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Sample records for anharmonic vibrational spectroscopy

  1. Anharmonic Vibrational Dynamics of DNA Oligomers

    CERN Document Server

    Kühn, O; Krishnan, G M; Fidder, H; Heyne, K

    2008-01-01

    Combining two-color infared pump-probe spectroscopy and anharmonic force field calculations we characterize the anharmonic coupling patterns between fingerprint modes and the hydrogen-bonded symmetric NH$_2$ stretching vibration in adenine-thymine dA$_{20}$-dT$_{20}$ DNA oligomers. Specifically, it is shown that the anharmonic coupling between the NH$_2$ bending and the CO stretching vibration, both absorbing around 1665 cm-1, can be used to assign the NH$_2$ fundamental transition at 3215 cm-1 despite the broad background absorption of water.

  2. Vibrational spectroscopy of the G...C base pair: Experiment, harmonic and anharmonic calculations, and the nature of the anharmonic couplings

    Czech Academy of Sciences Publication Activity Database

    Brauer, B.; Gerber, R. B.; Kabeláč, Martin; Hobza, Pavel; Bakker, J. M.; Abo-Riziq, A.; Vries de, M. S.

    2005-01-01

    Roč. 109, - (2005), s. 6974-6984. ISSN 1089-5639 Grant ostatní: NSF(US) CHE-0244341 Institutional research plan: CEZ:AV0Z40550506 Keywords : nucleic acids base s * vibrational spectrum * frequencies anharmonicity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.898, year: 2005

  3. Vibrational spectroscopy via the Caldeira-Leggett model with anharmonic system potentials

    CERN Document Server

    Gottwald, Fabian; Kühn, Oliver

    2016-01-01

    The Caldeira-Leggett (CL) model, which describes a system bi-linearly coupled to a harmonic bath, has enjoyed popularity in condensed phase spectroscopy owing to its utmost simplicity. However, the applicability of the model to cases with anharmonic system potentials, as it is required for the description of realistic systems in solution, is questionable due to the presence of the invertibility problem [J. Phys. Chem. Lett., \\textbf{6}, 2722 (2015)] unless the system itself resembles the CL model form. This might well be the case at surfaces or in the solid regime, which we here confirm for a particular example of an iodine molecule in the atomic argon environment under high pressure. For this purpose we extend the recently proposed Fourier method for parameterizing linear generalized Langevin dynamics[J. Chem. Phys., \\textbf{142}, 244110 (2015)] to the non-linear case based on the CL model and perform an extensive error analysis. In order to judge on the applicability of this model in advance, we give handy ...

  4. Gas-phase spectroscopy and anharmonic vibrational analysis of the 3-residue peptide Z-Pro-Leu-Gly-NH2 by the laser desorption supersonic jet technique

    International Nuclear Information System (INIS)

    Highlights: ► UV, IR and hole-burning spectra of a tri-peptide Z-PLG-NH2 were measured in a jet. ► The laser desorption technique was used to evaporate the peptide. ► The conformers were detected but the population is mainly distributed to a single conformation. ► MD simulations and DFT calculations reproduced the IR spectrum except for NH stretch. ► Anharmonic vibrational analysis VQDPT reproduced the splitting of the NH stretch. - Abstract: The electronic excitation and infrared (IR) spectra of a capped tri-peptide, Z-PLG-NH2 (Z = benzyloxycarbonyl, P = Pro, L = Leu, G = Gly), were measured in the gas phase by using the laser desorption supersonic jet technique. By measuring an ultraviolet–ultraviolet hole burning spectrum, it was found that Z-PLG-NH2 has the maximum three conformers in the gas phase, but that the population is mainly distributed to a single conformation. Molecular dynamics simulations and density functional theory calculations well-reproduced the observed IR spectrum, except for splitting of the NH stretching bands by a β-turn structure that corresponds to a global minimum structure. Anharmonic vibrational analysis by vibrational quasi-degenerate perturbation theory (VQDPT) successfully reproduced the anharmonic splitting, and confirmed the assignments

  5. Effective harmonic oscillator description of anharmonic molecular vibrations

    Indian Academy of Sciences (India)

    Tapta Kanchan Roy; M Durga Prasad

    2009-09-01

    The validity of an effective harmonic oscillator approximation for anharmonic molecular vibrations is tested and compared with vibrational self consistent field and vibrational configurational interaction results. The effective harmonic oscillator is constructed variationally, by taking the trial wave function as a harmonic oscillator eigenfunction with the centroid and width parameter as variational paraeters. It is found that the effective harmonic oscillator approximation provides a description of the anharmonic eigenstates very similar to the vibrational self consistent field results. Coriolis coupling is also included in these studies.

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

    Science.gov (United States)

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

    2016-02-01

    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

  7. Anharmonic force field and vibrational dynamics of CH2F2 up to 5000 cm(-1) studied by Fourier transform infrared spectroscopy and state-of-the-art ab initio calculations.

    Science.gov (United States)

    Tasinato, Nicola; Regini, Giorgia; Stoppa, Paolo; Pietropolli Charmet, Andrea; Gambi, Alberto

    2012-06-01

    Difluoromethane (CH(2)F(2), HFC-32) is a molecule used in refrigerant mixtures as a replacement of the more environmentally hazardous, ozone depleting, chlorofluorocarbons. On the other hand, presenting strong vibration-rotation bands in the 9 μm atmospheric window, it is a greenhouse gas which contributes to global warming. In the present work, the vibrational and ro-vibrational properties of CH(2)F(2), providing basic data for its atmospheric modeling, are studied in detail by coupling medium resolution Fourier transform infrared spectroscopy to high-level electronic structure ab initio calculations. Experimentally a full quantum assignment and accurate integrated absorption cross sections are obtained up to 5000 cm(-1). Ab initio calculations are carried out by using CCSD(T) theory and large basis sets of either the correlation consistent or atomic natural orbital hierarchies. By using vibrational perturbation theory to second order a complete set of vibrational and ro-vibrational parameters is derived from the ab initio quartic anharmonic force fields, which well compares with the spectroscopic constants retrieved experimentally. An excellent agreement between theory and experiment is achieved for vibrational energy levels and integrated absorption cross sections: transition frequencies up to four quanta of vibrational excitation are reproduced with a root mean square deviation (RMSD) of 7 cm(-1) while intensities are predicted within few km mol(-1) from the experiment. Basis set performances and core correlation effects are discussed throughout the paper. Particular attention is focused in the understanding of the anharmonic couplings which rule the vibrational dynamics of the |ν(1)>, |2ν(8)>, |2ν(2)> three levels interacting system. The reliability of the potential energy and dipole moment surfaces in reproducing the vibrational eigenvalues and intensities as well as in modeling the vibrational and ro-vibrational mixings over the whole 400-5000 cm(-1

  8. A local anharmonic treatment of vibrations of methane

    OpenAIRE

    Arias Carrasco, José Miguel; Pérez Bernal, Francisco; A. Frank; Lemus Casillas, Renato; Bijker, R.

    1996-01-01

    The stretching and bending vibrations of methane are studied in a local anharmonic model of molecular vibrations. The use of symmetry-adapted operators reduces the eigenvalue problem to block diagonal form. For the 44 observed energies we obtain a fit with a standard deviation of 0.81 cm$^{-1}$ (and a r.m.s. deviation of 1.16 cm$^{-1}$).

  9. Anharmonic Effects on Vibrational Spectra Intensities: Infrared, Raman, Vibrational Circular Dichroism, and Raman Optical Activity.

    Science.gov (United States)

    Bloino, Julien; Biczysko, Malgorzata; Barone, Vincenzo

    2015-12-10

    The aim of this paper is 2-fold. First, we want to report the extension of our virtual multifrequency spectrometer (VMS) to anharmonic intensities for Raman optical activity (ROA) with the full inclusion of first- and second-order resonances for both frequencies and intensities in the framework of the generalized second-order vibrational perturbation theory (GVPT2) for all kinds of vibrational spectroscopies. Then, from a more general point of view, we want to present and validate the performance of VMS for the parallel analysis of different vibrational spectra for medium-sized molecules (IR, Raman, VCD, ROA) including both mechanical and electric/magnetic anharmonicity. For the well-known methyloxirane benchmark, careful selection of density functional, basis set, and resonance thresholds permitted us to reach qualitative and quantitative agreement between experimental and computed band positions and shapes. Next, the whole series of halogenated azetidinones is analyzed, showing that it is now possible to interpret different spectra in terms of mass, electronegativity, polarizability, and hindrance variation between closely related substituents, chiral spectroscopies being particular effective in this connection. PMID:26580121

  10. Anharmonic Decay of Vibrational States in Amorphous Silicon

    OpenAIRE

    Fabian, Jaroslav; Allen, Philip B.

    1996-01-01

    Anharmonic decay rates are calculated for a realistic atomic model of amorphous silicon. The results show that the vibrational states decay on picosecond timescales and follow the two-mode density of states, similar to crystalline silicon, but somewhat faster. Surprisingly little change occurs for localized states. These results disagree with a recent experiment.

  11. Vibrational Spectra of the Azabenzenes Revisited: Anharmonic Force Fields

    CERN Document Server

    Boese, A D; Martin, Jan M.L.

    2003-01-01

    Anharmonic force fields and vibrational spectra of the azabenzene series (pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, 1,2,3-triazine, 1,2,4-triazine and s-tetrazine) and benzene are obtained using density functional theory (DFT) with the B97-1 exchange-correlation functional and a triple-zeta plus double polarization (TZ2P) basis set. Overall, the fundamental frequencies computed by second-order rovibrational perturbation theory are in excellent agreement with experiment. The resolution of the presently calculated anharmonic spectra is such that they represent an extremely useful tool for the assignment and interpretation of the experimental spectra, especially where resonances are involved.

  12. Bandshapes in vibrational spectroscopy

    International Nuclear Information System (INIS)

    A detailed account is given of the development of modern bandshape theories since 1965. An investigation into the relative contributions of statistical irreversible relaxation processes is described, for a series of molecules in which gradually the length of one molecular axis is increased. An investigation into the theoretical and experimental investigation of the broadening brought about by the effect of fluctuating intermolecular potentials on the vibrational frequency is also described. The effect of an intermolecular perturbative potential on anharmonic and Morse oscillators is discussed and the results are presented of a computation on the broadening of the vibrational band of some diatomic molecules in a rigid lattice type solvent. The broadening of the OH-stretching vibration in a number of aliphatic alcohols, the vibrational bandshapes of the acetylenic C-H stretching vibration and of the symmetric methyl stretching vibration are investigated. (Auth./ C.F.)

  13. Solvent effect on the anharmonic vibrational frequencies in guanine-cytosine base pair

    Science.gov (United States)

    Bende, A.; Muntean, C. M.

    2012-02-01

    We present an ab initio study of the vibrational properties of cytosine and guanine in the Watson-Crick and Hoogsteen base pair configurations. The results are obtained by considering the DFT method together with the Polarizable Continuum Model (PCM) using PBE and B3PW91 exchange-correlation functionals and triple-ζ valence basis set. We investigate the importance of anharmonic corrections for the vibrational modes taking into account the solvent effect of the water environment. In particular, the unusual anharmonic effect of the H+ vibration in the case of the Hoogsteen base pair configuration is discussed.

  14. Vibration-translation energy transfer in anharmonic diatomic molecules. II - The vibrational quantum-number dependence

    Science.gov (United States)

    Mckenzie, R. L.

    1976-01-01

    A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom is used to predict the variation of thermally averaged vibrational-translational rate coefficients with temperature and initial-state quantum number. Multiple oscillator states are included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model is also used as a basis for evaluating several less complete, but analytic, models. Two computationally simple analytic approximations are found that successfully reproduce the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations are identified, and the relative rates of multiple-quantum transitions from excited states are evaluated for several molecular types.

  15. Vibration-translation energy transfer in anharmonic diatomic molecules. 2: The vibrational quantum number dependence

    Science.gov (United States)

    Mckenzie, R. L.

    1975-01-01

    A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom was used to predict the variation of thermally averaged vibration-translation rate coefficients with temperature and initial-state quantum number. Multiple oscillator states were included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model was also used as a basis for evaluating several less complete but analytic models. Two computationally simple analytic approximations were found that successfully reproduced the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations were also identified. The relative rates of multiple-quantum transitions from excited states were evaluated for several molecular types.

  16. Anharmonic calculation of vibration characteristics of the [F(HF)2]''- complex

    International Nuclear Information System (INIS)

    Anharmonic vibrations of the [F(HF)2]- complex were calculated using second-order perturbation theory and the variational method. The interaction of the stretching vibrations of HF molecular fragments and stretching vibrations of the hydrogen bond, as well as the interaction between stretching and bending vibrations of HF was considered in the second method. A more accurate description of the high-frequency of stretching vibration of the HF molecules for the [F(HF)2]- system with a strong hydrogen bond is obtained by the variational method. (authors)

  17. Probing anharmonic properties of nuclear surface vibration by heavy-ion fusion reactions

    OpenAIRE

    Takigawa, N.; Hagino, K.; Kuyucak, S

    1997-01-01

    Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O and ^{144}Sm by the $sd-$ and $sdf-$ interacting boson model, we show that heavy-ion fusion reactions are strongly affected by anharmonic properties of nuclear surface vibrations and nuclear shape, and thus provide a powerful method to study details of nuclear structure and dynamics.

  18. Anharmonicities and coherent vibrational dynamics of phosphate ions in bulk H2O.

    Science.gov (United States)

    Costard, Rene; Tyborski, Tobias; Fingerhut, Benjamin P

    2015-11-28

    Phosphates feature prominently in the energetics of metabolism and are important solvation sites of DNA and phospholipids. Here we investigate the ion H2PO4(-) in aqueous solution combining 2D IR spectroscopy of phosphate stretching vibrations in the range from 900-1300 cm(-1) with ab initio calculations and hybrid quantum-classical molecular dynamics based simulations of the non-linear signal. While the line shapes of diagonal peaks reveal ultrafast frequency fluctuations on a sub-100 fs timescale caused by the fluctuating hydration shell, an analysis of the diagonal and cross-peak frequency positions allows for extracting inter-mode couplings and anharmonicities of 5-10 cm(-1). The excitation with spectrally broad pulses generates a coherent superposition of symmetric and asymmetric PO2(-) stretching modes resulting in the observation of a quantum beat in aqueous solution. We follow its time evolution through the time-dependent amplitude and the shape of the cross peaks. The results provide a complete characterization of the H2PO4(-) vibrational Hamiltonian including fluctuations induced by the native water environment. PMID:26488541

  19. Franck-Condon factors based on anharmonic vibrational wave functions of polyatomic molecules

    Science.gov (United States)

    Rodriguez-Garcia, Valerie; Yagi, Kiyoshi; Hirao, Kimihiko; Iwata, Suehiro; Hirata, So

    2006-07-01

    Franck-Condon (FC) integrals of polyatomic molecules are computed on the basis of vibrational self-consistent-field (VSCF) or configuration-interaction (VCI) calculations capable of including vibrational anharmonicity to any desired extent (within certain molecular size limits). The anharmonic vibrational wave functions of the initial and final states are expanded unambiguously by harmonic oscillator basis functions of normal coordinates of the respective electronic states. The anharmonic FC integrals are then obtained as linear combinations of harmonic counterparts, which can, in turn, be evaluated by established techniques taking account of the Duschinsky rotations, geometry displacements, and frequency changes. Alternatively, anharmonic wave functions of both states are expanded by basis functions of just one electronic state, permitting the FC integral to be evaluated directly by the Gauss-Hermite quadrature used in the VSCF and VCI steps [Bowman et al., Mol. Phys. 104, 33 (2006)]. These methods in conjunction with the VCI and coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] method have predicted the peak positions and intensities of the vibrational manifold in the X˜B12 photoelectron band of H2O with quantitative accuracy. It has revealed that two weakly visible peaks are the result of intensity borrowing from nearby states through anharmonic couplings, an effect explained qualitatively by VSCF and quantitatively by VCI, but not by the harmonic approximation. The X˜B22 photoelectron band of H2CO is less accurately reproduced by this method, likely because of the inability of CCSD(T)/cc-pVTZ to describe the potential energy surface of open-shell H2CO+ with the same high accuracy as in H2O+.

  20. Adiabatic coherent control in the anharmonic ion trap: Proposal for the vibrational two-qubit system

    International Nuclear Information System (INIS)

    A method for encoding a multiqubit system into the quantized motional states of ion string in an anharmonic linear trap is proposed. Control over this system is achieved by applying oscillatory electric fields (rf) shaped optimally for desired state-to-state transitions. Anharmonicity of the vibrational spectrum of the system plays a key role in this approach to the control and quantum computation, since it allows resolving different state-to-state transitions and addressing them selectively. The anharmonic trap architecture proposed earlier [Phys. Rev. A 83, 022305 (2011)] is explored here and the optimal control theory is used to derive pulses for a set of universal quantum gates. An accurate choice of pulse parameters allows deriving gates that are both accurate and simple. A practical realization of this approach seems to be within the reach of today's technology.

