. Investigation of Raman spectra of polyethylene terephthalate

    NASA Astrophysics Data System (ADS)

    Zhu, Changjun; Tong, Na; Song, Lixin; Zhang, Guoqing

    2015-08-01

    Raman spectrometry was employed to study the characteristics of Raman spectra of polyethylene terephthalate (PET), which were treated with sodium hydroxide, sulfuric acid and copper sulfate, respectively. Raman spectra under different conditions were obtained and the characteristics of the Raman spectra were analyzed. The morphology structures were observed under different conditions using Atomic Force Microscope. The results show that the spectral intensity of PET treated with sodium hydroxide is higher than that untreated between 200-1750 cm-1, while the intensity of PET treated with sodium hydroxide is lower than that untreated beyond 1750 cm-1 and the fluorescence background of Raman spectra is decreased. The spectral intensity of PET treated with sulfuric acid is remarkably reduced than that untreated, and the intensity of PET treated with copper sulphate is much higher than that untreated.

  6. NBO analysis and vibrational spectra of 2,6-bis(p-methyl benzylidene cyclohexanone) using density functional theory

    NASA Astrophysics Data System (ADS)

    Padmaja, L.; Amalanathan, M.; Ravikumar, C.; Hubert Joe, I.

    2009-10-01

    Vibrational analysis of the 2,6-bis(p-methyl benzylidene cyclohexanone) [PMBC] compound was carried out by using NIR FT-Raman and FT-IR spectroscopic techniques. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of PMBC have been investigated with the help of B3LYP/6-31G(d) density functional theory method. The optimized geometry clearly demonstrates cyclohexanone ring chair conformation is changed into half-chair conformation. The shortening of C-H bond length and blue shifting of the CH stretching wavenumber suggest the existence of improper weak C-H⋯O hydrogen bonding, which is confirmed by the natural bond orbital analysis. The Mulliken population analysis on atomic charges and the HOMO-LUMO energy are also calculated.

  7. Molecular structure and vibrational spectra of 2,6-bis(benzylidene)cyclohexanone: a density functional theoretical study.

    PubMed

    Sajan, D; Udaya Lakshmi, K; Erdogdu, Y; Joe, I Hubert

    2011-01-01

    The near-infrared Fourier transform (NIR-FT) Raman and Fourier transform infrared (FT-IR) spectral analyses of 2,6-bis(benzylidene)cyclohexanone (BBC) molecule, a potential drugs for the treatment of P388 leukemia cells, were carried out along with density functional computations. The optimized geometry of BBC using density functional theory shows that the energetically favored chair conformation is not observed for central cyclohexanone ring and is found to possess a nearly 'half chair' conformation and shows less expansion of the angles and more rotation about the bonds. The existence of intramolecular C-H⋯O improper, blue-shifted hydrogen bond was investigated by means of the NBO analysis. The lowering of carbonyl stretching vibration can be attributed to the mesomeric effect and the π-orbital conjugation induced by the unsaturation in the α-carbon atoms and co-planarity of the (-CH=C-(C=O)-C=CH-) group.

  8. NBO analysis and vibrational spectra of 2,6-bis(p-methyl benzylidene cyclohexanone) using density functional theory.

    PubMed

    Padmaja, L; Amalanathan, M; Ravikumar, C; Hubert Joe, I

    2009-10-01

    Vibrational analysis of the 2,6-bis(p-methyl benzylidene cyclohexanone) [PMBC] compound was carried out by using NIR FT-Raman and FT-IR spectroscopic techniques. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of PMBC have been investigated with the help of B3LYP/6-31 G(d) density functional theory method. The optimized geometry clearly demonstrates cyclohexanone ring chair conformation is changed into half-chair conformation. The shortening of C-H bond length and blue shifting of the CH stretching wavenumber suggest the existence of improper weak C-H***O hydrogen bonding, which is confirmed by the natural bond orbital analysis. The Mulliken population analysis on atomic charges and the HOMO-LUMO energy are also calculated.

  9. Micro-Raman spectra of ugrandite garnet.

    PubMed

    Moroz, T; Ragozin, A; Salikhov, D; Belikova, G; Puchkov, V; Kagi, H

    2009-08-01

    The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X(3)Y(2)(SiO(4))(3), X = Ca(2+), Y = Al(3+), Fe(3+), Cr(3+), according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported.

  10. Micro-Raman spectra of ugrandite garnet

    NASA Astrophysics Data System (ADS)

    Moroz, T.; Ragozin, A.; Salikhov, D.; Belikova, G.; Puchkov, V.; Kagi, H.

    2009-08-01

    The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X 3Y 2(SiO 4) 3, X = Ca 2+, Y = Al 3+, Fe 3+, Cr 3+, according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported.

  11. Raman spectra of benzophenone and benzopinacol crystals

    NASA Astrophysics Data System (ADS)

    Davydova, N. A.; Babkov, L. M.; Baran, J.; Kukielski, J. I.; Mel'nik, V. I.; Truchkachev, S. V.

    2002-09-01

    For the first time Raman spectra of benzopinacol crystals, which are a result of photochemical decomposition of benzophenone crystals, have been measured over the range 10-3600 cm -1. A tentative model of benzopinacol molecule has been proposed to calculate Raman active modes. The comparison of the calculated frequencies with those experimentally observed shows good accordance. Thus, the proposed model of benzopinacol molecule apparently is quite adequate to the real structure.

  12. Molecular dynamics and spectra. II. Diatomic Raman

    NASA Astrophysics Data System (ADS)

    Berens, Peter H.; White, Steven R.; Wilson, Kent R.

    1981-07-01

    This paper and paper I in this series [P.H. Berens and K.R. Wilison, J. Chem. Phys. 74, 4872 (1981)] indicate that infrared and Raman rotational and fundamental vibrational-rotational spectra of dense systems (high pressure gases, liquids, and solids) are essentially classical, in that they can be computed and understood from a basically classical mechanical viewpoint, with some caveats for features in which anharmonicity is important, such as the detailed shape of Q branches. It is demonstrated here, using the diatomic case as an example, that ordinary, i.e., nonresonant, Raman band contours can be computed from classical mechanics plus simple quantum corrections. Classical versions of molecular dynamics, linear response theory, and ensemble averaging, followed by straightforward quantum corrections, are used to compute the pure rotational and fundamental vibration-rotational Raman band contours of N2 for the gas phase and for solutions of N2 in different densities of gas phase Ar and in liquid Ar. The evolution is seen from multiple peaked line shapes characteristic of free rotation in the gas phase to single peaks characteristic of hindered rotation in the liquid phase. Comparison is made with quantum and correspondence principle classical gas phase spectral calculations and with experimental measurements for pure N2 and N2 in liquid Ar. Three advantages are pointed out for a classical approach to infrared and Raman spectra. First, a classical approach can be used to compute the spectra of complex molecular systems, e.g., of large molecules, clusters, liquids, solutions, and solids. Second, this classical approach can be extended to compute the spectra of nonequilibrium and time-dependent systems, e.g., infrared and Raman spectra during the course of chemical reactions. Third, a classical viewpoint allows experimental infrared and Raman spectra to be understood and interpreted in terms of atomic motions with the considerable aid of classical models and of our

  13. ProRaman: a program to classify Raman spectra.

    PubMed

    de Paula, Alderico Rodrigues; Silveira, Landulfo; Pacheco, Marcos Tadeu Tavares

    2009-06-01

    The program ProRaman, developed for the Matlab platform, provides an interactive and flexible graphic interface to develop efficient algorithms to classify Raman spectra into two or three different classes. A set of preprocessing algorithms to decrease the variable dimensionality and to extract the main features which improve the correct classification ratio was implemented. The implemented classification algorithms were based on the Mahalanobis distance and neural network. To verify the functionality of the developed program, 72 spectra from human artery samples, 36 of which had been histopathologically diagnosed as non-diseased and 36 as having an atherosclerotic lesion, were processed using a combination of different preprocessing and classification techniques. The best result was accomplished when the variables were selected from the Raman spectrum shift range from 1200 to 1700 cm(-1), then preprocessed using wavelets for compression and principal component analysis for feature extraction and, finally, classified by a multilayer perceptron with one hidden layer with eight neurons.

  14. Molecular structure and vibrational spectra of 2,6-bis(benzylidene)cyclohexanone: A density functional theoretical study

    NASA Astrophysics Data System (ADS)

    Sajan, D.; Udaya Lakshmi, K.; Erdogdu, Y.; Hubert Joe, I.

    2011-01-01

    The near-infrared Fourier transform (NIR-FT) Raman and Fourier transform infrared (FT-IR) spectral analyses of 2,6-bis(benzylidene)cyclohexanone (BBC) molecule, a potential drugs for the treatment of P388 leukemia cells, were carried out along with density functional computations. The optimized geometry of BBC using density functional theory shows that the energetically favored chair conformation is not observed for central cyclohexanone ring and is found to possess a nearly 'half chair' conformation and shows less expansion of the angles and more rotation about the bonds. The existence of intramolecular C-H⋯O improper, blue-shifted hydrogen bond was investigated by means of the NBO analysis. The lowering of carbonyl stretching vibration can be attributed to the mesomeric effect and the π-orbital conjugation induced by the unsaturation in the α-carbon atoms and co-planarity of the (-CH dbnd C-(C dbnd O)-C dbnd CH-) group.

  15. Raman spectra of carotenoids in natural products

    NASA Astrophysics Data System (ADS)

    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.

  16. [Raman spectra of monkey cerebral cortex tissue].

    PubMed

    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.

  17. Raman spectra of deuteriated taurine single crystals

    NASA Astrophysics Data System (ADS)

    Souza, J. M. de; Lima, R. J. C.; Freire, P. T. C.; Sasaki, J. M.; Melo, F. E. A.; Filho, J. Mendes; Jones, Derry W.

    2005-05-01

    The polarized Raman spectra of partially deuteriated taurine [(ND 3+) 0.65(NH 3+) 0.35(CH 2) 2SO 3-] crystals from x( zz) x and x( zy) x scattering geometries of the A g and B g irreducible representations of the factor group C 2h are reported. The temperature-dependent Raman spectra of partially deuteriated taurine do not reveal any evidence of the structural phase transition undergone by normal taurine at about 250 K, but an anomaly observed in the 180 cm -1 band at ˜120 K implies a different dynamic for this band (which is involved in a pressure-induced phase transition) in the deuteriated crystal.

  18. Ab initio infrared and Raman spectra

    NASA Technical Reports Server (NTRS)

    Fredkin, D. R.; White, S. R.; Wilson, K. R.; Komornicki, A.

    1983-01-01

    It is pointed out that with increased computer power and improved computational techniques, such as the gradients developed in recent years, it is becoming practical to compute spectra ab initio, from the fundamental constants of nature, for systems of increasing complexity. The present investigation has the objective to explore several possible ab initio approaches to spectra, giving particular attention to infrared and nonresonance Raman. Two approaches are discussed. The sequential approach, in which first the electronic part and then later the nuclear part of the Born-Oppenheimer approximation is solved, is appropriate for small systems. The simultaneous approach, in which the electronic and nuclear parts are solved at the same time, is more appropriate for many-atom systems. A review of the newer quantum gradient techniques is provided, and the infrared and Raman spectral band contours for the water molecule are computed.

  19. Automatic Spike Removal Algorithm for Raman Spectra.

    PubMed

    Tian, Yao; Burch, Kenneth S

    2016-11-01

    Raman spectroscopy is a powerful technique, widely used in both academia and industry. In part, the technique's extensive use stems from its ability to uniquely identify and image various material parameters: composition, strain, temperature, lattice/excitation symmetry, and magnetism in bulk, nano, solid, and organic materials. However, in nanomaterials and samples with low thermal conductivity, these measurements require long acquisition times. On the other hand, charge-coupled device (CCD) detectors used in Raman microscopes are vulnerable to cosmic rays. As a result, many spurious spikes occur in the measured spectra, which can distort the result or require the spectra to be ignored. In this paper, we outline a new method that significantly improves upon existing algorithms for removing these spikes. Specifically, we employ wavelet transform and data clustering in a new spike-removal algorithm. This algorithm results in spike-free spectra with negligible spectral distortion. The reduced dependence on the selection of wavelets and intuitive wavelet coefficient adjustment strategy enables non-experts to employ these powerful spectra-filtering techniques.

  20. AB initio infrared and Raman spectra

    NASA Astrophysics Data System (ADS)

    Fredkin, D. R.; Komornicki, A.; White, S. R.; Wilson, K. R.

    1982-08-01

    We discuss several ways in which molecular absorption and scattering spectra can be computed ab initio, from the fundamental constants of nature. These methods can be divided into two general categories. In the first, or sequential, type of approach, one first solves the electronic part of the Schroedinger equation in the Born-Oppenheimer approximation, mapping out the potential energy, dipole moment vector (for infrared absorption) and polarizability tensor (for Raman scattering) as functions of nuclear coordinates. Having completed the electronic part of the calculation, one then solves the nuclear part of the problem either classically or quantum mechanically. As an example of the sequential ab initio approach, the infrared and Raman rotational and vibrational-rotational spectral band contours for the water molecule are computed in the simplest rigid rotor, normal mode approximation. Quantum techniques, are used to calculate the necessary potential energy, dipole moment, and polarizability information at the equilibrium geometry. A new quick, accurate, and easy to program classical technique involving no reference to Euler angles or special functions is developed to compute the infrared and Raman angles or special functions is developed to compute the infrared and Raman band contours for any rigid rotor, including asymmetric tops. A second, or simultaneous, type of ab initio approach is suggested for large systems, particularly those for which normal mode analysis is inappropriate, such as liquids, clusters, or floppy molecules.

  1. Multiconfigurational Effects in Theoretical Resonance Raman Spectra

    PubMed Central

    Ma, Yingjin

    2017-01-01

    Abstract We analyze resonance Raman spectra of the nucleobase uracil in the short‐time approximation calculated with multiconfigurational methods. We discuss the importance of static electron correlation by means of density‐matrix renormalization group self‐consistent field (DMRG‐SCF) calculations. Our DMRG‐SCF results reveal that a minimal active orbital space that leads to a qualitatively correct description of the resonance Raman spectrum of uracil should encompass parts of the σ/σ* bonding/anti‐bonding orbitals of the pyrimidine ring. We trace these findings back to the considerable entanglement between the σ/σ* bonding/anti‐bonding as well as valence π/π* orbitals in the excited‐state electronic structure of uracil, which indicates non‐negligible non‐dynamical correlation effects that are less pronounced in the electronic ground state. PMID:27933695

  2. [Study on Raman Spectra of Some Clinical Medicine].

    PubMed

    Dong, He; Liu, Chuan; Dai, Chang-Jian

    2016-01-01

    Aiming at the shortage of the Raman spectra of drugs and the current situation of drug testing, we have applied Raman spectroscopic technique to several kinds of medicine, such as antibiotics, antihistamine, hemocoagulase and antiemetics. The spectral properties for the samples with high Raman activity are investigated by observing their Raman spectra to yield the shift, intensity, and line width of the Raman peaks, as well as the line shape of Raman envelope. For those samples with weak Raman activity or complex structures that are hard to be identified, we have also made some tentative measurements or raise some suggestions for future measurement. Comparing the similarities or differences among many Raman spectra of drugs, it is evident that drugs with small molecule have apparent spectral characteristics, by which to recognize them is very feasible, while those with large molecule usually have weak peaks or complex envelope in their spectra, leading to a difficult recognition and uncertain peak positions. This work not only proposes to identify chemical ingredients of drugs by observing and analyzing their Raman spectra, but also provides experimental evidences for medical workers doing so. The present results lay the foundation for establish the database of Raman spectra for drugs, and point out the prospect for rapid identification and detection of drugs, promoting the application of Raman spectroscopy technology on drug detection to a certain extent.

  3. [Near infrared Raman spectra analysis of rhizoma dioscoreae].

    PubMed

    Lin, Wen-Shuo; Chen, Rong; Li, Yong-Zeng; Feng, Shang-Yuan; Huang, Zu-Fang; Xie, Bing-Xian

    2008-05-01

    A novel and compact near-infrared (NIR) Raman system was developed using 785 nm diode laser, volume-phase technology holographic system, and NIR intensified charge-coupled device (CCD). The Raman spectra and first derivative spectra of rhizoma dioscoreae were obtained. The Raman spectra of rhizoma dioscoreae showed three strong characteristic peaks at 477, 863 and 936 cm(-1), respectively. The major ingredients are protein, amino acid, starch, polysaccharides and so on, matching the known basic biochemical composition of rhizoma dioscoreae. In the first derivative spectra of rhizoma dioscoreae, the distinguishing characteristic peaks appeared at 467, 484, 870 and 943 cm(-1). Contrasted with rhizoma dioscoreae Raman spectra in the ranges of 600 to 800 cm(-1) and 1 000 to 1 400 cm(-1), the changes in rhizoma dioscoreae Raman first derivative spectra are represented more clearly than the rhizoma dioscoreae Raman spectra. So the rhizoma dioscoreae Raman first derivative spectra can be an accurate supplementary analysis method to the rhizoma dioscoreae Raman spectra.

  4. Ab initio infrared and Raman spectra

    NASA Astrophysics Data System (ADS)

    Fredkin, Donald R.; Komornicki, Andrew; White, Steven R.; Wilson, Kent R.

    1983-06-01

    We discuss several ways in which molecular absorption and scattering spectra can be computed ab initio, from the fundamental constants of nature. These methods can be divided into two general categories. In the first, or sequential, type of approach, one first solves the electronic part of the Schrödinger equation in the Born-Oppenheimer approximation, mapping out the potential energy, dipole moment vector (for infrared absorption) and polarizability tensor (for Raman scattering) as functions of nuclear coordinates. Having completed the electronic part of the calculation, one then solves the nuclear part of the problem either classically or quantum mechanically. As an example of the sequential ab initio approach, the infrared and Raman rotational and vibrational-rotational spectral band contours for the water molecule are computed in the simplest rigid rotor, normal mode approximation. Quantum techniques are used to calculate the necessary potential energy, dipole moment, and polarizability information at the equilibrium geometry. A new quick, accurate, and easy to program classical technique involving no reference to Euler angles or special functions is developed to compute the infrared and Raman band contours for any rigid rotor, including asymmetric tops. A second, or simultaneous, type of ab initio approach is suggested for large systems, particularly those for which normal mode analysis is inappropriate, such as liquids, clusters, or floppy molecules. Then the curse of dimensionality prevents mapping out in advance the complete potential, dipole moment, and polarizability functions over the whole space of nuclear positions of all atoms, and a solution in which the electronic and nuclear parts of the Born-Oppenheimer approximation are simultaneously solved is needed. A quantum force classical trajectory (QFCT) molecular dynamic method, based on linear response theory, is described, in which the forces, dipole moment, and polarizability are computed quantum

  5. Time-Resolved Raman Spectra Measured with an Aerosol Raman Spectrometer

    NASA Astrophysics Data System (ADS)

    Videen, G.; Doughty, D., III; Hill, S. C.; Wetmore, A.; James, D.

    2016-12-01

    Raman spectroscopy yields information about the composition of atmospheric particles, but generally requires offline analysis. To examine temporal trends in aerosol composition we use an automated aerosol Raman spectrometer (Battelle, Columbus, OH) which semi-continuously samples aerosol particles onto a metallized tape and within a few minutes measures the Raman spectra of these. We collected particles (24 hr at 15 minute intervals), clustered their Raman spectra, noted particle composition of many of them, and examined the time variations of numbers of spectra indicating different particle types. We discuss contemporaneous aerosol measurements, the heterogeneity of many particles as indicated by their Raman spectra, and the prevalence of Raman spectra similar to humic-like substances or soot, which we suggest may be related to the relatively large Raman cross sections of materials with extensively conjugated sp2 bonds.

  6. Raman spectra of oxalates in lichen encrustations on Renaissance frescoes

    NASA Astrophysics Data System (ADS)

    Edwards, H. G. M.; Farwell, D. W.; Seaward, M. R. D.

    The vibrational Raman spectra of lichen encrustations on biodeteriorated Renaissance frescoes have been recorded using a laser Raman microprobe. The major chemical species identified in the encrustations is calcium oxalate. Other vibrational features in the Raman spectra have been assigned to fragments of the substratum incorporated from the biodeterioration process and to organic by-products of lichen metabolism such as erythrin, lecanoric acid and meso-erythritol.

  7. Resonant Femtosecond Stimulated Raman Spectra: Theory and Simulations.

    PubMed

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

    2016-05-19

    We present a description of resonant femtosecond stimulated Raman spectra, which is based on the solution of the nonperturbative equation of motion of the chromophore in the laser fields. The theory is applicable for arbitrary shapes and durations of the Raman pulses, accounts for excited-state absorption, and describes nonstationary preparation of the system by an actinic pulse. The method is illustrated by the calculation of femtosecond stimulated Raman spectra of a model system with a conical intersection.

  8. [Raman spectra of fossil dinosaurs from different regions].

    PubMed

    Yang, Qun; Wang, Yi-lin

    2007-12-01

    Raman microscopic spectra in the higher wave number region were obtained from 7 fossil dinosaurs specimens from different regions. The specimens of fossil dinosaurs are different parts of bone. The Raman spectra of fossil dinosaurs indicate the high similarity among peak positions of different fossil dinosaurs; but important differences exist in the spectral peak figures. In the wave number region of 1000-1800 cm(-1) the Raman spectra of the same bone part fossils from different regions are very similar, example similarities between spectra of Lufeing backbone head and Yua nmou backbone head; Lufeng limb bone and Wuding limb bone. There are relations between the same bone part spectra of different fossil dinosaurs. The characteristic does not relate to regions. Raman spectra of fossil dinosaurs cannot be used to distinguish fossil source, although the part of bone can be used as an indicator to narrow the range of possible geographical origins.

  9. [The analysis and identification of fritillaria cirrhosa by Raman spectra].

    PubMed

    Wang, Wen-Na; Chen, Di-Ling; Zhu, Mei-Fang; Zhang, He-Ming

    2013-08-01

    Laser Raman spectrum technology was used to distinguish fritillaria cirrhosa from its adulterants rapidly and accurately. The study is based on that different traditional Chinese medicine contains different chemical compositions, and the differences could be displayed in Raman spectra. The Raman spectra of fritillaria cirrhosas shows that several characteristic strong peaks could be found at 442, 480, 863, 941, 1 083, 1 129, 1 342, 1 463 and 2 910 cm(-1), and a few obvious peaks appear at 111, 302, 360, 409, 527, 579, 618, 718, 767, 1 052, 1 083, 1 207 and 1 261 cm(-1). According to the Raman spectra, a Raman fingerprint of fritillaria cirrhosa was set up, which could be used to distinguish its adulterants. This analysis could be used in identifying fritillaria cirrhosa rapidly, accurately and nondestructively.

  10. Raman intensity and spectra predictions for cylindrical viruses

    NASA Astrophysics Data System (ADS)

    Dykeman, Eric C.; Sankey, Otto F.; Tsen, Kong-Thon

    2007-07-01

    A theoretical framework for predicting low frequency Raman vibrational spectra of viral capsids is presented and applied to the M13 bacteriophage. The method uses a continuum elastic theory for the vibrational modes and a bond-charge polarizability model of an amorphous material to roughly predict the Raman intensities. Comparison is made to experimental results for the M13 bacteriophage virus.

  11. [Vibrational assignment analysis of Raman spectra of fatty alcohols].

    PubMed

    Zou, Qiao; Du, Xian-Yuan; Zhang, Chen; Li, Xing-Chun; Li, Yu

    2013-01-01

    In the present research, Raman spectra of 31 fatty alcohols were calculated by B3LYP/6-31G (d) and verified by taking methanol for example. The study results indicate that B3LYP/6-31G (d) is an effective approach for the fatty alcohols Raman spectra calculated. The vibrational assignment and Raman spectra features of 6 unbranched alcohols were discussed and the vibrating peaks derived from stretching vibration by C-O were chosen as the research target selection, and the multiple principal component regression models were established and validated with the parameters including polarizability, thermodynamic and energy parameters of the above unbranched alcohols. There exists significant correlation between the vibrating peaks derived from stretching vibration by C-O of fatty alcohols and the parameters (sig. = 0.015). This study will benefit the Raman spectra research of homologs.

  12. [Study on Raman Spectra of Some Animal and Plant Oils].

    PubMed

    Wang, Xiang; Dai, Chang-jian

    2015-04-01

    The spectral characteristics of different kinds of oil, either from plant seeds or animal fat, were studied with Raman spectroscopy. The experimental data were processed with the adaptive iteratively reweighted penalized least squares method to realize baseline correction, and provide evident information about their microscopic world. The spectra were analyzed and compared with each other in three parts: the Raman spectra comparison among different samples of plant oils, the analysis of the animal fat and the comparison between plant oils and the animal fat. The differences among the oils were observed in the analysis, including Raman shift and Raman intensity differences. This study not only yields the spectral basis for distinguishing or recognizing the different edible oils, but also confirms that Raman spectroscopy is an effective tool for identifying different oils.

  13. [Raman spectra of YBCO superconductor with hot ultrapressing treatment].

    PubMed

    Yang, Hai-feng; Wei, Le-han; Cao, Xiao-wei

    2002-02-01

    Laser Raman spectra of YBCO oxide superconductor with hot ultrapressing and annealing treatment are reported. In addition to improving physical properties, the spectra data show that the processing can also perfect orthorhombie phase and enhance lattice on orientation trend as well as is good for formation of two dimension CuO2 net. The relation between structure and the superconductivity has been discussed.

  14. Cancer detection based on Raman spectra super-paramagnetic clustering

    NASA Astrophysics Data System (ADS)

    González-Solís, José Luis; Guizar-Ruiz, Juan Ignacio; Martínez-Espinosa, Juan Carlos; Martínez-Zerega, Brenda Esmeralda; Juárez-López, Héctor Alfonso; Vargas-Rodríguez, Héctor; Gallegos-Infante, Luis Armando; González-Silva, Ricardo Armando; Espinoza-Padilla, Pedro Basilio; Palomares-Anda, Pascual

    2016-08-01

    The clustering of Raman spectra of serum sample is analyzed using the super-paramagnetic clustering technique based in the Potts spin model. We investigated the clustering of biochemical networks by using Raman data that define edge lengths in the network, and where the interactions are functions of the Raman spectra's individual band intensities. For this study, we used two groups of 58 and 102 control Raman spectra and the intensities of 160, 150 and 42 Raman spectra of serum samples from breast and cervical cancer and leukemia patients, respectively. The spectra were collected from patients from different hospitals from Mexico. By using super-paramagnetic clustering technique, we identified the most natural and compact clusters allowing us to discriminate the control and cancer patients. A special interest was the leukemia case where its nearly hierarchical observed structure allowed the identification of the patients's leukemia type. The goal of this study is to apply a model of statistical physics, as the super-paramagnetic, to find these natural clusters that allow us to design a cancer detection method. To the best of our knowledge, this is the first report of preliminary results evaluating the usefulness of super-paramagnetic clustering in the discipline of spectroscopy where it is used for classification of spectra.

  15. FT-IR, Raman, and SERS spectra of arcaine sulfate

    SciTech Connect

    Eapen, A.; Joe, I.H.; Aruldhas, G.

    1997-11-01

    Vibrational spectral analysis of arcaine sulfate has been carried out using FT-IR, Raman, and SERS spectra. Raman and FT-IR spectra suggest protonation of the imino groups of the arcaine molecule at the expense of the proton from H{sub 2}SO{sub 4}. Analysis of SERS spectra shows that the molecule is adsorbed to the silver surface through the uncharged amino group and oxygen sites of the sulfate groups. The large enhancement observed for the amino group bending vibrations suggests that the molecule is adsorbed perpendicular to the silver surface.

  16. [Raman spectra calculation and analysis of plasticizer dioctyl phthalate].

    PubMed

    Liu, Yu; Wang, Hu; Wang, Yan; Guo, Mo-ran; Shi, Jing; Feng, Shi-qi; Song, Wei; Zhai Rui-zhi; Cai, Hong-xing

    2015-01-01

    In recent years, with frequent domestic food safety incidents related to the plasticizing agent, the detection of plasticizers in food research becomes increasingly urgent. DEHP is one of the plasticizer. In the present paper, theoretical Raman spectrum and experimental Raman spectrum of DEHP were given. DEHP molecular structure was optimized by DFT(B3LYP) method. DEHP molecular Raman spectra and infrared spectra were calculated with. HF theory and DFT theory based on 3-2G level. The analytical reagent level DEHP Raman spectra was measured, and was compared with theoretical spectra, and good agreements were obtained between the theoretical and experimental results. Because of different calculation methods, we can see that both the wave number and relative intensity of peaks have small differences. DEHP structure parameters were also given in the paper including bond lengths and bond angles etc. Vibrational modes were assigned to all bands between 400 and 3 500 cm-1. Raman spectroscopy study of the commonly used plasticizer dioctyl phthalate was reported in this paper for the first time. This effort will contribute to the research and application of Raman spectroscopy in the field of food testing.

  17. Analytic calculations of anharmonic infrared and Raman vibrational spectra.

    PubMed

    Cornaton, Yann; Ringholm, Magnus; Louant, Orian; Ruud, Kenneth

    2016-02-07

    Using a recently developed recursive scheme for the calculation of high-order geometric derivatives of frequency-dependent molecular properties [Ringholm et al., J. Comp. Chem., 2014, 35, 622], we present the first analytic calculations of anharmonic infrared (IR) and Raman spectra including anharmonicity both in the vibrational frequencies and in the IR and Raman intensities. In the case of anharmonic corrections to the Raman intensities, this involves the calculation of fifth-order energy derivatives-that is, the third-order geometric derivatives of the frequency-dependent polarizability. The approach is applicable to both Hartree-Fock and Kohn-Sham density functional theory. Using generalized vibrational perturbation theory to second order, we have calculated the anharmonic infrared and Raman spectra of the non- and partially deuterated isotopomers of nitromethane, where the inclusion of anharmonic effects introduces combination and overtone bands that are observed in the experimental spectra. For the major features of the spectra, the inclusion of anharmonicities in the calculation of the vibrational frequencies is more important than anharmonic effects in the calculated infrared and Raman intensities. Using methanimine as a trial system, we demonstrate that the analytic approach avoids errors in the calculated spectra that may arise if numerical differentiation schemes are used.

  18. Analytic calculations of anharmonic infrared and Raman vibrational spectra

    PubMed Central

    Louant, Orian; Ruud, Kenneth

    2016-01-01

    Using a recently developed recursive scheme for the calculation of high-order geometric derivatives of frequency-dependent molecular properties [Ringholm et al., J. Comp. Chem., 2014, 35, 622], we present the first analytic calculations of anharmonic infrared (IR) and Raman spectra including anharmonicity both in the vibrational frequencies and in the IR and Raman intensities. In the case of anharmonic corrections to the Raman intensities, this involves the calculation of fifth-order energy derivatives—that is, the third-order geometric derivatives of the frequency-dependent polarizability. The approach is applicable to both Hartree–Fock and Kohn–Sham density functional theory. Using generalized vibrational perturbation theory to second order, we have calculated the anharmonic infrared and Raman spectra of the non- and partially deuterated isotopomers of nitromethane, where the inclusion of anharmonic effects introduces combination and overtone bands that are observed in the experimental spectra. For the major features of the spectra, the inclusion of anharmonicities in the calculation of the vibrational frequencies is more important than anharmonic effects in the calculated infrared and Raman intensities. Using methanimine as a trial system, we demonstrate that the analytic approach avoids errors in the calculated spectra that may arise if numerical differentiation schemes are used. PMID:26784673

  19. Photoinduced changes in the Raman spectra of germanosilicate optical fibres

    SciTech Connect

    Vasil'ev, Sergei A; Dianov, Evgenii M; Koltashev, V V; Mashinsky, V M; Medvedkov, O I; Plotnichenko, V G; Pyrkov, Yu N; Sazhin, O D; Frolov, A A; Marchenko, V M

    1998-04-30

    An investigation was made of changes in the Raman spectra of germanosilicate optical fibres as a result of UV irradiation. The photoinduced changes in the spectra were of the same nature for all types of irradiation used. These changes increased with increase in the radiation dose and in the GeO{sub 2} concentration in the fibre core and were evidence of a structural modification of glass. (nonlinear optical phenomena and devices)

  20. Raman spectra of olivine measured in different planetary environments

    NASA Astrophysics Data System (ADS)

    Weber, I.; Böttger, U.; Pavlov, S.; Grunow, D.; Jessberger, E. K.; Hübers, H.-W.

    2012-09-01

    Missions to bodies of our solar system are coming up and imply new instrumentation to be applied remotely and in situ. In ESA's ExoMars mission the Raman Laser Spectrometer (RLS) will identify minerals and organic compounds in Martian surface rocks and soils. Here we present the results of a Raman study of different olivines with variable Fo and Fa contents. We chose olivine because it is a rock forming mineral and is found as an abundant mineral in Martian meteorites. We determined the Raman spectra in different environmental conditions that include vacuum, 8mbar CO2 atmosphere and temperatures between room temperature and 10K. These environmental conditions resemble those on asteroids as well as on Mars and Moon. Thus our study investigates the influence of these varying conditions on the position and band width of the Raman lines, which is to be known when such investigations are performed in future space missions.

  1. Low-Cost Elimination of Plasma Lines in Raman Spectra.

    ERIC Educational Resources Information Center

    Behlow, Herbert W., Jr.; Petersen, John D.

    1985-01-01

    Describes a low-cost ($120) device which eliminates plasma lines in Raman spectra. The device consists of two prisms and two mirrors which are held in a symmetrical relationship to one another so that a particular position will allow only one wavelength to pass through on a given axis. (JN)

  2. Low-Cost Elimination of Plasma Lines in Raman Spectra.

    ERIC Educational Resources Information Center

    Behlow, Herbert W., Jr.; Petersen, John D.

    1985-01-01

    Describes a low-cost ($120) device which eliminates plasma lines in Raman spectra. The device consists of two prisms and two mirrors which are held in a symmetrical relationship to one another so that a particular position will allow only one wavelength to pass through on a given axis. (JN)

  3. Raman rotational spectra of endohedral C60 fullerene complexes

    NASA Astrophysics Data System (ADS)

    Hernández-Rojas, J.; Bretón, J.; Gomez Llorente, J. M.

    1996-09-01

    Low-temperature (T=50 K) Raman rotational spectra are calculated for the endohedral complexes Li+@C60, Na+@C60, CO@C60, LiF@C60, and LiH@C60. The systems Na+@C60 and CO@C60 produce very similar spectra dominated by pure rotational bands. The other systems present more complex and dissimilar spectra which suggest librational motions and hindered rotations. An assignment of these spectra is provided by analyzing the structure of the low energy rotational eigenvalues and eigenfunctions. Rotational energy quasiband and quasiresonance-band structures are found to be the origin of the features observed in the more complex spectra. Out of these analyses, a classification of the low-temperature rotational spectra of endohedral C60 complexes in two basic classes emerges.

  4. Anomalous Raman spectra from La2CuO4

    NASA Astrophysics Data System (ADS)

    Burns, Gerald; Dacol, F. H.

    1990-03-01

    We show that some published Raman spectra from the superconductors (La2-xSrx)CuO4 and La2NiO4 are incorrect. We believe that these spectra were obtained when the samples were ``burnt'' by the focused laser beam and were actually due to La2O3. Similar anomalous results can be obtained when starting with Nd2CuO4 where the spectra come from Nd2O3. A spectrum distinctly different from those of La2O3 or Nd2O3 is obtained from Y2O3.

  5. Genesis of enhanced Raman bands in SERS spectra of 2-mercaptoimidazole: FTIR, Raman, DFT, and SERS.

    PubMed

    Chandra, Subhendu; Chowdhury, Joydeep; Ghosh, Manash; Talapatra, G B

    2012-11-15

    The surface enhanced Raman scattering (SERS) spectra of biologically and industrially significant, 2-mercaptoimidazole (2-MI) molecule have been investigated. The SERS spectra of the molecule at different concentrations of the adsorbate are compared with its Fourier transform infrared (FTIR) and normal Raman spectra (NRS) in varied environments. The optimized molecular structures and vibrational wavenumbers of the various forms (ca. cationic, neutral, ylidic, anionic) of the molecule have been estimated from the density functional theory (DFT). The vibrational signatures of the molecule have been assigned for the first time from the potential energy distributions (PEDs). The analyses of the Raman vibrational signatures reveal the coexistence of all the different forms of the molecule in the solid state and in aqueous solution. Concentration dependent SERS spectra of the molecule at neutral pH of the medium together with the multivariate data analyses techniques also suggest the concomitance of all the probable forms of the molecule in the surface adsorbed state. The genesis of selective enhancements of the Raman bands in the SERS spectra emanating from the cationic, neutral, ylidic and anionic forms of the molecule have been divulged from the view of the Albretcht's "A" and Herzberg-Teller (HT) charge transfer (CT) contribution.

  6. Complete symmetry analysis of the Raman spectra in cuprates

    NASA Astrophysics Data System (ADS)

    Venturini, F.; Zhang, Q.-M.; Hackl, R.; Erb, A.; Berger, H.; Revaz, B.; Nagao, Y.; Ando, Y.

    2002-03-01

    We describe results of Raman scattering measurements on differently doped cuprate single crystals. We performed a complete polarization analysis, using circular in addition to the commonly used linear polarizations. This allowed us to determine all symmetry components of the Raman signal being characteristic for tetragonal systems, including A_2g excitations which indicate the presence of a time-reversal broken symmetry in these systems. The A_2g signal has an intensity comparable to that of the other symmetries, but exhibits a distinctly different frequency dependence. In particular, there is a gap at low energies which decreases with increasing doping. The Raman relaxation rates and mass renormalization factor extracted from the pure B_1g and B_2g spectra are consistent with IR-results, and the unphysical drop of 1+λ(ω) below unity for high frequencies disappears teopel. 99 opel M. Opel et al., Phys. Rev. B 61, 9752 (2000). thebibliography

  7. Raman spectra and optical coherent tomography images of skin

    NASA Astrophysics Data System (ADS)

    Villanueva-Luna, A. E.; Castro-Ramos, J.; Vazquez-Montiel, S.; Flores-Gil, A.; Delgado-Atencio, J. A.; Vazquez-Villa, A.

    2011-03-01

    The optical coherence tomography images are useful to see the internal profile and the structure of material samples. In this work, OCT images were recorded in 10 volunteers with different skin tone which were related to Raman spectra. The areas where we obtained OCT images and Raman spectra were a) index finger nail, b) between index finger and middle finger, c) middle finger tip, d) half of middle finger, e) the thumb finger tip and f) between index finger and thumb, areas measured were for the purpose of finding extracellular fluids with contain triglycerides, cholesterol and glucose that are reported in the literature. The excitation wavelength used for this work was 785 nm, a spectrometer of 6 cm-1 resolution. The spectral region used ranges from 300 to 1800 cm-1. We use an OCT with 930 nm of Central Wavelength, 1.6 mm of Image Depth, 6 mm of image width and 6.2 μm of axial resolution.

  8. Detection of Raman spectra in ocular drugs for potential in vivo application of Raman spectroscopy.

    PubMed

    Elshout, Mari; Erckens, Roel J; Webers, Carroll A; Beckers, Henny J; Berendschot, Tos T; de Brabander, John; Hendrikse, Fred; Schouten, Jan S

    2011-10-01

    Raman spectroscopy holds potential for the assessment of intraocular pharmacokinetics. Raman spectra of ocular drugs were acquired, to determine the drug-specific Raman signature. The ability of the Raman technique to quantify drug concentrations was also investigated. The experimental setup was based on a High Performance Raman Module 2500 Raman module, designed for 180° "backscatter" signal detection in the wavenumber range of 400-1,800 cm(-1). Excitation source was a diode laser emitting a beam with a wavelength of 785 nm and a power of 10 mW. Laser light was focused in the sample with a long-working-distance microscope objective (25×/0.50). Samples were measured in quartz cuvettes in 10 sequential measurements, with exposure time 30 s. The total number of measured drugs was 49. To determine whether signal intensity and drug concentration correlate, 2 drugs were diluted in water and measured with 120 s exposure time at different concentrations. An active ingredient-specific Raman signature was detected in 4 glaucoma drugs, 6 mydriatics, 5 antibiotics, 4 anesthetics, 3 anti-inflammatory drugs, 2 types of artificial tears, and 5 other drugs. In 20 drugs, no specific Raman signature was detected. Linear correlation of drug concentration with signal intensity was high (R(2)≥0.94). Using low laser powers, Raman signatures for 29 commonly used ocular drugs were detected. Correlation of drug concentration with signal intensity is high, which is essential for monitoring drug concentration in ocular media. The presented results encourage the use of Raman spectroscopy to acquire detailed information on the pharmacokinetics of these ocular drugs.

  9. Processing Raman Spectra of High-Pressure Hydrogen Flames

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Kojima, Jun

    2006-01-01

    The Raman Code automates the analysis of laser-Raman-spectroscopy data for diagnosis of combustion at high pressure. On the basis of the theory of molecular spectroscopy, the software calculates the rovibrational and pure rotational Raman spectra of H2, O2, N2, and H2O in hydrogen/air flames at given temperatures and pressures. Given a set of Raman spectral data from measurements on a given flame and results from the aforementioned calculations, the software calculates the thermodynamic temperature and number densities of the aforementioned species. The software accounts for collisional spectral-line-broadening effects at pressures up to 60 bar (6 MPa). The line-broadening effects increase with pressure and thereby complicate the analysis. The software also corrects for spectral interference ("cross-talk") among the various chemical species. In the absence of such correction, the cross-talk is a significant source of error in temperatures and number densities. This is the first known comprehensive computer code that, when used in conjunction with a spectral calibration database, can process Raman-scattering spectral data from high-pressure hydrogen/air flames to obtain temperatures accurate to within 10 K and chemical-species number densities accurate to within 2 percent.

  10. Raman spectra of solid benzene under high pressure

    NASA Technical Reports Server (NTRS)

    Thiery, M.-M.; Kobashi, K.; Spain, I. L.

    1985-01-01

    Raman spectra of solid benzene have been measured at room temperature up to about 140 kbar, using the diamond anvil cell. Effort has been focused upon the lattice vibration spectra at pressures above that of phase II. It is found that a change in slopes occurs in the frequency-pressure curves at about 40 kbar. Furthermore, a new band appears above 90 kbar. These features probably correspond respectively to the II-III phase transition, which has been reported previously, and a III-IV phase transition, reported here for the first time.

  11. IR and Raman spectra of liquid water: theory and interpretation.

    PubMed

    Auer, B M; Skinner, J L

    2008-06-14

    IR and Raman (parallel- and perpendicular-polarized) spectra in the OH stretch region for liquid water were measured some years ago, but their interpretation is still controversial. In part, this is because theoretical calculation of such spectra for a neat liquid presents a formidable challenge due to the coupling between vibrational chromophores and the effects of motional narrowing. Recently we proposed an electronic structure/molecular dynamics method for calculating spectra of dilute HOD in liquid D(2)O, which relied on ab initio calculations on clusters to provide a map from nuclear coordinates of the molecules in the liquid to OH stretch frequencies, transition dipoles, and polarizabilities. Here we extend this approach to the calculation of couplings between chromophores. From the trajectories of the fluctuating local-mode frequencies, transition moments, and couplings, we use our recently developed time-averaging approximation to calculate the line shapes. Our results are in good agreement with experiment for the IR and Raman line shapes, and capture the significant differences among them. Our analysis shows that while the coupling between chromophores is relatively modest, it nevertheless produces delocalization of the vibrational eigenstates over up to 12 chromophores, which has a profound effect on the spectroscopy. In particular, our results demonstrate that the peak in the parallel-polarized Raman spectrum at about 3250 wavenumbers is collective in nature.

  12. Efficacious calculation of Raman spectra in high pressure hydrogen

    NASA Astrophysics Data System (ADS)

    Ackland, G. J.; Magdau, I. B.

    2014-04-01

    We present and evaluate an efficient method for simulating Raman spectra from molecular dynamics calculations without defining normal modes. We apply the method to high pressure hydrogen in the high-temperature "Phase IV": a plastic crystal in which the conventional picture of fixed phonon eigenmodes breaks down. Projecting trajectories onto in-phase molecular stretches is shown to be many orders of magnitude faster than polarisability calculations, allowing statistical averaging at high-temperature. The simulations are extended into metastable regimes and identify several regimes associated with symmetry-breaking on different timescales, which are shown to exhibit features in the Raman spectra at the current experimental limit of resolvability. In this paper we have concentrated on the methodology, a fuller description of the structure of Phase IV hydrogen is given in a previous paper [Magdau IB, Ackland GJ. Identification of high-pressure phases III and IV in hydrogen: simulating Raman spectra using molecular dynamics. Phys Rev B. 2013;87:174110].

  13. [Raman spectra of carbon fibers during electrochemical treatment].

    PubMed

    Zhang, Min; Zhu, Bo; Wang, Cheng-guo; Wei, Han-xing

    2010-01-01

    Laser Raman spectroscopy was employed to characterize the microstructure variations of polyacrylonitrile-based carbon fibers during electrochemical treatment, and the characteristics of first-order Raman spectra of carbon fibers with different treatment time were investigated in the present paper. The results indicate that the Raman spectra of the carbon fibers can be fitted into four bands, named as D (or D1) band, G band, D2 band and D3 band, respectively. The Raman parameters to characterize surface microstructure variations of carbon fibers mainly include R(I(D2)) / I(G), area ratio of D band and G band), I(D2) / I(G) (area ratio of D2 band and G band), I(D3) / I(G) (area ratio of D3 band and G band), and I(D(S))/ I(G) (area ratio of all the disordered structure and G band). The peak separation between D band and G band becomes large after electrochemical treatment. R increases, which indicates that the surface disordered degree of carbon fibers increases. I(D3) / I(G) increases, which is caused by organic molecules, fragments or functional groups; decreases which is caused by the break of the aliphatic structures. With increasing treatment time, I(D(S)) / I(G) increases continuously, and the change trend of l(D(S)) / I(G) is consistent with that of R value, which can be used to comprehensively explain the variation of the surface structure of carbon fibers. So, the variety rules of the structure of carbon fibers can be investigated by laser Raman spectroscopy during electrochemical treatment.

  14. Surface-enhanced Raman scattering spectra of tomato epidermis on gold/ silver sol active substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Chen, Zhenyi; Chen, Na; Hu, Ling; Zhu, Hongfei; Liu, Shupeng; Guo, Qiang

    2011-12-01

    In this paper, tomato epidermis' surface-enhanced Raman scattering spectra were measured on gold and silver active substrates and analyzed. Preparing and using gold sol and silver sol in similar particle diameters (about 50-60nm), three comparable Raman spectra were obtained. Silver sol and gold sol can both increase Raman scattering signal of tomato epidermis. Through the Raman spectra, silver sol has greater enhancement ability than gold sol to tomato epidermis.

  15. Polarised IR and Raman spectra of monoglycine nitrate single crystal

    NASA Astrophysics Data System (ADS)

    Baran, Jan A.; Drozd, Marek A.; Ratajczak, Henryk

    2010-07-01

    Polarised Raman spectra of the monoglycine (monoglycinium) nitrate (hereafter MGN) single crystal are reported. Additionally, the polarised specular reflection spectra for the (1 0 0) single crystal sample (E|| Y( b) and E|| Z( c)) were measured in the region 3600-80 cm -1. The spectra of the imaginary parts of the refractive indices are computed by the Kramers-Kronig transformation (Opus). The polarised spectra are discussed with respect to the diffraction crystal structure and recent literature data on normal co-ordinate analysis for the glycinium cation ( +NH 3CH 2COOH). The stretching vibrations of the NH3+ groups are explained by considering their hydrogen bonds. The intensity of the Raman bands arising from the stretching vibrations of the CH 2 group are explained assuming that each C sbnd H bond stretches independently. This finding is unusual and suggests that the C(2) sbnd H(5) bond is involved in the hydrogen bonding (improper hydrogen bond). The deformation vibrations of the CH 2 group are explained assuming scissoring, twisting, wagging and rocking type of vibrations. The band at 871 cm -1 exhibits the CC stretching character of the CCN skeleton, whereas the band at ca. 1050 cm -1 shows the νaCCN character. The stretching νOH vibrations of the C sbnd O sbnd H⋯O hydrogen bond gives rise to a band at ca. 3087 cm -1, clearly seen in the Y( xx) Z Raman spectrum. Its γOH mode appears at 896 cm -1. The δOH vibration is coupled to other vibrations, although the IR band at ca. 1375 (E|| Y) likely arises from this mode. It was impossible to define a character of the glycinium cations deformation vibrations giving rise to the bands observed in between 680 and 490 cm -1, on the basis of their polarisation properties. The polarisation properties of the internal modes of the nitrate ions are discussed.

  16. Complete analytic anharmonic hyper-Raman scattering spectra.

    PubMed

    Cornaton, Yann; Ringholm, Magnus; Ruud, Kenneth

    2016-08-10

    We present the first computational treatment of the complete second-order vibrational perturbation theory applied to hyper-Raman scattering spectroscopy. The required molecular properties are calculated in a fully analytic manner using a recently developed program [Ringholm, Jonsson and Ruud, J. Comp. Chem., 2014, 35, 622] that utilizes recursive routines. For some of the properties, these calculations are the first analytic calculations of their kind at their respective levels of theory. We apply this approach to the calculation of the hyper-Raman spectra of methane, ethane and ethylene and compare these to available experimental data. We show that the anharmonic corrections have a larger effect on the vibrational frequencies than on the spectral intensities, but that the inclusion of combination and overtone bands in the anharmonic treatment can improve the agreement with the experimental data, although the quality of available experimental data limits a detailed comparison.

  17. Near infrared Raman spectra of human brain lipids

    NASA Astrophysics Data System (ADS)

    Krafft, Christoph; Neudert, Lars; Simat, Thomas; Salzer, Reiner

    2005-05-01

    Human brain tissue, in particular white matter, contains high lipid content. These brain lipids can be divided into three principal classes: neutral lipids including the steroid cholesterol, phospholipids and sphingolipids. Major lipids in normal human brain tissue are phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidic acid, sphingomyelin, galactocerebrosides, gangliosides, sulfatides and cholesterol. Minor lipids are cholesterolester and triacylglycerides. During transformation from normal brain tissue to tumors, composition and concentration of lipids change in a specific way. Therefore, analysis of lipids might be used as a diagnostic parameter to distinguish normal tissue from tumors and to determine the tumor type and tumor grade. Raman spectroscopy has been suggested as an analytical tool to detect these changes even under intra-operative conditions. We recorded Raman spectra of the 12 major and minor brain lipids with 785 nm excitation in order to identify their spectral fingerprints for qualitative and quantitative analyses.

  18. Model investigation of the Raman spectra of amorphous silicon

    NASA Astrophysics Data System (ADS)

    Marinov, M.; Zotov, N.

    1997-02-01

    A model for calculating the first-order Raman spectra of amorphous silicon (a-Si) without adjustable parameters is proposed. Calculations on the original 216-atom model of a-Si, generated by the algorithm of Wooten, Winer, and Weaire (WWW) are in very good agreement with experimental spectra and give further indication that the WWW cluster is a realistic model of moderately disordered a-Si. The TA-TO assignment of the low and high frequency bands is supported by direct numerical calculations of the phase quotient and the stretching character of the vibrational modes. The calculated participation ratios and correlation lengths of the vibrational modes indicate that the high-frequency TO-like modes are strongly localized on defects. The relative intensities of the TA-, LA-, and LO-like bands depend on the intermediate-range order, while that of the TO-like band mainly on the short-range order.

  19. Raman spectra of amorphous carbon films deposited by SWP

    NASA Astrophysics Data System (ADS)

    Xu, Junqi; Liu, Weiguo; Hang, Lingxia; Su, Junhong; Fan, Huiqing

    2010-10-01

    Amorphous carbon film is one of the most important anti-reflection protective films coated on infrared optical components. In this paper, hydrogen-free amorphous carbon films were deposited by new type surface-wave-sustained plasma (SWP) source with a graphite target at various experiment parameters. The laser Raman spectroscopy at wavelength of 514 nm was used to investigate the structure and bonding of these carbon films. The results showed consanguineous correlations between the intensity ratio ID/IG and the experiment parameters such as microwave power, target voltage and gas pressure applied to the SWP source. Raman spectra proved the structure of these carbon films prepared by SWP technique is typical diamond-like carbon (DLC). The analysis on G peak position and intensity ratio ID/IG indicated that Raman shifts moves to low wavenumber and ID/IG decreases with the increasing of microwave power from 150 W to 330 W. These results means the formation of sp3 bond prefers higher microwave power. DLC films prepared at target voltage of -200 V have higher sp3 content than that of -350 V, moreover, an increase of gas pressure during experiments yields higher sp3 content at the microwave power below 270 W, whereas the change of sp3 content is slight with the various conditions when microwave power exceeds 270 W.

  20. Temperature dependence of resonance Raman spectra of carotenoids

    NASA Astrophysics Data System (ADS)

    Andreeva, A.; Apostolova, I.; Velitchkova, M.

    2011-04-01

    To understand the mechanism of the photoprotective and antioxidative functions of carotenoids, it is essential to have a profound knowledge of their excited electronic and vibronic states. In the present study we investigate the most powerful antioxidants: β-carotene and lutein by means of resonance Raman spectroscopy. The aim was to study in detail their Raman spectra in solution at room temperature and their changes as a function of temperature. To measure the spectra in their natural environment pyridine has been used as a solvent. It has been chosen because of its polarizability ( n = 1.5092) which is close to that of membrane lipids and proteins. The temperature dependence of the most intensive ν1 band in the range from 77 K to 295 K at 514.5 nm excitation has been obtained. It was found that in pyridine the C dbnd C stretching frequency, its intensity, line shape, and line width are very sensitive to the temperature (the sensitivity being different for the two studied carotenoids). The observed linear temperature dependence of the C dbnd C stretching frequency is explained by a mechanism involving changes of the vibronic coupling and the extent of π-electron delocalization. The different behavior of the temperature-induced broadening of the ν1 band and its intensity for the two studied carotenoids can be associated with the different nature of their solid matrices: glassy for β-carotene and crystalline-like for lutein, owing to their different chemical structures.

  1. Raman and infrared spectra of stibnite, Sb2S3

    NASA Astrophysics Data System (ADS)

    Ilinca, G.; Caracas, R.

    2006-12-01

    Stibnite, Sb2S3 is a small-gap quasi-one-dimensional semiconductor (PhChMin, 32, 295-300, 2005) and a structural archetype for a variety of sulfide and sulfosalt minerals. Despite its widespread natural occurrence and its mineralogical importance, the physical properties are barely studied. Here, we combine experimental and theoretical approaches to analyze its zone-center dynamical properties. We measure the powder infrared reflectivity spectra and the powder Raman spectra under ambient conditions of pressure and temperature. We calculate the normal mode frequencies within the density functional perturbation theory, as implemented in the ABINIT package. With 20 atoms in the unit cell, stibnite has 60 normal modes, which according to the group theory decompose in Gamma as 10A_g+5B1g+10B2g+5B3g + 5A_u+10B1u+5B2u+10B3u. The acoustic modes have characters B1u+B2u+B3u. The Au modes are silent whereas all the other modes are active. The optical modes are distributed over a narrow 0-350 cm-1 frequency range. The infrared reflectivity spectrum shows a multitude of peaks, which are poorly differentiated and highly overlapping. The Raman spectrum is better differentiated, with five main peaks. The main infrared mode lays around 246 cm-1 and represents a superposition of at least one B3u and one B1u modes.

  2. [IR and Raman spectra studies of Rotundine based on DFT].

    PubMed

    Li, Jun-Ping; Zhou, Guang-Ming; Zhang, Li-Jun; Cheng, Hong-Mei; Qin, Hong-Ying

    2014-11-01

    Infrared spectroscopy (IR), the normal Raman spectroscopy (NRS) and the surface enhanced Raman spectroscopy (SERS) in new Ag/Cu nanomaterial of Rotundine were studied in the present paper. The IR and the NRS of Rotundine were calculated by the density functional theory (DFT) using B3LYP/6-311+G(d, p), then the spectral intensity graph of Rotundine were given. The vibrational peaks were assigned comprehensively by the visualization software of Gauss view 5. 0. Rotundine has obvious infrared and Raman vibrational peak in the wave number range of 3 300-2500 and 1 800-600 cm(-1). SnCl2 and PVP was used as capping agent for the silver nanoparticles in SERS of Rotundine. Finally, by using the method of cyclic immersion well dispersed silver nanoparticles was obtained and achieved good enhancement effect. This molecule acquired strong selective enhancement vibration peak, In the wave number ranges of 1 500-1 400 and 1 000-700 cm(-1) the enhancement effect is most obvious. After analyzed, the methylene of this molecule is adsorbed on the silver nanoparticles surface and the angle between the benzene ring and the silver substrate is close to 90 degrees. The theoretically calculated spectra of Rotundine are consistent with the obtained experimental spectra. There are some differences may be due to the interaction forces between molecules and so on. The visualization software displayed the structure characteristics and molecular group vibration of this molecular visually and provided important basis for assigning the vibrational peaks. Rotundine is an important traditional Chinese medicine agent contained in many kinds of sedative drugs. The study provides a strong basis for the rapid, feature and trace identification of Rotundine and also supplies important reference for the biological role of central inhibition of analgesic drugs.

  3. A COMPARISON OF FAR INFRARED AND RAMAN SPECTRA OF SOME RARE EARTH GARNET SINGLE CRYSTALS,

    DTIC Science & Technology

    RARE EARTH COMPOUNDS, *INFRARED SPECTRA), (*GARNET, RARE EARTH COMPOUNDS), (* RAMAN SPECTROSCOPY, RARE EARTH COMPOUNDS), SINGLE CRYSTALS, ALUMINATES...PHONONS, YTTRIUM COMPOUNDS, YTTERBIUM COMPOUNDS, TERBIUM COMPOUNDS, DYSPROSIUM COMPOUNDS, CANADA

  4. Quantum spectra of Raman photon pairs from a mesoscopic particle

    NASA Astrophysics Data System (ADS)

    Ooi, C. H. Raymond; Loh, W. M. Edmund; Kam, C. H.

    2015-06-01

    Quantum Langevin formalism with noise operators is used to provide quantum descriptions of photon pairs (the Stokes and anti-Stokes fields) emitted by a mesoscopic spherical particle composed of quantum particles in a double Raman configuration. The spectra of the fields obtained are sensitive to the dimension of the microsphere and can be controlled by pump and control laser fields. Spectral peaks due to quantum coherence are Stark shifted by the laser fields experiencing autofocusing inside the spherical particle, causing broadening of peaks as the size of the microsphere increases. The antinormal-order spectrum is found to be identical to the normal-order spectrum. The anti-Stokes spectrum is identical to the Stokes spectrum when the linear dispersion is neglected. Frequency-dependent dielectric functions of the Stokes and anti-Stokes spectra corresponding to the linear dispersions of the particle yield narrow morphology-dependent resonance gain peaks at certain frequencies of the Stokes and anti-Stokes spectra that depend not only on the particle size but also on the angle of observation.

  5. Detection of skin cancer by classification of Raman spectra.

    PubMed

    Sigurdsson, Sigurdur; Philipsen, Peter Alshede; Hansen, Lars Kai; Larsen, Jan; Gniadecka, Monika; Wulf, Hans Christian

    2004-10-01

    Skin lesion classification based on in vitro Raman spectroscopy is approached using a nonlinear neural network classifier. The classification framework is probabilistic and highly automated. The framework includes a feature extraction for Raman spectra and a fully adaptive and robust feedforward neural network classifier. Moreover, classification rules learned by the neural network may be extracted and evaluated for reproducibility, making it possible to explain the class assignment. The classification performance for the present data set, involving 222 cases and five lesion types, was 80.5%+/-5.3% correct classification of malignant melanoma, which is similar to that of trained dermatologists based on visual inspection. The skin cancer basal cell carcinoma has a classification rate of 95.8%+/-2.7%, which is excellent. The overall classification rate of skin lesions is 94.8%+/-3.0%. Spectral regions, which are important for network classification, are demonstrated to reproduce. Small distinctive bands in the spectrum, corresponding to specific lipids and proteins, are shown to hold the discriminating information which the network uses to diagnose skin lesions.

  6. Thermal Conductivity and Raman Spectra of Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Liu, Xuebo; Dong, Hua; Li, Yan; Mei, Ning

    2017-10-01

    Due to its unique physical properties, carbon fiber (CF) has been widely studied for extensive application in aerospace and machinery. In this study, the thermal diffusivity of three kinds of CF sample is characterized by the transient electrothermal technique at room temperature. By subtracting the effect of radiative losses, the effective thermal diffusivity of CFs can be calculated as 6.46× 10^{-6} m2\\cdot s^{-1}, 6.58× 10^{-6} m2\\cdot s^{-1} and 2.01× 10^{-4} m2\\cdot s^{-1}, respectively. For the first time, the emissivity coefficient of carbon fiber is calibrated as 0.78. Combined with Raman spectra and phonon scattering, we found that the better crystalline structure and low defect in CF have an obvious impact on its thermal diffusivity.

  7. Detection of high-resolution Raman spectra in short oligonucleotides

    NASA Astrophysics Data System (ADS)

    Bairamov, F. B.; Poloskin, E. D.; Chernev, A. L.; Toporov, V. V.; Dubina, M. V.; Lahderanta, E.; Lipsanen, H.; Bairamov, B. Kh.

    2014-06-01

    High-resolution spectra of single-chain short oligonucleotides d(20G, 20T), where d is a deoxyribonucleoside, G is guanine, and T is thymine, have been obtained by the highly sensitive nonresonant Raman scattering method of biomacromolecules. In addition to their own multifunctional significance, short oligonucleotides attract interest as ideal model objects for revealing poorly studied peculiarities of tertiary and quaternary structures of DNA. The detection of narrow spectral lines has allowed determining the characteristic time scale and makes it possible to study the dynamics of fast relaxation processes of vibrational motions of atoms in biomacromolecules. It has been found that the FWHM of the narrowest 1355.4 cm-1 spectral line attributed to the vibrations of the dT methyl group is 14.6 cm-1. The corresponding lifetime is 0.38 ps.

  8. [Raman, FTIR spectra and normal mode analysis of acetanilide].

    PubMed

    Liang, Hui-Qin; Tao, Ya-Ping; Han, Li-Gang; Han, Yun-Xia; Mo, Yu-Jun

    2012-10-01

    The Raman and FTIR spectra of acetanilide (ACN) were measured experimentally in the regions of 3 500-50 and 3 500-600 cm(-1) respectively. The equilibrium geometry and vibration frequencies of ACN were calculated based on density functional theory (DFT) method (B3LYP/6-311G(d, p)). The results showed that the theoretical calculation of molecular structure parameters are in good agreement with previous report and better than the ones calculated based on 6-31G(d), and the calculated frequencies agree well with the experimental ones. Potential energy distribution of each frequency was worked out by normal mode analysis, and based on this, a detailed and accurate vibration frequency assignment of ACN was obtained.

  9. Pre-processing of ultraviolet resonance Raman spectra.

    PubMed

    Simpson, John V; Oshokoya, Olayinka; Wagner, Nicole; Liu, Jing; JiJi, Renee D

    2011-03-21

    The application of UV excitation sources coupled with resonance Raman have the potential to offer information unavailable with the current inventory of commonly used structural techniques including X-ray, NMR and IR analysis. However, for ultraviolet resonance Raman (UVRR) spectroscopy to become a mainstream method for the determination of protein secondary structure content and monitoring protein dynamics, the application of multivariate data analysis methodologies must be made routine. Typically, the application of higher order data analysis methods requires robust pre-processing methods in order to standardize the data arrays. The application of such methods can be problematic in UVRR datasets due to spectral shifts arising from day-to-day fluctuations in the instrument response. Additionally, the non-linear increases in spectral resolution in wavenumbers (increasing spectral data points for the same spectral region) that results from increasing excitation wavelengths can make the alignment of multi-excitation datasets problematic. Last, a uniform and standardized methodology for the subtraction of the water band has also been a systematic issue for multivariate data analysis as the water band overlaps the amide I mode. Here we present a two-pronged preprocessing approach using correlation optimized warping (COW) to alleviate spectra-to-spectra and day-to-day alignment errors coupled with a method whereby the relative intensity of the water band is determined through a least-squares determination of the signal intensity between 1750 and 1900 cm(-1) to make complex multi-excitation datasets more homogeneous and usable with multivariate analysis methods.

  10. Absorption and resonance Raman spectra of Pb2, Pb3, and Pb4 in xenon matrices

    NASA Technical Reports Server (NTRS)

    Stranz, D. D.; Khanna, R. K.

    1981-01-01

    Matrix isolation techniques are used to investigate the spectra of lead molecules and, in particular, to obtain resonance Raman spectra of lead vapors isolated in solid xenon matrices. The presence of Pb2 is confirmed by the visible adsorption, and Raman spectra yield a vibrational frequency for the ground state of 108 per cm and a dissociation energy of 8200 per cm. A second resonance Raman progression indicates a Pb3 species of D3h symmetry. Finally, two additional Raman features at approximately 111 per cm spacing are evidence for a third species, tentatively identified as Pb4.

  11. [Raman and infrared spectra of non-stoichiometry uranium oxides].

    PubMed

    Lü, Jun-Bo; Li, Gan; Guo, Shu-Lan

    2014-02-01

    Both of Raman and infrared spectra of seven non-stoichiometry and threestoichiometry uranium oxides, including UO2, U3O7 and UO(2+x) (0spectra of UO(2+x) in the stoichiometry range, U3O7 to U3O8, were first obtained and reported. Three typical peaks were observed at 445, 578 and 1150 cm(-1) in the Raman spectrum of uranium dioxide. The intensities of the peaks at 578 and 1151 cm(-1) decrease quickly with increasing x value of UO(2+x), and while x=0.19, the two peaks disappear. Such peaks can therefore be considered as a fin-gerprint of the quasi-perfect UO2 fluorite structure. The peak at 445 cm(-1) tends to weaken, broaden and shift to higher wavenumber in more oxidised samples. When x=0.32, this peak is shifted to the 459 cm(-1) and a weak peak at about 630 cm(-1) appears. The two new peaks are typical of the tetragonal U3O7. While x> or =0.39, the peak at 459 cm(-1) further splits into separate components. Two peaks at 235 and 754 cm(-1) appear for UO(2.39) and are visible with increased intensity as the oxygen-uranium ratio is increased. And the Raman spectra of UO(2+x) are gradually close to U3O8 in the alpha-phase, which has an orthorhombic unit cell. But several strongest features of the alpha-U3O8 specturm at 333, 397, 483 and 805 cm(-1) are still not outstanding even in UO(2.60). The main feature of the UO2 infrared spectrum shows a very broad and strong adsorption band at 400-570 cm(-1) and another feature is a weak adsorption peak at about 700 cm(-1). The 400-570 cm(-1) band undergoes a progressive splitting into two new peaks at approximately 421 and approximately 515 cm(-1) through increasing incorporation of oxygen into UO2. The weak peak at about 700 cm(-1) disappears and a new weak peak appears at about 645 cm(-1). The three new peaks are the infrared absorption features of U3O7. An absorption peak at 744 cm(-1) which is the strongest feature of alpha-U3O8 infrared spectrum appears for UO(2.39) and is

  12. Transport properties and Raman spectra of impurity substituted MgB 2

    NASA Astrophysics Data System (ADS)

    Masui, T.

    2007-06-01

    Recent advances in the study of MgB 2 are reviewed, with focus on the transport properties and Raman scattering measurements for impurity substituted crystals. Carbon and Aluminium substitution change band filling, introduce intraband and interband scattering. These effects are seen in the temperature dependence of resistivity, Hall coefficients, and phonon peak of Raman spectra. Manganese substitution introduces magnetic scattering, that increases resistivity but gives little change in Raman spectra. The effect of disorder in neutron irradiated samples is also discussed.

  13. [Reserach on Raman spectra of organic ingredients on colored pearls].

    PubMed

    Hu, Yang; Fan, Lu-Wei; Huang, Yi-Lan

    2014-01-01

    Based on the visible spectra and Raman spectra test of a variety of colored pearls samples to study the relationship between the organic component and the pearl's color was studied. The study results show that both the freshwater and seawater pearls exhibit strong characteristic peaks in 1121-1132 and 1506-1524 cm(-1) range, which is respectively attributed to the C-C and C=C stretching vibration; the peak intensity in 1117-1132, 1502-1524 and 2000-3500 cm(-1) range increases as the color deepens, which is closely related to the pearl's color; The peak in the 1475-1575 cm(-1) range is divided into 8-10 secondary peaks of purple freshwater pearl and deep orange seawater pearl. The number of C=C double bonds is N=9 approximately 27 and N=7 approximately 27 respectively after calculation. Polyene compound of different varieties and content could be the reason for the pearls' color.

  14. Spectrometer calibration protocol for Raman spectra recorded with different excitation wavelengths.

    PubMed

    Bocklitz, T W; Dörfer, T; Heinke, R; Schmitt, M; Popp, J

    2015-01-01

    The combination of Raman spectroscopy with chemometrics has gained significant importance within the last years to address a broad variety of biomedical and life science questions. However, the routine application of chemometric models to analyze Raman spectra recorded with Raman devices different from the device used to establish the model is extremely challenging due to Raman device specific influences on the recorded Raman spectra. Here we report on the influence of different non-resonant excitation wavelengths on Raman spectra and propose a calibration routine, which corrects for the main part of the spectral differences between Raman spectra recorded with different (non-resonant) excitation wavelengths. The calibration routine introduced within this contribution is an improvement to the known 'standard' calibration routines and is a starting point for the development of a calibration protocol to generate spectrometer independent Raman spectra. The presented routine ensures that a chemometric model utilizes only Raman information of the sample and not artifacts from small shifts in the excitation wavelength. This is crucial for the application of Raman-spectroscopy in real-world-settings, such as diagnostics of diseases or identification of bacteria.

  15. Evaluation of Shifted Excitation Raman Difference Spectroscopy and Comparison to Computational Background Correction Methods Applied to Biochemical Raman Spectra.