  1. 2008 Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Philip J. Reid

    2009-09-21

    The conference focuses on using vibrational spectroscopy to probe structure and dynamics of molecules in gases, liquids, and interfaces. The goal is to bring together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of systems.

  2. Anharmonic thermal vibrations of be metal found in the MEM nuclear density map

    International Nuclear Information System (INIS)

    A direct observation of the thermal vibrations of Be metal was performed by the Maximum Entropy Method (MEM) using neutron single crystal data. In the previous study, the existence of the small but significant cubic anharmonicity of Be has been found by the conventional least squares refinement of the observed structure factors [Larsen, Lehmann and Merisalo (1980) Acta Cryst. A36, 159-163]. In the present study, the same data were used for the MEM analysis which are comprised of 48 reflections up to sinθ/λ = 1.41A-1 in order to obtain the high resolution nuclear density of Be without using any thermal vibrational model. It was directly visible in the MEM map that not only the cubic terms but also quartic anharmonicities exist in the thermal vibrations of Be nuclei. In order to evaluate thermal parameters of Be including anharmonic terms quantitatively, the least squares refinement of the effective one-particle potential (OPP) parameters up to quartic term was carried out by using the MEM nuclear densities around atomic sites as the data set to be fitted. It was found that the present treatment has a great advantage to decide the most appropriate model of OPP by visually comparing the model with MEM density map. As a result of the least squares refinement, the anharmonic thermal parameters are obtained as α33 = -0.340(5)[eV/A3], α40 = 0, β20 = 9.89(1)[eV/A4] and γ00 = 0. No other anharmonic term was significant. (author)

  3. On the benefits of localized modes in anharmonic vibrational calculations for small molecules.

    Science.gov (United States)

    Panek, Paweł T; Jacob, Christoph R

    2016-04-28

    Anharmonic vibrational calculations can already be computationally demanding for relatively small molecules. The main bottlenecks lie in the construction of the potential energy surface and in the size of the excitation space in the vibrational configuration interaction (VCI) calculations. To address these challenges, we use localized-mode coordinates to construct potential energy surfaces and perform vibrational self-consistent field and L-VCI calculations [P. T. Panek and C. R. Jacob, ChemPhysChem 15, 3365 (2014)] for all vibrational modes of two prototypical test cases, the ethene and furan molecules. We find that the mutual coupling between modes is reduced when switching from normal-mode coordinates to localized-mode coordinates. When using such localized-mode coordinates, we observe a faster convergence of the n-mode expansion of the potential energy surface. This makes it possible to neglect higher-order contributions in the n-mode expansion of the potential energy surface or to approximate higher-order contributions in hybrid potential energy surfaces, which reduced the computational effort for the construction of the anharmonic potential energy surface significantly. Moreover, we find that when using localized-mode coordinates, the convergence with respect to the VCI excitation space proceeds more smoothly and that the error at low orders is reduced significantly. This makes it possible to devise low-cost models for obtaining a first approximation of anharmonic corrections. This demonstrates that the use of localized-mode coordinates can be beneficial already in anharmonic vibrational calculations of small molecules and provides a possible avenue for enabling such accurate calculations also for larger molecules. PMID:27131535

  4. On the benefits of localized modes in anharmonic vibrational calculations for small molecules

    Science.gov (United States)

    Panek, Paweł T.; Jacob, Christoph R.

    2016-04-01

    Anharmonic vibrational calculations can already be computationally demanding for relatively small molecules. The main bottlenecks lie in the construction of the potential energy surface and in the size of the excitation space in the vibrational configuration interaction (VCI) calculations. To address these challenges, we use localized-mode coordinates to construct potential energy surfaces and perform vibrational self-consistent field and L-VCI calculations [P. T. Panek and C. R. Jacob, ChemPhysChem 15, 3365 (2014)] for all vibrational modes of two prototypical test cases, the ethene and furan molecules. We find that the mutual coupling between modes is reduced when switching from normal-mode coordinates to localized-mode coordinates. When using such localized-mode coordinates, we observe a faster convergence of the n-mode expansion of the potential energy surface. This makes it possible to neglect higher-order contributions in the n-mode expansion of the potential energy surface or to approximate higher-order contributions in hybrid potential energy surfaces, which reduced the computational effort for the construction of the anharmonic potential energy surface significantly. Moreover, we find that when using localized-mode coordinates, the convergence with respect to the VCI excitation space proceeds more smoothly and that the error at low orders is reduced significantly. This makes it possible to devise low-cost models for obtaining a first approximation of anharmonic corrections. This demonstrates that the use of localized-mode coordinates can be beneficial already in anharmonic vibrational calculations of small molecules and provides a possible avenue for enabling such accurate calculations also for larger molecules.

  5. Vibrational Spectroscopy of Methyl benzoate

    CERN Document Server

    Maiti, Kiran Sankar

    2014-01-01

    Methyl benzoate (MB) is studied as a model compound for the development of new IR pulse schemes with possible applicability to biomolecules. Anharmonic vibrational modes of MB are calculated on different level (MP2, SCS, CCSD(T) with varying basis sets) ab-initio PESs using the vibrational self-consistent field (VSCF) method and its correlation corrected extensions. Dual level schemes, combining different quantum chemical methods for diagonal and coupling potentials, are systematically studied and applied successfully to reduce the computational cost. Isotopic substitution of {\\beta}-hydrogen by deuterium is studied to obtain a better understanding of the molecular vibrational coupling topology.

  6. Transient Two-Dimensional Infrared Spectroscopy in a Vibrational Ladder.

    Science.gov (United States)

    Kemlin, Vincent; Bonvalet, Adeline; Daniault, Louis; Joffre, Manuel

    2016-09-01

    We report on transient 2D Fourier transform infrared spectroscopy (2DIR) after vibrational ladder climbing induced in the CO-moiety longitudinal stretch of carboxyhemoglobin. The population distribution, spreading up to seven vibrational levels, results in a nonequilibrium 2DIR spectrum evidencing a large number of peaks that can be easily attributed to individual transitions thanks to the anharmonicity of the vibrational potential. We discuss the physical origin of the observed peaks as well as the qualitative behavior of the subsequent dynamics governed by population relaxation in the vibrational ladder. PMID:27508408

  7. Anharmonic contributions to the inversion vibration in 2-aminopyrimidine

    Science.gov (United States)

    McCarthy, W. J.; Lapinski, L.; Nowak, M. J.; Adamowicz, L.

    1995-07-01

    The out-of-plane vibrations of the amino group in 2-aminopyrimidine have large amplitudes, and cannot be properly described within the harmonic approximation. The normal mode analysis carried out at this level of approximation at the restricted Hartree-Fock level and at the second-order Møller-Plesset perturbation theory level failed to match the experimental transition frequency of ν≊200 cm-1 of the inversion vibration in this compound. In an effort to better understand this vibration motion, we went beyond the harmonic approximation. The inversion vibration was treated as being uncoupled from all other nuclear degrees of freedom. An internal coordinate (ω) was chosen whose displacement mimicked the out-of-plane distortion of the amino group during the inversion vibration. Electronic energy was calculated at the second-order Møller-Plesset perturbation theory level at selected values of ω to form a double-well curve describing a model potential within which the nuclei move during the vibration. This potential was incorporated into a one-dimensional Hamiltonian, and vibrational energy expectation values were variationally determined by utilizing the harmonic wavefunctions as the basis set. Two sets of calculations were performed: one in which the mirror plane of symmetry was preserved throughout the vibrational deformation limiting the internal coordinates to 17, and another in which the symmetry was unconstrained permitting description by 3N-6=30 internal coordinates. These calculations resulted in prediction of the v=0→v=1 transition energy of ν=130.1 cm-1 and ν=206.7 cm-1, respectively, reasonably matching the experimental value of ≊200 cm-1.

  8. Anharmonic contributions to the inversion vibration in 2-aminopyrimidine

    Energy Technology Data Exchange (ETDEWEB)

    McCarthy, W.J. [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States); Lapinski, L.; Nowak, M.J. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw (Poland); Adamowicz, L. [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States)

    1995-07-08

    The out-of-plane vibrations of the amino group in 2-aminopyrimidine have large amplitudes, and cannot be properly described within the harmonic approximation. The normal mode analysis carried out at this level of approximation at the restricted Hartree--Fock level and at the second-order Moller--Plesset perturbation theory level failed to match the experimental transition frequency of {nu}{approx}200 cm{sup {minus}1} of the inversion vibration in this compound. In an effort to better understand this vibration motion, we went beyond the harmonic approximation. The inversion vibration was treated as being uncoupled from all other nuclear degrees of freedom. An internal coordinate ({omega}) was chosen whose displacement mimicked the out-of-plane distortion of the amino group during the inversion vibration. Electronic energy was calculated at the second-order Moller--Plesset perturbation theory level at selected values of {omega} to form a double-well curve describing a model potential within which the nuclei move during the vibration. This potential was incorporated into a one-dimensional Hamiltonian, and vibrational energy expectation values were variationally determined by utilizing the harmonic wavefunctions as the basis set. Two sets of calculations were performed: one in which the mirror plane of symmetry was preserved throughout the vibrational deformation limiting the internal coordinates to 17, and another in which the symmetry was unconstrained permitting description by 3{ital N}{minus}6=30 internal coordinates. These calculations resulted in prediction of the {ital v}=0{r_arrow}{ital v}=1 transition energy of {nu}=130.1 cm{sup {minus}1} and {nu}=206.7 cm{sup {minus}1}, respectively, reasonably matching the experimental value of {approx}200 cm{sup {minus}1}. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  9. Alcohol dimers - how much diagonal OH anharmonicity?

    OpenAIRE

    Kollipost, Franz; Papendorf, Kim; Lee, Yu-Fang; Lee, Yuan-Pern; Suhm, Martin A

    2014-01-01

    The OH bond of methanol, ethanol and t-butyl alcohol becomes more anharmonic upon hydrogen bonding and the infrared intensity ratio between the overtone and the fundamental transition of the bridging OH stretching mode decreases drastically. FTIR spectroscopy of supersonic slit jet expansions allows to quantify these effects for isolated alcohol dimers, enabling a direct comparison to anharmonic vibrational predictions. The diagonal anharmonicity increase amounts to 15-18%, growing with incre...

  10. Quantum-chemical ab initio investigation of the vibrational spectrum of halon 1113 and its anharmonic force field: A joint experimental and computational approach

    International Nuclear Information System (INIS)

    Highlights: ► Halon 1113, potential ozone depleting gas, vibrational eigenstates and intensity. ► FT-IR experimental and theoretical study of chlorotrifluoroethene. ► Ab initio calculations at MP2 and CCSD(T) levels with cc-pVTZ and ANO basis sets. ► Equilibrium geometry and harmonic force field. ► Full CCSD(T) and hybrid anharmonic force fields. - Abstract: Halon 1113 (chlorotrifluoroethene), used in the synthesis of fluorocarbon-based polymers, has been recently detected in the atmosphere and it is a potential source of chlorine atoms. In this work, the vibrational properties of chlorotrifluoroethene are studied in the 125–5000 cm−1 region by coupling Fourier-transform infrared spectroscopy and high-level ab initio calculations. The vibrational analysis is performed over the whole spectral range and band intensities are obtained in the range 400–3100 cm−1. Ab initio calculations of the anharmonic force field are performed at the coupled cluster level of theory employing either cc-pVTZ or ANO basis sets. Vibration perturbation theory is applied to obtain spectroscopic parameters from the computed anharmonic force fields. The present results provide a solid interpretation of chlorotrifluoroethene vibrational spectrum, and they represent a significant reference for future studies on this molecule, being also the first published data on absorption cross sections and ab initio calculations.

  11. High-resolution IR absorption spectroscopy of polycyclic aromatic hydrocarbons: the realm of anharmonicity

    CERN Document Server

    Maltseva, Elena; Candian, Alessandra; Mackie, Cameron J; Huang, Xinchuan; Lee, Timothy J; Tielens, Alexander G G M; Oomens, Jos; Buma, Wybren Jan

    2015-01-01

    We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micron CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (~4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilises intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination ...

  12. Anharmonic exciton dynamics and energy dissipation in liquid water from two-dimensional infrared spectroscopy.

    Science.gov (United States)

    De Marco, Luigi; Fournier, Joseph A; Thämer, Martin; Carpenter, William; Tokmakoff, Andrei

    2016-09-01

    Water's extended hydrogen-bond network results in rich and complex dynamics on the sub-picosecond time scale. In this paper, we present a comprehensive analysis of the two-dimensional infrared (2D IR) spectrum of O-H stretching vibrations in liquid H2O and their interactions with bending and intermolecular vibrations. By exploring the dependence of the spectrum on waiting time, temperature, and laser polarization, we refine our molecular picture of water's complex ultrafast dynamics. The spectral evolution following excitation of the O-H stretching resonance reveals vibrational dynamics on the 50-300 fs time scale that are dominated by intermolecular delocalization. These O-H stretch excitons are a result of the anharmonicity of the nuclear potential energy surface that arises from the hydrogen-bonding interaction. The extent of O-H stretching excitons is characterized through 2D depolarization measurements that show spectrally dependent delocalization in agreement with theoretical predictions. Furthermore, we show that these dynamics are insensitive to temperature, indicating that the exciton dynamics alone set the important time scales in the system. Finally, we study the evolution of the O-H stretching mode, which shows highly non-adiabatic dynamics suggestive of vibrational conical intersections. We argue that the so-called heating, commonly observed within ∼1 ps in nonlinear IR spectroscopy of water, is a nonequilibrium state better described by a kinetic temperature rather than a Boltzmann distribution. Our conclusions imply that the collective nature of water vibrations should be considered in describing aqueous solvation. PMID:27608998

  13. Anharmonic apical oxygen vibration in high-Tc superconductors

    International Nuclear Information System (INIS)

    Using time-independent perturbation theory, a theoretical calculation has been performed for the transition temperatures for various high-Tc oxide compounds. It has been assumed that, three electrons are responsible for the superconducting current. Whereas two of these electrons form an exotic bound pair, the third electron causes perturbation H' = βx3 + γx4 with respect to apical oxygen vibrations. From the calculations, the transition temperatures are found to be realistic and comparable with experimental results. (author)

  14. Structure, Anharmonic Vibrational Frequencies, and Intensities of NNHNN(+).

    Science.gov (United States)

    Yu, Qi; Bowman, Joel M; Fortenberry, Ryan C; Mancini, John S; Lee, Timothy J; Crawford, T Daniel; Klemperer, William; Francisco, Joseph S

    2015-11-25

    A semiglobal potential energy surface (PES) and quartic force field (QFF) based on fitting high-level electronic structure energies are presented to describe the structures and spectroscopic properties of NNHNN(+). The equilibrium structure of NNHNN(+) is linear with the proton equidistant between the two nitrogen groups and thus of D(∞h) symmetry. Vibrational second-order perturbation theory (VPT2) calculations based on the QFF fails to describe the proton "rattle" motion, i.e., the antisymmetric proton stretch, due to the very flat nature of PES around the global minimum but performs properly for other modes with sharper potential wells. Vibrational self-consistent field/virtual state configuration interaction (VSCF/VCI) calculations using a version of MULTIMODE without angular momentum terms successfully describe this motion and predict the fundamental to be at 759 cm(-1). This is in good agreement with the value of 746 cm(-1) from a fixed-node diffusion Monte Carlo calculation and the experimental Ar-tagged result of 743 cm(-1). Other VSCF/VCI energies are in good agreement with other experimentally reported ones. Both double-harmonic intensity and rigorous MULTIMODE intensity calculations show the proton-transfer fundamental has strong intensity. PMID:26529262

  15. High-Resolution IR Absorption Spectroscopy of Polycyclic Aromatic Hydrocarbons: The Realm of Anharmonicity

    Science.gov (United States)

    Maltseva, Elena; Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Huang, Xinchuan; Lee, Timothy J.; Tielens, Alexander G. G. M.; Oomens, Jos; Buma, Wybren Jan

    2016-01-01

    We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micrometers CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold ((is) approximately 4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main modes that fall within 0.5% of the experimental frequencies. The implications for the Aromatic Infrared Bands, specifically the 3-m band are discussed.