    PubMed

    Cordero, Eliana; Korinth, Florian; Stiebing, Clara; Krafft, Christoph; Schie, Iwan W; Popp, Jürgen

    2017-07-27

    Raman spectroscopy provides label-free biochemical information from tissue samples without complicated sample preparation. The clinical capability of Raman spectroscopy has been demonstrated in a wide range of in vitro and in vivo applications. However, a challenge for in vivo applications is the simultaneous excitation of auto-fluorescence in the majority of tissues of interest, such as liver, bladder, brain, and others. Raman bands are then superimposed on a fluorescence background, which can be several orders of magnitude larger than the Raman signal. To eliminate the disturbing fluorescence background, several approaches are available. Among instrumentational methods shifted excitation Raman difference spectroscopy (SERDS) has been widely applied and studied. Similarly, computational techniques, for instance extended multiplicative scatter correction (EMSC), have also been employed to remove undesired background contributions. Here, we present a theoretical and experimental evaluation and comparison of fluorescence background removal approaches for Raman spectra based on SERDS and EMSC.

  16. Evaluation of Shifted Excitation Raman Difference Spectroscopy and Comparison to Computational Background Correction Methods Applied to Biochemical Raman Spectra

    PubMed Central

    Cordero, Eliana; Korinth, Florian; Stiebing, Clara; Krafft, Christoph; Schie, Iwan W.; Popp, Jürgen

    2017-01-01

    Raman spectroscopy provides label-free biochemical information from tissue samples without complicated sample preparation. The clinical capability of Raman spectroscopy has been demonstrated in a wide range of in vitro and in vivo applications. However, a challenge for in vivo applications is the simultaneous excitation of auto-fluorescence in the majority of tissues of interest, such as liver, bladder, brain, and others. Raman bands are then superimposed on a fluorescence background, which can be several orders of magnitude larger than the Raman signal. To eliminate the disturbing fluorescence background, several approaches are available. Among instrumentational methods shifted excitation Raman difference spectroscopy (SERDS) has been widely applied and studied. Similarly, computational techniques, for instance extended multiplicative scatter correction (EMSC), have also been employed to remove undesired background contributions. Here, we present a theoretical and experimental evaluation and comparison of fluorescence background removal approaches for Raman spectra based on SERDS and EMSC. PMID:28749450

  17. A Comparison between the Raman Spectra of Ce

    SciTech Connect

    Hirata, T.; Watanabe, A.

    2001-05-01

    The Raman spectra of Ce{sub 1-x}Ca{sub x}VO{sub 4-0.5x} (0{<=}x{le}0.41) and Ce{sub 1-x}Bi{sub x}VO{sub 4} (0{<=}x{le}0.68) solid solutions, where aliovalent Ca{sup 2+} or isovalent Bi{sup 3+} cations are substituted for Ce{sup 3+} in the tetragonal cerium vanadate CeVO{sub 4}, are presented as a function of x to compare with each other. There was a remarkable difference in that the three broad features appeared in the Raman spectra of Ce{sub 1-x}Ca{sub x}VO{sub 4-0.5x} whereas they were absent for Ce{sub 1-x}Bi{sub x}VO{sub 4}. The appearance of the broad features could be attributed to the ''charge transfer'' effect on the aliovalent Ca{sup 2+} substitution, which is responsible for a substantial enhancement in electrical conductivity in Ce{sub 1-x}Ca{sub x}VO{sub 4-0.5x} relative to Ce{sub 1-x}Bi{sub x}VO{sub 4} with x. From the changes in the modes' frequency with unit-c ell volume, which exhibit a different decrease with x between Ce{sub 1-x}Ca{sub x}VO{sub 4-0.5x} and Ce{sub 1-x}Bi{sub x}VO{sub 4}, we could estimate mode Grueneisen parameters that vary in magnitude and/or sign as well as between Ce{sub 1-x}Ca{sub x}VO{sub 4-0.5x} and Ce{sub 1-x}Bi{sub x}VO{sub 4}; this reflects the fact that different lattice distortions are induced when aliovalent or isovalent cations with similar/different ionic radii are substituted to form both the solid solutions.

  18. Excited-state Raman spectroscopy with and without actinic excitation: S{sub 1} Raman spectra of trans-azobenzene

    SciTech Connect

    Dobryakov, A. L.; Quick, M.; Ioffe, I. N.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A.

    2014-05-14

    We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S{sub 1} and S{sub 0} spectra of trans-azobenzene in n-hexane. The S{sub 1} spectra were also measured conventionally, upon nπ* (S{sub 0} → S{sub 1}) actinic excitation. The results are discussed and compared to earlier reports.

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

    PubMed

    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.

  20. The minimizing of fluorescence background in Raman optical activity and Raman spectra of human blood plasma.

    PubMed

    Tatarkovič, Michal; Synytsya, Alla; Šťovíčková, Lucie; Bunganič, Bohuš; Miškovičová, Michaela; Petruželka, Luboš; Setnička, Vladimír

    2015-02-01

    Raman optical activity (ROA) is inherently sensitive to the secondary structure of biomolecules, which makes it a method of interest for finding new approaches to clinical applications based on blood plasma analysis, for instance the diagnostics of several protein-misfolding diseases. Unfortunately, real blood plasma exhibits strong background fluorescence when excited at 532 nm; hence, measuring the ROA spectra appears to be impossible. Therefore, we established a suitable method using a combination of kinetic quenchers, filtering, photobleaching, and a mathematical correction of residual fluorescence. Our method reduced the background fluorescence approximately by 90%, which allowed speedup for each measurement by an average of 50%. In addition, the signal-to-noise ratio was significantly increased, while the baseline distortion remained low. We assume that our method is suitable for the investigation of human blood plasma by ROA and may lead to the development of a new tool for clinical diagnostics.

  1. Consistency analysis of plastic samples based on similarity calculation from limited range of the Raman spectra

    NASA Astrophysics Data System (ADS)

    Lai, B. W.; Wu, Z. X.; Dong, X. P.; Lu, D.; Tao, S. C.

    2016-07-01

    We proposed a novel method to calculate the similarity between samples with only small differences at unknown and specific positions in their Raman spectra, using a moving interval window scanning across the whole Raman spectra. Two ABS plastic samples, one with and the other without flame retardant, were tested in the experiment. Unlike the traditional method in which the similarity is calculated based on the whole spectrum, we do the calculation by using a window to cut out a certain segment from Raman spectra, each at a time as the window moves across the entire spectrum range. By our method, a curve of similarity versus wave number is obtained. And the curve shows a large change where the partial spectra of the two samples is different. Thus, the new similarity calculation method identifies samples with tiny difference in their Raman spectra better.

  2. An improved algorithm to remove cosmic spikes in Raman spectra for online monitoring.

    PubMed

    Li, Sheng; Dai, Liankui

    2011-11-01

    Raman spectral analysis integrated with multivariate calibration is a fast and effective solution to monitor chemical product properties. However, Raman instruments utilizing charge-coupled device (CCD) detectors suffer from occasional spikes caused by cosmic rays. Cosmic spikes can disturb or even destroy the meaningful chemical information expressed by normal Raman spectra. In online monitoring, some cosmic spikes have intensity and bandwidth similar to normal Raman peaks of chemical components when a low resolution and cost-effective Raman instrument is used. Moreover, the online Raman spectra always contain variations of strong Raman peaks and fluorescence. Current spike-removal methods seem to have difficulty detecting and recovering cosmic spikes in these online Raman spectra. Therefore, an improved algorithm is proposed. In this algorithm, a new scheme composed of intensity identification and local moving window correlation analysis is introduced for cosmic spike detection; intensity identification based on derivative spectra and local linear fitting approximation are used for the recovery of cosmic spikes. The algorithm is proved to be simple and effective and has been applied in an online Raman instrument installed at a continuous catalytic reforming unit in a refinery.

  3. Effect of hormonal variation on in vivo high wavenumber Raman spectra improves cervical precancer detection

    NASA Astrophysics Data System (ADS)

    Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J. H.; Ilancheran, A.; Huang, Zhiwei

    2012-03-01

    Raman spectroscopy is a unique analytical probe for molecular vibration and is capable of providing specific spectroscopic fingerprints of molecular compositions and structures of biological tissues. The aim of this study is to improve the classification accuracy of cervical precancer by characterizing the variations in the normal high wavenumber (HW - 2800-3700cm-1) Raman spectra arising from the menopausal status of the cervix. A rapidacquisition near-infrared (NIR) Raman spectroscopic system was used for in vivo tissue Raman measurements at 785 nm excitation. Individual HW Raman spectrum was measured with a 5s exposure time from both normal and precancer tissue sites of 15 patients recruited. The acquired Raman spectra were stratified based on the menopausal status of the cervix before the data analysis. Significant differences were noticed in Raman intensities of prominent band at 2924 cm-1 (CH3 stretching of proteins) and the broad water Raman band (in the 3100-3700 cm-1 range) with a peak at 3390 cm-1 in normal and dysplasia cervical tissue sites. Multivariate diagnostic decision algorithm based on principal component analysis (PCA) and linear discriminant analysis (LDA) was utilized to successfully differentiate the normal and precancer cervical tissue sites. By considering the variations in the Raman spectra of normal cervix due to the hormonal or menopausal status of women, the diagnostic accuracy was improved from 71 to 91%. By incorporating these variations prior to tissue classification, we can significantly improve the accuracy of cervical precancer detection using HW Raman spectroscopy.

  4. Recovery of Raman spectra with low signal-to-noise ratio using Wiener estimation.

    PubMed

    Chen, Shuo; Lin, Xiaoqian; Yuen, Clement; Padmanabhan, Saraswathi; Beuerman, Roger W; Liu, Quan

    2014-05-19

    Raman spectroscopy is a powerful non-destructive technique for qualitatively and quantitatively characterizing materials. However, noise often obscures interesting Raman peaks due to the inherently weak Raman signal, especially in biological samples. In this study, we develop a method based on spectral reconstruction to recover Raman spectra with low signal-to-noise ratio (SNR). The synthesis of narrow-band measurements from low-SNR Raman spectra eliminates the effect of noise by integrating the Raman signal along the wavenumber dimension, which is followed by spectral reconstruction based on Wiener estimation to recover the Raman spectrum with high spectral resolution. Non-negative principal components based filters are used in the synthesis to ensure that most variance contained in the original Raman measurements are retained. A total of 25 agar phantoms and 20 bacteria samples were measured and data were used to validate our method. Four commonly used de-noising methods in Raman spectroscopy, i.e. Savitzky-Golay (SG) algorithm, finite impulse response (FIR) filtration, wavelet transform and factor analysis, were also evaluated on the same set of data in addition to the proposed method for comparison. The proposed method showed the superior accuracy in the recovery of Raman spectra from measurements with extremely low SNR, compared with the four commonly used de-noising methods.

  5. Rapid acquisition of mean Raman spectra of eukaryotic cells for a robust single cell classification.

    PubMed

    Schie, Iwan W; Kiselev, Roman; Krafft, Christoph; Popp, Jürgen

    2016-11-14

    Raman spectroscopy has previously been used to identify eukaryotic and prokaryotic cells. While prokaryotic cells are small in size and can be assessed by a single Raman spectrum, the larger size of eukaryotic cells and their complex organization requires the acquisition of multiple Raman spectra to properly characterize them. A Raman spectrum from a diffraction-limited spot at an arbitrary location within a cell results in spectral variations that affect classification approaches. To probe whole cells with Raman imaging at high spatial resolution is time consuming, because a large number of Raman spectra need to be collected, resulting in low cell throughput and impairing statistical analysis due to low cell numbers. Here we propose a method to overcome the effects of cellular heterogeneity by acquiring integrated Raman spectra covering a large portion of a cell. The acquired spectrum represents the mean macromolecular composition of a cell with an exposure time that is comparable to acquisition of a single Raman spectrum. Data sets were collected from T lymphocyte Jurkat cells, and pancreatic cell lines Capan1 and MiaPaca2. Cell classification by support vector machines was compared for single spectra, spectra of images and integrated Raman spectra of cells. The integrated approach provides better and more stable prediction for individual cells, and in the current implementation, the mean macromolecular information of a cell can be acquired faster than with the acquisition of individual spectra from a comparable region. It is expected that this approach will have a major impact on the implementation of Raman based cell classification.

  6. Raman spectra of high- κ dielectric layers investigated with micro-Raman spectroscopy comparison with silicon dioxide.

    PubMed

    Borowicz, P; Taube, A; Rzodkiewicz, W; Latek, M; Gierałtowska, S

    2013-01-01

    Three samples with dielectric layers from high- κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high- κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the structure of this material. Raman spectra recorded for as-deposited hafnium oxide are similar to the results obtained for silicon dioxide layer. After thermal treatment especially at higher temperatures (600°C and above), the structure of hafnium oxide becomes similar to the bulk non-densified silicon dioxide.

  7. Raman Spectra of High-κ Dielectric Layers Investigated with Micro-Raman Spectroscopy Comparison with Silicon Dioxide

    PubMed Central

    Borowicz, P.; Taube, A.; Rzodkiewicz, W.; Latek, M.; Gierałtowska, S.

    2013-01-01

    Three samples with dielectric layers from high-κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high-κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the structure of this material. Raman spectra recorded for as-deposited hafnium oxide are similar to the results obtained for silicon dioxide layer. After thermal treatment especially at higher temperatures (600°C and above), the structure of hafnium oxide becomes similar to the bulk non-densified silicon dioxide. PMID:24072982

  8. Raman spectra of methane, ethylene, ethane, dimethyl ether, formaldehyde and propane for combustion applications

    NASA Astrophysics Data System (ADS)

    Magnotti, G.; KC, U.; Varghese, P. L.; Barlow, R. S.

    2015-09-01

    Spontaneous Raman scattering measurements of temperature and major species concentration in hydrocarbon-air flames require detailed knowledge of the Raman spectra of the hydrocarbons present when fuels more complex than methane are used. Although hydrocarbon spectra have been extensively studied at room temperature, there are no data available at higher temperatures. Quantum mechanical calculations, when available are not sufficiently accurate for combustion applications. This work presents experimental measurements of spontaneous Stokes-Raman scattering spectra of methane, ethylene, ethane, dimethyl ether, formaldehyde and propane in the temperature range 300-860 K. Raman spectra from heated hydrocarbons jets have been collected with a higher resolution than is generally employed for Raman measurements in combustion applications. A set of synthetic spectra have been generated for each hydrocarbon, providing the basis for extrapolation to higher temperatures. The spectra provided here will enable simultaneous measurements of multiple hydrocarbons in flames. This capability will greatly extend the range of applicability of Raman measurements in combustion applications. In addition, the experimental spectra provide a validation dataset for quantum mechanical models.

  9. Background photobleaching in raman spectra of aqueous solutions of plant toxins

    NASA Astrophysics Data System (ADS)

    Brandt, Nikolai N.; Chikishev, Andrey Y.; Tonevitsky, Alexander G.

    2002-05-01

    Kinetics of background photobleaching in Raman spectra of aqueous solutions of ricin, ricin agglutinin and ricin binding subunit were measured. It was found that the spectrum of Raman background changes upon laser irradiation. Background intensity is lower for the samples with lower molecular weight. Photobleaching is characterized by oscillations in the multi exponentially decaying intensity.

  10. [Raman spectra of different kinds of thalassemia erythrocytes with the effect of pH].

    PubMed

    Wu, Zheng-Jie; Wang, Cheng; Lin, Zheng-Chun

    2013-04-01

    Thalassemia is a kind of blood diseases which has high morbidity and large influence. Previous methods for diagnosis are all very cumbersome and time consuming. By comparing Raman spectra of different kinds of thalassemia and normal erythrocytes at acid or alkaline pH, it was found that beta-thalassemia and alpha-thalassemia erythrocytes have dissimilar Raman spectra in the acidic environment, such as the Raman spectra of beta-thalassemia erythrocytes showed higher intensity at the characteristic bands assigned to oxyhemoglobin, and the characteristic bands assigned to deoxyhemoglobin were even completely replaced; beta-thalassemia erythrocytes membrane has a smaller chain interaction between the transverse order parameters than normal erythrocytes, and the S(lat) values are different for different stages of anemia, while the S(lat) values are similar between alpha-thalassemia and normal erythrocytes, indicating that based on the effect of pH it is possible to diagnose thalassemia more quickly by using Raman spectra.

  11. Resonance Raman spectra of the anion and cation radicals of bacterial photosynthetic pigments

    SciTech Connect

    Diers, J.R.; Bocian, D.F. )

    1994-12-08

    Resonance Raman (RR) spectra are reported for the radical ions of the bacterial photosynthetic pigments bacteriochlorophyll a (BCh) and its metal-free analog bacteriopheophytin a (BPh). The radical anions, BCh[sup [minus

  12. Effect of Grain Size and Grain Orientation on the Raman Spectra of Minerals

    NASA Technical Reports Server (NTRS)

    Sharma, S. K.; Chio, C. H.; Deb, P.; Lucey, P. G.; Domergue-Schmidt, N.; Horton, K. A.

    2000-01-01

    We have examined effects of grain size and grain orientation on the Raman spectra of quartz and olivine to evaluate the effect of these parameters on in situ and remote analysis of planetary surface rocks.

  13. Infrared absorption and Raman scattering spectra of water under pressure via first principles molecular dynamics.

    PubMed

    Ikeda, Takashi

    2014-07-28

    From both the polarized and depolarized Raman scattering spectra of supercritical water a peak located at around 1600 cm(-1), attributed normally to bending mode of water molecules, was experimentally observed to vanish, whereas the corresponding peak remains clearly visible in the measured infrared (IR) absorption spectrum. In this computational study a theoretical formulation for analyzing the IR and Raman spectra is developed via first principles molecular dynamics combined with the modern polarization theory. We demonstrate that the experimentally observed peculiar behavior of the IR and Raman spectra for water are well reproduced in our computational scheme. We discuss the origins of a feature observed at 1600 cm(-1) in Raman spectra of ambient water.

  14. Surface-enhanced resonance hyper-Raman spectra of bacteriorhodopsin adsorbed on silver colloids

    NASA Astrophysics Data System (ADS)

    Baranov, A. V.; Nabiev, Igor R.

    1991-05-01

    Surface-enhanced resonance hyper-Raman scattering (SERHRS) spectra of bacteriorhodopsin (BRh) located in purple membranes of Halobacterium halobium adsorbed on aggregated hydrosol Ag particles are obtained for the first time. The SERIIR spectra excited by pulse 1064 nm radiation are compared with SERR spectra excited by radiation with doubled frequency (532 nm). The bands corresponding to the BRh57O and M412 forms of Brh are observed in both spectra. The relative intensities of these bands are discussed. 1.

  15. Evaluation of Raman spectra of human brain tumor tissue using the learning vector quantization neural network

    NASA Astrophysics Data System (ADS)

    Liu, Tuo; Chen, Changshui; Shi, Xingzhe; Liu, Chengyong

    2016-05-01

    The Raman spectra of tissue of 20 brain tumor patients was recorded using a confocal microlaser Raman spectroscope with 785 nm excitation in vitro. A total of 133 spectra were investigated. Spectra peaks from normal white matter tissue and tumor tissue were analyzed. Algorithms, such as principal component analysis, linear discriminant analysis, and the support vector machine, are commonly used to analyze spectral data. However, in this study, we employed the learning vector quantization (LVQ) neural network, which is typically used for pattern recognition. By applying the proposed method, a normal diagnosis accuracy of 85.7% and a glioma diagnosis accuracy of 89.5% were achieved. The LVQ neural network is a recent approach to excavating Raman spectra information. Moreover, it is fast and convenient, does not require the spectra peak counterpart, and achieves a relatively high accuracy. It can be used in brain tumor prognostics and in helping to optimize the cutting margins of gliomas.

  16. A study of aliphatic amino acids using simulated vibrational circular dichroism and Raman optical activity spectra*

    NASA Astrophysics Data System (ADS)

    Ganesan, Aravindhan; Brunger, Michael J.; Wang, Feng

    2013-11-01

    Vibrational optical activity (VOA) spectra, such as vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra, of aliphatic amino acids are simulated using density functional theory (DFT) methods in both gas phase (neutral form) and solution (zwitterionic form), together with their respective infrared (IR) and Raman spectra of the amino acids. The DFT models, which are validated by excellent agreements with the available experimental Raman and ROA spectra of alanine in solution, are employed to study other aliphatic amino acids. The inferred (IR) intensive region (below 2000 cm-1) reveals the signature of alkyl side chains, whereas the Raman intensive region (above 3000 cm-1) contains the information of the functional groups in the amino acids. Furthermore, the chiral carbons of the amino acids (except for glycine) dominate the VCD and ROA spectra in the gas phase, but the methyl group vibrations produce stronger VCD and ROA signals in solution. The C-H related asymmetric vibrations dominate the VOA spectra (i.e., VCD and ROA) > 3000 cm-1 reflecting the side chain structures of the amino acids. Finally the carboxyl and the C(2)H modes of aliphatic amino acids, together with the side chain vibrations, are very active in the VCD/IR and ROA/Raman spectra, which makes such the vibrational spectroscopic methods a very attractive means to study biomolecules.

  17. Laser-induced alteration of Raman spectra for micron-sized solid particles

    NASA Astrophysics Data System (ADS)

    Böttger, U.; Pavlov, S. G.; Deßmann, N.; Hanke, F.; Weber, I.; Fritz, J.; Hübers, H.-W.

    2017-04-01

    The Raman Laser Spectrometer (RLS) instrument on board of the future ESAs ExoMars mission will analyze micron-sized powder samples in a low pressure atmosphere. Such micron-sized polycrystalline solid particles might be heated by the laser during the Raman measurements. Here, we report on the temperature-induced alteration of Raman spectra from micron-sized polycrystalline solid particles by comparing Raman spectra on silicon and the rock forming minerals olivine and pyroxene taken at different laser intensities and different ambient temperatures. Our analyses indicate that laser-induced heating results in both broadening and shifting of characteristic Raman lines in the Stokes and anti-Stokes spectral regions. For elementary crystalline silicon a significant local temperature increase and relevant changes in Raman spectra have been observed in particles with median sizes below 250 μm. In comparison, significantly weaker laser-induced Raman spectral changes were observed in more complex rock-forming silicate minerals; even for lower grain sizes. Laser power densities realized in the RLS ExoMars instrument should cause only low local heating effects and, thus, negligible frequency shifts of the major Raman lines in common silicate minerals such as olivine and pyroxene.

  18. Combined quantum mechanics (TDDFT) and classical electrodynamics (Mie theory) methods for calculating surface enhanced Raman and hyper-Raman spectra.

    PubMed

    Mullin, Jonathan; Valley, Nicholas; Blaber, Martin G; Schatz, George C

    2012-09-27

    Multiscale models that combine quantum mechanics and classical electrodynamics are presented, which allow for the evaluation of surface-enhanced Raman (SERS) and hyper-Raman scattering spectra (SEHRS) for both chemical (CHEM) and electrodynamic (EM) enhancement mechanisms. In these models, time-dependent density functional theory (TDDFT) for a system consisting of the adsorbed molecule and a metal cluster fragment of the metal particle is coupled to Mie theory for the metal particle, with the surface of the cluster being overlaid with the surface of the metal particle. In model A, the electromagnetic enhancement from plasmon-excitation of the metal particle is combined with the chemical enhancement associated with a static treatment of the molecule-metal structure to determine overall spectra. In model B, the frequency dependence of the Raman spectrum of the isolated molecule is combined with the enhancements determined in model A to refine the enhancement estimate. An equivalent theory at the level of model A is developed for hyper-Raman spectra calculations. Application to pyridine interacting with a 20 nm diameter silver sphere is presented, including comparisons with an earlier model (denoted G), which combines plasmon enhanced fields with gas-phase Raman (or hyper-Raman) spectra. The EM enhancement factor for spherical particles at 357 nm is found to be 10(4) and 10(6) for SERS and SEHRS, respectively. Including both chemical and electromagnetic mechanisms at the level of model A leads to enhancements on the order of 10(4) and 10(9) for SERS and SEHRS.

  19. Analytic calculations of hyper-Raman spectra from density functional theory hyperpolarizability gradients

    NASA Astrophysics Data System (ADS)

    Ringholm, Magnus; Bast, Radovan; Oggioni, Luca; Ekström, Ulf; Ruud, Kenneth

    2014-10-01

    We present the first analytic calculations of the geometrical gradients of the first hyperpolarizability tensors at the density-functional theory (DFT) level. We use the analytically calculated hyperpolarizability gradients to explore the importance of electron correlation effects, as described by DFT, on hyper-Raman spectra. In particular, we calculate the hyper-Raman spectra of the all-trans and 11-cis isomers of retinal at the Hartree-Fock (HF) and density-functional levels of theory, also allowing us to explore the sensitivity of the hyper-Raman spectra on the geometrical characteristics of these structurally related molecules. We show that the HF results, using B3LYP-calculated vibrational frequencies and force fields, reproduce the experimental data for all-trans-retinal well, and that electron correlation effects are of minor importance for the hyper-Raman intensities.

  20. Analytic calculations of hyper-Raman spectra from density functional theory hyperpolarizability gradients

    SciTech Connect

    Ringholm, Magnus; Ruud, Kenneth; Bast, Radovan; Oggioni, Luca; Ekström, Ulf

    2014-10-07

    We present the first analytic calculations of the geometrical gradients of the first hyperpolarizability tensors at the density-functional theory (DFT) level. We use the analytically calculated hyperpolarizability gradients to explore the importance of electron correlation effects, as described by DFT, on hyper-Raman spectra. In particular, we calculate the hyper-Raman spectra of the all-trans and 11-cis isomers of retinal at the Hartree-Fock (HF) and density-functional levels of theory, also allowing us to explore the sensitivity of the hyper-Raman spectra on the geometrical characteristics of these structurally related molecules. We show that the HF results, using B3LYP-calculated vibrational frequencies and force fields, reproduce the experimental data for all-trans-retinal well, and that electron correlation effects are of minor importance for the hyper-Raman intensities.

  1. Analytic calculations of hyper-Raman spectra from density functional theory hyperpolarizability gradients.

    PubMed

    Ringholm, Magnus; Bast, Radovan; Oggioni, Luca; Ekström, Ulf; Ruud, Kenneth

    2014-10-07

    We present the first analytic calculations of the geometrical gradients of the first hyperpolarizability tensors at the density-functional theory (DFT) level. We use the analytically calculated hyperpolarizability gradients to explore the importance of electron correlation effects, as described by DFT, on hyper-Raman spectra. In particular, we calculate the hyper-Raman spectra of the all-trans and 11-cis isomers of retinal at the Hartree-Fock (HF) and density-functional levels of theory, also allowing us to explore the sensitivity of the hyper-Raman spectra on the geometrical characteristics of these structurally related molecules. We show that the HF results, using B3LYP-calculated vibrational frequencies and force fields, reproduce the experimental data for all-trans-retinal well, and that electron correlation effects are of minor importance for the hyper-Raman intensities.

  2. Real-Time Analysis of Raman Spectra for Temperature Field Characterization in Aircraft Exhaust Noise Studies

    NASA Astrophysics Data System (ADS)

    Wormhoudt, J.; Nelson, D. D.; Annen, K.; Locke, R. J.; Wernet, M.

    2009-06-01

    Raman scattering has long been used as a non-intrusive diagnostic of temperatures in combustion exhaust flows, using a variety of spectral analysis techniques. As part of their ongoing program of experiments to support development of computer codes that calculate exhaust flow fields and predict jet noise, NASA Glenn Research Center is developing a laser Raman diagnostic system that will measure mean temperatures and temperature fluctuations in hot and cold jet flows. We describe a software package, ART (Analysis for Raman Temperatures), that analyzes Raman spectra of air for temperature and density using vibrational or resolved or unresolved rotational bands, presenting results in a variety of real-time displays. Each analysis technique presents its own challenges in obtaining the most precise and accurate values, and we will comment on these issues by exhibiting example spectra of each type. The ART program is closely related to another Aerodyne software package (TDLWintel) which automates the acquisition and analysis of tunable laser absorption spectra.

  3. Standardization of Raman spectra for transfer of spectral libraries across different instruments.

    PubMed

    Rodriguez, Jason D; Westenberger, Benjamin J; Buhse, Lucinda F; Kauffman, John F

    2011-10-21

    In this paper we evaluate methods for standardization of Raman spectra that are required to improve spectral correlation computations between spectra measured on different instruments. Five commercially-available 785 nm Raman spectrometers from different vendors were included in the study. These spectrometers have diverse specifications and performance levels and range in size from laboratory-based instruments to field-deployable portable and handheld platforms. Since each Raman spectrometer has different characteristics, spectra obtained on one instrument cannot readily be compared to a library acquired on a different instrument without performing various types of spectral corrections (standardization). We outline a procedure that combines previously established Raman shift and intensity correction protocols with a resolution matching step to facilitate the comparison of a centralized master library with spectra acquired on different geographically distributed Raman spectrometers. The standardization procedure is effective in reducing the inherent instrument-to-instrument variability so that spectra from different spectrometers can be compared and reliable results obtained using library-based spectral correlation methods. The findings have important implications for the ability to transfer Raman spectral libraries between instruments.

  4. Method for automatically identifying spectra of different wood cell wall layers in Raman imaging data set.

    PubMed

    Zhang, Xun; Ji, Zhe; Zhou, Xia; Ma, Jian-Feng; Hu, Ya-Hong; Xu, Feng

    2015-01-20

    The technique of Raman spectroscopic imaging is finding ever-increasing applications in the field of wood science for its ability to provide spatial and spectral information about the sample. On the basis of the acquired Raman imaging data set, it is possible to determine the distribution of chemical components in various wood cell wall layers. However, the Raman imaging data set often contains thousands of spectra measured at hundreds or even thousands of individual frequencies, which results in difficulties accurately and quickly extracting all of the spectra within a specific morphological region of wood cell walls. To address this issue, the authors propose a new method to automatically identify Raman spectra of different cell wall layers on the basis of principal component analysis (PCA) and cluster analysis. A Raman imaging data set collected from a 55.5 μm × 47.5 μm cross-section of poplar tension wood was analyzed. Several thousand spectra were successfully classified into five groups in accordance with different morphological regions, namely, cell corner (CC), compound middle lamella (CML), secondary wall (SW), gelatinous layer (G-layer), and cell lumen. Their corresponding average spectra were also calculated. In addition, the relationship between different characteristic peaks in the obtained Raman spectra was estimated and it was found that the peak at 1331 cm(-1) is more related to lignin rather than cellulose. Not only can this novel method provide a convenient and accurate procedure for identifying the spectra of different cell wall layers in a Raman imaging data set, but it also can bring new insights into studying the morphology and topochemistry in wood cell walls.

  5. Hydrogen bonding effects on infrared and Raman spectra of drug molecules

    NASA Astrophysics Data System (ADS)

    Bondesson, Laban; Mikkelsen, Kurt V.; Luo, Yi; Garberg, Per; Ågren, Hans

    2007-02-01

    Infrared and Raman spectra of three drug molecules, aspirin, caffeine and ibuprofen, in gas phase and in aqueous solution have been simulated using hybrid density functional theory. The long range solvent effect is modelled by the polarizable continuum model, while the short range hydrogen bonding effects are taken care of by the super-molecular approach with explicit inclusion of water molecules. The calculated spectra are found to compare well with available experimental results. The agreement obtained make grounds for proposing theoretical modeling as a tool for characterizing changes in the bonding environments of drug molecules in terms of particular variations in their IR and Raman spectra.

  6. Interpretation of the resonance Raman spectra of linear tetrapyrroles based on DFT calculations

    NASA Astrophysics Data System (ADS)

    Kneip, Christa; Hildebrandt, Peter; Németh, Károly; Mark, Franz; Schaffner, Kurt

    1999-10-01

    Raman spectra of linear methine-bridged tetrapyrroles in different conformational and protonation states were calculated on the basis of scaled force fields obtained by density functional theory. Results are reported for protonated phycocyanobilin in the extended ZZZasa configuration, as it is found in C-phycocyanin of cyanobacteria. The calculated spectra are in good agreement with experimental spectra of the protein-bound chromophore in the α-subunit of C-phycocyanin and allow a plausible and consistent assignment of most of the observed resonance Raman bands in the region between 1000 and 1700 cm -1.

  7. Raman spectra of ammonia borane: low frequency lattice modes.

    PubMed

    Ziparo, C; Colognesi, D; Giannasi, A; Zoppi, M

    2012-09-06

    We have measured the Raman spectrum of ammonia borane at low temperature (T = 15 K) and across the orthorhombic-to-tetragonal phase transition at T = 225 K. A comprehensive study of the low frequency lattice modes using Raman spectroscopy has been carried out. Data analysis has been complemented by a density functional theory calculation of which the results have been used for a detailed assignment of the Raman active modes. The analysis of the spectroscopic measurements taken across the phase transition seems to be consistent with the increasing orientational disorder of the molecular components and seems to be compatible with the equalization of the a and b lattice constants characteristic of the tetragonal phase.

  8. Raman spectra of gaseous and solid N2F4

    NASA Technical Reports Server (NTRS)

    Durig, J. R.; Macnamee, R. W.

    1974-01-01

    The Raman spectrum of gaseous N2F4 at a pressure of 760 Torr was recorded with a spectral slit width of 3 kaysers. Ten of the expected eleven fundamentals of the symmetric motions of both the gauche and trans isomers give rise to strongly polarized Raman lines. These new data require a reassignment of some of the fundamentals for both the C2 and C2h conformers. The Raman of the solid at 18 K was also recorded. Both conformers were found in the solid even after annealing the sample for 9 hr at a temperature of 101.6 K and 3 hr at a temperature of 106.8 K. Bands attributable to the gauche isomer became more intense relative to those for the trans isomer after several hours of annealing.

  9. Pollen Raman spectra database: application to the identification of airborne pollen.

    PubMed

    Guedes, A; Ribeiro, H; Fernández-González, M; Aira, M J; Abreu, I

    2014-02-01

    Raman microspectroscopy allows a non-destructive identification of airborne particles. However, the identification of particles such as pollen is hindered by the absence of a spectral library. Although reference spectra of pollen have been published before, they have always been limited to a certain number of species. In this work, Raman spectra of 34 pollen types are presented and were used to build a pollen spectra primary library. Afterward, the applicability of this database for detecting and identifying pollen in airborne samples was tested. Airborne pollen samples collected during April, May and August were compared with blank pollen spectra by means of Hit Quality Index. Although a much larger library would be required, our results showed that all first hits correspond to the same blank pollen species of the questioned sample from the air. This possibility is an innovative idea and a promising line of investigation for future RAMAN technology development in the area of aerobiology.

  10. Surface-Enhanced Hyper-Raman Spectra of Adenine, Guanine, Cytosine, Thymine, and Uracil

    PubMed Central

    2016-01-01

    Using picosecond excitation at 1064 nm, surface-enhanced hyper-Raman scattering (SEHRS) spectra of the nucleobases adenine, guanine, cytosine, thymine, and uracil with two different types of silver nanoparticles were obtained. Comparing the SEHRS spectra with SERS data from the identical samples excited at 532 nm and with known infrared spectra, the major bands in the spectra are assigned. Due to the different selection rules for the one- and two-photon excited Raman scattering, we observe strong variation in relative signal strengths of many molecular vibrations obtained in SEHRS and SERS spectra. The two-photon excited spectra of the nucleobases are found to be very sensitive with respect to molecule–nanoparticle interactions. Using both the SEHRS and SERS data, a comprehensive vibrational characterization of the interaction of nucleobases with silver nanostructures can be achieved. PMID:28077982

  11. Raman spectra of normal and cancerous mouse mammary gland tissue using near infrared excitation energy

    NASA Astrophysics Data System (ADS)

    Naik, Vaman; Serhatkulu, G. K.; Dai, H.; Shukla, N.; Weber, R.; Thakur, J. S.; Freeman, D. C.; Pandya, A. K.; Auner, G. W.; Naik, R.; Miller, R. F.; Cao, A.; Klein, M. D.; Rabah, R.

    2006-03-01

    Raman spectra of normal mammary gland tissues, malignant mammary gland tumors, and lymph nodes have been recorded using fresh tissue from mice. Tumors were induced in mice by subcutaneously injecting 4T1 BALB/c mammary tumor (a highly malignant) cell line. The Raman spectra were collected using the same tissues that were examined by histopathology for determining the cancerous/normal state of the tissue. Differences in various peak intensities, peak shifts and peak ratios were analyzed to determine the Raman spectral features that differentiate mammary gland tumors from non-tumorous tissue. Tissues that were confirmed by pathology as cancerous (tumors) show several distinctive features in the Raman spectra compared to the spectra of the normal tissues. For example, the cancerous tissues show Raman peaks at 621, 642, 1004, 1032, 1175 and 1208 cm-1 that are assignable to amino acids containing aromatic side-chains such as phenylalanine, tryptophan and tyrosine. Further, the cancerous tissues show a greatly reduced level of phospholipids compared to the normal tissues. The Raman spectral regions that are sensitive to pathologic alteration in the tissue will be discussed.

  12. How to make Raman-inactive helium visible in Raman spectra of tritium-helium gas mixtures

    SciTech Connect

    Schloesser, M.; Pakari, O.; Rupp, S.; Mirz, S.; Fischer, S.

    2015-03-15

    Raman spectroscopy, a powerful method for the quantitative compositional analysis of molecular gases, e.g. mixtures of hydrogen isotopologues, is not able to detect monoatomic species like helium. This deficit can be overcome by using radioluminescence emission from helium atoms induced by β-electrons from tritium decay. We present theoretical considerations and combined Raman/radioluminescence spectra. Furthermore, we discuss the linearity of the method together with validation measurements for determining the pressure dependence. Finally, we conclude how this technique can be used for samples of helium with traces of tritium, and vice versa. (authors)

  13. Generation of simplified protein Raman spectra using three-color picosecond coherent anti-stokes Raman spectroscopy.

    PubMed

    Donaldson, Paul M; Willison, Keith R; Klug, David R

    2010-09-23

    The well-known and prominent marker bands of aromatic amino acids in Raman spectra of protein and peptide films are revisited in the frequency and time domains using three-color picosecond coherent anti-Stokes Raman spectroscopy (CARS). We show here that control of the probe delay allows the narrow width/long lifetime states to be observed free not only from nonresonant background and fluorescence contamination but also free from the spectral congestion that arises from the complex background of spectrally broader (shorter lifetime) vibrational modes. The reasonable limits of detection obtained indicate that such CARS methods may be useful for quantitative analysis of protein composition.

  14. FT-raman spectra of the border of infiltrating ductal carcinoma lesions.

    PubMed

    de Miranda Marzullo, Ana Carolina; Neto, Osmar Pinto; Bitar, Renata Andrade; da Silva Martinho, Herculano; Martin, Airton Abrahão

    2007-10-01

    The characterization of the FT-Raman spectra of the borders of lesions is of great importance in guiding the surgeon during surgical intervention. The main goals of this study were to investigate spectra of the borders of lesions of samples of infiltrating ductal carcinoma (IDC) and to determine the characteristics of these spectra. A total of 93 spectra were collected from five samples of healthy tissues and from 13 samples of IDC breast tissues using FT-Raman spectroscopy. Cluster analysis was used to separate the spectra into different groups. The results obtained from the statistical analysis were confirmed by a histopathological analysis. The results showed that 17 out of the 67 spectra collected from the IDC samples demonstrated wide variety. The only significant difference between the peaks of the spectra of normal tissues and those of lesion borders is a peak at 538 cm(1) . This peak is related to disulfide bridges in cysteine, and it seems to be the main factor for the FT-Raman determination of the boundaries between healthy and pathological tissue. These results serve as a foundation for future studies and application of Raman spectroscopy for optical diagnosis to guide biopsy and surgical intervention.

  15. Raman spectra of heterogeneous nanostructures based on organosilicon films

    NASA Astrophysics Data System (ADS)

    Vlasukova, L. A.; Komarov, F. F.; Leontyev, A. V.; Parkhomenko, I. N.

    2013-01-01

    We studied the effect of ion bombardment on the structure of SOG (spin-on-glass) films. We used IR and Raman spectroscopy and plan-view transmission electron microscopy to study the characteristic features of the structural transformation in organosilicon films when bombarded by nitrogen ions. We show that they are heterogeneous and we establish the presence of inclusions of nanocrystalline graphite.

  16. Models and methods for quantitative analysis of surface-enhanced Raman spectra.

    PubMed

    Li, Shuo; Nyagilo, James O; Dave, Digant P; Gao, Jean

    2014-03-01

    The quantitative analysis of surface-enhanced Raman spectra using scattering nanoparticles has shown the potential and promising applications in in vivo molecular imaging. The diverse approaches have been used for quantitative analysis of Raman pectra information, which can be categorized as direct classical least squares models, full spectrum multivariate calibration models, selected multivariate calibration models, and latent variable regression (LVR) models. However, the working principle of these methods in the Raman spectra application remains poorly understood and a clear picture of the overall performance of each model is missing. Based on the characteristics of the Raman spectra, in this paper, we first provide the theoretical foundation of the aforementioned commonly used models and show why the LVR models are more suitable for quantitative analysis of the Raman spectra. Then, we demonstrate the fundamental connections and differences between different LVR methods, such as principal component regression, reduced-rank regression, partial least square regression (PLSR), canonical correlation regression, and robust canonical analysis, by comparing their objective functions and constraints.We further prove that PLSR is literally a blend of multivariate calibration and feature extraction model that relates concentrations of nanotags to spectrum intensity. These features (a.k.a. latent variables) satisfy two purposes: the best representation of the predictor matrix and correlation with the response matrix. These illustrations give a new understanding of the traditional PLSR and explain why PLSR exceeds other methods in quantitative analysis of the Raman spectra problem. In the end, all the methods are tested on the Raman spectra datasets with different evaluation criteria to evaluate their performance.

  17. Infrared and Raman spectra of silica polymorphs from an ab initio parametrized polarizable force field.

    PubMed

    Liang, Yunfeng; Miranda, Caetano R; Scandolo, Sandro

    2006-11-21

    The general aim of this study is to test the reliability of polarizable model potentials for the prediction of vibrational (infrared and Raman) spectra in highly anharmonic systems such as high temperature crystalline phases. By using an ab initio parametrized interatomic potential for SiO2 and molecular dynamics simulations, we calculate the infrared and Raman spectra for quartz, cristobalite, and stishovite at various thermodynamic conditions. The model is found to perform very well in the prediction of infrared spectra. Raman peak positions are also reproduced very well by the model; however, Raman intensities calculated by explicitly taking the derivative of the polarizability with respect to the atomic displacements are found to be in poorer agreement than intensities calculated using a parametrized "bond polarizability" model. Calculated spectra for the high temperature beta phases, where the role of dynamical disorder and anharmonicities is predominant, are found to be in excellent agreement with experiments. For the octahedral phases, our simulations are able to reproduce changes in the Raman spectra across the rutile-to-CaCl2 transition around 50 GPa, including the observed phonon softening.

  18. Raman spectra of out-of-plane phonons in bilayer graphene

    NASA Astrophysics Data System (ADS)

    Sato, Kentaro; Park, Jin Sung; Saito, Riichiro; Cong, Chunxiao; Yu, Ting; Lui, Chun Hung; Heinz, Tony F.; Dresselhaus, Gene; Dresselhaus, Mildred S.

    2011-07-01

    The double resonance Raman spectra of the overtone of the out-of-plane tangential optical (oTO) phonon and of combinations of the LO, ZO, and ZA phonons with one another are calculated for bilayer graphene. In the case of the bilayer graphene, these Raman peaks are observed in the energy region between 1600 and 1800 cm-1. We obtain results for both the fixed q=0 and the dispersive q=2k peaks of the overtones of the oTO phonon of bilayer graphene. We calculate the double resonance Raman spectra of the combination modes coming from the LO, iTO, LA, and iTA phonons in bilayer graphene. The calculated Raman peaks are compared with the experimental results.

  19. Contrastive analysis of the Raman spectra of polychlorinated benzene: hexachlorobenzene and benzene.

    PubMed

    Zhang, Xian; Zhou, Qin; Huang, Yu; Li, Zhengcao; Zhang, Zhengjun

    2011-01-01

    Detection of persistent pollutants such as polychlorinated benzene in environment in trace amounts is challenging, but important. It is more difficult to distinguish homologues and isomers of organic pollutantd when present in trace amounts because of their similar physical and chemical properties. In this work we simulate the Raman spectra of hexachlorobenzene and benzene, and figure out the vibration mode of each main peak. The effect on the Raman spectrum of changing substituents from H to Cl is analyzed to reveal the relations between the Raman spectra of homologues and isomers of polychlorinated benzene, which should be helpful for distinguishing one kind of polychlorinated benzene from its homologues and isomers by surface enhanced Raman scattering.

  20. Acquisition of Raman spectra of amino acids using portable instruments: outdoor measurements and comparison.

    PubMed

    Culka, A; Jehlička, J; Edwards, H G M

    2010-12-01

    Raman spectra of 13 amino acids: L-alanine, β-alanine, L-asparagine, L-aspartic acid, L-glutamic acid, L-glutamine, glycine, L-methionine, L-proline, L-serine, L-threonine, L-tryptophan and L-tyrosine were acquired outdoors using two portable Raman instruments from the Ahura and Delta Nu manufacturers, both with 785 nm laser excitation. Both instruments provide quality Raman spectra with nevertheless a variable dependence upon the prevailing experimental conditions. The data acquired in these experiments will inform the selection of suitable Raman spectrometers for the in-field detection of biomolecules of relevance to the search for life signatures spectroscopically in terrestrial extreme environments and in extraterrestrial exploration, especially of planetary surfaces and subsurfaces using robotic instrumentation. Copyright © 2010 Elsevier B.V. All rights reserved.

  1. Contrastive Analysis of the Raman Spectra of Polychlorinated Benzene: Hexachlorobenzene and Benzene

    PubMed Central

    Zhang, Xian; Zhou, Qin; Huang, Yu; Li, Zhengcao; Zhang, Zhengjun

    2011-01-01

    Detection of persistent pollutants such as polychlorinated benzene in environment in trace amounts is challenging, but important. It is more difficult to distinguish homologues and isomers of organic pollutantd when present in trace amounts because of their similar physical and chemical properties. In this work we simulate the Raman spectra of hexachlorobenzene and benzene, and figure out the vibration mode of each main peak. The effect on the Raman spectrum of changing substituents from H to Cl is analyzed to reveal the relations between the Raman spectra of homologues and isomers of polychlorinated benzene, which should be helpful for distinguishing one kind of polychlorinated benzene from its homologues and isomers by surface enhanced Raman scattering. PMID:22247678

  2. First-principles calculations of Raman spectra in Li-doped Si nanocrystals

    NASA Astrophysics Data System (ADS)

    Scott Bobbitt, N.; Chelikowsky, James R.

    2016-02-01

    We examine the vibrational and Raman spectra for Li doped Si nanocrystals using real-space pseudopotentials constructed within density functional theory. We calculate differences in the Raman spectra using the Placzek approximation. The insertion of Li atoms into Si nanocrystals disrupts the Si crystal structure forming a region of Li-Si alloy in which the regular crystal structure is significantly disrupted. The Raman spectrum for this alloy exhibits a Li induced peak at 440-480 cm-1. We find an accompanying reduction in the size of the dominant bulk-like Si peak at 520 cm-1. Both of these results are consistent with experiment. Our analysis of the calculated spectrum confirms the utility of using Raman spectroscopy, coupled with first principle computations, to predict the structural and electronic properties of Li doped Si nanocrystals.

  3. Fourier-transform Raman spectra of ivory III: identification of mammalian specimens

    NASA Astrophysics Data System (ADS)

    Edwards, H. G. M.; Farwell, D. W.; Holder, J. M.; Lawson, E. E.

    1997-11-01

    The FT-Raman spectra of six mammalian ivories, other than elephant and mammoth, are presented and spectral differences formulated into a protocol for the identification of animal species from the ivory samples. In this study, sperm whale, walrus, wart hog, narwhal, hippopotamus and domestic pig are considered. The results, which are obtained non-destructively from a variety of specimens, suggest that FT-Raman spectroscopy provides a potentially useful method for the identification of mammalian ivory.

  4. Pre-resonance Raman spectra of some simple gases. [sulfur oxides, hydrogen sulfide, and nitrogen oxides

    NASA Technical Reports Server (NTRS)

    Low, P. W.

    1974-01-01

    The pre-resonance Raman spectra of SO2, N2O, and H2S were investigated using the 4880 A, 4727 A, and 4579 A lines of the argon ion laser. Although these molecules have electronic absorption bands in the near ultraviolet, none exhibit any pre-resonance enhancement within our experimental error of + or - 10%. Possible explanations taking into account the current theories for resonance Raman are discussed.

  5. Fourier-transform Raman spectra of ivory. III: Identification of mammalian specimens.

    PubMed

    Edwards, H G; Farwell, D W; Holder, J M; Lawson, E E

    1997-11-01

    The FT-Raman spectra of six mammalian ivories, other than elephant and mammoth, are presented and spectral differences formulated into a protocol for the identification of animal species from the ivory samples. In this study, sperm whale, walrus, wart hog, narwhal, hippopotamus and domestic pig are considered. The results, which are obtained non-destructively from a variety of specimens, suggest that FT-Raman spectroscopy provides a potentially useful method for the identification of mammalian ivory.

  6. [Raman spectra of PAN-based carbon fibers during surface treatment].

    PubMed

    Cao, Wei-wei; Zhu, Bo; Jing, Min; Wang, Cheng-guo

    2008-12-01

    Laser Raman spectroscopy was employed to characterize the microstructure changes of PAN based carbon fibers among different surface treatments, and the characteristics of first-order Raman spectra of carbon fibers during surface treatment were investigated in the present paper. The results show that the variety of carbon fibers' phase structures can be represented by Raman spectroscopy parameters, such as the Raman frequency shifts of main D and G bands, FWHMs and additive bands' area ratios at the positions of different Raman frequency shifts. During different surface treatment, some changes in the first-order Raman spectroscopy parameters of PAN based carbon fibers were observed, the Raman frequency shifts of D and G bands moved toward higher wavenumber, and the values of R(I(D)/I(G)) also improved, which can be used to measure the graphite crystallite size of carbon fiber. It is suggested that the graphite microstructure of carbon fibers is decomposed during surface treatment, the crystallite size is reduced, and the activity of the graphite crystallite boundary is improved. Moreover, the full-widths at half maximum (FWHM) of D and G bands both decrease, which can give information on the order of graphite microstructure and the quantity of defects in carbon fibers, and the relative bands' areas of A and D" bands also decrease, which can be attributed to the structure of amorphous carbon or some kinds of organic functional groups in carbon fibers. These differences among the spectra demonstrate that the structure of amorphous carbon in carbon fibers is easier to oxidize or decompose than multilayer graphite structure, so the relative proportion of amorphous carbon decreases during surface treatment. The conclusions obtained by Raman spectra are basically in agreement with the improvement of apparent crystallization degrees of carbon fibers during surface treatment, which were calculated by X-ray diffraction method. So the variety rules of carbon fibers' phase

  7. Structure, IR and Raman spectra of phosphotrihydrazide studied by DFT.

    PubMed

    Furer, V L; Vandyukov, A E; Majoral, J P; Caminade, A M; Kovalenko, V I

    2016-09-05

    The FTIR and FT Raman measurements of the phosphotrihydrazide (S)P[N(Me)-NH2]3 have been performed. This compound is a zero generation dendrimer G0 with terminal amine groups. Structural optimization and normal mode analysis were obtained for G0 by the density functional theory (DFT). Optimized geometric bond length and angles obtained by DFT show good agreement with experiment. The amine terminal groups are characterized by the well-defined bands at 3321, 3238, 1614cm(-1) in the experimental IR spectrum and by bands at 3327, 3241cm(-1) in the Raman spectrum of G0. The experimental frequencies of asymmetric and symmetric NH2 stretching vibrations of amine group are lower than theoretical values due to intramolecular NH⋯S hydrogen bond. This hydrogen bond is also responsible for higher experimental infrared intensity of these bands as compared with theoretical values. Relying on DFT calculations a complete vibrational assignment is proposed for the studied dendrimer.

  8. Simulation of the resonance Raman spectra for 5-halogenated (F, Cl, and Br) uracils.

    PubMed

    Sun, Shuai; Brown, Alex

    2015-04-30

    The resonance Raman spectra of the 5-halogenated (F, Cl, and Br) uracils are simulated via the Herzberg-Teller (HT) short-time dynamics formalism. The gradient of the S1 excited state is computed at the CAMB3LYP/aug-cc-pVTZ level of theory in the conductor-like polarizable continuum model for water (C-PCM, H2O), based on the equilibrium geometry determined using PBE0/aug-cc-pVTZ in H2O (C-PCM). The simulated resonance Raman spectra show good agreement with the experimental spectra in terms of both peak positions and intensities. The differences between the resonance Raman spectra of the three 5-halogenated uracils, caused by the effect of halogen substitution, are examined in terms of ground-state normal-mode eigenvectors and excited-state Cartesian gradients, according to the HT formalism. The differences in the normal-mode eigenvectors and excited-state Cartesian gradients between 5-fluorouracil and 5-chlorouracil are used to interpret the dissimilarity between their resonance Raman spectra. Meanwhile, the similarity between the spectra of 5-chlorouracil and 5-bromouracil is explained by the correspondence between their normal modes and excited-state gradients.

  9. Adapting Raman Spectra from Laboratory Spectrometers to Portable Detection Libraries

    SciTech Connect

    Weatherall, James; Barber, Jeffrey B.; Brauer, Carolyn S.; Johnson, Timothy J.; Su, Yin-Fong; Ball, Christopher D.; Smith, Barry; Cox, Rick; Steinke, Robert; McDaniel, Patricia; Wasserzug, Louis

    2013-02-01

    Raman spectral data collected with high-resolution laboratory spectrometers are processed into a for- mat suitable for importing as a user library on a 1064nm DeltaNu rst generation, eld-deployable spectrometer prototype. The two laboratory systems used are a 1064nm Bruker spectrometer and a 785nm Kaiser spectrometer. The steps taken to compensate for device-dependent spectral resolution, wavenumber shifts between instruments, and wavenumber sensitivity variation are described.

  10. Theoretical study of the resonance Raman spectra for meso-tetrakis(3,5-di-tertiarybutylphenyl)-porphyrin.

    PubMed

    Zheng, Ren-hui; Wei, Wen-mei; Zhu, Li-li; Shi, Qiang

    2014-12-10

    Applying time-dependent density functional theory (TDDFT), we study the resonance Raman spectra for the Q and B bands of the meso-tetrakis(3,5-di-tertiarybutylphenyl)-porphyrin (H2TBPP) molecule including both Raman A term (Franck-Condon term) and Raman B term (Herzberg-Teller term) contributions. It is found that Raman B term can be one order of magnitude larger than Raman A term and dominates resonance Raman for the Q band resonance. In comparison with the recent experimental Raman spectra of H2TBPP with incident light frequency 532nm, we predict the absence of 1580cm(-1) band in the resonance Raman spectra which agrees well with the experimental results, whereas the previous theoretical calculation using non-resonance strategy failed to do so.

  11. Effects of pathology dyes on Raman bone spectra

    PubMed Central

    Esmonde-White, Karen A.; Esmonde-White, Francis W. L.; Morris, Michael D.

    2013-01-01

    Abstract. We report an overlooked source of artifacts for clinical specimens, where unexpected and normally negligible contaminants can skew the interpretation of results. During an ongoing study of bone fragments from diabetic osteomyelitis, strong Raman signatures were found, which did not correspond with normal bone mineral or matrix. In a bone biopsy from the calcaneus of a patient affected by diabetic osteomyelitis, Raman microspectroscopic analysis revealed regions with both abnormal mineral and degraded collagen in addition to normal bone. Additional bands indicated a pathological material. Stenotrophomonas maltophilia was identified in the wound culture by independent microbiologic examination. We initially assigned the unusual bands to xanthomonadin, a bacterial pigment from S. maltophilia. However, the same bands were also found more than a year later on a second specimen that had been noticeably contaminated with pathology marking dye. Drop deposition/Raman spectroscopy of commonly used pathology dyes revealed that a blue tissue-marking dye was responsible for the unusual bands in both specimens, even in the first specimen where there was no visible evidence of contamination. PMID:23640079

  12. Effects of pathology dyes on Raman bone spectra

    NASA Astrophysics Data System (ADS)

    Esmonde-White, Karen A.; Esmonde-White, Francis W. L.; Morris, Michael D.; Roessler, Blake J.

    2013-05-01

    We report an overlooked source of artifacts for clinical specimens, where unexpected and normally negligible contaminants can skew the interpretation of results. During an ongoing study of bone fragments from diabetic osteomyelitis, strong Raman signatures were found, which did not correspond with normal bone mineral or matrix. In a bone biopsy from the calcaneus of a patient affected by diabetic osteomyelitis, Raman microspectroscopic analysis revealed regions with both abnormal mineral and degraded collagen in addition to normal bone. Additional bands indicated a pathological material. Stenotrophomonas maltophilia was identified in the wound culture by independent microbiologic examination. We initially assigned the unusual bands to xanthomonadin, a bacterial pigment from S. maltophilia. However, the same bands were also found more than a year later on a second specimen that had been noticeably contaminated with pathology marking dye. Drop deposition/Raman spectroscopy of commonly used pathology dyes revealed that a blue tissue-marking dye was responsible for the unusual bands in both specimens, even in the first specimen where there was no visible evidence of contamination.

  13. Raman spectra and electron-phonon coupling in disordered graphene with gate-tunable doping

    SciTech Connect

    Childres, Isaac; Jauregui, Luis A.; Chen, Yong P.

    2014-12-21

    We report a Raman spectroscopy study of graphene field-effect transistors with a controlled amount of defects introduced in graphene by exposure to electron-beam irradiation. Raman spectra are taken at T = 8 K over a range of back gate voltages (V{sub g}) for various irradiation dosages (R{sub e}). We study effects in the Raman spectra due to V{sub g}-induced doping and artificially created disorder at various R{sub e}. With moderate disorder (irradiation), the Raman G peak with respect to the graphene carrier density (n{sub FE}) exhibits a minimum in peak frequency and a maximum in peak width near the charge-neutral point (CNP). These trends are similar to those seen in previous works on pristine graphene and have been attributed to a reduction of electron-phonon coupling strength (D) and removal of the Kohn anomaly as the Fermi level moves away from the CNP. We also observe a maximum in I{sub 2D}/I{sub G} and weak maximum in I{sub D}/I{sub G} near the CNP. All the observed dependences of Raman parameters on n{sub FE} weaken at stronger disorder (higher R{sub e}), implying that disorder causes a reduction of D as well. Our findings are valuable for understanding Raman spectra and electron-phonon physics in doped and disordered graphene.

  14. Raman Scattering of Light in Silicon Nanostructures: First- and Second-Order Spectra

    SciTech Connect

    Kravets, V.G.; Kolmykova, V.Yu.

    2005-07-15

    First- and second-order Raman scattering spectra in Si nanocrystals have been studied. The shift to lower frequencies and the substantial broadening of first-order Raman scattering lines observed to occur with decreasing nanoparticle size were established to correlate with those in second-order spectra. It is shown that the experimentally observed shifts of peaks and their broadening cannot be predicted based only on the phenomenological model of strong phonon wave function localization. The anharmonic effect originating from the heating of the nanoparticle surface by laser radiation should also be included. Proper fitting of experimental data revealed that the anharmonic constants depend strongly on nanoparticle size. The shape and spectral positions of maxima in second-order Raman scattering spectra have been theoretically described.

  15. [Raman spectra analysis of Nd : YAG single crystal and its nano-powder].

    PubMed

    Su, Jing; Zhang, Qing-Li; Yin, Shao-Tang; Sun, Dun-Lu; Shao, Shu-Fang

    2009-06-01

    In the present paper, the authors measured the Raman spectra of YAG/Nd : YAG single crystal, Nd : YAG precursor and the powder sintered at different temperatures. The bands of these Raman spectra were assigned and analyzed. The results show that there is a structure transformation process in the course of sintering Nd : YAG precursor. The powder sintered at 700 degrees C was amorphous and it is of AlO4 tetrahedron structure. With the increase in sintering temperatures, the Raman spectra varied mainly in two respects. One is the decrease in FWHM with the increase in the bands intensity; the other is the bands shift. These should be due to the increase in the order degree of the interface component. Additionally, the difference in the lattice vibration modes between the powders sintered at 800 degrees C and the Nd : YAG single crystal powder was caused by the contribution of the interface component.

  16. Experimental and theoretical investigation of pressure-dependent Raman spectra of triaminotrinitrobenzene (TATB) at high pressures

    NASA Astrophysics Data System (ADS)

    Landerville, Aaron C.; Crowhurst, Jonathan C.; Grant, Christian D.; Zaug, Joseph M.; Oleynik, Ivan

    2017-01-01

    The experimental pressure dependent Raman spectra of triamino-trinitrobenzene (TATB) are determined up to 24.5 GPa, and compared with those obtained using density functional theory (DFT) up to 27 GPa. The density functional theory calculations include the Grimme empirical van der Waals correction, as well as corrections for both thermal and zero-point energy contributions to pressure. DFT-predicted crystal structure of TATB at ambient conditions, the equation of state, and Raman spectra up to 24.5 GPa are in good agreement with experiment. Pressure-dependence of specific vibrational modes is discussed in detail. Further, the comparison of experimental and calculated Raman spectra of TATB offers evidence that no first-order polymorphic phase transition occurs at least up to 27 GPa.

  17. Experimental and theoretical investigation of pressure-dependent Raman spectra of triaminotrinitrobenzene (TATB) at high pressures

    NASA Astrophysics Data System (ADS)

    Landerville, Aaron; Grant, Christian; Zaug, Joseph; Crowhurst, Jonathan; Oleynik, Ivan

    2015-06-01

    The experimental pressure dependent Raman spectra of triamino-trinitrobenzene (TATB) are determined up to 27 GPa, and compared with those obtained using density functional theory (DFT). The density functional perturbation theory calculations include the Grimme empirical van der Waals correction, as well as corrections for both thermal and zero-point energy contributions to pressure. DFT calculations of the crystal structure of TATB at ambient conditions, the equation of state, and Raman spectra up to 25 GPa are in good agreement with experiment. Pressure-dependence of specific vibrational modes is discussed in detail. Further, the comparison of experimental and calculated Raman spectra of TATB offers evidence that no first-order polymorphic phase transition occurs at least up to 25 GPa.

  18. Raman and Luminescent Spectra of Sulfonated Zn Phthalocyanine Enhanced by Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Kavelin, V.; Fesenko, O.; Dubyna, H.; Vidal, C.; Klar, T. A.; Hrelescu, C.; Dolgov, L.

    2017-03-01

    Sulfonated Zn phthalocyanine, as a prospective photosensitizer in the photodynamic therapy of tumors, is investigated by means of Raman, infrared, and fluorescence spectroscopies. Conventional and surface-enhanced spectra from this photosensitizer are obtained and compared. Gold nano-islands attached to silica cores (Au-SiO2) are proposed as nanostructures providing plasmonically enhanced signals. Pronounced enhancement of Raman and infrared spectral bands from sulfonated Zn phthalocyanine allows their more convenient assignment with vibrational modes of sulfonated Zn phthalocyanine. In comparison to Raman and IR, the fluorescence is less enhanced by Au-SiO2 particles.

  19. Identifying the lineages of individual cells in cocultures by multivariate analysis of Raman spectra.

    PubMed

    Ilin, Yelena; Kraft, Mary L

    2014-05-07

    The cellular and matrix cues that induce stem cell differentiation into distinct cell lineages must be identified to permit the ex vivo expansion of desired cell populations for clinical applications. Combinatorial biomaterials enable screening multiple different microenvironments while using small numbers of rare stem cells. New methods to identify the phenotypes of individual cells in cocultures with location specificity would increase the efficiency and throughput of these screening platforms. Here, we demonstrate that partial least-squares discriminant analysis (PLS-DA) models of calibration Raman spectra from cells in pure cultures can be used to identify the lineages of individual cells in more complex culture environments. The calibration Raman spectra were collected from individual cells of four different lineages, and a PLS-DA model that captured the Raman spectral profiles characteristic of each cell line was created. The application of these models to Raman spectra from test sets of cells indicated individual, fixed and living cells in separate monocultures, as well as those in more complex culture environments, such as cocultures, could be identified with low error. Cells from populations with very similar biochemistries could also be identified with high accuracy. We show that these identifications are based on reproducible cell-related spectral features, and not spectral contributions from the culture environment. This work demonstrates that PLS-DA of Raman spectra acquired from pure monocultures provides an objective, noninvasive, and label-free approach for accurately identifying the lineages of individual, living cells in more complex coculture environments.

  20. Theoretical analysis of Raman spectra of finite-stage Si/Si-Ge Fibonacci superlattices

    NASA Astrophysics Data System (ADS)

    Aers, G. C.; Dharma-Wardana, M. W. C.; Schwartz, G. P.; Bevk, J.

    1989-01-01

    Raman-scattering results for acoustic phonons in Si/GexSi1-x Fibonacci superlattices with low-stage numbers are analyzed and shown to have significant deviations from the infinite-stage assumption implicit in standard theoretical models. We show that a quantitative description of the observed spectra is possible only with a ``sample-specific'' theory which takes into account the presence of the substrate and the free surface. A nearest-neighbor linear-chain model is used to calculate Raman spectra which are in good agreement with experiment.

  1. Resolving stress tensor components in space from polarized Raman spectra: polycrystalline alumina.

    PubMed

    Pezzotti, Giuseppe; Zhu, Wenliang

    2015-01-28

    A method of Raman spectroscopic analysis has been proposed for evaluating tensorial stress fields stored in alumina polycrystals with a corundum structure (α-Al2O3). Raman selection rules for all the vibrational modes of the structure were expanded into explicit functions of both 3 Euler angles in space and 4 Raman tensor elements (RTE) of corundum. A theoretical treatment was then worked out according to the phonon deformation potential (PDP) formalism, which explicitly expressed the changes in force constants under stress in matricial form. Close-form solutions could be obtained for the matrix eigenvalues as a function of 9 unknown variables, namely 6 independent stress tensor components and 3 Euler angles in space, the latter parameters being representatives of local crystal orientation. Successively, two separate sets of Raman calibration experiments were performed for the determination of both RTE and PDP constants of the corundum structure of alumina. Calibration experiments provided a quantitative frame to the newly developed Raman formalism. Polarized Raman spectra were systematically recorded in both single-crystalline and polycrystalline samples, with both A1g and Eg vibrational bands being characterized. Regarding polycrystalline samples, a validation of the proposed Raman method could be done through a comparison between Raman and fluorescence data collected at the same locations across an alumina/metal interface embedded in a steeply graded residual stress field.

  2. [Surface-enhanced Raman spectra analysis of trace degradation products from goat horn].

    PubMed

    Pan, Yan-Ting; Ao, Ning-Jian; Shan, Guang-Hua; Zhang, Gang-Ping; Zhang, Quan-Bin; Yang, Ji-Wang; He, Chun-Lan; Huang, Yao-Xiong

    2014-04-01

    Nano-silver colloid was synthesized by using microwave method on the mixtures of sodium citrate solution and silver nitrate solution. The method has advantages of fast heating speed, uniform temperature distribution and easily controlled reaction conditions. The sizes and size distributions of the silver particles were characterized by means of quasi-elastic laser scattering (QLS). The average particles size was (53.27 +/- 2.65) nm and the size of the particles was mainly distributed around 56 nm. Surface-enhanced Raman spectra of the degradation products from goat horn were obtained with silver colloid as active substrate. It was observed that the Raman signal of SERS was enhanced significantly compared with that of regular Raman spectrum, especially at the Raman bands of 659, 830, 850, 929, 999, 1 028, 1 280, 1 439 and 1 599 cm(-1) which reflect the biochemical components in degradation products. The characteristic Raman bands of degradation products from goat horn were preliminary assigned. The assignments showed that the main constituents of the degradation products from goat horn were amino acids and polypeptides. It was for the first time that Surface-enhanced Raman spectroscopy was used to detect trace degradation products from the horns. Raman signal enhancement can be obtained with high sensitivity for the trace concentrations as low as ppm level. It is concluded that surface-enhanced Raman spectroscopy can provide a fast, direct and precise detecting method for the detection of trace degradation solution from horns.

  3. Wave packet theory of dynamic stimulated Raman spectra in femtosecond pump-probe spectroscopy.

    PubMed

    Sun, Zhigang; Jin, Zhongqi; Lu, J; Zhang, Dong H; Lee, Soo-Y

    2007-05-07

    The quantum theory for stimulated Raman spectroscopy from a moving wave packet using the third-order density matrix and polarization is derived. The theory applies, in particular, to the new technique of femtosecond broadband stimulated Raman spectroscopy (FSRS). In the general case, a femtosecond actinic pump pulse first prepares a moving wave packet on an excited state surface which is then interrogated with a coupled pair of picosecond Raman pump pulse and a femtosecond Raman probe pulse and the Raman gain in the direction of the probe pulse is measured. It is shown that the third-order polarization in the time domain, whose Fourier transform governs the Raman gain, is given simply by the overlap of a first-order wave packet created by the Raman pump on the upper electronic state with a second-order wave packet on the initial electronic state that is created by the coupling of the Raman pump and probe fields acting on the molecule. Calculations are performed on model potentials to illustrate and interpret the FSRS spectra.

  4. Excitation wavelength-dependent changes in Raman spectra of whole blood and hemoglobin: comparison of the spectra with 514.5-, 720-, and 1064-nm excitation

    NASA Astrophysics Data System (ADS)

    Sato, Hidetoshi; Chiba, Hironori; Tashiro, Hideo; Ozaki, Yukihiro

    2001-07-01

    Raman spectra of whole blood and oxy-hemoglobin (Hb) were measured under the same conditions with visible (514.5 nm) and near-infrared (NIR; 720 and 1064 nm) excitation, and the obtained spectra were compared in detail. The Raman spectrum of blood excited with visible light is dominated by very intense bands due to carotenoids, so that it was difficult to obtain information about Hb from the spectrum. The Raman spectra of whole blood and oxy-Hb excited with 720 nm light are very close to each other; both spectra are essentially Raman spectra of the heme chromophore that is preresonant with Q bands. Qualitative spectral analysis including band assignment and investigation of nature of resonance effect were carried out for the Raman spectra with 720 nm excitation. The spectra of whole blood and oxy-Hb excited with 1064 nm light contain contributions from nonresonance Raman spectra of the heme chromophore and Raman spectra of proteins. The 1064 nm excited spectra of blood and oxy-Hb are similar to each other but different in some features. For example, bands due to protein appear stronger in the spectrum of whole blood than in that of oxy-Hb which does not contain protein except globin part. The comparison between the 514.5, 720, and 1064 nm excited Raman spectra reveal that the excitation wavelength of 720 nm is more practical than that of visible light and 1064 nm in the Raman analysis of Hb, such as oxygenation, specially in situ measurement.