  16. Vibrational spectroscopy at electrified interfaces

    CERN Document Server

    Wieckowski, Andrzej; Braunschweig, Björn

    2013-01-01

    Reviews the latest theory, techniques, and applications Surface vibrational spectroscopy techniques probe the structure and composition of interfaces at the molecular level. Their versatility, coupled with their non-destructive nature, enables in-situ measurements of operating devices and the monitoring of interface-controlled processes under reactive conditions. Vibrational Spectroscopy at Electrified Interfaces explores new and emerging applications of Raman, infrared, and non-linear optical spectroscopy for the study of charged interfaces. The book draws from hu

  17. A study of anharmonic al and nonlinear behaviours of vibrations of atomic nuclei

    International Nuclear Information System (INIS)

    Double Giant Resonances, vibrational states in which a Giant Resonance is excited on top of another Giant Resonance, have been in the last years the object of many theories and studies. Whereas the measured energies and widths of these states agree with a theoretical predictions, the measured excitation cross sections on the other hand are almost always larger than the calculated ones. The standard theoretical approaches are based both on a harmonic approximation for the collective motion on the nucleus and on its linear response to an external field. In this work the influence of anharmonicities and non-linearities in the external field on the excitation of Double Giant Resonances are studied. First, an oscillator model and an extension of the Lipkin-Meshkow-Glick model are used to study the effects of anharmonicities and non-linearities on the excitation probabilities. The results show that these terms can influence the excitation probability of the second excited state in a significant way. Secondly, these exactly soluble schematic models are used to study some of the approximations made in microscopic calculations based on boson expansion methods and also some aspects on the time-dependent mean field approach. Finally, a microscopic calculation of the Coulomb excitation cross sections of Double Giant Resonances is presented for several nuclei. It is found that, for 208 Pb, the inclusion of anharmonicities and non-linearities and the consideration of many states that play a role in the excitation process give a satisfactory agreement between calculated and observed cross sections. (author)

  18. On the benefits of localized modes in anharmonic vibrational calculations for small molecules

    CERN Document Server

    Panek, Pawel T

    2016-01-01

    Anharmonic vibrational calculations can already be computationally demanding for relatively small molecules. The main bottlenecks lie in the construction of the potential energy surface and in the size of the excitation space in the vibrational configuration interaction (VCI) calculations. To address these challanges, we use localized-mode coordinates to construct potential energy surfaces and perform vibrational self-consistent field (L-VSCF) and L-VCI calculations [P. T. Panek, Ch. R. Jacob, ChemPhysChem 15, 3365 (2014)] for all vibrational modes of two prototypical test cases, the ethene and furan molecules. We find that the mutual coupling between modes is reduced when switching from normal-mode coordinates to localized-mode coordinates. When using such localized-mode coordinates, we observe a faster convergence of the $n$-mode expansion of the potential energy surface. This makes it possible to neglect higher-order contributions in the $n$-mode expansion of the potential energy surface or to approximate ...

  19. Vibrational spectroscopy of proteins

    International Nuclear Information System (INIS)

    Two important steps for the development of a biosensor are the immobilization of the biological component (e.g. protein) on a surface and the enhancement of the signal to improve the sensitivity of detection. To address these subjects, the present work describes Fourier transform infrared (FTIR) investigations of several proteins bound to the surface of an attenuated total reflection (ATR) crystal. Furthermore, new nanostructured surfaces for signal enhancement were developed for use in FTIR microscopy. The mitochondrial redox-protein cytochrome c oxidase (CcO) was incorporated into a protein-tethered bilayer lipid membrane (ptBLM) on an ATR crystal featuring a roughened two-layer gold surface for signal enhancement. Electrochemical excitation by periodic potential pulses at different modulation frequencies was followed by time-resolved FTIR spectroscopy. Phase sensitive detection was used for deconvolution of the IR spectra into vibrational components. A model based on protonation-dependent chemical reaction kinetics could be fitted to the time evolution of IR bands attributed to several different redox centers of the CcO. Further investigations involved the odorant binding protein 14 (OBP14) of the honey bee (Apis mellifera), which was studied using ATR-FTIR spectroscopy and circular dichroism. OBP14 was found to be thermally stable up to 45 °C, thus permitting the potential application of this protein for the fabrication of biosensors. Thermal denaturation measurements showed that odorant binding increases the thermal stability of the OBP-odorant complex. In another project, plasmonic nanostructures were fabricated that enhance the absorbance in FTIR microscopy measurements. The nanostructures are composed of an array of round-shaped insulator and gold discs on top of a continuous gold layer. Enhancement factors of up to ⁓125 could be observed with self-assembled monolayers of dodecanethiol molecules immobilized on the gold surface (author)

  20. Comparison of the local binding motifs in the imidazolium-based ionic liquids [EMIM][BF4] and [EMMIM][BF4] through cryogenic ion vibrational predissociation spectroscopy: Unraveling the roles of anharmonicity and intermolecular interactions

    International Nuclear Information System (INIS)

    We clarify the role of the critical imidazolium C(2)H position (the central C between N atoms in the heterocycle) in the assembly motif of the [EMIM][BF4] ionic liquid by analyzing the vibrational spectra of the bare EMIM+ ion as well as that of the cationic [EMIM]2[BF4]+ (EMIM+ = 1-ethyl-3-methylimidazolium, C6H11N2+) cluster. Vibrational spectra of the cold, mass-selected ions are obtained using cryogenic ion vibrational predissociation of weakly bound D2 molecules formed in a 10 K ion trap. The C(2)H behavior is isolated by following the evolution of key vibrational features when the C(2) hydrogen, the proposed binding location of the anion to the imidazolium ring, is replaced by either deuterium or a methyl group (i.e., in the EMMIM+ analogue). Strong features in the ring CH stretching region of the bare ion are traced to Fermi resonances with overtones of lower frequency modes. Upon incorporation into the EMIM+ ⋅ ⋅ ⋅ BF4− ⋅ ⋅ ⋅ EMIM+ ternary complex, the C(2)H oscillator strength is dramatically increased, accounting for the much more complicated patterns derived from the EMIM+ ring CH stretches in the light isotopomer, which are strongly suppressed in the deuterated analogue. Further changes in the spectra that occur when the C(2)H is replaced by a methyl group are consistent with BF4− attachment directly to the imidazolium ring in an arrangement that maximizes the electrostatic interaction between the molecular ions

  1. Numerical calculation of vibrational transition probability for the forced morse oscillator by use of the anharmonic boson operators

    International Nuclear Information System (INIS)

    The vibrational transition probability expressions for the forced Morse oscillator have been derived using the commutation relations of the anharmonic Boson operators. The formulation is based on the collinear collision model with the exponential repulsive potential in the framework of semiclassical collision dynamics. The sample calculation results for H2 + He collision system, where the anharmonicity is large, are in excellent agreement with those from an exact, numerical quantum mechanical study by Clark and Dickinson, using the reactance matrix. Our results,however, are markedly different from those of Ree, Kim, and Shin's in which they approximate the commutation operator Io as unity, the harmonic oscillator limit. We have concluded that the quantum number dependence in Io must be retained to get accurate vibrational transition probabilities for the Morse oscillator

  2. Ultrafast infrared vibrational spectroscopy

    CERN Document Server

    Fayer, Michael D

    2013-01-01

    The past ten years or so have seen the introduction of multidimensional methods into infrared and optical spectroscopy. The technology of multidimensional spectroscopy is developing rapidly and its applications are spreading to biology and materials science. Edited by a recognized leader in the field and with contributions from top researchers, including experimentalists and theoreticians, this book presents the latest research methods and results and will serve as an excellent resource for other researchers.

  3. Anharmonic IR and Raman spectra and electronic and vibrational (hyper)polarizabilities of barbituric, 2-thiobarbituric and 2-selenobarbituric acids

    Science.gov (United States)

    Alparone, Andrea

    2014-01-01

    Infrared, Raman and electronic absorption spectra, electronic and vibrational (hyper)polarizabilities, of barbituric, 2-thiobarbituric and 2-selenobarbituric acids were studied in gas using ab initio and density functional theory levels. The vibrational spectra were computed using harmonic and anharmonic methods. Anharmonic contributions improve the agreement between calculated and available experimental wavenumbers, especially in the highest-energy spectral region (wavenumbers >1700 cm-1). Vibrational and electronic transitions potentially useful to identify the investigated compounds were explored. The electronic and vibrational hyperpolarizabilities for the IDRI nonlinear optical (NLO) process at the λ value of 790 nm were computed. Supported by spectroscopic results, electronic and vibrational polarizabilities and second-order hyperpolarizabilities increase progressively in the order barbituric acid acid acid. The seleno-derivative is predicted to be ca. three/four times more hyperpolarizable than the barbituric acid. The Se → O or Se → S substitutions can be practical strategies to enhances the NLO properties of barbituric and thiobarbituric acid-based materials.

  4. Thermoelectric materials: The anharmonicity blacksmith

    Science.gov (United States)

    Heremans, Joseph P.

    2015-12-01

    Anharmonicity is a property of lattice vibrations governing how they interact and how well they conduct heat. Experiments on tin selenide, the most efficient thermoelectric material known, now provide a link between anharmonicity and electronic orbitals.

  5. Low-temperature vibrational anharmonicity of 151Eu in EuBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    The angular averaged mean-square displacement of 151Eu in EuBa2Cu3O7-δ was measured as a function of temperature by Moessbauer spectroscopy using the absorption area method. Large low-temperature anharmonicity was found; i.e. the adiabatic potential experienced by Eu3+ ions presents a 'wine-bottle bottom' shape with a flat region about 0.1 AA wide. Comparisons with other experimental results are made. (author)

  6. TIME-RESOLVED VIBRATIONAL SPECTROSCOPY

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-05-14

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

  7. Temperature dependence of thermal vibrations in cubic ZnS, a comparison of anharmonic models

    International Nuclear Information System (INIS)

    Accurate integrated intensities for the Bragg reflection of neutrons from a ZnS single crystal have been measured at temperatures between 285 and 1173 K. After correction for thermal diffuse scattering and extinction effects the data were interpreted with different models that allow anharmonic contributions to the temperature factor. Both the cumulant expansion and the one-particle potential (OPP) model with quasi-harmonic temperature dependence describe the data satisfactorily, although the Gruneisen parameter obtained in the OPP analysis differs greatly from the value calculated from known thermodynamic quantities. Predictions based on Matsubara's anharmonic formalism are not in accord with the behavior observed at the highest temperatures

  8. The far-infrared spectrum of azulene and isoquinoline and supporting anharmonic density functional theory calculations to high resolution spectroscopy of polycyclic aromatic hydrocarbons and derivatives

    Science.gov (United States)

    Goubet, Manuel; Pirali, Olivier

    2014-01-01

    In the laboratory, the acquisition and analysis of the rotationally resolved spectra of large molecular systems remain challenging. We report in this paper the rotational analysis of the ν30-GS band of azulene and the ν41-GS band of isoquinoline recorded with synchrotron-based Fourier transform absorption spectroscopy in the far-IR. As a support to rotational analyses, we employed a method based on standard density functional theory calculations performed at the anharmonic level which accurately reproduced the rotational constants of 28 vibrational states of 16 Polycyclic Aromatic Hydrocarbons (PAHs) and aza-derivatives. This method appears as an invaluable support for the spectral assignment of the very congested rotational structures of the infrared bands of PAH species and should be very helpful in the active search of these molecules in space through their pure rotational or rovibrational spectra.

  9. Systematic studies of molecular vibrational anharmonicity and vibration-rotation interaction by self-consistent-field higher derivative methods: Applications to asymmetric and symmetric top and linear polyatomic molecules

    International Nuclear Information System (INIS)

    Inclusion of the anharmonicity normal mode vibrations [i.e., the third and fourth (and higher) derivatives of a molecular Born-Oppenheimer potential energy surface] is necessary in order to theoretically reproduce experimental fundamental vibrational frequencies of a molecule. Although ab initio determinations of harmonic vibrational frequencies may give errors of only a few percent by the inclusion of electron correlation within a large basis set for small molecules, in general, molecular fundamental vibrational frequencies are more often available from high resolution vibration-rotation spectra. Recently developed analytic third derivatives methods for self-consistent-field (SCF) wavefunctions have made it possible to examine with previously unavailable accuracy and computational efficiency the anharmonic force fields of small molecules

  10. Static and dynamic properties of Rochelle salt considering asymmetric double well potential and anharmonic lattice vibrations

    International Nuclear Information System (INIS)

    The interesting features of phase transition in Rochelle Salt (RS) or C4H4O6NaK.4(H2O) i.e. the appearance of two Curie points Tsub(c1) (255 K) and Tsub(c2) (297 K) and large isotope effect on Tsub(c) are studied. On deuteration the lower Curie point shifts towards lower temperature and the upper Curie point towards the higher temperature, showing evidently the important role played by the hydrogen atoms in the ferroelectric behaviour of RS. A conclusion has finally been drawn from the present and previous investigations that both proton-lattice and phonon-phonon interactions play a vital role in the phase transition in hydrogen bonded ferroelectrics including KDP family and the present Rochelle Salt group. An estimation of the anharmonic contribution in the dynamic and static properties has also been found out for these crystals. (K.B.)

  11. Anharmonic phonons in few-layer MoS2: Raman spectroscopy of ultralow energy compression and shear modes

    Science.gov (United States)

    Boukhicha, Mohamed; Calandra, Matteo; Measson, Marie-Aude; Lancry, Ophelie; Shukla, Abhay

    2013-05-01

    Molybdenum disulfide (MoS2) is a promising material for making two-dimensional crystals and flexible electronic and optoelectronic devices at the nanoscale. MoS2 flakes can show high mobilities and have even been integrated in nanocircuits. A fundamental requirement for such use is efficient thermal transport. Electronic transport generates heat which needs to be evacuated, more crucially so in nanostructures. Anharmonic phonon-phonon scattering is the dominant intrinsic limitation to thermal transport in insulators. Here, using appropriate samples, ultralow energy Raman spectroscopy and first-principles calculations, we provide a full experimental and theoretical description of compression and shear modes of few-layer (FL) MoS2. We demonstrate that the compression modes are strongly anharmonic with a marked enhancement of phonon-phonon scattering as the number of layers is reduced, most likely a general feature of nanolayered materials with weak interlayer coupling.

  12. Vibrational spectroscopy of water interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Du, Q.

    1994-12-01

    The second order nonlinear optical processes of second harmonic generation and sum frequency generation are powerful and versatile tools for studying all kinds of surfaces. They possess unusual surface sensitivity due to the symmetry properties of the second order nonlinear susceptibility. The technique of infrared-visible sum frequency generation (SFG) is particularly attractive because it offers a viable way to do vibrational spectroscopy on any surfaces accessible to light with submonolayer sensitivity. In this thesis, the author applies SFG to study a number of important water interfaces. At the air/water interface, hydrophobic solid/water and liquid/water interfaces, it was found that approximately 25% of surface water molecules have one of their hydrogen pointing away from the liquid water. The large number of unsatisfied hydrogen bonds contributes significantly to the large interfacial energy of the hydrophobic surfaces. At the hydrophilic fused quartz/water interface and a fatty acid monolayer covered water surface, the structure and orientation of surface water molecules are controlled by the hydrogen bonding of water molecules with the surface OH groups and the electrostatic interaction with the surface field from the ionization of surface groups. A change of pH value in the bulk water can significantly change the relative importance of the two interactions and cause a drastic change in orientation of the surface water molecules. SFG has also been applied to study the tribological response of some model lubricant films. Monolayers of Langmuir-Blodgett films were found to disorder orientationaly under mildly high pressure and recover promptly upon removal of the applied pressure.

  13. Probing vibrational anisotropy with nuclear resonance vibrational spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Pavlik, J. W.; Barabanschikov, A.; Oliver, A. G.; Alp, E. E.; Sturhahn, W.; Zhao, J.; Sage, J. T.; Scheidt, W. R. (X-Ray Science Division); (Univ. of Notre Dame); (Northeastern Univ.)

    2010-06-14

    A NRVS single-crystal study (NRVS=nuclear resonance vibrational spectroscopy) has provided detailed information on the in-plane modes of nitrosyl iron porphyrinate [Fe(oep)(NO)] (see picture; oep=octaethylporphyrin). The axial nitrosyl ligand controls the direction of the in-plane iron motion.

  14. Unexpected red shift of C-H vibrational band of Methyl benzoate

    CERN Document Server

    Maiti, Kiran Sankar; Scheurer, Christoph

    2016-01-01

    The C-H vibrational bands become more and more important in the structural determination of biological molecules with the development of CARS microscopy and 2DIR spectroscopy. Due to the congested pattern, near degeneracy, and strong anharmonicity of the C-H stretch vibrations, assignment of the C-H vibrational bands are often misleading. Anharmonic vibrational spectra calculation with multidimensional potential energy surface interprets the C-H vibrational spectra more accurately. In this article we have presented the importance of multidimensional potential energy surface in anharmonic vibrational spectra calculation and discuss the unexpected red shift of C-H vibrational band of Methyl benzoate.

  15. Vibrational spectroscopy of polar molecules with superradiance

    Science.gov (United States)

    Lin, Guin-Dar; Yelin, Susanne F.

    2013-07-01

    We investigate cooperative phenomena and superradiance for vibrational transitions in polar molecule spectroscopy of high optical-depth samples. Such cooperativity comes from the build-up of inter-particle coherence through dipole-dipole interactions and leads to speed-up of decay processes. We compare our calculation to recent work and find very good agreement, suggesting that superradiant effects need to be taken into account in a wide variety of ultracold molecule experiments, including vibrational and rotational states.

  16. Two-dimensional vibrational-electronic spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Courtney, Trevor L.; Fox, Zachary W.; Slenkamp, Karla M.; Khalil, Munira, E-mail: mkhalil@uw.edu [Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 (United States)

    2015-10-21

    Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE) to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (ν{sub CN}) and either a ligand-to-metal charge transfer transition ([Fe{sup III}(CN){sub 6}]{sup 3−} dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN){sub 5}Fe{sup II}CNRu{sup III}(NH{sub 3}){sub 5}]{sup −} dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific ν{sub CN} modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a

  17. Two-dimensional vibrational-electronic spectroscopy

    International Nuclear Information System (INIS)

    Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE) to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (νCN) and either a ligand-to-metal charge transfer transition ([FeIII(CN)6]3− dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN)5FeIICNRuIII(NH3)5]− dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific νCN modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a wide range of complex molecular, material, and biological systems

  18. Anharmonicities in vibrational spectra of deformed nuclei discussed in a simple model

    International Nuclear Information System (INIS)

    Some microscopic treatments of the nuclear vibrational spectra are analyzed in terms of a model allowing an exact solution for a many-body nucleon system interacting via pairing plus quadrupole force. The multi-phonon approach -exact diagonalization in the restricted space of 1, 2, 3, .. collective phonons- appears satisfactory for the few lowest lying vibrational Ksup(π)=0+ states in deformed nuclei. The non conservation of the number of particles and coupling between collective and non collective states seem to be main sources of the discrepancies, that occur for the higher states. On the other hand, the lowest order contributions suggested by nuclear field theory lead to serious disagreement as compared with the exact solutions

  19. Vibrational Spectroscopy of Chromatographic Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jeanne E. Pemberton

    2011-03-10

    Chromatographic separations play a central role in DOE-supported fundamental research related to energy, biological systems, the environment, and nuclear science. The overall portfolio of research activities in the Separations and Analysis Program within the DOE Office of Basic Energy Sciences includes support for activities designed to develop a molecular-level understanding of the chemical processes that underlie separations for both large-scale and analytical-scale purposes. The research effort funded by this grant award was a continuation of DOE-supported research to develop vibrational spectroscopic methods to characterize the interfacial details of separations processes at a molecular level.

  20. Vibrational Spectroscopy on Trapped Cold Molecular Ions

    Science.gov (United States)

    Khanyile, Ncamiso B.; Brown, Kenneth R.

    2014-06-01

    We perform vibrational spectroscopy on the V0←10 overtone of a trapped and sympathetically cooled CaH+ molecular ion using a resonance enhanced two photon dissociation scheme. Our experiments are motivated by theoretical work that proposes comparing the vibrational overtones of CaH^+ with electronic transitions in atoms to detect possible time variation of in the mass ratio of the proton to electron. Due to the nonexistence of experimental data of the transition, we start the search with a broadband femtosecond Ti:Saph laser guided by theoretical calculations. Once the vibrational transition has been identified, we will move to CW lasers to perform rotationally resolved spectroscopy. M. Kajita and Y. Moriwaki, J. Phys. B. At. Mol. Opt.Phys., 42,154022(2009) Private communication

  1. Vibrational spectroscopy of polar molecules with superradiance

    CERN Document Server

    Lin, Guin-Dar

    2013-01-01

    We investigate cooperative phenomena and superradiance for vibrational transitions in polar molecule spectroscopy when a high optical-depth (OD) sample is studied. Such cooperativity comes from the build-up of inter-particle coherence through dipole-dipole interactions and leads to the speed-up of decay process. We compare our calculation to recent work [Deiglmayr et al., Eur. Phys. J. D 65, 99 (2011)] and find very good agreement, suggesting that superradiant effects need to be included in a wide variety of ultracold molecule setups including vibrational and rotational states.

  2. The vibrational spectrum of the water dimer: Comparison between anharmonic ab initio calculations and neon matrix infrared data between 14,000 and 90 cm-1

    International Nuclear Information System (INIS)

    Graphical abstract: The spectrum of the water dimer trapped in neon has been recorded and analysed up to 14,000 cm-1. Highlights: → Observation of the vibrational spectrum of the water dimer from the far infrared to the visible. → Assignment based on 18O/16O shift and on approximate values of anharmonicity coefficients. → Calculations in the framework of the second-order perturbation - resonance theory. - Abstract: The infrared spectrum of the water dimer trapped in solid neon has been recorded up to the visible by improving significantly the experimental technique used in a previous paper [Y. Bouteiller, J.P. Perchard, Chem. Phys. 305 (2004) 1]. A total of 22 intramolecular transitions of the proton donor (PD) and 23 of the proton acceptor (PA) are now identified and assigned on the basis of 16O/18O isotopic shifts and of realistic anharmonicity corrections. From an ab initio determination of the potential energy a perturbation-resonance treatment has been carried out for each polyad Pn, n = 2-8. Finally combinations of intra + intermolecular transitions were identified and assigned on the basis of calculated anharmonicity coefficients.

  3. Vibrational spectroscopy of polar molecules with superradiance

    OpenAIRE

    Lin, Guin-Dar; Yelin, Susanne F.

    2013-01-01

    We investigate cooperative phenomena and superradiance for vibrational transitions in polar molecule spectroscopy when a high optical-depth (OD) sample is studied. Such cooperativity comes from the build-up of inter-particle coherence through dipole-dipole interactions and leads to the speed-up of decay process. We compare our calculation to recent work [Deiglmayr et al., Eur. Phys. J. D 65, 99 (2011)] and find very good agreement, suggesting that superradiant effects need to be included in a...

  4. Vibrational Spectroscopy and Dynamics of Water.

    Science.gov (United States)

    Perakis, Fivos; Marco, Luigi De; Shalit, Andrey; Tang, Fujie; Kann, Zachary R; Kühne, Thomas D; Torre, Renato; Bonn, Mischa; Nagata, Yuki

    2016-07-13

    We present an overview of recent static and time-resolved vibrational spectroscopic studies of liquid water from ambient conditions to the supercooled state, as well as of crystalline and amorphous ice forms. The structure and dynamics of the complex hydrogen-bond network formed by water molecules in the bulk and interphases are discussed, as well as the dissipation mechanism of vibrational energy throughout this network. A broad range of water investigations are addressed, from conventional infrared and Raman spectroscopy to femtosecond pump-probe, photon-echo, optical Kerr effect, sum-frequency generation, and two-dimensional infrared spectroscopic studies. Additionally, we discuss novel approaches, such as two-dimensional sum-frequency generation, three-dimensional infrared, and two-dimensional Raman terahertz spectroscopy. By comparison of the complementary aspects probed by various linear and nonlinear spectroscopic techniques, a coherent picture of water dynamics and energetics emerges. Furthermore, we outline future perspectives of vibrational spectroscopy for water researches. PMID:27096701

  5. Vibrational spectroscopy in diagnosis and screening

    CERN Document Server

    Severcan, F

    2012-01-01

    In recent years there has been a tremendous growth in the use of vibrational spectroscopic methods for diagnosis and screening. These applications range from diagnosis of disease states in humans, such as cancer, to rapid identification and screening of microorganisms. The growth in such types of studies has been possible thanks to advances in instrumentation and associated computational and mathematical tools for data processing and analysis. This volume of Advances in Biomedical Spectroscopy contains chapters from leading experts who discuss the latest advances in the application of Fourier

  6. Anharmonic Vibrational Analysis of the Infrared and Raman Gas-Phase Spectra of s-trans- and s-gauche-1,3-Butadiene.

    Science.gov (United States)

    Krasnoshchekov, Sergey V; Craig, Norman C; Boopalachandran, Praveenkumar; Laane, Jaan; Stepanov, Nikolay F

    2015-10-29

    A quantum-mechanical (hybrid MP2/cc-pVTZ and CCSD(T)/cc-pVTZ) full quartic potential energy surface (PES) in rectilinear normal coordinates and the second-order operator canonical Van Vleck perturbation theory (CVPT2) are employed to predict the anharmonic vibrational spectra of s-trans- and s-gauche-butadiene (BDE). These predictions are used to interpret their infrared and Raman scattering spectra. New high-temperature Raman spectra in the gas phase are presented in support of assignments for the gauche conformer. The CVPT2 solution is based on a PES and electro-optical properties (EOP; dipole moment and polarizability) expanded in Taylor series. Higher terms than those routinely available from Gaussian09 software were calculated by numerical differentiation of quadratic force fields and EOP using the MP2/cc-pVTZ model. The integer coefficients of the polyad quantum numbers were derived for both conformers of BDE. Replacement of harmonic frequencies by their counterparts from the CCSD(T)/cc-pVTZ model significantly improved the agreement with experimental data for s-trans-BDE (root-mean-square deviation ≈ 5.5 cm(-1)). The accuracy in predicting the rather well-studied spectrum of fundamentals of s-trans-BDE assures good predictions of the spectrum of s-gauche-BDE. A nearly complete assignment of fundamentals was obtained for the gauche conformer. Many nonfundamental transitions of the BDE conformers were interpreted as well. The predictions of multiple Fermi resonances in the complex CH-stretching region correlate well with experiment. It is shown that solving a vibrational anharmonic problem through a numerical-analytic implementation of CVPT2 is a straightforward and computationally advantageous approach for medium-size molecules in comparison with the standard second-order vibrational perturbation theory (VPT2) based on analytic expressions. PMID:26437183

  7. Frequency and zero-point vibrational energy scale factors for double-hybrid density functionals (and other selected methods): can anharmonic force fields be avoided?

    Science.gov (United States)

    Kesharwani, Manoj K; Brauer, Brina; Martin, Jan M L

    2015-03-01

    We have obtained uniform frequency scaling factors λ(harm) (for harmonic frequencies), λ(fund) (for fundamentals), and λ(ZPVE) (for zero-point vibrational energies (ZPVEs)) for the Weigend-Ahlrichs and other selected basis sets for MP2, SCS-MP2, and a variety of DFT functionals including double hybrids. For selected levels of theory, we have also obtained scaling factors for true anharmonic fundamentals and ZPVEs obtained from quartic force fields. For harmonic frequencies, the double hybrids B2PLYP, B2GP-PLYP, and DSD-PBEP86 clearly yield the best performance at RMSD = 10-12 cm(-1) for def2-TZVP and larger basis sets, compared to 5 cm(-1) at the CCSD(T) basis set limit. For ZPVEs, again, the double hybrids are the best performers, reaching root-mean-square deviations (RMSDs) as low as 0.05 kcal/mol, but even mainstream functionals like B3LYP can get down to 0.10 kcal/mol. Explicitly anharmonic ZPVEs only are marginally more accurate. For fundamentals, however, simple uniform scaling is clearly inadequate. PMID:25296165

  8. Hydrogen Bonding in Ionic Liquids Probed by Linear and Nonlinear Vibrational Spectroscopy

    CERN Document Server

    Roth, C; Kerlé, D; Friedriszik, F; Lütgens, M; Lochbrunner, S; Kühn, O; Ludwig, R

    2012-01-01

    Three imidazolium-based ionic liquids of the type [Cnmim][NTf2] with varying alkyl chain lengths (n = 1, 2 and 8) at the 1 position of the imidazolium ring were studied applying IR, linear Raman, and multiplex CARS spectroscopy. The focus has been on the CH-stretching region of the imidazolium ring, which is supposed to carry information about a possible hydrogen bonding network in the ionic liquid. The measurements are compared to calculations of the corresponding anharmonic vibrational spectra for a cluster of [C2mim][NTf2] consisting of four ion pairs. The results support the hypothesis of moderate hydrogen bonding involving the C(4)-H and C(5)-H groups and somewhat stronger hydrogen bonds of the C(2)-H groups.

  9. Origin of the large anharmonicity in the phonon modes of LiBH{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Gremaud, R.; Züttel, A. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory 505 (Hydrogen and Energy), Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Borgschulte, A., E-mail: andreas.borgschulte@empa.ch [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory 505 (Hydrogen and Energy), Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Ramirez-Cuesta, A.J.; Refson, K. [Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, PO Box 2008, MS 6473 Oak Ridge (United States); Colognesi, D. [Istituto dei Sistemi Complessi – sezione di Firenze, Consiglio Nazionale delle Ricerche, via Madonna del piano 10, 50019 Sesto Fiorentino (Italy)

    2013-12-12

    Highlights: • IR, Raman, and INS spectroscopy data and corresponding DFT-calculations on LiBH4. • Mismatch between experiment and theory are due to anharmonicity. • Strong anharmonic effects can be expected for vibrations with high H amplitude. - Abstract: The dynamics and bonding of the complex hydride LiBH{sub 4} have been investigated by vibrational spectroscopy and density functional theory (DFT). The combination of infrared, Raman, and inelastic neutron-scattering (INS) spectroscopies on hydrided and deuterated samples reveals a complete picture of the dynamics of the BH{sub 4}{sup −} ions as well as of the lattice. Particular emphasis is laid on a comparison between experiment and theory, revealing significant discrepancy between the two approaches for vibrations with high anharmonicity, which is related to large vibrational amplitudes. The latter is typical for librational modes in molecular crystals and pseudo-ionic crystals such as complex hydrides. The presented strategy for anharmonic frequency corrections might thus be generally applicable for this kind of materials.

  10. Surface-Bulk Vibrational Correlation Spectroscopy.

    Science.gov (United States)

    Roy, Sandra; Covert, Paul A; Jarisz, Tasha A; Chan, Chantelle; Hore, Dennis K

    2016-05-01

    Homo- and heterospectral correlation analysis are powerful methods for investigating the effects of external influences on the spectra acquired using distinct and complementary techniques. Nonlinear vibrational spectroscopy is a selective and sensitive probe of surface structure changes, as bulk molecules are excluded on the basis of symmetry. However, as a result of this exquisite specificity, it is blind to changes that may be occurring in the solution. We demonstrate that correlation analysis between surface-specific techniques and bulk probes such as infrared absorption or Raman scattering may be used to reveal additional details of the adsorption process. Using the adsorption of water and ethanol binary mixtures as an example, we illustrate that this provides support for a competitive binding model and adds new insight into a dimer-to-bilayer transition proposed from previous experiments and simulations. PMID:27058265

  11. Multireflection sum frequency generation vibrational spectroscopy.

    Science.gov (United States)

    Zhang, Chi; Jasensky, Joshua; Chen, Zhan

    2015-08-18

    We developed a multireflection data collection method in order to improve the signal-to-noise ratio (SNR) and sensitivity of sum frequency generation (SFG) spectroscopy, which we refer to as multireflection SFG, or MRSFG for short. To achieve MRSFG, a collinear laser beam propagation geometry was adopted and trapezoidal Dove prisms were used as sample substrates. An in-depth discussion on the signal and SNR in MRSFG was performed. We showed experimentally, with "m" total internal reflections in a Dove prism, MRSFG signal is ∼m times that of conventional SFG; SNR of the SFG signal-to-background is improved by a factor of >m(1/2) and vibrational signals. Surface molecular structures of adsorbed ethanol molecules, polymer films, and a lipid monolayer were characterized using both MRSFG and conventional SFG. Molecular orientation information on lipid molecules with a 9% composition in a mixed monolayer was measured using MRSFG, which showed a good agreement with that derived from 100% lipid surface coverage using conventional SFG. MRSFG can both improve the spectral quality and detection limit of SFG spectroscopy and is expected to have important applications in surface science for studying structures of molecules with a low surface coverage or less ordered molecular moieties. PMID:26176565

  12. The spectroscopic constants and anharmonic force field of AgSH: An ab initio study.

    Science.gov (United States)

    Zhao, Yanliang; Wang, Meishan; Yang, Chuanlu; Ma, Xiaoguang; Zhu, Ziliang

    2016-07-01

    The equilibrium structure, spectroscopy constants, and anharmonic force field of silver hydrosulfide (AgSH) have been calculated at B3P86, B3PW91 and MP2 methods employing two basis sets, TZP and QZP, respectively. The calculated geometries, ground state rotational constants, harmonic vibrational wave numbers, and quartic and sextic centrifugal distortion constants are compared with the available experimental and theoretical data. The equilibrium rotational constants, fundamental frequencies, anharmonic constants, and vibration-rotation interaction constants, Coriolis coupling constants, cubic and quartic force constants are predicted. The calculated results show that the MP2/TZP results are in good agreement with experiment observation and are also an advisable choice to study the anharmonic force field of AgSH. PMID:27085293

  13. Vibrational spectroscopy in biomedical science: bone

    Science.gov (United States)

    Gamsjäger, Sonja; Zoehrer, R.; Roschger, P.; Fratzl, P.; Klaushofer, K.; Mendelsohn, R.; Paschalis, E. P.