  5. [Raman spectra characteristics of alunite in the Zijinshan gold-copper deposit].

    PubMed

    Wang, Cui-Zhi; Xiong, Xin

    2014-02-01

    The Zijinshan gold-copper deposit is the first one of high sulfidation epithermal hydrothermal deposits. The gold bodies up, and the copper bodies down. The gold bodies mainly occur above the ground water table associated with strong silicification, and the copper bodies mainly occur below the ground water table associated with alunitization. The alunite of the Zijinshan gold-copper deposit has four types of occurrence status, that is the altered rock type, the intergrowth-with-Cu-sulphide type, the vein type and the powder type. Different types of the alunite are of different Raman spectra characteristics and fluorescence scattering background. Laser Raman spectra of inclusions in the alunite show that: (1) The characteristics of the Laser Raman spectra of the alunite are of characteristic spectral bands of alunite, just fluorescent scattering weaken gradually from the altered rock type, the intergrowth-with-Cu-sulphide type to the vein type; the alunite in the Powder type has different bands of the Laser Raman spectra relative to the former three types, the intensity of each band is weaker, and it's fluorescent scattering intensity is strongger. (2) The bands in 100-700 cm(-1) of the Laser Raman spectra can be used as "fingerprint" bands indicating the condition of the cation replacement in the molecular structure of alunite. The intensities at 161 and 234 peak change obviously in the bands of the alunite in the altered rock type, which indicating a wide replacement between K and Na; the intensities at 381 and 484 peak in the bands of the alunite in the intergrowth-with-Cu-sulphide type change significantly, indicating Al can be replaced with Cu, Ga, etc.; the larger and stable intensities of the alunite in the vein type in the bands at the peaks about 161, 234, 484, 508, etc. indicate that there are less chances with the replacement between K and Na, Al and Si; fluorescence scatorescent scattering is very strong and the intensity of each band is weaker in the

  6. Structure, IR and Raman spectra of phosphotrihydrazide studied by DFT

    NASA Astrophysics Data System (ADS)

    Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

    2016-09-01

    The FTIR and FT Raman measurements of the phosphotrihydrazide (S)P[N(Me)-NH2]3 have been performed. This compound is a zero generation dendrimer G0 with terminal amine groups. Structural optimization and normal mode analysis were obtained for G0 by the density functional theory (DFT). Optimized geometric bond length and angles obtained by DFT show good agreement with experiment. The amine terminal groups are characterized by the well-defined bands at 3321, 3238, 1614 cm- 1 in the experimental IR spectrum and by bands at 3327, 3241 cm- 1 in the Raman spectrum of G0. The experimental frequencies of asymmetric and symmetric NH2 stretching vibrations of amine group are lower than theoretical values due to intramolecular Nsbnd H ⋯ S hydrogen bond. This hydrogen bond is also responsible for higher experimental infrared intensity of these bands as compared with theoretical values. Relying on DFT calculations a complete vibrational assignment is proposed for the studied dendrimer.

  7. Raman spectra of Martian glass analogues: A tool to approximate their chemical composition

    NASA Astrophysics Data System (ADS)

    Di Genova, Danilo; Kolzenburg, Stephan; Vona, Alessandro; Chevrel, Magdalena Oryaëlle; Hess, Kai-Uwe; Neuville, Daniel R.; Ertel-Ingrisch, Werner; Romano, Claudia; Dingwell, Donald B.

    2016-05-01

    Raman spectrometers will form a key component of the analytical suite of future planetary rovers intended to investigate geological processes on Mars. In order to expand the applicability of these spectrometers and use them as analytical tools for the investigation of silicate glasses, a database correlating Raman spectra to glass composition is crucial. Here we investigate the effect of the chemical composition of reduced silicate glasses on their Raman spectra. A range of compositions was generated in a diffusion experiment between two distinct, iron-rich end-members (a basalt and a peralkaline rhyolite), which are representative of the anticipated compositions of Martian rocks. Our results show that for silica-poor (depolymerized) compositions the band intensity increases dramatically in the regions between 550-780 cm-1 and 820-980 cm-1. On the other hand, Raman spectra regions between 250-550 cm-1 and 1000-1250 cm-1 are well developed in silica-rich (highly polymerized) systems. Further, spectral intensity increases at ~965 cm-1 related to the high iron content of these glasses (~7-17 wt % of FeOtot). Based on the acquired Raman spectra and an ideal mixing equation between the two end-members we present an empirical parameterization that enables the estimation of the chemical compositions of silicate glasses within this range. The model is validated using external samples for which chemical composition and Raman spectra were characterized independently. Applications of this model range from microanalysis of dry and hydrous silicate glasses (e.g., melt inclusions) to in situ field investigations and studies under extreme conditions such as extraterrestrial (i.e., Mars) and submarine volcanic environments.

  8. Raman spectra of Martian glass analogues: A tool to approximate their chemical composition.

    PubMed

    Di Genova, Danilo; Kolzenburg, Stephan; Vona, Alessandro; Chevrel, Magdalena Oryaëlle; Hess, Kai-Uwe; Neuville, Daniel R; Ertel-Ingrisch, Werner; Romano, Claudia; Dingwell, Donald B

    2016-05-01

    Raman spectrometers will form a key component of the analytical suite of future planetary rovers intended to investigate geological processes on Mars. In order to expand the applicability of these spectrometers and use them as analytical tools for the investigation of silicate glasses, a database correlating Raman spectra to glass composition is crucial. Here we investigate the effect of the chemical composition of reduced silicate glasses on their Raman spectra. A range of compositions was generated in a diffusion experiment between two distinct, iron-rich end-members (a basalt and a peralkaline rhyolite), which are representative of the anticipated compositions of Martian rocks. Our results show that for silica-poor (depolymerized) compositions the band intensity increases dramatically in the regions between 550-780 cm(-1) and 820-980 cm(-1). On the other hand, Raman spectra regions between 250-550 cm(-1) and 1000-1250 cm(-1) are well developed in silica-rich (highly polymerized) systems. Further, spectral intensity increases at ~965 cm(-1) related to the high iron content of these glasses (~7-17 wt % of FeOtot). Based on the acquired Raman spectra and an ideal mixing equation between the two end-members we present an empirical parameterization that enables the estimation of the chemical compositions of silicate glasses within this range. The model is validated using external samples for which chemical composition and Raman spectra were characterized independently. Applications of this model range from microanalysis of dry and hydrous silicate glasses (e.g., melt inclusions) to in situ field investigations and studies under extreme conditions such as extraterrestrial (i.e., Mars) and submarine volcanic environments.

  9. Broadband coherent Raman spectroscopy running at 24,000 spectra per second

    NASA Astrophysics Data System (ADS)

    Hashimoto, Kazuki; Takahashi, Megumi; Ideguchi, Takuro; Goda, Keisuke

    2016-02-01

    We present a Fourier-transform coherent anti-Stokes Raman scattering (FT-CARS) spectroscopy technique that achieves broadband CARS measurements at an ultrahigh scan rate of more than 20,000 spectra/s – more than 20 times higher than that of previous broadband coherent Raman scattering spectroscopy techniques. This is made possible by an integration of a FT-CARS system and a rapid-scanning retro-reflective optical path length scanner. To demonstrate the technique’s strength, we use it to perform broadband CARS spectroscopy of the transient mixing dynamics of toluene and benzene in the fingerprint region (200–1500 cm‑1) with spectral resolution of 10 cm‑1 at a record high scan rate of 24,000 spectra/s. Our rapid-scanning FT-CARS technique holds great promise for studying chemical dynamics and wide-field label-free biomedical imaging.

  10. Broadband coherent Raman spectroscopy running at 24,000 spectra per second

    PubMed Central

    Hashimoto, Kazuki; Takahashi, Megumi; Ideguchi, Takuro; Goda, Keisuke

    2016-01-01

    We present a Fourier-transform coherent anti-Stokes Raman scattering (FT-CARS) spectroscopy technique that achieves broadband CARS measurements at an ultrahigh scan rate of more than 20,000 spectra/s – more than 20 times higher than that of previous broadband coherent Raman scattering spectroscopy techniques. This is made possible by an integration of a FT-CARS system and a rapid-scanning retro-reflective optical path length scanner. To demonstrate the technique’s strength, we use it to perform broadband CARS spectroscopy of the transient mixing dynamics of toluene and benzene in the fingerprint region (200–1500 cm−1) with spectral resolution of 10 cm−1 at a record high scan rate of 24,000 spectra/s. Our rapid-scanning FT-CARS technique holds great promise for studying chemical dynamics and wide-field label-free biomedical imaging. PMID:26875786

  11. Raman spectra of adsorbed layers on space shuttle and AOTV thermal protection system surface

    NASA Technical Reports Server (NTRS)

    Willey, Ronald J.

    1987-01-01

    Surfaces of interest to space vehicle heat shield design were struck by a 2 W argon ion laser line while subjected to supersonic arc jet flow conditions. Emission spectra were taken at 90 deg to the angle of laser incidence on the test object. Results showed possible weak Raman shifts which could not be directly tied to any particular parameter such as surface temperature or gas composition. The investigation must be considered exploratory in terms of findings. Many undesirable effects were found and corrected as the project progressed. For instance, initial spectra settings led to ghosts which were eliminated by closing the intermediate of filter slit of the Spex from 8 to 3 mm. Further, under certain conditions, plasma lines from the laser were observed. Several materials were also investigated at room temperature for Raman shifts. Results showed Raman shifts for RCC and TEOS coated materials. The HRSI materials showed only weak Raman shifts, however, substantial efforts were made in studying these materials. Baseline materials showed the technique to be sound. The original goal was to find a Raman shift for the High-temperature Reusable Surface Insulation (HRSI) Reaction Cured borosilicate Glass (RCG) coated material and tie the amplitude of this peak to Arc jet conditions. Weak Raman shifts may be present, however, time limitations prevented confirmation.

  12. Comparative study of resonance Raman and surface-enhanced resonance Raman chlorophyll a spectra using soret and red excitation

    SciTech Connect

    Thomas, L.L.; Kim, Jaeho; Cotton, T.M. )

    1990-12-05

    Surface-enhanced resonance Raman scattering (SERRS) spectra are reported for chlorophyll a adsorbed on a silver electrode at 298 and 77 K with 406.7-, 457.9-, 514.5-, and 647.1-nm excitation. Submerging the electrode in degassed water at 298 K was found to improve the spectral quality by minimizing sample heating and photooxidation. Spectral intensities and peak resolutions were greater at all excitation wavelengths at liquid nitrogen temperature. Most significantly, roughened silver at the low temperature quenched the fluorescence accompanying red excitation and minimized sample photooxidation, resulting in richly detailed SERRS spectra of chlorophyll a. The close correspondence between chlorophyll a resonance Raman (RR) and SERRS spectra suggests that an electromagnetic mechanism is the major source of the surface enhancement, rather than a chemical mechanism (e.g. a charge-transfer complex between chlorophyll a and the metal). The spectral similarities, together with the presence of the MgN{sub 4} vibration band in the SERRS spectra, also provide evidence that structural alterations (e.g. cleavage of ring V or loss of Mg) do not occur in chlorophyll a after adsorption at the electrode surface. A distinctive SERRS spectrum was obtained for each excitation wavelength. Selective excitation within the various electronic transitions can thus be utilized to verify assignments of the vibrational modes of chlorophyll a and to monitor its interactions and photochemical behavior in biomimetic systems.

  13. Raman spectra of the different phases in the CaSO4-H2O system.

    PubMed

    Prieto-Taboada, Nagore; Gómez-Laserna, Olivia; Martínez-Arkarazo, Irantzu; Olazabal, María Ángeles; Madariaga, Juan Manuel

    2014-10-21

    Although it is known that the CaSO4/H2O system is formed by at least five different phases, this fact is not correctly documented in Raman spectroscopy studies. The main problem detected in the literature was the incorrect definition of the anhydrite, which produced the assignation of different spectra for a single compound. In this sense, two different spectra were clearly identified from the bibliography, which showed different main Raman bands at 1017 or 1025 cm(-1), although anhydrite could be present even as three different polymorphous species with different structures. A better understanding of the whole system obtained from a review of the literature allowed new conclusions to be established. Thanks to that revision and the development of different thermodynamical experiments by Raman spectroscopy, the Raman spectra of each phase were successfully identified for the first time. In this way, the main Raman bands of gypsum, bassanite, anhydrite III, anhydrite II and anhydrite I were identified at 1008, 1015, 1025, 1017 and 1017 cm(-1), respectively. To conclude this work, the contradictions found in literature were critically summarized.

  14. A rapidly modulated multifocal detection scheme for parallel acquisition of Raman spectra from a 2-D focal array.

    PubMed

    Kong, Lingbo; Chan, James

    2014-07-01

    We report the development of a rapidly modulated multifocal detection scheme that enables full Raman spectra (~500-2000 cm(-1)) from a 2-D focal array to be acquired simultaneously. A spatial light modulator splits a laser beam to generate an m × n multifocal array. Raman signals generated within each focus are projected simultaneously into a spectrometer and imaged onto a TE-cooled CCD camera. A shuttering system using different masks is constructed to collect the superimposed Raman spectra of different multifocal patterns. The individual Raman spectrum from each focus is then retrieved from the superimposed spectra with no crosstalk using a postacquisition data processing algorithm. This system is expected to significantly improve the speed of current Raman-based instruments such as laser tweezers Raman spectroscopy and hyperspectral Raman imaging.

  15. Temperature dependence of the resonance Raman spectra of plastocyanin and azurin between cryogenic and ambient conditions.

    PubMed

    Woodruff, W H; Norton, K A; Swanson, B I; Fry, H A

    1984-02-01

    Resonance Raman spectra of spinach plastocyanin and Pseudomonas aeruginosa azurin were studied as a function of temperature between 10 K and 300 K. The spectra are markedly improved both in signal/noise ratio and in resolution at low temperatures. The assignments of the resonance Raman-active vibrations are reinterpreted in view of the number and intensities of peaks observed in the low-temperature spectra. Features appear in the low-temperature spectra of azurin that may be due to copper-bound methionine. The plastocyanin spectra undergo a transition between 220 K and the melting point of water that results in dramatically narrowed peaks at lower temperature and a shift in the carbon-sulfur stretching frequency of the copper-bound cysteine, suggesting a structural change in the active site and an accompanying effect on vibrational dephasing. Considering that the structures and nonvibrational spectroscopies of these two proteins are similar, the substantial differences in the resonance Raman spectra are striking and significant.

  16. Effect of disordering in rare earth titanates on their Raman spectra

    SciTech Connect

    Mel'nik, N.N.; Tsapenko, L.M.

    1986-09-01

    The authors study the rare earth titanates obtained by quenching from the melt using Raman spectroscopy. Secimens with the general formula Ln/sub 2/Ti/sub 2/O/sub 7/ and Ln/sub 2/TiO/sub 5/ (Ln = La to Lu, Y) were prepared by melting the initial oxides on a Uran beam-heating unit, followed by quenching on a cooled substrate. The Raman spectra were excited by an argon laser and recorded by means of a double monochromator in the photon counting regime. With an increase in the rate of quenching the structure was altered for certain specimens, this being established from the x-ray diffraction patterns and the Raman spectra.

  17. Infrared and Raman spectra, DFT-calculations and spectral assignments of germacyclohexane

    SciTech Connect

    Aleksa, V. Ozerenskis, D.; Pucetaite, M.; Sablinskas, V.; Cotter, C.; Guirgis, G. A.

    2015-03-30

    Raman spectra of germacyclohexane in liquid and solid states were recorded and depolarization data obtained. Infrared absorption spectra of the vapor and liquid have been studied. The wavenumbers of the vibrational modes were derived in the harmonic and anharmonic approximation in B3LYP/ccpVTZ calculations. According to the calculations, germacyclohexane exists in the stable chair conformation, whereas a possible twist form should have more than 15 kJ·mol{sup -1} higher enthalpy of formation what makes this conformer experimentally not observable. The 27 A' and 21 A'' fundamentals were assigned on the basis of the calculations and infrared and Raman band intensities, contours of gas phase infrared spectral bands and Raman depolarization measurements. An average discrepancy of ca. 0.77 % was found between the observed and the calculated anharmonic wavenumbers for the 48 modes. Substitution of carbon atom with Ge atom in the cyclohexane ring is reasoning flattening of the ring.

  18. Resonance Raman Spectra of Hemoglobin and Cytochrome c: Inverse Polarization and Vibronic Scattering

    PubMed Central

    Spiro, Thomas G.; Strekas, Thomas C.

    1972-01-01

    Resonance Raman spectra of hemoglobin and cytochrome c in dilute solution contain prominent bands that exhibit inverse polarization, i.e., the polarization vector of the incident radiation is rotated through 90° for 90° scattering, giving infinite depolarization ratios. This phenomenon is shown to require an antisymmetric molecular-scattering tensor. The antisymmetry, which is characteristic of resonance scattering, is associated with the form of a particular class of vibrations, A20, of the tetragonal heme chromophores. The dependence of the resonance Raman spectra on the wavelength of the exciting radiation, as well as their polarization properties, demonstrates that the prominent bands correspond to vibronically active modes of the first electronic transition of the heme proteins, and provide confirmation of Albrecht's vibronic theory of Raman intensities. PMID:4506783

  19. Probabilistic partial least squares regression for quantitative analysis of Raman spectra.

    PubMed

    Li, Shuo; Nyagilo, James O; Dave, Digant P; Wang, Wei; Zhang, Baoju; Gao, Jean

    2015-01-01

    With the latest development of Surface-Enhanced Raman Scattering (SERS) technique, quantitative analysis of Raman spectra has shown the potential and promising trend of development in vivo molecular imaging. Partial Least Squares Regression (PLSR) is state-of-the-art method. But it only relies on training samples, which makes it difficult to incorporate complex domain knowledge. Based on probabilistic Principal Component Analysis (PCA) and probabilistic curve fitting idea, we propose a probabilistic PLSR (PPLSR) model and an Estimation Maximisation (EM) algorithm for estimating parameters. This model explains PLSR from a probabilistic viewpoint, describes its essential meaning and provides a foundation to develop future Bayesian nonparametrics models. Two real Raman spectra datasets were used to evaluate this model, and experimental results show its effectiveness.

  20. The macroscopic field in ultrathin molecular films and its manifestation in absorption and Raman spectra

    SciTech Connect

    Tyu, N.S.

    1995-12-01

    Optical properties of an ultrathin molecular film placed in a dielectric medium are considered. A macroscopic field is calculated and a spectrum of Coulomb excitons is found. The features of their manifestation in absorption and Raman spectra are studied. 15 refs., 2 figs.

  1. [Qualitative analysis of Raman spectra based on pulse coupled neural network].

    PubMed

    Wang, Cheng; Li, Shao-fa; Wu, Zheng-jie; He, Kai; Huang, Yao-xiong

    2010-09-01

    By studying on pulse coupled neural network (PCNN) and Raman spectra qualitative analysis, a method based on PCNN for Raman spectra qualitative analysis was proposed. After encoding the Raman spectra by using PCNN neurons' characteristics of fatigue and refractory period, the improved Horspool algorithm was used to match the code corresponding to the detected sample with all of the base code in the database one by one, and then their matching similarity was acquired to determine the sample type. Experimental results and analysis of data proved that the method proposed in this paper is accurate and effective for Raman spectra qualitative analysis. Meanwhile, traditional qualitative analysis method based on spectral template has some deficiencies, like that it is difficult to determine the characteristic peak of the detected sample and the matching analysis process has a high degree of redundancy. While our proposed method not only can avoid these deficiencies very well, but also needs a small amount of data storage. The requirement of the storage space was only 5.8% of that used in the traditional qualitative analysis method based on spectral template.

  2. A study on bovine erythrocyte superoxide dismutase by controlled potential electrolysis and Raman spectra.

    PubMed

    Wang, Zhi-Lin; Luo, Qin-Hui; Qian, Wen; Shen, Meng-Chang

    2004-08-01

    The electrochemical behavior of Cu(2)Zn(2)SOD on mercury electrodes was studied by controlled potential electrolysis. By comparison of UV, Raman spectra and activity of Cu(2)Zn(2)SOD before electrochemical reduction and after re-oxidation, it is proved that the conformation and activity are not changed.

  3. Roto-translational Raman spectra of pairs of hydrogen molecules from first principles.

    PubMed

    Gustafsson, Magnus; Frommhold, Lothar; Li, Xiaoping; Hunt, K L C

    2009-04-28

    We calculate the collision-induced, roto-translational, polarized, and depolarized Raman spectra of pairs of H(2) molecules. The Schrodinger equation of H(2)-H(2) scattering in the presence of a weak radiation field is integrated in the close-coupled scheme. This permits the accounting for the anisotropy of the intermolecular potential energy surface and thereby it includes mixing of polarizability components. The static polarizability invariants, trace and anisotropy, of two interacting H(2) molecules were obtained elsewhere [Li et al., J. Chem. Phys. 126, 214302 (2007)] from first principles. Here we report the associated spherical tensor components which, along with the potential surface, are input in the calculation of the supramolecular Raman spectra. Special attention is paid to the interferences in the wings of the rotational S(0)(0) and S(0)(1) lines of the H(2) molecule. The calculated Raman pair spectra show reasonable consistency with existing measurements of the polarized and depolarized Raman spectra of pairs of H(2) molecules.

  4. Detection of Chemicals in Mixed, Two-Dimensional Raman Spectra

    DTIC Science & Technology

    2010-03-18

    pure’ components may be written (at least approximately) as a linear sum of the spectra of the individual components. Over the last several years , a...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Research Laboratory,4555 Overlook Ave SW...Washington,DC,20706 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S

  5. Detection of Chemicals in Mixed, Two-Dimensional Raman Spectra

    DTIC Science & Technology

    2011-02-08

    PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION...approximately) as a linear sum of the spectra of the individual components. Over the last several years , a wide variety of different ‘target detection... low -dimensional space (that can be determined via singular value decomposition, or SVD). We take this subspace to be the target / background

  6. Temperature effects in low-frequency Raman spectra of corticosteroid hormones

    NASA Astrophysics Data System (ADS)

    Minaeva, V. A.; Minaev, B. F.; Baryshnikov, G. V.; Surovtsev, N. V.; Cherkasova, O. P.; Tkachenko, L. I.; Karaush, N. N.; Stromylo, E. V.

    2015-02-01

    Experimental Raman spectra of the corticosteroid hormones corticosterone and desoxycorticosterone are recorded at different temperatures (in the range of 30-310 K) in the region of low-frequency (15-120 cm-1) vibrations using a solid-state laser at 532.1 nm. The intramolecular vibrations of both hormones are interpreted on the basis of Raman spectra calculated by the B3LYP/6-31G(d) density functional theory method. The intermolecular bonds in tetramers of hormones are studied with the help of the topological theory of Bader using data of X-ray structural analysis for crystalline samples of hormones. The total energy of intermolecular interactions in the tetramer of desoxycorticosterone (-49.1 kJ/mol) is higher than in the tetramer of corticosterone (-36.9 kJ/mol). A strong intramolecular hydrogen bond O21-H⋯O=C20 with an energy of -42.4 kJ/mol was revealed in the corticosterone molecule, which is absent in the desoxycorticosterone molecule. This fact makes the Raman spectra of both hormones somewhat different. It is shown that the low-frequency lines in the Raman spectra are associated with skeletal vibrations of molecules and bending vibrations of the substituent at the C17 atom. The calculated Raman spectrum of the desoxycorticosterone dimer allows one to explain the splitting and shift of some lines and to interpret new strong lines observed in the spectra at low temperatures, which are caused by the intermolecular interaction and mixing of normal vibrations in a crystal cell. On the whole the calculated frequencies are in a good agreement with the experimental results.

  7. [Raman spectra of endospores of Bacillus subtilis by alkali stress].

    PubMed

    Dong, Rong; Lu, Ming-qian; Li, Feng; Shi, Gui-yu; Huang, Shu-shi

    2013-09-01

    To research the lethal mechanism of spores stressed by alkali, laser tweezers Raman spectroscopy (LTRS) combined with principal components analysis (PCA) was used to study the physiological process of single spore with alkali stress. The results showed that both spores and germinated spores had tolerance with alkali in a certain range, but the ability of spores was obviously lower than that of spores due to the release of their Ca2+ -DPA which plays a key role in spores resistance as well as spores resistance to many stresses; A small amount of Ca2+ -DPA of spores was observed to release after alkali stress, however, the behavior of release was different with the normal Ca2+ -DPA release behavior induced by L-alanine; The data before and after alkali stress of the spores and g. spores with PCA reflected that alkali mainly injured the membrane of spores, and alkali could be easily enter into the inner structure of spores to damage the structure of protein backbone and injure the nucleic acid of spores. We show that the alkali could result in the small amount of Ca2+ -DPA released by destroying the member channel of spores.

  8. Calculation of Raman optical activity spectra for vibrational analysis.

    PubMed

    Mutter, Shaun T; Zielinski, François; Popelier, Paul L A; Blanch, Ewan W

    2015-05-07

    By looking back on the history of Raman Optical Activity (ROA), the present article shows that the success of this analytical technique was for a long time hindered, paradoxically, by the deep level of detail and wealth of structural information it can provide. Basic principles of the underlying theory are discussed, to illustrate the technique's sensitivity due to its physical origins in the delicate response of molecular vibrations to electromagnetic properties. Following a short review of significant advances in the application of ROA by UK researchers, we dedicate two extensive sections to the technical and theoretical difficulties that were overcome to eventually provide predictive power to computational simulations in terms of ROA spectral calculation. In the last sections, we focus on a new modelling strategy that has been successful in coping with the dramatic impact of solvent effects on ROA analyses. This work emphasises the role of complementarity between experiment and theory for analysing the conformations and dynamics of biomolecules, so providing new perspectives for methodological improvements and molecular modelling development. For the latter, an example of a next-generation force-field for more accurate simulations and analysis of molecular behaviour is presented. By improving the accuracy of computational modelling, the analytical capabilities of ROA spectroscopy will be further developed so generating new insights into the complex behaviour of molecules.

  9. Studies of the Raman spectra of cyclic and acyclic molecules: Combination and prediction spectrum methods

    NASA Astrophysics Data System (ADS)

    Kim, Taejin; Assary, Rajeev S.; Marshall, Christopher L.; Gosztola, David J.; Curtiss, Larry A.; Stair, Peter C.

    2012-04-01

    A combination of Raman spectroscopy and density functional methods was employed to investigate the spectral features of selected molecules: furfural, 5-hydroxymethyl furfural (HMF), methanol, acetone, acetic acid, and levulinic acid. The computed spectra and measured spectra are in excellent agreement, consistent with previous studies. Using the combination and prediction spectrum method (CPSM), we were able to predict the important spectral features of two platform chemicals, HMF and levulinic acid. The results have shown that CPSM is a useful alternative method for predicting vibrational spectra of complex molecules in the biomass transformation process.

  10. Studies of the Raman Spectra of Cyclic and Acyclic Molecules: Combination and Prediction Spectrum Methods

    SciTech Connect

    Kim, Taijin; Assary, Rajeev S.; Marshall, Christopher L.; Gosztola, David J.; Curtiss, Larry A.; Stair, Peter C.

    2012-04-02

    A combination of Raman spectroscopy and density functional methods was employed to investigate the spectral features of selected molecules: furfural, 5-hydroxymethyl furfural (HMF), methanol, acetone, acetic acid, and levulinic acid. The computed spectra and measured spectra are in excellent agreement, consistent with previous studies. Using the combination and prediction spectrum method (CPSM), we were able to predict the important spectral features of two platform chemicals, HMF and levulinic acid.The results have shown that CPSM is a useful alternative method for predicting vibrational spectra of complex molecules in the biomass transformation process.

  11. Ensemble multivariate analysis to improve identification of articular cartilage disease in noisy Raman spectra.

    PubMed

    Richardson, Wade; Wilkinson, Dan; Wu, Ling; Petrigliano, Frank; Dunn, Bruce; Evseenko, Denis

    2015-07-01

    The development of new methods for the early diagnosis of cartilage disease could offer significant improvement in patient care. Raman spectroscopy is an emerging biomedical technology with unique potential to recognize disease tissues, though difficulty in obtaining the samples needed to train a diagnostic and excessive signal noise could slow its development into a clinical tool. In the current report we detail the use of principal component analysis--linear discriminant analysis (PCA-LDA) on spectra from pairs of materials modeling cartilage disease to create multiple spectral scoring metrics, which could limit the reliance on primary training data for identifying disease in low signal-to-noise-ratio (SNR) Raman spectra. Our proof-of-concept experiments show that combinations of these model-metrics has the potential to improve the classification of low-SNR Raman spectra from human normal and osteoarthritic (OA) cartilage over a single metric trained with spectra from the same healthy and OA tissues. Scatter plot showing the PCA-LDA derived human-disease-metric scores versus rat-model-metric scores for 7656 low signal-to-noise spectra from healthy (blue) and osteoarthritic (red) cartilage. Light vertical and horizontal lines represent the optimized single metric classification boundary. Dark diagonal line represents the classification of boundary resulting from the optimized combination of the two metrics.

  12. Infrared, Polarized Raman, and SERS Spectra of Betaine Hydrogen Oxalate Monohydrate

    NASA Astrophysics Data System (ADS)

    Philip, Daizy; Aruldhas, G.

    1995-01-01

    Infrared and polarized Raman spectra of betaine hydrogen oxalate monohydrate are recorded and analyzed. The observed bands are assigned on the basis of vibrations due to oxalic acid, betaine, and water molecules. In the crystal it is found that oxalic acid molecules occupy a lower site and that betaine exists in zwitterionic form. Oxalic acid and water molecules are involved in strong hydrogen bending. Band assignments are confirmed by deuteration. Surface enhanced Raman scattering (SERS) spectra recorded in two silver colloids reveal chemisorption through different adsorption sites. The observed SERS spectra are interpreted on the basis of different adsorption sites, geometries, and adsorbate conformation/orientation. The change of the SERS spectrum with time is due to the different stabilities of the adsorbed states. The oxalic acid molecules of the compound are likely to be in a tilted orientation with respect to the silver surface.

  13. Wavelet data analysis of micro-Raman spectra for follow-up monitoring in oral pathologies

    NASA Astrophysics Data System (ADS)

    Camerlingo, C.; Zenone, F.; Perna, G.; Capozzi, V.; Cirillo, N.; Gaeta, G. M.; Lepore, M.

    2008-02-01

    A wavelet multi-component decomposition algorithm has been used for data analysis of micro-Raman spectra from human biological samples. In particular, measurements have been performed on some samples of oral tissue and blood serum from patients affected by pemphigus vulgaris at different stages. Pemphigus is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. The disease is characterized histologically by intradermal blisters and immunopathologically by the finding of tissue bound and circulating immunoglobulin G (IgG) antibody directed against the cell surface of keratinocytes. More than 150 spectra were measured by means of a Raman confocal microspectrometer apparatus using the 632.8 nm line of a He-Ne laser source. A discrete wavelet transform decomposition method has been applied to the recorded Raman spectra in order to overcome related to low-level signals and the presence of noise and background components due to light scattering and fluorescence. The results indicate that appropriate data processing can contribute to enlarge the medical applications of micro-Raman spectroscopy.

  14. First-principles simulation of Raman spectra and structural properties of quartz up to 5 GPa

    NASA Astrophysics Data System (ADS)

    Liu, Lei; Lv, Chao-Jia; Zhuang, Chun-Qiang; Yi, Li; Liu, Hong; Du, Jian-Guo

    2015-12-01

    The crystal structure and Raman spectra of quartz are calculated by using first-principles method in a pressure range from 0 to 5 GPa. The results show that the lattice constants (a, c, and V) decrease with increasing pressure and the a-axis is more compressible than the c axis. The Si-O bond distance decreases with increasing pressure, which is in contrast to experimental results reported by Hazen et al. [Hazen R M, Finger L W, Hemley R J and Mao H K 1989 Solid State Communications 725 507-511], and Glinnemann et al. [Glinnemann J, King H E Jr, Schulz H, Hahn T, La Placa S J and Dacol F 1992 Z. Kristallogr. 198 177-212]. The most striking changes are of inter-tetrahedral O-O distances and Si-O-Si angles. The volume of the tetrahedron decreased by 0.9% (from 0 to 5 GPa), which suggests that it is relatively rigid. Vibrational models of the quartz modes are identified by visualizing the associated atomic motions. Raman vibrations are mainly controlled by the deformation of the tetrahedron and the changes in the Si-O-Si bonds. Vibrational directions and intensities of atoms in all Raman modes just show little deviations when pressure increases from 0 to 5 GPa. The pressure derivatives (dνi/dP) of the 12 Raman frequencies are obtained at 0 GPa-5 GPa. The calculated results show that first-principles methods can well describe the high-pressure structural properties and Raman spectra of quartz. The combination of first-principles simulations of the Raman frequencies of minerals and Raman spectroscopy experiments is a useful tool for exploring the stress conditions within the Earth. Project supported by the Key Laboratory of Earthquake Prediction, Institute of Earthquake Science, China Earthquake Administration (CEA) (Grant No. 2012IES010201) and the National Natural Science Foundation of China (Grant Nos. 41174071 and 41373060).

  15. Biophotonics of skin: method for correction of deep Raman spectra distorted by elastic scattering

    NASA Astrophysics Data System (ADS)

    Roig, Blandine; Koenig, Anne; Perraut, François; Piot, Olivier; Gobinet, Cyril; Manfait, Michel; Dinten, Jean-Marc

    2015-03-01

    Confocal Raman microspectroscopy allows in-depth molecular and conformational characterization of biological tissues non-invasively. Unfortunately, spectral distortions occur due to elastic scattering. Our objective is to correct the attenuation of in-depth Raman peaks intensity by considering this phenomenon, enabling thus quantitative diagnosis. In this purpose, we developed PDMS phantoms mimicking skin optical properties used as tools for instrument calibration and data processing method validation. An optical system based on a fibers bundle has been previously developed for in vivo skin characterization with Diffuse Reflectance Spectroscopy (DRS). Used on our phantoms, this technique allows checking their optical properties: the targeted ones were retrieved. Raman microspectroscopy was performed using a commercial confocal microscope. Depth profiles were constructed from integrated intensity of some specific PDMS Raman vibrations. Acquired on monolayer phantoms, they display a decline which is increasing with the scattering coefficient. Furthermore, when acquiring Raman spectra on multilayered phantoms, the signal attenuation through each single layer is directly dependent on its own scattering property. Therefore, determining the optical properties of any biological sample, obtained with DRS for example, is crucial to correct properly Raman depth profiles. A model, inspired from S.L. Jacques's expression for Confocal Reflectance Microscopy and modified at some points, is proposed and tested to fit the depth profiles obtained on the phantoms as function of the reduced scattering coefficient. Consequently, once the optical properties of a biological sample are known, the intensity of deep Raman spectra distorted by elastic scattering can be corrected with our reliable model, permitting thus to consider quantitative studies for purposes of characterization or diagnosis.

  16. Effects of ion beam heating on Raman spectra of single-walled carbon nanotubes

    SciTech Connect

    Hulman, Martin; Skakalova, Viera; Krasheninnikov, A. V.; Roth, S.

    2009-02-16

    Free standing films of single-wall carbon nanotubes were irradiated with energetic N{sup +} and C{sup 4+} ions. The observed changes in the Raman line shape of the radial breathing mode and the G band of the C{sup 4+} irradiated samples were similar to those found for a thermally annealed sample. We ascribe these changes to thermal desorption of volatile dopants from the initially doped nanotubes. A simple geometry of the experiment allows us to estimate the temperature rise by one-dimensional heat conductance equation. The calculation indicates that irradiation-mediated increase in temperature may account for the observed Raman spectra changes.

  17. IR absorption and surface-enhanced Raman spectra of the isoquinoline alkaloid berberine

    NASA Astrophysics Data System (ADS)

    Strekal', N. D.; Motevich, I. G.; Nowicky, J. W.; Maskevich, S. A.

    2007-01-01

    We present the IR absorption and surface-enhanced Raman scattering (SERS) spectra of the isoquinoline alkaloid berberine adsorbed on a silver hydrosol and on the surface of a silver electrode for different potentials. Based on quantum chemical calculations, for the first time we have assigned the vibrations in the berberine molecule according to vibrational mode. The effect of the potential of the silver electrode on the geometry of sorption of the molecule on the surface is considered, assuming a short-range mechanism for enhancement of Raman scattering.

  18. Low-temperature Raman spectra of the 2-(α-methylbenzylamino)-5-nitropyridine crystal

    NASA Astrophysics Data System (ADS)

    Pinheiro, G. S.; Ferreira Júnior, M. N. G.; dos Santos, A. O.; Freire, P. T. C.; Lima, J. A., Jr.; Nogueira, C. E. S.; Cardoso, L. P.; Sherwood, J. N.; Remédios, C. M. R.

    2017-08-01

    The polar organic 2-(α-methylbenzylamino)-5-nitropyridine crystal (MBANP) has been studied by Raman spectroscopy at low temperatures (from 300 to 10 K). The effect of temperature change on the vibrational spectrum is discussed with the aid of DFT calculations. The behavior of the Raman spectra indicates that MBANP molecules present a different conformation at low temperatures associated with the rotation of the phenyl and pyridine rings. Temperature-dependent X-ray measurements and differential scanning calorimetry (DSC) analysis were utilized as complementary techniques to investigate the structural stability of MBANP crystal.

  19. Principal components analysis of FT-Raman spectra of ex vivo basal cell carcinoma

    NASA Astrophysics Data System (ADS)

    Martin, Airton A.; Bitar Carter, Renata A.; de Oliveira Nunes, Lilian; Loschiavo Arisawa, Emilia A.; Silveira, Landulfo, Jr.

    2004-07-01

    FT-Raman spectroscopy is a modern analytical tool and it is believed that its use for skin cancer diagnosis will lead to several advantages for patients, e.g., faster results and a minimization of invasivity. This article reports results of an ex Vivo study of the FT-Raman spectra regarding differentiation between non-diseased and malignant human skin lesions, Basal Cell Carcinoma (BCC). A Nd: YAG laser at 1064nm was used as the excitation source in the FT-Raman, RFS 100/S Spectrometer, Bruker. Thirty-nine sets of human skin samples, 18 histopathologically diagnosed as non-diseased, and 21 as BCC, were obtained during routine therapeutic procedures required by the primary disease. No sample preparation was needed to promote the FT-Raman spectra collection. The main spectral features, which may differentiate the sample, were found in the shift region of Amide I (1640 to 1680 cm-1), Amide III (1220 to 1330cm-1), proteins and lipids (1400 to 1500 cm-1), amino acids (939 to 940 cm-1) and deoxyribonucleic acid (1600 to 1620cm-1). Principal Components Analysis (PCA) was applied to FT-Raman spectra of Basal Cell Carcinoma. Analysis was performed on mean-normalized and mean-centered data of the non-diseased skin and BCC spectra. The dynamic loading of PCA was expanded into 2D contour by calculating a variance-covariance matrix. PCA was used to verify the statistical differences in the sample. This technique applied over all samples identified tissue type within 83% of sensitivity and 100% specificity. The PCA technique proved efficient for analysis in skin tissue ex vivo, results were significant and coherent.

  20. Raman and infrared spectra and theoretical calculations of dipicolinic acid, dinicotinic acid, and their dianions

    NASA Astrophysics Data System (ADS)

    McCann, Kathleen; Laane, Jaan

    2008-11-01

    The Raman and infrared spectra of dipicolinic acid (DPA) and dinicotinic acid (DNic) and their salts (CaDPA, Na 2DPA, and CaDNic) have been recorded and the spectra have been assigned. Ab initio and DFT calculations were carried out to predict the structures and vibrational spectra and were compared to the experimental results. Because of extensive intermolecular hydrogen bonding in the crystals of these molecules, the calculated structures and spectra for the individual molecules agree only moderately well with the experimental values. Theoretical calculations were also carried out for DPA dimers and DPA·2H 2O to better understand the intermolecular interactions. The spectra do show that DPA and its calcium salt, which are present in anthrax spores, can be distinguished from the very similar DNic and CaDNic.

  1. Chemical composition of matrix-embedded ternary II-VI nanocrystals derived from first- and second-order Raman spectra

    NASA Astrophysics Data System (ADS)

    Azhniuk, Yu. M.; Hutych, Yu. I.; Lopushansky, V. V.; Prymak, M. V.; Gomonnai, A. V.; Zahn, D. R. T.

    2016-12-01

    A one- and multiphonon Raman scattering study is performed for an extensive set of CdS1-xSex, Cd1-yZnyS, Cd1-yZnySe, and CdSe1-xTex nanocrystals to investigate the applicability of first- and second-order Raman spectra for the determination of the matrix-embedded ternary nanocrystal composition. For one-mode ternary systems both the LO and 2LO phonon frequencies in the Raman spectra are shown to be a good measure of the nanocrystal composition. For two-mode systems, the approaches based on the difference of the LO phonon frequencies (first-order Raman spectra) or double LO overtone and combination tone frequencies (second-order Raman spectra) as well as on the LO phonon band intensity ratios are analysed. The weak electron-phonon coupling in the II-VI nanocrystals and the polaron constant values for the nanocrystal sublattices are discussed.

  2. Modeling of the fundamental Raman and infrared CH stretching spectra of CHD{sub 2} picolines

    SciTech Connect

    Lapouge, C.; Cavagnat, D.

    1996-12-31

    The quasi-free internal rotation of the methyl group in the {alpha}, {Beta} and {gamma} CHD{sub 2} picolines leads to complex features observed in the Raman and infrared CH stretching spectra. A quantum theory has been developed to model these spectra, taking explicitly into account the coupling between the slow internal motion and the much faster CH stretching vibration. In the ground vibrational state (v=0), the effective potential of internal rotation is calculated by adding to the methyl rotation potential energy, the variation of the zero point vibrational energy during the internal motion, determined by ab-initio. In the CH stretching excited state, this effective potential is added to the CH stretching vibrational contribution, determined from the conformational dependence of the CH bond length. The CH transitions between the effective potentials in the ground (v=0) and the first excited (v=1) CH stretching states are then calculated to reconstruct the fundamental Raman and IR spectra. The Raman intensities are determined from simple Franck-Condom factors, and the IR intensities are calculated from dipole moment derivatives determined by ab-initio. The so calculated spectra agree well with the experimental ones.

  3. Femtosecond Raman spectra of cis-stilbene and trans-stilbene with isotopomers in solution

    NASA Astrophysics Data System (ADS)

    Dobryakov, A. L.; Ioffe, I.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A.

    2012-12-01

    Femtosecond stimulated Raman spectra of trans-stilbene (D0), its isotopomers D2, D10, D12, 13C2 and of cis-stilbene in hexane are measured in the ground (S0) and excited (S1) electronic states. The ground 13C2 and excited D12 spectra are presented for the first time; the excited cis-spectra differ substantially from previously published ones. S1 Raman bands of trans-stilbene are 20 cm-1 wide corresponding to ˜1 ps vibrational dephasing. For cis-stilbene the bands are broadened to 40 cm-1 reflecting a short excited-state lifetime of 0.3 ps, in agreement with transient absorption data. From a dynamic shift of the 1569 cm-1 band, pump-induced intramolecular cooling is estimated to be less than 20 K. Many S1 Raman lines are detected for the first time. Vibrational spectra are calculated at MP2/cc-pVTZ (for S0) and XMCQDPT2/cc-pVTZ (for S1) levels of theory. Experimental and computational results can be used for a re-evalution of Rice-Ramsberger-Kassel-Marcus (RRKM) predictions for this famous photoisomeration reaction.

  4. Femtosecond Raman spectra of cis-stilbene and trans-stilbene with isotopomers in solution.

    PubMed

    Dobryakov, A L; Ioffe, I; Granovsky, A A; Ernsting, N P; Kovalenko, S A

    2012-12-28

    Femtosecond stimulated Raman spectra of trans-stilbene (D0), its isotopomers D2, D10, D12, (13)C2 and of cis-stilbene in hexane are measured in the ground (S(0)) and excited (S(1)) electronic states. The ground (13)C2 and excited D12 spectra are presented for the first time; the excited cis-spectra differ substantially from previously published ones. S(1) Raman bands of trans-stilbene are 20 cm(-1) wide corresponding to ~1 ps vibrational dephasing. For cis-stilbene the bands are broadened to 40 cm(-1) reflecting a short excited-state lifetime of 0.3 ps, in agreement with transient absorption data. From a dynamic shift of the 1569 cm(-1) band, pump-induced intramolecular cooling is estimated to be less than 20 K. Many S(1) Raman lines are detected for the first time. Vibrational spectra are calculated at MP2/cc-pVTZ (for S(0)) and XMCQDPT2/cc-pVTZ (for S(1)) levels of theory. Experimental and computational results can be used for a re-evalution of Rice-Ramsberger-Kassel-Marcus (RRKM) predictions for this famous photoisomeration reaction.

  5. Calorimetry-Derived Composition Vectors to Resolve Component Raman Spectra in Phospholipid Phase Transitions.

    PubMed

    Kitt, Jay P; Bryce, David A; Harris, Joel M

    2016-07-01

    Multidimensional least squares analysis is a well-established technique for resolving component vibrational spectra from mixed samples or systems. Component resolution of temperature-dependent vibrational spectra is challenging, however, due to the lack of a suitable model for the variation in sample composition with temperature. In this work, analysis of temperature-dependent Raman spectra of lipid membranes is accomplished by using "concentration" vectors independently derived from enthalpy changes determined by differential scanning calorimetry. Specifically, the lipid-bilayer phase transitions of DMPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) are investigated through Raman spectra acquired from individual, optically trapped vesicles in suspension as a function of temperature. Heat capacity profiles of the same vesicle suspension are measured using differential scanning calorimetry and numerically integrated to generate enthalpy change curves of each phase transition, which are in turn used to construct composition vectors. Multidimensional least squares analysis optimized for a fit to these composition vectors allows resolution of the component spectra corresponding to gel, ripple, and liquid-crystalline phases of the DMPC. The quality of fit of the calorimetry-derived results is confirmed by unstructured residual differences between the data and the model, and a composition variation predicted by the resolved spectra that matches the calorimetry results. This approach to analysis of temperature-dependent spectral data could be readily applied in other areas of materials characterization, where one is seeking to learn about structural changes that occur through temperature-dependent phase transitions.

  6. Fluorescence and Raman spectra on surface of K9 glass by high fluence ultraviolet laser irradiation at 355 nm

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen; Huang, Jin; Geng, Feng; Zhou, Xiaoyan; Feng, Shiquan; Ren, Dahua; Cheng, Xinlu; Jiang, Xiaodong; Wu, Weidong; Zheng, Wanguo; Tang, Yongjian

    2013-11-01

    In order to explore the damage mechanisms of K9 glass irradiated by high energy density ultraviolet laser, laser-induced fluorescence and Raman spectra were investigated. Compared the fluorescence spectra of damaged area, undamaged area and sub-damaged area, it can be conclude that the fluorescence spectrum of sub-damaged area is different from the structure of the other two areas. Especially, the main peak of the spectra at 415 nm reveals the unique characteristics of K9 glass. The structure at the sub-damaged area enhances intensity of the Raman scattering spectra. Three peaks of the spectra at about 500 nm and two characteristic peaks at about 550 nm exhibit the characterization of damaged area. A peak of the Raman scattering spectra at 350 nm which related to water can be observed. The relationship between intensity of Raman scattering and laser intensity at 355 nm is investigated by confocal Raman microscopy. At sub-damage area, signal of Raman scattering is rather high and decreased dramatically with respect to energy density. The major band at about 1470 cm-1 sharpened and moved to higher frequency with densification. These phenomena demonstrate that the structure of sub-damaged area has some characterization compared with the damaged area. The investigation of defect induced fluorescence and Raman spectra on surface of K9 glass is important to explore the damage mechanisms of optical materials irradiated by ultraviolet laser irradiation at 355 nm.

  7. Hyper Raman spectra calculated in a time-dependent Hartree-Fock method

    NASA Astrophysics Data System (ADS)

    Mohammed, Abdelsalam; Ågren, Hans; Ringholm, Magnus; Thorvaldsen, Andreas J.; Ruud, Kenneth

    2012-10-01

    Hyper Raman scattering (HRS) of the benzonitrile (BN) and 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) molecules is studied by means of ab initio calculations. The computational procedure employs a recently developed methodology for the analytic calculations of frequency-dependent polarizability gradients of arbitrary order, including perturbation dependent basis sets. The result are compared to normal Raman scattering (NRS) and coherent anti-Stokes Raman scattering (CARS) that previously have been studied using the same technology. It is found that some suppressed or silent modes in CARS and NRS spectra are clearly seen in HRS, and that although under general excitation conditions the HRS intensities are much lower than for CARS and NRS, HRS provides complementary information useful for target identification.

  8. [Raman spectra and its application of graphite enclaves in nephrite-jades in Xiuyan, Liaoning].

    PubMed

    Qiu, Zhi-li; Jiang, Qi-yun; Luo, Han; Qin, She-cai; Li, Liu-fen

    2010-11-01

    Xiuyan, Liaoning was an important locality of jade material of the Red Mountain Culture in the Neolithic Age in Chinese history where there are two types of raw material of nephrite jades, namely gravel nephrite jade (Hemo Yu in Chinese) and old nephrite jade (Lao Yu in Chinese). In the present paper, Laser Raman spectrum technique was applied to analyze the graphite enclaves in the nephrite jades of the two types of materials. The results show that the graphite enclaves in the two types of jades have different characteristics of Raman spectra, indicating that they probably were formed under different geological conditions, or originated from different ore-forming periods or were exploited from different section of ore body. Hence, laser Raman spectrum technique could be used as a supplementary measure for nondestructive detection to determine the occurrence of jades.

  9. DFT simulations and vibrational analysis of FTIR and FT-Raman spectra of 2-amino-4-methyl benzonitrile.

    PubMed

    Dheivamalar, S; Silambarasan, V

    2012-10-01

    This work deals with the vibrational spectroscopy of 2-amino-4-methyl benzonitrile (AMB) by means of quantum chemical calculations. The mid and far FTIR and FT-Raman spectra were measured in the condensed state. Hartree-Fock (HF/6-31G(*)) and density functional theory (DFT, B3LYP/6-31G(*)) ab initio methods have been performed to interpret the observed vibrational spectra. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results of the calculations were applied to simulated infrared and Raman spectra of the title compound, which showed excellent agreement with the observed spectra.

  10. [Research on Raman spectra of oxalic acid during decarboxylation under high temperature and high pressure].

    PubMed

    Wang, Hui-yuan; Zheng, Hai-fei

    2012-03-01

    The present research studied the thermal stability of oxalic acid under high temperature and pressure and its in-situ transformation by Raman spectroscopy using a hydrothermal diamond anvil cell. Raman spectra allow the detection of ionic and covalent atomic aggregates through the acquisition of vibrational spectra that are characteristic of their structures and molecular bond types. The result showed that there was no change in characteristic vibrational Raman peaks of oxalic acid in the low-temperature stage. With the increase in temperature and pressure, the characteristic vibrational Raman peaks of oxalic acid became weaker and the peaks disappeared at a certain high temperature, and decarboxylation happened. Oxalic acid decomposes to produce CO2 and H2, according to the reaction: C2 H2O4-2CO2 + H2. It was found that the decarboxylation was highly related with pressure and that the decarboxylation would be hindered at high pressure. Decarboxylation of oxalic acid under high temperature and pressure showed a linear relationship between temperature and pressure. The data fitting generated the formula: P(MPa) = 12. 839T(K)-5 953.7, R2 = 0.99. The molar volume change of decarboxylation of oxalic acid can be described by deltaV(cm(-3) x mol(-1)) = 16.69-0.002P (MPa) + 0.005 2T(K), R = 0.99.

  11. [Study on the frontier orbital and Raman spectra of Aflatoxin B1 and isomer].

    PubMed

    Li, Tao; Tang, Yan-lin; Ling, Zhi-gang; Long, Zheng-wen

    2014-08-01

    Through computation, this paper obtained Aflatoxin B1 and its trans-isomer molecules stable structure which was rarely reported by the density functional theory(DFT) with B3LYP complex function and 6-311 + g(d, p) basis set. Through a single point calculations and geometry analysis, we know that the cis-structure is more stable than trans-structure. On the basis of this, Raman spectra of two molecules are calculated by the same method and basis set. compared with the Aflatoxin B1 cis-structure powder experimental Raman spectra, it was informed that numerical results with experimental results combined with a better. While 1582, 3065, 1626 means to take the strongest of the three peaks of cis-structure raman characteristics, 1616, 3065, 1659 cm(-1) is indicated for the strongest of the three peaks of trans-structure raman characteristics. Use the Hirshfeld atom division method combined with Multiwfn software to analyze the composition of frontier orbital based on optimization calculation, and it was informed that the electrophilic ability of two monlecules was stronger than the nucleophilic ability. The proportion of C1 atoms in LUMO orbital are respectively 21.48 percent, 20.62 percent by calculating, thus it is predicted that C1 atom is most main position spot depriving of the electronic in DNA to cause cancer. The above-mentioned research has certain theoretical directive significance in detection, transformation and toxicity inhibition of the cis-trans isomers.

  12. Remote Raman spectra of benzene obtained from 217 meters using a single 532 nm laser pulse.

    PubMed

    Chen, Teng; Madey, John M J; Price, Frank M; Sharma, Shiv K; Lienert, Barry

    2007-06-01

    This report describes a mobile Raman lidar system that has been developed for spectral measurements of samples located remotely at ranges of hundreds of meters. The performance of this system has been quantitatively verified in a lidar calibration experiment using a hard target of standardized reflectance. A new record in detection range was achieved for remote Raman systems using 532 nm laser excitation. Specifically, Raman spectra of liquid benzene were measured with an integration time corresponding to a single 532 nm laser pulse at a distance of 217 meters. The single-shot Raman spectra at 217 meters demonstrated high signal-to-noise ratio and good resolution sufficient for the unambiguous identification of the samples of interest. The transmitter consists of a 20 Hz Nd:YAG laser emitting at 532 nm and 1064 nm and a 178 mm telescope through the use of which allows the system to produce a focused beam at the target location. The receiver consists of a large custom telescope (609 mm aperture) and a Czerny-Turner monochromator equipped with two fast photomultiplier tubes.

  13. [Raman Spectra Study on Topochemistry in Miscanthus × giganteus Cell Walls During Dilute Acid Pretreatment].

    PubMed

    He, Chuan; Zhou, Xia; Yao, Chun-li; Xu, Feng

    2015-09-01

    Confocal Raman microspectroscopy (CRM) represents a powerful technique that can provide insights into topochemistry in lignocellulosic biomass cell wall. In this work, CRM was used to explore the impact of dilute acid (DA) pretreatment on the topochemistry of lignin and hydroxycinnamic acid (HCA) in the-fiber cell walls of Miscanthus × giganteus internode. Raman spectra extracted from different morphological regions of untreated fiber cell walls indicated the heterogeneous concentration of lignin and HCA. There is a companied trend between them, that is, regions where there is the higher lignin concentration have the higher concentration of HCA. When treated with DA, it was found that the intensity of 1600 cm(-1) (lignin) and 1170 cm(-1) (HCA) were decreased, which could be contributed to the partially removal of lignin and HCA. The removal rate in different morphological areas followed the decreasing order: secondary cell wall (SW) > compound middle lamella (CML) > cell corner middle lamella (CCML). The increase of the Raman band intensity ratio (1170/1600) indicated the preferential removal of lignin in the SW and CML as a result of DA pretreatment, while the constant of the ratio meant there is no preference between lignin and HCA in the CCML. The research will provide the deep understanding of the topochemistry of lignin and HCA at sub-cellular level during DA pretreatment, meanwhile, it also expands the application of Raman spectra in the research area of plant cell wall.

  14. Change of phonon Raman spectra with V trimerization in BaV10O15

    NASA Astrophysics Data System (ADS)

    Kanzaki, T.; Kubota, R.; Katsufuji, T.

    2012-04-01

    We investigated Raman scattering of BaV10O15, which exhibits a structural phase transition with V trimerization at Tc=123 K possibly dominated by the orbital ordering of V t2g states. It was found that phonon Raman spectra drastically change at Tc. According to the analysis of the phonon spectra based on the bond-polarizability model, the force constant of the V-V bond increases by 75% and the peak width is reduced by half below Tc. This result can be explained by the existence of disorder originating from orbital degrees of freedom above Tc, which is suppressed by the long-range orbital ordering below Tc.

  15. Pressure dependent Raman spectra used to validate DFT EOS of hexanitrostilbene (HNS)

    NASA Astrophysics Data System (ADS)

    Farrow, Darcie; Alam, Kathy; Martin, Laura; Wixom, Ryan

    2017-01-01

    Due to its thermal stability and low vapor pressure, Hexanitrostilbene (HNS) is often used in high-temperature or vacuum applications as a detonator explosive or in mild detonating fuse. Toward improving the accuracy of the equation of state used in hydrodynamic simulations of the performance of HNS, we have measured the spe ctra of this material under static pressure in a diamond anvil cell. Density functional theory calculations were used to simulate the pressure dependence of the Raman spectra along the Hugoniot and 300K isotherm for comparison and to aid in interpreting the data. We discuss changes in vibrational signatures of HNS under pressure, comparison with simulated spectra, and using this data as a basis for understanding future pulsed Raman measurements on dynamically compressed HNS samples.

  16. DSC and Raman spectra of α and β-Endosulfan plus 60/40 mixture

    NASA Astrophysics Data System (ADS)

    Schmidt, Walter F.; Nguyen, Julie K.; Qin, Jianwei; Kim, Moon S.; Mookherji, Swati; McConnell, Laura L.; Hapeman, Cathleen J.

    2013-05-01

    The symmetrical β-conformer of endosulfan has the identical chemical composition of the asymmetrical α-conformer, and both have very different melting/boiling points. The α- and β-isomer however have markedly different Raman spectra at each of 50°C, 75°C and 100°C. Moreover, the commercially available Raman spectra of the 60/40 (α-/β-) mixture at the same temperatures is discrete from either a- and b-isomer alone. Previous research demonstrated that at a- boiling point 110°C, β-conformer partially converts to α-. DSC curves of mixtures suggest thermal interactions and conformational changes occurs in BOTH α- and β-isomer at temperatures even 60°C lower than the liquid/gas phase transition.

  17. Spectral Signatures for the Classification of Microbial Species using Raman Spectra

    SciTech Connect

    Webb-Robertson, Bobbie-Jo M.; Bailey, Vanessa L.; Fansler, Sarah J.; Wilkins, Michael J.; Hess, Nancy J.

    2012-06-14

    In general, classification-based methods based on Confocal Raman microscopy are focused on targeted studies under which the spectral libraries are collected under controlled instrument parameters, which facilitate analyses via standard multivariate data analysis methods and cross-validation. We develop and compare approaches to combine spectra collected at different times and varying levels of spectral resolution into a single spectral library. We demonstrate these approaches on a relevant test case; the identification of microbial species from a natural environment.

  18. Low-frequency Raman spectra and fragility of imidazolium ionic liquids.

    PubMed

    Ribeiro, Mauro C C

    2010-07-14

    Raman spectra within the 5-200 cm(-1) range have been recorded as a function of temperature for different ionic liquids based on imidazolium cations. A correlation has been found between fragility and the temperature dependence of the strength of fast relaxational motions. Understanding quasielastic scattering as the relaxational contribution to ionic mean-squared displacement elucidates some effects on ionic liquids' fragility resulting from modifications in the chemical structure.

  19. Low-frequency Raman spectra and fragility of imidazolium ionic liquids

    SciTech Connect

    Ribeiro, Mauro C. C.

    2010-07-14

    Raman spectra within the 5-200 cm{sup -1} range have been recorded as a function of temperature for different ionic liquids based on imidazolium cations. A correlation has been found between fragility and the temperature dependence of the strength of fast relaxational motions. Understanding quasielastic scattering as the relaxational contribution to ionic mean-squared displacement elucidates some effects on ionic liquids' fragility resulting from modifications in the chemical structure.

  20. SIRS-SS: a system for simulating IR/Raman spectra. 1. Substructure/subspectrum correlation.

    PubMed

    Yao, J; Fan, B; Doucet, J P; Panaye, A; Yuan, S; Li, J

    2001-01-01

    An IR/RAMAN spectra simulation system is reported. The development of this software was based on the substructure/subspectrum relationships established for four different structural classes: small molecules, special fragments, atom-centered FRELs, and bond-centered FRELs (FREL: Fragment centered on an Environment which is Limited). Four corresponding knowledge-bases (now, at a pilot stage) are constructed from usual correlation charts or data analyses of large populations of compounds using data mining techniques.

  1. Raman spectra of probably shock-metamorphosed zircon in structures of the Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Kaulina, Tatiana; Nerovich, Luidmila; Lialina, Luidmila; Il'chenko, Vadim; Bocharov, Vladimir; Kunakkuzin, Evgeny

    2016-04-01

    Zircon crystals were studied by means of Raman spectroscopy from certain structures of the Kola Peninsula, for which impact events are expected according to geological and geochemical data: circular structure in Javrozersky area of the Tanaelv belt and granophyres of Jarva-Varaka layered massif of the Monchegorsky ore district. Zircons from anorthosites of the Javrozersky area showed some features of impact zircons: wavy extinction, blurred "aurora-like" CL image and a presence of additional bands in the Raman spectrum, which may indicate the presence of ZrSiO4 with the scheelite-type structure (reidite) surrounded by zircon material. Zircon crystals of Yavra-Varaka granophyres showed variation of Raman spectra from the core part of crystals with typical zircon Raman pattern to complete absence of spectral bands in the marginal parts and rims. There was also a transition zone between cores and marginal parts of crystals, where the Raman spectrum is "blurred". Such pattern may be associated with the transformation of crystalline zircon to diaplectic glass under the influence of shock metamorphism, since the Jarva-Varaka massif according to geological and geochemical data is compared with the Sudbury structure, for which impact origin is assumed. The work is supported by RSF grant N 16-17-10051.

  2. Continuous cell sorting in a flow based on single cell resonance Raman spectra.

    PubMed

    McIlvenna, David; Huang, Wei E; Davison, Paul; Glidle, Andrew; Cooper, Jon; Yin, Huabing

    2016-04-21

    Single cell Raman spectroscopy measures a spectral fingerprint of the biochemistry of cells, and provides a powerful method for label-free detection of living cells without the involvement of a chemical labelling strategy. However, as the intrinsic Raman signals of cells are inherently weak, there is a significant challenge in discriminating and isolating cells in a flowing stream. Here we report an integrated Raman-microfluidic system for continuous sorting of a stream of cyanobacteria, Synechocystis sp. PCC6803. These carotenoid-containing microorganisms provide an elegant model system enabling us to determine the sorting accuracy using the subtly different resonance Raman spectra of microorganism cultured in a (12)C or (13)C carbon source. Central to the implementation of continuous flow sorting is the use of "pressure dividers" that eliminate fluctuations in flow in the detection region. This has enabled us to stabilise the flow profile sufficiently to allow automated operation with synchronisation of Raman acquisition, real-time classification and sorting at flow rates of ca. <100 μm s(-1), without the need to "trap" the cells. We demonstrate the flexibility of this approach in sorting mixed cell populations with the ability to achieve 96.3% purity of the selected cells at a speed of 0.5 Hz.

  3. Manifestation of hydrogen bonds of aqueous ethanol solutions in the Raman scattering spectra

    SciTech Connect

    Dolenko, T A; Burikov, S A; Patsaeva, S V; Yuzhakov, V I

    2011-03-31

    Spectra of Raman scattering of light by aqueous ethanol solutions in the range of concentrations from pure water to 96% alcohol are studied. For water, 25%, and 40% solutions of ethanol in water, as well as for 96% alcohol the Raman spectra are measured at temperatures from the freezing point to nearly the boiling point. The changes in the shape of the stretching OH band are interpreted in terms of strengthening or weakening of hydrogen bonds between the molecules in the solution. The strongest hydrogen bonding of hydroxyl groups is observed at the ethanol content from 20 to 25 volume percent, which is explained by formation of ethanol hydrates of a definite type at the mentioned concentrations of alcohol. This is confirmed by means of the method of multivariate curve resolution, used to analyse the Raman spectra of aqueous ethanol solutions. With growing temperature the weakening of hydrogen bonding occurs in all studied systems, which consists in reducing the number of OH groups, linked by strong hydrogen bonds. (laser applications and other problems in quantum electronics)

  4. Time-dependent density functional methods for Raman spectra in open-shell systems.

    PubMed

    Aquino, Fredy W; Schatz, George C

    2014-01-16

    We present an implementation of a time-dependent density functional theory (TD-DFT) linear response module in NWChem for unrestricted DFT calculations and apply it to the calculation of resonant Raman spectra in open-shell molecular systems using the short-time approximation. The new source code was validated and applied to simulate Raman spectra on several doublet organic radicals (e.g., benzyl, benzosemiquinone, TMPD, trans-stilbene anion and cation, and methyl viologen) and the metal complex copper phthalocyanine. We also introduce a divide-and-conquer approach for the evaluation of polarizabilities in relatively large systems (e.g., copper phthalocyanine). The implemented tool gives comparisons with experiment that are similar to what is commonly found for closed-shell systems, with good agreement for most features except for small frequency shifts, and occasionally large deviations for some modes that depend on the molecular system studied, experimental conditions not being accounted in the modeling such as solvation effects and extra solvent-based peaks, and approximations in the underlying theory. The approximations used in the quantum chemical modeling include (i) choice of exchange-correlation functional and basis set; (ii) harmonic approximation used in the frequency analysis to determine vibrational normal modes; and (iii) short-time approximation (omission of nuclear motion effects) used in calculating resonant Raman spectra.

  5. Raman and IR Spectra of Ice Ih and Ice XI with an Assessment of DFT Methods.

    PubMed

    Liu, Yuan; Ojamäe, Lars

    2016-10-01

    IR and Raman spectroscopic technology can be directly used to identify the occurrence of ferroelectric ice XI in laboratory or extraterrestrial settings. The performance of 16 different DFT methods applied on the ice Ih, VIII, IX, and XI crystal phases are evaluated. Based on a selected DFT computational scheme, the IR and Raman spectra of ice Ih and XI are derived and compared. When comparing the spectra of ice Ih and ice XI, both IR and Raman, the librational vibrations are found to be the most affected by the proton ordering. The spectroscopic fingerprint of ice XI can be used to distinguish ferroelectric ice XI from ice Ih in the universe. Furthermore, the existence of only one kind of H-bond in ice Ih is demonstrated from the overlapping sub-spectra for different types of H-bonded pair configurations in 16 isomers of ice Ih, which provides an illustration to the historic debate on whether one or two kinds of H-bonds existed in ice.

  6. Residual stress and Raman spectra of laser deposited highly-tetrahedral-coordinated-amorphous-carbon films

    SciTech Connect

    Friedmann, T.A.; Siegal, M.P.; Tallant, D.R.; Simpson, R.L.; Dominguez, F.

    1994-05-01

    We are studying carbon thin films by using a pulsed excimer laser to ablate pyrolytic graphite targets to form highly tetrahedral coordinated amorphous carbon ({alpha}t-C) films. These films have been grown on room temperature p-type Si (100) substrates without the intentional incorporation of hydrogen. In order to understand and optimize the growth of {alpha}t-C films, parametric studies of the growth parameters have been performed. We have also introduced various background gases (H{sub 2}, N{sub 2} and Ar) and varied the background gas pressure during deposition. The residual compressive stress levels in the films have been measured and correlated to changes in the Raman spectra of the {alpha}t-C band near 1565 cm{sup {minus}1}. The residual compressive stress falls with gas pressure, indicating a decreasing atomic sp{sup 3}-bonded carbon fraction. We find that reactive gases such as hydrogen and nitrogen significantly alter the Raman spectra at higher pressures. These effects are due to a combination of chemical incorporation of nitrogen and hydrogen into the film as well as collisional cooling of the ablation plume. In contrast, films grown in non-reactive Ar background gases show much less dramatic changes in the Raman spectra at similar pressures.

  7. Effect of Principal Component Analysis Centering and Scaling on Classification of Mycobacteria from Raman Spectra.

    PubMed

    Hanson, Cynthia; Sieverts, Michael; Vargis, Elizabeth

    2016-11-25

    Raman spectroscopy has been used for decades to detect and identify biological substances as it provides specific molecular information. Spectra collected from biological samples are often complex, requiring the aid of data truncation techniques such as principal component analysis (PCA) and multivariate classification methods. Classification results depend on the proper selection of principal components (PCs) and how PCA is performed (scaling and/or centering). There are also guidelines for choosing the optimal number of PCs such as a scree plot, Kaiser criterion, or cumulative percent variance. The goal of this research is to evaluate these methods for best implementation of PCA and PC selection to classify Raman spectra of bacteria. Raman spectra of three different isolates of mycobacteria (Mycobacterium sp. JLS, Mycobacterium sp. KMS, Mycobacterium sp. MCS) were collected and then passed through PCA and linear discriminant analysis for classification. Principal component analysis implementation as well as PC selection was evaluated by comparing the highest possible classification accuracies against accuracies determined by PC selection methods for each centering and scaling option. Centered and unscaled data provided the best results when selecting PCs based on cumulative percent variance.

  8. Characterisation of Raman spectra of high purity olivine as a function of temperature and shock history.

    NASA Astrophysics Data System (ADS)

    Hibbert, R.; Price, M. C.; Burchell, M. J.; Cole, M. J.