    2009-02-01

    Fourier transform infrared imaging (FTIR) and Raman Microspectroscopy are powerful tools for characterizing the distribution of different chemical moieties in heterogeneous materials. FTIR and Raman measurements have been adapted to assess the maturity of the mineral and the quality of the organic component (collagen and non-collagenous proteins) of the mineralized tissue in bone. Unique to the FTIRI analysis is the capability to provide the spatial distribution of two of the major collagen cross-links (pyridinoline, and dehydro-dihydroxylysinonorleucine) and through the study of normal and diseased bone, relate them to bone strength. These FTIR parameters have been validated based on analysis of model compounds. It is widely accepted that bone strength is determined by bone mass and bone quality. The latter is a multifactorial term encompassing the material and structural properties of bone, and one important aspect of the bone material properties is the organic matrix. The bone material properties can be defined by parameters of mineral and collagen, as determined by FTIR and Raman analysis. Considerably less attention has been directed at collagen, although there are several publications in the literature reporting altered collagen properties associated with fragile bone, in both animals and humans. Since bone is a heterogeneous tissue due to the remodeling process, microscopic areas may be carefully selected based on quantitative Backscattered Electron Imaging or histological staining, thus ensuring comparison of areas with similar metabolic activity and mineral content. In conclusion, FTIRI and Raman vibrational spectroscopy are proving to be powerful tools in bone-related medical research.

  14. Spontaneous and stimulated Raman studies of vibrational dephasing in condensed phases

    International Nuclear Information System (INIS)

    Vibrational dephasing in condensed phases is studied from both a theoretical and experimental standpoint. A theory is presented which describes the dynamics of motional or exchange processes in weakly perturbed systems. This general formalism, which has been previously used to describe motional narrowing in magnetic resonance, is applied to vibrational spectroscopy. The model treats the case of a high frequency vibration anharmonically coupled to a low-frequency vibration. Intermolecular exchange of low frequency vibrational quanta results in a temperature dependent broadening and frequency shift of the high frequency vibration. Analysis of experimental data by this model yields both the exchange rates and the anharmonic couplings

  15. Vibrational spectroscopy and density functional theory calculations on biological molecules

    OpenAIRE

    Peica, Niculina

    2006-01-01

    Infrared (IR) and Raman spectroscopy are among the most widely used techniques in the physical and natural sciences today. Vibrational spectroscopy, including IR and Raman spectroscopy, has both a long and interesting history and an illustrious record of contributions to science. Spectroscopy in the pharmaceutical industry is dominated by techniques such as nuclear magnetic resonance (NMR) and mass spectrometry (MS) for the elucidation of chemical structures. Despite this, the versatility of ...

  16. Study on vibrational relaxation dynamics of phenol–water complex by picosecond time-resolved IR-UV pump–probe spectroscopy in a supersonic molecular beam

    International Nuclear Information System (INIS)

    Graphical abstract: Picosecond IR-UV pump–probe study revealed a detailed energy dissipation route and its time scale from the energy put into the OH(OD) stretching vibration for the phenol–water hydrogen-bonded complex. - Abstract: A comparative study of vibrational energy relaxation (VER) between the monohydrated complexes of phenol-d0 and phenol-d1 is investigated in a supersonic molecular beam. The direct time-resolved measurement of energy redistribution from the phenolic OH/OD stretching mode of the phenol-d0-H2O/phenol-d1-D2O is performed by picosecond IR-UV pump–probe spectroscopy. Two complexes follow the same relaxation process that begins with the intramolecular vibrational energy redistribution (IVR) and the intermolecular vibrational energy redistribution (IVR), which is followed by the vibrational predissociation (VP). The difference in the relaxation lifetimes between them is discussed by anharmonic force field and RRKM calculations. Anharmonic analysis implies that intra- (IVR) and intermolecular (IVR) relaxations occur in parallel in the complexes. The RRKM-predicted dissociation (VP) lifetimes show qualitative agreement with the observed results, suggesting that VP takes place after the statistical energy distribution in the complexes

  17. Spectroscopy and reactions of vibrationally excited transient molecules

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-12-01

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

  18. Translating vibrational spectroscopy into clinical applications - vision or reality?

    Science.gov (United States)

    Petrich, Wolfgang

    2016-06-23

    The Faraday Discussion meeting "Advanced Vibrational Spectroscopy for Biomedical Applications" provided an excellent opportunity to share and discuss recent research and applications on a highly interdisciplinary level. Spectral pathology, single cell analysis, data handling, clinical spectroscopy, and the spectral analysis of biofluids were among the topics covered during the meeting. The focus on discussion rather than "merely" presentation was highly appreciated and fruitful discussions evolved around the interpretation of the amide-bands, optical resolution, the role of diffraction and data analysis procedure, to name a few. The meeting made clear that the spectroscopy of molecular vibrations in biomolecules has evolved from a purely academic research tool to a technology used in clinical practice in some cases. In this sense, biomedical vibrational spectroscopy has reached a pivotal point at which questions like diagnostic value, therapeutic consequence and financial viability are gaining more and more importance. PMID:27250100

  19. Anharmonic collective excitation in a solvable model

    International Nuclear Information System (INIS)

    We apply the time-dependent variational principle, the nuclear field theory, and the boson expansion method to the Lipkin model to discuss anharmonicities of collective vibrational excitations. It is shown that all of these approaches lead to the same anharmonicity to leading order in the number of particles. Comparison with the exact solution of the Lipkin model shows that these theories reproduce quite well

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

    Science.gov (United States)

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

    2015-12-14

    Infrared vibrational nano-spectroscopy based on scattering scanning near-field optical microscopy (s-SNOM) provides intrinsic chemical specificity with nanometer spatial resolution. Here we use incoherent infrared radiation from a 1400 K thermal blackbody emitter for broadband infrared (IR) nano-spectroscopy. With optimized interferometric heterodyne signal amplification we achieve few-monolayer sensitivity in phonon polariton spectroscopy and attomolar molecular vibrational spectroscopy. Near-field localization and nanoscale spatial resolution is demonstrated in imaging flakes of hexagonal boron nitride (hBN) and determination of its phonon polariton dispersion relation. The signal-to-noise ratio calculations and analysis for different samples and illumination sources provide a reference for irradiance requirements and the attainable near-field signal levels in s-SNOM in general. The use of a thermal emitter as an IR source thus opens s-SNOM for routine chemical FTIR nano-spectroscopy. PMID:26698997

  1. Seventh international conference on time-resolved vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

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

  2. Anharmonicity and Confinement in Zeolites: Structure, Spectroscopy and Adsorption Free Energy of Ethanol in H-ZSM-5

    Energy Technology Data Exchange (ETDEWEB)

    Alexopoulos, Konstantinos; Lee, Mal Soon; Liu, Yue; Zhi, Yuchun; Liu, Yuanshuai; Reyniers, Marie-Francoise; Marin, Guy B.; Glezakou, Vassiliki Alexandra; Rousseau, Roger J.; Lercher, Johannes A.

    2016-04-07

    To account for thermal and entropic effects caused by the dynamics of the motion of the reaction intermediates, ethanol adsorption on the Brønsted acid site of the H-ZSM-5 catalyst has been studied at different temperatures and ethanol loadings using ab initio molecular dynamics (AIMD) simulations, infrared (IR) spectroscopy and calorimetric measurements. At low temperatures (T ≤ 400 K) and ethanol loading, a single ethanol molecule adsorbed in H-ZSM-5 forms a Zundel-like structure where the proton is equally shared between the oxygen of the zeolite and the oxygen of the alcohol. At higher ethanol loading, a second ethanol molecule helps to stabilize the protonated ethanol at all temperatures by acting as a solvating agent. The vibrational density of states (VDOS), as calculated from the AIMD simulations, are in excellent agreement with measured IR spectra for C2H5OH, C2H5OD and C2D5OH isotopomers and support the existence of both monomers and dimers. A quasi-harmonic approximation (QHA), applied to the VDOS obtained from the AIMD simulations, provides estimates of adsorption free energy within ~10 kJ/mol of the experimentally determined quantities, whereas the traditional approach, employing harmonic frequencies from a single ground state minimum, strongly overestimates the adsorption free energy by at least ~30 kJ/mol. This discrepancy is traced back to the inability of the harmonic approximation to represent the contributions to the vibrational motions of the ethanol molecule upon confinement in the zeolite. KA, MFR, GBM were supported by the Long Term Structural Methusalem Funding by the Flemish Government – grant number BOF09/01M00409. MSL, VAG, RR and JAL were supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. PNNL is a multiprogram national laboratory operated for DOE by Battelle. Computational resources were provided at W. R. Wiley Environmental

  3. Vibrational photodetachment spectroscopy near the electron affinity of S2

    Science.gov (United States)

    Barrick, J. B.; Yukich, J. N.

    2016-02-01

    We have conducted laser photodetachment spectroscopy near the detachment threshold of the electron affinity of S2 in a 1.8-T field. The ions are prepared by dissociative electron attachment to carbonyl sulfide. The experiment is conducted in a Penning ion trap and with a narrow-band, tunable, Ti:sapphire laser. A hybrid model for photodetachment in an ion trap is fit to the data using the appropriate Franck-Condon factors. The observations reveal detachment from and to the first few vibrational levels of the anion and the neutral molecule, respectively. Evaporative cooling of the anion ensemble condenses the thermal distribution to the lowest initial vibrational states. The subsequent detachment spectroscopy yields results consistent with a vibrationally cooled anion population.

  4. Determining the static electronic and vibrational energy correlations via two-dimensional electronic-vibrational spectroscopy

    International Nuclear Information System (INIS)

    Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrational energies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this paper, we present a theoretical formalism to demonstrate the slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. We also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions

  5. Determining the static electronic and vibrational energy correlations via two-dimensional electronic-vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Hui; Lewis, Nicholas H. C.; Oliver, Thomas A. A.; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, Californial 94720 (United States); Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720 (United States)

    2015-05-07

    Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrational energies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this paper, we present a theoretical formalism to demonstrate the slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. We also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions.

  6. Two-Dimensional Vibrational Spectroscopy of a Dissipative System with the Optimized Mean-Trajectory Approximation

    OpenAIRE

    Alemi, Mallory; Loring, Roger F

    2014-01-01

    The optimized mean-trajectory (OMT) approximation is a semiclassical method for computing vibrational response functions from action-quantized classical trajectories connected by discrete transitions representing radiation–matter interactions. Here we apply this method to an anharmonic chromophore coupled to a harmonic bath. A forward–backward trajectory implementation of the OMT method is described that addresses the numerical challenges of applying the OMT to large systems with disparate fr...

  7. Vibrational spectroscopy at high external pressures the diamond anvil cell

    CERN Document Server

    Ferraro, John R

    1984-01-01

    Vibrational Spectroscopy at High External Pressures: The Diamond Anvil Cell presents the effects of high pressure on the vibrational properties of materials as accomplished in a diamond anvil cell (DAC). The DAC serves the dual purpose of generating the pressures and being transparent to infrared radiation, allowing the observation of changes caused by pressure. The optical probes highlighted will deal principally with infrared and Raman scattering, although some observations in the visible region will also be presented. The book begins with a discussion of the effects of pressure and pres

  8. Probing electronic lifetimes and phonon anharmonicities in high-quality chemical vapor deposited graphene by magneto-Raman spectroscopy

    Science.gov (United States)

    Neumann, Christoph; Halpaap, Donatus; Reichardt, Sven; Banszerus, Luca; Schmitz, Michael; Watanabe, Kenji; Taniguchi, Takashi; Beschoten, Bernd; Stampfer, Christoph

    2015-12-01

    We present a magneto-Raman study on high-quality single-layer graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride by a dry transfer technique. By analyzing the Raman D, G, and 2D peaks, we find that the structural quality of the samples is comparable with state-of-the-art exfoliated graphene flakes. From B-field dependent Raman measurements, we extract the broadening and associated lifetime of the G peak due to anharmonic effects. Furthermore, we determine the decay width and lifetime of Landau level (LL) transitions from magneto-phonon resonances as a function of laser power. At low laser power, we find a minimal decay width of 140 cm-1 highlighting the high electronic quality of the CVD-grown graphene. At higher laser power, we observe an increase of the LL decay width leading to a saturation, with the corresponding lifetime saturating at a minimal value of 18 fs.

  9. Probing electronic lifetimes and phonon anharmonicities in high-quality chemical vapor deposited graphene by magneto-Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Christoph, E-mail: cneumann@physik.rwth-aachen.de; Stampfer, Christoph [JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen (Germany); Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich (Germany); Halpaap, Donatus; Banszerus, Luca; Schmitz, Michael; Beschoten, Bernd [JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen (Germany); Reichardt, Sven [JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen (Germany); Physics and Materials Science Research Unit, Université du Luxembourg, 1511 Luxembourg (Luxembourg); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2015-12-07

    We present a magneto-Raman study on high-quality single-layer graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride by a dry transfer technique. By analyzing the Raman D, G, and 2D peaks, we find that the structural quality of the samples is comparable with state-of-the-art exfoliated graphene flakes. From B-field dependent Raman measurements, we extract the broadening and associated lifetime of the G peak due to anharmonic effects. Furthermore, we determine the decay width and lifetime of Landau level (LL) transitions from magneto-phonon resonances as a function of laser power. At low laser power, we find a minimal decay width of 140 cm{sup −1} highlighting the high electronic quality of the CVD-grown graphene. At higher laser power, we observe an increase of the LL decay width leading to a saturation, with the corresponding lifetime saturating at a minimal value of 18 fs.

  10. Probing electronic lifetimes and phonon anharmonicities in high-quality chemical vapor deposited graphene by magneto-Raman spectroscopy

    International Nuclear Information System (INIS)

    We present a magneto-Raman study on high-quality single-layer graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride by a dry transfer technique. By analyzing the Raman D, G, and 2D peaks, we find that the structural quality of the samples is comparable with state-of-the-art exfoliated graphene flakes. From B-field dependent Raman measurements, we extract the broadening and associated lifetime of the G peak due to anharmonic effects. Furthermore, we determine the decay width and lifetime of Landau level (LL) transitions from magneto-phonon resonances as a function of laser power. At low laser power, we find a minimal decay width of 140 cm−1 highlighting the high electronic quality of the CVD-grown graphene. At higher laser power, we observe an increase of the LL decay width leading to a saturation, with the corresponding lifetime saturating at a minimal value of 18 fs

  11. Investigating buried polymer interfaces using sum frequency generation vibrational spectroscopy

    OpenAIRE

    Chen, Zhan

    2010-01-01

    This paper reviews recent progress in the studies of buried polymer interfaces using sum frequency generation (SFG) vibrational spectroscopy. Both buried solid/liquid and solid/solid interfaces involving polymeric materials are discussed. SFG studies of polymer/water interfaces show that different polymers exhibit varied surface restructuring behavior in water, indicating the importance of probing polymer/water interfaces in situ. SFG has also been applied to the investigation of interfaces b...

  12. Drug-excipient interactions in ketoprofen: A vibrational spectroscopy study

    OpenAIRE

    Carvalho, L. A. E. Batista de; Marques, M. Paula M.; Tomkinson, John

    2006-01-01

    Ketoprofen (3-benzoyl-alpha-methylbenzeneacetic acid) is a widely used nonsteroidal anti-inflammatory drug (NSAID), always administered in the form of drug-excipient physical mixtures (PMs). The occurrence of possible interactions between ketoprofen and two commonly used excipients - lactose (LAC) and polyvinylpyrrolidone (PVP) - was evaluated, through vibrational spectroscopy techniques [both Raman and Inelastic Neutron Scattering (INS)]. Spectral evidence of drug:excipient close contacts, w...

  13. Structural Dynamics of Rotaxanes Studied by Infrared Photon Echo Spectroscopy

    Science.gov (United States)

    Yeremenko, Sergey; Larsen, Olaf F. A.; Bodis, Pavol; Buma, Wybren Jan; Hannam, Jeffrey S.; Leigh, David A.; Woutersen, Sander

    The structural dynamics of a rotaxane is investigated using infrared photon echo peak shift spectroscopy on the N-H stretch vibrational mode. The results demonstrate non-Markovian character of the dynamics of this vibrational mode and an oscillatory component related to the presence of low-frequency modes that are anharmonically coupled to the N-H stretch mode.

  14. Enhanced Vibrational Spectroscopies as Tools for Small Molecule Biosensing

    Directory of Open Access Journals (Sweden)

    Souhir Boujday

    2015-08-01

    Full Text Available In this short summary we summarize some of the latest developments in vibrational spectroscopic tools applied for the sensing of (small molecules and biomolecules in a label-free mode of operation. We first introduce various concepts for the enhancement of InfraRed spectroscopic techniques, including the principles of Attenuated Total Reflection InfraRed (ATR-IR, (phase-modulated InfraRed Reflection Absorption Spectroscopy (IRRAS/PM-IRRAS, and Surface Enhanced Infrared Reflection Absorption Spectroscopy (SEIRAS. Particular attention is put on the use of novel nanostructured substrates that allow for the excitation of propagating and localized surface plasmon modes aimed at operating additional enhancement mechanisms. This is then be complemented by the description of the latest development in Surface- and Tip-Enhanced Raman Spectroscopies, again with an emphasis on the detection of small molecules or bioanalytes.