    2014-04-01

    ExoMars' Raman Laser Spectrometer (RLS, [1], [2]) will be the first Raman spectrometer deployed on another planetary body. It is probable the rover will land on the ancient terrain (TBD) within transverse distance to several impact craters where the rocks are estimated to be >3 billion years old. These ancient terrains have been subjected to impacts, and work at Kent has shown such impacts result in modification of minerals and organics [3, 4] and can induce a loss of volatiles [5, 6, 7]. This highlights some problematic scenarios for the interpretation of Raman spectra collected by ExoMars: i) The spectra of impact generated minerals may be misinterpreted since their signatures have not been systematically characterised; ii) The materials produced by the degradation of organic (biologically significant) compounds during impact are unknown, and consequently may be overlooked as evidence for life; iii) Shocked hydrated minerals may be erroneously identified as anhydrous, since it is currently unknown whether there is a spectral difference between volatile rich minerals that have been shocked and their anhydrous counterparts. Our primary goal is therefore to study impact modification. Using the Light Gas Gun at Kent [8], we have shocked minerals under Martian conditions and compared their Raman spectra from before and after impact. Thus far, we have conducted experiments by a firing a buckshot of ~50 μm molybdenum spheres onto gem quality olivine (peridots, which have a very clean and consistent composition) and analysing the impact craters on the surface of the sample using Raman spectroscopy. Raman spectroscopy is generally regarded as a nondestructive technique, however, concentrated laser power can generate localised heating leading to devolatisation, crystalline changes, and even melting of the sample. This can lead to misinterpretation of spectral data (such as incorrect mineralogical composition). Therefore, we have also set out to study and quantify any

  9. Vibrational infrared and Raman spectra of polypeptides: Fragments-in-fragments within molecular tailoring approach

    NASA Astrophysics Data System (ADS)

    Sahu, Nityananda; Gadre, Shridhar R.

    2016-03-01

    The present work reports the calculation of vibrational infrared (IR) and Raman spectra of large molecular systems employing molecular tailoring approach (MTA). Further, it extends the grafting procedure for the accurate evaluation of IR and Raman spectra of large molecular systems, employing a new methodology termed as Fragments-in-Fragments (FIF), within MTA. Unlike the previous MTA-based studies, the accurate estimation of the requisite molecular properties is achieved without performing any full calculations (FC). The basic idea of the grafting procedure is implemented by invoking the nearly basis-set-independent nature of the MTA-based error vis-à-vis the respective FCs. FIF has been tested out for the estimation of the above molecular properties for three isomers, viz., β-strand, 310- and α-helix of acetyl(alanine)nNH2 (n = 10, 15) polypeptides, three conformers of doubly protonated gramicidin S decapeptide and trpzip2 protein (PDB id: 1LE1), respectively, employing BP86/TZVP, M06/6-311G**, and M05-2X/6-31G** levels of theory. For most of the cases, a maximum difference of 3 cm-1 is achieved between the grafted-MTA frequencies and the corresponding FC values. Further, a comparison of the BP86/TZVP level IR and Raman spectra of α-helical (alanine)20 and its N-deuterated derivative shows an excellent agreement with the existing experimental spectra. In view of the requirement of only MTA-based calculations and the ability of FIF to work at any level of theory, the current methodology provides a cost-effective solution for obtaining accurate spectra of large molecular systems.

  10. Vibrational infrared and Raman spectra of polypeptides: Fragments-in-fragments within molecular tailoring approach.

    PubMed

    Sahu, Nityananda; Gadre, Shridhar R

    2016-03-21

    The present work reports the calculation of vibrational infrared (IR) and Raman spectra of large molecular systems employing molecular tailoring approach (MTA). Further, it extends the grafting procedure for the accurate evaluation of IR and Raman spectra of large molecular systems, employing a new methodology termed as Fragments-in-Fragments (FIF), within MTA. Unlike the previous MTA-based studies, the accurate estimation of the requisite molecular properties is achieved without performing any full calculations (FC). The basic idea of the grafting procedure is implemented by invoking the nearly basis-set-independent nature of the MTA-based error vis-à-vis the respective FCs. FIF has been tested out for the estimation of the above molecular properties for three isomers, viz., β-strand, 310- and α-helix of acetyl(alanine)nNH2 (n = 10, 15) polypeptides, three conformers of doubly protonated gramicidin S decapeptide and trpzip2 protein (PDB id: 1LE1), respectively, employing BP86/TZVP, M06/6-311G**, and M05-2X/6-31G** levels of theory. For most of the cases, a maximum difference of 3 cm(-1) is achieved between the grafted-MTA frequencies and the corresponding FC values. Further, a comparison of the BP86/TZVP level IR and Raman spectra of α-helical (alanine)20 and its N-deuterated derivative shows an excellent agreement with the existing experimental spectra. In view of the requirement of only MTA-based calculations and the ability of FIF to work at any level of theory, the current methodology provides a cost-effective solution for obtaining accurate spectra of large molecular systems.

  11. Principal component analysis and analysis of variance on the effects of Entellan New on the Raman spectra of fibers.

    PubMed

    Yu, Marcia M L; Sandercock, P Mark L

    2012-01-01

    During the forensic examination of textile fibers, fibers are usually mounted on glass slides for visual inspection and identification under the microscope. One method that has the capability to accurately identify single textile fibers without subsequent demounting is Raman microspectroscopy. The effect of the mountant Entellan New on the Raman spectra of fibers was investigated to determine if it is suitable for fiber analysis. Raman spectra of synthetic fibers mounted in three different ways were collected and subjected to multivariate analysis. Principal component analysis score plots revealed that while spectra from different fiber classes formed distinct groups, fibers of the same class formed a single group regardless of the mounting method. The spectra of bare fibers and those mounted in Entellan New were found to be statistically indistinguishable by analysis of variance calculations. These results demonstrate that fibers mounted in Entellan New may be identified directly by Raman microspectroscopy without further sample preparation.

  12. [Study on the modified surface layers of the CIGS thin films by Raman spectra].

    PubMed

    Liu, Wei; Sun, Yun; Li, Feng-Yan; He, Qing; Li, Chang-Jian; Tian, Jian-Guo

    2007-04-01

    In the present paper, the properties of Cu(In(1-x) Ga(x)) Se2 (CIGS) thin film absorber materials for the solar cells obtained by selenization of the precursors with In-rich or CuGa-rich surface layers were studied by XRD, SEM and Raman spectra. The photovoltaic devices based on the absorbers were measured and analyzed by illuminated J-V curve subsequently. The performance of the device constructed by the absorbers obtained by selenization of the precursors with CuGa-rich surface layer was improved greatly compared to that with In-rich surface layer. Through Raman spectra measurement, it was found that the Raman peak of the A1 mode was shifted for the CuGa-rich one, which is verified that the band gap of the surface layers was elevated. Moreover the value of increased Ga contents within the surface region of films were calculated by the relation between the Raman shifts and the Ga contents. As a result, the devices based on the thin films with the elevated surface energy band by selenizing the precursors with the CuGa-rich surface layer improved further the V(oc) and FF by about 74 mV and 8% respectively compared to that of corresponding to the one with In-rich surface layers, so that the conversion efficiency of the photovoltaic devices based on these thin films with CuGa-rich surface layer was improved by up to 9.4%. Meanwhile Raman scattering spectroscopy has proven to be a very powerful and useful technique for the surface analysis of such thin film solar cell semiconducuor materials.

  13. Infrared and Raman spectra, conformations, ab initio calculations and spectral assignments of ethylmethyldichlorogermane

    NASA Astrophysics Data System (ADS)

    Klaeboe, Peter; Nielsen, Claus J.; Horn, Anne; Guirgis, Gamil A.; Wurrey, Charles J.

    2010-07-01

    Raman spectra of ethylmethyldichlorogermane (CH 3CH 2GeCl 2CH 3) as a liquid were recorded at 293 K and polarization data were obtained. Additional Raman spectra were recorded at various temperatures between 293 and 154 K, and intensity changes of certain bands with temperature were detected. The sample was also investigated as amorphous and crystalline solids on a cold finger of copper at 78 K. The infrared spectra have been studied as a vapour in the 4000-400 and 500-100 cm -1 regions and as amorphous and crystalline solids at 78 K. No Raman or infrared bands present in the liquid seemed to vanish completely upon crystallization, but considerable intensity changes were observed, indicating a partly crystallization. The compound exists a priori in two conformers, anti and gauche, and the experimental results suggest an equilibrium in which the anti conformer has 0.6 kJ mol -1 lower enthalpy than gauche in the liquid. In the partly crystalline solid, however, the results indicate gauche to be preferred in the crystal lattice. DFT/B3LYP, CBS-QB3 and G2 calculations were carried out indicating a conformational enthalpy difference Δ H( gauche- anti) between 0.8 and 1.5 kJ mol -1, somewhat higher than the experimental value. Vibrational frequencies, infrared and Raman intensities, and polarization ratios for the anti and gauche conformers were calculated. Anharmonic vibrational wavenumbers were derived in B3LYP/cc-pVTZ. In most cases these values gave a good agreement with the experimental results for the anti and gauche conformers.

  14. Improved Savitzky-Golay-method-based fluorescence subtraction algorithm for rapid recovery of Raman spectra.

    PubMed

    Chen, Kun; Zhang, Hongyuan; Wei, Haoyun; Li, Yan

    2014-08-20

    In this paper, we propose an improved subtraction algorithm for rapid recovery of Raman spectra that can substantially reduce the computation time. This algorithm is based on an improved Savitzky-Golay (SG) iterative smoothing method, which involves two key novel approaches: (a) the use of the Gauss-Seidel method and (b) the introduction of a relaxation factor into the iterative procedure. By applying a novel successive relaxation (SG-SR) iterative method to the relaxation factor, additional improvement in the convergence speed over the standard Savitzky-Golay procedure is realized. The proposed improved algorithm (the RIA-SG-SR algorithm), which uses SG-SR-based iteration instead of Savitzky-Golay iteration, has been optimized and validated with a mathematically simulated Raman spectrum, as well as experimentally measured Raman spectra from non-biological and biological samples. The method results in a significant reduction in computing cost while yielding consistent rejection of fluorescence and noise for spectra with low signal-to-fluorescence ratios and varied baselines. In the simulation, RIA-SG-SR achieved 1 order of magnitude improvement in iteration number and 2 orders of magnitude improvement in computation time compared with the range-independent background-subtraction algorithm (RIA). Furthermore the computation time of the experimentally measured raw Raman spectrum processing from skin tissue decreased from 6.72 to 0.094 s. In general, the processing of the SG-SR method can be conducted within dozens of milliseconds, which can provide a real-time procedure in practical situations.

  15. Discriminating model for diagnosis of basal cell carcinoma and melanoma in vitro based on the Raman spectra of selected biochemicals

    NASA Astrophysics Data System (ADS)

    Silveira, Landulfo; Silveira, Fabrício Luiz; Bodanese, Benito; Zângaro, Renato Amaro; Pacheco, Marcos Tadeu T.

    2012-07-01

    Raman spectroscopy has been employed to identify differences in the biochemical constitution of malignant [basal cell carcinoma (BCC) and melanoma (MEL)] cells compared to normal skin tissues, with the goal of skin cancer diagnosis. We collected Raman spectra from compounds such as proteins, lipids, and nucleic acids, which are expected to be represented in human skin spectra, and developed a linear least-squares fitting model to estimate the contributions of these compounds to the tissue spectra. We used a set of 145 spectra from biopsy fragments of normal (30 spectra), BCC (96 spectra), and MEL (19 spectra) skin tissues, collected using a near-infrared Raman spectrometer (830 nm, 50 to 200 mW, and 20 s exposure time) coupled to a Raman probe. We applied the best-fitting model to the spectra of biochemicals and tissues, hypothesizing that the relative spectral contribution of each compound to the tissue Raman spectrum changes according to the disease. We verified that actin, collagen, elastin, and triolein were the most important biochemicals representing the spectral features of skin tissues. A classification model applied to the relative contribution of collagen III, elastin, and melanin using Euclidean distance as a discriminator could differentiate normal from BCC and MEL.

  16. Discriminating model for diagnosis of basal cell carcinoma and melanoma in vitro based on the Raman spectra of selected biochemicals.

    PubMed

    Silveira, Landulfo; Silveira, Fabrício Luiz; Bodanese, Benito; Zângaro, Renato Amaro; Pacheco, Marcos Tadeu T

    2012-07-01

    Raman spectroscopy has been employed to identify differences in the biochemical constitution of malignant [basal cell carcinoma (BCC) and melanoma (MEL)] cells compared to normal skin tissues, with the goal of skin cancer diagnosis. We collected Raman spectra from compounds such as proteins, lipids, and nucleic acids, which are expected to be represented in human skin spectra, and developed a linear least-squares fitting model to estimate the contributions of these compounds to the tissue spectra. We used a set of 145 spectra from biopsy fragments of normal (30 spectra), BCC (96 spectra), and MEL (19 spectra) skin tissues, collected using a near-infrared Raman spectrometer (830 nm, 50 to 200 mW, and 20 s exposure time) coupled to a Raman probe. We applied the best-fitting model to the spectra of biochemicals and tissues, hypothesizing that the relative spectral contribution of each compound to the tissue Raman spectrum changes according to the disease. We verified that actin, collagen, elastin, and triolein were the most important biochemicals representing the spectral features of skin tissues. A classification model applied to the relative contribution of collagen III, elastin, and melanin using Euclidean distance as a discriminator could differentiate normal from BCC and MEL.

  17. Theoretical and experimental IR, Raman and NMR spectra in studying the electronic structure of 2-nitrobenzoates

    NASA Astrophysics Data System (ADS)

    Świsłocka, R.; Samsonowicz, M.; Regulska, E.; Lewandowski, W.

    2007-05-01

    The influence of lithium, sodium, potassium, rubidium and cesium on the electronic system of the 2-nitrobenzoic acid (2-NBA) was studied. Optimized geometrical structures of studied compounds were calculated by HF, B3PW91, B3LYP methods using 6-311++G ∗∗ basis set. The theoretical IR and NMR spectra were obtained. The vibrational (FT-IR, FT-Raman) and NMR ( 1H and 13C) spectra for 2-nitrobenzoic acid salts of alkali metals were also recorded. The assignment of vibrational spectra was done. Characteristic shifts of band wavenumbers and changes in band intensities along the metal series were observed. Good correlation between the wavenumbers of the vibrational bands in the IR and Raman spectra for 2-nitrobenzoates (2-NB) and ionic potential, electronegativity, atomic mass and affinity of metals were found. The chemical shifts of protons and carbons ( 1H, 13C NMR) in the series of studied alkali metal 2-nitrobenzoates were observed too. The calculated parameters were compared to experimental characteristic of studied compounds.

  18. Surface-enhanced Raman spectra of hemoglobin for esophageal cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Zhou, Xue; Diao, Zhenqi; Fan, Chunzhen; Guo, Huiqiang; Xiong, Yang; Tang, Weiyue

    2014-03-01

    Surface-enhanced Raman scattering (SERS) spectra of hemoglobin from 30 esophageal cancer patients and 30 healthy persons have been detected and analyzed. The results indicate that, there are more iron ions in low spin state and less in high for the hemoglobin of esophageal cancer patients than normal persons, which is consistent with the fact that it is easier to hemolyze for the blood of cancer patients. By using principal component analysis (PCA) and discriminate analysis, we can get a three-dimensional scatter plot of PC scores from the SERS spectra of healthy persons and cancer patients, from which the two groups can be discriminated. The total accuracy of this method is 90%, while the diagnostic specificity is 93.3% and sensitivity is 86.7%. Thus SERS spectra of hemoglobin analysis combined with PCA may be a new technique for the early diagnose of esophageal cancer.

  19. Density functional IR, Raman, and VCD spectra of halogen substituted β-lactams

    NASA Astrophysics Data System (ADS)

    Rode, Joanna E.; Dobrowolski, Jan Cz.

    2003-06-01

    Halogenoazetidinones are important as synthetic intermediates for preparation of halogen β-lactam (2-azetidinone) antibiotics and as building blocks for carbohydrates and amino acids. In this paper, we consider the influence of the halogen atom, substituted at the C4 position of the 2-azetidinone ring, on the geometry, IR, Raman, and vibrational circular dichroism spectra. The vibrational spectra were calculated for the chiral 4-( R)-X-2-azetidinone (X=F, Cl or Br) molecules at the B3PW91/aug-cc-pVTZ level. It was shown that the geometry of the molecules studied do not change much upon the change of the halogen atom. In case of the vibrational spectra, the position but even more the intensities depend strongly on the kind of halogen substituent.

  20. Influence of the coordination number Z on the micro-Raman spectra of ternary chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Iovu, M. S.; Iaseniuc, O. V.; Dinescu, D.; Enachescu, M.

    2016-12-01

    Chalcogenide glasses are attractive materials due to its application in photonics and optoelectronics. Chalcogenide glasses GexAsxSe1-2x (average coordination number Z=2.15÷2.90) and (As4S3Se3)1-xSnx (average coordination number Z=2.4÷2.56), which contain elements of IV group of the Periodic Table, such as Ge and Sn are important for a wide range of technical applications, such as infrared optical elements, acousto-optic and alloptical switching devices, holographic recording media, diffractive optics, photonic crystals, etc. [1, 2]. Raman spectroscopy is an efficient method for obtaining information on the local structure of the disordered material, especially when the composition is varied. In this paper are reported the Micro-Raman spectra of GexAsxSe1-2x and (As4S3Se3)1-xSnx bulk glasses and amorphous thin films. The Micro-Raman spectra of bulk glasses and thermally deposited amorphous (As4S3Se3)1-xSnx thin films consist of two broad bands located at around ν=236 cm-1 and ν=345 cm-1, which corresponds to the symmetric stretching vibration modes of AsSe3/2 and AsS3/2 pyramids, respectively. Tin impurities didn't change the shape of Micro-Raman spectra, but shift the both bands to low frequency region. The Micro-Raman spectra of bulk glasses and thermally deposited amorphous (GexAsxSe1-2x thin films consist of one main vibration band located at around ν=246 cm-1 for lower concentration of Ge and As, and is attributed to (AsSe1/2)3 pyramidal units. With increasing of Ge and As concentrations this band shifts to lower frequency region up to ν=236 cm-1 for x=0.30. The vibration band situated around ν=205 cm-1 is attributed to Ge(Se1/2)4 tetrahedral units and increase in the intensity with increasing of Ge and As concentrations. Some shoulders in high frequency regions at ν=365-390 cm-1 and ν=500-530 cm-1, caused by the presence of As-Se bands and Se-Se chains also was observed.

  1. Effects of heat treatment on Raman spectra of two-layer 12C/13C graphene.

    PubMed

    Kalbac, Martin; Frank, Otakar; Kavan, Ladislav

    2012-10-22

    The Raman spectra of two-layered graphene on a silicon substrate were studied in the temperature range from 298 to 1073 K in an inert atmosphere. Isotopic engineering was used to fabricate two-layer graphene specimens containing (13)C atoms in the top layer and (12)C atoms in the bottom layer, which allowed the behavior of each particular layer to be distinguished as a function of temperature. It is demonstrated that the top layer exhibits much lower Raman temperature coefficients than the bottom one for both the G and the G' modes. We suggest that the changes in the Raman spectra of graphene observed during thermal cycling are predominantly caused by a superposition of two effects, namely, the mechanical stress in graphene exerted by the substrate and the intrinsic changes in the graphene lattice caused by the temperature itself. The top graphene layer is proposed to be more relaxed than the bottom graphene layer and thus reflects almost exclusively the temperature variations as a freestanding graphene layer would.

  2. Infrared and Raman spectra, DFT-calculations and spectral assignments of 1,3,5-trisilacyclohexane

    NASA Astrophysics Data System (ADS)

    Andersen, Niels H.; Nielsen, Claus J.; Klaeboe, Peter; Guirgis, Gamil A.; Overby, Jason S.; Askarian, Sahand M.

    2014-11-01

    The infrared spectra of 1,3,5-trisilacyclohexane (c-C3H6Si3H6) as a vapour and liquid have been recorded. Raman spectra of the liquid have been studied and depolarization data were obtained. The compound exists in the stable form as a chair conformer with C3v symmetry, and additional conformers such as twist or cradle forms were not detected. The wavenumbers of the IR and Raman active vibrational modes were measured and their existence were supported by quantum chemical B3LYP/cc-pVTZ calculations in the harmonic approximation. The 11 totally symmetric A1 and 16 doubly degenerate E fundamentals were assigned on the basis of the infrared vapour contours and intensities and upon the Raman intensities and depolarization measurements. Quantum chemistry calculations support the assignments: an average relative deviation between observed and calculated wavenumbers of 2.2% was obtained employing scaling of the harmonic B3LYP/cc-pVTZ force field, which was reduced to 1.4% in the anharmonic calculations.

  3. Comparison between IR absorption and raman scattering spectra of liquid and supercritical 1-butanol.

    PubMed

    Sokolova, Maia; Barlow, Stephen J; Bondarenko, Galina V; Gorbaty, Yuri E; Poliakoff, Martyn

    2006-03-23

    Raman spectra of 1-butanol have been obtained at a constant pressure of 500 bar up to 350 degrees C and along isotherms 250, 300, and 350 degrees C up to 600 bar. The purpose of the experiment was to compare responses of Raman and IR absorption spectroscopy to the forming of O-H...O bonds in alcohols. As a result, some important inferences were drawn from the experiment. In particular, it has been estimated quantitatively how the intensity of Raman scattering in the region of the OH band depends on the extent of hydrogen bonding. As might be expected, the dependence is much weaker than in the case of the IR absorption. As was shown, the ratio of integrated intensities of bonded molecules in the absorption and scattering spectra is a constant and does not depend on temperature and density. The effect of cooperativity of hydrogen bonds is confirmed. It was also found that even at high pressures, a noticeable amount of nonbonded molecules exists at room temperature.

  4. Principal component analysis of Raman spectra for TiO2 nanoparticle characterization

    NASA Astrophysics Data System (ADS)

    Ilie, Alina Georgiana; Scarisoareanu, Monica; Morjan, Ion; Dutu, Elena; Badiceanu, Maria; Mihailescu, Ion

    2017-09-01

    The Raman spectra of anatase/rutile mixed phases of Sn doped TiO2 nanoparticles and undoped TiO2 nanoparticles, synthesised by laser pyrolysis, with nanocrystallite dimensions varying from 8 to 28 nm, was simultaneously processed with a self-written software that applies Principal Component Analysis (PCA) on the measured spectrum to verify the possibility of objective auto-characterization of nanoparticles from their vibrational modes. The photo-excited process of Raman scattering is very sensible to the material characteristics, especially in the case of nanomaterials, where more properties become relevant for the vibrational behaviour. We used PCA, a statistical procedure that performs eigenvalue decomposition of descriptive data covariance, to automatically analyse the sample's measured Raman spectrum, and to interfere the correlation between nanoparticle dimensions, tin and carbon concentration, and their Principal Component values (PCs). This type of application can allow an approximation of the crystallite size, or tin concentration, only by measuring the Raman spectrum of the sample. The study of loadings of the principal components provides information of the way the vibrational modes are affected by the nanoparticle features and the spectral area relevant for the classification.

  5. Raman spectra of cubic and amorphous Ge2Sb2Te5 from first principles

    NASA Astrophysics Data System (ADS)

    Sosso, Gabriele C.; Caravati, Sebastiano; Mazzarello, Riccardo; Bernasconi, Marco

    2011-04-01

    We computed the Raman spectrum of cubic and amorphous Ge2Sb2Te5 (GST) by ab initio phonons and an empirical bond polarizability model. Models of the amorphous phase were generated by quenching from the melt by means of ab initio molecular dynamics simulations. The calculated spectra are in good agreement with experimental data which confirms the reliability of the models of the amorphous phase emerged from the simulations. All the features of the spectrum in both crystalline and amorphous GST can be assigned to vibrations of defective octahedra. The calculations reveal that the polarizability of the Sb-Te is much higher than that of Ge-Te bonds and of Ge-Ge/Sb wrong bonds resulting in a much lower Raman response of tetrahedra which are made of Ge-Te and wrong bonds. As a consequence and as opposed to amorphous GeTe, the signatures of tetrahedra in the Raman spectrum of amorphous GST are hidden by the larger Raman cross section of defective octahedra.

  6. Microwave spectra and conformational studies of ethylamine from temperature dependent Raman spectra of xenon solutions and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Darkhalil, Ikhlas D.; Nagels, Nick; Herrebout, Wouter A.; van der Veken, Benjamin J.; Gurusinghe, Ranil M.; Tubergen, Michael J.; Durig, James R.

    2014-06-01

    FT-microwave spectroscopy was carried out where the trans conformer was identified to be the most stable conformer. Variable temperature (-60 to -100 °C) studies of the Raman spectra (4000-50 cm-1) of ethylamine, CH3CH2NH2 dissolved in liquefied xenon have been carried out. From these data both conformers have been identified and their relative stabilities obtained. The enthalpy difference has been determined to be 62 ± 6 cm-1 (0.746 ± 0.072 kJ mol-1) with the trans conformer the more stable form. The percentage of the gauche conformer is estimated to be 60% at ambient temperature. The conformational stabilities have been predicted from ab initio calculations with the Møller-Plesset perturbation method to the second order (MP2(full)) and the fourth order (MP4(SDTQ)) as well as with density functional theory by the B3LYP method by utilizing a variety of basis sets. Vibrational assignments have been made for the observed bands which have been predicted by MP2(full)/6-31G(d) ab initio calculations which includes harmonic force fields, frequencies, infrared intensities, Raman activities and depolarization ratios for both conformers. The results are discussed and compared to the corresponding properties of some similar molecule.

  7. Evaluation of the state of active ingredients in pharmaceutical preparations using fourier transform-Raman difference spectra.

    PubMed

    Mifune, Masaki; Iwasaki, Toshinobu; Kozaki, Yukari; Tsukamoto, Ikuko; Saito, Madoka; Kitamura, Youji; Yamaguchi, Toshikazu; Saito, Yutaka

    2006-12-01

    To examine the pharmaceutical application of Fourier transform (FT)-Raman spectroscopy, the state of active pharmaceutical ingredients (APIs) in a preparation of several forms was evaluated by investigating the Raman difference spectra between the preparation and excipient. The difference spectra indicated that APIs in alacepril tablets, caffeine sustained-release granules, and quinidine sulfate granules remained unchanged after the manufacturing process. However, the state of sparfloxacin in nanoparticles changed, although it remained unchanged in tablets or powders. These results show that the FT-Raman difference spectrum is expected to be utilized in the field of quality control of crystalline pharmaceutical preparations.

  8. Calculation of the lattice dynamics and Raman spectra of copper zinc tin chalcogenides and comparison to experiments

    NASA Astrophysics Data System (ADS)

    Khare, Ankur; Himmetoglu, Burak; Johnson, Melissa; Norris, David J.; Cococcioni, Matteo; Aydil, Eray S.

    2012-04-01

    The electronic structure, lattice dynamics, and Raman spectra of the kesterite, stannite, and pre-mixed Cu-Au (PMCA) structures of Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) were calculated using density functional theory (DFT). Differences in longitudinal and transverse optical (LO-TO) splitting in kesterite, stannite, and PMCA structures can be used to differentiate them. The Γ-point phonon frequencies, which give rise to Raman scattering, exhibit small but measurable shifts, for these three structures. Experimentally measured Raman scattering from CZTS and CZTSe thin films were examined in light of DFT calculations and deconvoluted to explain subtle shifts and asymmetric line shapes often observed in CZTS and CZTSe Raman spectra. Raman spectroscopy in conjunction with ab initio calculations can be used to differentiate between kesterite, stannite, and PMCA structures of CZTS and CZTSe.

  9. Raman Spectra of Deuterated Potassium Dihydrogen Phosphate Crystals with Different Degrees of Deuteration

    NASA Astrophysics Data System (ADS)

    Liu, Bao-An; Zhou, Hai-Liang; Zhang, Qing-Hua; Xu, Ming-Xia; Ji, Shao-Hua; Zhu, Li-Li; Zhang, Li-Song; Liu, Fa-Fu; Sun, Xun; Xu, Xin-Guang

    2013-06-01

    The polarized Raman spectra of deuterated potassium dihydrogen phosphate crystals with different deuterium concentrations are measured. With the increasing deuterium concentration, the Raman peaks which are assigned as the internal vibrations of the (H/D)2PO-4 anion shift to lower wavenumbers. This red-shift contributes to the decrease in the bonding force of the P—O bond as a result of the substitution of deuterium for hydrogen. Moreover, the intensity of the strongest peak of these crystals decreases first, and reaches the minimum value while the mole percentage of the deuterium content in the crystal is about 74%. After that, the intensity increases with the increase of the deuterium concentration in the crystal.

  10. Low-frequency isotropic and anisotropic Raman spectra of aromatic liquids.

    PubMed

    Heisler, Ismael A; Meech, Stephen R

    2010-05-07

    The Raman spectra below 300 wavenumbers of six different aromatic molecular liquids have been measured with a time and polarization resolved optical Kerr effect technique. The isotropic and anisotropic contributions were determined to yield the complete third order response, and thus a more detailed description of the microscopic liquid dynamics. The anisotropic contributions accurately reproduced previously published results. Both the isotropic and anisotropic Raman spectral densities shift toward lower frequencies with decreasing molecular weights. The first moment of the isotropic spectral densities scales linearly with the inverse square root of the molecular weight, which is consistent with interaction-induced dynamics in these liquids being driven mainly by motions with a translational character. Also, the isotropic spectral densities could be fit to a single Bucaro-Litovitz function. The exponent delta of this function increases monotonically with the inverse square root of the molecular weight. A possible physical origin of this behavior is discussed.

  11. Raman spectra of biomarkers of relevance to analytical astrobiological exploration: hopanoids, sterols and steranes.

    PubMed

    Edwards, H G M; Herschy, B; Page, K; Munshi, T; Scowen, I J

    2011-01-01

    The aim of this work is to investigate the viability and potential of three groups of organic compounds as biomarkers in a future robotic analytical exploration of Mars. The three compounds have been identified as suitable candidates for potential biomarkers for extant or extinct life from the terrestrial fossil record. The three groups of compound were all similar in structure, being either tetra- or penta-cyclic compounds. The limits of detection for a sample were also tested to estimate what concentrations it would still be amenable to Raman spectroscopic investigation. This was investigated using both solid mixtures and liquid solutions. The spectra of these compounds are characterised so that they can be added to the Raman database for future Mars missions. This involved identifying functional group characteristics, assigning peaks for each individual sample and characteristic features which would categorise the samples.

  12. Phase Transition in all-trans-β-Carotene Crystal: Temperature-Dependent Raman Spectra.

    PubMed

    da Silva, Kleber J R; Paschoal, Waldomiro; Belo, Ezequiel A; Moreira, Sanclayton G C

    2015-09-24

    In this study, we studied the stability of an all-trans-β-carotene single crystal using Raman spectroscopy with line excitation at 632.8 nm, in the temperature range 20–300 K. The Raman spectra exhibit clear modifications in the spectral range of the lattice and internal vibrational modes. The temperature dependence of the most intense vibrational modes ν1 (1511 cm(–1)) and ν2 (1156 cm(–1)) that are related to the C═C and C—C stretching vibrations of the polyene chain, respectively, shows an upward shift on the Raman modes. This behavior is similar to that stated in the theoretical work of Wei-Long Liu et al. We conclude that the all-trans-β-carotene crystal undergoes a temperature-induced phase transition at approximately 219 K. This transition is interpreted as a rotation experienced by β-ring groups at each end of the all-trans-β-carotene molecule around the dihedral angle. At low temperatures, the new molecular configuration affects the sliding plane of the space group C2h(5)(P2(1)/n), and the phase transition leads to an unchanged monoclinic structure; however, the original space group is possibly lowered to the space group C2. In the temperature range 200–220 K, the spectral ratio (S) of the integrated intensities of the spectral modes around the symmetric and asymmetric stretching wavenumbers of the methyl group (CH3) changes as a function of temperature in agreement with the phase transition. Furthermore, according to phase transition undergone by the all-trans-β-carotene, the thermal results obtained by differential scanning calorimetry show an exothermic process that occurs near the transition temperature assigned by the Raman spectra.

  13. Kernel principal component analysis residual diagnosis (KPCARD): An automated method for cosmic ray artifact removal in Raman spectra.

    PubMed

    Li, Boyan; Calvet, Amandine; Casamayou-Boucau, Yannick; Ryder, Alan G

    2016-03-24

    A new, fully automated, rapid method, referred to as kernel principal component analysis residual diagnosis (KPCARD), is proposed for removing cosmic ray artifacts (CRAs) in Raman spectra, and in particular for large Raman imaging datasets. KPCARD identifies CRAs via a statistical analysis of the residuals obtained at each wavenumber in the spectra. The method utilizes the stochastic nature of CRAs; therefore, the most significant components in principal component analysis (PCA) of large numbers of Raman spectra should not contain any CRAs. The process worked by first implementing kernel PCA (kPCA) on all the Raman mapping data and second accurately estimating the inter- and intra-spectrum noise to generate two threshold values. CRA identification was then achieved by using the threshold values to evaluate the residuals for each spectrum and assess if a CRA was present. CRA correction was achieved by spectral replacement where, the nearest neighbor (NN) spectrum, most spectroscopically similar to the CRA contaminated spectrum and principal components (PCs) obtained by kPCA were both used to generate a robust, best curve fit to the CRA contaminated spectrum. This best fit spectrum then replaced the CRA contaminated spectrum in the dataset. KPCARD efficacy was demonstrated by using simulated data and real Raman spectra collected from solid-state materials. The results showed that KPCARD was fast (<1 min per 8400 spectra), accurate, precise, and suitable for the automated correction of very large (>1 million) Raman datasets.

  14. Sensitivity of Raman spectra excited at 325 nm to surface treatments of undoped polycrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Ghodbane, S.; Deneuville, A.; Tromson, D.; Bergonzo, P.; Bustarret, E.; Ballutaud, D.

    2006-08-01

    About 20 m thick films were deposited in the same run by MPCVD at 900 °C on Si substrates and then hydrogenated in situ during 30 min with a hydrogen plasma at the same temperature. Their surfaces were kept as prepared or more or less strongly oxidized by annealing at 600 °C under ambient atmosphere or by sulphochromic acid or aqua regia treatments. Raman spectra were excited at 325 and 632.8 nm. Spectra of the as-prepared sample exhibit structures around 2835 and 2895 cm-1 from monohydride carbon-hydrogen ascribed to the atomically flat (111) and (100) areas, respectively, on the facets of the sample surface crystallites. The decrease of these structures in the normalized spectra after the various oxidation treatments confirms these assignments. The decrease is smaller for the aqua regia treatment than for the two other treatments which give similar effects. Other Raman signals from sp2 C around 1589 cm-1 and CHx bonds around 2930, 2952, 3025 and 3050 cm-1 originate from species at the surface and within the films. Their variation with the oxidizing treatments indicates a significant contribution from the surface species.

  15. Raman spectra from Symmetric Hydrogen Bonds in Water by High-intensity Laser-induced Breakdown

    PubMed Central

    Men, Zhiwei; Fang, Wenhui; Li, Dongfei; Li, Zhanlong; Sun, Chenglin

    2014-01-01

    Raman spectra of ice VII and X were investigated using strong plasma shockwave generated by laser-induced breakdown (LIB) in liquid water. Simultaneously, the occurrence of the hydrogen emission lines of 656 nm (Hα), 486 nm (Hβ), 434 nm (Hγ) and 410 nm (Hδ) was observed. At 5 × 1012 W/cm2 optical power density, the O-H symmetric stretching, translational and librational modes of ice VII and a single peak at 785 cm−1 appeared in the spectra. The band was assigned to the Raman-active O-O mode of the monomolecular phase, which was the symmetric hydrogen bond of cuprite ice X. The spectra indicated that ice VII and X structure were formed, as the trajectory of the strong plasma shockwave passes through the stable Pressure-Temperature range of ice VII and X. The shockwave temperature and pressure were calculated by the Grüneisen model. PMID:24709652

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

    PubMed

    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.

  17. Mineralogical analyses of surface sediments in the Antarctic Dry Valleys: coordinated analyses of Raman spectra, reflectance spectra and elemental abundances.

    PubMed

    Bishop, Janice L; Englert, Peter A J; Patel, Shital; Tirsch, Daniela; Roy, Alex J; Koeberl, Christian; Böttger, Ute; Hanke, Franziska; Jaumann, Ralf

    2014-12-13

    Surface sediments at Lakes Fryxell, Vanda and Brownworth in the Antarctic Dry Valleys (ADV) were investigated as analogues for the cold, dry environment on Mars. Sediments were sampled from regions surrounding the lakes and from the ice cover on top of the lakes. The ADV sediments were studied using Raman spectra of individual grains and reflectance spectra of bulk particulate samples and compared with previous analyses of subsurface and lakebottom sediments. Elemental abundances were coordinated with the spectral data in order to assess trends in sediment alteration. The surface sediments in this study were compared with lakebottom sediments (Bishop JL et al. 2003 Int. J. Astrobiol. 2, 273-287 (doi:10.1017/S1473550403001654)) and samples from soil pits (Englert P et al. 2013 In European Planetary Science Congress, abstract no. 96; Englert P et al. 2014 In 45th Lunar and Planetary Science Conf., abstract no. 1707). Feldspar, quartz and pyroxene are common minerals found in all the sediments. Minor abundances of carbonate, chlorite, actinolite and allophane are also found in the surface sediments, and are similar to minerals found in greater abundance in the lakebottom sediments. Surface sediment formation is dominated by physical processes; a few centimetres below the surface chemical alteration sets in, whereas lakebottom sediments experience biomineralization. Characterizing the mineralogical variations in these samples provides insights into the alteration processes occurring in the ADV and supports understanding alteration in the cold and dry environment on Mars. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  18. Collision-induced Raman spectra of Hg-rare gas Van der Waals complexes

    NASA Astrophysics Data System (ADS)

    Borysow, A.; Grycuk, T.

    1982-10-01

    An absolute differential scattering cross section is calculated for the Hg-rare gas and pure Hg Van der Waals quasimolecules, taking into account both the free state and bound state contributions to the depolarized Raman spectra of these systems. The calculations are performed using the Maitland-Smith (MS) potential function fitted to available experimental data and assuming the simple dipole-induced dipole (DID) model of anisotropy of the polarizability tensor of a collisional atomic pair. The obtained cross sections are about 100 times greater than those for the pure rare gas calculated and measured by Frommhold et al.

  19. Absorption and resonance Raman spectra of Pb2, Pb3 and Pb4 in xenon matrices

    NASA Technical Reports Server (NTRS)

    Stranz, D. D.; Khanna, R. K.

    1980-01-01

    Lead metal was vaporized and trapped in solid xenon at 12K. Electronic absorption and resonance Raman spectra were recorded of the resulting matrix, which was shown to contain Pb2, Pb3, and possibly Pb4 molecular species. The vibrational frequency for Pb2 is determined to be 108/cm for the ground state, with a dissociation energy of 82000/cm. Ad3h symmetry is indicated for the Pb3 species, with nu sub 1=117/cm and nu sub 2 = 96 /cm. The existence of Pb4 is suggested by a fundamental and overtone of 111/cm spacing.

  20. Influence of SOP modes on Raman spectra of ZnO(Fe) nanoparticles

    NASA Astrophysics Data System (ADS)

    Hadžić, B.; Romčević, N.; Romčević, M.; Kuryliszyn-Kudelska, I.; Dobrowolski, W.; Narkiewicz, U.; Sibera, D.

    2015-04-01

    Nanocrystaline samples of ZnO(Fe) were synthesized by traditional wet chemical method followed by calcinations. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, ZnFe2O4 and Fe2O3) and the mean crystalline size (from 8 to 51 nm). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm-1) with surface optical phonons (SOP) in range of 500-550 cm-1. The phonon of registered phase's exhibit effects connected to phase concentration, while the SOP phonon mode exhibit significant confinement effect.

  1. Raman Optical Activity Spectra for Large Molecules through Molecules-in-Molecules Fragment-Based Approach.

    PubMed

    Jovan Jose, K V; Raghavachari, Krishnan

    2016-02-09

    We present an efficient method for the calculation of the Raman optical activity (ROA) spectra for large molecules through the molecules-in-molecules (MIM) fragment-based method. The relevant higher energy derivatives from smaller fragments are used to build the property tensors of the parent molecule to enable the extension of the MIM method for evaluating ROA spectra (MIM-ROA). Two factors were found to be particularly important in yielding accurate results. First, the link-atom tensor components are projected back onto the corresponding host and supporting atoms through the Jacobian projection method, yielding a mathematically rigorous method. Second, the long-range interactions between fragments are taken into account by using a less computationally expensive lower level of theory. The performance of the MIM-ROA model is calibrated on the enantiomeric pairs of 10 carbohydrate benchmark molecules, with strong intramolecular interactions. The vibrational frequencies and ROA intensities are accurately reproduced relative to the full, unfragmented, results for these systems. In addition, the MIM-ROA method is employed to predict the ROA spectra of d-maltose, α-D-cyclodextrin, and cryptophane-A, yielding spectra in excellent agreement with experiment. The accuracy and performance of the benchmark systems validate the MIM-ROA model for exploring ROA spectra of large molecules.

  2. Using Separable Nonnegative Matrix Factorization Techniques for the Analysis of Time-Resolved Raman Spectra

    NASA Astrophysics Data System (ADS)

    Luce, R.; Hildebrandt, P.; Kuhlmann, U.; Liesen, J.

    2016-09-01

    The key challenge of time-resolved Raman spectroscopy is the identification of the constituent species and the analysis of the kinetics of the underlying reaction network. In this work we present an integral approach that allows for determining both the component spectra and the rate constants simultaneously from a series of vibrational spectra. It is based on an algorithm for non-negative matrix factorization which is applied to the experimental data set following a few pre-processing steps. As a prerequisite for physically unambiguous solutions, each component spectrum must include one vibrational band that does not significantly interfere with vibrational bands of other species. The approach is applied to synthetic "experimental" spectra derived from model systems comprising a set of species with component spectra differing with respect to their degree of spectral interferences and signal-to-noise ratios. In each case, the species involved are connected via monomolecular reaction pathways. The potential and limitations of the approach for recovering the respective rate constants and component spectra are discussed.

  3. Using Separable Nonnegative Matrix Factorization Techniques for the Analysis of Time-Resolved Raman Spectra.

    PubMed

    Luce, Robert; Hildebrandt, Peter; Kuhlmann, Uwe; Liesen, Jörg

    2016-09-01

    The key challenge of time-resolved Raman spectroscopy is the identification of the constituent species and the analysis of the kinetics of the underlying reaction network. In this work we present an integral approach that allows for determining both the component spectra and the rate constants simultaneously from a series of vibrational spectra. It is based on an algorithm for nonnegative matrix factorization that is applied to the experimental data set following a few pre-processing steps. As a prerequisite for physically unambiguous solutions, each component spectrum must include one vibrational band that does not significantly interfere with the vibrational bands of other species. The approach is applied to synthetic "experimental" spectra derived from model systems comprising a set of species with component spectra differing with respect to their degree of spectral interferences and signal-to-noise ratios. In each case, the species involved are connected via monomolecular reaction pathways. The potential and limitations of the approach for recovering the respective rate constants and component spectra are discussed.

  4. Spectra and structure of organogermanes. XXII. Microwave, infrared, and Raman spectra of methylgermyl cyanide

    SciTech Connect

    Durig, J.R.; Mohamad, A.B.; Attia, G.M.; Li, Y.S.; Cradock, S.

    1985-07-01

    The microwave spectra have been recorded from 18.0 to 26.5 GHz for /sup 12/CH/sub 3/GeH/sub 2//sup 12/C/sup 14/N, /sup 13/CH/sub 3/GeH/sub 2//sup 12/C/sup 14/N, /sup 12/CH/sub 3/GeH/sub 2//sup 12/C/sup 15/N, /sup 12/CH/sub 3/GeH/sub 2//sup 13/C/sup 14/N, /sup 12/CH/sub 3/GeD/sub 2//sup 12/C/sup 14/N, and /sup 12/CD/sub 3/GeH/sub 2//sup 12/C/sup 14/N of the four naturally occurring isotopes of germanium: /sup 70/Ge, /sup 72/Ge, /sup 74/Ge, and /sup 76/Ge. Only a-type transitions were observed and R-branch assignments have been made for all the isotopic species in the ground vibrational state from which the rotational constants were determined. From these data the complete structural parameters were determined to be r/sub 0/(C/sub ME/--Ge) = 1.933 +- 0.002 A, r(Ge--C/sub CN/) = 1.927 +- 0.004 A, r(CequivalentN) = 1.155 +- 0.004 A, r(Ge--H) = 1.521 +- 0.001 A, r(C--H/sub s/) = 1.092 +- 0.005 A, r(C--H/sub a/) = 1.092 +- 0.005 A, arcCGeC = 107.36/sup 0/ +- 0.60/sup 0/, arcHGeH = 111.41/sup 0/ +- 0.04/sup 0/, arcHGeC/sub Me/ = 112.92/sup 0/ +- 0.08/sup 0/, arcH/sub s/CGe = 109.5/sup 0/ +- 2.0/sup 0/, and

  5. Experimental and theoretical IR and Raman spectra of picolinic, nicotinic and isonicotinic acids

    NASA Astrophysics Data System (ADS)

    Koczoń, P.; Dobrowolski, J. Cz.; Lewandowski, W.; Mazurek, A. P.

    2003-07-01

    The experimental and theoretical (B3PW91/6-311++G**) vibrational (IR and Raman) spectra of picolinic, nicotinic and isonicotinic acids (pyridine-2-, -3-, and -4-carboxylic acid, respectively) were studied. Three stable calculated structures were found for picolinic acid: the structure with intramolecular hydrogen COOH⋯N bond, and the two without hydrogen bond. For the nicotinic acid two stable theoretical structures differ in orientation of the COOH group with respect to the nitrogen atom, whereas for the isonicotinic acid only one form was stable. The theoretical vibrational spectra of the three acids were interpreted by means of potential energy distributions (PEDs) using VEDA 3 program. Next, selected experimental bands were assigned based on the scaled theoretical wavenumbers. Finally, the wavenumbers and intensities for the three isomeric acids were compared and discussed in terms of location of the carboxylic group.

  6. FT-IR and FT-Raman spectra of cimetidine and its metallocomplexes

    NASA Astrophysics Data System (ADS)

    Barańska, M.; Proniewicz, L. M.

    1999-11-01

    We present vibrational spectra of three stable, well-reproducible, polymorphic forms of cimetidine ( cim), a drug which is a powerful histamine H 2-receptor antagonist used in the treatment of peptic ulcer and the Zollinger-Ellison syndrome. Assignments of Raman and IR bands are made using semiempirical methods: MNDO, AM1 and PM3. We also describe the synthesis of Me( cim) 2(ClO 4) 2, where Me=Cu(II), Cd(II), Co(II) and Ni(II), and present their vibrational data. We show that the obtained complexes are isostructural, however a metal ion that occupies a center of octahedral unit introduces some distortions that can be seen in the spectra. We also make tentative assignment of metal-ligand stretching modes observed in low frequency range.

  7. Raman spectra of gases. XVI - Torsional transitions in ethanol and ethanethiol

    NASA Technical Reports Server (NTRS)

    Durig, J. R.; Bucy, W. E.; Wurrey, C. J.; Carreira, L. A.

    1975-01-01

    The Raman spectra of gaseous ethanol and ethanethiol have been investigated. Thiol torsional fundamentals for the gauche conformer of EtSH and EtSD have been observed and the asymmetric potential function for this vibration has been calculated. Methyl torsional transitions and overtones have also been observed for both of these molecules. Barriers to internal rotation for the methyl top are calculated to be 3.77 and 3.84 kcal/mol for the EtSH and EtSD compounds, respectively. Hydroxyl torsional fundamentals were observed at 207 and 170 per cm in the EtOH and EtOD spectra, respectively. Overtones of the methyl torsion in both molecules yield a barrier to internal rotation of 3.62 kcal/mol for the gauche conformer.

  8. Polarization dependence of tip-enhanced Raman and plasmon-resonance Rayleigh scattering spectra

    NASA Astrophysics Data System (ADS)

    Kitahama, Yasutaka; Uemura, Shohei; Katayama, Ryota; Suzuki, Toshiaki; Itoh, Tamitake; Ozaki, Yukihiro

    2017-06-01

    Tip-enhanced Raman scattering (TERS) spectroscopy has high sensitivity and high spatial resolution, although it shows low reproducibility due to the variable optical properties of the tips. In the present study, polarized scattering spectra of localized surface plasmon resonance (LSPR) at the apex of the tip induced by conventional dark field illumination were compared with the corresponding TERS spectra, generated by excitation using polarization not only parallel and perpendicular to the tip, but also vertical to the sample plane (z-polarization). The polarization-dependence of LSPR was consistent with that of the TERS. Thus, the optical properties of the tip can be easily optimized before TERS measurement by excitation polarization that induces the largest LSPR signal.

  9. Real-space pseudopotential study of vibrational properties and Raman spectra in Si-Ge core-shell nanocrystals

    NASA Astrophysics Data System (ADS)

    Bobbitt, N. Scott; Chelikowsky, James R.

    2016-03-01

    We examine the vibrational properties and Raman spectra of Si-Ge core-shell nanostructures using real-space pseudopotentials constructed within density functional theory. Our method uses no empirical parameters, unlike many popular methods for predicting Raman spectra for nanocrystals. We find the dominant features of the Raman spectrum for the Si-Ge core-shell structure to be a superposition of the Raman spectra of the Ge and Si nanocrystals with optical peaks around 300 and 500 cm-1, respectively. We also find a Si-Ge "interface" peak at 400 cm-1. The Ge shell causes the Si core to expand from the equilibrium structure. This strain induces significant redshift in the Si contribution to the vibrational and Raman spectra, while the Ge shell is largely unstrained and does not exhibit this shift. We find that the ratio of peak heights is strongly related to the relative size of the core and shell regions. This finding suggests that Raman spectroscopy may be used to characterize the size of the core and shell in these structures.

  10. NIR Raman spectra of whole human blood: effects of laser-induced and in vitro hemoglobin denaturation.

    PubMed

    Lemler, P; Premasiri, W R; DelMonaco, A; Ziegler, L D

    2014-01-01

    Care must be exercised in the use of Raman spectroscopy for the identification of blood in forensic applications. The Raman spectra of dried whole human blood excited at 785 nm are shown to be exclusively due to oxyhemoglobin or related hemoglobin denaturation products. Raman spectra of whole blood are reported as a function of the incident 785-nm-laser power, and features attributable to heme aggregates are observed for fluences on the order of 10(4) W/cm(2) and signal collection times of 20 s. In particular, the formation of this local-heating-induced heme aggregate product is indicated by a redshifting of several heme porphyrin ring vibrational bands, the appearance of a large broad band at 1,248 cm(-1), the disappearance of the Fe-O2 stretching and bending bands, and the observation of a large overlapping fluorescence band. This denaturation product is also observed in the low-power-excitation Raman spectrum of older ambient-air-exposed bloodstains (2 weeks or more). The Raman spectrum of methemoglobin whole blood excited at 785 nm is reported, and increasing amounts of this natural denaturation product can also be identified in Raman spectra of dried whole blood particularly when the blood has been stored prior to drying. These results indicate that to use 785-nm-excitation Raman spectra as an identification method for forensic applications to maximum effect, incident laser powers need to be kept low to eliminate variable amounts of heme aggregate spectral components contributing to the signal and the natural aging process of hemoglobin denaturation needs to be accounted for. This also suggests that there is a potential opportunity for 785-nm-excitation Raman spectra to be a sensitive indicator of the age of dried bloodstains at crime scenes.

  11. [Research on Raman spectra of isooctane at ambient temperature and ambient pressure to 1. 2 GPa].

    PubMed

    Zhang, Fei-fei; Zheng, Hai-fei

    2012-03-01

    The experimental study of the Raman spectral character for liquid isooctane (2,2,4-trimethylpentane, ATM) was con ducted by moissanite anvil cell at the pressure of 0-1.2 GPa and the ambient temperature. The results show that the Raman peaks of the C-H stretching vibration shift to higher frenquencies with increasing pressures. The relations between the system pressure and peaks positions is given as following: v2 873 = 0.002 8P+2 873.3; v2 905 = 0.004 8P+2 905.4; v2 935 = 0.002 7P+ 2 935.0; v2 960 = 0.012P+2 960.9. The Raman spectra of isooctane abruptly changed at the pressure about 1.0 GPa and the liquid-solid phase transition was observed by microscope. With the freezing pressure at ambient temperature and the melting temperature available at 1 atm, the authors got the liquid-solid phase diagram of isooctane. According to Clapeyron equation, the authors obtained the differences of volume and entropy for the liquid-solid phase transition of isooctane: deltaV(m) = 4.46 x 10(-6) m3 x mol-1 and deltaS = -30.32 J x K(-1) x mol(-1).

  12. Geometry and Raman spectra of P.R. 255 and its furo-furanone analogue

    NASA Astrophysics Data System (ADS)

    Luňák, Stanislav, Jr.; Frumarová, Božena; Vyňuchal, Jan; Hrdina, Radim

    2009-05-01

    Fourier transform Raman spectra of two π-isoelectronic compounds 3,6-diphenyl-2,5-dihydro-pyrrolo-[3,4-c]pyrrole-1,4-dione (BPPB, C.I. Pigment Red 255) and 3,6-diphenyl-2,5-dihydro-furo-[3,4-c]furanone (BFFB) with the same 1,4-diphenyl-buta-1,3-diene (DPB) backbone were first time measured in polycrystalline phase. The ground state geometry and vibrational frequencies together with Raman intensities were computed by density functional theory (DFT: B3LYP/6-311G++(d,p)). All intensive observed Raman frequencies were identified as totally symmetric. The difference of carbon-carbon bond lengths of BPPB and BFFB compared to DPB, relating very well with the shifts of C dbnd C and C-C stretching modes frequencies, was explained by aromatization of central butadiene unit bounded in diketo-pyrrolo-pyrrole and furo-furanone heterocycles. A strong coupling of modes was observed for BFFB enhancing selectively the intensity of one peak 1593 cm -1 in C dbnd C stretching region and one peak 1372 cm -1 in C-C stretching region. C dbnd O stretching and N-H bending modes of BPPB are significantly affected by intermolecular hydrogen bonding.

  13. Pressure-Tuning Raman Spectra of Diiodine Thioamide Compounds: Models for Antithyroid Drug Activity

    PubMed Central

    Corban, Ghada J.; Antoniadis, Constantinos; Hadjikakou, Sotiris K.; Hadjiliadis, Nick; Meng, Jin-Fang; Butler, Ian S.

    2006-01-01

    The pressure-tuning Raman spectra of five solid, diiodine heterocyclic thioamide compounds (mbztS)I2 (mbztS = N-methyl-2-mercaptobenzothiazole) (1); [(mbztS)2I]+[I7]− (2); (pySH)I2 (pySH = 2-mercaptopyridine) (3); [(pySH)(pyS]+[I3]− (4); (thpm)(I2)2 or possibly [(thpm)I2]+[I3]− (thpm = 2-mercapto-3,4,5,6-tertahydropyrimidine (5) have been measured for pressures up to ∼ 50 kbar using a diamond-anvil cell. Compounds 1, 4, and 5 undergo pressure-induced phase transitions at ∼ 35, ∼ 25, and ∼ 32 kbar, respectively. Following the phase transition in 1, the pressure dependences of the vibrational modes, which were originally located at 84, 111, and 161 cm−1 and are associated with the S⋯I–I linkage, are 2.08, 1.78, and 0.57 cm−1/kbar, respectively. These pressure dependences are typical of low-energy vibrations. The pressure-tuning FT-Raman results for the pairs of compounds 1 , 2, 3, and 4 are remarkably similar to each other suggesting that the compounds are most probably perturbed diiodide compounds rather than ionic ones. The Raman data for 5 show that it is best formulated as (thpm)(I2)2 rather than [(thpm)2I]+[I3]−. PMID:17497015

  14. Experimental and theoretical studies on IR, Raman, and UV-Vis spectra of quinoline-7-carboxaldehyde.

    PubMed

    Kumru, M; Küçük, V; Kocademir, M; Alfanda, H M; Altun, A; Sarı, L

    2015-01-05

    Spectroscopic properties of quinoline-7-carboxaldehyde (Q7C) have been studied in detail both experimentally and theoretically. The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)), dispersive-Raman (3500-50 cm(-1)), and UV-Vis (200-400 nm) spectra of Q7C were recorded at room temperature (25 °C). Geometry parameters, potential energy surface about CCH(O) bond, harmonic vibrational frequencies, IR and Raman intensities, UV-Vis spectrum, and thermodynamic characteristics (at 298.15K) of Q7C were computed at Hartree-Fock (HF) and density functional B3LYP levels employing the 6-311++G(d,p) basis set. Frontier molecular orbitals, molecular electrostatic potential, and Mulliken charge analyses of Q7C have also been performed. Q7C has two stable conformers that are energetically very close to each other with slight preference to the conformer that has oxygen atom of the aldehyde away from the nitrogen atom of the quinoline.

  15. Multivariate analysis of Raman spectra for in vitro non-invasive studies of living cells

    NASA Astrophysics Data System (ADS)

    Notingher, Ioan; Jell, Gavin; Notingher, Petronela L.; Bisson, Isabelle; Tsigkou, Olga; Polak, Julia M.; Stevens, Molly M.; Hench, Larry L.

    2005-06-01

    Understanding the biochemical and biophysical properties of live cells is fundamental for unravelling the secrets of many diseases and developing new therapies. Raman micro-spectroscopy is a powerful non-invasive technique that allows in vitro studies of individual living cells or groups of cells without the use of any labels or contrast enhancing chemicals. We describe the use of various multivariate statistical methods, such as Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Classical Least Square (CLS) fitting, to extract biochemical information related to various cellular events. Such methods are required because of the high complexity of the Raman spectra obtained from living cells. PCA and LDA are used to discriminate between healthy and tumor cells. A leave-one-out cross-validation method indicated high prediction accuracy (95%) in identification of tumorogenic bone cells. The CLS fitting method using commercially available biopolymers makes it possible to monitor biochemical changes during the differentiation of embryonic stem cells and foetal bone cells. The results suggest that in both cases differentiated cells are characterised by lower concentrations of RNA compared to undifferentiated cells. These studies suggest that Raman micro-spectroscopy could become an invaluable tool for in vitro cellular biochemistry studies.

  16. Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate ( struvite) and its isomorphous analogues. I. Spectra of protiated and partially deuterated magnesium potassium phosphate hexahydrate

    NASA Astrophysics Data System (ADS)

    Stefov, V.; Šoptrajanov, B.; Spirovski, F.; Kuzmanovski, I.; Lutz, H. D.; Engelen, B.

    2004-02-01

    The Fourier transform infrared and Raman spectra of magnesium potassium phosphate hexahydrate and a series of its deuterated analogues were recorded and analyzed. By comparing the spectra recorded at room temperature with those obtained at the boiling temperature of liquid nitrogen and by studying the spectra of the series of partially deuterated MgKPO 4·H 2O an assignment was proposed for the observed bands. The unusual behavior for bands originating from the ν4 modes of PO 43- ions in the Raman spectra of partially deuterated analogues of MgKPO 4·6H 2O was explained by coupling and mixing of the ν4(PO 4) mode and D 2O librations.

  17. Importance of backbone angles versus amino acid configurations in peptide vibrational Raman optical activity spectra

    NASA Astrophysics Data System (ADS)

    Herrmann, Carmen; Ruud, Kenneth; Reiher, Markus

    2008-01-01

    In this work, we investigate whether the differential scattering of right- and left-circularly polarized light in peptide Raman optical activity spectra are uniquely dominated by the backbone conformation, or whether the configurations of the individual amino acid also play a significant role. This is achieved by calculating Raman optical activity spectra using density functional theory for four structurally related peptides with a common backbone conformation, but with different sequences of amino acid configurations. Furthermore, the ROA signals of the amide normal modes are decomposed into contributions from groups of individual atoms. It is found that the amino acid configuration has a considerable influence on the ROA peaks in the amide I, II, and III regions, although the local decomposition reveals that the side-chain atoms only contribute to those peaks directly in the case of the amide II vibrations. Furthermore, small changes in the amide normal modes may lead to large and irregular modifications in the ROA intensity differences, making it difficult to establish transferable ROA intensity differences even for structurally similar vibrations.

  18. Tracking of the polyproline folding by density functional computations and Raman optical activity spectra.

    PubMed

    Profant, Václav; Baumruk, Vladimír; Li, Xiaojun; Safařík, Martin; Bouř, Petr

    2011-12-22

    Polyprolines offer many opportunities to study factors influencing peptide and protein folding and structure. Longer chains can adopt two well-defined forms (PPI and PPII), but shorter peptides are quite flexible. To understand in detail the dependence of the secondary structure on the length and the interplay between the side chain and main chain conformation, zwitterionic (Pro)(N) models (with N = 2, 3, 4, 6, 9, 12 and longer inhomogeneous chains) were studied by a combination of the Raman and Raman optical activity (ROA) spectroscopy with the density functional theory (DFT). Potential surfaces were systematically explored for the shorter oligoprolines, and Boltzmann conformational ratios were obtained both for the main chain and the proline ring puckering. The predictions were verified by comparison of the experimental and simulated ROA spectra. The conformer ratios extracted from a decomposition of the experimental ROA into scaled computed spectra well reproduced Boltzmann populations calculated from relative energies. For example, an "A" puckering of the proline ring was found prevalent, relatively independent of the length, whereas the cis-amide backbone form adopted by shorter peptides rapidly disappeared for N > 4. The results are consistent with previous NMR and vibrational circular dichroism (VCD) data. Delocalized exciton vibrations along the peptide chain often enhance the ROA signal, and can thus be used to indicate a longer regular peptide structure. The ROA technique appeared to be very sensitive to the ring puckering; less distinct spectral features were produced by changes in the main chain geometry.

  19. Theoretical study of NMR, infrared and Raman spectra on triple-decker phthalocyanines

    SciTech Connect

    Suzuki, Atsushi; Oku, Takeo

    2016-02-01

    Electronic structures and magnetic properties of multi-decker phthalocyanines were studied by theoretical calculation. Electronic structures, excited processes at multi-states, isotropic chemical shifts of {sup 13}C, {sup 14}N and {sup 1}H-nuclear magnetic resonance (NMR), principle V-tensor in electronic field gradient (EFG) tensor and asymmetry parameters (η), vibration mode in infrared (IR) and Raman spectra of triple-decker phthalocyanines were calculated by density functional theory (DFT) and time-dependent DFT using B3LYP as basis function. Electron density distribution was delocalized on the phthalocyanine rings with electron static potential. Considerable separation of chemical shifts in {sup 13}C, {sup 14}N and {sup 1}H-NMR was originated from nuclear spin interaction between nitrogen and carbon atoms, nuclear quadrupole interaction based on EFG and η of central metal under crystal field. Calculated optical absorption at multi-excited process was derived from overlapping π-orbital on the phthalocyanine rings. The vibration modes in IR and Raman spectra were based on in-plane deformation and stretching vibrations of metal-ligand coordination bond on the deformed structure.

  20. Lidar-measured atmospheric N₂ vibrational-rotational Raman spectra and consequent temperature retrieval.

    PubMed

    Liu, Fuchao; Yi, Fan

    2014-11-17

    We have built a spectrally resolved Raman lidar to measure atmospheric N₂ Stokes vibrational-rotational Raman spectra. The lidar applies a double-grating polychromator with a reciprocal linear dispersion of ~0.12 nm mm(-1) for the wavelength separation and a 32-channel linear-array photomultiplier tube for sampling the spectral signals. The lidar can together measure the individual S- and O-branch line signals from J = 0 (2) through 14 (16). A comparison shows an excellent agreement between the lidar-measured and theoretically-calculated spectra. Based on the signal ratio of two individual lines (e.g., S-branch J = 6 and 12), the atmospheric temperature profiles are derived without requiring a calibration from another reference temperature. In terms of the envelope shape of an even-J section of the measured S-branch lines, we have also developed a new temperature retrieval approach without needing a calibration from reference temperature data. Both the approaches can give rise to reasonable temperature profiles comparable to that from local radiosonde.

  1. The VA, VCD, Raman and ROA spectra of tri-L-serine in aqueous solution.

    PubMed

    Jürgensen, V Würtz; Jalkanen, K

    2006-02-22

    The structures of one conformer of the nonionic neutral and zwitterionic species of L-serinyl L-serinyl L-serine (SSS or tri-L-serine), together with its cationic and anionic species and the capped N-acetyl tri-L-serine N'-methylamide analog were optimized with density functional theory with the Becke 3LYP hybrid exchange correlation (XC) functional and the PW91 GGA XC functional and the 6-31G* and aug-cc-pVDZ basis sets. Subsequently, the vibrational absorption, vibrational circular dichroism, Raman and Raman optical activity spectra were simulated in order to compare them to experimentally measured spectra. In addition, we compare to previously reported studies for both structural determination and spectral simulations and measurements. A comparison of the various ways to treat the effects of the environment and solvation on both the structure and the spectral properties is thoroughly investigated for one conformer, with the goal to determine which level of theory is appropriate to use in the systematic search of the conformational space. In addition, the effects of the counterion, here Cl- anion, are also investigated. Here we present the current state of the art in nanobiology, where the latest methods in experimental and theoretical vibrational spectroscopy are used to gain useful information about the coupling of the nuclear, electronic and magnetic degrees of freedom and structure of tri-L-serine and its capped peptide analog with the environment.

  2. Polarization properties, high-order Raman spectra, and frequency asymmetry between Stokes and anti-Stokes scattering of Raman modes in a graphite whisker

    NASA Astrophysics Data System (ADS)

    Tan, Pingheng; Hu, Chengyong; Dong, Jian; Shen, Wanci; Zhang, Baofa

    2001-12-01

    The Raman spectra of a new type of graphite whiskers have been measured in the range of 150-7800 cm-1. The intensity of the overtone (2D) located at ~2700 cm-1 is found to be about 10 times stronger than that of the C-C stretching mode (G) at 1582 cm-1. Because of the peculiar enhancement of the 2D mode, high-order Raman bands up to fifth order at ~7500 cm-1 have been observed. Polarized micro-Raman spectroscopy has been performed on an individual graphite whisker, and angular-dependent intensity measurements of all Raman modes in the VV and HV geometries are in agreement with the theoretical calculated results. Laser-energy-dependent dispersion effects and the frequency discrepancy of Raman modes between their Stokes and anti-Stokes lines in graphite whiskers are also carefully investigated. The energy dispersion of the D mode and G mode is very similar to that of highly oriented pyrolytic graphite (HOPG). In contrast to the Raman spectra of HOPG and other graphite materials, two laser-energy-dependent Raman lines are revealed in the low-frequency region of the Raman spectra of graphite whiskers, which are believed to be the resonantly enhanced phonons in the transverse-acoustic and longitudinal-acoustic phonon branches. Moreover, the obvious energy dispersion of the D' mode at ~1620 cm-1 is observed in graphite whiskers. The results clearly reveal how strongly the peak parameters of Raman modes of graphite materials are dependent on their structural geometry. The Stokes and anti-Stokes scattering experiments show that the frequency discrepancy between the Stokes and anti-Stokes sides of a Raman mode in graphite materials is equal to the frequency value covered by the one-phonon energy of this Raman mode in its frequency versus laser energy curve, which is the product of the one-phonon energy of this mode (Eωs) and the value of its laser-energy dispersions (∂Eωs/∂ɛL).

  3. [Raman spectra and structure analysis of 2,6-pyridine dicarboxylic acid in different states and single Bacillus spore].

    PubMed

    Huang, Rong-shao; Huang, Xi; Xu, Lan-lan; Li, Yong-qing; Huang, Shu-shi

    2011-03-01

    The Raman spectra of 2,6-pyridine dicarboxylic acid (DPA) and their calcium salts(Ca-DPA) in different states and the Ca-DPA in a single bacterial spore have been recorded by laser tweezers Raman system (LTRS) and the spectra have been assigned. Raman spectra of different states of DPA and Ca-DPA are different evidently. Analysis leading to differences in the structure of spectrum may be due to that the Raman spectra of DPA crystalline reflected more precise characteristics information compared to DPA powder, in which the laser can penetrate through DPA crystalline and the Raman scatter from the crystalline interior is greater than that from DPA powder. The second reason is that DPA powder and Ca-DPA crystalline contain water molecules, and the intermolecular hydrogen bonding in the crystals of these molecules is extensive. The presence of calcium ions would affect the pyridine ring so that both sides of the carboxyl pyridine ring have a certain geometric deformation and the hydroxy carboxylic was damaged. The DPA2-anion is principal in Ca-DPA and the DPA solution. The calcium ion affects the stability of the pyridine ring structure in the Ca-DPA solution. The result from the spectra also showed that the DPA in single spores present Ca-DPA crystal state.

  4. Vibrational features of confined water in nanoporous TiO2 by Raman spectra

    NASA Astrophysics Data System (ADS)

    Xin, Gao; Qiang, Wang; Gang, Sun; Chen-Xi, Li; Lin, Hu

    2016-02-01

    Raman spectra of confined water adsorbed in nanoporous TiO2 are obtained in experiment. TiO2 samples with different pore diameters under different humidity conditions are investigated. The results indicate that the symmetric vibrational mode of water molecule is destroyed when relative humidity decreases. This indicates that the interaction between water molecules and surface of TiO2 becomes stronger when the distance between water molecules and surface turns smaller, and the interaction plays a major role in depressing the symmetric vibrational peak. The spectra of confined water in TiO2 and Vycor are compared. When filling fractions are the same, their spectra show distinctions no matter whether they are in partial filling condition or in full filling condition. The spectra of HDO confined in TiO2 with different filling fractions are compared with each other. There is no clear distinction among their vibrational peaks, and the peaks mainly relate to asymmetric vibration. Therefore, the interaction between water molecules and the wall of pore decouples the symmetric vibrational mode only, and the influences on asymmetric vibrational mode show little differences among different filling fractions. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304049 and 11264006), the Guizhou Provincial Science and Technology Foundation, China (Grant No. J[2010]2132), and the Doctor Funds of Guizhou University, China (Grant No. [2012] 020).

  5. Multivariate statistical analysis of Raman spectra to distinguish normal, tumor, lymph nodes and mastitis in mouse mammary tissues

    NASA Astrophysics Data System (ADS)

    Dai, H.; Thakur, J. S.; Serhatkulu, G. K.; Pandya, A. K.; Auner, G. W.; Naik, R.; Freeman, D. C.; Naik, V. M.; Cao, A.; Klein, M. D.; Rabah, R.

    2006-03-01

    Raman spectra ( > 680) of normal mammary gland, malignant mammary gland tumors, and lymph node tissues from mice injected with 4T1 tumor cells have been recorded using 785 nm excitation laser. The state of the tissues was confirmed by standard pathological tests. The multivariate statistical analysis methods (principle component analysis and discriminant functional analysis) have been used to categorize the Raman spectra. The statistical algorithms based on the Raman spectral peak heights, clearly separated tissues into six distinct classes, including mastitis, which is clearly separated from normal and tumor. This study suggests that the Raman spectroscopy can possibly perform a real-time analysis of the human mammary tissues for the detection of cancer.

  6. Peculiarities in the Raman spectra of ZrB{sub 12} and LuB{sub 12} single crystals

    SciTech Connect

    Werheit, H. . E-mail: helmut.werheit@koeln.de; Paderno, Yu.; Filippov, V.; Paderno, V.; Pietraszko, A.; Armbruester, M.; Schwarz, U.

    2006-09-15

    We have measured Raman spectra of high-quality Zr{sup nat}B{sub 12}, Lu{sup nat}B{sub 12} and Lu{sup 11}B{sub 12} single crystals with high resolution, and the observed strong peaks are attributed to specific vibration modes. Besides, there are a number of additional Raman peaks in spectral ranges, where only Raman-inactive vibrations of the atomic arrangement are expected. Accordingly, it is assumed, that the investigated crystals contain intrinsic structural imperfections or distortions in sufficient concentration and efficiency to initiate the observed breaking of phonon selection rules. We suppose boron vacancies, boron isotope effects and displacements of the metal atoms to be reasons for such imperfections. - Graphical abstract: Raman spectra of Lu{sup nat}B{sub 12}, Lu{sup 11}B{sub 12} and Zr{sup nat}B{sub 12}.

  7. Raman spectra calculations for Si-Ge core-shell nanocrystals using ab initio real-space methods

    NASA Astrophysics Data System (ADS)

    Bobbitt, N. Scott; Chelikowsky, James R.

    We use a real-space pseudopotential method within density functional theory to calculate Raman spectra for Si-Ge core-shell nanocrystals. We examine the lattice strain induced by the interface of the core and the shell. We calculate how this strain affects the vibrational modes and Raman spectra. We also find that the relative size of the Si and Ge peaks in the Raman spectrum is proportional to the size of the Si core and Ge shell regions, which suggests that Raman spectroscopy can be used to experimentally determine the relative size of the core and the outer shell in these nanocrystals. This work is supported by the DOE under Grant Number DE-FG02-06ER46286. Computations were performed on machines at TACC and NERSC.

  8. The Raman and SERS spectra of indigo and indigo-Ag2 complex: DFT calculation and comparison with experiment.

    PubMed

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

    2018-01-05

    Using time-dependent density functional theory in conjunction with B3LYP functional and LANL2DZ/6-31+g(d,p) basis sets, static and pre-resonance Raman spectra of the indigo-Ag2 complex have been calculated. Structure optimization, excitation energies and pre-resonance Raman spectra of the indigo molecule have been obtained at the same level of theory. The available experimental Raman spectra at 1064, 785 and 514nm and the SERS spectra at 785 and 514nm have been well reproduced by the calculation. Experimental SERS spectra are confronted with the calculated pre-resonance Raman spectra obtained for the indigo-Ag2 complex. The Raman activities calculated under the infinite lifetime approximation show a strong dependence upon the proximity to the energy and the oscillator strength of the excitation electronic transition. The comparison of the integrated EFs for indigo and indigo-Ag2 calculated Raman spectra, gave some hints as to the enhancement mechanisms acting for the different excitation wavelengths. Whereas for excitation at a wavelength corresponding to 785nm, the enhancement mechanism for the Raman spectrum of the metal complex seems the chemical one, the strong increment (ten times) of the integrated EF of the Raman spectra of the complex in the case of 514nm excitation, suggests the onset of other enhancement mechanisms. Assuming that intra-cluster transitions with high oscillator strength can be thought of as to mimic surface plasmons excitations, we suggest the onset of the electromagnetic mechanisms (EM) as the origin of the Raman spectrum enhancement. Nevertheless, other enhancement effects cannot be ruled out, as a new molecular transition gains strength in the proximity of the excitation wavelength, as a consequence of the symmetry lowering of the molecule in the complex. A large variation across vibrational modes, by a factor of at least 10(4), was found for the EFs. This large variation in the EFs can indicate that B-term Herzberg-Teller scattering

  9. NIR Raman spectra of whole human blood: Effects of laser-induced and in vitro hemoglobin denaturation

    PubMed Central

    Lemler, P.; Premasiri, W. R.; DelMonaco, A.; Ziegler, L. D.

    2013-01-01

    Care must be exercised in the use of Raman spectroscopy for the identification of blood in forensic applications. The 785 nm excited Raman spectra of dried whole human blood are shown to be exclusively due to oxyhemoglobin (oxyHb) or related hemoglobin denaturation products. Raman spectra of whole blood are reported as a function of incident 785 nm laser power and features attributable to heme aggregates are observed for fluences on the order of 104 W/cm2 and 20 sec signal collection times. In particular, the formation of this local heating induced heme aggregate product is indicated by a red-shifting of several heme porphyrin ring vibrational bands, the appearance of a large broad band at 1248 cm−1, the disappearance of the Fe-O2 stretching and bending bands, and the observation of a large overlapping fluorescence. This denaturation product is also observed in the low power excited Raman spectrum of older ambient air exposed bloodstains (≥ two weeks). The 785 nm excited Raman spectrum of methemoglobin whole blood is reported and increasing amounts of this natural denaturation product can also be identified in dried whole blood Raman spectra particularly when the blood has been stored prior to drying. These results indicate that to use 785 nm excited Raman spectra as an identification methodology for forensic applications to maximum effectiveness, incident laser powers need to be kept low to eliminate variable amounts of heme aggregate spectral components contributing to the signal and the natural aging process of hemoglobin denaturation needs to be accounted for. This also suggests that there is a potential opportunity for 785 nm excited Raman to be a sensitive indicator of dried bloodstain age at crime scenes. PMID:24162820

  10. FT-Raman spectra of cellulose and lignocellulose materials : “self-absorption” phenomenon and its implications for quantitative work

    Treesearch

    Umesh Agarwal; Nancy Kawai

    2003-01-01

    The phenomenon of “self-absorption” was found to exist in the FT-Raman spectra of cellulose and thermomechanical pulp (TMP), but not in the spectrum of milled wood lignin. For cellulose and TMP, the effect was responsible for reducing the intensity of the Raman bands in the C-H stretch region. Several factors including sampling position, sample thickness, and moisture...

  11. Characterizing variability in in vivo Raman spectra of different anatomical locations in the upper gastrointestinal tract toward cancer detection

    NASA Astrophysics Data System (ADS)

    Bergholt, Mads Sylvest; Zheng, Wei; Lin, Kan; Ho, Khek Yu; Teh, Ming; Yeoh, Khay Guan; So, Jimmy Bok Yan; Huang, Zhiwei

    2011-03-01

    Raman spectroscopy is an optical vibrational technology capable of probing biomolecular changes of tissue associated with cancer transformation. This study aimed to characterize in vivo Raman spectroscopic properties of tissues belonging to different anatomical regions in the upper gastrointestinal (GI) tract and explore the implications for early detection of neoplastic lesions during clinical gastroscopy. A novel fiber-optic Raman endoscopy technique was utilized for real-time in vivo tissue Raman measurements of normal esophageal (distal, middle, and proximal), gastric (antrum, body, and cardia) as well as cancerous esophagous and gastric tissues from 107 patients who underwent endoscopic examinations. The non-negativity-constrained least squares minimization coupled with a reference database of Raman active biochemicals (i.e., actin, histones, collagen, DNA, and triolein) was employed for semiquantitative biomolecular modeling of tissue constituents in the upper GI. A total of 1189 in vivo Raman spectra were acquired from different locations in the upper GI. The Raman spectra among the distal, middle, and proximal sites of the esophagus showed no significant interanatomical variability. The interanatomical variability of Raman spectra among normal gastric tissue (antrum, body, and cardia) was subtle compared to cancerous tissue transformation, whereas biomolecular modeling revealed significant differences between the two organs, particularly in the gastroesophageal junction associated with proteins, DNA, and lipids. Cancerous tissues can be identified across interanatomical regions with accuracies of 89.3% [sensitivity of 92.6% (162/175) specificity of 88.6% (665/751)], and of 94.7% [sensitivity of 90.9% (30/33) specificity of 93.9% (216/230)] in the gastric and esophagus, respectively, using partial least squares-discriminant analysis together with the leave-one tissue site-out, cross validation. This work demonstrates that Raman endoscopy technique has

  12. Amide I vibrational mode suppression in surface (SERS) and tip (TERS) enhanced Raman spectra of protein specimens.

    PubMed

    Kurouski, Dmitry; Postiglione, Thomas; Deckert-Gaudig, Tanja; Deckert, Volker; Lednev, Igor K

    2013-03-21

    Surface- and tip-enhanced Raman spectroscopy (SERS and TERS) are modern spectroscopic techniques, which are becoming widely used and show a great potential for the structural characterisation of biological systems. Strong enhancement of the Raman signal through localised surface plasmon resonance enables chemical detection at the single-molecule scale. Enhanced Raman spectra collected from biological specimens, such as peptides, proteins or microorganisms, were often observed to lack the amide I band, which is commonly used as a marker for the interpretation of the secondary protein structure. The cause of this phenomenon was unclear for many decades. In this work, we investigated this phenomenon for native insulin and insulin fibrils using both TERS and SERS and compared these spectra to the spectra of well-defined homo peptides. The results indicate that the appearance of the amide I Raman band does not correlate with the protein aggregation state, but is instead determined by the size of the amino acid side chain. For short model peptides, the absence of the amide I band in TERS and SERS spectra correlates with the presence of a bulky side chain. Homo-glycine and -alanine, which are peptides with small side chain groups (H and CH(3), respectively), exhibited an intense amide I band in almost 100% of the acquired spectra. Peptides with bulky side chains, such as tyrosine and tryptophan, exhibited the amide I band in 70% and 31% of the acquired spectra, respectively.

  13. Raman spectra and vibrational analysis of BaFe{sub 12}O{sub 19} hexagonal ferrite

    SciTech Connect

    Kreisel, J.; Lucazeau, G.; Vincent, H.

    1998-04-01

    This paper reports on the first Raman spectra of barium hexaferrite, BaFe{sub 12}O{sub 19}, as a member of the magnetoplumbite-type structure. The spectra, recorded from 150 to 1,000 cm{sup {minus}1} at room and liquid nitrogen temperature, are analyzed on the basis of D{sub 6h} factor group selection rules. The iron atom on the bi-pyramidal site is discussed with regard to its particular dynamics. The distribution of normal modes in BaFe{sub 12}O{sub 19} is examined on the basis of the Raman spectra of {beta}-alumina and a series of ferrites. Emphasis has been put on the factors influencing the Raman frequencies, namely the value of the coordination number, the degree of connection of a coordinated group, and the mass effect.

  14. Predicting Raman Spectra of Aqueous Silica and Alumina Species in Solution From First Principles

    NASA Astrophysics Data System (ADS)

    Hunt, J. D.; Schauble, E. A.; Manning, C. E.

    2006-12-01

    Dissolved silica and alumina play an important role in lithospheric fluid chemistry. Silica concentrations in aqueous fluids vary over the range of crustal temperatures and pressures enough to allow for significant mass transport of silica via fluid-rock interaction. The polymerization of silica, and the possible incorporation of alumina into the polymer structure, could afford crystal-like or melt-like sites to otherwise insoluble elements such as titanium, leading to enhanced mobility. Raman spectroscopy in a hydrothermal diamond anvil cell (HDAC) has been used to study silica polymerization at elevated pressure and temperature [Ref. 1, 2], but Raman spectra of expected solutes are not fully understood. We calculated Raman spectra of H4SiO4 monomers, H6Si2O7 dimers, and H6SiAlO_7^- dimers, from first principles using hybrid density functional theory (B3LYP). These spectra take into account the variation in bridging angle (Si-O-Si and Si-O-Al angles) that the dimers will have at a given temperature by calculating a potential energy surface of the dimer as the bridging angle varies, and using a Boltzmann distribution at that temperature to determine relative populations at each geometry. Solution effects can be incorporated by using a polarizable continuum model (PCM), and a potential energy surface has been constructed for the silica dimer using a PCM. The bridging angle variation explains the broadness of the 630 cm^-^1 silica dimer peak observed in HDAC experiments [Ref. 1, 2] at high temperatures. The silica-alumina dimer bridging angle is shown to be stiffer than the silica dimer bridging angle, which results in a much narrower main peak. The synthetic spectrum obtained for the silica-alumina dimer suggests that there may be a higher ratio of complexed alumina to free alumina in solution at highly basic pH than previously estimated [Ref. 3]. References: 1. Zotov, N. and H. Keppler, Chemical Geology, 2002. 184: p. 71-82. 2. Zotov, N. and H. Keppler, American

  15. Sorting of Single Biomolecules based on Fourier Polar Representation of Surface Enhanced Raman Spectra

    PubMed Central

    Leray, Aymeric; Brulé, Thibault; Buret, Mickael; Colas des Francs, Gérard; Bouhelier, Alexandre; Dereux, Alain; Finot, Eric

    2016-01-01

    Surface enhanced Raman scattering (SERS) spectroscopy becomes increasingly used in biosensors for its capacity to detect and identify single molecules. In practice, a large number of SERS spectra are acquired and reliable ranking methods are thus essential for analysing all these data. Supervised classification strategies, which are the most effective methods, are usually applied but they require pre-determined models or classes. In this work, we propose to sort SERS spectra in unknown groups with an alternative strategy called Fourier polar representation. This non-fitting method based on simple Fourier sine and cosine transforms produces a fast and graphical representation for sorting SERS spectra with quantitative information. The reliability of this method was first investigated theoretically and numerically. Then, its performances were tested on two concrete biological examples: first with single amino-acid molecule (cysteine) and then with a mixture of three distinct odorous molecules. The benefits of this Fourier polar representation were highlighted and compared to the well-established statistical principal component analysis method. PMID:26833130

  16. Sorting of Single Biomolecules based on Fourier Polar Representation of Surface Enhanced Raman Spectra

    NASA Astrophysics Data System (ADS)

    Leray, Aymeric; Brulé, Thibault; Buret, Mickael; Colas Des Francs, Gérard; Bouhelier, Alexandre; Dereux, Alain; Finot, Eric

    2016-02-01

    Surface enhanced Raman scattering (SERS) spectroscopy becomes increasingly used in biosensors for its capacity to detect and identify single molecules. In practice, a large number of SERS spectra are acquired and reliable ranking methods are thus essential for analysing all these data. Supervised classification strategies, which are the most effective methods, are usually applied but they require pre-determined models or classes. In this work, we propose to sort SERS spectra in unknown groups with an alternative strategy called Fourier polar representation. This non-fitting method based on simple Fourier sine and cosine transforms produces a fast and graphical representation for sorting SERS spectra with quantitative information. The reliability of this method was first investigated theoretically and numerically. Then, its performances were tested on two concrete biological examples: first with single amino-acid molecule (cysteine) and then with a mixture of three distinct odorous molecules. The benefits of this Fourier polar representation were highlighted and compared to the well-established statistical principal component analysis method.

  17. FTIR and Raman spectra, electronic spectra and normal coordinate analysis of N,N-dimethyl-3-phenyl-3-pyridin-2-yl-propan-1-amine by DFT method

    NASA Astrophysics Data System (ADS)

    Renuga, S.; Karthikesan, M.; Muthu, S.

    2014-06-01

    The Fourier transform infrared (FT-IR) and FT-Raman spectra of N,N-dimethyl-3-phenyl-3-pyridin-2-yl-propan-1-amine have been recorded in the range 4000-500 cm-1 and 4000-50 cm-1 respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FT-IR and FT Raman data. The vibrational frequencies experimentally determined, was compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31+G(d, p) basis set for the optimized geometry of the compound. The geometry and normal modes of vibration obtained from the DFT method are in good agreement with the experimental data. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The calculated infrared and Raman spectra of the title compounds were also stimulated utilizing the scaled force fields and the computed dipole derivatives for IR intensities and polarizability derivatives for Raman intensities. The change in electron density (ED) in the σ* and π* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interaction. The electronic spectrum determined by TD-DFT method is compared with the observed electronic spectrum.

  18. FTIR and Raman spectra, electronic spectra and normal coordinate analysis of N,N-dimethyl-3-phenyl-3-pyridin-2-yl-propan-1-amine by DFT method.

    PubMed

    Renuga, S; Karthikesan, M; Muthu, S

    2014-06-05

    The Fourier transform infrared (FT-IR) and FT-Raman spectra of N,N-dimethyl-3-phenyl-3-pyridin-2-yl-propan-1-amine have been recorded in the range 4000-500cm(-1) and 4000-50cm(-1) respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FT-IR and FT Raman data. The vibrational frequencies experimentally determined, was compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31+G(d,p) basis set for the optimized geometry of the compound. The geometry and normal modes of vibration obtained from the DFT method are in good agreement with the experimental data. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The calculated infrared and Raman spectra of the title compounds were also stimulated utilizing the scaled force fields and the computed dipole derivatives for IR intensities and polarizability derivatives for Raman intensities. The change in electron density (ED) in the σ(*) and π(*) antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interaction. The electronic spectrum determined by TD-DFT method is compared with the observed electronic spectrum.

  19. [Raman spectra study of soy protein isolate structure treated with pulsed electric fields].

    PubMed

    Liu, Yan-Yan; Zeng, Xin-An; Han, Zhong

    2010-12-01

    The effect of pulsed electric field on molecular structure of soy protein isolate (SPI) was investigated by Raman spectroscopy method. The applied pulsed electric field was up to 50 kV * cm(-1) with pulse width 40 micros. It was demonstrated from the Raman spectra that the PEF treatment undei 50 kV * cm(-1) had induced disappearance significantly of peak near 2 886 cm(-1) bond. It was also explored that with the increase in treatment time, the polarity of microenvironment of aliphatic amino acid residues and the exposure of tryptophan residues from a buried hydrophobic microenvironment were increased. On the other hand, the interaction of serine acid residues, the C-H plane bend vibration, C-N stretch vibration, and the C=O stretch vibration of aspartic acid and glutamic acid were decreased. The embeding or participation of the tyrosine phenolic groups as hydrogen bond donors was firstly increased with the treatment time (less than 1 600 micros), and afterwards decreased (from 1 600 to 3 200 micros).

  20. Disentangling contributions of point and line defects in the Raman spectra of graphene-related materials

    NASA Astrophysics Data System (ADS)

    Cançado, Luiz Gustavo; Gomes da Silva, Mateus; Martins Ferreira, Erlon H.; Hof, Ferdinand; Kampioti, Katerina; Huang, Kai; Pénicaud, Alain; Achete, Carlos Alberto; Capaz, Rodrigo B.; Jorio, Ado

    2017-06-01

    The transition from graphene to a fully disordered sp2 carbon material can be idealized by either cutting graphene into smaller and smaller pieces, or adding more and more point defects. In other words, from the dimensionality standpoint, defects in two-dimensional (2D) systems can be either one- (1D) or zero-dimensional (0D). From an application point of view, both in terms of bottom-up as well as top-down approaches, the discrimination between these two structural disorder in two-dimensional systems is urgently desired. In graphene, both types of defects produce changes in the Raman spectrum, but identifying separately the contribution from each defect-type has not yet been achieved. Here we show that a diagram can be built for disentangling contributions of point-like and line-like defects to the Raman spectra of graphene-related materials embracing, from the topology point of view, all possible structures from perfect to fully disordered sp2 bonded carbons. Two sets of graphene-related samples, produced by well-established protocols that generate either 0D or 1D defects in a controlled way, are analysed with our model and used to parameterize the limiting values of the phase space. We then discuss the limitations and apply our new methodology to analyse the structure of two-dimensional nanocarbons generated from renewable gas, used to produce inks and conducting coatings.

  1. Wavelet data processing of micro-Raman spectra of biological samples

    NASA Astrophysics Data System (ADS)

    Camerlingo, C.; Zenone, F.; Gaeta, G. M.; Riccio, R.; Lepore, M.

    2006-02-01

    A wavelet multi-component decomposition algorithm is proposed for processing data from micro-Raman spectroscopy (μ-RS) of biological tissue. The μ-RS has been recently recognized as a promising tool for the biopsy test and in vivo diagnosis of degenerative human tissue pathologies, due to the high chemical and structural information contents of this spectroscopic technique. However, measurements of biological tissues are usually hampered by typically low-level signals and by the presence of noise and background components caused by light diffusion or fluorescence processes. In order to overcome these problems, a numerical method based on discrete wavelet transform is used for the analysis of data from μ-RS measurements performed in vitro on animal (pig and chicken) tissue samples and, in a preliminary form, on human skin and oral tissue biopsy from normal subjects. Visible light μ-RS was performed using a He-Ne laser and a monochromator with a liquid nitrogen cooled charge coupled device equipped with a grating of 1800 grooves mm-1. The validity of the proposed data procedure has been tested on the well-characterized Raman spectra of reference acetylsalicylic acid samples.

  2. Raman spectra and ab initio calculation of a structure of aqueous solutions of methanol

    NASA Astrophysics Data System (ADS)

    Hushvaktov, H. A.; Tukhvatullin, F. H.; Jumabaev, A.; Tashkenbaev, U. N.; Absanov, A. A.; Hudoyberdiev, B. G.; Kuyliev, B.

    2017-03-01

    Small amount of low molecular weight alcohols leads to appearance of some special properties of alcohol-water solutions. In the literature it is associated with structural changes in solution with changing concentration. However, the problem special properties and structure of solutions at low concentration of alcohol is not very clear. Accordingly, we carried out quantum-chemical calculations and experimental studies of aqueous solutions of methyl alcohol. The calculations performed for ten molecular alcohol-water mixtures showed that with a low concentration of methyl alcohol in water the solubility of alcohol is poor: the alcohol molecules are displaced from the water structure and should form a particular structure. Thus, with low concentration of alcohol in the aqueous solution there are two types of structures: the structure of water and the structure of alcohol that should lead to the presence of specific properties. At high concentration of alcohol the structure of water is destroyed and there is just the structure made of alcohol-water aggregates. This interpretation is consistent with the experimental data of Raman spectroscopy. The band of Csbnd O vibrations of alcohol is detected to be of complex character just in the region of the presence of specific properties. Formation of intermolecular H-bonds also complicates the Raman spectra of Osbnd H or O-D vibrations of pure alcohol: a non-coincidence of peak frequencies, a shift of the band towards low-frequency region, a strong broadening of the band.

  3. DFT study of IR and Raman spectra of phosphotrihydrazone dendrimer with terminal phenolic groups

    NASA Astrophysics Data System (ADS)

    Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

    2017-09-01

    FT Raman and infrared spectra of phosphotrihydrazone (S)P[N(CH3)Ndbnd CHsbnd C6H4sbnd OH]3 (G0) were recorded. This compound is a zero generation phosphorus dendrimer with terminal phenolic groups. Optimal geometry and vibrational frequencies were calculated for G0 using the density functional theory (DFT). The molecule studied has C3 symmetry. In the molecule G0, each sbnd C6H4sbnd CHdbnd Nsbnd N(CH3)sbnd P arm is flat. Optimized geometric parameters correspond to experimental data. The core of the dendrimer manifests itself as a band at 647 cm-1 in the Raman spectrum of G0 related to Pdbnd S stretching. Phenolic end functions exhibit a well-defined band at 3374 cm-1 in the experimental IR spectrum of G0. The observed frequency of the OH stretching vibrations of the phenolic groups is lower than the theoretical value due to the intermolecular Osbnd H⋯O hydrogen bond. This hydrogen bond is also responsible for the higher intensity of this band in the experimental IR spectrum compared with the theoretical value. DFT calculations suggest full assignment of normal modes. Global and local descriptors characterize the reactivity of the core and end groups.

  4. Raman Spectra of Luminescent Graphene Oxide (GO)-Phosphor Hybrid Nanoscrolls.

    PubMed

    Rani, Janardhanan R; Oh, Se-I; Jang, Jae-Hyung

    2015-12-04

    Graphene oxide (GO)-phosphor hybrid nanoscrolls were synthesized using a simple chemical method. The GO-phosphor ratio was varied to find the optimum ratio for enhanced optical characteristics of the hybrid. A scanning electron microscope analysis revealed that synthesized GO scrolls achieved a length of over 20 μm with interior cavities. The GO-phosphor hybrid is extensively analyzed using Raman spectroscopy, suggesting that various Raman combination modes are activated with the appearance of a low-frequency radial breathing-like mode (RBLM) of the type observed in carbon nanotubes. All of the synthesized GO-phosphor hybrids exhibit an intense luminescent emission around 540 nm along with a broad emission at approximately 400 nm, with the intensity ratio varying with the GO-phosphor ratio. The photoluminescence emissions were gauged using Commission Internationale d'Eclairage (CIE) coordinates and at an optimum ratio. The coordinates shift to the white region of the color spectra. Our study suggests that the GO-phosphor hybrid nanoscrolls are suitable candidates for light-emitting applications.

  5. Theoretical study the surface-enhanced Raman scattering spectra of Thiophenol absorbed on Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Han, Yu; Liu, Chengyou; Jiang, Chengguo

    2016-10-01

    Surface-Enhanced Raman Scattering (SERS) is a powerful spectroscopic technique for highly sensitive molecular detection. It effectively improves the defect of low sensitivity of normal Raman spectra. So it is widely used in the area of surface science, analytical science, biological science and so on. Using Density Functional Theory (DFT) and Time- Dependent density functional theory (TD-DFT), the SERS spectrum has been simulated for biphenyl l-4, 4'-dithiol (BPDT, HS-(C6H4)2-SH), p-terphenyl-4, 4″-dithiol (TPDT, HS - (C6H4)3-SH )1, 4-benzenedithiol (BDT) absorbed on AuNPs and AgNPs. The SERS which aroused by C-C stretching mode is increasing with the benzene ring. Whereas, for the SERS of S-H bending vibrational mode, changing the position of S atom have little effect. The C-S stretching mode and S-H stretching mode are also little effect by the insert number.

  6. Identification of heme propionate vibrational modes in the resonance Raman spectra of cytochrome c oxidase.

    PubMed

    Egawa, Tsuyoshi; Lee, Hyun Ju; Ji, Hong; Gennis, Robert B; Yeh, Syun-Ru; Rousseau, Denis L

    2009-11-01

    The propionate groups of heme a and a(3) in cytochrome c oxidase (CcO) have been postulated to mediate both the electron and proton transfer within the enzyme. To establish structural markers for the propionate groups, their associated vibrational modes were identified in the resonance Raman spectra of CcO from bovine (bCcO) and Rhodobacter sphaeroides (RsCcO). The distinction between the modes from the propionates of heme a and heme a(3), as well as those from the propionates on the pyrrole rings A and D in each heme, was made on the basis of H2O-D2O isotope substitution experiments combined with wavelength-selective resonance enhancement (for bCcO) or mutagenesis studies (for RsCcO).

  7. Predicted infrared and Raman spectra for neutral Ti{sub 8}C{sub 12} isomers

    SciTech Connect

    Baruah, Tunna; Pederson, Mark R.; Lyn, M.L.; Castleman, A.W. Jr.

    2002-11-01

    Using a density-functional based algorithm, the full infrared and Raman spectra are calculated for the neutral Ti{sub 8}C{sub 12} cluster assuming geometries of T{sub h}, T{sub d}, D{sub 2d}, and C{sub 3v} symmetry. The T{sub h} pentagonal dodecahedron is found to be dynamically unstable. The calculated properties of the relaxed structure having C{sub 3v} symmetry are found to be in excellent agreement with experimental gas-phase infrared results, ionization potential and electron affinity measurements. Consequently, the results presented may be used as a reference for further experimental characterization using vibrational spectroscopy.

  8. Raman scattering and fluorescence spectra of water from the sea surface microlayer

    NASA Astrophysics Data System (ADS)

    Fadeev, V. V.; Burikov, S. A.; Volkov, P. A.; Lapshin, V. B.; Syroeshkin, A. V.

    2009-04-01

    The Raman scattering and fluorescence spectra were first obtained for the water of sea surface microlayers (SML) of 1 and 0.2 mm thickness (sampled with a Garrett net and a Lapshin capillary sampler, respectively). For reference, samples of water below the SML (from the layer of 0.5 m) were also taken. Substantial differences were found for the values of the normalized intensity of the fluorescence (the number of photons from the volume unit in response to a unit of excitation) between the aqueous humic substances and, presumably, oil hydrocarbons and proteins. Some slight but analyzable differences in the shapes and location of spectral bands were also found. These latter allow one to determine the content of salts and the characteristics of complicated organic compounds in the SML and to compare them to those within the water volume.

  9. Raman spectra of bilayer graphene covered with Poly(methyl methacrylate) thin film

    SciTech Connect

    Xia Minggang; Su Zhidan; Zhang Shengli

    2012-09-15

    The Raman spectra of bilayer graphene covered with poly(methyl methacrylate) (PMMA) were investigated. Both the G and 2D peaks of PMMA-coated graphene were stiff and broad compared with those of uncovered graphene. This could be attributed to the residual strain induced by high-temperature baking during fabrication of the nanodevice. Furthermore, the two 2D peaks stiffened and broadened with increasing laser power, which is just the reverse to uncovered graphene. The stiffness is likely caused by graphene compression induced by the circular bubble of the thin PMMA film generated by laser irradiation. Our findings may contribute to the application of PMMA in the strain engineering of graphene nanodevices.

  10. Raman spectra of hydrogen molybdenum bronze, H 0.30MoO 3

    NASA Astrophysics Data System (ADS)

    Eda, Kazuo

    1992-06-01

    The Raman spectra of hydrogen molybdenum bronze, H 0.30MoO 3, named as Type I, were studied. Four bands observed at 1011, ca. 750, ca. 670, and 452 cm -1 were assigned to the Mo-O1, Mo-O3', Mo-O2', and Mo-O2 stretching vibrations, respectively. These assignments suggest that the structural change from MoO 3 to Type I induces a shift of the Mo-O1 stretching vibrations to a higher frequency and shifts of the Mo-O3' and Mo-O2 stretching vibrations to lower frequencies. The frequencies of the Mo-O2' stretching vibrations were scarcely influenced. These spectral changes were understood on the basis of the changes in the bond length of Type I presented by Dickens et al.

  11. Solvent effects on the resonance Raman spectra of bacteriochlorophyll a cation radical

    NASA Astrophysics Data System (ADS)

    Misono, Yasuhito; Nishizawa, Ei-ichi; Limantara, Leenawaty; Koyama, Yasushi; Itoh, Koichi

    1995-04-01

    Resonance Raman (RR) spectra were measured for the cation radical of bacteriochlorophyll a in acetone, methanol, dichloromethane and mixed solvents of acetone and methanol. The ring-breathing (C a-C m stretching) frequency of the radical (abbreviated as vr+) was observed at 1601 cm -1 in acetone (forming a penta-coordinated monomer), at 1587 cm -1 in a methanol (forming a hexa-coordinated monomer) and at 1600 cm -1 in dichloromethane (forming a penta-coordinated aggregate). The RR spectrum of the radical in dichloromethane is almost identical to the transient RR spectrum ascribed to 'the aggregated T 1 species of Bchl a' formed in the particular solvent by Nishizawa, Limantara, Nanjou, Nagae, Kakuno and Koyama, indicating that their interpretation needs to be revised.

  12. [Surface-enhanced Raman spectra of oxidation damnification of fetal bovine serum by ozone].

    PubMed

    Zou, Zu-Quan; Liu, Yan-Nan; Wu, Ying; Li, Qi-Nan; Chen, Mei-Zong; Sun, Hai-Ying; Lee, Imshik

    2007-06-01

    Fetal bovine serum was treated by ozone for 1 hour and 3 hours before getting its surface-enhanced Raman spectra from 200 to 1 800 cm(-1). Treated with ozone for 1 hour, it shows a significant decrease in band intensity. Treated with ozone for 3 hours, the band intensity has a further decrease but not so obviously, which means that oxidation of ozone is short lived. Treated with ozone, the orderly conformations of main chains in protein such as alpha-helix, beta-sheet and beta-corner are damaged seriously. Aromatic side chains and C-S of Cys and Met also are damnified greatly. All this means that strong oxidation of ozone results in denaturation, conformational changes and even degradation in protein.

  13. Fully anharmonic IR and Raman spectra of medium-size molecular systems: accuracy and interpretation†

    PubMed Central

    Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien

    2015-01-01

    Computation of full infrared (IR) and Raman spectra (including absolute intensities and transition energies) for medium- and large-sized molecular systems beyond the harmonic approximation is one of the most interesting challenges of contemporary computational chemistry. Contrary to common beliefs, low-order perturbation theory is able to deliver results of high accuracy (actually often better than those issuing from current direct dynamics approaches) provided that anharmonic resonances are properly managed. This perspective sketches the recent developments in our research group toward the development a robust and user-friendly virtual spectrometer rooted into the second-order vibrational perturbation theory (VPT2) and usable also by non-specialists essentially as a black-box procedure. Several examples are explicitly worked out in order to illustrate the features of our computational tool together with the most important ongoing developments. PMID:24346191

  14. Raman spectra of aligned carbon micro-coils and their impedance characteristics under loads

    SciTech Connect

    Tao, Wang; Yabo, Zhu Heliang, Fan; Zhicheng, Ju; Lei, Chen; Zhengyuan, Wang

    2014-02-21

    Scanning and transmission electron microscopy were used to characterize the morphology of the carbon microcoils (CMCs). The Raman spectra showed that CMCs had local regular structure as I{sub D}/I{sub G} = 0.841. Then, aligned CMCs/silicone–rubber composites (5 × 5 × 1 mm{sup 3}) were fabricated by coating of silicone rubber on the CMCs. Their alternating current impedance characteristics were measured as a function of applied load and the pressure sensitivity was discussed. The results showed that the impedance decreased as the increasing applied load, and the sample with less CMCs owned high pressure sensitivity, which indicated a novel composite film could act as an alternative of tactile sensor.

  15. Surface-enhanced raman spectra of pyrazine, pyrimidine, and pyridazine adsorbed on silver sols

    SciTech Connect

    Muniz-Miranda, M.; Neto, N.; Sbrana, G.

    1988-02-25

    Raman spectra of pyrazine, pyrimidine, and pyridazine adsorbed on silver sols have been obtained and compared with existing data from corresponding experiments on Ag electrode. These two techniques give similar results except for pyrazine for with strong bands, observed only in the SER spectrum on the electrode, may be due to reduction products coadsorbed on the Ag surface. Chemisorption plays a role in the absorption of diazines as evidence of Ag-N bond formation was found in the SERS of all three molecules. Both N atoms of pyridazine are bound to the substrate and this explains an enhancement, for the latter molecule, of 2 orders of magnitude larger than for the other two compounds. The presence of low-frequency Ag-N modes and predictions of surface selection rules support edge on, rather than flat, orientation of diazines on the colloidal particles.

  16. Theoretical Study of Infrared and Raman Spectra of Hydrated Magnesium Sulfate Salts

    NASA Technical Reports Server (NTRS)

    Chaban, Galina M.; Huo, Winifred M.; Lee, Timothy J.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    Harmonic and anharmonic vibrational frequencies, as well as infrared and Raman intensities, are calculated for MgSO4.nH20 (n=1-3). Electronic structure theory at the second order Moller-Plesset perturbation theory (MP2) level with a triple-zeta + polarization (TZP) basis set is used to determine the geometry, properties, and vibrational spectra of pure and hydrated MgSO4 salts. The direct vibrational self-consistent field (VSCF) method and its correlation corrected (CC-VSCF) extension are used to determine anharmonic corrections to vibrational frequencies and intensities for the pure MgSO4 and its complex with one water molecule. Very significant differences are found between vibrational of water molecules in complexes with MgSO4 and pure water. Some of the O-H stretching frequencies are shifted to the red very significantly (by up to 1500-2000/cm) upon complexation with magnesium sulfate. They should be observed between 1700 and 3000/cm in a region very different from the corresponding O-H stretch frequency region of pure water (3700-3800/cm). In addition, the SO2 stretching vibrations are found at lower frequency regions than the water vibrations. They can serve as unique identifiers for the presence of sulfate salts. The predicted infrared and Raman spectra should be of valuable help in the design of future missions and analysis of observed data from the ice surface of Jupiter's moon Europa that possibly contains hydrated MgSO4 salts.

  17. Time-dependent wave packet averaged vibrational frequencies from femtosecond stimulated Raman spectra

    NASA Astrophysics Data System (ADS)

    Wu, Yue-Chao; Zhao, Bin; Lee, Soo-Y.

    2016-02-01

    Femtosecond stimulated Raman spectroscopy (FSRS) on the Stokes side arises from a third order polarization, P(3)(t), which is given by an overlap of a first order wave packet, |" separators=" Ψ2 ( 1 ) ( p u , t ) > , prepared by a narrow band (ps) Raman pump pulse, Epu(t), on the upper electronic e2 potential energy surface (PES), with a second order wave packet, <" separators=" Ψ1 ( 2 ) ( p r ∗ , p u , t ) | , that is prepared on the lower electronic e1 PES by a broadband (fs) probe pulse, Epr(t), acting on the first-order wave packet. In off-resonant FSRS, |" separators=" Ψ2 ( 1 ) ( p u , t ) > resembles the zeroth order wave packet |" separators=" Ψ1 ( 0 ) ( t ) > on the lower PES spatially, but with a force on |" separators=" Ψ2 ( 1 ) ( p u , t ) > along the coordinates of the reporter modes due to displacements in the equilibrium position, so that <" separators=" Ψ1 ( 2 ) ( p r ∗ , p u , t ) | will oscillate along those coordinates thus giving rise to similar oscillations in P(3)(t) with the frequencies of the reporter modes. So, by recovering P(3)(t) from the FSRS spectrum, we are able to deduce information on the time-dependent quantum-mechanical wave packet averaged frequencies, ω ¯ j ( t ) , of the reporter modes j along the trajectory of |" separators=" Ψ1 ( 0 ) ( t ) > . The observable FSRS Raman gain is related to the imaginary part of P(3)(ω). The imaginary and real parts of P(3)(ω) are related by the Kramers-Kronig relation. Hence, from the FSRS Raman gain, we can obtain the complex P(3)(ω), whose Fourier transform then gives us the complex P(3)(t) to analyze for ω ¯ j ( t ) . We apply the theory, first, to a two-dimensional model system with one conformational mode of low frequency and one reporter vibrational mode of higher frequency with good results, and then we apply it to the time-resolved FSRS spectra of the cis-trans isomerization of retinal in rhodopsin [P. Kukura et al., Science 310, 1006 (2005)]. We obtain the vibrational

  18. Time-dependent wave packet averaged vibrational frequencies from femtosecond stimulated Raman spectra.

    PubMed

    Wu, Yue-Chao; Zhao, Bin; Lee, Soo-Y

    2016-02-07

    Femtosecond stimulated Raman spectroscopy (FSRS) on the Stokes side arises from a third order polarization, P(3)(t), which is given by an overlap of a first order wave packet, |Ψ2(1)(pu,t)>, prepared by a narrow band (ps) Raman pump pulse, Epu(t), on the upper electronic e2 potential energy surface (PES), with a second order wave packet, <Ψ1(2)(pr(∗),pu,t)|, that is prepared on the lower electronic e1 PES by a broadband (fs) probe pulse, Epr(t), acting on the first-order wave packet. In off-resonant |FSRS, Ψ2(1)(pu,t)> resembles the zeroth order wave packet |Ψ1(0)(t)> on the lower PES spatially, but with a force on |Ψ2(1)(pu,t)> along the coordinates of the reporter modes due to displacements in the equilibrium position, so that <Ψ1(2)(pr(∗),pu,t)| will oscillate along those coordinates thus giving rise to similar oscillations in P(3)(t) with the frequencies of the reporter modes. So, by recovering P(3)(t) from the FSRS spectrum, we are able to deduce information on the time-dependent quantum-mechanical wave packet averaged frequencies, ω̄j(t), of the reporter modes j along the trajectory of |Ψ1 (0)(t)>. The observable FSRS Raman gain is related to the imaginary part of P(3)(ω). The imaginary and real parts of P(3)(ω) are related by the Kramers-Kronig relation. Hence, from the FSRS Raman gain, we can obtain the complex P(3)(ω), whose Fourier transform then gives us the complex P(3)(t) to analyze for ω̄j(t). We apply the theory, first, to a two-dimensional model system with one conformational mode of low frequency and one reporter vibrational mode of higher frequency with good results, and then we apply it to the time-resolved FSRS spectra of the cis-trans isomerization of retinal in rhodopsin [P. Kukura et al., Science 310, 1006 (2005)]. We obtain the vibrational frequency up-shift time constants for the C12-H wagging mode at 216 fs and for the C10-H wagging mode at 161 fs which are larger than for the C11-H wagging mode at 127 fs, i.e., the C11-H

  19. [Study on the Temperature Dependent Phase Transformation of Raman Spectra for Cyclobutanol].

    PubMed

    Zhang, Huan-jun; Cheng, Xue-rui; Ren, Yu-fen; Zhu, Xiang; Yuan, Chao-sheng

    2016-02-01

    Cyclobutanol (C₄H₈O) is one of the four-membered ring type molecules, which usually adopts a non-planar equilibrium conformation, and the substituent group OH can adopt two positions relative to the puckered ring, the axial or the equatorial, giving rise to an additional degree of freedom and various molecular conformations. Additionally, temperature is one important thermodynamic parameter that greatly influents the structure and induces the possibility of conformational change or crystal change. As a consequence, there may be a number of phase transitions and molecular conformations for cyclobutanol under different temperature. In this paper, Raman and infrared spectroscopic technique were applied to investigate the vibration modes of cyclobutanol. The results indicate that the main component of the liquid cyclobutanol is equatorial-trans (Eq-t) conformer with a few Eq-g conformers at ambient condition. Then differential scanning calorimetry (DSC) and low temperature Raman spectroscopic were applied to study the phase transition of cyclobutanol during the cooling and heating process. It is observed that the Raman spectra and the intensities of these bands are not significantly changed during the cooling process. The results indicate that there is sill no presence of solidification especially cooling to 140K, which indicates that the cyclobutanol still remains the liquid state and supercooled state is observed during the cooling process. And this supercooled liquid is one metastable state, not in thermodynamic equilibrium. Further cooling to 138 K, the super-cooling liquid cyclobutanol will transform into the glassy state, accompanied with a small change of entropy. During the heating process, as the temperature is raised to 180 K, the Raman peaks became sharper and some new characteristic peaks appeared abruptly and a discontinuous change was observed in bandwidths versus temperature. And these new signatures can be maintained upon to 220 K, and then will

  20. An Investigation on Micro-Raman Spectra and Wavelet Data Analysis for Pemphigus Vulgaris Follow-up Monitoring.

    PubMed

    Camerlingo, Carlo; Zenone, Flora; Perna, Giuseppe; Capozzi, Vito; Cirillo, Nicola; Gaeta, Giovanni Maria; Lepore, Maria

    2008-06-01

    A wavelet multi-component decomposition algorithm has been used for data analysis of micro-Raman spectra of blood serum samples from patients affected by pemphigus vulgaris at different stages. Pemphigus is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. Spectra were measured by means of a Raman confocal microspectrometer apparatus using the 632.8 nm line of a He-Ne laser source. A discrete wavelet transform decomposition method has been applied to the recorded Raman spectra in order to overcome problems related to low-level signals and the presence of noise and background components due to light scattering and fluorescence. This numerical data treatment can automatically extract quantitative information from the Raman spectra and makes more reliable the data comparison. Even if an exhaustive investigation has not been done in this work, the feasibility of the follow-up monitoring of pemphigus vulgaris pathology has been clearly proved with useful implications for the clinical applications.

  1. An Investigation on Micro-Raman Spectra and Wavelet Data Analysis for Pemphigus Vulgaris Follow-up Monitoring

    PubMed Central

    Camerlingo, Carlo; Zenone, Flora; Perna, Giuseppe; Capozzi, Vito; Cirillo, Nicola; Gaeta, Giovanni Maria; Lepore, Maria

    2008-01-01

    A wavelet multi-component decomposition algorithm has been used for data analysis of micro-Raman spectra of blood serum samples from patients affected by pemphigus vulgaris at different stages. Pemphigus is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. Spectra were measured by means of a Raman confocal microspectrometer apparatus using the 632.8 nm line of a He-Ne laser source. A discrete wavelet transform decomposition method has been applied to the recorded Raman spectra in order to overcome problems related to low-level signals and the presence of noise and background components due to light scattering and fluorescence. This numerical data treatment can automatically extract quantitative information from the Raman spectra and makes more reliable the data comparison. Even if an exhaustive investigation has not been done in this work, the feasibility of the follow-up monitoring of pemphigus vulgaris pathology has been clearly proved with useful implications for the clinical applications. PMID:27879899

  2. Spectral signatures for the classification of microbial species using Raman spectra.

    PubMed

    Webb-Robertson, Bobbie-Jo M; Bailey, Vanessa L; Fansler, Sarah J; Wilkins, Michael J; Hess, Nancy J

    2012-08-01

    In general, classification-based methods based on confocal Raman microscopy are focused on targeted studies under which the spectral libraries are collected under controlled instrument parameters, which facilitate analyses via standard multivariate data analysis methods and cross-validation. We develop and compare approaches to transform spectra collected at different spectral ranges and varying levels of resolution into a single lower-dimension spectral signature library. This will result in a more robust analysis method able to accommodate spectra accumulated at different times and conditions. We demonstrate these approaches on a relevant test case; the identification of microbial species from a natural environment. The training data were based on samples prepared for three unique species collected at two time points and the test data consisted of blinded unknowns prepared and analyzed at a later date with different instrument parameters. The results indicate that using reduced dimension representations of the spectral signatures improves classification accuracy over basic alignment protocols. In particular, utilizing the microbial species partial least squares discriminant analysis classifier on the blinded samples based on alignment achieved ~78 % accuracy, while both binning and peak selection approaches yielded 100 % accuracy.

  3. Raman spectra of long chain hydrocarbons: anharmonic calculations, experiment and implications for imaging of biomembranes

    PubMed Central

    Šebek, Jiří; Pele, Liat; Potma, Eric O.

    2012-01-01

    First-principles anharmonic vibrational calculations are carried out for the Raman spectrum of the C–H stretching bands in dodecane, and for the C–D bands in the deuterated molecule. The calculations use the Vibrational Self-Consistent Field (VSCF) algorithm. The results are compared with liquid-state experiments, after smoothing the isolated-molecule sharp-line computed spectra. Very good agreement between the computed and experimental results is found for the two systems. The combined theoretical and experimental results provide insights into the spectrum, elucidating the roles of symmetric and asymmetric CH3 and CH2 hydrogenic stretches. This is expected to be very useful for the interpretation of spectra of long-chain hydrocarbons. The results show that anharmonic effects on the spectrum are large. On the other hand, vibrational degeneracy effects seem to be rather modest at the resolution of the experiments. The degeneracy effects may have more pronounced manifestations in higher-resolution experiments. The results show that first-principles anharmonic vibrational calculations for hydrocarbons are feasible, in good agreement with experiment, opening the way for applications to many similar systems. The results may be useful for the analysis of CARS imaging of lipids, for which dodecane is a representative molecule. It is suggested that first-principles vibrational calculations may be useful also for CARS imaging of other systems. PMID:21670823

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

    PubMed

    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.

  5. Assessing Polarizability Models for the Simulation of Low-Frequency Raman Spectra of Benzene.

    PubMed

    Bender, John S; Coasne, Benoit; Fourkas, John T

    2015-07-23

    Optical Kerr effect (OKE) spectroscopy is a widely used technique for probing the low-frequency, Raman-active dynamics of liquids. Although molecular simulations are an attractive tool for assigning liquid degrees of freedom to OKE spectra, the accurate modeling of the OKE and the motions that contribute to it relies on the use of a realistic and computationally tractable molecular polarizability model. Here we explore how the OKE spectrum of liquid benzene, and the underlying dynamics that determines its shape, are affected by the polarizability model employed. We test a molecular polarizability model that uses a point anisotropic molecular polarizability and three other models that distribute the polarizability over the molecule. The simplest and most computationally efficient distributed polarizability model tested is found to be sufficient for the accurate simulation of the many-body polarizability dynamics of this liquid. We further find that the atomic-to-molecular polarizability transformation approximation [Hu et al. J. Phys. Chem. B 2008, 112, 7837-7849], used in conjunction with this distributed polarizability model, yields OKE spectra whose shapes differ negligibly from those calculated without this approximation, providing a substantial increase in computational efficiency.

  6. Spectra of spontaneous Raman scattering in taper-drawn micro/nano-fibers

    NASA Astrophysics Data System (ADS)

    Xu, Yingxin; Cui, Liang; Li, Xiaoying; Guo, Cheng; Li, Yuhang; Xu, Zhongyang; Wang, Lijun; Fang, Wei

    2016-12-01

    We study the spontaneous Raman scattering (RS) in taper-drawn micro/nano-fibers (MNFs) by employing the photon counting technique. The spectra of RS in five MNFs, which are fabricated by using different heating flames (hydrogen flame or butane flame) and with different diameters, are measured within a frequency shift range of 1435 cm-1-3200 cm-1. From the measured spectra, we observe the RS peaks originated from silica and a unique RS peak with a frequency shift of ˜2905 cm-1 (˜87.2 THz). Unlike the former ones, the latter one is not observable in conventional optical fibers. Furthermore, the unique peak becomes obvious and starts to rapidly increase with the decrease of the diameter of MNFs when the diameter is smaller than 2 μm, and the intensity of the unique peak significantly depends on the heating flame used in the fabricating process. Our investigation is useful for the entanglement generation or optical sensing using taper-drawn MNFs. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304222 and 11527808) and the State Key Development Program for Basic Research of China (Grant No. 2014CB340103).

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

    NASA Astrophysics Data System (ADS)

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

    PubMed

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Probing the photoreaction mechanism of phytochrome through analysis of resonance Raman vibrational spectra of recombinant analogues.

    PubMed

    Andel, F; Murphy, J T; Haas, J A; McDowell, M T; van der Hoef, I; Lugtenburg, J; Lagarias, J C; Mathies, R A

    2000-03-14

    Resonance Raman spectra of native and recombinant analogues of oat phytochrome have been obtained and analyzed in conjunction with normal mode calculations. On the basis of frequency shifts observed upon methine bridge deuteration and vinyl and C(15)-methine bridge saturation of the chromophore, intense Raman lines at 805 and 814 cm(-)(1) in P(r) and P(fr), respectively, are assigned as C(15)-hydrogen out-of-plane (HOOP) wags, lines at 665 cm(-)(1) in P(r) and at 672 and 654 cm(-)(1) in P(fr) are assigned as coupled C=C and C-C torsions and in-plane ring twisting modes, and modes at approximately 1300 cm(-)(1) in P(r) are coupled N-H and C-H rocking modes. The empirical assignments and normal mode calculations support proposals that the chromophore structures in P(r) and P(fr) are C(15)-Z,syn and C(15)-E,anti, respectively. The intensities of the C(15)-hydrogen out-of-plane, C=C and C-C torsional, and in-plane ring modes in both P(r) and P(fr) suggest that the initial photochemistry involves simultaneous bond rotations at the C(15)-methine bridge coupled to C(15)-H wagging and D-ring rotation. The strong nonbonded interactions of the C- and D-ring methyl groups in the C(15)-E,anti P(fr) chromophore structure indicated by the intense 814 cm(-1) C(15) HOOP mode suggest that the excited state of P(fr) and its photoproduct states are strongly coupled.

  10. Far infrared and low frequency Raman spectra and conformational stability of gaseous chloromethylcyclopropane and bromomethylcyclopropane

    NASA Astrophysics Data System (ADS)

    Durig, J. R.; Godbey, S. E.; Faust, S. A.

    1988-05-01

    The far-IR (350-50 cm -1) and low frequency Raman spectra (200-70 cm -1) of gaseous chloro- and bromomethylcyclopropane have been recorded. The asymmetric torsion arising from the gauche conformer of the bromide has been observed at 91.8 cm -1 but the corresponding transition for the cis conformer was not observed. However, IR bands for all the skeletal bending modes indicate the presence of a second conformer at ambient temperature. For chloromethylcyclopropane, the asymmetric torsions of both the cis and the gauche conformers have been observed at 99.54 and 96.84 cm -1, respectively, along with two excited state transitions for each conformer. From these data a potential function for the chloromethylcyclopropane molecule has been calculated and the determined potential constants have the following values: V1=200±65, V2=-34±16, and V3=1138±6 cm -1 with the gauche conformer calculated to be more stable by 178±87 cm -1 (510±25 cal mol -1) than the cis conformer. The gauche to cis barrier is 1239 cm -1 (3.54 kcal mol -1) and the gauche to gauche barrier is 1114 cm -1 (3.19 kcal mol -1). A variable temperature Raman study of the gaseous chloride was carried out and the enthalpy difference was found to be Δ H=273±108 cm -1 (782±309 cal mol -1) with the gauche conformer being more stable. The results of this study are compared with previous studies of these and similar molecules.

  11. Size effects in near-ultraviolet Raman spectra of few-nanometer-thick silicon-on-insulator nanofilms

    SciTech Connect

    Poborchii, Vladimir Morita, Yukinori; Tada, Tetsuya; Geshev, Pavel I.; Utegulov, Zhandos N.; Volkov, Alexey

    2016-04-21

    We have fabricated Si-on-insulator (SOI) layers with a thickness h{sub 1} of a few nanometers and examined them by Raman spectroscopy with 363.8 nm excitation. We have found that phonon and electron confinement play important roles in SOI with h{sub 1} < 10 nm. We have confirmed that the first-order longitudinal optical phonon Raman band displays size-induced major homogeneous broadening due to phonon lifetime reduction as well as minor inhomogeneous broadening due to wave vector relaxation (WVR), both kinds of broadening being independent of temperature. Due to WVR, transverse acoustic (TA) phonons become Raman-active and give rise to a broad band in the range of 100–200 cm{sup −1}. Another broad band appeared at 200–400 cm{sup −1} in the spectrum of SOI is attributed to the superposition of 1st order Raman scattering on longitudinal acoustic phonons and 2nd order scattering on TA phonons. Suppression of resonance-assisted 2-nd order Raman bands in SOI spectra is explained by the electron-confinement-induced direct band gap enlargement compared to bulk Si, which is confirmed by SOI reflection spectra.

  12. Raman spectra of epitaxial graphene on SiC and of epitaxial graphene transferred to SiO2.

    PubMed

    Lee, Dong Su; Riedl, Christian; Krauss, Benjamin; von Klitzing, Klaus; Starke, Ulrich; Smet, Jurgen H

    2008-12-01

    Raman spectra were measured for mono-, bi-, and trilayer graphene grown on SiC by solid state graphitization, whereby the number of layers was preassigned by angle-resolved ultraviolet photoemission spectroscopy. It was found that the only unambiguous fingerprint in Raman spectroscopy to identify the number of layers for graphene on SiC(0001) is the line width of the 2D (or D*) peak. The Raman spectra of epitaxial graphene show significant differences as compared to micromechanically cleaved graphene obtained from highly oriented pyrolytic graphite crystals. The G peak is found to be blue-shifted. The 2D peak does not exhibit any obvious shoulder structures, but it is much broader and almost resembles a single-peak even for multilayers. Flakes of epitaxial graphene were transferred from SiC onto SiO2 for further Raman studies. A comparison of the Raman data obtained for graphene on SiC with data for epitaxial graphene transferred to SiO2 reveals that the G peak blue-shift is clearly due to the SiC substrate. The broadened 2D peak however stems from the graphene structure itself and not from the substrate.

  13. DFT study of Raman spectra of phosphorus-containing dendrons built from cyclotriphosphazene core with terminal carbamate and ester groups.

    PubMed

    Furer, V L; Vandyukov, A E; Fuchs, S; Majoral, J P; Caminade, A M; Kovalenko, V I

    2014-01-01

    The FT Raman spectra of the zero (Gv0) and first generations (Gv1) of phosphorus-containing dendrons with terminal carbamate groups and one ester function and [2-(4-hydroxyphenyl)ethyl]-carbamic acid tert-butyl ester (C) have been recorded and analyzed. The lines of free ν(C=O) bonds are not observed in the experimental Raman spectrum of C and thus association of carbamate groups by hydrogen bonds occur. The frequencies of ν(C=O) lines in the experimental Raman spectrum reveal the presence of the different types of H-bonds in the amorphous state of Gv0. Density functional theory (DFT) calculations of C gave geometrical parameters for the t-g-, g-g-, tg-, gg-conformers. The most stable is the gg-conformer. The structural optimization and normal mode analysis were performed for dendrons on the basis of the DFT. The calculated geometrical parameters, harmonic vibrational frequencies and Raman intensities are predicted in a good agreement with the experimental data. The experimental Raman spectra of dendrons were interpreted by means of potential energy distribution. Relying on DFT calculations the lines of a core, repeating units and terminal groups of dendrons were assigned. The polarizabilities and lipophilicity of dendrons were estimated.

  14. Size effects in near-ultraviolet Raman spectra of few-nanometer-thick silicon-on-insulator nanofilms

    NASA Astrophysics Data System (ADS)

    Poborchii, Vladimir; Morita, Yukinori; Tada, Tetsuya; Geshev, Pavel I.; Utegulov, Zhandos N.; Volkov, Alexey

    2016-04-01

    We have fabricated Si-on-insulator (SOI) layers with a thickness h1 of a few nanometers and examined them by Raman spectroscopy with 363.8 nm excitation. We have found that phonon and electron confinement play important roles in SOI with h1 < 10 nm. We have confirmed that the first-order longitudinal optical phonon Raman band displays size-induced major homogeneous broadening due to phonon lifetime reduction as well as minor inhomogeneous broadening due to wave vector relaxation (WVR), both kinds of broadening being independent of temperature. Due to WVR, transverse acoustic (TA) phonons become Raman-active and give rise to a broad band in the range of 100-200 cm-1. Another broad band appeared at 200-400 cm-1 in the spectrum of SOI is attributed to the superposition of 1st order Raman scattering on longitudinal acoustic phonons and 2nd order scattering on TA phonons. Suppression of resonance-assisted 2-nd order Raman bands in SOI spectra is explained by the electron-confinement-induced direct band gap enlargement compared to bulk Si, which is confirmed by SOI reflection spectra.

  15. Transient Raman Spectra, Structure and Thermochemistry of the Thiocyanate Dimer Radical Anion in Water

    NASA Astrophysics Data System (ADS)

    Janik, Ireneusz; Tripathi, G. N. R.; Carmichael, Ian

    2017-06-01

    Time-resolved resonance-enhanced Stokes and anti-Stokes Raman spectra of the thiocyanate dimer radical anion, (SCN)_{2}^{-}, prepared by pulse radiolysis in water, have been obtained and interpreted in conjunction with theoretical calculations to provide detailed information on the molecular geometry and bond properties of the species. The structural properties of the radical are used to develop a molecular perspective on its thermochemistry in aqueous solution. Twenty-nine Stokes Raman bands of the radical observed in the 120-4200 \\wn region are assigned in terms of the strongly enhanced 220 \\wn fundamental, weakly enhanced 721 \\wn, and moderately enhanced 2073 \\wn fundamentals, their overtones and combinations. Calculations by range-separated hybrid (RSH) density functionals (ωB97x and LC-ωPBE) support the spectroscopic assignments of the 220 \\wn vibration to a predominantly SS stretching mode and the features at 721 \\wn and 2073 \\wn to CS and CN stretching modes, respectively. The corresponding bond lengths are 2.705 (+0.036) Å, 1.663 (+0.001) Å and 1.158 (+0.002) Å. A first order anharmonicity of 1 \\wn determined for the SS stretching mode suggests a convergence of vibrational states at an energy 1.5 eV, using the Birch-Sponer extrapolation. This value, estimated for the radical confined in solvent cage, compares well with the calculated gas-phase energy required for the radical (1.22 eV) to dissociate into SCN and SCN^{-} fragments. The enthalpy of dissociation drops to 0.63 eV in water when solvent dielectric effects on the radical and its dissociation products upon S-S bond scission are incorporated in the calculations. No frequency shift or spectral broadening was observed between light and heavy water solvents, indicating that the motion of solvent molecules in the hydration shell have no perceptible effect on the intramolecular dynamics of the radical. The Stokes and anti-Stokes Raman frequencies were found to be identical within the

  16. Transient Raman spectra, structure, and thermochemistry of the thiocyanate dimer radical anion in water.

    PubMed

    Janik, Ireneusz; Carmichael, Ian; Tripathi, G N R

    2017-06-07

    Time-resolved resonance-enhanced Stokes and anti-Stokes Raman spectra of the thiocyanate dimer radical anion, (SCN)2(•-), prepared by pulse radiolysis in water, have been obtained and interpreted in conjunction with theoretical calculations to provide detailed information on the molecular geometry and bond properties of the species. The structural properties of the radical are used to develop a molecular perspective on its thermochemistry in an aqueous solution. Twenty-nine Stokes Raman bands of the radical observed in the 120-4200 cm(-1) region are assigned in terms of the strongly enhanced 220 cm(-1) fundamental, weakly enhanced 721 cm(-1), and moderately enhanced 2073 cm(-1) fundamentals, their overtones, and combinations. Calculations by range-separated hybrid density functionals (ωB97x and LC-ωPBE) support the spectroscopic assignments of the 220 cm(-1) vibration to a predominantly SS stretching mode and the features at 721 cm(-1) and 2073 cm(-1) to CS and CN symmetric stretching modes, respectively. The corresponding bond lengths are 2.705 (±0.036) Å, 1.663 (±0.001) Å, and 1.158 (±0.002) Å. A first order anharmonicity of 1 cm(-1) determined for the SS stretching mode suggests a convergence of vibrational states at an energy of ∼1.5 eV, using the Birge-Sponer extrapolation. This value, estimated for the radical confined in solvent cage, compares well with the calculated gas-phase energy of 1.26 ± 0.04 eV required for the radical to dissociate into SCN(•) and SCN(-) fragments. The enthalpy of dissociation drops to 0.60 ± 0.03 eV in water when solvent dielectric effects on the radical and its dissociation products upon S-S bond scission are incorporated in the calculations. No frequency shift or spectral broadening was observed between light and heavy water solvents, indicating that the motion of solvent molecules in the hydration shell has no perceptible effect on the intramolecular dynamics of the radical. The Stokes and anti-Stokes Raman

  17. Transient Raman spectra, structure, and thermochemistry of the thiocyanate dimer radical anion in water

    NASA Astrophysics Data System (ADS)

    Janik, Ireneusz; Carmichael, Ian; Tripathi, G. N. R.

    2017-06-01

    Time-resolved resonance-enhanced Stokes and anti-Stokes Raman spectra of the thiocyanate dimer radical anion, (SCN)2•-, prepared by pulse radiolysis in water, have been obtained and interpreted in conjunction with theoretical calculations to provide detailed information on the molecular geometry and bond properties of the species. The structural properties of the radical are used to develop a molecular perspective on its thermochemistry in an aqueous solution. Twenty-nine Stokes Raman bands of the radical observed in the 120-4200 cm-1 region are assigned in terms of the strongly enhanced 220 cm-1 fundamental, weakly enhanced 721 cm-1, and moderately enhanced 2073 cm-1 fundamentals, their overtones, and combinations. Calculations by range-separated hybrid density functionals (ωB97x and LC-ωPBE) support the spectroscopic assignments of the 220 cm-1 vibration to a predominantly SS stretching mode and the features at 721 cm-1 and 2073 cm-1 to CS and CN symmetric stretching modes, respectively. The corresponding bond lengths are 2.705 (±0.036) Å, 1.663 (±0.001) Å, and 1.158 (±0.002) Å. A first order anharmonicity of 1 cm-1 determined for the SS stretching mode suggests a convergence of vibrational states at an energy of ˜1.5 eV, using the Birge-Sponer extrapolation. This value, estimated for the radical confined in solvent cage, compares well with the calculated gas-phase energy of 1.26 ± 0.04 eV required for the radical to dissociate into SCN• and SCN- fragments. The enthalpy of dissociation drops to 0.60 ± 0.03 eV in water when solvent dielectric effects on the radical and its dissociation products upon S-S bond scission are incorporated in the calculations. No frequency shift or spectral broadening was observed between light and heavy water solvents, indicating that the motion of solvent molecules in the hydration shell has no perceptible effect on the intramolecular dynamics of the radical. The Stokes and anti-Stokes Raman frequencies were found to be

  18. Pressure-tuning micro-Raman spectra of artists' pigments: α- and β-copper phthalocyanine polymorphs.

    PubMed

    Beaulieu-Houle, Guillaume; Gilson, Denis F R; Butler, Ian S

    2014-01-03

    The two polymorphs of copper phthalocyanine, α- and β-CuPc, have been examined by micro-Raman spectroscopy at pressures approaching 5.0 GPa. The metastable α-polymorph does not exhibit any structural changes, while the more thermodynamically stable β-polymorph does exhibit a reversible phase transition at 2.0 GPa. The pressure dependences (dν/dP) for a selected number of vibrational modes are reported. Two regions of the Raman spectra, 800-900 cm(-1) and 1100-1200 cm(-1), are sensitive to pressure such that they can be used as indicators of the polymorphic form.

  19. 266 nm CH3I photodissociation: CH3 spectra and population distributions by coherent Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zahedi, Mansour; Harrison, James A.; Nibler, Joseph W.

    1994-03-01

    High resolution coherent anti-Stokes Raman spectroscopy has been used to study the symmetric CH stretching mode of methyl radical formed by UV laser photolysis of CH3I cooled in a free jet expansion. Spectra obtained under near-nascent conditions (˜3 to ˜6 collisions) show that most of the CH3 product is formed in the ground vibrational state, with little excitation seen in the ν2 out-of-plane bending coordinate [v2=1/v2=0, population ratio 0.27(10)]. This is in accord with recent theoretical calculations favoring slow, adiabatic CH3 relaxation from a pyramidal to planar structure as the C-I bond breaks. Extensive N,K rotational structure is resolved and the distributions obtained lend support to those deduced for nascent CH3 by Chandler and co-workers from modeling of unresolved resonance enhanced multiphoton ionization spectra. The results are consistent with conservation during dissociation of CH3 ortho-para nuclear spin forms and of K spinning angular momentum about the symmetry axis. CH3 product tumbling motion is slightly greater (1-2 units of angular momentum) than predicted theoretically. Rapid collisional excitation of higher rotational levels is seen and the rich spectrum observed after ˜50 collisions has been analyzed to give improved or new vibrational-rotational parameters for 1000 and 1100 states. The 1100 band origin is determined to be 2996.21(4) cm-1, yielding -8.23(5) cm-1 for the x12 anharmonicity constant.

  20. Applications of Group Theory: Infrared and Raman Spectra of the Isomers of cis- and trans-1,2-DICHLOROETHYLENE

    NASA Astrophysics Data System (ADS)

    Craig, Norman C.

    2015-06-01

    A study of the vibrational spectra of cis- and trans-1,2-dichloroethylene provides an excellent way for undergraduates to gain experience with the application of group theory in the physical chemistry laboratory. Although the group vibrations are similar for these two molecules, the selection rules for infrared (IR) and Raman spectra differ significantly. Most of the transitions for the fundamentals of the cis isomer of C2v symmetry are both IR and Raman active. Mutual exclusion for the vibrational transitions applies to the centrosymmetric trans isomer of C2h symmetry. Thus, half the transitions for the trans isomer are IR active and half are Raman active. The two isomers are volatile enough that gas-phase IR spectra can be recorded at room temperature. Band shapes in gas-phase IR spectra provide additional evidence for assignments of fundamentals. The two isomers are small enough that good quality quantum chemical calculations of harmonic frequencies can be done by students with commercial software.

  1. Measurement and Simulation of Spontaneous Raman Scattering Spectra in High-Pressure, Fuel-Rich H2-Air Flames

    NASA Technical Reports Server (NTRS)

    Kojima, Jun; Nguyen, Quang-Viet

    2003-01-01

    Rotational vibrational spontaneous Raman spectra (SRS) of H2, N2, and H2O have been measured in H2-air flames at pressures up to 30 atm as a first stem towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. A newly developed high-pressure burner facility provides steady, reproducible flames with a high degree of flow precision. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in terms of spectral resolution, wavelength coverage, and signal-to-noise ratio for use in future reference standards. The fully resolved Stokes and anti-Stokes shifted SRS spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a non-intensified CCD spectrograph with a high-speed shutter. Reasonable temperatures were determined via the intensity distribution of rotational H2 lines at stoichiometry and fuel-rich conditions. Theoretical Raman spectra of H2 were computed using a semi-classical harmonic-oscillator model with recent pressure broadening data and were compared with experimental results. The data and simulation indicated that high-J rotational lines of H2 might interfere with the N2 vibrational Q-branch lines, and this could lead to errors in N2-Raman thermometry based on the line-fitting method. From a comparison of N2 Q-branch spectra in lean H2 low-pressure (1.2 atm) and high-pressure (30 atm) flames, we found no significant line-narrowing or -broadening effects at the current spectrometer resolution of 0.04 nm.

  2. Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

    SciTech Connect

    Burris, Paul C.; Laage, Damien; Thompson, Ward H.

    2016-05-20

    Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this Paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. Lastly, the simulated spectra indicate that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.

  3. Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

    DOE PAGES

    Burris, Paul C.; Laage, Damien; Thompson, Ward H.

    2016-05-20

    Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this Paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is usedmore » to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. Lastly, the simulated spectra indicate that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.« less

  4. Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

    SciTech Connect

    Burris, Paul C.; Laage, Damien; Thompson, Ward H.

    2016-05-20

    Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this Paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. Lastly, the simulated spectra indicate that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.

  5. Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores.

    PubMed

    Burris, Paul C; Laage, Damien; Thompson, Ward H

    2016-05-21

    Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. The simulated spectra indicates that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.

  6. Structural and vibrational characterization of sugar arabinitol structures employing micro-Raman spectra and DFT calculations

    NASA Astrophysics Data System (ADS)

    Hédoux, Alain; Guinet, Yannick; Carpentier, Laurent; Paccou, Laurent; Derollez, Patrick; Brandán, Silvia Antonia

    2017-06-01

    In this work, three monomeric forms of arabinitol, usually named arabitol, and their dimeric species have been structural and vibrationally studied by using the micro-Raman spectra in the solid phase accomplished with theoretical calculations based on the theory of the functional of the density (DFT). The hybrid B3LYP method was used for all the calculations together with the 6-31G* and 6-311++g** basis sets. Two different L structures with minima energies were predicted in accordance to the two polymorphic structures revealed by recent X-ray diffraction experiments. The studies by natural bond orbital (NBO) calculations reveals high stabilities of the L form as compared with the D one but the topological properties by using the atoms in molecules (AIM) suggest a higher stability of the D form due to a strong H bond interactions. The scaled mechanical force fields (SQMFF) procedure was used to perform the complete vibrational assignments for the monomeric forms and their dimer. On the other hand, the similarity in the gap values computed for the three forms of arabitol with those observed for sucrose, trehalose, maltose and lactose in gas phase at the same level of theory could partially explain the sweetening property of this alcohol. In addition, the influences of the size of the basis set on some properties were evidenced.