  15. Nonequilibrium molecular dynamics simulations with a backward-forward trajectories sampling for multidimensional infrared spectroscopy of molecular vibrational modes

    Science.gov (United States)

    Hasegawa, Taisuke; Tanimura, Yoshitaka

    2008-02-01

    A full molecular dynamics (MD) simulation approach to calculate multidimensional third-order infrared (IR) signals of molecular vibrational modes is proposed. Third-order IR spectroscopy involves three-time intervals between three excitation and one probe pulses. The nonequilibrium MD (NEMD) simulation allows us to calculate molecular dipoles from nonequilibrium MD trajectories for different pulse configurations and sequences. While the conventional NEMD approach utilizes MD trajectories started from the initial equilibrium state, our approach does from the intermediate state of the third-order optical process, which leads to the doorway-window decomposition of nonlinear response functions. The decomposition is made before the second pump excitation for a two-dimensional case of IR photon echo measurement, while it is made after the second pump excitation for a three-dimensional case of three-pulse IR photon echo measurement. We show that the three-dimensional IR signals are efficiently calculated by using the MD trajectories backward and forward in time for the doorway and window functions, respectively. We examined the capability of the present approach by evaluating the signals of two- and three-dimensional IR vibrational spectroscopies for liquid hydrogen fluoride. The calculated signals might be explained by anharmonic Brownian model with the linear-linear and square-linear system-bath couplings which was used to discuss the inhomogeneous broadening and dephasing mechanism of vibrational motions. The predicted intermolecular librational spectra clearly reveal the unusually narrow inhomogeneous linewidth due to the one-dimensional character of HF molecule and the strong hydrogen bond network.

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

    Science.gov (United States)

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

    2012-02-14

    Time-resolved vibrational spectroscopy is used to investigate the inter-component motion of an ultraviolet-triggered two-station molecular shuttle. The operation cycle of this molecular shuttle involves several intermediate species, which are observable in the amide I and amide II regions of the mid-IR spectrum. Using ab initio calculations on specific parts of the rotaxane, and by comparing the transient spectra of the normal rotaxane with that of the N-deuterated version, we can assign the observed vibrational modes of each species occurring during the shuttling cycle in an unambiguous way. The complete time- and frequency-dependent data set is analyzed using singular value decomposition (SVD). Using a kinetic model to describe the time-dependent concentrations of the transient species, we derive the absorption spectra associated with each stage in the operation cycle of the molecular shuttle, including the recombination of the charged species. PMID:22033540

  17. Transient grating spectroscopy of SF6 molecular vibrations

    CERN Document Server

    Ferré, Amélie; Burgy, Frédéric; Dagan, Michal; Descamps, Dominique; Dudovich, Nirit; Petit, Stéphane; Soifer, Hadas; Blanchet, Valérie; Mairesse, Yann

    2014-01-01

    Strong field transient grating spectroscopy has shown to be a very versatile tool in time-resolved molecular spectroscopy. Here we use this technique to investigate the high-order harmonic generation from SF6 molecules vibrationally excited by impulsive stimulated Raman scattering. Transient grating spectroscopy enables us to reveal clear modulations of the harmonic emission. This heterodyne detection shows that the harmonic emission generated between 14 to 26 eV is mainly sensitive to two among the three active Raman modes in SF6, i.e. the strongest and fully symmetric nu 1-A1g mode (774 cm-1, 43 fs) and the slowest mode nu5-T2g (524 cm-1, 63 fs). A time-frequency analysis of the harmonic emission reveals additional dynamics: the strength and central frequency of the nu 1 mode oscillate with a frequency of 52 cm-1 (640 fs). This could be a signature of the vibration of dimers in the generating medium. Harmonic 11 shows a remarkable behavior, oscillating in opposite phase, both on the fast (774 cm-1) and slow...

  18. Computational Vibrational Spectroscopy of HDO in Osmolyte-Water Solutions.

    Science.gov (United States)

    Lee, Hochan; Choi, Jun-Ho; Verma, Pramod Kumar; Cho, Minhaeng

    2016-07-28

    The IR absorption and time-resolved IR spectroscopy of the OD stretch mode of HDO in water was successfully used to study osmolyte effects on water H-bonding network. Protecting osmolytes such as sorbitol and trimethylglycine (TMG) make the vibrational OD stretch band red-shifted, whereas urea affects the OD band marginally. Furthermore, we recently showed that, even though sorbitol and TMG cause a slow-down of HDO rotation in their aqueous solutions, urea does not induce any change in the rotational relaxation of HDO in aqueous urea solutions even at high concentrations. To clarify the underlying osmolyte effects on water H-bonding structure and dynamics, we performed molecular dynamics (MD) simulations of a variety of aqueous osmolyte solutions. Using the vibrational solvatochromism model for the OD stretch mode and taking into account the vibrational non-Condon and polarization effects on the OD transition dipole moment, we then calculated the IR absorption spectra and rotational anisotropy decay of the OD stretch mode of HDO for the sake of direct comparisons with our experimental results. The simulation results on the OD stretch IR absorption spectra and the rotational relaxation rate of HDO in osmolyte solutions are found to be in quantitative agreement with experimental data, which confirms the validity of the MD simulation and vibrational solvatochromism approaches. As a result, it becomes clear that the protecting osmolytes like sorbitol and TMG significantly modulate water H-bonding network structure, while urea perturbs water structure little. We anticipate that the computational approach discussed here will serve as an interpretive method with atomic-level chemical accuracy of current linear and nonlinear time-resolved IR spectroscopy of structure and dynamics of water near the surfaces of membranes and proteins under crowded environments. PMID:27341918

  19. The ab initio assigning of the vibrational probing modes of tryptophan: linear shifting of approximate anharmonic frequencies vs. multiplicative scaling of harmonic frequencies

    Czech Academy of Sciences Publication Activity Database

    Kabeláč, Martin; Hobza, Pavel; Špirko, Vladimír

    2009-01-01

    Roč. 11, č. 20 (2009), s. 3921-3926. ISSN 1463-9076 R&D Projects: GA AV ČR IAA400550511; GA AV ČR IAA400550808; GA ČR GA203/06/0420; GA MŠk LC512 Grant ostatní: GA ČR(CZ) GA203/06/0738 Institutional research plan: CEZ:AV0Z40550506 Keywords : tryptophan * anharmonicity * harmonic frequencies * ab initio Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.116, year: 2009

  20. Anharmonic phonon quasiparticle theory of zero-point and thermal shifts in insulators: Heat capacity, bulk modulus, and thermal expansion

    Science.gov (United States)

    Allen, Philip B.

    2015-08-01

    The quasiharmonic (QH) approximation uses harmonic vibrational frequencies ωQ ,H(V ) computed at volumes V near V0 where the Born-Oppenheimer (BO) energy Eel(V ) is minimum. When this is used in the harmonic free energy, QH approximation gives a good zeroth order theory of thermal expansion and first-order theory of bulk modulus, where nth-order means smaller than the leading term by ɛn, where ɛ =ℏ ωvib/Eel or kBT /Eel , and Eel is an electronic energy scale, typically 2 to 10 eV. Experiment often shows evidence for next-order corrections. When such corrections are needed, anharmonic interactions must be included. The most accessible measure of anharmonicity is the quasiparticle (QP) energy ωQ(V ,T ) seen experimentally by vibrational spectroscopy. However, this cannot just be inserted into the harmonic free energy FH. In this paper, a free energy is found that corrects the double-counting of anharmonic interactions that is made when F is approximated by FH( ωQ(V ,T ) ) . The term "QP thermodynamics" is used for this way of treating anharmonicity. It enables (n +1 ) -order corrections if QH theory is accurate to order n . This procedure is used to give corrections to the specific heat and volume thermal expansion. The QH formulas for isothermal (BT) and adiabatic (BS) bulk moduli are clarified, and the route to higher-order corrections is indicated.

  1. Structural dynamics in complex liquids studied with multidimensional vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tokmakoff, Andrei [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2013-08-31

    The development of new sustainable energy sources is linked to our understanding of the molecular properties of water and aqueous solutions. Energy conversion, storage, and transduction processes, particularly those that occur in biology, fuel cells, and batteries, make use of water for the purpose of moving energy in the form of charges and mediating the redox chemistry that allows this energy to be stored as and released from chemical bonds. To build our fundamental knowledge in this area, this project supports work in the Tokmakoff group to investigate the molecular dynamics of water’s hydrogen bond network, and how these dynamics influence its solutes and the mechanism of proton transport in water. To reach the goals of this grant, we developed experiments to observe molecular dynamics in water as directly as possible, using ultrafast multidimensional vibrational spectroscopy. We excite and probe broad vibrational resonances of water, molecular solutes, and protons in water. By correlating how molecules evolve from an initial excitation frequency to a final frequency, we can describe the underlying molecular dynamics. Theoretical modeling of the data with the help of computational spectroscopy coupled with molecular dynamics simulations provided the atomistic insight in these studies.

  2. Vibrational Assignments of Six-Coordinate Ferrous Heme Nitrosyls: New Insight From Nuclear Resonance Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Paulat, F.; Berto, T.C.; George, S.DeBeer; Goodrich, L.; Praneeth, V.K.K.; Sulok, C.D.; Lehnert, N.

    2009-05-21

    This Communication addresses a long-standing problem: the exact vibrational assignments of the low-energy modes of the Fe-N-O subunit in six-coordinate ferrous heme nitrosyl model complexes. This problem is addressed using nuclear resonance vibrational spectroscopy (NRVS) coupled to {sup 15}N{sup 18}O isotope labeling and detailed simulations of the obtained data. Two isotope-sensitive features are identified at 437 and 563 cm{sup -1}. Normal coordinate analysis shows that the 437 cm{sup -1} mode corresponds to the Fe-NO stretch, whereas the 563 cm{sup -1} band is identified with the Fe-N-O bend. The relative NRVS intensities of these features determine the degree of vibrational mixing between the stretch and the bend. The implications of these results are discussed with respect to the trans effect of imidazole on the bound NO. In addition, a comparison to myoglobin-NO (Mb-NO) is made to determine the effect of the Mb active site pocket on the bound NO.

  3. Cross-Propagation Sum-Frequency Generation Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Li; Chen, Shunli; Gan, Wei; Wang, Hongfei

    2016-02-01

    Here we report the theory formulation and the experiment realization of sum-frequency generation vibrational spectroscopy (SFG-VS) in the cross-propagation (XP) geometry or configuration. In the XP geometry, the visible and the infrared (IR) beams in the SFG experiment are delivered to the same location on the surface from visible and IR incident planes perpendicular to each other, avoiding the requirement to have windows or optics to be transparent to both the visible and IR frequencies. Therefore, the XP geometry is applicable to study surfaces in the enclosed vacuum or high pressure chambers with far infrared (FIR) frequencies that can directly access the metal oxide and other lower frequency surface modes, with much broader selection of visible and IR transparent window materials.

  4. Structural characterization of chiral molecules using vibrational circular dichroism spectroscopy

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2006-01-01

    Chiral molecules, i.e., molecules with handedness, are essential to biology, because most amino acids and sugars are chiral. A pair of molecules which are mirror images of each other have identical physical properties, but they differ in their interaction with other chiral molecules. This is the...... cornerstone of biological specificity. Chiral molecules also interact differently with different polarization states of electromagnetic radiation, because the absorption coefficient depends on the state of polarization. This is called dichroism and gives rise to several spectroscopic techniques targeting...... compounds of pharmaceutical interest. Others are transition metal complexes relevant for the search for parity-violation effects in vibrational spectroscopy (rhenium complexes), for asymmetric catalysis (Schiff-base complexes), or as model systems for metal centres in biology (Schiff-bases and heme...

  5. Cryogenic Ion Vibrational Spectroscopy of - CH Activation Intermediates

    Science.gov (United States)

    Marsh, Brett; Garand, Etienne

    2013-06-01

    Despite the rather simple composition of alkanes the strength of their C-C and C-H bonds has made controlled, selective reaction of these compounds an unrealized goal of synthetic chemistry. The field was pioneered by Shilov and coworkers in 1969 when they observed the exchange of H and D in methane that was bubbled into an acidic solution of K_2PtCl_4. The Shilov reaction has since been extended to induce oxidation of methane selectively to methanol and has become the standard bearer of CH activation despite its limitations. The mechanism for the reaction, while inferred from kinetics studies, is still largely uncharacterized. Here, we present our work towards applying cryogenic ion vibrational spectroscopy (CIVS) to capture the intermediate species of this reaction with a focus on the σ-CH adduct formed between methane and Pt(II) complexes that is believed to be crucial to the selectivity and rate of this reaction.

  6. Anharmonicity and electron-phonon coupling in cuprate superconductors studied by inelastic neutron scattering

    International Nuclear Information System (INIS)

    An overview is given on anharmonic lattice vibrations originating from structural instabilities. The transverse vibrations of the chain oxygens in YBa2Cu3O7 are found to be only moderately anharmonic. Measurements of the phonon linewidths in the Cu-O bond stretching vibrations strongly support recent calculations of the electron-phonon coupling. Results are presented on superconductivity-induced frequency shifts at short wavelengths. 20 refs., 15 figs

  7. Composite vibrational spectroscopy of the group 12 difluorides: ZnF2, CdF2, and HgF2

    Science.gov (United States)

    Solomonik, Victor G.; Smirnov, Alexander N.; Navarkin, Ilya S.

    2016-04-01

    The vibrational spectra of group 12 difluorides, MF2 (M = Zn, Cd, Hg), were investigated via coupled cluster singles, doubles, and perturbative triples, CCSD(T), including core correlation, with a series of correlation consistent basis sets ranging in size from triple-zeta through quintuple-zeta quality, which were then extrapolated to the complete basis set (CBS) limit using a variety of extrapolation procedures. The explicitly correlated coupled cluster method, CCSD(T)-F12b, was employed as well. Although exhibiting quite different convergence behavior, the F12b method yielded the CBS limit estimates closely matching more computationally expensive conventional CBS extrapolations. The convergence with respect to basis set size was examined for the contributions entering into composite vibrational spectroscopy, including those from higher-order correlation accounted for through the CCSDT(Q) level of theory, second-order spin-orbit coupling effects assessed within four-component and two-component relativistic formalisms, and vibrational anharmonicity evaluated via a perturbative treatment. Overall, the composite results are in excellent agreement with available experimental values, except for the CdF2 bond-stretching frequencies compared to spectral assignments proposed in a matrix isolation infrared and Raman study of cadmium difluoride vapor species [Loewenschuss et al., J. Chem. Phys. 50, 2502 (1969); Givan and Loewenschuss, J. Chem. Phys. 72, 3809 (1980)]. These assignments are called into question in the light of the composite results.

  8. Anharmonic force fields and thermodynamic functions using density functional theory

    OpenAIRE

    Boese, A. Daniel; Klopper, Wim; Martin, Jan M. L.

    2004-01-01

    The very good performance of modern density functional theory for molecular geometries and harmonic vibrational frequencies has been well established. We investigate the performance of density functional theory (DFT) for quartic force fields, vibrational anharmonicity and rotation-vibration coupling constants, and thermodynamic functions beyond the RRHO (rigid rotor-harmonic oscillator) approximation of a number of small polyatomic molecules. Convergence in terms of basis set, integration gri...

  9. High-Pressure Effects in Benzoic Acid Dimers: Vibrational Spectroscopy

    Science.gov (United States)

    Tao, Yuchuan; Dreger, Zbigniew; Gupta, Yogendra

    2013-06-01

    To understand pressure effects on dimer structure stability, Raman and FTIR spectroscopy were used to examine changes in hydrogen bonded dimers of benzoic acid crystals up to 31 GPa. Raman measurements indicated a phase transition around 7-8 GPa. It is proposed that this transition is caused by a rearrangement of molecules within the dimer leading to a symmetry change from C2h to likely C2 or Cs. This change was reversible upon pressure release from 15 GPa. Pressures above 15 GPa, induced gradual changes in luminescence and a color change in the crystal from white to brownish. FTIR measurements at 31 GPa revealed the formation of a new broad band centered around 3250 cm-1, which was attributed to the stretching vibrations of the O -H bond. It is proposed that hydrogen bonded dimers of benzoic acid transform partially to a covalently bonded compound composed of benzoic anhydride-like molecules and H2O. This study demonstrates that application of high pressure can lead to significant changes in the H-bonded dimer structure, including formation of chemical bonding. Work supported by DOE/NNSA and ONR/MURI.