  7. Pseudogap and Superconducting Gap in the Electronic Raman Spectra of Underdoped Cuprates

    SciTech Connect

    Nemetschek, R.; Opel, M.; Hoffmann, C.; Mueller, P.F.; Hackl, R.; Berger, H.; Forro, L.; Erb, A.; Walker, E.

    1997-06-01

    Raman spectra of YBa{sub 2}Cu {sub 3}O{sub 7-x} and Bi{sub 2}Sr {sub 2}(Ca {sub 0.62}Y{sub 0.38})Cu{sub 2}O{sub 8+{delta}} with T{sub c}{congruent}0.65T{sup max}{sub c} in the underdoped regime of the phase diagram are studied as a function of temperature and polarization. At B{sub 2g}(xy) symmetry a reduction of spectral weight by 10{percent} for frequencies less than 700cm{sup -1} or 15k{sub B}T{sub c} is found below approximately 200K. Below T{sub c}, a superconducting gap opens up which closely resembles that observed at higher doping levels. It is compatible with d{sub x{sup 2}-y{sup 2}} pairing and its amplitude 2{Delta}{sub 0} can be estimated to be 8k{sub B}T{sub c}. {copyright} {ital 1997} {ital The American Physical Society}

  8. Infrared and polarized Raman spectra of tetramethyl ammonium cerium(III) bis(sulfate) trihydrate

    SciTech Connect

    Jayasree, R.S.; Nayar, V.U.; Jordanovska, V.

    1996-11-15

    Infrared and polarized Raman spectra of (CH{sub 3}){sub 4}NCe(SO{sub 4}){sub 2}{center_dot}3H{sub 2}O are recorded and analyzed. Bands are assigned on the basis on (CH{sub 3}){sub 4}N{sup +}, SO{sub 4}{sup 2-}, and H{sub 2}O vibrations. Methyl rotational modes and tetramethyl skeletal bending modes are not observed in the IR spectrum confirming the X-ray data that the tetramethyl ammonium ion retains its T{sub d} symmetry in the crystal. Small splitting observed in the nondegenerate modes of SO{sub 4}{sup 2-} ions implies slight distortion of the anions in the crystal. The existence of two types of SO{sub 4}{sup 2-} ions cannot be confirmed. The shifting of the stretching and bending vibrations of the water molecules from the free state value confirms the formation of hydrogen bonds of varying strengths in the crystal.

  9. Glue function of optimally and overdoped cuprates from inversion of the Raman spectra

    NASA Astrophysics Data System (ADS)

    Fanfarillo, L.; Mori, M.; Campetella, M.; Grilli, M.; Caprara, S.

    2016-02-01

    We address the issue of identifying the mediators of effective interactions in cuprates superconductors. Specifically, we use inversion theory to analyze Raman spectra of optimally and over-doped La2-x Sr x CuO4 samples. This allows us to extract the so-called glue function without making any a priori assumption based on any specific model. We use instead two different techniques, namely the singular value decomposition and a multi-rectangle decomposition. With both techniques we find consistent results showing that: (i) two distinct excitations are responsible for the glue function, which have completely different doping dependence. One excitation becomes weak above optimal doping, where on the contrary the other keeps (or even slightly increases) its strength; (ii) there is a marked temperature dependence on the weight and spectral distribution of these excitations, which therefore must have a somewhat critical character. It is quite natural to identify and characterize these two distinct excitations as damped antiferromagnetic spin waves and damped charge density waves, respectively. This sets the stage for a scenario in which superconductivity is concomitant and competing with a charge ordering instability.

  10. Glue function of optimally and overdoped cuprates from inversion of the Raman spectra.

    PubMed

    Fanfarillo, L; Mori, M; Campetella, M; Grilli, M; Caprara, S

    2016-02-17

    We address the issue of identifying the mediators of effective interactions in cuprates superconductors. Specifically, we use inversion theory to analyze Raman spectra of optimally and over-doped La2-x Sr x CuO4 samples. This allows us to extract the so-called glue function without making any a priori assumption based on any specific model. We use instead two different techniques, namely the singular value decomposition and a multi-rectangle decomposition. With both techniques we find consistent results showing that: (i) two distinct excitations are responsible for the glue function, which have completely different doping dependence. One excitation becomes weak above optimal doping, where on the contrary the other keeps (or even slightly increases) its strength; (ii) there is a marked temperature dependence on the weight and spectral distribution of these excitations, which therefore must have a somewhat critical character. It is quite natural to identify and characterize these two distinct excitations as damped antiferromagnetic spin waves and damped charge density waves, respectively. This sets the stage for a scenario in which superconductivity is concomitant and competing with a charge ordering instability.

  11. Raman spectra of lithium niobate crystals heavily doped with zinc and magnesium

    NASA Astrophysics Data System (ADS)

    Sidorov, N. V.; Palatnikov, M. N.

    2016-12-01

    We have examined the Raman spectra of heavily doped lithium niobate single crystals (at close-to-threshold concentrations of doping cations): LiNbO3:Zn (4.5 mol % ZnO), LiNbO3:Mg (5.01 mol %):Fe (0.005 mol %), LiNbO3:Mg (5.1 mol %), and LiNbO3:Mg (5.3 mol % MgO). Low-intensity lines with frequencies at 209, 230, 298, 694, and 880 cm-1 have been revealed for the first time. Analysis of the data from the literature on lattice dynamics calculations from first principles (ab initio) does not make it possible to unambiguously state that these lines correspond to fundamental vibrations of the A2 symmetry species, which are forbidden for the C3 V 6 ( R3c) space group. At the same time, ab initio calculations unambiguously indicate that the experimentally observed low-intensity "superfluous" lines with the frequencies at 104 and 119 cm-1 cannot correspond to vibrations of the A2 symmetry species. It is most likely that they correspond to two-particle states of acoustic phonons with a total wave vector equal to zero.

  12. Effect of annealing on Raman spectra of monolayer graphene samples gradually disordered by ion irradiation

    NASA Astrophysics Data System (ADS)

    Zion, E.; Butenko, A.; Kaganovskii, Yu.; Richter, V.; Wolfson, L.; Sharoni, A.; Kogan, E.; Kaveh, M.; Shlimak, I.

    2017-03-01

    Raman scattering spectra (RS) of two series of monolayer graphene samples irradiated with various doses of C + and Xe + ions were measured after annealing in a high vacuum and in forming gas (95%Ar + 5%H2). It is shown that annealing below 500 °C leads to a significant decrease in both the D-line, associated with defects, and the 2D-line, associated with the intact lattice structure. This can be explained by annealing-induced enhanced doping. Further annealing in a vacuum up to 1000 °C leads to a significant increase in the 2D-line together with a continuous decrease in the D-line. This gives evidence for the partial removal of the defects and restoration of the damaged lattice. Annealing in forming gas is less effective in this sense. A blue shift of all lines is observed after annealing. It is shown that below 500 °C, unintentional doping is the main origin of the shift. At higher annealing temperatures, the blue shift is mainly due to lattice strain arising because of mismatch between the thermal expansion coefficients of graphene and the substrate. Inhomogeneous distribution of stress and doping across the samples lead to the correlated variation of the height and peak position of RS lines.

  13. Ultranarrow resonance peaks in the transmission and reflection spectra of a photonic crystal cavity with Raman gain

    SciTech Connect

    Arkhipkin, V. G.; Myslivets, S. A.

    2009-12-15

    The Raman gain of a probe light in a three-state LAMBDA scheme placed into a defect of a one-dimensional photonic crystal is studied theoretically. We show that there exists a pump intensity range, where the transmission and reflection spectra of the probe field exhibit simultaneously occurring narrow peaks (resonances) whose position is determined by the Raman resonance. Transmission and reflection coefficients can be larger than unity at pump intensities on the order of tens of muW/cm{sup 2}. When the pump intensity is outside this region, the peak in the transmission spectrum turns into a narrow dip. The nature of narrow resonances is attributed to a drastic dispersion of the nonlinear refractive index in the vicinity of the Raman transition, which leads to a significant reduction in the group velocity of the probe wave.

  14. Molecular component distribution imaging of living cells by multivariate curve resolution analysis of space-resolved Raman spectra

    NASA Astrophysics Data System (ADS)

    Ando, Masahiro; Hamaguchi, Hiro-o.

    2014-01-01

    Label-free Raman microspectroscopy combined with a multivariate curve resolution (MCR) analysis can be a powerful tool for studying a wide range of biomedical molecular systems. The MCR with the alternating least squares (MCR-ALS) technique, which retrieves the pure component spectra from complicatedly overlapped spectra, has been successfully applied to in vivo and molecular-level analysis of living cells. The principles of the MCR-ALS analysis are reviewed with a model system of titanium oxide crystal polymorphs, followed by two examples of in vivo Raman imaging studies of living yeast cells, fission yeast, and budding yeast. Due to the non-negative matrix factorization algorithm used in the MCR-ALS analysis, the spectral information derived from this technique is just ready for physical and/or chemical interpretations. The corresponding concentration profiles provide the molecular component distribution images (MCDIs) that are vitally important for elucidating life at the molecular level, as stated by Schroedinger in his famous book, "What is life?" Without any a priori knowledge about spectral profiles, time- and space-resolved Raman measurements of a dividing fission yeast cell with the MCR-ALS elucidate the dynamic changes of major cellular components (lipids, proteins, and polysaccharides) during the cell cycle. The MCR-ALS technique also resolves broadly overlapped OH stretch Raman bands of water, clearly indicating the existence of organelle-specific water structures in a living budding yeast cell.

  15. Interpretation of the infrared and Raman spectra of zwitterionic push-pull dyes based on quinoidal thiazole

    NASA Astrophysics Data System (ADS)

    Luis Zafra, José; Andreu, Raquel; Galán, Elena; Orduna, Jesús; Garín, Javier; Martín Ortiz, Jorge; López Navarrete, Juan T.; Casado, Juan

    2013-07-01

    The infrared and Raman spectra of a donor (dithiole)-acceptor (dicyano) compound having a quinoidal thiazole bridge connecting the two electro-active groups have been recorded and the vibrational properties described on the basis of MP2 and DFT theoretical approaches. The spectroscopic data have been interpreted accounting for: (i) charge polarization or donor-acceptor charge separation in the S0 ground electronic state from the infrared spectrum; (ii) π-conjugation on the donor-(π-spacer)-acceptor sequence from the non-resonant Raman spectrum; and (iii) intramolecular donor-to-acceptor charge transfer character of the S0 → S1 excitation from the resonant Raman spectrum; and (iv) dependence of the non-resonant and resonant Raman spectra varying the spacer and the donor group. This paper highlights the interesting combination of vibrational spectroscopy and theoretical modeling in order to get insight on the relevant electro-optical and molecular properties on these compounds which are items of interest to develop organic molecules for non-linear optical applications.

  16. Molecular component distribution imaging of living cells by multivariate curve resolution analysis of space-resolved Raman spectra.

    PubMed

    Ando, Masahiro; Hamaguchi, Hiro-o

    2014-01-01

    Label-free Raman microspectroscopy combined with a multivariate curve resolution (MCR) analysis can be a powerful tool for studying a wide range of biomedical molecular systems. The MCR with the alternating least squares (MCR-ALS) technique, which retrieves the pure component spectra from complicatedly overlapped spectra, has been successfully applied to in vivo and molecular-level analysis of living cells. The principles of the MCR-ALS analysis are reviewed with a model system of titanium oxide crystal polymorphs, followed by two examples of in vivo Raman imaging studies of living yeast cells, fission yeast, and budding yeast. Due to the non-negative matrix factorization algorithm used in the MCR-ALS analysis, the spectral information derived from this technique is just ready for physical and/or chemical interpretations. The corresponding concentration profiles provide the molecular component distribution images (MCDIs) that are vitally important for elucidating life at the molecular level, as stated by Schroedinger in his famous book, "What is life?" Without any a priori knowledge about spectral profiles, time- and space-resolved Raman measurements of a dividing fission yeast cell with the MCR-ALS elucidate the dynamic changes of major cellular components (lipids, proteins, and polysaccharides) during the cell cycle. The MCR-ALS technique also resolves broadly overlapped OH stretch Raman bands of water, clearly indicating the existence of organelle-specific water structures in a living budding yeast cell.

  17. DFT study of structure, IR and Raman spectra of the fluorescent "Janus" dendron built from cyclotriphosphazene core

    NASA Astrophysics Data System (ADS)

    Furer, V. L.; Vandyukova, I. I.; Vandyukov, A. E.; Fuchs, S.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

    2011-11-01

    The FTIR and FT-Raman spectra of the zero generation dendron, possessing five fluorescent dansyl terminal groups, cyclotriphosphazene core, and one carbamate function G0v were studied. The structural optimization and normal mode analysis were performed for G0v dendron on the basis of the density functional theory (DFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendron molecule G0v has a concave lens structure with slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of G0v dendron were interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The frequency of ν(N-H) band in the IR spectrum reveal the presence of H-bonds in the G0v dendron.

  18. Raman spectra investigation of the defects of chemical vapor deposited multilayer graphene and modified by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Li, Zongyao; Xu, Yu; Cao, Bing; Qi, Lin; He, Shunyu; Wang, Chinhua; Zhang, Jicai; Wang, Jianfeng; Xu, Ke

    2016-11-01

    Graphene, a two dimensional material, can be modified its properties by defects engineering. Here, we present Raman spectra studies of the multilayer graphene (MLG) fabricated by low-pressure chemical vapor deposition over copper foil, and report that the defects of MLG can be controlled by adjusting methane concentration. Moreover, MLG can be changed from metallic to semiconductoring properties by using oxygen plasma treatment, and we investigate the defects evolution of the graphene after exposing to oxygen plasma by Raman spectra. Our results indicate that the amount of defects in graphene can be changed by regulating the methane concentration and oxygen plasma exposure times, but the primary type of defect in MLG is still boundary-like defect. It is valuable for understanding the physics of defects evolution through artificially generated defects, and such defect engineering will greatly open up the future application of the novel material.

  19. Quantum-mechanical calculation of the intensity distribution in Raman and resonance Raman spectra of a phenylalanine aqueous solution

    NASA Astrophysics Data System (ADS)

    Burova, T. G.; Shcherbakov, R. S.

    2017-03-01

    Quantum-mechanical calculations of the intensity distribution in the resonance Raman spectrum of an aqueous solution of phenylalanine, excited by light with wavelengths of 193, 204, 218, and 235 nm, and in the nonresonant Raman spectrum excited at a wavelength of 488 nm have been performed. The calculation results are in satisfactory agreement with the experimental data in the literature. Spectral lines characteristic of phenylalanine are observed, which can be used as markers when analyzing the peptide structure. It is noted that the contribution of highly excited electronic states (spaced by less than 10 eV from the resonant lines) to the scattering tensor components must be taken into account. The important role of the Herzberg-Teller effect in the description of spectral intensity distribution is demonstrated.

  20. The Raman spectra of N-14O2 and N-15O2 solids at 20 K

    NASA Technical Reports Server (NTRS)

    Durig, J. R.; Griffin, M. G.

    1976-01-01

    The Raman spectra of N-14O2 and N-15O2 have been studied at 20 K. The far infrared of N-14O2 at 20 K was also measured. The data were assigned on the basis of a C-sub 2 nu molecular model. Normal coordinate calculations were performed for a variety of assignments. The assignment that yielded the best fit is presented. The solid state effects are discussed.

  1. DFT Study of Hydrogen-Bonding Interaction, Solvation Effect, and Electric-Field Effect on Raman Spectra of Hydrated Proton.

    PubMed

    Pang, Ran; Yu, Li-Juan; Zhang, Meng; Tian, Zhong-Qun; Wu, De-Yin

    2016-10-12

    Strong hydrogen-bonding interaction and Raman spectra of hydrated proton have been investigated using hybrid density functional theory method B3LYP. The solvation model of density (SMD) approach is employed in the present calculation to simulate hydrated protons in aqueous solution. Focusing on the different hydrogen-bonded Eigen-water and Zundel-water interactions, we present a better assignment of Raman signals of hydrated proton on the basis of vibrational analysis in different environments. Our results showed that B3LYP calculations could give a good prediction for characteristic vibrational frequencies of Eigen and Zundel isomers in liquid phase. The O-H stretching vibrational frequencies from Eigen and Zundel units are very sensitive to hydrogen-bonding interaction with solvent water molecules. Moreover, the solvation effect and the external electric-field effect lead to the proton deviating from the central position of Zundel structure and finally resulting in a transition to Eigen one in aqueous solution. Furthermore, by combining theoretical prediction and Raman scattering theory, we calculate absolute Raman intensities of characteristic signals based on the polarizability tensor derivatives of hydrated proton clusters. This is very helpful to infer the microstructure of hydrated protons in aqueous solution by using Raman measurements.

  2. Influence of ageing on Raman spectra and the conductivity of monolayer graphene samples irradiated by heavy and light ions

    NASA Astrophysics Data System (ADS)

    Butenko, A.; Zion, E.; Kaganovskii, Yu.; Wolfson, L.; Richter, V.; Sharoni, A.; Kogan, E.; Kaveh, M.; Shlimak, I.

    2016-07-01

    The influence of long-term ageing (about one year) on the Raman scattering (RS) spectra and the temperature dependence of conductivity has been studied in two series of monolayer graphene samples irradiated by different doses of C+ and Xe+ ions. It is shown that the main result of ageing consists of changes in the intensity and position of D- and G- and 2D-lines in RS spectra and in an increase of the conductivity. The observed effects are explained in terms of an increase of the radius of the "activated" area around structural defects.

  3. Influence of ageing on Raman spectra and the conductivity of monolayer graphene samples irradiated by heavy and light ions

    SciTech Connect

    Butenko, A.; Zion, E.; Richter, V.; Sharoni, A.; Kaganovskii, Yu.; Wolfson, L.; Kogan, E.; Kaveh, M.; Shlimak, I.

    2016-07-28

    The influence of long-term ageing (about one year) on the Raman scattering (RS) spectra and the temperature dependence of conductivity has been studied in two series of monolayer graphene samples irradiated by different doses of C{sup +} and Xe{sup +} ions. It is shown that the main result of ageing consists of changes in the intensity and position of D- and G- and 2D-lines in RS spectra and in an increase of the conductivity. The observed effects are explained in terms of an increase of the radius of the “activated” area around structural defects.

  4. Gas-phase thermometry using delayed-probe-pulse picosecond coherent anti-Stokes Raman scattering spectra of H2.

    PubMed

    Stauffer, Hans U; Kulatilaka, Waruna D; Hsu, Paul S; Gord, James R; Roy, Sukesh

    2011-02-01

    We report the development and application of a simple theoretical model for extracting temperatures from picosecond-laser-based coherent anti-Stokes Raman scattering (CARS) spectra of H2 obtained using time-delayed probe pulses. This approach addresses the challenges associated with the effects of rotational-level-dependent decay lifetimes on time-delayed probing for CARS thermometry. A simple procedure is presented for accurate temperature determination based on a Boltzmann distribution using delayed-probe-pulse vibrational CARS spectra of H2; this procedure requires measurement at only a select handful of probe-pulse delays and requires no assumptions about sample environment.

  5. The spectroscopic (FTIR, FT-Raman and UV-Vis spectra), DFT and normal coordinate computations of m-nitromethylbenzoate.

    PubMed

    Gnanasambandan, T; Gunasekaran, S; Seshadri, S

    2013-08-01

    A combined experimental and theoretical study on molecular structure, vibrational spectra, NBO and UV-spectral analysis of m-nitromethylbenzoate (MNMB) has been reported in the present work. The FT-IR solid phase (4000-400 cm(-1)) and FT-Raman spectra (3500-100 cm(-1)) of MNMB was recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of MNMB in the ground-state have been calculated by using the density functional method B3LYP with 6-31G (d,p) and 6-31+G(d,p) basis sets. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). Stability of the molecule arising from hyperconjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* antibonding orbitals and E(2) energies confirms the occurrence of ICT (Intra-molecular Charge Transfer) within the molecule. The UV spectrum was measured in ethyl acetate solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) result complements the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Raman spectra and structures of 1-methyl-4-(4-diethylaminophenylazo)-pyridinium iodide in neutral and acidic aqueous solutions

    NASA Astrophysics Data System (ADS)

    Iwase, Akitaka; Ueda, Atsushi; Kuwae, Akio; Hanai, Kazuhiko; Kunimoto, Ko-Ki

    2013-09-01

    Fourier transform (FT) and resonance Raman spectra of 1-methyl-4-(4-diethylaminophenylazo)-pyridinium iodide (MDP) and its four deuterated and three 15N stable isotopic compounds have been measured in neutral and acidic aqueous solutions, and the molecular structures have been discussed on the basis of detailed vibrational assignments using the isotope shifts. No Raman band due to the azo Ndbnd N group is observed in a neutral aqueous solution and also in the solid state of MDP; therefore, this finding suggests that double bond character of the azo group becomes weak and, consequently, the structures of both benzene and pyridinium rings are close to that of a quinoid. The Raman and the 15N NMR spectra indicate that the Nβ of the azo group is protonated in an acidic solution of MDP. Comparison of the spectra of the two solutions suggests that the benzene ring has more quinoid character in the acidic than in the neutral solution. The chromophore structures have been revealed in each of the neutral (purple) and the acidic (yellow) solution.

  7. Resonance Raman and vibronic absorption spectra with Duschinsky rotation from a time-dependent perspective: Application to β-carotene

    NASA Astrophysics Data System (ADS)

    Banerjee, Shiladitya; Kröner, Dominik; Saalfrank, Peter

    2012-12-01

    The time-dependent approach to electronic spectroscopy, as popularized by Heller and co-workers in the 1980s, is applied here in conjunction with linear-response, time-dependent density functional theory to study vibronic absorption and resonance Raman spectra of β-carotene, with and without a solvent. Two-state models, the harmonic and the Condon approximations are used in order to do so. A new code has been developed which includes excited state displacements, vibrational frequency shifts, and Duschinsky rotation, i.e., mode mixing, for both non-adiabatic spectroscopies. It is shown that Duschinsky rotation has a pronounced effect on the resonance Raman spectra of β-carotene. In particular, it can explain a recently found anomalous behaviour of the so-called ν1 peak in resonance Raman spectra [N. Tschirner, M. Schenderlein, K. Brose, E. Schlodder, M. A. Mroginski, C. Thomsen, and P. Hildebrandt, Phys. Chem. Chem. Phys. 11, 11471 (2009)], 10.1039/b917341b, which shifts with the change in excitation wavelength.

  8. Quantum mechanics/molecular mechanics calculation of the Raman spectra of the phycocyanobilin chromophore in alpha-C-phycocyanin.

    PubMed

    Mroginski, Maria Andrea; Mark, Franz; Thiel, Walter; Hildebrandt, Peter

    2007-09-15

    We have established a quantum mechanics (QM)/molecular mechanics (MM) hybrid method for calculating the Raman spectra of protein-bound cofactors using the alpha-subunit of C-phycocyanin containing a phycocyanobilin (PCB) chromophore as a test case. The PCB cofactor was described with density functional theory, whereas the protein matrix was treated with the CHARMM force field. The Hessian matrix of the QM region was built by taking into account bonded and nonbonded interactions with the protein environment and projected onto the internal coordinate space. Force constants were scaled with a global set of scaling factors, and the Raman intensities were computed using a finite-field method combined with a fourth-order differentiation algorithm for the calculation of the polarizability derivatives. In general, the QM/MM results provided a substantially improved description of the experimental resonance Raman (RR) spectra of the protein-bound cofactor compared to QM calculations of isolated PCB models in vacuo. The results allow the assessment of the effect of the protein-cofactor interactions on the RR spectra and reveal the potential and limitations of QM calculations on isolated tetrapyrroles for determining the chromophore structures in the various species and states of phytochromes for which three-dimensional structures are not available.

  9. Glass formation and Raman spectra of CaO-SiO2 glasses towards the orthosilicate limit

    NASA Astrophysics Data System (ADS)

    Retsinas, A.; Kalampounias, A. G.; Papatheodorou, G. N.

    2016-12-01

    A series of silicate glasses formed in the binary system (1-X)CaO-XSiO2with silica mole fractions X ranging from 0.61to 0.38have been prepared using container-less aerodynamic levitation techniques and CO2-laser heating. Glasses with X<0.45were prepared for the first time but, no glass formation was possible at compositions X<0.38. Ambient temperature polarized and depolarized Raman spectra were measured for all these glasses. Qi-speciation analysis of the isotropic Raman spectra shows that near X∼0.38the predominant structures present are the SiO44- tetrahedra and the single bridged Q1species. Oxygen bridging was present at all compositions studied while at X<0.45 small amounts of free oxygen anions was present. The data are compared with the resent NMR measurements obtained with the same glass samples used in the present study. Stokes and anti-Stokes Raman spectra were measured in low frequencies revealing the Boson peak (BP) at ∼50 and ∼70 cm-1 for the corresponding polarized and depolarized configurations. On the Stokes side the BP frequencies exhibit a fictional shift due to contributions from the low frequency vibrational modes of the glass.

  10. Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate ( struvite) and its isomorphous analogues. VII: Spectra of protiated and partially deuterated hexagonal magnesium caesium phosphate hexahydrate

    NASA Astrophysics Data System (ADS)

    Stefov, V.; Cahil, A.; Šoptrajanov, B.; Najdoski, M.; Spirovski, F.; Engelen, B.; Lutz, H. D.; Koleva, V.

    2009-04-01

    The Fourier transform infrared and Raman spectra of the struvite analogue, hexagonal magnesium caesium phosphate hexahydrate, MgCsPO 4·6H 2O ( hP50) and of its partially deuterated analogues were recorded from room temperature (RT) down to the boiling temperature of liquid nitrogen (LNT). The existence of strong hydrogen bonds between water molecules and PO 43- ions is supported by the appearance of a broad band from 3600 to 2200 cm -1 in the O-H stretching region of the vibrational spectra. In the region of the OD stretching vibrations of isotopically isolated HDO molecules of the analogue with a small deuterium content (≈5% D), at least two bands (from the expected three) are observed in the difference LNT infrared spectrum. In the region of ν3(PO 4) modes of the infrared spectra, a broad and asymmetric band (at around 1000 cm -1) is found, while in the region of the ν4(PO 4) bending vibration and of the external modes of the water molecules, several bands can be seen. The intense band at 945 cm -1 in the Raman spectra can with certainty be attributed to the ν1(PO 4) mode. On the basis of a careful analysis of the RT and LNT spectra of the protiated compound, as well as those of its partially deuterated analogues, the asymmetric band at around 550 cm -1 could be assigned to the components of the ν4(PO 4) mode, the bands between 470 and 430 cm -1 to the ν2(PO 4) vibrations and the remaining ones as due to pure or coupled librational and translational modes of the water molecules. The external modes of the phosphate ions and those of the water molecules are mixed.

  11. Far infrared and low frequency gas phase Raman spectra and conformational stability of the 1-halopropanes

    NASA Astrophysics Data System (ADS)

    Durig, J. R.; Godbey, S. E.; Sullivan, J. F.

    1984-06-01

    The far infrared (375-50 cm-1) and low frequency Raman (400-70 cm-1) spectra of the gaseous 1-halopropanes CH3CH2CH2F, CH3CH2CH2Cl, and CH3CH2CH2Br have been recorded and both the methyl and asymmetric torsional modes have been observed and assigned for both the gauche and trans conformers for all of these molecules. The asymmetric torsions for each molecule have several observed excited states which fall on the low frequency side of the fundamental. The asymmetric torsional potential functions have been calculated and, from these potential functions, the enthalpy differences between the high energy trans and low energy gauche conformers have been determined to be 122±10 cm-1 for the fluoride, 127±10 cm-1 for the chloride, and 37±10 cm-1 for the bromide. The trans and gauche methyl torsions have also been observed and assigned for the three 1-halopropanes. The resulting barriers in cm-1 are: 936±4 (trans), 986±9 (gauche) for 1-fluoropropane; 929±2 (trans), 1080±3 (gauche) for 1-chloropropane; and 841 (trans), 1016±8 (gauche) for 1-bromopropane. A complete vibrational assignment has also been made for the 1-fluoropropane molecule and, from the spectral data for the solid, it appears that there are two or more molecules per primitive cell. Attempts to obtain experimental values for the enthalpy differences in the gas phase were made and these results, as well as the determined potential functions, are discussed in relation to previous studies.

  12. Raman spectra and conductivity of PbO-PbCl2-CsCl melts

    NASA Astrophysics Data System (ADS)

    Zakir'yanova, I. D.; Arkhipov, P. A.

    2017-02-01

    The structure and the conductivity of homogeneous CsCl-PbCl2-PbO melts with different compositions are studied. The Raman spectra (RS) of the chloride and oxide-chloride melts containing lead oxide have been measured. It is found that the CsCl (71.3 mol %)-PbCl2 (28.7 mol %) system with the addition of 12 mol % PbO and the CsCl (18.3 mol %)-PbCl2 (81.7 mol %) system with the addition of 18 mol % PbO contain Pb3O2Cl+ oxide-chloride groups. The temperature dependences of the electrical conductivity are measured in the PbCl2-CsCl chloride melts containing 28.7 and 81.7 mol % lead chloride and in homogeneous molten mixtures CsCl (71.3 mol %)-PbCl2 (28.7 mol %) with the addition of 12 mol % PbO and the CsCl (18.3 mol %)-PbCl2 (81.7 mol %) with the addition of 18 mol % PbO. Significant degradation of the ion conductive properties of the PbO-PbCl2-CsCl oxide-chloride melts as compared to those of the PbCl2-CsCl chloride electrolytes has been revealed. It is shown that the decrease in the electrical conductivity of the PbCl2-CsCl oxide-chloride melts as lead oxide is added is due to the presence of Pb3O2Cl+ oxide-chloride groups.

  13. Analysis of torsional spectra of molecules with two internal C3v rotors. II - Far infrared and low frequency Raman spectra of dimethylether isotopes

    NASA Technical Reports Server (NTRS)

    Groner, P.; Durig, J. R.

    1977-01-01

    The torsional far infrared and Raman spectra of gaseous CH3OCH3, CD3OCH3, and CD3OCD3 are presented. They are analyzed using a computer program which is based on the results of an extensive investigation of the isometric groups and of the symmetry groups of the rotation-internal rotation Hamiltonians of a series of semirigid two-top models. Four or more Fourier coefficients of the potential functions in two variables could be determined for each isotope. Strong evidence was found for Fermi-resonance-type interactions with the COC bending mode.

  14. Optical signatures of defects in low temperature Raman and photoluminescence spectra of 2D crystals (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Puretzky, Alexander A.; Mahjouri-Samani, Masoud; Li, Xufan; Xiao, Kai; Wang, Kai; Idrobo, Juan Carlos; Liang, Liangbo; Sumpter, Bobby G.; Yoon, Mina; Meunier, Vincent; Geohegan, David B.

    2017-02-01

    Currently, two-dimensional (2D) layered materials are rapidly emerging as a new platform for many potential applications in nanoscale optoelectronics, optics, flexible electronics, energy, etc. Monolayers of 2D crystals [e.g., transition metals dichalcogenides (TMDs)] are basically surface and therefore, their optoelectronic properties are very sensitive to defects and environment including ambient gases and substrates. However, only limited number of studies is devoted to understanding of the effect of defects on their optical properties. It is not clear if the specific defects have their fingerprints in Raman, absorption, and PL spectra. Here, we report measurements of low temperature (4-150K) Raman and photoluminescence (PL) spectra of TMD monolayers (MoSe2, WS2) with variable and controlled concentrations of specific defects, i.e., chalcogenide atom vacancies, to reveal optical signatures of these defects. The defective TMD monolayers were synthesized using our new laser CVD approach. To identify the type of defects and their concentration the 2D crystals were transferred from a substrate to a TEM grid and atomic resolution STEM and EELS measurements were performed. Low temperature Raman and PL mapping were used to understand spatial distribution of the defects within the 2D crystals. The assignment of the observed spectral features in low temperature Raman and PL spectra was supported by ab initio theoretical modeling. Synthesis science was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division. Characterization and computational science at CNMS was supported by the Scientific User Facilities Division, BES.

  15. The electron–phonon coupling of fundamental, overtone, and combination modes and its effects on the resonance Raman spectra

    SciTech Connect

    Li, Shuo; Li, Zhanlong; Wang, Shenghan; Gao, Shuqin; Sun, Chenglin; Li, Zuowei

    2015-12-15

    Highlights: • The Huang–Rhys factors and electron–phonon coupling constants are calculated. • The changes of overtone mode are larger than those of fundamental mode. • The variation pattern of electron–phonon coupling well interprets the changes of spectra. - Abstract: External field plays a very important role in the interaction between the π-electron transition and atomic vibration of polyenes. It has significant effects on both the Huang–Rhys factor and the electron–phonon coupling. In this paper, the visible absorption and resonance Raman spectra of all-trans-β-carotene are measured in the 345–295 K temperature range and it is found that the changes of the 0–1 and 0–2 vibration bands of the absorption spectra with the temperature lead to the different electron–phonon coupling of fundamental, overtone, and combination modes. The electron-phonon coupling constants of all the modes are calculated and analyzed under different temperatures. The variation law of the electron–phonon coupling with the temperature well interprets the changes of the resonance Raman spectra, such as the shift, intensity and line width of the overtone and combination modes, which are all greater than those of the fundamental modes.

  16. Spectra and structure of organophosphorus compounds. XII - Infrared and Raman spectra of /CH3/2PH and /CD3/2PH

    NASA Technical Reports Server (NTRS)

    Durig, J. R.; Saunders, J. E.

    1975-01-01

    The vibrational spectra of (CH3)2PH and (CD3)2PH have been studied and assignments made. In the infrared, the region between 4000 and 33 wavelength/cm was recorded for the gaseous and solid states, while Raman spectra from 3500 to 10 wavelength/cm in the gaseous, liquid and solid states were observed. There is some evidence of weak hydrogen bonding, based on the behavior of the phosphorus-hydrogen stretching and bending modes. There also appears to be considerable interaction between the methyl rocking and phosphorus-carbon stretching modes. The a double prime and a prime torsional modes appear to be accidentally degenerate at 182 and 142 wavelength/cm for the 'light' and 'heavy' compounds, respectively. This gives barriers of 2.14 and 2.30 kcal/mole, respectively.

  17. Spectra and structure of organophosphorus compounds. XII - Infrared and Raman spectra of /CH3/2PH and /CD3/2PH

    NASA Technical Reports Server (NTRS)

    Durig, J. R.; Saunders, J. E.

    1975-01-01

    The vibrational spectra of (CH3)2PH and (CD3)2PH have been studied and assignments made. In the infrared, the region between 4000 and 33 wavelength/cm was recorded for the gaseous and solid states, while Raman spectra from 3500 to 10 wavelength/cm in the gaseous, liquid and solid states were observed. There is some evidence of weak hydrogen bonding, based on the behavior of the phosphorus-hydrogen stretching and bending modes. There also appears to be considerable interaction between the methyl rocking and phosphorus-carbon stretching modes. The a double prime and a prime torsional modes appear to be accidentally degenerate at 182 and 142 wavelength/cm for the 'light' and 'heavy' compounds, respectively. This gives barriers of 2.14 and 2.30 kcal/mole, respectively.

  18. On the calculations of the vibrational Raman spectra of small water clusters

    NASA Astrophysics Data System (ADS)

    Cybulski, Hubert; Sadlej, Joanna

    2007-12-01

    The static and frequency-dependent Raman intensities for small water clusters ((H 2O) n, n = 2-8) were calculated by means of the DFT(B3LYP)/d-aug-cc-pVDZ method. The obtained intensities were analyzed in order to find a correlation between the topology of a cluster and its calculated Raman spectrum. A change from 170 for water dimer to 677 Å 4 u -1 for hexamer-ring cluster reveals a tendency of a practically linear increase in the Raman intensity of the lowest-frequency symmetric OH stretching mode with a number of water molecules in cyclic clusters (including dimer). The stretching vibrations of the three-coordinated single donor-double acceptor (DAA) molecules are marked by higher Raman intensities than the double donor-single acceptor (DDA) molecules. The simple average Raman intensity over the stretching modes of the DAA molecules yields 110 Å 4 u -1 while the corresponding value for the DDA molecules is 70 Å 4 u -1. The Raman intensities calculated at 351.1 nm are larger by 10-40% than the static ones. Previously suggested in literature origin of the shoulder on the blue side of the Raman spectrum of liquid water as arising from the water molecules whose protons are not engaged to hydrogen bond can be confirmed by our calculations.

  19. Polarized Raman spectra of the oriented NaY(WO 4) 2 and KY(WO 4) 2 single crystals

    NASA Astrophysics Data System (ADS)

    Macalik, L.; Hanuza, J.; Kaminskii, A. A.

    2000-11-01

    Polarized Raman scattering spectra of the NaY(WO 4) 2 (NYW) single crystal have been measured. Its structure is described in the tetragonal space group isomorphic to CaWO 4 scheelite. The A g, B g and E g spectra were made and discussed in terms of factor group analysis. These spectra are compared to those of monoclinic KY(WO 4) 2 (KYW) single crystals whose structure differs from the other crystal. The NYW unit cell comprises of the isolated WO 4 tetrahedra whereas the KYW structure is built from the WO 6 octahedra joined by WO 2W double bonds and WOW single bridges. The vibrational characteristics of the bridge bond systems are proposed. On this basis, the role of the vibronic transitions for the KYW crystal doped with Eu 3+ ions is discussed.

  20. Discriminant analysis of Raman spectra for body fluid identification for forensic purposes.

    PubMed

    Sikirzhytski, Vitali; Virkler, Kelly; Lednev, Igor K

    2010-01-01

    Detection and identification of blood, semen and saliva stains, the most common body fluids encountered at a crime scene, are very important aspects of forensic science today. This study targets the development of a nondestructive, confirmatory method for body fluid identification based on Raman spectroscopy coupled with advanced statistical analysis. Dry traces of blood, semen and saliva obtained from multiple donors were probed using a confocal Raman microscope with a 785-nm excitation wavelength under controlled laboratory conditions. Results demonstrated the capability of Raman spectroscopy to identify an unknown substance to be semen, blood or saliva with high confidence.

  1. A short hydrogen bond investigation by polarized Raman spectra of Co2+ and Zn2+ salts of pyromellitic acid.

    PubMed

    Diniz, Renata; Dantas, Maria S; Fernandes, Nelson G; Sansiviero, Maria T C

    2007-06-01

    Cobalt and zinc salts of 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), [C(6)H(2)(COO)(4)H(4)], have been synthesized and investigate by polarized Raman spectroscopy. These compounds present short intramolecular hydrogen bonds (SHB) between adjacent carboxyl groups. Raman spectra indicate the presence of this interaction in both salts. Three specific vibrational of SHB modes have been investigated: O-H-O symmetric [nu(sym)(OHO)] and asymmetric [nu(asym)(OHO)] stretching modes and O-H stretching mode [nu(O-H)], which they were observed around 300, 850 and 2500 cm(-1), respectively. In crystallographic point of view, the cobalt salt presents a symmetric SHB while the zinc salt presents an asymmetric SHB. In cobalt salt all three vibrational modes of O-H-O groups in polarized Raman spectra occur in A(g) orientation although in zinc salts two of them are observed in A(g) orientation and one in B(g). Spectra analysis indicate that nu(sym)(OHO) mode is observed as A(g) to cobalt salt and B(g) to zinc salt. This mode occurs in a crowded spectral region and its identification was made by deconvolution techniques. Comparing spectra of the two salts, it is observed a small difference in relative intensity and wavenumber shift of nu(sym)(OHO) (deviance of 43 cm(-1)) and nu(OH) (deviance of 21 cm(-1)) modes due probably to differences in O...O distance between salts and in orientation of pyromellitate anion in unit cell. The nu(asym)(OHO) mode does not present significant wavenumber shift due difference in SHB. The nu(OH) band presents a great potential for hydrogen bond studies due to the fact that in its vibrational region (around 2500 cm(-1)) it is not observed other vibrational modes of these compounds.

  2. A short hydrogen bond investigation by polarized Raman spectra of Co 2+ and Zn 2+ salts of pyromellitic acid

    NASA Astrophysics Data System (ADS)

    Diniz, Renata; Dantas, Maria S.; Fernandes, Nelson G.; Sansiviero, Maria T. C.

    2007-06-01

    Cobalt and zinc salts of 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), [C 6H 2(COO) 4H 4], have been synthesized and investigate by polarized Raman spectroscopy. These compounds present short intramolecular hydrogen bonds (SHB) between adjacent carboxyl groups. Raman spectra indicate the presence of this interaction in both salts. Three specific vibrational of SHB modes have been investigated: O-H-O symmetric [ νsym(OHO)] and asymmetric [ νasym(OHO)] stretching modes and O-H stretching mode [ ν(O-H)], which they were observed around 300, 850 and 2500 cm -1, respectively. In crystallographic point of view, the cobalt salt presents a symmetric SHB while the zinc salt presents an asymmetric SHB. In cobalt salt all three vibrational modes of O-H-O groups in polarized Raman spectra occur in A g orientation although in zinc salts two of them are observed in A g orientation and one in B g. Spectra analysis indicate that νsym(OHO) mode is observed as A g to cobalt salt and B g to zinc salt. This mode occurs in a crowed spectral region and its identification was made by deconvolution techniques. Comparing spectra of the two salts, it is observed a small difference in relative intensity and wavenumber shift of νsym(OHO) (deviance of 43 cm -1) and ν(OH) (deviance of 21 cm -1) modes due probably to differences in O⋯O distance between salts and in orientation of pyromellitate anion in unit cell. The νasym(OHO) mode does not present significant wavenumber shift due difference in SHB. The ν(OH) band presents a great potential for hydrogen bond studies due to the fact that in its vibrational region (around 2500 cm -1) it is not observed other vibrational modes of these compounds.

  3. Libraries, classifiers, and quantifiers: a comparison of chemometric methods for the analysis of Raman spectra of contaminated pharmaceutical materials.

    PubMed

    Gryniewicz-Ruzicka, Connie M; Rodriguez, Jason D; Arzhantsev, Sergey; Buhse, Lucinda F; Kauffman, John F

    2012-03-05

    In this study, pharmaceutical grade sorbitol was used as a model system for comparison of Raman based library spectral correlation methods with more sophisticated methods of chemometric data analysis. Both crystallizing sorbitol (CS) and non-crystallizing sorbitol (NCS) from several manufacturers were examined. The Raman spectrum of each sample was collected and identified by correlation with a spectral library that included the CS spectrum but not the NCS spectrum. The average hit quality index (HQI) for the measured NCS spectra and the library CS spectrum was 0.966 whereas the average HQI for the measured CS spectra was 0.991. Both HQIs exceeded the 0.950 threshold that is commonly used for material verification. To enhance the discrimination between CS and NCS, a CS/NCS classification model was constructed using soft independent modeling of class analogies (SIMCA). SIMCA was able to positively identify CS and NCS solutions with no misclassifications. When CS was adulterated with low levels (0-5%) of ethylene glycol (EG) and diethylene glycol (DEG), the HQI values of the measured spectra and the CS library spectrum were still above 0.950. When the CS SIMCA model was applied to adulterated CS spectra, it determined that CS samples with adulterant levels as low as 2% were outside of the CS class. A quantitative PLS model was also applied to EG adulterated CS and resulted in a detection limit of 0.9% for EG. The results obtained from these studies highlight the importance of selecting an appropriate data analysis process for the detection of low level adulterants in pharmaceutical raw materials using Raman spectroscopic screening methods.

  4. [Research on the Method of Eliminating Noise and Background in the Meantime in Detecting Ethanol Contention Based on Raman Spectra].

    PubMed

    Han, Qing-yang; Zhou, Peng-ji

    2015-12-01

    In the process of detecting ethanol content by Raman spectra, the precision of correction model prediction is affected by noise and baseline drift, which is caused by the spectral fluorescence and sample pool's background. Use ensemble empirical mode decomposition to decompose spectrum into several intrinsic mode functions, which are without aliasing. The permutation entropy is employed to judge the intrinsic mode functions. Set the intrinsic mode functions which are on behalf of noise and background to zero, and then the signal is without noise and background. In this paper combine ensemble empirical mode decomposition and permutation entropy, and apply to the Raman spectrum, which are used to detect ethanol content. At the same time compare with wavelet transform and average smoothing filter. The experimental result shows that the application of empirical mode decomposition and permutation entropy can effectively eliminate the noise and background. The precision of correction model prediction is improved. This method simply employs and doesn't need to set parameters, which has great value of application in the process of detecting ethanol content by Raman spectra.

  5. Structural characterization of tellurite glasses doped with transition metal oxides using Raman spectra and ab initio calculations.

    PubMed

    Mohamed, Tarek A; Shaltout, I; Al Yahyaei, K M

    2006-05-01

    Systems of iron tellurite glasses were prepared by melt quenching with compositions of [85%TeO2+5%Fe2O3+10%TMO], where transition metal oxides (TMO) are TiO2, V2O5, MnO, CoO, NiO and CuO. Furthermore, the main structural units of these samples have been characterized by means of Raman spectra (150-1200 cm(-1)) as well as wavenumber predictions by means of Gaussian 98 ab initio calculations for the proposed site symmetries of TeO4(4-) triagonal bipyramid (C2v) and Te2O7(6-) bridged tetrahedra (Cs and C1). Aided by normal coordinate analysis, calculated vibrational frequencies, Raman scattering activities, force constants in internal coordinates and potential energy distributions (PEDs), revised vibrational assignments for the fundamental modes have been proposed. The main structural features are correlated to the dominant units of triagonal bipyramid (tbp) or bridged tetrahedral (TeO3+1 binds to TeO3 through TeOTe bridge; corner sharing). Moreover, the Raman spectra of the investigated tellurites reflect a structural change from tbp (coordination number is four) to triagonal pyramidal (coordination number is three).

  6. [Study of density functional theory (DFT) for Raman spectra of CH3OLi and CH3CH2OLi].

    PubMed

    Yu, Hong-Jing; Liu, Zhao-Jun; Yin, Yan-Feng; Fu, Juan; Ding, Li; Mo, Yu-Jun

    2009-11-01

    Molecular configurations of CH3 OLi and CH3 CH2 OLi were structured based on the previous study that lithium atom and oxygen atom are directly joined by O-Li bond in alkoxy lithium (ROLi). Neither experimental nor theoretical Raman spectra of CH3 OLi and CH3 CH2 OLi have been reported up to now. In the present paper, DFT method at the B3LYP/ 6-31G(d,p) level was used to optimize molecular configurations of CH3 OLi and CH3 CH2 OLi, obtaining each corresponding equilibrium configuration. Vibration frequencies and Raman spectra of these two molecules were calculated based on equilibrium configuration. The vibration frequencies of obtained calculated results were analyzed by normal coordinate analysis. Besides, the Raman vibration modes of CH3 OLi and CH3 CH2 OLi were assigned according to potential energy distribution of each vibration frequency, which will provide theoretical basis for experimental workers to analyze the components of solid electrolyte interface film (SEI film) of lithium ion battery.

  7. Digital dewaxing of Raman signals: discrimination between nevi and melanoma spectra obtained from paraffin-embedded skin biopsies.

    PubMed

    Tfayli, Ali; Gobinet, Cyril; Vrabie, Valeriu; Huez, Regis; Manfait, Michel; Piot, Olivier

    2009-05-01

    Malignant melanoma (MM) is the most severe tumor affecting the skin and accounts for three quarters of all skin cancer deaths. Raman spectroscopy is a promising nondestructive tool that has been increasingly used for characterization of the molecular features of cancerous tissues. Different multivariate statistical analysis techniques are used in order to extract relevant information that can be considered as functional spectroscopic descriptors of a particular pathology. Paraffin embedding (waxing) is a highly efficient process used to conserve biopsies in tumor banks for several years. However, the use of non-dewaxed formalin-fixed paraffin-embedded tissues for Raman spectroscopic investigations remains very restricted, limiting the development of the technique as a routine analytical tool for biomedical purposes. This is due to the highly intense signal of paraffin, which masks important vibrations of the biological tissues. In addition to being time consuming and chemical intensive, chemical dewaxing methods are not efficient and they leave traces of the paraffin in tissues, which affects the Raman signal. In the present study, we use independent component analysis (ICA) on Raman spectral images collected on melanoma and nevus samples. The sources obtained from these images are then used to eliminate, using non-negativity constrained least squares (NCLS), the paraffin contribution from each individual spectrum of the spectral images of nevi and melanomas. Corrected spectra of both types of lesion are then compared and classified into dendrograms using hierarchical cluster analysis (HCA).

  8. Optical redshift in the Raman scattering spectra of Fe-doped multiwalled carbon nanotubes: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Bhalerao, G. M.; Singh, M. K.; Sinha, A. K.; Ghosh, Haranath

    2012-09-01

    Electron doping of arc-grown multiwalled carbon nanotubes coated with iron nanoparticles is established by the redshift of the graphite peak and a larger redshift of the defect peak in the Raman spectra of doped samples compared to the corresponding peak positions in undoped samples. This is unlike the blue Raman shift usually observed in defect-induced double-Raman-resonance studies. On doping, the defect peak splits into two peaks. One has approximately the same dispersion (50 cm-1 eV-1) as the defect peak of undoped samples. The other peak has a very large dispersion (110 cm-1 eV-1). We show that the above observations are consequences of drastic changes in the electronic band structure of the graphitic systems under doping. Experimental observations of the splitting of the defect peak into two and larger dispersions of one of the peaks are explained via double-Raman-resonance processes studied through detailed theoretical calculations of electronic and phonon band structures based on a first principles ab initio method.

  9. Preliminary investigation on the relationship of Raman spectra of sheep meat with shear force and cooking loss.

    PubMed

    Schmidt, Heinar; Scheier, Rico; Hopkins, David L

    2013-01-01

    A prototype handheld Raman system was used as a rapid non-invasive optical device to measure raw sheep meat to estimate cooked meat tenderness and cooking loss. Raman measurements were conducted on m. longissimus thoracis et lumborum samples from two sheep flocks from two different origins which had been aged for five days at 3-4°C before deep freezing and further analysis. The Raman data of 140 samples were correlated with shear force and cooking loss data using PLS regression. Both sample origins could be discriminated and separate correlation models yielded better correlations than the joint correlation model. For shear force, R(2)=0.79 and R(2)=0.86 were obtained for the two sites. Results for cooking loss were comparable: separate models yielded R(2)=0.79 and R(2)=0.83 for the two sites. The results show the potential usefulness of Raman spectra which can be recorded during meat processing for the prediction of quality traits such as tenderness and cooking loss.

  10. FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular conformational analysis of 2,5-di-tert-butyl-hydroquinone

    NASA Astrophysics Data System (ADS)

    Subramanian, N.; Sundaraganesan, N.; Dereli, Ö.; Türkkan, E.

    2011-12-01

    The purpose of finding conformer among six different possible conformers of 2,5-di-tert-butyl-hydroquinone (DTBHQ), its equilibrium geometry and harmonic wavenumbers were calculated by the B3LYP/6-31G(d,p) method. The infrared and Raman spectra of DTBHQ were recorded in the region 400-4000 cm -1 and 50-3500 cm -1, respectively. In addition, the IR spectra in CCl 4 at various concentrations of DTBHQ are also recorded. The computed vibrational wavenumbers were compared with the IR and Raman experimental data. Computational calculations at B3LYP level with two different basis sets 6-31G(d,p) and 6-311++G(d,p) are also employed in the study of the possible conformer of DTBHQ. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated using VEDA 4 program. The general agreement between the observed and calculated frequencies was established.

  11. Communication: three-dimensional model for phonon confinement in small particles: quantitative bandshape analysis of size-dependent Raman spectra of nanodiamonds.

    PubMed

    Korepanov, Vitaly I; Witek, Henryk; Okajima, Hajime; Ōsawa, Eiji; Hamaguchi, Hiro-o

    2014-01-28

    Raman spectroscopy of nano-scale materials is facing a challenge of developing a physically sound quantitative approach for the phonon confinement effect, which profoundly affects the phonon Raman band shapes of small particles. We have developed a new approach based on 3-dimensional phonon dispersion functions. It analyzes the Raman band shapes quantitatively in terms of the particle size distributions. To test the model, we have successfully obtained good fits of the observed phonon Raman spectra of diamond nanoparticles in the size range from 1 to 100 nm.

  12. Surface enhanced raman spectra of biliverdine and pyrromethenone adsorbed to silver colloids

    NASA Astrophysics Data System (ADS)

    Lippitsch, Max E.

    1981-04-01

    Adsorption of certain bile pigments to silver colloids yields an enormous enhancement in Raman intensity, while fluorescence remains more or less unaffected. It is argued that this may be caused by (weak) chemisorption.

  13. Evanescent excitation and collection of spontaneous Raman spectra using silicon nitride nanophotonic waveguides.

    PubMed

    Dhakal, Ashim; Subramanian, Ananth Z; Wuytens, Pieter; Peyskens, Frédéric; Le Thomas, Nicolas; Baets, Roel

    2014-07-01

    We experimentally demonstrate the use of high contrast, CMOS-compatible integrated photonic waveguides for Raman spectroscopy. We also derive the dependence of collected Raman power with the waveguide parameters and experimentally verify the derived relations. Isopropyl alcohol (IPA) is evanescently excited and detected using single-mode silicon-nitride strip waveguides. We analyze the measured signal strength of pure IPA corresponding to an 819  cm⁻¹ Raman peak due to in-phase C-C-O stretch vibration for several waveguide lengths and deduce a pump power to Raman signal conversion efficiency on the waveguide to be at least 10⁻¹¹  per cm.

  14. Ultraviolet Raman spectra and cross-sections of the G-series nerve agents.

    PubMed

    Christesen, Steven D; Pendell Jones, Jay; Lochner, Joseph M; Hyre, Aaron M

    2008-10-01

    Ultraviolet (UV) Raman spectroscopy is being applied to the detection of chemical agent contamination of natural and man-made surfaces. In support of these efforts, we have measured the UV Raman signatures of the G-series nerve agents GA (tabun), GB (sarin), GD (soman), GF (cyclosarin), and the agent simulant diisopropyl methylphosphonate (DIMP) at 248 nm and 262 nm, as well as taking their UV Raman and UV absorption cross-sections. Of these chemicals, only GA exhibits any significant pre-resonance enhancement. We also show that reduction of the excitation wavelength from 262 nm to 248 nm effectively shifts the Raman spectrum away from a substantial sample fluorescence background, implying a significant improvement in detection capability.

  15. Interpretation of FTIR spectra of polymers and Raman spectra of car paints by means of likelihood ratio approach supported by wavelet transform for reducing data dimensionality.

    PubMed

    Martyna, Agnieszka; Michalska, Aleksandra; Zadora, Grzegorz

    2015-05-01

    The problem of interpretation of common provenance of the samples within the infrared spectra database of polypropylene samples from car body parts and plastic containers as well as Raman spectra databases of blue solid and metallic automotive paints was under investigation. The research involved statistical tools such as likelihood ratio (LR) approach for expressing the evidential value of observed similarities and differences in the recorded spectra. Since the LR models can be easily proposed for databases described by a few variables, research focused on the problem of spectra dimensionality reduction characterised by more than a thousand variables. The objective of the studies was to combine the chemometric tools easily dealing with multidimensionality with an LR approach. The final variables used for LR models' construction were derived from the discrete wavelet transform (DWT) as a data dimensionality reduction technique supported by methods for variance analysis and corresponded with chemical information, i.e. typical absorption bands for polypropylene and peaks associated with pigments present in the car paints. Univariate and multivariate LR models were proposed, aiming at obtaining more information about the chemical structure of the samples. Their performance was controlled by estimating the levels of false positive and false negative answers and using the empirical cross entropy approach. The results for most of the LR models were satisfactory and enabled solving the stated comparison problems. The results prove that the variables generated from DWT preserve signal characteristic, being a sparse representation of the original signal by keeping its shape and relevant chemical information.

  16. Conformational properties of asymmetrically substituted mono-, di- and trisulfides: solid and liquid phase Raman spectra

    NASA Astrophysics Data System (ADS)

    Devlin, Mark T.; Barany, George; Levin, Ira W.

    1990-10-01

    The Raman spectra of diallyl trisulfide, allyl methyl sulfide, allyl methyl disulfide and allyl methyl trisulfide in the liquid and solid states are interpreted in terms of their conformational behavior. In both the liquid and solid states, the allyl moieties in all molecules are in a gauche conformation in which the sulfur atoms and the terminal vinyl carbons form a dihedral angle of between 105° and 120°. For diallyl trisulfide and allyl methyl trisulfide in both the liquid and solid states, only a near- cis SS rotational conformer exists with a CSSS dihedral angle of approximately 25°. Furthermore, the rotational isomerism of both SS bonds of these molecules is the same. For allyl methyl disulfide in the solid and liquid phases only the gauche SS conformer exists, with a CSSC dihedral angle of approximately 70°. In the liquid state, two CS rotational conformers occur in each of the four molecules examined. The gauche conformer corresponds to a CCSC (allyl methyl sulfide) or CCSS (allyl methyl disulfide, allyl methyl trisulfide and diallyl trisulfide) dihedral angle of 70°, while the trans conformer corresponds to a CCSC or CCSS dihedral angle of 180°. For allyl methyl sulfide in the solid state only the trans CS conformer exists, while for allyl methyl disulfide and diallyl trisulfide only the gauche CS conformers exist in the solid phase. For allyl methyl trisulfide in the solid state both CS conformers exist, with the gauche CS conformer being more stable. We suggest that the gauche CS conformers for the di- and trisulfide systems are stabilized by attractive 1,4 C··S interactions analogous to those proposed for other sulfur containing molecules (H.E. Van Wart, L.L. Shipman and H.A. Scheraga, J. Phys. Chem., 79 (1975) 1428; ibid., 79 (1975) 1436.)

  17. SIRS-SS: a system for simulating IR/Raman spectra. 2. Procedures and performance.

    PubMed

    Yao, Jianhua; Fan, Botao; Doucet, Jean-Pierre; Panaye, Annick; Li, Jianfeng; Sun, Chuantao; Yuan, Shengang

    2002-01-01

    This paper is devoted to the description of procedures used in our IR/RAMAN spectrum simulation system, based on substructure/subspectrum correlations established between linked databases. The search is performed in the following order: small molecules/specific fragments/atom centered FRELs (FREL: FRagment centered on an Environment which is Limited)/bond focused FRELs. Comparative study with several reported methods has been carried out to show good performance of this software both for IR and RAMAN spectrum simulation.

  18. Raman vibrational spectra of bulk to monolayer ReS2 with lower symmetry

    DOE PAGES

    Feng, Yanqing; Zhou, Wei; Wang, Yaojia; ...

    2015-08-26

    Lattice structure and symmetry of two-dimensional (2D) layered materials are of key importance to their fundamental mechanical, thermal, electronic and optical properties. Raman spectroscopy, as a convenient and nondestructive tool, however has its limitations on identifying all symmetry allowing Raman modes and determining the corresponding crystal structure of 2D layered materials with high symmetry like graphene and MoS2. Due to lower structural symmetry and extraordinary weak interlayer coupling of ReS2, we successfully identified all 18 first-order Raman active modes for bulk and monolayer ReS2. Without van der Waals (vdW) correction, our local density approximation (LDA) calculations successfully reproduce all themore » Raman modes. Our calculations also suggest no surface reconstruction effect and the absence of low frequency rigid-layer Raman modes below 100 cm-1. As a result, combining with Raman and LDA thus provides a general approach for studying the vibrational and structural properties of 2D layered materials with lower symmetry.« less

  19. Multistate Mechanism of Lysozyme Denaturation through Synchronous Analysis of Raman Spectra.

    PubMed

    Xing, Lei; Lin, Ke; Zhou, Xiaoguo; Liu, Shilin; Luo, Yi

    2016-10-10

    The denaturation mechanism of hen egg lysozyme is still controversial. In this study, Raman spectroscopy was employed to study the thermal and chemical denaturation mechanisms of lysozyme. All of the Raman bands were synchronously recorded and analyzed during the denaturation process. It was found that the Raman bands of the side groups changed before the bands of skeleton groups. This directly reveals the three-state mechanism of thermal denaturation of lysozyme. The preferential change of the side groups was also observed in the chemical denaturation of lysozyme by guanidine hydrochloride. Moreover, it was found that the Raman bands of the groups on the surface of lysozyme changed before those of the other groups. This indicates that the chemical denaturants interact with the protein surface before the protein core in each step and the chemical denaturation of lysozyme conforms to the multistate and outside-in mechanisms. The synchronous Raman study not only reveals the multistate mechanism of lysozyme denaturation but also demonstrates that this synchronous Raman analysis is a powerful method to study the denaturation mechanisms of other proteins.

  20. Appearance of radial breathing modes in Raman spectra of multi-walled carbon nanotubes upon laser illumination

    NASA Astrophysics Data System (ADS)

    Rai, Padmnabh; Mohapatra, Dipti R.; Hazra, K. S.; Misra, D. S.; Ghatak, Jay; Satyam, P. V.

    2008-03-01

    The Raman spectra of the multi-walled carbon nanotubes are studied with the laser power of 5-20 mW. We observe the Raman bands at ˜1352, 1581, 1607, and 2700 cm -1 with 5 mW laser power. As the laser power is increased to 10, 15 and 20 mW, the radial breathing modes (RBMs) of the single wall carbon nanotubes (SWNTs) appear in the range 200-610 cm -1. The diameter corresponding to the highest RBM is ˜0.37 nm, the lowest reported so far. The RBMs are attributed to the local synthesis of the SWNTs at the top surface of the samples at higher laser power.

  1. Raman spectra and magnetization of all-ferromagnetic superlattices grown on (110) oriented SrTiO{sub 3}

    SciTech Connect

    Behera, B. C.; Ravindra, A. V.; Padhan, P.; Prellier, W.

    2014-03-03

    Superlattices consist of two ferromagnets La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) and SrRuO{sub 3} (SRO) were grown in (110)-orientation on SrTiO{sub 3} (STO) substrates. The x-ray diffraction and Raman spectra of these superlattices show the presence of in-plane compressive strain and orthorhombic structure of less than 4 u.c. thick LSMO spacer, respectively. Magnetic measurements reveal several features including reduced magnetization, enhanced coercivity, antiferromagnetic coupling, and switching from antiferromagnetic to ferromagnetic coupling with magnetic field orientations. These magnetic properties are explained by the observed orthorhombic structure of spacer LSMO in Raman scattering which occurs due to the modification in the stereochemistry of Mn at the interfaces of SRO and LSMO.

  2. Rare-earth metal halogenide encapsulation-induced modifications in Raman spectra of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kharlamova, M. V.

    2015-01-01

    In the present work, a detailed Raman spectroscopy investigation on the single-walled carbon nanotubes (SWCNTs) filled with praseodymium chloride, terbium chloride and thulium chloride was performed. The salts were incorporated inside the SWCNTs by a capillary filling method using melts, and the high-resolution transmission electron microscopy data proved the high filling degree of the nanotube channels. A thorough analysis of the radial breathing mode and G-band of the Raman spectra of the pristine and filled SWCNTs showed that the encapsulated salts cause acceptor doping of the host nanotubes, and the doping efficiency depends on the compound. The incorporated thulium chloride has the strongest doping effect on the SWCNTs, whereas praseodymium chloride has the weakest effect. It was found that the encapsulated salts modify more significantly the electronic structure of metallic nanotubes than semiconducting SWCNTs.

  3. UV-excited transient raman spectra and the co stretching frequencies of the lowest excited triplet state of benzophenone

    NASA Astrophysics Data System (ADS)

    Tahara, Tahei; Hamaguchi, Hiro-o.; Tasumi, Mitsuo

    1988-11-01

    Transient resonance Raman spectra of T 1 benzophenone (BP) and its carbonyl- 18O-substituted analogue were measured with 355 nm excitation which is in resonance with a triplet-triplet (T n←T 1) transition in the ultraviolet. The intensity of the CO stretch band was greatly enhanced under this resonance condition. Reliable values of the T 1 CO stretching frequency were obtained including the solvent shifts. It is concluded that the solvent dependence of the photochemical reactivity of BP is not primarily due to the solvent-induced structural changes in the T 1 state. The character of the two different T-T transitions (T n←T 1 and T n←T 1) is discussed in relation to the observed Raman spectral changes with different resonance conditions.

  4. NONLINEAR OPTICAL PHENOMENA: Manifestation of a photorefractive effect in Raman spectra of lithium niobate crystals of different compositions

    NASA Astrophysics Data System (ADS)

    Sidorov, N. V.; Chufyrev, P. G.; Palatnikov, M. N.; Mel'nik, N. N.; Zheleznov, Yu A.; Khomich, V. Yu

    2004-12-01

    The ordering of structural units in a cation sublattice and the photorefractive properties of lithium niobate single crystals of different compositions: nominally pure with different [Li]/[Nb] ratios and doped with non-photorefractive cations Mg2+, Gd3+, and Y3+, are studied by their Raman spectra. It is shown that at low concentrations of Mg2+, Gd3+, and Y3+, the magnitude of the photorefractive effect is determined by the ordering of the structural units of the cation sublattice. It is found for the first time that the intensity of a Raman line corresponding to the bridge valence vibrations of oxygen atoms in the NbO6 octahedra is sensitive to the dipole ordering of the cation sublattice.

  5. Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate (struvite) and its isomorphous analogues. V. Spectra of protiated and partially deuterated magnesium ammonium arsenate hexahydrate (arsenstruvite)

    NASA Astrophysics Data System (ADS)

    Stefov, V.; Šoptrajanov, B.; Najdoski, M.; Engelen, B.; Lutz, H. D.

    2008-01-01

    The Fourier transform infrared and Raman spectra of magnesium ammonium arsenate hexahydrate, MgNH 4AsO 4 · 6H 2O (arsenstruvite) and of its deuterated analogues were recorded at room temperature (RT) and the boiling temperature of liquid nitrogen (LNT). Not surprisingly, the spectra show pronounced similarities with the corresponding spectra of the previously studied magnesium potassium phosphate hexahydrate and magnesium ammonium phosphate hexahydrate with the expected differences in the regions of the arsenate vibrations. The main contribution to the intensity of the complex feature in the X-H stretching region (X being O or N) comes from the stretching vibrations of the water molecules, whereas the vibrations of the ammonium ions are less important as long as the intensity is concerned. This is due not only to the fact that four crystallographically different water molecules of crystallization exist in the structure (as compared with a single type of ammonium ions) but also because the hydrogen bonds formed by the water molecules are much stronger than those in which the ammonium ions take part. Difference infrared spectra were obtained by subtracting the properly normalized spectrum of the protiated compound from the spectrum of a deuterated analogue with low deuterium content. As evidenced by the spectra of the partially deuterated analogues and by the difference spectra, vibrational interactions are present in the crystal. Probably the most dramatic is the result of such an interaction producing a deep Evans-type hole in the stretching region of the difference spectrum but additional cases of vibrational mixing are found in the low-frequency region.

  6. Structural, optoelectronic, infrared and Raman spectra of orthorhombic SrSnO{sub 3} from DFT calculations

    SciTech Connect

    Moreira, E.; Henriques, J.M.; Azevedo, D.L.; Caetano, E.W.S.; Freire, V.N.; Albuquerque, E.L.

    2011-04-15

    Orthorhombic SrSnO{sub 3} was investigated using density functional theory (DFT) considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The electronic band structure, density of states, complex dielectric function, optical absorption, and the infrared and Raman spectra were computed. Calculated lattice parameters are close to the experimental measurements, and an indirect band gap E(S{yields}{Gamma})=1.97eV (2.27 eV) was obtained within the GGA (LDA) level of calculation. Effective masses for holes and electrons were estimated, being very anisotropic in comparison with similar results for orthorhombic CaSnO{sub 3}. The complex dielectric function and the optical absorption of SrSnO{sub 3} were shown to be sensitive to the plane of polarization of the incident light. The infrared spectrum between 100 and 600 cm{sup -1} was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum of orthorhombic SrSnO{sub 3} was achieved. -- Graphical abstract: Orthorhombic SrSnO{sub 3}: a view of the unit cell (left) and plots showing the calculated and experimental Raman spectra (right). Display Omitted Research highlights: {yields} We have performed DFT calculations on orthorhombic SrSnO{sub 3} crystals, obtaining their structural, electronical and optical properties. {yields} An indirect band gap was obtained, and anisotropic effective masses were found for both electrons and holes. {yields} The complex dielectric function and the optical absorption of SrSnO{sub 3} were shown to be very sensitive to the plane of polarization of the incident light. {yields} The infrared spectrum between 100 and 600 cm{sup -1} was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum was achieved.

  7. Influence of annealing temperature on Raman and photoluminescence spectra of electron beam evaporated TiO₂ thin films.

    PubMed

    Vishwas, M; Narasimha Rao, K; Chakradhar, R P S

    2012-12-01

    Titanium dioxide (TiO(2)) thin films were deposited on fused quartz substrates by electron beam evaporation method at room temperature. The films were annealed at different temperatures in ambient air. The surface morphology/roughness at different annealing temperatures were analyzed by atomic force microscopy (AFM). The crystallinity of the film has improved with the increase of annealing temperature. The effect of annealing temperature on optical, photoluminescence and Raman spectra of TiO(2) films were investigated. The refractive index of TiO(2) films were studied by envelope method and reflectance spectra and it is observed that the refractive index of the films was high. The photoluminescence intensity corresponding to green emission was enhanced with increase of annealing temperature. The peaks in Raman spectra depicts that the TiO(2) film is of anatase phase after annealing at 300°C and higher. The films show high refractive index, good optical quality and photoluminescence characteristics suggest that possible usage in opto-electronic and optical coating applications.