  10. Vibrational relaxation of the H2O bending mode in liquid water.

    Science.gov (United States)

    Larsen, Olaf F A; Woutersen, Sander

    2004-12-22

    We have studied the vibrational relaxation of the H(2)O bending mode in an H(2)O:HDO:D(2)O isotopic mixture using infrared pump-probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55+/-10 cm(-1) for the H(2)O bending mode, and a value of 400+/-30 fs for its vibrational lifetime. PMID:15606231

  11. Vibrational relaxation of the H2O bending mode in liquid water

    Science.gov (United States)

    Larsen, Olaf F. A.; Woutersen, Sander

    2004-12-01

    We have studied the vibrational relaxation of the H2O bending mode in an H2O:HDO:D2O isotopic mixture using infrared pump-probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55±10 cm-1 for the H2O bending mode, and a value of 400±30 fs for its vibrational lifetime.

  12. Structural characterization of electron-induced proton transfer in the formic acid dimer anion, (HCOOH)2-, with vibrational and photoelectron spectroscopies

    Science.gov (United States)

    Gerardi, Helen K.; DeBlase, Andrew F.; Leavitt, Christopher M.; Su, Xiaoge; Jordan, Kenneth D.; McCoy, Anne B.; Johnson, Mark A.

    2012-04-01

    The (HCOOH)2 anion, formed by electron attachment to the formic acid dimer (FA2), is an archetypal system for exploring the mechanics of the electron-induced proton transfer motif that is purported to occur when neutral nucleic acid base-pairs accommodate an excess electron [K. Aflatooni, G. A. Gallup, and P. D. Burrow, J. Phys. Chem. A 102, 6205 (1998), 10.1021/jp980865n; J. H. Hendricks, S. A. Lyapustina, H. L. de Clercq, J. T. Snodgrass, and K. H. Bowen, J. Chem Phys. 104, 7788 (1996), 10.1063/1.471484; C. Desfrancois, H. Abdoul-Carime, and J. P. Schermann, J. Chem Phys. 104, 7792 (1996)]. The FA2 anion and several of its H/D isotopologues were isolated in the gas phase and characterized using Ar-tagged vibrational predissociation and electron autodetachment spectroscopies. The photoelectron spectrum of the FA2 anion was also recorded using velocity-map imaging. The resulting spectroscopic information verifies the equilibrium FA2- geometry predicted by theory which features a symmetrical, double H-bonded bridge effectively linking together constituents that most closely resemble the formate ion and a dihydroxymethyl radical. The spectroscopic signatures of this ion were analyzed with the aid of calculated anharmonic vibrational band patterns.

  13. E x circle ε Jahn-Teller anharmonic coupling for an octahedral system

    International Nuclear Information System (INIS)

    The coupling between doubly degenerate electronic states and doubly degenerate vibrations is analyzed for an octahedral system on the basis of the introduction of an anharmonic Morse potential for the vibronic part. The vibrations are described by anharmonic coherent states and their linear coupling with the electronic states is considered. The matrix elements of the vibronic interaction are built and the energy levels corresponding to the interaction Hamiltonian are derived. (authors)

  14. Vibrational spectroscopy of –/ – stretching vibrations of copper tetramesityl porphyrin: An algebraic approach

    Indian Academy of Sciences (India)

    Srinivasa Rao Karumuri; Joydeep Choudhury; Nirmal Kumar Sarkar; Ramendu Bhattacharjee

    2010-01-01

    Using Lie algebraic techniques and simpler expressions of the matrix elements of Majorana and Casimir operators given by us, we obtain an effective Hamiltonian operator which conveniently describes stretching vibrations of biomolecules. For a copper tetramesityl porphyrin molecule, the higher excited vibrational levels are calculated by applying the (2) algebraic approach.

  15. Thermal expansion of mullite-type Bi2Al4O9: A study by X-ray diffraction, vibrational spectroscopy and density functional theory

    International Nuclear Information System (INIS)

    Polycrystalline Bi2Al4O9 powder samples were synthesized using the glycerine method. Single crystals were produced from the powder product in a Bi2O3 melt. The lattice thermal expansion of the mullite-type compound was studied using X-ray diffraction, Raman spectroscopy and density functional theory (DFT). The metric parameters were modeled using Grüneisen approximation for the zero pressure equation of state, where the temperature-dependent vibrational internal energy was calculated from the Debye characteristic frequency. Both the first-order and second-order Grüneisen approximations were applied for modeling the volumetric expansion, and the second-order approach provided physically meaningful axial parameters. The phonon density of states as well as phonon dispersion guided to set the characteristic frequency for simulation. The experimental infrared and Raman phonon bands were compared with those calculate from the DFT calculations. Selective Raman modes were analyzed for the thermal anharmonic behaviors using simplified Klemens model. The respective mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. - Graphical abstract: Crystal structure of mullite-type Bi2Al4O9 showing the edge-sharing AlO6 octahedra running parallel to the c-axis. - Highlights: • Thermal expansion of Bi2Al4O9 was studied using XRD, FTIR, Raman and DFT. • Metric parameters were modeled using Grüneisen approximation. • Phonon DOS and phonon dispersion helped to set the Debye frequency. • Mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. • Anharmonicity was analyzed for some selective Raman modes

  16. Structural determination of some uranyl compounds by vibrational spectroscopy

    International Nuclear Information System (INIS)

    The vibrational spectra of different uranyl compounds has been studied and of it spectral information has been used the fundamental asymmetric vibrational frequency, to determine the length and constant bond force U=O by means of the combination of the concept of absorbed energy and the mathematical expression of Badger modified by Jones. It is intended a factor that simplifies the mathematical treatment and the results are compared with the values obtained for other methods. (Author)

  17. Vibrational dynamics of aqueous hydroxide solutions probed using broadband 2DIR spectroscopy

    International Nuclear Information System (INIS)

    We employed ultrafast transient absorption and broadband 2DIR spectroscopy to study the vibrational dynamics of aqueous hydroxide solutions by exciting the O–H stretch vibrations of the strongly hydrogen-bonded hydroxide solvation shell water and probing the continuum absorption of the solvated ion between 1500 and 3800 cm−1. We observe rapid vibrational relaxation processes on 150–250 fs time scales across the entire probed spectral region as well as slower vibrational dynamics on 1–2 ps time scales. Furthermore, the O–H stretch excitation loses its frequency memory in 180 fs, and vibrational energy exchange between bulk-like water vibrations and hydroxide-associated water vibrations occurs in ∼200 fs. The fast dynamics in this system originate in strong nonlinear coupling between intra- and intermolecular vibrations and are explained in terms of non-adiabatic vibrational relaxation. These measurements indicate that the vibrational dynamics of the aqueous hydroxide complex are faster than the time scales reported for long-range transport of protons in aqueous hydroxide solutions

  18. Vibrational dynamics of aqueous hydroxide solutions probed using broadband 2DIR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Aritra [Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637 (United States); Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Tokmakoff, Andrei, E-mail: tokmakoff@uchicago.edu [Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637 (United States)

    2015-11-21

    We employed ultrafast transient absorption and broadband 2DIR spectroscopy to study the vibrational dynamics of aqueous hydroxide solutions by exciting the O–H stretch vibrations of the strongly hydrogen-bonded hydroxide solvation shell water and probing the continuum absorption of the solvated ion between 1500 and 3800 cm{sup −1}. We observe rapid vibrational relaxation processes on 150–250 fs time scales across the entire probed spectral region as well as slower vibrational dynamics on 1–2 ps time scales. Furthermore, the O–H stretch excitation loses its frequency memory in 180 fs, and vibrational energy exchange between bulk-like water vibrations and hydroxide-associated water vibrations occurs in ∼200 fs. The fast dynamics in this system originate in strong nonlinear coupling between intra- and intermolecular vibrations and are explained in terms of non-adiabatic vibrational relaxation. These measurements indicate that the vibrational dynamics of the aqueous hydroxide complex are faster than the time scales reported for long-range transport of protons in aqueous hydroxide solutions.

  19. 2012 VIBRATIONAL SPECTROSCOPY GORDON RESEARCH CONFERENCE, AUGUST 5-10, 2012

    Energy Technology Data Exchange (ETDEWEB)

    Geiger, Franz

    2012-08-10

    The Vibrational Spectroscopy conference brings together experimentalists and theoreticians working at the frontiers of modern vibrational spectroscopy, with a special emphasis on spectroscopies that probe the structure and dynamics of molecules in gases, liquids, and at interfaces. The conference explores the wide range of state-of-the-art techniques based on vibrational motion. These techniques span the fields of time-domain, high-resolution frequency-domain, spatially-resolved, nonlinear, and multidimensional spectroscopies. The conference highlights both the application of these techniques in chemistry, materials, biology, the environment, and medicine as well as the development of theoretical models that enable one to connect spectroscopic signatures to underlying molecular motions including chemical reaction dynamics. The conference goal is to advance the field of vibrational spectroscopy by bringing together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of molecular systems ranging from small polyatomic molecules to large biomolecules, nanomaterials, and environmental systems.

  20. Measuring correlated electronic and vibrational spectral dynamics using line shapes in two-dimensional electronic-vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Nicholas H. C.; Dong, Hui; Oliver, Thomas A. A.; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720 (United States)

    2015-05-07

    Two-dimensional electronic-vibrational (2DEV) spectroscopy is an experimental technique that shows great promise in its ability to provide detailed information concerning the interactions between the electronic and vibrational degrees of freedom in molecular systems. The physical quantities 2DEV is particularly suited for measuring have not yet been fully determined, nor how these effects manifest in the spectra. In this work, we investigate the use of the center line slope of a peak in a 2DEV spectrum as a measure of both the dynamic and static correlations between the electronic and vibrational states of a dye molecule in solution. We show how this center line slope is directly related to the solvation correlation function for the vibrational degrees of freedom. We also demonstrate how the strength with which the vibration on the electronic excited state couples to its bath can be extracted from a set of 2DEV spectra. These analytical techniques are then applied to experimental data from the laser dye 3,3′-diethylthiatricarbocyanine iodide in deuterated chloroform, where we determine the lifetime of the correlation between the electronic transition frequency and the transition frequency for the backbone C = C stretch mode to be ∼1.7 ps. Furthermore, we find that on the electronic excited state, this mode couples to the bath ∼1.5 times more strongly than on the electronic ground state.

  1. Measuring correlated electronic and vibrational spectral dynamics using line shapes in two-dimensional electronic-vibrational spectroscopy.

    Science.gov (United States)

    Lewis, Nicholas H C; Dong, Hui; Oliver, Thomas A A; Fleming, Graham R

    2015-05-01

    Two-dimensional electronic-vibrational (2DEV) spectroscopy is an experimental technique that shows great promise in its ability to provide detailed information concerning the interactions between the electronic and vibrational degrees of freedom in molecular systems. The physical quantities 2DEV is particularly suited for measuring have not yet been fully determined, nor how these effects manifest in the spectra. In this work, we investigate the use of the center line slope of a peak in a 2DEV spectrum as a measure of both the dynamic and static correlations between the electronic and vibrational states of a dye molecule in solution. We show how this center line slope is directly related to the solvation correlation function for the vibrational degrees of freedom. We also demonstrate how the strength with which the vibration on the electronic excited state couples to its bath can be extracted from a set of 2DEV spectra. These analytical techniques are then applied to experimental data from the laser dye 3,3'-diethylthiatricarbocyanine iodide in deuterated chloroform, where we determine the lifetime of the correlation between the electronic transition frequency and the transition frequency for the backbone C = C stretch mode to be ∼1.7 ps. Furthermore, we find that on the electronic excited state, this mode couples to the bath ∼1.5 times more strongly than on the electronic ground state. PMID:25956093

  2. Exact solutions for anharmonic oscillators

    International Nuclear Information System (INIS)

    Rigorous solutions for the one-dimensional quantum mechanical doubly anharmonic oscillator in the form of definite integrals, already presented (Flessas. Phys. Lett. 81 A: 17 (1981)), are here generalised to anharmonic interactions and their interest for models of the charmonium system considered. (U.K.)

  3. Vibrational Spectroscopy of Photoreactive Molecules in Atmospheric Chemistry

    Science.gov (United States)

    Vaida, Veronica

    2010-06-01

    Vibrational overtone spectra of oxidized atmospheric chromophores are presented and analyzed to energies where chemistry through vibrational overtone pumping is possible. Experimental near infrared and visible spectra complemented by dynamical theory are presented to elucidate the light initiated reaction dynamics of pyruvic and of glyoxilic acid photo-decarboxylation. The role of water is investigated by making use of vibrational spectra of hydrates of the title compounds. Consequences of water and sunlight mediated chemistry to formation of secondary organic aerosol in the atmosphere will be discussed. K. L. Plath, J. L. Axson, G. C. Nelson, K. Takahashi, R. T. Skodje and V. Vaida -- React. Kineti. Catal. Lett. 96, 209 (2009) V. Vaida J. Phys. Chem. A 113, 5 (2009) K. Takahashi, K. L. Plath, R. T. Skodje and V. Vaida J. Phys. Chem A 112 7321 (2008)

  4. Action spectroscopy for single-molecule motion induced by vibrational excitation with a scanning tunneling microscope

    OpenAIRE

    Ueba, H.; Persson, B.N.J.

    2007-01-01

    We propose an action spectroscopy for single-molecule motion induced by vibrational excitation with a scanning tunneling microscope (STM). Calculations of the inelastic tunneling current for excitation of the C-O stretch mode of the CO molecule on metal surfaces are combined with a theory which describes how the energy in the vibrational mode is transferred to a reaction coordinate mode to overcome the activation barrier. The calculated rate for CO hopping on Pd (110) as a function of the bia...

  5. Mechanism for vibrational relaxation in water investigated by femtosecond infrared spectroscopy

    Science.gov (United States)

    Nienhuys, Han-Kwang; Woutersen, Sander; van Santen, Rutger A.; Bakker, Huib J.

    1999-07-01

    We present a study on the relaxation of the O-H stretch vibration in a dilute HDO:D2O solution using femtosecond mid-infrared pump-probe spectroscopy. We performed one-color experiments in which the 0→1 vibrational transition is probed at different frequencies, and two-color experiments in which the 1→2 transition is probed. In the one-color experiments, it is observed that the relaxation is faster at the blue side than at the center of the absorption band. Furthermore, it is observed that the vibrational relaxation time T1 shows an anomalous temperature dependence and increases from 0.74±0.01 ps at 298 K to 0.90±0.02 ps at 363 K. These results indicate that the O-H⋯O hydrogen bond forms the dominant accepting mode in the vibrational relaxation of the O-H stretch vibration.

  6. Vibrational spectroscopy of purified C[sub 76

    Energy Technology Data Exchange (ETDEWEB)

    Michel, R.H. (Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Physikalische Chemie und Elektrochemie); Schreiber, H. (Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Physikalische Chemie und Elektrochemie); Gierden, R. (Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Physikalische Chemie und Elektrochemie); Hennrich, F. (Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Physikalische Chemie und Elektrochemie); Rockenberger, J. (Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Physikalische Chemie und Elektrochemie); Beck, R.D. (Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Physikalische Chemie und Elektrochemie); Kappes, M.M. (Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Physikalische Chemie und Elektrochemie); Lehner, C. (Bruker Analytische Messtechnik GmbH, Rheinstetten (Germany)); Adelmann, P. (Kernforschungszentrum Karlsruhe GmbH (Germany). Inst. fuer Nukleare Festkoerperphysik); Armbruster, J.F. (Kernforschungszentrum Karlsruhe GmbH (Germany). Inst. fuer Nukleare Festkoerperphysik)

    1994-07-01

    C[sub 76] was generated by graphite contact arc discharge in helium and purified by high performance liquid chromatography (>98%). We report an infrared and first Raman spectroscopic study of the microcrystalline solid and compare the observed vibrational structure to existing calculations. (orig.)

  7. Vibrational circular dichroism spectroscopy study of paroxetine and femoxetine precursors

    Czech Academy of Sciences Publication Activity Database

    Urbanová, M.; Setnička, V.; Bouř, Petr; Navrátilová, H.; Volka, K.