  8. Structural properties and FTIR-Raman spectra of the anti-hypertensive clonidine hydrochloride agent and their dimeric species

    NASA Astrophysics Data System (ADS)

    Romano, Elida; Davies, Lilian; Brandán, Silvia Antonia

    2017-04-01

    The structural and vibrational properties of the α-adrenergic agonist clonidine hydrochloride agent and their anionic and dimeric species were studied combining the experimental FT-IR and Raman spectra in solid phase with ab-initio calculations based on the density functional theory (DFT). All the calculations were performed by using the hybrid B3LYP with the 6-31G* and 6-311++G** basis sets. The structural properties for those species were studied employing the Natural Bond Orbital (NBO), Atoms in Molecules theory (AIM) and frontier orbitals calculations. The complete assignments of the FTIR and Raman spectra were performed combining the DFT calculations with the Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology. Very good concordances between the theoretical and experimental spectra were found. In addition, the force constants for those three species were computed and compared with the values reported for similar antihypertensive agents. The ionic nature of the H→Cl bond and the high value of the LP(1)N4 → LP*(1)H18 charge transfer could explain the high reactivity of clonidine hydrochloride in relation to other antihypertensive agent and the strong shifthing of the band assigned to the Nsbnd H stretching mode linked to the Hsbnd Cl bond toward lower wavenumbers.

  9. How Does the Relocation of Internal Water Affect Resonance Raman Spectra of Rhodopsin? An Insight from CASSCF/Amber Calculations.

    PubMed

    Andruniów, Tadeusz; Olivucci, Massimo

    2009-11-10

    The effect of relocation of the W2 crystallographic water in bovine rhodopsin has been investigated by comparing and analyzing simulated resonance Raman spectra of 1HZX- and 1U19-based quantum mechanics/molecular mechanics (CASSCF/MM) models. The main target is to explore the sensitivity of the simulated resonance Raman spectra to protein cavity change. In particular, we focus on a quantitative investigation of the changes in the vibrational activity of rhodopsin induced by modifications in the protein cavity structure and in the water position. Comparison of the simulated RR spectra of the Rh-1U19 and Rh-1HZX models with the measured spectrum of rhodopsin reveals that the Rh-1U19 model provides a slightly better rhodopsin model consistently with the simulations of the absorption maxima. On the other hand, and irrespective of the comparison with the experimental data, the analysis of two different computational models for the same protein and chromophore makes it possible to investigate and disentangle the relationship between structural features and change in the RR intensities in an unusually detailed way.

  10. Signal-to-noise contribution of principal component loads in reconstructed near-infrared Raman tissue spectra.

    PubMed

    Grimbergen, M C M; van Swol, C F P; Kendall, C; Verdaasdonk, R M; Stone, N; Bosch, J L H R

    2010-01-01

    The overall quality of Raman spectra in the near-infrared region, where biological samples are often studied, has benefited from various improvements to optical instrumentation over the past decade. However, obtaining ample spectral quality for analysis is still challenging due to device requirements and short integration times required for (in vivo) clinical applications of Raman spectroscopy. Multivariate analytical methods, such as principal component analysis (PCA) and linear discriminant analysis (LDA), are routinely applied to Raman spectral datasets to develop classification models. Data compression is necessary prior to discriminant analysis to prevent or decrease the degree of over-fitting. The logical threshold for the selection of principal components (PCs) to be used in discriminant analysis is likely to be at a point before the PCs begin to introduce equivalent signal and noise and, hence, include no additional value. Assessment of the signal-to-noise ratio (SNR) at a certain peak or over a specific spectral region will depend on the sample measured. Therefore, the mean SNR over the whole spectral region (SNR(msr)) is determined in the original spectrum as well as for spectra reconstructed from an increasing number of principal components. This paper introduces a method of assessing the influence of signal and noise from individual PC loads and indicates a method of selection of PCs for LDA. To evaluate this method, two data sets with different SNRs were used. The sets were obtained with the same Raman system and the same measurement parameters on bladder tissue collected during white light cystoscopy (set A) and fluorescence-guided cystoscopy (set B). This method shows that the mean SNR over the spectral range in the original Raman spectra of these two data sets is related to the signal and noise contribution of principal component loads. The difference in mean SNR over the spectral range can also be appreciated since fewer principal components can

  11. Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate (struvite) and its isomorphous analogues. III. Spectra of protiated and partially deuterated magnesium ammonium phosphate hexahydrate

    NASA Astrophysics Data System (ADS)

    Stefov, V.; Šoptrajanov, B.; Kuzmanovski, I.; Lutz, H. D.; Engelen, B.

    2005-10-01

    Magnesium ammonium phosphate hexahydrate, MgNH 4PO 4·6H 2O (synthetic struvite) is a well-known biomineral, its major biological importance being related to its presence in human urinary sediments and vesical and renal calculi. The Fourier transform infrared and Raman spectra of magnesium ammonium phosphate hexahydrate were recorded and analyzed from room temperature (RT) down to the boiling temperature of liquid nitrogen (LNT). Also recorded and analyzed were the spectra of its partially deuterated analogues. The recorded spectra were compared with the corresponding ones of the previously studied potassium analogue. On the basis of such a comparison it was concluded that the main contribution to the intensity of the broad and structured feature in the O-H/N-H stretching region comes from the bands originating from the H-O-H stretches. The location of at least some of the stretching vibrations of the ammonium ions (albeit one of its deuterated forms) is possible in the spectrum of the sample containing ≈2% deuterium. The bands at 2326 and 2277 cm -1 (and probably, at least partially, that at 2393 cm -1) can be assigned with certainty to N-D stretching vibrations of isotopically isolated NH 3D + ions. The LNT Raman bands at 1702 and 1685 cm -1 are attributed to the ν2NH4+ mode and those at 1477 and 1442 cm -1 are observed are attributed to the ν4 mode. The relatively high frequencies (1302 and 1295 cm -1) of some of the bands due to the ND bending vibrations of isotopically isolated NH 3D + ions are in line with the existence of quite strong hydrogen bonds formed by ammonium ions. The librations of the deuterated forms of water molecules may be coupled with the components of the phosphate ν4 vibration.

  12. Spectra and structure of gallium compounds. Part IX . Infrared and Raman spectra of trimethylphosphinegallium trichloride and normal coordinate calculations of gallium trichloride and the adduct

    NASA Astrophysics Data System (ADS)

    Durig, J. R.; Chatterjee, K. K.

    1982-05-01

    The infrared (3200-50 cm -1)and the Raman (3200-30 cm -1) spectra of (CH 3) 3PGaCI 3 have been recorded for the solid state. The spectra are interpreted on the basis of an effective C3v molecular symmetry for the crystalline state and a complete vibrational assignment except for the torsional modes is presented. The frequencies and potential energy distribution for GaCl 3 and those of the adduct have been calculated utilizing a modified valence force field model. A comparison of the calculated potential constants for the adduct with those of the free Lewis acid and base is made and the differences are shown to be consistent with structural changes upon adduct formation and explained in terms of the VSEPR model. Extensive coupling is observed between the GaP stretching mode and the GaCI 3 and the PC 3 stretching and symmetric deformational modes. Various degrees of coupling are also observed between other skeletal modes of vibration, including coupling between the PC 3 and GaCI 3 rocking motions. The value of 2.01 mdyn Å -1 for the GaP stretching force constant is the same as that previously determined for the same constant for (CH 3) 3PGaH 3. Several weak bands, observed in the low frequency region of the infrared and Raman spectra of crystalline (CH 3) 3PGaCl 3, are characterized as lattice modes arising from intermolecular librations. These results are compared to the similar quantities in some corresponding molecules.

  13. Comparison of several chemometric methods of libraries and classifiers for the analysis of expired drugs based on Raman spectra.

    PubMed

    Gao, Qun; Liu, Yan; Li, Hao; Chen, Hui; Chai, Yifeng; Lu, Feng

    2014-06-01

    Some expired drugs are difficult to detect by conventional means. If they are repackaged and sold back into market, they will constitute a new public health challenge. For the detection of repackaged expired drugs within specification, paracetamol tablet from a manufacturer was used as a model drug in this study for comparison of Raman spectra-based library verification and classification methods. Raman spectra of different batches of paracetamol tablets were collected and a library including standard spectra of unexpired batches of tablets was established. The Raman spectrum of each sample was identified by cosine and correlation with the standard spectrum. The average HQI of the suspicious samples and the standard spectrum were calculated. The optimum threshold values were 0.997 and 0.998 respectively as a result of ROC and four evaluations, for which the accuracy was up to 97%. Three supervised classifiers, PLS-DA, SVM and k-NN, were chosen to establish two-class classification models and compared subsequently. They were used to establish a classification of expired batches and an unexpired batch, and predict the suspect samples. The average accuracy was 90.12%, 96.80% and 89.37% respectively. Different pre-processing techniques were tried to find that first derivative was optimal for methods of libraries and max-min normalization was optimal for that of classifiers. The results obtained from these studies indicated both libraries and classifier methods could detect the expired drugs effectively, and they should be used complementarily in the fast-screening.

  14. Infrared and Polarized Raman Spectra of RbAl(SO 4) 2·12H 2O

    NASA Astrophysics Data System (ADS)

    Suresh, G.; Ratheesh, R.; Jayasree, R. S.; Nayar, V. U.; Keresztury, G.

    1996-03-01

    The IR and polarized Raman spectra of a single crystal RbAl(SO4)2·12H2O is recorded and analyzed at room temperature. Bands indicate a stronger S-O bond in RbAl(SO4)2·12H2O than that in a free SO2-4ion. The fraction of reversed sulfate group in the Rb alum is much lower than that in the potassium alum. Broad bands with frequencies considerably shifted from the free state values indicate that water molecules form hydrogen bonds of various strengths. Two crystallographically distinct water molecules are identified in the crystal.

  15. Surface-Enhanced Raman Scattering Spectra of Thioflavin T: Manifestation of the Electromagnetic and Molecular Enhancement Mechanisms

    NASA Astrophysics Data System (ADS)

    Maskevich, A. A.; Kurhuzenkau, S. A.; Lavysh, A. V.; Kivach, L. N.; Maskevich, S. A.

    2015-09-01

    Surface-enhanced Raman scattering spectra of the fluorescent probe thioflavin T and its complex with amyloid fibrils adsorbed on silver hydrosol were investigated at excitation wavelengths 473, 532, and 633 nm. The enhancement mechanisms of the principal vibrational bands of the dye molecules were determined. The molecules were bound to the surface of the silver nanoparticles through the thiazole ring sulfur atom while retaining their native conformation. Active sites of the molecule that were responsible for its incorporation into amyloid fibrils were identified.

  16. UV and VIS Raman spectra of natural lonsdaleites: towards a recognised standard.

    PubMed

    Smith, David C; Godard, Gaston

    2009-08-01

    A UV laser has now been used to measure the Raman spectrum of lonsdaleite. This mineral species is a little-known hexagonal form of carbon having no known P-T field of stability. Lonsdaleite is known to coexist with diamond and/or graphite in certain impact structures and meteorites. Its presence in microinclusions in some ultrahigh-pressure eclogites is under discussion as there is a considerable wavenumber overlap of the sp(3) Raman band of lonsdaleite in the 1200-1400 cm(-1) region with certain bands of haematite, graphite and diamond, and also with "disordered-diamond" having a downshifted wavenumber. Various incoherent previously published values of the Raman bands are briefly reviewed and an attempt is made to establish a reference spectrum. Four samples of lonsdaleite from the Zapadnaya and Popigai impact structures (Ukraine) were measured with three different laser sources (488, 514.5 and 325 nm) with two Raman spectrometers. UV-Raman was less fluorescent. All the new data were coherent in establishing an sp(3) band centred at 1324+/-4 cm(-1) with a FWHM about five times wider than that of diamond and an intensity about 500 times weaker. The presence of a second band giving a weak shoulder around 1225 cm(-1) is discussed with respect to the alternative of one continuous asymmetrical band.

  17. The effect of pressure on the Raman spectra of solids. VII. The internal Raman bands in solid and coordinated pyridine

    NASA Astrophysics Data System (ADS)

    Heyns, A. M.; Venter, M. W.

    1990-12-01

    The pressure dependences of the internal Raman-active modes of solid pyridine and pyridine-d5 in both the crystalline and glassy modifications as well as of the complexes Zn(py)2Cl2, Ni(py)2Cl2, and Ni(py)4Cl2 are reported. When pyridine is frozen by the application of pressure, some ring modes as well as those involving the hydrogen atoms reflect this transformation. Upon the coordination of pyridine to metal ions, the ring vibrations show appreciable blue shifts. The pressure dependences of ν1, the C-C stretching mode, and ν12, the in-plane ring bending mode of the pyridine rings, are discussed in detail. The unusually high d5-h5 isotopic ratio of ν12 and its contrasting pressure dependences in the liquid and condensed phases of pyridine-d5 are explained. The association of pyridine molecules in the condensed phase does not occur through hydrogen bonds and the C-H stretching modes, in particular, show that repulsive intermolecular forces become very significant at higher pressures. The ratio of the intensities Iν12/Iν1 varies linearly with the strength of the M-N bonds in a series of pyridine complexes and a correlation also exists between Iν12/Iν1 and ∂ν12/∂p. The vibrations ν1 and ν2 are coupled through Fermi resonance in pyridine and its complexes and the pressure dependence of the Fermi resonance constant W is calculated for Zn(py)2Cl2. The C-H stretching modes reflect the presence of more than one distinct pyridine group in the lattice and are of much lower intensity than in complexes where only one distinct pyridine group is found.

  18. Evolution of the Raman spectra from single-, few-, and many-layer graphene with increasing disorder

    SciTech Connect

    Martins Ferreira, E. H.; Stavale, F.; Moutinho, Marcus V. O.; Lucchese, M. M.; Capaz, Rodrigo B.; Achete, C. A.; Jorio, A.

    2010-09-15

    We report on the micro-Raman spectroscopy of monolayer, bilayer, trilayer, and many layers of graphene (graphite) bombarded by low-energy argon ions with different doses. The evolution of peak frequencies, intensities, linewidths, and areas of the main Raman bands of graphene is analyzed as function of the distance between defects and number of layers. We describe the disorder-induced frequency shifts and the increase in the linewidth of the Raman bands by means of a spatial-correlation model. Also, the evolution of the relative areas A{sub D}/A{sub G}, A{sub D}{sup '}/A{sub G}, and A{sub G}{sup '}/A{sub G} is described by a phenomenological model. The present results can be used to fully characterize disorder in graphene systems.

  19. [Application of Raman spectra to the research of jades excavated from Xue Jiagang site].

    PubMed

    Wang, Rong; Feng, Min; Wu, Wei-hong; Gao, Fei; Wang, Chang-sui

    2005-09-01

    Non-destructive analysis is always the aim in jades' research. The present article applied the Raman spectroscopy to the research on jades excavated from the Xue Jiagang site and achieved good result in the main mineral, inclusion and phenocryst. The study shows that as a non-destructive technique Raman spectroscopy can be applied to ancient jades conveniently and practically, and it can detect not only the surface information of ancient jades, but also the interior information. The technique is important to the verification and provenance of ancient jades.

  20. Far-Infrared and Raman Spectra and The Ring-Twisting Potential Energy Function of 1,3-Cyclohexadiene

    NASA Astrophysics Data System (ADS)

    Autrey, Daniel; Choo, Jaebum; Laane, Jaan

    2001-10-01

    The nu19 (A2) ring-twisting vibration of 1,3-cyclohexadiene has been analyzed from the vapor-phase Raman and infrared spectra. The Raman spectrum shows nine ring-twisting transitions in the 116 - 199 cm-1 region. The far-infrared spectrum confirms five of these transitions, despite the fact that the vibration is infrared forbidden in the C2v (planar) approximation. Other Raman and infrared combination bands verify the assignments and provide information on the vibrational coupling. A coordinate dependent kinetic energy expansion for the ring-twisting motion was calculated, and this was used to determine the ring-twisting potential function, which has a barrier to planarity of 1132 cm-1 and energy minima corresponding to twisting angles of 9.1º and 30.1º. Ab initio calculations were also carried out using Moller-Plesset perturbation theory (MP2) with a large number of different basis sets. The various ab initio calculations gave barriers to planarity in the 1197 - 1593 cm-1 range and calculated vibrational frequencies in excellent agreement with the experimental values.

  1. FT-IR and Raman spectra and vibrational investigation of bis (4-acetylanilinium) hexachlorostannate using DFT (B3LYP) calculation

    NASA Astrophysics Data System (ADS)

    Tarchouna, S.; Chaabane, I.; Rahaiem, A. Ben

    2016-09-01

    4-acetylanilinium was used as a ligand for the synthesis of the organic/inorganic compound bis (4-acetylanilinium) hexachlorostannate. Vibrational study in the solid state was performed by FT-Raman of the free 4-acetylanilinium ligand C8H9ON+ and by FT-IR and FT-Raman spectroscopies of the [C8H10NO]2 SnCl6 compound. The comparative analysis of the Raman spectra of the title compound with that of the free ligand was discussed. The structure of the [C8H10NO]2SnCl6 was optimized by density functional theory (DFT) using B3LYP method and shows that the calculated values obtained by B3LYP/LanL2DZ basis are in a better agreement with the experimental data reported by Song et al. (2011) [1] than those obtained by B3LYP/LanL2MB basis. The vibrational frequencies are calculated using density functional theory (DFT) with the B3LYP/LanL2DZ basis, and scaled by various factors. Root mean square (RMS) value was calculated and the small difference between experimental and calculated modes has been interpreted by intermolecular interactions in the crystal.

  2. Progress in the Raman spectra analysis of covalently functionalized multiwalled carbon nanotubes: unraveling disorder in graphitic materials.

    PubMed

    Rebelo, Susana L H; Guedes, Alexandra; Szefczyk, Monika E; Pereira, André M; Araújo, João P; Freire, Cristina

    2016-05-14

    Raman spectroscopy is highly sensitive to the morphology and electronic structures of graphitic materials, but a convenient interpretation model has been lacking for multiwalled carbon nanotubes (MWCNTs), in particular for the discrimination of spectral changes induced by covalent functionalization. The present work describes a systematic investigation of the Raman analysis of covalently functionalized MWCNTs by diazonium chemistry and oxidation methodologies, with typically different mechanisms and reaction sites. A multi-peak deconvolution system and spectral band assignment were proposed based on the chemical and structural modifications identified by X-ray photoelectron spectroscopy, thermogravimetry, X-ray diffraction, specific surface areas and the comparative analysis of the first and second order regions of the Raman spectra. Diazonium functionalization takes place mainly in the π-system of the external sidewall, while oxidation occurs on defects and leads to structure burning. This allowed us to distinguish between spectral features related to aromaticity disruptions within the sidewalls and spectral features related to changes within the inner tubes. The model was validated extending the studies to the functionalization of MWCNTs by the Bingel reaction.

  3. FT-IR and FT-Raman spectra of 2-hydroxyethyl methacrylate--A conformational and vibrational analysis.

    PubMed

    Belaidi, O; Adjim, M; Bouchaour, T; Maschke, U

    2015-09-05

    A conformational search of the flexible 2-hedroxyethyl methacrylate molecule by semi-empirical AM1 and B3LYP formalisms leads to six stable conformations. Four of them are in the s-trans conformation. The optimized geometries at DFT using 6-311+G(∗∗) basis set are in good agreement with experimental electron diffraction data of the methyl methacrylate molecule, thereby the s-trans is the most stable form. The harmonic frequencies at the fully optimized geometries of all conformers have been performed at the DFT//B3LYP/6-311+G(∗∗) level of theory. Infrared and Raman intensities and potential energy distributions of the scaled harmonic frequencies are used for the assignment of the observed IR and Raman bands. We noticed a good agreement between the experimental and the computed spectra. The strong band at 1081 cm(-1), in the infrared spectrum, maybe used as a characteristic band of the s-trans conformation. Henceforth, the less stable structure contribute alone for reproducing the Raman bands located at 276 (sh) and 3020 (vw) cm(-1).

  4. Identification of high-pressure phases III and IV in hydrogen: Simulating Raman spectra using molecular dynamics

    NASA Astrophysics Data System (ADS)

    Magdău, Ioan B.; Ackland, Graeme J.

    2013-05-01

    We present a technique for extracting Raman intensities from ab initio molecular dynamics (MD) simulations at high temperature. The method is applied to the highly anharmonic case of dense hydrogen up to 500 K for pressures ranging from 180 to 300 GPa. On heating or pressurizing we find first-order phase transitions under the experimental conditions of the phase III-IV boundary. At even higher pressures, close to 350 GPa, we find a second phase transformation to the previously proposed Cmca-4. Our method enables, for the first time, a direct comparison of Raman vibrons between theory and experiment at finite temperature. This turns out to provide excellent discrimination between subtly different structures found in MD. We find candidate structures whose Raman spectra are in good agreement with experiment. The new phase obtained in high-temperature simulations adopts a dynamic, simple hexagonal structure with three layer types: freely rotating hydrogen molecules, static hexagonal trimers, and rotating hexagonal trimers. We show that previously calculated structures for phase IV are inconsistent with experiment, and their appearance in simulation is due to finite-size effects.

  5. IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-aminouracil.

    PubMed

    Singh, J S

    2014-09-15

    Infrared (IR) and Raman spectra of uracil and 5-aminouracil have been recorded and analyzed between the region 200-4000 cm(-1). The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Using the Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional and Becke's three-parameter hybrid method (B3LYP), the ab initio and DFT calculations were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-aminouracil by employing Gaussian-03 program. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. In quantum chemical calculations, the most of B3LYP/6-311++G** vibrational frequencies are in the excellent agreement with available experimental assignments and helped in the reassignments of some fundamental vibrational modes. On the basis of calculated results, the assignments of some missing frequencies in the experimental study are proposed. Assuming under the Cs point group for both molecules, the distribution of normal mode of vibrations between the two species as planar (a') and non-planar (a″) are given by 25a'+11a″, of which 30 modes (21a'+9a″) correspond to the uracil moiety and 6 modes (4a'+2a″) to the NH2 group. Kekule ring stretching mode is found to be comparatively higher frequency magnitude than the mode of uracil due to the involvement of hydrogen bonding of amino group. But, the ring breathing is found to be lower frequency magnitude compared to those for uracil which could be due to mass effect of the NH2 group in place of the hydrogen atom. All other bands have also been assigned different fundamentals/overtones/combinations. Copyright © 2014

  6. IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-aminouracil

    NASA Astrophysics Data System (ADS)

    Singh, J. S.

    2014-09-01

    Infrared (IR) and Raman spectra of uracil and 5-aminouracil have been recorded and analyzed between the region 200-4000 cm-1. The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Using the Becke’s exchange in conjunction with Lee-Yang-Parr’s correlation functional and Becke’s three-parameter hybrid method (B3LYP), the ab initio and DFT calculations were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-aminouracil by employing Gaussian-03 program. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. In quantum chemical calculations, the most of B3LYP/6-311++G** vibrational frequencies are in the excellent agreement with available experimental assignments and helped in the reassignments of some fundamental vibrational modes. On the basis of calculated results, the assignments of some missing frequencies in the experimental study are proposed. Assuming under the Cs point group for both molecules, the distribution of normal mode of vibrations between the two species as planar (a‧) and non-planar (a″) are given by 25a‧ + 11a″, of which 30 modes (21a‧ + 9a″) correspond to the uracil moiety and 6 modes (4a‧ + 2a″) to the NH2 group. Kekule ring stretching mode is found to be comparatively higher frequency magnitude than the mode of uracil due to the involvement of hydrogen bonding of amino group. But, the ring breathing is found to be lower frequency magnitude compared to those for uracil which could be due to mass effect of the NH2 group in place of the hydrogen atom. All other bands have also been assigned different fundamentals/overtones/combinations.

  7. Surface-enhanced raman spectra and molecular orientation of phthalazine adsorbed on a silver electrode

    NASA Astrophysics Data System (ADS)

    Takahashi, Machiko; Fujita, Masato; Ito, Masatoki

    1984-08-01

    SERS from phthalazine adsorbed on an Ag electrode was investigated under several conditions of applied voltage and solution concentration. Spectral assignments of the Raman bands were successfully performed and two differently oriented adsorbates, i.e. flat and end-on species, were identified. The contribution of the image field to the SERS intensity was considerable.

  8. Temperature, Magnetic Field, and Dimensionality Effects on the Raman Spectra of TaSe2

    NASA Astrophysics Data System (ADS)

    Simpson, J. R.; Chowdhury, S.; Hight Walker, A. R.

    In bulk form, TaSe2 exhibits transitions between commensurate and incommensurate charge-density wave (CDW) phases, and is attracting interest for advanced device applications. In order to explore the evolution of the groundstate CDW phase with layer number, mechanical exfoliation of bulk crystals provides few- to single-layer flakes. In the present work, we extend our opto-thermal Raman measurements on MoS2 to include other TMDs, specifically TaSe2, in both 1 T and 2 H crystallographic phases. A novel, magneto-Raman microscope system affords measurement of low-frequency (down to 10 cm-1) vibrational modes as a function of both temperature (100 to 400) K and magnetic field (0 to 9) T. The dependence of the observed Raman-active phonons on temperature and magnetic field will be discussed and compared with earlier results on MoS2. Specifically, we observe the appearance of low-frequency, zone-folded modes in the CDW state, which soften with temperature similar to the higher frequency, in-plane E2 g mode. Additionally, we compare the measured magneto-Raman results to calculations using ab initio, density functional theory.

  9. Detection of mercury-TpT dinucleotide binding by Raman spectra: a computational study.

    PubMed

    Benda, Ladislav; Straka, Michal; Sychrovský, Vladimír; Bouř, Petr; Tanaka, Yoshiyuki

    2012-08-16

    The Hg(2+) ion stabilizes the thymine-thymine mismatched base pair and provides new ways of creating various DNA structures. Recently, such T-Hg-T binding was detected by the Raman spectroscopy. In this work, detailed differences in vibrational frequencies and Raman intensity patterns in the free TpT dinucleotide and its metal-mediated complex (TpT·Hg)(2) are interpreted on the basis of quantum chemical modeling. The computations verified specific marker Raman bands indicating the effect of mercury binding to DNA. Although the B3LYP functional well-describes the Raman frequencies, a dispersion correction had to be added for all atoms including mercury to obtain realistic geometry of the (TpT·Hg)(2) dimer. Only then, the DFT complex structure agreed with those obtained with the wave function-based MP2 method. The aqueous solvent modeled as a polarizable continuum had a minor effect on the dispersion interaction, but it stabilized conformations of the sugar and phosphate parts. A generalized definition of internal coordinate force field was introduced to monitor covalent bond mechanical strengthening and weakening upon the Hg(2+) binding. Induced vibrational frequency shifts were rationalized in terms of changes in electronic structure. The simulations thus also provided reliable insight into the complex structure and stability.

  10. A study of the observed shift in the peak position of olivine Raman spectra as a result of shock induced by hypervelocity impacts

    NASA Astrophysics Data System (ADS)

    Harriss, Kathryn H.; Burchell, M. J.

    2016-07-01

    Kuebler et al. (2006) identified variations in olivine Raman spectra based on the composition of individual olivine grains, leading to identification of olivine composition from Raman spectra alone. However, shock on a crystal lattice has since been shown to result in a structural change to the original material, which produces a shift in the Raman spectra of olivine grains compared with the original unshocked olivine (Foster et al. 2013). This suggests that the use of the compositional calculations from the Raman spectra, reported in Kuebler et al. (2006), may provide an incorrect compositional value for material that has experienced shock. Here, we have investigated the effect of impact speed (and hence peak shock pressure) on the shift in the Raman spectra for San Carlos olivine (Fo91) impacting Al foil. Powdered San Carlos olivine (grain size 1-10 μm) was fired at a range of impact speeds from 0.6 to 6.1 km s-1 (peak shock pressures 5-86 GPa) at Al foil to simulate capture over a wide range of peak shock pressures. A permanent change in the Raman spectra was found to be observed only for impact speeds greater than ~5 km s-1. The process that causes the shift is most likely linked to an increase in the peak pressure produced by the impact, but only after a minimum shock pressure associated with the speed at which the effect is first observed (here 65-86 GPa). At speeds around 6 km s-1 (peak shock pressures ~86 GPa), the shift in Raman peak positions is in a similar direction (red shift) to that observed by Foster et al. (2013) but of twice the magnitude.

  11. Spectroscopic and structural studies on lactose species in aqueous solution combining the HATR and Raman spectra with SCRF calculations.

    PubMed

    Márquez, María Jimena; Brizuela, Alicia Beatriz; Davies, Lilian; Brandán, Silvia Antonia

    2015-04-30

    In this work, the α and β isomers, the α-lactose monohydrate and dihydrate and the dimeric species of lactose were studied from the spectroscopic point of view in gas and aqueous solution phases combining the infrared, Horizontal Attenuated Total Reflectance (HATR) and Raman spectra with the density functional theory (DFT) calculations. Aqueous saturated solutions of α-lactose monohydrate and solutions at different molar concentrations of α-lactose monohydrate in water were completely characterized by infrared, HATR and Raman spectroscopies. For all the species in solution, the solvent effects were studied using the solvation polarizable continuum (PCM) and solvation (SM) models and, then, their corresponding solvation energies were predicted. The vibrational spectra of those species in aqueous solution were completely assigned by employing the Scaled Quantum Mechanics Force Field (SQMFF) methodology and the self-consistent reaction field (SCRF) calculations. The stabilities of all those species were studied by using the natural bond orbital (NBO), and atoms in molecules (AIM) calculations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Investigation of oxygen vacancies in Ce coupled TiO2 nanocomposites by Raman and PL spectra

    NASA Astrophysics Data System (ADS)

    Dhanalakshmi, J.; Iyyapushpam, S.; Nishanthi, S. T.; Malligavathy, M.; Pathinettam Padiyan, D.

    2017-03-01

    CeO2–TiO2 nanocomposites with different Ce weight percentages (2, 4, 6 and 8%) were synthesized by sol-gel method. The influence of cerium inclusion on the structural, morphological, optical properties and elemental composition has been analyzed via XRD, BET surface area analysis, UV-DRS, HR-SEM, EDAX, TEM, Raman and photoluminescence spectra. The structural study showed that all the CeO2–TiO2 nanocomposites crystallized in tetragonal structure with anatase phase. Morphological study revealed that the nanocomposites are in spherical shape with size between 13–15 nm. Raman and PL spectra confirmed the presence and influence of oxygen vacancy defects. The adsorption ability of the CeO2–TiO2 nanocomposites was investigated for congo red dye under dark condition. CeO2–TiO2 nanocomposites have enhanced adsorptive performance in comparison with bare TiO2 nanoparticles. The enhanced adsorptive activity of CeO2–TiO2 nanocomposites is due to the higher surface area of the nanocomposites and oxygen vacancies present in the surface of the nanocomposites. The pseudo second order kinetic equation fits well with higher correlation coefficient compared to the pseudo first order in explaining the reaction kinetics.

  13. DFT calculation of the potential energy landscape topology and Raman spectra of type I CH4 and CO2 hydrates.

    PubMed

    Vidal-Vidal, Ángel; Pérez-Rodríguez, Martín; Torré, Jean-Philippe; Piñeiro, Manuel M

    2015-03-14

    CO2 and CH4 clathrate hydrates of type I were studied by means of DFT and QTAIM, in order to better understand their properties at the molecular level. Sub-cells of type I hydrates were modeled as independent rigid cages, both empty and containing guest molecules. Interaction potentials of guest molecules inside each cage, and moving from a cell to the adjacent one, were calculated using the DFT approximation B3LYP/6-311+g(d,p), considering the cases with and without long range Coulombic corrections. The selected theory level was validated by comparison of the simulated Raman spectra with the experimental ones, for the case of type I lattice at full occupation of CO2 and CH4, respectively. For this comparison, Fermi resonances of CO2 were taken into account by transforming experimental bands to the corresponding theoretical non-mixed states. On the one hand, our results confirm the validity of the theory level selected for the model. We have shown the high anisotropy of the guest-cell interaction potential of the molecules analyzed, which has implications in the formulation and use of equations of state, and in the study of transport properties as well. On the other hand, our results suggest that the concentration of guest species inside type I hydrates could be computed from the comparison of experimental and predicted Raman spectra, although there are non-trivial experimental limitations to get over for that purpose.

  14. Molecular structure, vibrational spectra (FTIR and FT Raman) and natural bond orbital analysis of 4-Aminomethylpiperidine: DFT study.

    PubMed

    Mahalakshmi, G; Balachandran, V

    2014-10-15

    The FT-IR and FT-Raman spectra of 4-Aminomethylpiperidine have been recorded using Perkin Elmer Spectrophotometer and Nexus 670 spectrophotometer. The equilibrium geometrical parameters, various bonding features, the vibrational wavenumbers, the infrared intensities and the Raman scattering activities were calculated using Hartree-Fock and density functional method (B3LYP) with 6-311+G(d,p) basis set. Detailed interpretations of the vibrational spectra have been carried out with the aid of the normal coordinate analysis. The spectroscopic and natural bonds orbital (NBO) analysis confirms the occurrence of intra molecular hydrogen bonds, electron delocalization and steric effects. The changes in electron density in the global minimum and in the energy of hyperconjugative interactions of 4-Aminomethylpiperidine (4AMP) were calculated. The theoretical UV-Visible spectrum of the compound was computed in the region 200-400nm by time-dependent TD-DFT approach. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. The dipole moment (μ) and polarizability (α), anisotropy polarizability (Δα) and hyperpolarizability (β) of the molecule have been reported.

  15. Resonance Raman spectra of an O2-binding H-NOX domain reveal heme relaxation upon mutation†

    PubMed Central

    Tran, Rosalie; Boon, Elizabeth M.; Marletta, Michael A.; Mathies, Richard A.

    2009-01-01

    Resonance Raman spectra are measured for Tt H-NOX WT and three other Tt H-NOX proteins containing mutations at key conserved residues to determine the heme conformation in solution. The most dramatic changes in heme conformation occurred in the O2-bound forms, and the single Tt H-NOX P115A mutation was sufficient to generate a significant relaxation of the chromophore. Clear evidence of heme relaxation in the Tt H-NOX I5L, P115A, and I5L/P115A mutants in solution is demonstrated by the observation of reduced resonance Raman intensities for several out-of-plane low frequency modes (e.g. γ11, γ12, γ13, and γ15) in the 400–750 cm−1 region known to be sensitive to ruffling and saddling deformations, as well as increased vibrational frequencies for the core heme skeletal stretching modes, ν3, ν2, and ν10. In addition, all three mutants exhibited some degree of heme conformational heterogeneity based on several broad skeletal markers (e.g. ν10) in the high frequency region. These results are comparable to those observed by Olea et al. for Tt H-NOX P115A in crystal form, where four different heme structures were determined from a single unit cell. Based on the resonance Raman spectra, it is clear that the actual heme conformation for Tt H-NOX P115A in solution is considerably more relaxed than WT, with increased flexibility within the protein pocket, allowing for rapid sampling of alternate conformations. PMID:19653642

  16. The surface-enhanced Raman spectra of aflatoxins: spectral analysis, density functional theory calculation, detection and differentiation.

    PubMed

    Wu, Xiaomeng; Gao, Simin; Wang, Jia-Sheng; Wang, Hongyan; Huang, Yao-Wen; Zhao, Yiping

    2012-09-21

    High-quality surface-enhanced Raman scattering (SERS) spectra of aflatoxin (AF) B(1), B(2), G(1) and G(2) have been acquired using silver nanorod (AgNR) array substrates fabricated by oblique angle deposition method. Significant vibrational peaks are identified on the argon plasma-cleaned substrates, and those peaks agree very well with the Raman spectra calculated by density function theory (DFT). The concentration-dependent SERS detection is also explored. The relationship between the concentration (C) of different AFs and the SERS intensity (I) of the Raman peak at Δν = 1592 cm(-1) is found to follow the general relationship I = AC(α), with α ranging from 0.32 to 0.46 for the four AFs. The limits of detection (LODs) reach 5 × 10(-5) mol L(-1) for AFB(1), 1 × 10(-4) mol L(-1) for AFB(2), and 5 × 10(-6) mol L(-1) for both AFG(1) and AFG(2) in bulk solution, or 6.17 × 10(-16) mol/1.93 × 10(-4) ng of AFB(1), 1.23 × 10(-15) mol/3.88 × 10(-4) ng for AFB(2), 6.17 × 10(-17) mol/2.03 × 10(-5) ng for AFG(1), and 6.17 × 10(-17) mol/2.04 × 10(-5) ng for AFG(2) per laser spot. Principal component analysis (PCA) is used to successfully differentiate these four different kinds of AFs at different concentrations up to their detection limits. The LODs obtained from PCA agree with the LODs obtained by using peak fitting method. With such a low detection limit and outstanding differentiation ability, we prove the possibility of utilizing the SERS detection system as a platform for highly sensitive mycotoxin detection.

  17. Theoretical Study on Surface-Enhanced Raman Spectra of Water Adsorbed on Noble Metal Cathodes of Nanostructures

    NASA Astrophysics Data System (ADS)

    Wu, De-Yin; Pang, Ran; Tian, Zhong-Qun

    2016-06-01

    The observed surface-enhanced Raman scattering (SERS) spectra of water adsorbed on metal film electrodes of silver, gold, and platinum nanoparticles were used to infer interfacial water structures. The basis is the change of the electrochemical vibrational Stark tuning rates and the relative Raman intensity of the stretching and bending modes. How it is not completely understood the reason why the relative Raman intensity ratio of the bending and stretching vibrations of interfacial water increases at the very negative potential region. Density functional theory calculations provide the conceptual model. The specific enhancement effect for the bending mode was closely associated with the water adsorption structure in a hydrogen bonded configuration through its H-end binding to surface sites with large polarizability due to strong cathodic polarization. The present theoretical results allow us to propose that interfacial water molecules exist on these metal cathodes with different hydrogen bonding interactions, the HO-H…Ag(Au) for silver and gold. In acidic solution, a surface electron-hydronium ion-pair was proposed as an adsorption configuration of interfacial water structures on silver and gold cathodes based on density functional theory (DFT) calculations. The EHIP is in the configuration of H3O+(H2O)ne-, where the hydronium H3O+ and the surface electron is separated by water layers. The electron bound in the EHIP can first be excited under light irradiation, subsequently inducing a structural relaxation into a hydrated hydrogen atom. Thus, Raman intensities of the interfacial water in the EHIP species are signifcantly enhanced due to the cathodic polarization on silver and gold electrodes.

  18. Vibrational modes of hydrogens in the proton ordered phase XI of ice: Raman spectra above 400 cm(-1).

    PubMed

    Shigenari, Takeshi; Abe, Kohji

    2012-05-07

    Polarized Raman spectra of the proton ordered phase of ice Ih, i.e., ice XI, were measured above 400 cm(-1) in the range of librational, bending, and stretching vibrations. Vibrational modes in ice XI, of which symmetry is C(2v) (12)(Cmc2(1)), were discussed from the group theoretical point of view. In the librational mode spectra below 1200 cm(-1), several new peaks and clear polarization dependencies were observed. Assignments of the librational modes agree reasonably well with the recent MD calculations by Iwano et al. (J. Phys. Soc. Jpn. 79, 063601 (2010)). In contrast, the spectra for bands above 1200 cm(-1) show no distinct polarization dependencies and the spectra resemble those in ice Ih. In ice XI, however, fine structure composed of several weak peaks appear on the broad bending and the combination band. No direct evidence of the LO-TO splitting of the ν(3) anti-symmetric stretching mode was obtained. It is contrary to the case of the translational modes Abe and Shigenari (J. Chem. Phys. 134, 104506 (2011)). Present results suggest that the influence of the proton ordering in ice XI is weaker than the effect of inter- and intra-molecular couplings in the stretching vibrations of ice Ih.

  19. Independent component analysis-based algorithm for automatic identification of Raman spectra applied to artistic pigments and pigment mixtures.

    PubMed

    González-Vidal, Juan José; Pérez-Pueyo, Rosanna; Soneira, María José; Ruiz-Moreno, Sergio

    2015-03-01

    A new method has been developed to automatically identify Raman spectra, whether they correspond to single- or multicomponent spectra. The method requires no user input or judgment. There are thus no parameters to be tweaked. Furthermore, it provides a reliability factor on the resulting identification, with the aim of becoming a useful support tool for the analyst in the decision-making process. The method relies on the multivariate techniques of principal component analysis (PCA) and independent component analysis (ICA), and on some metrics. It has been developed for the application of automated spectral analysis, where the analyzed spectrum is provided by a spectrometer that has no previous knowledge of the analyzed sample, meaning that the number of components in the sample is unknown. We describe the details of this method and demonstrate its efficiency by identifying both simulated spectra and real spectra. The method has been applied to artistic pigment identification. The reliable and consistent results that were obtained make the methodology a helpful tool suitable for the identification of pigments in artwork or in paint in general.

  20. The Raman spectra and cross-sections of the ν2 band of H 2O, D 2O, and HDO

    NASA Astrophysics Data System (ADS)

    Avila, G.; Tejeda, G.; Fernández, J. M.; Montero, S.

    2004-02-01

    We report the experimental Raman spectra of the ν2 band of H 2O, D 2O, and HDO in the vapor phase at room temperature. A complete interpretation of the Raman intensities is carried out employing the variational rovibrational wavefunctions obtained from a Hamiltonian in Radau coordinates and an ab initio polarizability surface at 514.5 nm. We show the importance of the rotation-vibration coupling to obtain the correct line intensities. Several tables with the assignments of the individual rotational-vibrational transitions and their Raman scattering strengths are reported. From these tables, the ν2 Raman spectra can be simulated up to 2000 K for H 2O, and up to 300 K for D 2O and HDO.

  1. Classification model based on Raman spectra of selected morphological and biochemical tissue constituents for identification of atherosclerosis in human coronary arteries.

    PubMed

    Peres, Marines Bertolo; Silveira, Landulfo; Zângaro, Renato Amaro; Pacheco, Marcos Tadeu Tavares; Pasqualucci, Carlos Augusto

    2011-09-01

    This study presents the results of Raman spectroscopy applied to the classification of arterial tissue based on a simplified model using basal morphological and biochemical information extracted from the Raman spectra of arteries. The Raman spectrograph uses an 830-nm diode laser, imaging spectrograph, and a CCD camera. A total of 111 Raman spectra from arterial fragments were used to develop the model, and those spectra were compared to the spectra of collagen, fat cells, smooth muscle cells, calcification, and cholesterol in a linear fit model. Non-atherosclerotic (NA), fatty and fibrous-fatty atherosclerotic plaques (A) and calcified (C) arteries exhibited different spectral signatures related to different morphological structures presented in each tissue type. Discriminant analysis based on Mahalanobis distance was employed to classify the tissue type with respect to the relative intensity of each compound. This model was subsequently tested prospectively in a set of 55 spectra. The simplified diagnostic model showed that cholesterol, collagen, and adipocytes were the tissue constituents that gave the best classification capability and that those changes were correlated to histopathology. The simplified model, using spectra obtained from a few tissue morphological and biochemical constituents, showed feasibility by using a small amount of variables, easily extracted from gross samples.

  2. Infrared and Raman spectra of DL-aspartic acid nitrate monohydrate

    NASA Astrophysics Data System (ADS)

    Rajkumar, B. J. M.; Ramakrishnan, V.; Rajaram, R. K.

    1998-09-01

    Infrared and Raman spectral studies of DL-aspartic acid nitrate monohydrate help to determine the influence of extensive intermolecular hydrogen bonding in the aspartic acid crystal. The presence of the carbonyl rather than the carboxylic group indicates that the molecule is ionic. The shifting of several group frequencies in the molecule confirms extensive hydrogen bonding. The anion fundamentals however continue to be degenerate. This indicates that its symmetry is unaffected in the molecule.

  3. Raman spectra, electrochemical redox potentials and intramolecular reorganization due to ionization and excitation of benzodifuranone chromophore

    NASA Astrophysics Data System (ADS)

    Luňák, Stanislav; Frumarová, Božena; Mikysek, Tomáš; Vyňuchal, Jan

    2013-05-01

    Experimental Raman spectrum of 3,7-diphenyl substituted benzodifuranone (BDF) was assigned based on the density functional theory. The first electrochemical redox potentials in acetonitrile relate well with DFT adiabatic HOMO and LUMO energies, computed by polarized continuum model including solvent effect. DFT computed changes of bond lengths of central para-benzoquinodimethane (BQM) core upon ionization correspond to the most intense stretching modes. Simple algebraic relations between the bond lengths of BQM core in neutral, ionized and excited species were found.

  4. Influence of the shaking time on the forensic analysis of FTIR and Raman spectra of spray paints.

    PubMed

    Muehlethaler, Cyril; Massonnet, Geneviève; Buzzini, Patrick

    2014-04-01

    In order to decide if replicated measurements of a trace fall within the intra-variability expected for reference paint samples, a forensic scientist has to understand and integrate all reasonable sources of variation. The origins of such variation in spectra can be various, but mainly include differences in components distribution (homogeneity of spraying) or differences originating from the manufacturing process (production batches). Instrumental variation can also be problematic for non-successive measurements. Infrared and Raman spectra were collected to study the homogeneity of the paint distribution after shaking a spray can for times of 0, 1, 2, 3, 4 and 5min. The results confirm that differences arise in both the spectroscopic techniques used in this study. Mainly, this survey shows that the problematic of shaking is particularly important when the pigment content can be detected from spray paint samples within the infrared domain. In these situations, the signal from the pigment might produce strong absorptions that vary with shaking time, leading to differences in relative intensities with respect to those attributed to the binder. For Raman spectroscopy, it has been shown that a gradient of pigment concentration is observable in some samples depending on the shaking time. The proportion of the signal due to the pigment increases with shaking times from 0 to 1min and diminishes afterwards, to finally reach stabilization around 3min of shaking. Not all samples are affected by these differences and it should always be evaluated on a case-by-case basis. From a statistical point-of-view, principal component analyses of the replicates show that the spectra are reproducible after 3min of shaking.

  5. Raman Spectra of Interchanging β lactamase Inhibitor Intermediates on the Millisecond Time Scale

    PubMed Central

    Torkabadi, Hossein Heidari; Che, Tao; Shou, Jingjing; Shanmugam, Sivaprakash; Crowder, Michael W.; Bonomo, Robert A.; Pusztai-Carey, Marianne; Carey, Paul R.

    2013-01-01

    Rapid mix - rapid freeze is a powerful method to study the mechanisms of enzyme-substrate reactions in solution. Here we report a protocol that combines this method with normal (non-resonance) Raman microscopy to enable us to define molecular details of intermediates at early time points. With this combined method, SHV-1, a class A β-lactamase, and tazobactam, a commercially available β-lactamase inhibitor, were rapidly mixed on the millisecond time-scale, then were flash-frozen by injecting into an isopentane solution surrounded by liquid nitrogen. The “ice” was finally freeze-dried and characterized by Raman microscopy. We found that, in solution at 25 milliseconds, the reaction is almost complete giving rise to a major population composed of the trans-enamine intermediate. Between 25 – 500 milliseconds, minor populations of protonated imine are detected, that have previously been postulated to precede enamine intermediates. However, within 1 second, the imines are converted entirely to enamines. Interestingly, with this method, we can measure directly the turnover number of SHV-1 and tazobactam. At 1 : 4 ratio (enzyme : inhibitor) or greater, the enzyme is completely inhibited, a number that agrees with the turnover number derived from steady-state kinetic methods. This application, employing non-intensity enhanced Raman spectroscopy, provides a general and effective route to study the early events in enzyme-substrate reactions. PMID:23406484

  6. Experimental and density functional theory study of Raman and SERS spectra of 5-amino-2-mercaptobenzimidazole

    NASA Astrophysics Data System (ADS)

    Chen, Yufeng; Yang, Jin; Li, Zonglong; Li, Ran; Ruan, Weidong; Zhuang, Zhiping; Zhao, Bing

    2016-01-01

    Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) simulations were employed to study 5-amino-2-mercaptobenzimidazole (5-A-2MBI) molecules. Ag colloids were used as SERS substrates which were prepared by using hydroxylamine hydrochloride as reducing agent. Raman vibration modes and SERS characteristic peaks of 5-A-2MBI were assigned with the aid of DFT calculations. The molecular electrostatic potential (MEP) of 5-A-2MBI was used to discuss the possible adsorption behavior of 5-A-2MBI on Ag colloids. The spectral analysis showed that 5-A-2MBI molecules were slightly titled via the sulfur atoms adhering to the surfaces of Ag substrates. The obtained SERS spectral intensity decreased when lowering the 5-A-2MBI concentrations. A final detection limit on the concentration of 5 × 10- 7 mol · L- 1 was gained. SERS proved to be a simple, fast and reliable method for the detection and characterization of 5-A-2MBI molecules.

  7. Experimental and density functional theory study of Raman and SERS spectra of 5-amino-2-mercaptobenzimidazole.

    PubMed

    Chen, Yufeng; Yang, Jin; Li, Zonglong; Li, Ran; Ruan, Weidong; Zhuang, Zhiping; Zhao, Bing

    2016-01-15

    Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) simulations were employed to study 5-amino-2-mercaptobenzimidazole (5-A-2MBI) molecules. Ag colloids were used as SERS substrates which were prepared by using hydroxylamine hydrochloride as reducing agent. Raman vibration modes and SERS characteristic peaks of 5-A-2MBI were assigned with the aid of DFT calculations. The molecular electrostatic potential (MEP) of 5-A-2MBI was used to discuss the possible adsorption behavior of 5-A-2MBI on Ag colloids. The spectral analysis showed that 5-A-2MBI molecules were slightly titled via the sulfur atoms adhering to the surfaces of Ag substrates. The obtained SERS spectral intensity decreased when lowering the 5-A-2MBI concentrations. A final detection limit on the concentration of 5×10(-7) mol · L(-1) was gained. SERS proved to be a simple, fast and reliable method for the detection and characterization of 5-A-2MBI molecules.

  8. FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular geometry of butylated hydroxy toluene

    NASA Astrophysics Data System (ADS)

    Chinna Babu, P.; Sundaraganesan, N.; Dereli, Ö.; Türkkan, E.

    2011-08-01

    The FT-IR spectrum of 2,6-di-tert-butyl-4-methylphenol [butylated hydroxy toluene] was recorded in the region 4000-400 cm -1. The FT-Raman spectrum of butylated hydroxy toluene was also recorded in the region 3500-50 cm -1. The molecular structure and vibrational frequencies of butylated hydroxy toluene (BHT) have been investigated with combined experimental and theoretical study. Two stable conformers of the title compound were obtained from the result of geometry optimizations of these possible conformers. The conformer 1 is (approximately 2.6 kcal/mol) more stable than conformer 2. Geometry optimizations and vibrational frequency calculations were performed by BLYP and B3LYP methods using 6-31G(d), 6-31G(d,p) and 6-31+G(d,p) as basis sets. The scaled frequencies were compared with experimental spectrum and on the basis of this comparison; assignments of fundamental vibrational modes were examined. Comparison of the experimental spectra with harmonic vibrational wavenumbers indicates that B3LYP/6-31G(d) results are more accurate. Predicted electronic absorption spectra of BHT from TD-DFT calculation have been analyzed and compared with the experimental UV-vis spectrum. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule.

  9. Ab initio calculations of electronic structures, polarizabilities, Raman and infrared spectra, optical gaps, and absorption spectra of M@Si16 (M=Ti and Zr) clusters

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Briere, Tina M.; Kawazoe, Yoshiyuki

    2003-10-01

    Ab initio calculations have been performed using density-functional theory with the B3PW91 hybrid exchange-correlation functional and the Gaussian method to obtain the electronic and vibrational properties of the fullerene (f) and Frank-Kasper (FK) isomers of the metal-encapsulated silicon clusters M@Si16, M=Ti and Zr. The electron affinities of the two isomers are found to differ significantly and our result for FK-Ti@Si16 is in good agreement with recent experiments. The Raman and infrared vibrational spectra of the f and FK isomers show marked differences, due to their distinct bonding natures and structural features, that can be used unambiguously to identify the structures of these clusters experimentally. The polarizabilities, however, have similar values and lie above the bulk limit of silicon. The optical gaps and absorption spectra have been calculated using time-dependent density-functional theory. The lowest electronic excitation for the FK isomer lies in the deep blue region, while the one for the f isomer lies in the red region, making them attractive for optoelectronic applications.

  10. Raman Spectra and Cross Sections of Ammonia, Chlorine, Hydrogen Sulfide, Phosgene, and Sulfur Dioxide Toxic Gases in the Fingerprint Region 400-1400 cm-1

    DTIC Science & Technology

    2016-02-11

    region 400-1400 cm−1 using the Raman cross section of the 1285 cm−1 mode of carbon dioxide (CO2) as the reference.9 Raman cross sections of NH3, Cl2...Safety. Hydrogen sulfide (34 L of 50 ppm balance nitrogen) was purchased from Cross Company. Carbon dioxide (103 L of 4.97 ppm balance air), chlorine...AIP ADVANCES 6, 025310 (2016) Raman spectra and cross sections of ammonia, chlorine, hydrogen sulfide, phosgene, and sulfur dioxide toxic gases in

  11. The effect of laser wavelength on the Raman Spectra of phenanthrene, chrysene, and tetracene: implications for extra-terrestrial detection of polyaromatic hydrocarbons.

    PubMed

    Alajtal, A I; Edwards, H G M; Elbagerma, M A; Scowen, I J

    2010-06-01

    Raman spectroscopy, with visible laser (514 and 633 nm) and near infrared (785 and 1064 nm) excitation, has been used to obtain high quality spectra of phenanthrene, chrysene, and tetracene. Samples with dimensions from a minimum size of 10 microm have been analyzed utilizing a Raman microprobe fitted with a charge-coupled device (CCD) array detector and a FT-Raman instrument. Fluorescence is observed for samples using visible 514, 633 and near infrared 785 nm excitation but most of the samples can be measured with a near infrared 1064 nm Nd:YAG laser. Copyright 2010 Elsevier B.V. All rights reserved.

  12. Spectra and structure of silicon-containing compounds. XXX. Raman and infrared spectra, conformational stability, vibrational assignment of chloromethyl silyl dichloride.

    PubMed

    Guirgis, Gamil A; Pan, Chunhua; Durig, James R

    2002-07-01

    The Raman spectra (3200-30 cm(-1)) of liquid and solid, and infrared spectra of gaseous and solid chloromethyl silyl dichloride, ClCH2SiHCl2, have been recorded. Variable temperature (-105 to -150 degrees C) studies of the infrared spectra of the sample dissolved in liquid krypton have been carried out. From these data, the enthalpy difference was determined to be 363 +/- 40 cm(-1) (4.34 +/- 0.48 kJ mol(-1)), with the more stable form being the gauche conformer, which is consistent with the prediction from ab initio calculations at both the Hartree-Fock level and with full electron correlation by the perturbation method to second order. It is estimated that 92% of the sample is in the gauche form at ambient temperature. A complete vibrational assignment is proposed for the gauche conformer and several of fundamentals of the trans conformer based on infrared band contours, relative intensities, depolarization values, and group frequencies, which is supported by normal coordinate calculations utilizing the force constants from the ab initio MP2/6-31G(d) calculations. The r0 SiH bond distances of 1.476 and 1.472 A have been obtained for the trans and gauche conformers, respectively, from the silicon-hydrogen stretching frequencies. The optimized geometries have also been obtained from ab initio calculations utilizing several different basis sets with full electron correlation by the perturbation method up to MP2/6-311 + G(2d,2p). The results are discussed and compared to some corresponding results for several related molecules.

  13. Ab initio calculations, FTIR and raman spectra of 2,3-difluorobenzonitrile.

    PubMed

    Alcolea Palafox, M; Rastogi, V K; Singh, C; Tanwar, R P

    2001-10-01

    Geometry, vibrational frequencies, atomic charges and several thermodynamic parameters (the total energy, the zero point energy, the rotational constants and the room temperature entropy) were calculated using ab initio quantum chemical methods for 2,3-difluorobenzonitrile molecule. The results were compared with experimental values. With the help of two specific scaling procedures, observed FTIR and Raman vibrational frequencies were analysed and assigned to different normal modes of the molecule. The error obtained was in general very low. Other general conclusions have also been deduced.

  14. FT-IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-methyluracil (thymine).

    PubMed

    Singh, J S

    2015-02-25

    FT-IR (400-4000 cm(-1)) and Raman spectra (200-4000 cm(-1)) of uracil and 5-methyluracil (thymine) have been recorded and analyzed. The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Using the Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional and Becke's three-parameter hybrid method (B3LYP), the ab initio and DFT calculations were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-methyluracil (thymine) by employing Gaussian-03 program. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. In quantum chemical calculations, most of the B3LYP/6-311++G(∗∗) vibrational frequencies are in excellent agreement with the available experimental assignments and helped to propose in the reassignments of some missing frequencies in experimental study. Assuming under the Cs point group for both molecules, the distribution of normal mode of vibrations between the two species as planar (a') and non-planar (a″) for all 39 normal vibrational modes of 5-methyluracil are given by 26a'+13a″, of which 30 modes (21a'+9a″) correspond to the uracil moiety and 9 modes (5a'+4a″) to the CH3 group. Consistent assignments have been made for the internal modes of CH3 group, especially for the anti-symmetric CH3 stretching and bending modes. A possible explanation could be the planarity of pyrimidine ring and non-planarity at carbon site of methyl group which might cause the splitting of frequencies including three components due to the substitution of CH3 group at the site of C5 atom on pyrimidine ring of uracil. The three non-equivalent CH bonds of CH3 group are

  15. FT-IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-methyluracil (thymine)

    NASA Astrophysics Data System (ADS)

    Singh, J. S.

    2015-02-01

    FT-IR (400-4000 cm-1) and Raman spectra (200-4000 cm-1) of uracil and 5-methyluracil (thymine) have been recorded and analyzed. The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Using the Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional and Becke's three-parameter hybrid method (B3LYP), the ab initio and DFT calculations were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-methyluracil (thymine) by employing Gaussian-03 program. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. In quantum chemical calculations, most of the B3LYP/6-311++G∗∗ vibrational frequencies are in excellent agreement with the available experimental assignments and helped to propose in the reassignments of some missing frequencies in experimental study. Assuming under the Cs point group for both molecules, the distribution of normal mode of vibrations between the two species as planar (a‧) and non-planar (a″) for all 39 normal vibrational modes of 5-methyluracil are given by 26a‧ + 13a″, of which 30 modes (21a‧ + 9a″) correspond to the uracil moiety and 9 modes (5a‧ + 4a″) to the CH3 group. Consistent assignments have been made for the internal modes of CH3 group, especially for the anti-symmetric CH3 stretching and bending modes. A possible explanation could be the planarity of pyrimidine ring and non-planarity at carbon site of methyl group which might cause the splitting of frequencies including three components due to the substitution of CH3 group at the site of C5 atom on pyrimidine ring of uracil. The three non-equivalent CH bonds of CH3

  16. Analysis of measured and calculated Raman spectra of indole, 3-methylindole, and tryptophan on the basis of observed and predicted isotope shifts.

    PubMed

    Dieng, Senghane D; Schelvis, Johannes P M

    2010-10-14

    The aromatic amino acid tryptophan plays an important role in protein electron-transfer and in enzyme catalysis. Tryptophan is also used as a probe of its local protein environment and of dynamic changes in this environment. Raman spectroscopy of tryptophan has been an important tool to monitor tryptophan, its radicals, and its protein environment. The proper interpretation of the Raman spectra requires not only the correct assignment of Raman bands to vibrational normal modes but also the correct identification of the Raman bands in the spectrum. A significant amount of experimental and computational work has been devoted to this problem, but inconsistencies still persist. In this work, the Raman spectra of indole, 3-methylindole (3MI), tryptophan, and several of their isotopomers have been measured to determine the isotope shifts of the Raman bands. Density functional theory calculations with the B3LYP functional and the 6-311+G(d,p) basis set have been performed on indole, 3MI, 3-ethylindole (3EI), and several of their isotopomers to predict isotope shifts of the vibrational normal modes. Comparison of the observed and predicted isotope shifts results in a consistent assignment of Raman bands to vibrational normal modes that can be used for both assignment and identification of the Raman bands. For correct assignments, it is important to determine force field scaling factors for each molecule separately, and scaling factors of 0.9824, 0.9843, and 0.9857 are determined for indole, 3MI, and 3EI, respectively. It is also important to use more than one parameter to assign vibrational normal modes to Raman bands, for example, the inclusion of isotope shifts other than those obtained from H/D-exchange. Finally, the results indicate that the Fermi doublet of indole may consist of just two fundamentals, whereas one fundamental and one combination band are identified for the Fermi resonance that gives rise to the doublet in 3MI and tryptophan.

  17. Electronic absorption and resonance Raman spectra of large linear carbon clusters isolated in solid argon.

    PubMed

    Szczepanski, J; Fuller, J; Ekern, S; Vala, M

    2001-03-15

    Neutral and anionic carbon clusters have been generated via a laser-induced graphite-based plasma and deposited in a solid argon matrix. Anionic clusters were formed from neutral clusters by using crossed electron/carbon cluster beams. Thermal annealing (to 36 K) resulted in the aggregation of the smaller carbon species, leading to the formation of long chain neutral and anionic clusters. Spectroscopic measurements in the ultraviolet, visible, near-infrared and infrared regions revealed a series of bands attributable to a homologous set of odd-numbered C5-C29 neutral clusters and even-numbered C6(-)-C36- anionic clusters. Good agreement is found for the band positions of carbon chains containing odd C15-C21 neutrals and even C6(-)-C22- anions, with species previously identified by Maier and coworkers using mass selection or laser vaporization, followed by neon matrix isolation. Resonance Raman frequencies for the neutral C17, C21 and C23 species are shown to be consistent with the above attributions. Density functional theory calculations agree well with the observed bands. It is found that certain low frequency Raman stretching frequencies decrease in a predictable way with increasing chain length. Comparison of the 0(0)0 absorption transitions of the even C18(-)-C36- anionic clusters with the 'unidentified' infrared (UIR) interstellar emission bands suggests that the electronic emission from specific long chain carbon anions may contribute to the some of the UIR bands.

  18. High-pressure Raman study of vibrational spectra in crystalline acetanilide

    NASA Astrophysics Data System (ADS)

    Sakai, Masamichi; Kuroda, Noritaka; Nishina, Yuichiro

    1993-01-01

    We have studied the effect of pressure on the low-frequency lattice modes and the amide-I (N-CO stretching) vibrational modes in crystalline acetanilide (C6H5NHCOCH3) in the temperature range 80-300 K by means of Raman spectroscopy. The Raman intensity of the 1650-cm-1 band, which appears upon cooling, is enhanced by applying pressure. The energy difference between the amide-I phonon (Ag mode) and the 1650-cm-1 bands does not change appreciably under pressure up to at least 4 GPa. These results are analyzed in terms of the self-trapped model in which a single lattice mode couples with the amide-I excitation by taking into account the effect of pressure on the low-frequency lattice modes and on the dipole-dipole interactions associated with the amide-I vibration. A band is observed at 30 cm-1 below the amide-I phonon band at low temperatures with a pressure above ~2 GPa.

  19. Theoretical study, and infrared and Raman spectra of copper(II) chelated complex with dibenzoylmethane.

    PubMed

    Nekoei, A-R; Vakili, M; Hakimi-Tabar, M; Tayyari, S F; Afzali, R; Kjaergaard, H G

    2014-07-15

    There are some discrepancies in both the vibrational assignments and in the metal-ligand (M-L) bond strengths predicted in the previous studies on the copper (II) chelated complex of dibenzoylmethane, Cu(dbm)2. Also, there is a lack of theoretical structure, Raman spectrum and full vibrational assignment for Cu(dbm)2 in the literatures. Density functional theory (DFT) at the B3LYP level and also MP2 calculations using different basis sets, besides Natural Bond Orbital (NBO) and Atoms-in-Molecules (AIM) analyses, have been employed to investigate the effect of methyl substitution with the phenyl group on the stabilities of bis(acetylacetonate) copper (II), Cu(acac)2, and Cu(dbm)2 complexes and the electron delocalization in their chelated rings. Measured solid phase infrared and Raman bands for Cu(dbm)2 complex have been interpreted in terms of the calculated vibrational modes and detailed assignment has been presented. We concluded that, theoretically, the results of charge transfer studies, and experimentally, in-phase symmetric O-Cu-O stretching mode of these complexes are very useful measures for M-L bond strength. The electron delocalization in the chelated rings and the M-L bond strength in Cu(dbm)2 are concluded to be higher than those in Cu(acac)2. The calculated geometries and vibrational results are in good agreement with the experimental data. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Quantitative Determination of Ala-Ala Conformer Ratios in Solution by Decomposition of Raman Optical Activity Spectra.

    PubMed

    Jungwirth, Jakub; Šebestík, Jaroslav; Šafařík, Martin; Kapitán, Josef; Bouř, Petr

    2017-09-18

    Raman optical activity (ROA) spectroscopy combined with quantum-chemical simulations is a sensitive method to determine the absolute configuration and conformation of chiral molecules in solutions. However, the precision of this approach varies for different systems. In the present study, the reliability and numerical stability of decomposing experimental spectra into calculated subspectra is tested on the Ala-Ala dipeptide. Molecular dynamics (MD) snapshots of Ala-Ala/water clusters are averaged to account for solvent effects and molecular flexibility. Multiple experiments with protonated, zwitterionic, and deprotonated dipeptide forms and natural and d2- and d8-isotopically labeled dipeptides are used to verify the results and estimate the overall accuracy. Although the precision is still limited by experimental noise and computational error, a very close match between the observed and theoretical spectral shapes has been achieved. This enabled quantitative determination of conformer populations with a typical dispersion of 10%. The spectroscopy also demonstrated how the conformation depends on pH. The ROA results were more consistent than the Raman ones. Typically, the ROA analysis was more resistant to artifacts in the experiment, such as incomplete baseline subtraction. Conformer ratios predicted by MD agree fairly but not fully with the experimental ones. This indicates minor deficiencies in the Amber force field, particularly for the protonated dipeptide. Overall, the combination of ROA experiment and computational chemistry appears to be a robust tool providing deep insight into molecular structure.

  1. Spectroscopic properties of neuroleptics: IR and Raman spectra of Risperidone (Risperdal) and of its mono- and di-protonated forms

    NASA Astrophysics Data System (ADS)

    Alparone, Andrea

    2011-10-01

    Structures and IR and Raman spectra of Risperidone in its neutral, mono- and di-protonated forms were calculated in gas phase by DFT-B3LYP/6-31G* level. Mono-protonation occurs at the nitrogen atom of the piperidine ring, while nitrogen atom of the pyrimidine ring is the preferred site for the second protonation. The lowest-energy structure of the mono-protonated Risperidone is characterized by formation of a strong seven-membered O(pyrimidine ring)⋯ +H-N(piperidine ring) intramolecular hydrogen-bonded cycle. In the high-energy spectral region (3500-2500 cm -1), the bands of the N-H + stretches and the changes in wavenumbers and IR intensities of the C-H stretches near to the piperidine nitrogen atom (Bohlmann effect) are potentially useful to discriminate conformations and protonation states. Di-protonated structures can be identified by the presence of an isolated absorption peak located in the low-energy IR region (660-690 cm -1), attributed to the out-of-plane N-H +(pyrimidine ring) bending deformation. The most intense Raman band of neutral Risperidone placed at ca. 1500 cm -1, assigned to C dbnd C(pyrimidine ring) stretch + C dbnd N(pyrimidine ring) stretch, can be a useful vibrational marker to distinguish the neutral from the protonated forms.

  2. Synthetic organic pigments of the 20th and 21st century relevant to artist's paints: Raman spectra reference collection

    NASA Astrophysics Data System (ADS)

    Scherrer, Nadim C.; Stefan, Zumbuehl; Francoise, Delavy; Annette, Fritsch; Renate, Kuehnen

    2009-08-01

    Some 170 organic pigments relevant to artist's paints have been collected from historic collections and modern manufacturers. The number includes multiples of the same pigment from different sources and comprises 118 different color indices (C.I.). All of them have been analysed with FTIR spectroscopy and 125 pigments (93 different C.I. No.s) of particular relevance to artist's paints have been characterised with Raman spectroscopy so far. The pigment collection encompasses the following pigment classes and subgroups: monoazo pigments represented by acetoacetic arylide yellow (hansa yellow), β-naphthol, BON, naphthol AS and benzimidazolone; disazo pigments with disazo condensation, diarylide, bisacetoacetarylide, pyrazolone; azo-azomethin metal complex pigments; non-azo, polycyclic pigments such as phthalocyanines, diketopyrrolo-pyrroles (DPP), perylenes and perinones, quinacridones, isoindolinones, polycarbocyclic anthraquinones and dioxanines. The selection of references was based on availability (historic collections) and current use in 16 acrylic, alkyd and oil-based artist's paints, and it covers pigment colors PY yellow (27 C.I. No.s), PR red (38), PO orange (9), PB blue (8), PV violet (6), PG green (3) and PBr brown (2). Besides peak tables and spectra patterns, flow charts based on color, pigment class, group and individual color index are presented to help identification of unknowns and mixed paint samples. While Raman could isolate all different C.I. numbers, multiple references of the same C.I. from different sources could not be distinguished.

  3. Synthetic organic pigments of the 20th and 21st century relevant to artist's paints: Raman spectra reference collection.

    PubMed

    Scherrer, Nadim C; Zumbuehl, Stefan; Delavy, Francoise; Fritsch, Annette; Kuehnen, Renate

    2009-08-01

    Some 170 organic pigments relevant to artist's paints have been collected from historic collections and modern manufacturers. The number includes multiples of the same pigment from different sources and comprises 118 different color indices (C.I.). All of them have been analysed with FTIR spectroscopy and 125 pigments (93 different C.I. No.s) of particular relevance to artist's paints have been characterised with Raman spectroscopy so far. The pigment collection encompasses the following pigment classes and subgroups: monoazo pigments represented by acetoacetic arylide yellow (hansa yellow), beta-naphthol, BON, naphthol AS and benzimidazolone; disazo pigments with disazo condensation, diarylide, bisacetoacetarylide, pyrazolone; azo-azomethin metal complex pigments; non-azo, polycyclic pigments such as phthalocyanines, diketopyrrolo-pyrroles (DPP), perylenes and perinones, quinacridones, isoindolinones, polycarbocyclic anthraquinones and dioxanines. The selection of references was based on availability (historic collections) and current use in 16 acrylic, alkyd and oil-based artist's paints, and it covers pigment colors PY yellow (27 C.I. No.s), PR red (38), PO orange (9), PB blue (8), PV violet (6), PG green (3) and PBr brown (2). Besides peak tables and spectra patterns, flow charts based on color, pigment class, group and individual color index are presented to help identification of unknowns and mixed paint samples. While Raman could isolate all different C.I. numbers, multiple references of the same C.I. from different sources could not be distinguished.

  4. Phase formation, magnetic properties and Raman spectra of Co-Ti co-substitution M-type barium ferrites

    NASA Astrophysics Data System (ADS)

    Li, Jie; Zhang, Huaiwu; Liu, Yinong; Li, Qiang; Zhou, Tingchuan; Yang, Hong

    2015-05-01

    In this paper, Co-Ti ions co-substituted M-type barium ferrite materials [Ba(CoTi)xFe12-2xO19, x = 1.15, 1.20, 1.25 and 1.30] were synthesized by solid-state reaction method. The ferrites, with sintering at 1,200 °C for 4 h, all exhibit the single phase M-type barium ferrite structure. However, there are obvious differences on properties among different amounts of Co-Ti substitution, basing on the same phase formation of M-type barium ferrites. With x increasing from 1.20 to 1.25, magnetic properties, including saturation magnetic flux density ( B s), residual magnetic flux density ( B r), initial permeability ( μ α), saturation magnetization ( M s), coercivity ( H c) and Q-factor, have an obvious change. This is attributing to that Co and Ti occupancies at different sites in the barium ferrite crystalline structure bring the change of magnetocrystalline anisotropy. The appropriate content of Co-Ti substitution makes the magnetocrystalline anisotropy transform from uniaxial to planar anisotropy. Meanwhile, this difference also is confirmed by Raman spectroscopy. The spectra are recorded from 200 to 3,200 cm-1 in the room temperature. The occupancy of Co2+ and Ti4+ ions on the Fe3+ sites causes difference in intensity and Raman bands, which also corroborate the changes of Co-Ti occupation and magnetocrystalline anisotropy from another perspective.

  5. Raman identification of yellow synthetic organic pigments in modern and contemporary paintings: Reference spectra and case studies

    NASA Astrophysics Data System (ADS)

    Ropret, Polonca; Centeno, Silvia A.; Bukovec, Peter

    2008-02-01

    The characterization of the binding media and pigments in modern and contemporary paintings is important for designing safe conservation treatments, as well as for determining suitable environmental conditions for display, storage and transport. Raman spectroscopy is a suitable technique for the in situ non-destructive identification of synthetic organic pigments in the presence of the complex binding media characteristic of synthetic resin paints or colour lithographic inks. The precise identification of a pigment by comparing its spectrum to that of a reference is necessary when conservation treatments with aqueous solutions or organic solvents are being considered for a work of art, since solubility properties can sometimes vary within the same pigment group. The Raman spectra of 21 yellow synthetic organic pigments, belonging to the monoazo, monoazo lakes, diarylide, disazo condensation, benzimidazolone, bisacetoacetarylide, azo-methine metal complex, isoindolinone and isoindoline groups are presented. Since modern artists frequently mixed paint developed for other applications, in addition to colorants developed as artists' paints, other synthetic organic pigments were included in the spectral database. Two monoazo pigments, Pigment Yellow 1 and Pigment Yellow 3, a benzimidazolone, Pigment Yellow 154 and a phthalocynanine, Pigment Green 7, were identified in sample cross-sections from four modern and contemporary paintings in the collection of The Museum of Modern Art in Ljubljana, Slovenia.

  6. Raman identification of yellow synthetic organic pigments in modern and contemporary paintings: reference spectra and case studies.

    PubMed

    Ropret, Polonca; Centeno, Silvia A; Bukovec, Peter

    2008-02-01

    The characterization of the binding media and pigments in modern and contemporary paintings is important for designing safe conservation treatments, as well as for determining suitable environmental conditions for display, storage and transport. Raman spectroscopy is a suitable technique for the in situ non-destructive identification of synthetic organic pigments in the presence of the complex binding media characteristic of synthetic resin paints or colour lithographic inks. The precise identification of a pigment by comparing its spectrum to that of a reference is necessary when conservation treatments with aqueous solutions or organic solvents are being considered for a work of art, since solubility properties can sometimes vary within the same pigment group. The Raman spectra of 21 yellow synthetic organic pigments, belonging to the monoazo, monoazo lakes, diarylide, disazo condensation, benzimidazolone, bisacetoacetarylide, azo-methine metal complex, isoindolinone and isoindoline groups are presented. Since modern artists frequently mixed paint developed for other applications, in addition to colorants developed as artists' paints, other synthetic organic pigments were included in the spectral database. Two monoazo pigments, Pigment Yellow 1 and Pigment Yellow 3, a benzimidazolone, Pigment Yellow 154 and a phthalocynanine, Pigment Green 7, were identified in sample cross-sections from four modern and contemporary paintings in the collection of The Museum of Modern Art in Ljubljana, Slovenia.

  7. Infrared, Raman and NMR spectra, conformational stability and vibrational assignment of 7,8-Dihydroxy-4-Methylcoumarin.

    PubMed

    Erdogdu, Yusuf; Saglam, Semran

    2014-11-11

    We report a combined some (infrared, Raman and NMR) spectroscopic and quantum chemistry study on 7,8-Dihydroxy-4-Methylcoumarin molecule (78D4MC). The Raman and IR spectra of 78D4MC molecule were recorded and analyzed in the region 3500-50 cm(-1) and 4000-400 cm(-1), respectively. Potential energy scans were performed at the MMFF level of theory. All possible conformers, which are results at the MMFF level theory, were re-computed at the B3LYP functional with cc-pVDZ basis set. The optimized geometrical parameters, harmonic vibrational wavenumbers and NMR chemical shifts of the most stable conformer were calculated at the B3LYP/6-311G(d,p), cc-pVTZ and cc-pVQZ level in the proximity of the isolated molecule. DFT calculations were combined with Pulay's scaled quantum mechanics force field (SQMFF) methodology in order to fit the theoretical wavenumbers to the experimental ones.

  8. The 2ν{sub 3} Raman overtone of sulfur hexafluoride: Absolute spectra, pressure effects, and polarizability properties

    SciTech Connect

    Chrysos, M. Rachet, F.; Kremer, D.

    2014-03-28

    Of the six normal vibrations of SF{sub 6}, ν{sub 3} has a key role in the mechanisms of radiative forcing. This vibration, though inactive in Raman, shows up through the transition 2ν{sub 3} allowing for a complementary view on the asymmetric stretch of the molecule. Here, we look back into this topic, which has already caught some interest in the past but with some points been left out. We make a systematic incoherent-light-scattering analysis of the overtone with the use of different gas pressures and polarization orientations for the incident beam. Absolute-scale isotropic and anisotropic spectra are reported along with natural and pressure-induced widths and shifts, and other spectral features such as the peaks corresponding to the (experimentally indistinguishable) interfering channels E{sub g} and F{sub 2g} hitherto seen solely as two-photon IR-absorption features. We make the first-ever prediction of the SF{sub 6} polarizability second derivative with respect to the ν{sub 3}-mode coordinate and we develop a heuristic argument to explain why the superposition of the three degenerate stretching motions that are related to the ν{sub 3} mode cannot but generate a polarized Raman band.

  9. Analysis of serum from type II diabetes mellitus and diabetic complication using surface-enhanced Raman spectra (SERS)

    NASA Astrophysics Data System (ADS)

    Han, H. W.; Yan, X. L.; Dong, R. X.; Ban, G.; Li, K.

    2009-03-01

    In this paper, we show surface-enhanced Raman spectra (SERS) of serums from type II diabetes mellitus and diabetic complication (coronary disease, glaucoma and cerebral infarction), and analyze the SERS through the multivariate statistical methods of principal component analysis (PCA). In particular, we find that there exist many adenines in these serums, which maybe come from DNA (RNA) damage. The relative intensity of the band at 725±2 cm-1 assigned to adenine is higher for patients than for the healthy volunteers; therefore, it can be used as an important ‘fingerprint’ in order to diagnose these diseases. It is also shown that serums from type II diabetes mellitus group, diabetic complication group and healthy volunteers group can be discriminated by PCA.

  10. Effects of Er doping on Raman spectra and on the structural properties of YbMnO{sub 3}

    SciTech Connect

    Sattibabu, Bhumireddi; Bhatnagar, Anil K.

    2015-06-24

    Polycrystalline samples of Yb{sub 1-x}Er{sub x}MnO{sub 3} (x= 0, 0.1 and 0.2) were prepared by a solid state reaction procedure. Detailed crystal structure studies were performed using X-ray diffraction data obtained at room temperature. The application of the Rietveld method confirmed the reported hexagonal P6{sub 3}cm phase. Crystallographic parameters for the pure compounds are in agreement with those found in the literature. Changes in the lattice parameters, unit-cell volume, and polyhedral distortions observed in the compounds are explained as a function of x. Raman spectra show that the phonon peaks of Yb{sub 1-x}Er{sub x}MnO{sub 3} slightly shift to lower frequencies with doping.

  11. Origin of additional broad peaks in Raman spectra from thin germanium-rich silicon-germanium films

    NASA Astrophysics Data System (ADS)

    Takeuchi, Kazuma; Kosemura, Daisuke; Yokogawa, Ryo; Usuda, Koji; Ogura, Atsushi

    2016-07-01

    Additional broad peaks in Raman spectra from thin Ge-rich SiGe films were examined in detail. The broad peak on the low-wavenumber side of first-order optical phonon was also present for pure Ge, which indicates that the localized mode is not the reason for the broad peaks. Furthermore, other factors, e.g., strain, defect, phonon confinement effect, Fano effect, and fluorescence from oil, were excluded from the origin of the broad peaks. We assigned the broad peaks to surface optical phonon modes. The dependence of this surface mode on Ge concentration in Ge-rich SiGe was also investigated and the behavior was discussed.

  12. Sensitive marker bands for the detection of spin states of heme in surface-enhanced resonance Raman scattering spectra of metmyoglobin.

    PubMed

    Kitahama, Yasutaka; Egashira, Masatoshi; Suzuki, Toshiaki; Tanabe, Ichiro; Ozaki, Yukihiro

    2014-12-21

    Surface-enhanced resonance Raman scattering (SERRS) spectra of myoglobin (Mb) with various ligands were measured. In the resonance Raman scattering (RRS) spectra, peaks at around 1610 and 1640 cm(-1) have so far been used to discriminate between the heme iron in a high or low spin state. In the SERRS spectra, however, the spin state cannot be distinguished by the corresponding peaks. Alternatively, the intensity ratio of the SERRS peak at 1560 cm(-1) to that at 1620 cm(-1) was applied to detect the spin states sensitively (1.5 × 10(5) times compared with the RRS); namely, a high ratio was obtained from met-Mb in the high spin state at pH ≤ 7 except for in a strong acid solution. The different marker bands between the SERRS and RRS spectra may be due to the enhancement order from the surface selection rule.

  13. Fully automated decomposition of Raman spectra into individual Pearson's type VII distributions applied to biological and biomedical samples.

    PubMed

    Schulze, H Georg; Atkins, Chad G; Devine, Dana V; Blades, Michael W; Turner, Robin F B

    2015-01-01

    Rapid technological advances have made the acquisition of large numbers of spectra not only feasible, but also routine. As a result, a significant research effort is focused on semi-automated and fully automated spectral processing techniques. However, the need to provide initial estimates of the number of peaks, their band shapes, and the initial parameters of these bands presents an obstacle to the full automation of peak fitting and its incorporation into fully automated spectral-preprocessing workflows. Moreover, the sensitivity of peak-fit routines to initial parameter settings and the resultant variations in solution quality further impede user-free operation. We have developed a technique to perform fully automated peak fitting on fully automated preconditioned spectra-specifically, baseline-corrected and smoothed spectra that are free of cosmic-ray-induced spikes. Briefly, the tallest peak in a spectrum is located and a Gaussian peak-fit is performed. The fitted peak is then subtracted from the spectrum, and the procedure is repeated until the entire spectrum has been processed. In second and third passes, all the peaks in the spectrum are fitted concurrently, but are fitted to a Pearson Type VII model using the parameters for the model established in the prior pass. The technique is applied to a synthetic spectrum with several peaks, some of which have substantial overlap, to test the ability of the method to recover the correct number of peaks, their true shape, and their appropriate parameters. Finally the method is tested on measured Raman spectra collected from human embryonic stem cells and samples of red blood cells.

  14. Raman and infrared spectra of GdTb (MoO 4) 3 single crystal in the region 250-1000 cm -1

    NASA Astrophysics Data System (ADS)

    Saleem, S. Sheik; Aruldhas, G.; Bist, H. D.

    Polarized Raman spectra (single crystal) at 300 K and infrared spectra (powder) at 300 and 85 K in the region 250-1000 cm -1 of a binary molybdate of gadolinium and terbium have been recorded. Based on C 2ν symmetry, group theoretical analysis has been carried out and vibrational assignment is proposed. The observed symmetric stretching frequencies of the MoO 2-4 ion points to the absence of resonance vibrational interaction in this system.

  15. An analytical derivative procedure for the calculation of vibrational Raman optical activity spectra

    NASA Astrophysics Data System (ADS)

    Liégeois, Vincent; Ruud, Kenneth; Champagne, Benoît

    2007-11-01

    We present an analytical time-dependent Hartree-Fock algorithm for the calculation of the derivatives of the electric dipole-magnetic dipole polarizability with respect to atomic Cartesian coordinates. Combined with analogous procedures to determine the derivatives of the electric dipole-electric dipole and electric dipole-electric quadrupole polarizabilities, it enables a fully analytical evaluation of the three frequency-dependent vibrational Raman optical activity (VROA) invariants within the harmonic approximation. The procedure employs traditional non-London atomic orbitals, and the gauge-origin dependence of the VROA intensities has, therefore, been assessed for the commonly used aug-cc-pVDZ and rDPS:3-21G basis sets.

  16. Shaping femtosecond coherent anti-Stokes Raman spectra using optimal control theory.

    PubMed

    Pezeshki, Soroosh; Schreiber, Michael; Kleinekathöfer, Ulrich

    2008-04-21

    Optimal control theory is used to tailor laser pulses which enhance a femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) spectrum in a certain frequency range. For this aim the optimal control theory has to be applied to a target state distributed in time. Explicit control mechanisms are given for shaping either the Stokes or the probe pulse in the four-wave mixing process. A simple molecule for which highly accurate potential energy surfaces are available, namely molecular iodine, is used to test the procedure. This approach of controlling vibrational motion and delivering higher intensities to certain frequency ranges might also be important for the improvement of CARS microscopy.

  17. Double-Ended Calibration of Fiber-Optic Raman Spectra Distributed Temperature Sensing Data

    PubMed Central

    van de Giesen, Nick; Steele-Dunne, Susan C.; Jansen, Jop; Hoes, Olivier; Hausner, Mark B.; Tyler, Scott; Selker, John

    2012-01-01

    Over the past five years, Distributed Temperature Sensing (DTS) along fiber optic cables using Raman backscattering has become an important tool in the environmental sciences. Many environmental applications of DTS demand very accurate temperature measurements, with typical RMSE < 0.1 K. The aim of this paper is to describe and clarify the advantages and disadvantages of double-ended calibration to achieve such accuracy under field conditions. By measuring backscatter from both ends of the fiber optic cable, one can redress the effects of differential attenuation, as caused by bends, splices, and connectors. The methodological principles behind the double-ended calibration are presented, together with a set of practical considerations for field deployment. The results from a field experiment are presented, which show that with double-ended calibration good accuracies can be attained in the field. PMID:22778596

  18. Raman spectra of a Lower Cambrian ctenophore embryo from southwestern Shaanxi, China.

    PubMed

    Chen, Jun-Yuan; Schopf, J William; Bottjer, David J; Zhang, Chen-Yu; Kudryavtsev, Anatoliy B; Tripathi, Abhishek B; Wang, Xiu-Qiang; Yang, Yong-Hua; Gao, Xiang; Yang, Ying

    2007-04-10

    The Early Cambrian (approximately 540 million years old) Meishucun fossil assemblage of Ningqiang County (Shaanxi Province), China, contains the oldest complex skeletonized organisms known in the geological record. We here report the finding in this assemblage of an exquisitely preserved late-stage embryo of a ctenophore ("comb jelly"), its fine structure documented by confocal laser scanning microscopy and shown by Raman spectroscopy to be composed of carbonaceous kerogen permineralized in apatite. In its spheroidal morphology, the presence of eight comb rows and the absence of tentacles, this embryo resembles an adult ctenophore (Maotianoascus octonarius) known from the immediately younger Chengjiang fauna of Yunnan, China. The oldest ctenophore and the only embryonic comb jelly known from the fossil record, this exceptionally well preserved specimen provides important clues about the early evolution of the phylum Ctenophora and of metazoans in general.

  19. Raman spectra of a Lower Cambrian ctenophore embryo from southwestern Shaanxi, China

    PubMed Central

    Chen, Jun-Yuan; Schopf, J. William; Bottjer, David J.; Zhang, Chen-Yu; Kudryavtsev, Anatoliy B.; Tripathi, Abhishek B.; Wang, Xiu-Qiang; Yang, Yong-Hua; Gao, Xiang; Yang, Ying

    2007-01-01

    The Early Cambrian (≈540 million years old) Meishucun fossil assemblage of Ningqiang County (Shaanxi Province), China, contains the oldest complex skeletonized organisms known in the geological record. We here report the finding in this assemblage of an exquisitely preserved late-stage embryo of a ctenophore (“comb jelly”), its fine structure documented by confocal laser scanning microscopy and shown by Raman spectroscopy to be composed of carbonaceous kerogen permineralized in apatite. In its spheroidal morphology, the presence of eight comb rows and the absence of tentacles, this embryo resembles an adult ctenophore (Maotianoascus octonarius) known from the immediately younger Chengjiang fauna of Yunnan, China. The oldest ctenophore and the only embryonic comb jelly known from the fossil record, this exceptionally well preserved specimen provides important clues about the early evolution of the phylum Ctenophora and of metazoans in general. PMID:17404242

  20. High-temperature, high-pressure Raman spectra and their intrinsic anharmonic effects in the perovskite Pb1-xLaxTiO3

    NASA Astrophysics Data System (ADS)

    Joya, Miryam R.; Barba-Ortega, J.; Pizani, P. S.

    2013-01-01

    Raman spectra of ferroelectric Pb1-xLaxTiO3, in the tetragonal phase of the material and for different La concentrations, were studied for different temperatures and pressures. While temperature was varied from 8 K to transition temperature (Tc) at atmospheric pressure, applied hydrostatic pressure was increased from zero to transition pressure (Pc) at room temperature. Isobaric and isothermal mode-Grüneisen parameters were calculated from the measured Raman spectra, and previously reported coefficients of thermal expansion [Chen et al., J. Am. Ceram. Soc. 88, 1356 (2005)] and bulk moduli. Also the coefficient of intrinsic anharmonicity was calculated. Although the absolute value of Grüneisen parameters strongly depends on the Raman mode under study, all of them grow as La concentration increases.

  1. Raman spectra and molecular conformation of 2,4,4-trimethyl-2-pentanethiol as a model compound of a hydrophobic group of triton X-100 surfactant

    NASA Astrophysics Data System (ADS)

    Matsuura, Hiroatsu; Fukuhara, Koichi

    1986-05-01

    Raman spectra of 2,4,4-trimethyl-2-pentanethiol were measured. The spectral analysis with the normal coordinate treatment indicated that this molecule takes the gauche conformation about the CCCS bond in the solid state and the trans and gauche conformations in the liquid state. The Raman bands due to the totally symmetric C&.zdbnd;C streching vibration of the t-butyl part of the 1,1,3,3-tetramethylbutyl group were found to be important to distinguish the two conformations. These key bands were applied to the interpretation of the Raman spectra of Triton X-100 surfactant which contains the p-(1,1,3,3-tetramethylbutyl)phenoxyl group as a hydrophobic moiety. The 1,1,3,3-tetramethylbutyl group of Triton X-100 molecules is shown to be predominantly in the gauche conformation in the liquid state and in aquaeous solution.

  2. Signs of the Biological Effect of ~2 μm Low-Intensity Laser Radiation in Raman and Absorption Spectra of Blood

    NASA Astrophysics Data System (ADS)

    Batay, L. E.; Khodasevich, I. A.; Khodasevich, M. A.; Gorbunova, N. B.; Manina, E. Yu.

    2016-09-01

    Local exposure of experimental animals to low-intensity emission from a thulium laser (λ = 1.96 μm) leads to changes in the Raman and IR absorption spectra of blood. This indicates development of systemic effects caused by direct excitation of water molecules by radiation with wavelength ~2 μm, in particular modifi cation of the hemoglobin molecule.

  3. Quantum chemical calculations and analysis of FTIR, FT-Raman and UV-Vis spectra of temozolomide molecule

    NASA Astrophysics Data System (ADS)

    Bhat, Sheeraz Ahmad; Ahmad, Shabbir

    2015-11-01

    A combined experimental and theoretical study of the structure, vibrational and electronic spectra of temozolomide molecule, which is largely used in the treatment of brain tumours, is presented. FTIR (4000-400 cm-1) and FT-Raman spectra (4000‒50 cm-1) have been recorded and analysed using anharmonic frequency calculations using VPT2, VSCF and CC-VSCF levels of theory within B3LYP/6-311++G(d,p) framework. Anharmonic methods give accurate frequencies of fundamental modes, overtones as well as Fermi resonances and account for coupling of different modes. The anharmonic frequencies calculated using VPT2 and CC-VSCF methods show better agreement with the experimental data. Harmonic frequencies including solvent effects are also computed using IEF-PCM model. The magnitudes of coupling between pair of modes have been calculated using coupling integral based on 2MR-QFF approximation. Intermolecular interactions are discussed for three possible dimers of temozolomide. UV-Vis spectrum, examined in ethanol solvent, is compared with the calculated spectrum at TD-DFT/6-311++G(d,p) level of theory. The electronic properties, such as excitation energy, frontier molecular orbital energies and the assignments of the absorption bands are also discussed.

  4. Furfuryl alcohol—III. Infrared, matrix infrared and Raman spectra and ab initio and normal coordinate calculations

    NASA Astrophysics Data System (ADS)

    Strandman-Long, Liisa; Murto, Juhani

    The i.r. spectra of furfuryl alcohol have been recorded for gaseous and liquid states and in argon and nitrogen matrices, and the i.r. spectrum of the OD deuterated analogue has been recorded in an argon matrix. The Raman spectra of the compounds in the liquid state were also recorded. In particular the modes related to the OH and OD vibrations were studied and the results are discussed. Ab initio STO-3G optimizations were carried out on five conformations of furfuryl alcohol. The rotation of the side group around the CC bond seems to be almost free: an 'orthogonal' conformer being the most stable form. Normal coordinate calculations were carried out on the most stable C s conformer, using the general valence force field, and a vibrational assignment is presented. Force constants taken from the literature were employed for the in-plane vibrations of the furane ring, but for its out-of-plane modes a new force field was developed. This also gave good results for furane.

  5. Resonance Raman Spectra of Cobalt-Substituted Hemoglobin: Cooperativity and Displacement of the Cobalt Atom upon Oxygenation

    PubMed Central

    Woodruff, William H.; Spiro, Thomas G.; Yonetani, Takashi

    1974-01-01

    The resonance Raman spectra of oxy and deoxy cobalt-substituted hemoglobin (CoHb) are reported. Comparison of these spectra to those of hemoglobin, methemoglobin, cytochrome c, and model cobalt porphyrin complexes suggests that the displacement of the cobalt atom upon oxygenation of CoHb is no greater than the out-of-plane distance in five-coordinate Co(II) porphyrins, 0.15 Å. Combining this distance with the expected contraction of the cobalt-histidine bond, Ibers has estimated a maximum displacement of 0.37 Å for the proximal histidine with respect to the heme plane upon oxygenation, about one-third the corresponding distance estimated for iron hemoglobin. The free energy of cooperativity for cobalt hemoglobin is also estimated to be one-third that of iron hemoglobin. These results are therefore consistent with Hopfield's distributed energy model, which predicts proportionality between proximal histidine displacement and the free energy of cooperativity. By implication they support Perutz's trigger mechanism for cooperativity. PMID:4524615

  6. Raman electron spin-lattice relaxation with the Debye-type and with real phonon spectra in crystals

    NASA Astrophysics Data System (ADS)

    Hoffmann, Stanislaw K.; Lijewski, Stefan

    2013-02-01

    Electron spin-lattice relaxation temperature dependence was measured for Ti2+ (S = 1) and for Cu2+ (S = 1/2) ions in SrF2 single crystal by electron spin echo method in temperature range 4-109 K. The spin relaxation was governed by the two-phonon Raman processes. The relaxation theory is outlined and presented in a form suitable for applying with real phonon spectra. The experimental relaxation results were described using Debye-type phonon spectrum and the real phonon spectrum of SrF2 crystal. The Debye approximation does not fit well the results for SrF2 both at low and at high temperature. The relaxation rate is faster than that predicted by Debye-type phonon spectrum at low temperatures where excess of lattice vibrations over the Debye model exists but is slower at higher temperatures (above 50 K) where density of phonon states continuously decreases when approaching to the maximal acoustic phonon frequency. The expected deviation from Debye approximation was analyzed also for Cu2+ in NaCl and MgSiO3 crystals for which phonon spectra are available. The fitting with the real phonon spectrum allowed us to calculate spin-phonon coupling parameter as 267 cm-1 for Ti2+ and 1285 cm-1 for Cu2+ in SrF2.

  7. Organic Process Technology Valuation: Cyclohexanone Oxime Syntheses

    ERIC Educational Resources Information Center

    Cannon, Kevin C.; Breen, Maureen P.

    2010-01-01

    Three contemporary processes for cyclohexanone oxime synthesis are evaluated in a case study. The case study introduces organic chemistry students to basic cost accounting to determine the most economical technology. Technical and financial aspects of these processes are evaluated with problem-based exercises that may be completed by students…

  8. Organic Process Technology Valuation: Cyclohexanone Oxime Syntheses

    ERIC Educational Resources Information Center

    Cannon, Kevin C.; Breen, Maureen P.

    2010-01-01

    Three contemporary processes for cyclohexanone oxime synthesis are evaluated in a case study. The case study introduces organic chemistry students to basic cost accounting to determine the most economical technology. Technical and financial aspects of these processes are evaluated with problem-based exercises that may be completed by students…

  9. Quantum mechanical interpretation of intermolecular vibrational modes of crystalline poly-(R)-3-hydroxybutyrate observed in low-frequency Raman and terahertz spectra.

    PubMed

    Yamamoto, Shigeki; Morisawa, Yusuke; Sato, Harumi; Hoshina, Hiromichi; Ozaki, Yukihiro

    2013-02-21

    Low-frequency vibrational bands observed in the Raman and terahertz (THz) spectra in the region of 50-150 cm(-1) of crystalline powder poly-(R)-3-hydroxybutyrate (PHB) were assigned based on comparisons of the Raman and THz spectra, polarization directions of THz absorption spectra, and their congruities to quantum mechanically (QM) calculated spectra. This combination, Raman and THz spectroscopies and the QM simulations, has been rarely adopted in spite of its potential of reliable assignments of the vibrational bands. The QM simulation of a spectrum has already been popular in vibrational spectroscopies, but for low-frequency bands of polymers it is still a difficult task due to its large scales of systems and a fact that interactions among polymer chains should be considered in the calculation. In this study, the spectral calculations with the aid of the Cartesian-coordinate tensor transfer (CCT) method were applied successfully to the crystalline PHB, which include the explicit consideration of an intermolecular interaction among helical polymer chains. The agreements between the calculations and the experiments are good in both the Raman and THz spectra in terms of spectral shapes, frequencies, and intensities. A Raman active band at 79 cm(-1) was assigned to the intermolecular vibrational mode of the out-of-plane C═O + CH(3) vibration. A polarization state of the corresponding far-infrared absorption band at ∼82 cm(-1), perpendicular to the helix-elongation direction of PHB, was reproduced only under the explicit correction, which indicates that this polarized band originates from the interaction among the polymer chains. The calculation explored that the polarization direction of this band was along the a axis, which is consistent with the direction in which weak intermolecular hydrogen bonds are suggested between the C═O and CH(3) groups of two parallel polymer chains. The results obtained here have confirmed sensitivity of the low

  10. Infrared and Raman spectra, conformational stability, vibration assignment, and ab initio calculations for 3-bromo-3,3-difluoropropene

    NASA Astrophysics Data System (ADS)

    Shen, Shiyu; Guirgis, Gamil A.; Gao, Jian; Durig, James R.

    2001-12-01

    The infrared spectra (3200-50 cm -1) of gaseous and solid and Raman spectra (3200-10 cm -1) of the liquid with qualitative depolarization ratios and solid 3-bromo-3,3-difluoropropene CH 2CHCBrF 2 have been recorded. Both the gauche and cis conformers have been identified in the fluid phase, but the gauche conformer is thermodynamically more stable than the cis rotamer and it is the only rotamer present in the spectrum of the annealed solid. Variable temperature (-105 to -150°C) studies of the infrared spectra of the sample dissolved in liquid krypton has been carried out. From these data, the enthalpy difference has been determined to be 281±28 cm -1 (3.36±0.33 kJ mol -1), with the gauche conformer as the more stable rotamer, which is in agreement with the ab initio predictions at all levels of calculations. It is estimated that there is only 11% of the cis conformer present at an ambient temperature. A complete vibration assignment is proposed for the gauche conformer which is based on infrared band contours, depolarization values, and group frequencies which is supported by normal coordinate calculations utilizing the force constants from ab initio MP2/6-31G (d) calculations. The conformational stabilities, barriers to internal rotation, and fundamental vibrational frequencies which have been determined experimentally are compared to those obtained from the ab initio calculations. The results are discussed and compared with the corresponding properties of some similar molecules.

  11. FTIR, FT-Raman, UV-Visible spectra and quantum chemical calculations of allantoin molecule and its hydrogen bonded dimers.

    PubMed

    Alam, Mohammad Jane; Ahmad, Shabbir

    2015-02-05

    FTIR, FT-Raman and electronic spectra of allantoin molecule are recorded and investigated using DFT and MP2 methods with 6-311++G(d,p) basis set. The molecular structure, anharmonic vibrational spectra, natural atomic charges, non-linear optical properties, etc. have been computed for the ground state of allantoin. The anharmonic vibrational frequencies are calculated using PT2 algorithm (Barone method) as well as VSCF and CC-VSCF methods. These methods yield results that are in remarkable agreement with the experiment. The coupling strengths between pairs of modes are also calculated using coupling integral based on 2MR-QFF approximation. The simulations on allantoin dimers have been also performed at B3LYP/6-311++G(d,p) level of theory to investigate the effect of the intermolecular interactions on the molecular structure and vibrational frequencies of the monomer. Vibrational assignments are made with the great accuracy using PED calculations and animated modes. The combination and overtone bands have been also identified in the FTIR spectrum with the help of anharmonic computations. The electronic spectra are simulated in gas and solution at TD-B3LYP/6-311++G(d,p) level of theory. The important global quantities such as electro-negativity, electronic chemical potential, electrophilicity index, chemical hardness and softness based on HOMO, LUMO energy eigenvalues are also computed. NBO analysis has been performed for monomer and dimers of allantoin at B3LYP/6-311++G(d,p) level of theory. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. FT-IR and FT-Raman spectra, normal coordinate analysis and ab initio computations of Trimesic acid.

    PubMed

    Mahalakshmi, G; Balachandran, V

    2014-04-24

    The FT-IR and FT-Raman spectra have been recorded of Trimesic acid (1,3,5-benzenetricarboxylic acid, H3BTC). The molecular structure, conformational stability, geometry optimization, vibrational frequencies have been investigated. The total energy calculations of H3BTC were tried for various possible conformers. The spectra were interpreted with the aid of normal coordinate analysis based on ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods and 6-31+G(d,p) basis set level and was scaled using scale factors yielding good agreement between observed and calculated frequencies. Vibrational assignments and Natural bonding orbital (NBO) calculations are performed on the stable monomer of H3BTC using the same level of theory. Intramolecular hydrogen bond exists via COOH group gives the evidence for the formation of dimer entities in the title molecule. UV-VIS spectral analyses of H3BTC have been researched by theoretical calculations. In order to understand electronic transitions of the compound, TD-DFT calculations on electronic absorption spectra in gas phase and solvent (DMSO and Chloroform) were performed. The calculated frontier orbital energies, absorption wavelengths (λ), oscillator strengths (ƒ) and excitation energies (E) for gas phase and solvent (DMSO and Chloroform) are also illustrated. The statistical thermodynamic functions were obtained for the range of temperature 100-1000 K. Reliable vibrational modes associated with H3BTC are made on the basis of total energy distribution (TED) results obtained from scaled quantum mechanical (SQM) method.

  13. Chemometric study of Andalusian extra virgin olive oils Raman spectra: Qualitative and quantitative information.

    PubMed

    Sánchez-López, E; Sánchez-Rodríguez, M I; Marinas, A; Marinas, J M; Urbano, F J; Caridad, J M; Moalem, M

    2016-08-15

    Authentication of extra virgin olive oil (EVOO) is an important topic for olive oil industry. The fraudulent practices in this sector are a major problem affecting both producers and consumers. This study analyzes the capability of FT-Raman combined with chemometric treatments of prediction of the fatty acid contents (quantitative information), using gas chromatography as the reference technique, and classification of diverse EVOOs as a function of the harvest year, olive variety, geographical origin and Andalusian PDO (qualitative information). The optimal number of PLS components that summarizes the spectral information was introduced progressively. For the estimation of the fatty acid composition, the lowest error (both in fitting and prediction) corresponded to MUFA, followed by SAFA and PUFA though such errors were close to zero in all cases. As regards the qualitative variables, discriminant analysis allowed a correct classification of 94.3%, 84.0%, 89.0% and 86.6% of samples for harvest year, olive variety, geographical origin and PDO, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Vibrational Raman spectra of hydrogen clathrate hydrates from density functional theory

    NASA Astrophysics Data System (ADS)

    Ramya, K. R.; Venkatnathan, Arun

    2013-03-01

    Hydrogen clathrate hydrates are promising sources of clean energy and are known to exist in a sII hydrate lattice, which consists of H2 molecules in dodecahedron (512) and hexakaidecahedron (51264) water cages. The formation of these hydrates which occur in extreme thermodynamic conditions is known to be considerably reduced by an inclusion of tetrahydrofuran (THF) in cages of these hydrate lattice. In this present work, we employ the density functional theory with a dispersion corrected (B97-D) functional to characterize vibrational Raman modes in the cages of pure and THF doped hydrogen clathrate hydrates. Our calculations show that the symmetric stretch of the H2 molecule in the 51264H2.THF cage is blueshifted compared to the 51264H2 cage. However, all vibrational modes of water molecules are redshifted which suggest reduced interaction between the H2 molecule and water molecules in the 51264H2.THF cage. The symmetric and asymmetric O-H stretch of water molecules in 512H2, 51264H2, and 51264H2.THF cages are redshifted compared with the corresponding guest free cages due to interactions between encapsulated H2 molecules and water molecules of the cages. The low frequency modes contain contributions from contraction and expansion of water cages and vibration of water molecules due to hydrogen bonding and these modes could possibly play an important role in the formation of the hydrate lattice.

  15. Effect of silicate structure on thermodynamic properties of calcium silicate melts: Quantitative analysis of Raman spectra

    NASA Astrophysics Data System (ADS)

    Park, Joo Hyun

    2013-05-01

    The distribution of silicate anionic species (Qn units, n=0, 1, 2, 3) and the chemical speciation of oxygen in CaO-SiO2-MO (M=Mn and Mg) slags were investigated by micro-Raman spectroscopic analysis. Furthermore, the thermochemical properties were evaluated using a concentration of free oxygen and a degree of polymerization. A good linear relationship was obtained between sulfide capacity and concentration of free oxygen in the CaO-SiO2 (-MnO) melts at 1500 to 1600 °C. However, even though there was more abundant free oxygen in the CaO-SiO2-MgO system than in the CaO-SiO2 system, the sulfide capacity of the former was lower than the latter, indicating that the sulfur dissolution behavior in the silicate melts cannot be simply explained by the content of free oxygen, because the composition dependency of the stability ratio of oxygen and sulfide ions should be taken into account. The excess free energy of CaO, MgO and MnO linearly decreased as the ln (Q3/Q2) increased. The effect of the degree of polymerization on the excess free energy of mixing of MgO-containing slag was larger than that of MnO-containing slag, which was explained by the difference of the ionization potential between Mn2+ and Mg2+ ions.

  16. Line mixing effects in isotropic Raman spectra of pure N2: a classical trajectory study.

    PubMed

    Ivanov, Sergey V; Boulet, Christian; Buzykin, Oleg G; Thibault, Franck

    2014-11-14

    Line mixing effects in the Q branch of pure N2 isotropic Raman scattering are studied at room temperature using a classical trajectory method. It is the first study using an extended modified version of Gordon's classical theory of impact broadening and shift of rovibrational lines. The whole relaxation matrix is calculated using an exact 3D classical trajectory method for binary collisions of rigid N2 molecules employing the most up-to-date intermolecular potential energy surface (PES). A simple symmetrizing procedure is employed to improve off-diagonal cross-sections to make them obeying exactly the principle of detailed balance. The adequacy of the results is confirmed by the sum rule. The comparison is made with available experimental data as well as with benchmark fully quantum close coupling [F. Thibault, C. Boulet, and Q. Ma, J. Chem. Phys. 140, 044303 (2014)] and refined semi-classical Robert-Bonamy [C. Boulet, Q. Ma, and F. Thibault, J. Chem. Phys. 140, 084310 (2014)] results. All calculations (classical, quantum, and semi-classical) were made using the same PES. The agreement between classical and quantum relaxation matrices is excellent, opening the way to the analysis of more complex molecular systems.

  17. [Variation of Raman spectra of oligoclase under 1.0-4.4 GPa].

    PubMed

    Xie, Chao; Du, Jian-guo; Cui, Yue-ju; Chen, Zhi; Zhang, Wei-bin; Yi, Li; Deng, Li

    2012-03-01

    Variation of crystal structure of oligoclase with pressure was investigated by the approach of diamond anvil cell (DAC) and in situ micro-Raman spectroscopic measurement at room temperature and under pressures from 1.0 to 4.4 GPa. At 2.9 GPa a new peak round 517 cm(-1) appeared, and a new phase was produced. Near 3.4 GPa a major discontinuity occurs in the pressure dependence of 288 cm(-1) peak arising from the stretching mode of M-O, and 517 cm(-1) peak disappeared, it implied that the oligoclase underwent triclinic to monoclinic phase transition completely at about 3.4 GPa. The peaks at 458 and 516 cm(-1) peaks arising from flexural vibrational mode of Si-O-Si shifted linearly with the increasing pressures, the pressure-related slopes are 1.667 cm(-1)/GPa and 3.560 cm(-1)/GPa, respectively, whereas, the flexural vibrational mode of Al-O-Al at 480 cm(-1) did not shifted linearly with the increasing pressures. The position of 288 cm(-1) peak did not change obviously in comparision with 458, 516 and 480 cm(-1) peaks, which shifted to lower frequency during decompression. The phase transition pressure of feldspar relates to the species of cation in the octatomic rings.

  18. Retrieval Of Cloud Pressure And Chlorophyll Content Using Raman Scattering In GOME Ultraviolet Spectra

    NASA Technical Reports Server (NTRS)

    Atlas, Robert (Technical Monitor); Joiner, Joanna; Vasikov, Alexander; Flittner, David; Gleason, James; Bhartia, P. K.

    2002-01-01

    Reliable cloud pressure estimates are needed for accurate retrieval of ozone and other trace gases using satellite-borne backscatter ultraviolet (buv) instruments such as the global ozone monitoring experiment (GOME). Cloud pressure can be derived from buv instruments by utilizing the properties of rotational-Raman scattering (RRS) and absorption by O2-O2. In this paper we estimate cloud pressure from GOME observations in the 355-400 nm spectral range using the concept of a Lambertian-equivalent reflectivity (LER) surface. GOME has full spectral coverage in this range at relatively high spectral resolution with a very high signal-to-noise ratio. This allows for much more accurate estimates of cloud pressure than were possible with its predecessors SBUV and TOMS. We also demonstrate the potential capability to retrieve chlorophyll content with full-spectral buv instruments. We compare our retrieved LER cloud pressure with cloud top pressures derived from the infrared ATSR instrument on the same satellite. The findings confirm results from previous studies that showed retrieved LER cloud pressures from buv observations are systematically higher than IR-derived cloud-top pressure. Simulations using Mie-scattering radiative transfer algorithms that include O2-O2 absorption and RRS show that these differences can be explained by increased photon path length within and below cloud.

  19. DFT calculation of vibrational frequencies of clusters in GaAs and the Raman spectra

    NASA Astrophysics Data System (ADS)

    Radhika Devi, V.; Shrivastava, Keshav N.

    2012-09-01

    We have calculated the vibrational frequencies of clusters of Ga and As atoms from the first principles using the density-functional theory (DFT) method and the local-density approximation (LDA). We find that the calculated value of 286.2 cm-1 for a linear cluster of Ga2As2 is very near the experimental value of 292 ± 4 cm-1. The calculated value of 289.4 cm-1 for Ga2As6 (dumb bell) cluster is indeed very near the experimental value. There are strong phonon correlations so that the cluster frequency is within the dispersion relation of the crystal LO value. There is a weak line in the experimental Raman spectrum at 268 cm-1 which is very near the value of 267.3 cm-1 calculated for the Ga2As (triangular) cluster. The weak lines corresponding to the linear bonds provide the strength to the amorphous samples. There are clusters of atoms in the glassy state of GaAs.

  20. Structure and polarised IR and Raman spectra of the solid complex betaine trichloroacetic acid

    NASA Astrophysics Data System (ADS)

    Baran, J.; Barnes, A. J.; Engelen, B.; Panthöfer, M.; Pietraszko, A.; Ratajczak, H.; Sledz, M.

    2000-09-01

    The structural chemistry and phase transitions of the molecular complex of betaine with trichloroacetic acid (C7H12Cl3NO4, BET-TClA) have been investigated by means of single crystal and powder X-ray diffraction, thermal analysis (DSC) and FTIR and FT-Raman measurements. BET-TClA crystallises in the orthorhombic space group Pnma with Z=4 in a layer structure of hydrogen bonded betainium cations (BETH+) and trichloroacetate anions (TClA-). The structural irregularities, which have been found for the TClA- sublattice, are treated on the basis of a combined model of orientational disorder and thermal libration. DSC as well as temperature dependent FTIR measurements resolve two reversible low temperature phase transitions at 177 and 187 K, respectively, of which only one was detectable with the help of powder X-ray diffraction. In addition, the FTIR measurements point to the existence of a further, hitherto unknown, low temperature phase transition below 100 K.

  1. Atomistic modeling of the low-frequency mechanical modes and Raman spectra of icosahedral virus capsids

    NASA Astrophysics Data System (ADS)

    Dykeman, Eric C.; Sankey, Otto F.

    2010-02-01

    We describe a technique for calculating the low-frequency mechanical modes and frequencies of a large symmetric biological molecule where the eigenvectors of the Hessian matrix are determined with full atomic detail. The method, which follows order N methods used in electronic structure theory, determines the subset of lowest-frequency modes while using group theory to reduce the complexity of the problem. We apply the method to three icosahedral viruses of various T numbers and sizes; the human viruses polio and hepatitis B, and the cowpea chlorotic mottle virus, a plant virus. From the normal-mode eigenvectors, we use a bond polarizability model to predict a low-frequency Raman scattering profile for the viruses. The full atomic detail in the displacement patterns combined with an empirical potential-energy model allows a comparison of the fully atomic normal modes with elastic network models and normal-mode analysis with only dihedral degrees of freedom. We find that coarse-graining normal-mode analysis (particularly the elastic network model) can predict the displacement patterns for the first few (˜10) low-frequency modes that are global and cooperative.

  2. Line mixing effects in isotropic Raman spectra of pure N2: A classical trajectory study

    NASA Astrophysics Data System (ADS)

    Ivanov, Sergey V.; Boulet, Christian; Buzykin, Oleg G.; Thibault, Franck

    2014-11-01

    Line mixing effects in the Q branch of pure N2 isotropic Raman scattering are studied at room temperature using a classical trajectory method. It is the first study using an extended modified version of Gordon's classical theory of impact broadening and shift of rovibrational lines. The whole relaxation matrix is calculated using an exact 3D classical trajectory method for binary collisions of rigid N2 molecules employing the most up-to-date intermolecular potential energy surface (PES). A simple symmetrizing procedure is employed to improve off-diagonal cross-sections to make them obeying exactly the principle of detailed balance. The adequacy of the results is confirmed by the sum rule. The comparison is made with available experimental data as well as with benchmark fully quantum close coupling [F. Thibault, C. Boulet, and Q. Ma, J. Chem. Phys. 140, 044303 (2014)] and refined semi-classical Robert-Bonamy [C. Boulet, Q. Ma, and F. Thibault, J. Chem. Phys. 140, 084310 (2014)] results. All calculations (classical, quantum, and semi-classical) were made using the same PES. The agreement between classical and quantum relaxation matrices is excellent, opening the way to the analysis of more complex molecular systems.

  3. Surface-enhanced Raman scattering (SERS) spectra of hemoglobin of mouse and rabbit with self-assembled nano-silver film.

    PubMed

    Kang, Yipu; Si, Minzhen; Zhu, Yanqing; Miao, Lei; Xu, Gang

    2013-05-01

    The nano-silver film was prepared by electrolysis method. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to detect the morphology of the nano-silver particles. The SERS spectra of the hemoglobin (rabbit and mouse) on nano-silver film were gained. It could be known from the SERS spectra that the nano-silver films could enhance the Raman signal of the hemoglobin efficiently, and the sodium citrate and PBS create no influence to the SERS spectra of the hemoglobin. Using this electrolysis technique to fabricate highly bio-active, stable, reusable, and low-cost SERS substrate will be useful in the development of hemoglobin detection.

  4. The use of UV, FT-IR and Raman spectra for the identification of the newest penem analogs: solutions based on mathematic procedure and the density functional theory.

    PubMed

    Cielecka-Piontek, J; Lewandowska, K; Barszcz, B; Paczkowska, M

    2013-02-15

    The application of ultraviolet, FT-IR and Raman spectra was proposed for identification studies of the newest penem analogs (doripenem, biapenem and faropenem). An identification of the newest penem analogs based on their separation from related substances was achieved after the application of first derivative of direct spectra in ultraviolet which permitted elimination of overlapping effects. A combination of experimental and theoretical studies was performed for analyzing the structure and vibrational spectra (FT-IR and Raman spectra) of doripenem, biapenem and faropenem. The calculations were conducted using the density functional theory with the B3LYP hybrid functional and 6-31G(d,p) basis set. The confirmation of the applicability of the DFT methodology for interpretation of vibrational IR and Raman spectra of the newest penem analogs contributed to determination of changes of vibrations in the area of the most labile bonds. By employing the theoretical approach it was possible to eliminate necessity of using reference standards which - considering the instability of penem analogs - require that correction coefficients are factored in.

  5. Time-resolved coherent anti-Stokes Raman spectroscopy (CARS) and the measurement of vibrational spectra in shock-compressed molecular materials

    SciTech Connect

    Moore, D.S.; Schmidt, S.C.

    1990-01-01

    We present the use of coherent anti-Stokes Raman scattering (CARS) in conjunction with a two-stage light-gas gun to obtain vibrational spectra of shock-compressed liquid N{sub 2}, O{sub 2}, CO, and their mixtures. The experimental spectra are compared to spectra calculated using a semiclassical model for CARS intensities to obtain vibrational frequencies, peak Raman susceptibilities, and linewidths. The derived spectroscopic parameters suggest thermal equilibrium of the vibrational populations is established in less than a few nanoseconds after shock passage. Vibrational temperatures obtained are compared to those derived from equation-of-state calculations. Shifts in the vibrational frequencies reflect the influence of increased density and temperature on the intramolecular motion. 11 refs., 5 figs.

  6. Theoretical Investigation of C-H Vibrational Spectroscopy. 2. Unified Assignment Method of IR, Raman, and Sum Frequency Generation Spectra of Ethanol.

    PubMed

    Wang, Lin; Ishiyama, Tatsuya; Morita, Akihiro

    2017-09-14

    Using the flexible and polarizable model in the preceding paper, we performed comprehensive analysis of C-H stretching vibrations of ethanol and partially deuterated ones by molecular dynamics (MD) simulation. The overlapping band structures of the C-H stretching region including (i) methyl and methylene, (ii) the number of modes with Fermi resonances, and (iii) different trans/gauche conformers are disentangled by various analysis methods, such as isotope exchange, empirical potential parameter shift analysis, and separate calculations of conformers. The present analysis with MD simulation revealed unified assignment of infrared, Raman, and sum frequency generation (SFG) spectra. The analysis confirmed that the different conformers have significant influence on the assignment of CH2 vibrations. Band components and their signs in the imaginary χ((2)) spectra of SFG under various polarizations are also understood from the common assignment with the infrared and Raman spectra.

  7. Molecular structure, natural bond analysis, vibrational and electronic spectra, surface enhanced Raman scattering and Mulliken atomic charges of the normal modes of [Mn(DDTC)2] complex

    NASA Astrophysics Data System (ADS)

    Téllez S., Claudio A.; Costa, Anilton C.; Mondragón, M. A.; Ferreira, Glaucio B.; Versiane, O.; Rangel, J. L.; Lima, G. Müller; Martin, A. A.

    2016-12-01

    Theoretical and experimental bands have been assigned for the Fourier Transform Infrared and Raman spectra of the bis(diethyldithiocarbamate)Mn(II) complex, [Mn(DDTC)2]. The calculations have been based on the DFT/B3LYP method, second derivative spectra and band deconvolution analysis. The UV-vis experimental spectra were measured in acetonitrile solution, and the calculated electronic spectrum was obtained using the TD/B3LYP method with 6-311G(d, p) basis set for all atoms. Charge transfer bands and those d-d spin forbidden were assigned in the UV-vis spectrum. The natural bond orbital analysis was carried out using the DFT/B3LYP method and the Mn(II) hybridization leading to the planar geometry of the framework was discussed. Surface enhanced Raman scattering (SERS) was also performed. Mulliken charges of the normal modes were obtained and related to the SERS enhanced bands.

  8. SiGe superlattice nanocrystal infrared and Raman spectra: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Abdulsattar, Mudar A.

    2012-02-01

    Infrared and Raman vibrational spectrum are calculated using ab initio density functional theory for SiGe superlattice nanocrystal of approximately 1.6 nm length. After obtaining the optimum positions of atoms via geometrical optimization using density functional theory, coupled perturbed Hartree-Fock equations are solved iteratively to obtain vibrational spectrum. Frequencies of vibrations are analyzed against intensities, reduced masses, and vibrational force constants. A scale factor of 0.81 is suggested to correct the frequencies of the present calculations that are obtained using STO-3 G basis functions. Results show that SiGe nanocrystals have complex and rich vibrational spectrum that can be generally divided into three regions. The highest reduced masses are in the first region where Si and Ge atoms are the main contributors to vibrations with a smaller number of vibrations attributed to hydrogen atoms. The highest intensity lines in SiGe superlattice nanocrystals are in the middle region where most of the modes of vibration can be excited. The third region is characterized by high force constants. The first region shows a redshift of the original Ge-Si bond vibration from the calculated bulk 418 cm-1 to the present nanocrystal 395 cm-1. Hydrogen vibrations interferences are found in the same redshift region that might induce uncertainties in the experimentally measured redshift. Si-H and Ge-H vibrations are observed mainly in the second and third region and less frequently in the first region. These vibrations include modes of vibration such as symmetric, asymmetric, wagging, scissor, rocking, and twisting modes.

  9. Raman spectra of vibrational and librational modes in methane clathrate hydrates using density functional theory

    NASA Astrophysics Data System (ADS)

    Ramya, K. R.; Pavan Kumar, G. V.; Venkatnathan, Arun

    2012-05-01

    The sI type methane clathrate hydrate lattice is formed during the process of nucleation where methane gas molecules are encapsulated in the form of dodecahedron (512CH4) and tetrakaidecahedron (51262CH4) water cages. The characterization of change in the vibrational modes which occur on the encapsulation of CH4 in these cages plays a key role in understanding the formation of these cages and subsequent growth to form the hydrate lattice. In this present work, we have chosen the density functional theory (DFT) using the dispersion corrected B97-D functional to characterize the Raman frequency vibrational modes of CH4 and surrounding water molecules in these cages. The symmetric and asymmetric C-H stretch in the 512CH4 cage is found to shift to higher frequency due to dispersion interaction of the encapsulated CH4 molecule with the water molecules of the cages. However, the symmetric and asymmetric O-H stretch of water molecules in 512CH4 and 51262CH4 cages are shifted towards lower frequency due to hydrogen bonding, and interactions with the encapsulated CH4 molecules. The CH4 bending modes in the 512CH4 and 51262CH4 cages are blueshifted, though the magnitude of the shifts is lower compared to modes in the high frequency region which suggests bending modes are less affected on encapsulation of CH4. The low frequency librational modes which are collective motion of the water molecules and CH4 in these cages show a broad range of frequencies which suggests that these modes largely contribute to the formation of the hydrate lattice.

  10. [Study on the Recognition of Liquor Age of Gujing Based on Raman Spectra and Support Vector Regression].

    PubMed

    Wang, Guo-xiang; Wang, Hai-yan; Wang, Hu; Zhang, Zheng-yong; Liu, Jun

    2016-03-01

    It is an important and difficult research point to recognize the age of Chinese liquor rapidly and exactly in the field of liquor analyzing, which is also of great significance to the healthy development of the liquor industry and protection of the legitimate rights and interests of consumers. Spectroscopy together with the pattern recognition technology is a preferred method of achieving rapid identification of wine quality, in which the Raman Spectroscopy is promising because of its little affection of water and little or free of sample pretreatment. So, in this paper, Raman spectra and support vector regression (SVR) are used to recognize different ages and different storing time of the liquor of the same age. The innovation of this paper is mainly reflected in the following three aspects. First, the application of Raman in the area of liquor analysis is rarely reported till now. Second, the concentration of studying the recognition of wine age, while most studies focus on studying specific components of liquor and studies together with the pattern recognition method focus more on the identification of brands or different types of base wine. The third one is the application of regression analysis framework, which cannot be only used to identify different years of liquor, but also can be used to analyze different storing time, which has theoretical and practical significance to the research and quality control of liquor. Three kinds of experiments are conducted in this paper. Firstly, SVR is used to recognize different ages of 5, 8, 16 and 26 years of the Gujing Liquor; secondly, SVR is also used to classify the storing time of the 8-years liquor; thirdly, certain group of train data is deleted form the train set and put into the test set to simulate the actual situation of liquor age recognition. Results show that the SVR model has good train and predict performance in these experiments, and it has better performance than other non-liner regression method such

  11. The effect of intermolecular dipole-dipole interaction on Raman spectra of polyconjugated molecules: density functional theory simulations and mathematical models.

    PubMed

    Milani, Alberto; Del Zoppo, Mirella; Tommasini, Matteo; Zerbi, Giuseppe

    2008-02-14

    In this work, we analyze the effect of intermolecular dipole-dipole interactions on Raman spectra of polyconjugated molecules. In particular, the behavior of push-pull polyenes has been studied. By means of density functional theory (DFT) calculations on isolated molecules and dimers, we have found that both the frequencies and intensities of the strongest Raman lines (R mode) are strongly influenced by intermolecular interactions. The results have been rationalized within the effective conjugation coordinate (ECC) theory developed in the past. The calculations for different configurations have also shown that the Raman spectra are sensible to different intermolecular geometries, thus implying a possible application of vibrational spectroscopy to the study of supramolecular properties of polyconjugated systems. The comparison with the available experimental spectra confirms the results obtained with the DFT computations. Finally, a very simple mathematical model is proposed for the prediction of the Raman frequencies of interacting systems. From the knowledge of just a few quantities for the isolated molecule and of some geometrical parameters, an estimate of the frequency of the dimers can be obtained. Despite its simplicity, this model gives results in very good agreement with DFT calculations carried out explicitly on dimers in several different arrangements.

  12. Effects of collective excitations on the G-band and RBM modes in the Raman spectra of metallic unfilled and filled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Gayen, Saurabh; Behera, Surjyo; Bose, Shyamalendu

    2006-03-01

    The Raman spectra of a single-wall carbon nanotube (SWNT) consist of three types of modes; (i) the high frequency G-mode arising out of tangential oscillations of carbon atoms, (ii) D-mode due to the defects in the nanotube and (iii) the low frequency radial breathing mode (RBM) resulting out of radial oscillations of the carbon atoms. In this paper we theoretically investigate the effects of collective oscillations of electrons (plasmons) on the G and RBM modes in the Raman spectra of a filled and unfilled metallic SWNT. Inclusion of plasmon and the filling (rattler) atom produces four peaks in the Raman spectra in general. The positions and relative strengths of the Raman peaks [1] depend upon phonon frequencies of the nanotube and that of the filling atoms, the plasmon frequency, the strength of the electron-phonon interaction, strength of the interactions between the nanotube phonons and rattler phonon and radius of the nanotube [2]. Usually the intensity of the G-mode is higher than that of RBM. For heavier filling atoms the frequency of the rattler phonon is lower in value, which may broaden the peak to such an extent that it may disappear in the background spectrum altogether. 1.S.M. Bose et al., Physica B 351, 129 (2004) 2. S.M. Bose, S.Gayen and S. Behera, Phys. Rev. B 72, 153402 (2005).

  13. Allergic reactions in red tattoos: Raman spectroscopy for 'fingerprint' detection of chemical risk spectra in tattooed skin and culprit tattoo inks.

    PubMed

    Hutton Carlsen, K; Køcks, M; Sepehri, M; Serup, J

    2016-11-01

    The aim of this study was to assess the feasibility of Raman spectroscopy as a screening technique for chemical characterisation of tattoo pigments in pathologic reacting tattoos and tattoo ink stock products to depict unsafe pigments and metabolites of pigments. Twelve dermatome shave biopsies from allergic reactions in red tattoos were analysed with Raman spectroscopy (A 785-nm 300 mW diode laser). These were referenced to samples of 10 different standard tattoo ink stock products, three of these identified as the culprit inks used by the tattooist and thus by history the source of the allergy. Three primary aromatic amine (PAA) laboratory standards (aniline, o-anisidine and 3,3'-dichlorobenzidine) were also studied. Application of Raman spectroscopy to the shave biopsies was technically feasible. In addition, all ten inks and the three PAA standards could be discriminated. 10/12 shave biopsies provided clear fingerprint Raman signals which differed significantly from background skin, and Raman spectra from 8/12 biopsies perfectly matched spectra from the three culprit ink products. The spectrum of one red ink (a low cost product named 'Tattoo', claimed to originate from Taiwan, no other info on label) was identified in 5/12 biopsies. Strong indications of the inks 'Bright Red' and 'Crimson Red' were seen in three biopsies. The three PAA's could not be unambiguously identified. This study, although on a small-scale, demonstrated Raman spectroscopy to be feasible for chemical analysis of red pigments in allergic reactions. Raman spectroscopy has a major potential for fingerprint screening of problematic tattoo pigments in situ in skin, ex vivo in skin biopsies and in tattoo ink stock products, thus, to eliminate unsafe ink products from markets. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  14. Surface-enhanced Raman scattering spectra of adsorbates on Cu2O nanospheres: charge-transfer and electromagnetic enhancement

    NASA Astrophysics Data System (ADS)

    Jiang, Li; You, Tingting; Yin, Penggang; Shang, Yang; Zhang, Dongfeng; Guo, Lin; Yang, Shihe

    2013-03-01

    Surface-enhanced Raman scattering (SERS) spectra of 4-mercaptobenzoic acid (4-MBA) have been investigated on the surface of Cu2O nanospheres. The SERS signals were believed to originate from the static chemical enhancement, resonant chemical enhancement and electromagnetic enhancement. The coupling between the adsorbates and the semiconductor, evidenced by the shift in absorption spectrum of modified Cu2O and the enhancement of non-totally symmetric modes of the 4-MBA and 4-mercaptopyridine (4-MPY) molecules, were invoked to explain the experimental results. Furthermore, simulations were employed to investigate the nature of the enhancement mechanisms operative between the molecules and the semiconductor. Density functional theory (DFT) calculations suggested a charge transfer (CT) transition process between the molecules and the Cu2O nanospheres. Three-dimensional finite-difference time domain (3D-FDTD) simulations were conducted to map out the electromagnetic field around the Cu2O nanospheres. The experimental and simulation results have revealed the promise of the Cu2O nanospheres as a good SERS substrate and the prospect of using the SERS substrate as a valuable tool for in situ investigation and assay of the adsorption behavior on semiconductor surfaces.Surface-enhanced Raman scattering (SERS) spectra of 4-mercaptobenzoic acid (4-MBA) have been investigated on the surface of Cu2O nanospheres. The SERS signals were believed to originate from the static chemical enhancement, resonant chemical enhancement and electromagnetic enhancement. The coupling between the adsorbates and the semiconductor, evidenced by the shift in absorption spectrum of modified Cu2O and the enhancement of non-totally symmetric modes of the 4-MBA and 4-mercaptopyridine (4-MPY) molecules, were invoked to explain the experimental results. Furthermore, simulations were employed to investigate the nature of the enhancement mechanisms operative between the molecules and the semiconductor

  15. Spectra and structure of gallium compounds. Part X. Infrared and Raman spectra, vibrational assignment, and normal coordinate calculations for trimethylaminegallium trichloride

    NASA Astrophysics Data System (ADS)

    Durig, J. R.; Chatterjee, K. K.

    1982-11-01

    The far IR (450-480 cm -1) and Raman (3200-3230 cm -1) spectra of (CH 3) 3 NGaCl 3 have been recorded in the solid state and interpreted in detail on the basis of C3 molecular symmetry. A modified valence force field model is used to calculate the frequencies and potential energy distribution of the adduct. The calculated force constants of the adduct are compared with those previously reported for the free Lewis acid and the free Lewis base moieties, and the observed differences ascribed to geometrical changes of the uncomplexed species on adduct formation and explained on the basis of the VSEPR model and non-bond interactions. Extensive coupling is observed between the GaN stretching mode and the NC 3 symmetric stretching and the NC 3 symmetric deformational modes. Strong coupling interaction is also found between the GaCl 3 antisymmetric stretch and the NC 3 antisymmetric deformation. The calculated value of 2.50 mdyn Å -1 for the GaN stretching force constant in (CH 3) 3NGaCl 3 is larger than any of those previously determined in complexes such as (CH 3) 3NGaH 3 (2.43 mdyn Å -1), (CH 3) 3NGa(CH 3) 3 (1.61 mdyn Å -1), and H 3NGa(CH 3) 3 (1.08 mdyn Å -1). The observed variations in the magnitudes of the stretching force constants of the donor—acceptor dative bond is found to be consistent with the estimated relative stabilities of this series of adducts.

  16. Spectra and structure of gallium compounds. Part X. Infrared and Raman spectra, vibrational assignment, and normal coordinate calculations for trimethylaminegallium trichloride

    NASA Astrophysics Data System (ADS)

    Durig, J. R.; Chatterjee, K. K.

    The far IR (450-480 cm-1) and Raman (3200-3230 cm-1) spectra of (CH3)3 NGaCl3 have been recorded in the solid state and interpreted in detail on the basis of C3 molecular symmetry. A modified valence force field model is used to calculate the frequencies and potential energy distribution of the adduct. The calculated force constants of the adduct are compared with those previously reported for the free Lewis acid and the free Lewis base moieties, and the observed differences ascribed to geometrical changes of the uncomplexed species on adduct formation and explained on the basis of the VSEPR model and non-bond interactions. Extensive coupling is observed between the GaN stretching mode and the NC3 symmetric stretching and the NC3 symmetric deformational modes. Strong coupling interaction is also found between the GaCl3 antisymmetric stretch and the NC3 antisymmetric deformation. The calculated value of 2.50 mdyn Å-1 for the GaN stretching force constant in (CH3)3NGaCl3 is larger than any of those previously determined in complexes such as (CH3)3NGaH3 (2.43 mdyn Å-1), (CH3)3NGa(CH3)3 (1.61 mdyn Å-1), and H3NGa(CH3)3 (1.08 mdyn Å-1). The observed variations in the magnitudes of the stretching force constants of the donor-acceptor dative bond is found to be consistent with the estimated relative stabilities of this series of adducts.

  17. State-by-state investigation of destructive interference in resonance Raman spectra of neutral tyrosine and the tyrosinate anion with the simplified sum-over-states approach.

    PubMed

    Cabalo, Jerry B; Saikin, Semion K; Emmons, Erik D; Rappoport, Dmitrij; Aspuru-Guzik, Alán

    2014-10-16

    UV resonance Raman scattering is uniquely sensitive to the molecular electronic structure as well as intermolecular interactions. To better understand the relationship between electronic structure and resonance Raman cross section, we carried out combined experimental and theoretical studies of neutral tyrosine and the tyrosinate anion. We studied the Raman cross sections of four vibrational modes as a function of excitation wavelength, and we analyzed them in terms of the contributions of the individual electronic states as well as of the Albrecht A and B terms. Our model, which is based on time-dependent density functional theory (TDDFT), reproduced the experimental resonance Raman spectra and Raman excitation profiles for both studied molecules with good agreement. We found that for the studied modes, the contributions of Albrecht's B terms in the Raman cross sections were important across the frequency range spanning the L(a,b) and B(a,b) electronic excitations in tyrosine and the tyrosinate anion. Furthermore, we demonstrated that interference with high-energy states had a significant impact and could not be neglected even when in resonance with a lower-energy state. The symmetry of the vibrational modes served as an indicator of the dominance of the A or B mechanisms. Excitation profiles calculated with a damping constant estimated from line widths of the electronic absorption bands had the best consistency with experimental results.

  18. Spin-phonon interactions of multiferroic Bi4Ti3O12-BiFeO3 ceramics: Low-temperature Raman scattering and infrared reflectance spectra investigations

    NASA Astrophysics Data System (ADS)

    Jiang, P. P.; Zhang, X. L.; Chang, P.; Hu, Z. G.; Bai, W.; Li, Y. W.; Chu, J. H.

    2014-04-01

    Optical phonons of multiferroic Bi4Ti3O12-BiFeO3 ceramic have been investigated by low temperature Raman scattering and infrared reflectance spectra. Anomalies at about 85 K can be observed from the temperature dependence of the Raman and infrared modes, which arise from spin-phonon interaction during antiferromagnetic to paramagnetic phase transition. It was found that the change of exchange interaction in magnetic phase transition can be induced by Fe-O-Fe octahedral tilting driven from the A-site atoms. Moreover, ferroelectricity-related displacement of Bismuth atoms suggests the coupling of magnetic and ferroelectric orders.

  19. Analysis of the Raman spectra of Ca(2+)-dipicolinic acid alone and in the bacterial spore core in both aqueous and dehydrated environments.

    PubMed

    Kong, Lingbo; Setlow, Peter; Li, Yong-qing

    2012-08-21

    The core of dormant bacterial spores suspended in water contains a large depot of dipicolinic acid (DPA) chelated with divalent cations, predominantly Ca(2+) (CaDPA), and surrounded by water molecules. Since the intensities of the vibration bands of CaDPA molecules depend significantly on the water content in the CaDPA's environment, the Raman spectra of CaDPA in spores may allow the determination of the spore core's hydration state. We have measured Raman spectra of single spores of three Bacillus species in different hydration states including the spores suspended in water, air-dried and vacuum-dried. As a comparison, we also measured the Raman spectra of CaDPA and DPA in different forms including in aqueous solution, and as amorphous powder and crystalline form. We also monitored changes in Raman spectra of an individual spore during dehydration under vacuum. The results indicated that (1) the state of CaDPA in the core of a spore suspended in water is close to an amorphous solid or a glassy state, but still mixed with water molecules; (2) the ratio of intensities of Raman bands at 1575 and 1017 cm(-1) (I(1575)/I(1017)) is sensitive to the water content in the CaDPA's environment; (3) variations in I(1575)/I(1017) are small (∼4%) in a population of dormant Bacillus spores suspended in water; and (4) the I(1575)/I(1017) ratio increases significantly during dehydration under vacuum. Consequently, measurement of the I(1575)/I(1017) ratio of CaDPA in spores may allow a qualitative estimation of the degree of hydration of the bacterial spore's core.

  20. [Characteristics of Raman spectra of minerals in the veins of Wenchuan earthquake fault zone].

    PubMed

    Xie, Chao; Zhou, Ben-gang; Liu, Lei; Zhou, Xiao-cheng; Yi, Li; Chen, Zhi; Cui, Yue-ju; Li, Jing; Chen, Zheng-wei; Du, Jian-guo

    2015-01-01

    Quartz in the veins at the Shenxigou section of Wenchuan earthquake fault zone was investigated by micro-Raman spectroscopic measurement, and the distribution of compressive stress in the fault zone was estimated by the frequency shifts of the 464 cm-1 vibrational mode of quartz grains in the veins. It was showed that the 464 cm-1 peak arising from the quartz grains in the veins near the fault plane shifts by 3. 29 cm-1 , and the corresponding compressive stress is 368. 63 MPa, which is significantly lower than the stress accumulation on both sides due to multi-stage events. Stress accumulation increased with moving away from the fault plane in the footwall with the offset of the 464 cm-1 peak arising from the quartz grains in the veins increasing, which can reach 494. 77 MPa at a distance of 21 m with a high offset of 4. 40 cm-1 of the 464 cm-1 peak. The compressive stress gets the maximum value of 519.87 MPa at a distance of 10 m from the fault plane in the hanging wall with the offset of the 464 cm-1 peak arising from the quartz grains in the veins being 4. 62 cm-1, followed by a sudden drop in stress accumulation, and it drops to 359. 59 MPa at a distance of 17 m. Because of moving away from the foult plane at the edge of the foult zone, the stress drops to 359. 59 MPa with a small value of 464 cm-1 peak offset 3. 21 cm-1 at a distance of 27 m from the fault plane in the hanging wall due to the little effect by the fault activity. Therefore, the stress of Wenchuan earthquake fault zone is partially released, but the rest of the stress distribution is uneven, and there is also a high stress accumulation in somewhere in the fault zone, which reflects that the mechanical properties of the rocks in the fault zone have a characteristic of unevenness in space.