    2002-01-01

    Roč. 67, - (2002), s. 298-301. ISSN 0006-3525 R&D Projects: GA AV ČR IAA4055104 Institutional research plan: CEZ:AV0Z4055905 Keywords : vibrational circular dichroism Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.372, year: 2002

  8. Proceedings of the national conference on exploring the frontiers of vibrational spectroscopy: abstracts

    International Nuclear Information System (INIS)

    Spectroscopy has played and is playing a very important role as it is one of the most efficient methods of molecular structure studies with the help of which direct information about the chemical compounds can be obtained. Spectroscopy has its contribution in a number of branches in areas such as medicine, industry, environment, agriculture, power, construction, forensic analysis (both criminal and civil cases), etc., where it has revolutionized the very face of these sectors. Vibrational spectroscopic (Infrared and Raman) techniques have demonstrated potential to provide non-destructive, rapid clinically relevant diagnostic information. Raman and infrared spectroscopy enable the biochemical signatures from biological tissues to be extracted and analyzed there by advancing the treatment of cancer. Advancement in instrumentation has allowed the development of numerous infrared and Raman spectroscopic methods. Infrared spectroscopy is tremendously used in the fields of pharmaceuticals. medical diagnostics food and agrochemical quality control, and combustion research. Raman spectroscopy is used in condensed matter physics, biomedicinal fields for tissue analysis and chemistry to study vibrational, rotational, and other low-frequency modes in a system. Keeping in mind the fast development: in the Spectroscopy, we have planned to organize a national level conference for 2 days on 'Exploring the Frontiers of Vibrational Spectroscopy' to bring out the tremendous potential of various Spectroscopic techniques available at the global level. Papers relevant to INIS are indexed separately

  9. Microwave spectroscopy of furfural in vibrationally excited states

    Science.gov (United States)

    Motiyenko, R. A.; Alekseev, E. A.; Dyubko, S. F.

    2007-07-01

    The results of microwave spectrum investigation of the excited vibrational states of furfural in the frequency range between 49 and 149 GHz are reported. In total 15 excited vibrational states (9 for trans-furfural and 6 for cis-furfural) were assigned and analyzed. Six of the 15 investigated states were assigned for the first time. Accurate values of rigid rotor and quartic centrifugal distortion constants of asymmetric top Hamiltonian have been determined for 13 excited states. Also for some states several sextic and octic level constants were needed in order to fit the data within experimental accuracy. The vt = 3 and vs = 1, va = 1 states of trans-furfural were found to be strongly perturbed and only rotational transitions with low Ka values can be reliably identified in this study.

  10. Ultrafast reaction dynamics and vibrational spectroscopy at surfaces

    OpenAIRE

    Hess, Christian

    2001-01-01

    A mechanistic understanding of the surface femtochemistry leading to the formation of hydrogen and the desorption and oxidation of CO from a Ru(001) single crystal surface is obtained by application of a variety of experimental methods. Among these are measurements of the translational energy distributions, two-pulse-correlations, isotope effects, and vibrational spectra of the reaction products after excitation with near-infrared (800 nm) femtosecond laser pulses. It is demonstrated t...

  11. Nonlinear (Anharmonic Casimir Oscillator

    Directory of Open Access Journals (Sweden)

    Habibollah Razmi

    2011-01-01

    Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.

  12. Vibrational and optical spectroscopies integrated with environmental transmission electron microscopy

    International Nuclear Information System (INIS)

    Here, we present a measurement platform for collecting multiple types of spectroscopy data during high-resolution environmental transmission electron microscopy observations of dynamic processes. Such coupled measurements are made possible by a broadband, high-efficiency, free-space optical system. The critical element of the system is a parabolic mirror, inserted using an independent hollow rod and placed below the sample holder which can focus a light on the sample and/or collect the optical response. We demonstrate the versatility of this optical setup by using it to combine in situ atomic-scale electron microscopy observations with Raman spectroscopy. The Raman data is also used to measure the local temperature of the observed sample area. Other applications include, but are not limited to: cathodo- and photoluminescence spectroscopy, and use of the laser as a local, high-rate heating source. - Highlights: • Broadband, high-efficiency design adaptable to other electron microscopes. • Raman spectroscopy integrated with environmental transmission electron microscopy. • Raman spectra peak frequency shifts enable measurement of local sample temperature. • Multiple types of optical spectroscopy enabled, e.g. cathodoluminescence

  13. The study of secondary effects in vibrational and hydrogen bonding properties of 2- and 3-ethynylpyridine and ethynylbenzene by IR spectroscopy.

    Science.gov (United States)

    Vojta, Danijela; Matanović, Ivana; Kovačević, Goran; Baranović, Goran

    2014-11-11

    Weak hydrogen bonds formed by 2- and 3-ethynylpyridine and ethynylbenzene with trimethylphosphate and phenol were characterized by IR spectroscopy and DFT calculations (B3LYP/6-311++G(d, p)). The structure and stability of ethynylpyridines and ethynylbenzene in the gas phase and in the complexes with trimethylphosphate and phenol are discussed in terms of geometry and electronic charge redistribution. Anharmonic effects are taken into account when calculating vibrational wavenumbers of these systems what lead to partial improvement of agreement with experiment. The changes in the electronic charge distribution are behind the frequency shifts of the CC stretching in opposite direction depending on the role the ethyne molecule has in a hydrogen bonded complex (Δν̃=+9 cm(-1) in trimethylphosphate complexes, Δν̃=-3 cm(-1) in phenol complexes). The association constants were determined by keeping the concentrations of proton donors approximately constant and low enough to avoid self-association and the proton acceptors were present in excess. The values obtained for the association constants and enthalpy changes in C2Cl4 (for trimethylphosphate complexes K≈0.5-1.0 mol(-1)dm(3) and -ΔrH≈6-8 kJ mol(-1), for phenol complexes K≈20-40 mol(-1) dm3-ΔrH≈17-22 kJ mol(-1)) are in good agreement with literature data. PMID:24866088

  14. Far-infra-red molecular vibrational spectroscopy by inelastic electron tunneling

    International Nuclear Information System (INIS)

    In this paper the far infrared vibrational spectrum of polyvinyl-formate is reported as can be obtained by an inelastic electron tunneling experiment. The results here described as compared with those previously known from the current literature show that the afore mentioned technique can improve molecular spectroscopy data both as the covered energy range and resolution

  15. Study of cancer cell lines with Fourier transform infrared (FTIR)/vibrational absorption (VA) spectroscopy

    DEFF Research Database (Denmark)

    Uceda Otero, E. P.; Eliel, G. S. N.; Fonseca, E. J. S.;

    2013-01-01

    In this work we have used Fourier transform infrared (FTIR) / vibrational absorption (VA) spectroscopy to study two cancer cell lines: the Henrietta Lacks (HeLa) human cervix carcinoma and 5637 human bladder carcinoma cell lines. Our goal is to experimentally investigate biochemical changes and d...

  16. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy

    CERN Document Server

    Karhu, J; Vainio, M; Metsälä, M; Hoekstra, S; Halonen, L

    2016-01-01

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, $\

  17. Vibrational spectroscopy for online monitoring of extraction solvent degradation products

    International Nuclear Information System (INIS)

    In our research, we are exploring the potential of online monitoring of the organic solvents for the flowsheets relevant to the used nuclear fuel reprocessing and tributyl phosphate (TBP)- based extraction processes in particular. Utilization of vibrational spectroscopic techniques permits the discrimination of the degradation products from the primary constituents of the loaded extraction solvent. Multivariate analysis of the spectral data facilitates development of the regression models for their quantification in real time and potentially enables online implementation of a monitoring system. Raman and FTIR spectral databases were created and used to develop the regression partial least squares (PLS) chemometric models for the quantitative prediction of HDBP (dibutyl phosphoric acid) degradation product, TBP, and UO22+ extraction organic product phase. It was demonstrated that both these spectroscopic techniques are suitable for the quantification of the Purex solvent components in the presence of UO2(NO3)2. Developed PLS models successfully predicted HDBP and TBP organic concentrations in simulated Purex solutions

  18. Vibrational spectroscopy on protons and deuterons in proton conducting perovskites

    DEFF Research Database (Denmark)

    Glerup, M.; Poulsen, F.W.; Berg, R.W.

    2002-01-01

    C, the OH-stretch cannot be observed due to thermal broadening, but the peak reappears upon cooling; the OH and OD absorption bands in BaCe1-chiNdchiO3 are very broad and, in addition, an electronic transition of Nd-3 is observed at 1900-1930 cm(-1);finally, IR reflectance spectroscopy on BaZr0.9Y0.1O3, La0...

  19. Monte Carlo wave packet propagators for multidimensional vibrational spectroscopy

    OpenAIRE

    Samsonyuk, Andriy

    2013-01-01

    A direct Monte Carlo wave packet sampling method for Liouville space pathways, based on the solution of the quantum stochastic differential equation in a doubled Hilbert space, was developed to widen the scope of nonlinear spectroscopy simulations. Using this method we can: compute third order infrared response functions for systems with thousands of states, which was not possible before; simulate a very broad range of experiments with any number of pulse interactions; reduce the computationa...

  20. TOPICAL REVIEW: Nonlinear two-dimensional vibrational spectroscopy of peptides

    Science.gov (United States)

    Woutersen, Sander; Hamm, Peter

    2002-10-01

    In this overview, we discuss theoretical and experimental aspects of nonlinear two-dimensional infrared (2D-IR) spectroscopy. With this technique both peptide conformation and conformational flexibility can be probed. The quantitative relation between the experimental 2D-IR spectrum and the peptide conformation is discussed, and examples of how the conformation of a peptide and the timescale of its fluctuations are derived from its (time-resolved) 2D spectrum are presented.

  1. Partial dynamical symmetry and anharmonicity in γ-soft nuclei

    International Nuclear Information System (INIS)

    The concept of dynamical symmetry (DS) is now widely accepted to be of central importance in our understanding of many-body systems, such as nuclei. Its hallmarks are the solvability of the complete spectrum, and the existence of exact quantum numbers for all eigenstates. However, in most applications to realistic systems, the predictions of an exact DS are rarely fulfilled and one is compelled to break it. More often one finds that the assumed symmetry is not obeyed uniformly, i.e., is fulfilled by only some states but not by others. The need to address such situations has led to the introduction of partial dynamical symmetries (PDSs). The essential idea is to relax the stringent conditions of complete solvability, so that the DS is broken, but part of the eigen spectrum remains solvable with good symmetry. Various types of bosonic and fermionic PDS, have been shown to be relevant to nuclear spectroscopy [1-7] and to quantum phase transitions [8]. In the present contribution we extend the notion of PDS to encompass Hamiltonians with higher-order terms. We present a systematic procedure for constructing such PDS Hamiltonians and demonstrate their relevance to the anharmonicity of excited bands in the -soft nucleus 196Pt. The work, to be reported, was done in collaboration with J.E. Garcfa-Ramos (Huelva) and P. Van backer (GANIL) [9]. The SO(6)-DS limit of the interacting boson model (IBM) [10], provides a good description of the rotational spectrum and E2 rates for states in the ground band of 196Pt [11]. However, the resulting fit to energies of excited bands is quite poor. The empirical anharmonicity of excited vibrational bands is large and negative. On the other hand, in the SO(6)-DS limit, the calculated anharmonicity is fixed by the number of valence nucleons, and is found to be in marked disagreement with the empirical value. A detailed study of double-phonon excitations within the IBM, has concluded that large anharmonicities can be incorporated only by the

  2. Vibration-rotation alchemy in acetylene (12C2H2), ? at low vibrational excitation: from high resolution spectroscopy to fast intramolecular dynamics

    Science.gov (United States)

    Perry, David S.; Miller, Anthony; Amyay, Badr; Fayt, André; Herman, Michel

    2010-04-01

    The link between energy-resolved spectra and time-resolved dynamics is explored quantitatively for acetylene (12C2H2), ? with up to 8600 cm-1 of vibrational energy. This comparison is based on the extensive and reliable knowledge of the vibration-rotation energy levels and on the model Hamiltonian used to fit them to high precision [B. Amyay, S. Robert, M. Herman, A. Fayt, B. Raghavendra, A. Moudens, J. Thiévin, B. Rowe, and R. Georges, J. Chem. Phys. 131, 114301 (2009)]. Simulated intensity borrowing features in high resolution absorption spectra and predicted survival probabilities in intramolecular vibrational redistribution (IVR) are first investigated for the v 4 + v 5 and v 3 bright states, for J = 2, 30 and 100. The dependence of the results on the rotational quantum number and on the choice of vibrational bright state reflects the interplay of three kinds of off-diagonal resonances: anharmonic, rotational l-type, and Coriolis. The dynamical quantities used to characterize the calculated time-dependent dynamics are the dilution factor φ d, the IVR lifetime τ IVR , and the recurrence time τ rec. For the two bright states v 3 + 2v 4 and 7v 4, the collisionless dynamics for thermally averaged rotational distributions at T = 27, 270 and 500 K were calculated from the available spectroscopic data. For the 7v 4 bright state, an apparent irreversible decay of is found. In all cases, the model Hamiltonian allows a detailed calculation of the energy flow among all of the coupled zeroth-order vibration-rotation states.

  3. Examining Low Frequency Molecular Modulations from the High Frequency Vantage Point: Anharmonically-Coupled Low Frequency Modes in PCET Model Systems

    Science.gov (United States)

    Reynolds, Anthony

    Proton-coupled electron transfer model systems (PCET) are examined using polarization selective femtosecond infrared pump-probe spectroscopy to determine how the structural modes are coupled to the OH/OD stretching vibrational mode by monitoring low frequency oscillations in the OH/OD vibrational mode using pump-probe techniques. For all of the systems discussed in this dissertation, low frequency modes are anharmonically coupled to the OH/OD stretching vibration. The OH/OD stretching vibration discussed in this dissertation have complex and broad lineshapes in the infrared region (IR) that are difficult to decipher. A broadband IR (BBIR) source, when used as part of a third order nonlinear infrared pump-probe spectroscopy, gains access into the electronic ground state potential energy surface. This information reveals the molecular dynamics that give rise to the complex structure in an IR spectra. The BBIR used for these experiments is generated by focusing 800 nm/400 nm pulses into compressed air and is tunable from 2 -- 5 microns with a FWHM greater than 1200 wavenumbers. The BBIR is a crucial mid-IR source in subsequent chapters for examining the broad lineshapes of the OH/OD stretching mode, which often exceeds 200 wavenumbers. The coupling of low frequency structural modulations to hydrogen bonding dynamics in PCET systems is explored by using the OH/OD stretching vibration in CCl4 or CHCl3. Third order nonlinear ultrafast infrared pump-probe spectroscopy is used to gather information on the high frequency OH/OD stretching vibrational modes in the ground state such as vibrational relaxation time and anharmonic vibrational coupling to low frequency structural modulations. At least one anharmonically coupled low frequency mode between 120 and 250 wavenumbers has been observed in all systems. To better understand and visualize how the low frequency mode may contribute to the PCET chemistry, we calculated the fundamental frequencies and third order coupling

  4. Vibrational spectroscopy characterization of magnetron sputtered silicon oxide and silicon oxynitride films

    International Nuclear Information System (INIS)

    Vibrational (infrared and Raman) spectroscopy has been used to characterize SiOxNy and SiOx films prepared by magnetron sputtering on steel and silicon substrates. Interference bands in the infrared reflectivity measurements provided the film thickness and the dielectric function of the films. Vibrational modes bands were obtained both from infrared and Raman spectra providing useful information on the bonding structure and the microstructure (formation of nano-voids in some coatings) for these amorphous (or nanocrystalline) coatings. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis have also been carried out to determine the composition and texture of the films, and to correlate these data with the vibrational spectroscopy studies. The angular dependence of the reflectivity spectra provides the dispersion of vibrational and interference polaritons modes, what allows to separate these two types of bands especially in the frequency regions where overlaps/resonances occurred. Finally the attenuated total reflection Fourier transform infrared measurements have been also carried out demonstrating the feasibility and high sensitivity of the technique. Comparison of the spectra of the SiOxNy films prepared in various conditions demonstrates how films can be prepared from pure silicon oxide to silicon oxynitride with reduced oxygen content.

  5. Correlating the motion of electrons and nuclei with two-dimensional electronic-vibrational spectroscopy.

    Science.gov (United States)

    Oliver, Thomas A A; Lewis, Nicholas H C; Fleming, Graham R

    2014-07-15

    Multidimensional nonlinear spectroscopy, in the electronic and vibrational regimes, has reached maturity. To date, no experimental technique has combined the advantages of 2D electronic spectroscopy and 2D infrared spectroscopy, monitoring the evolution of the electronic and nuclear degrees of freedom simultaneously. The interplay and coupling between the electronic state and vibrational manifold is fundamental to understanding ensuing nonradiative pathways, especially those that involve conical intersections. We have developed a new experimental technique that is capable of correlating the electronic and vibrational degrees of freedom: 2D electronic-vibrational spectroscopy (2D-EV). We apply this new technique to the study of the 4-(di-cyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H-pyran (DCM) laser dye in deuterated dimethyl sulfoxide and its excited state relaxation pathways. From 2D-EV spectra, we elucidate a ballistic mechanism on the excited state potential energy surface whereby molecules are almost instantaneously projected uphill in energy toward a transition state between locally excited and charge-transfer states, as evidenced by a rapid blue shift on the electronic axis of our 2D-EV spectra. The change in minimum energy structure in this excited state nonradiative crossing is evident as the central frequency of a specific vibrational mode changes on a many-picoseconds timescale. The underlying electronic dynamics, which occur on the hundreds of femtoseconds timescale, drive the far slower ensuing nuclear motions on the excited state potential surface, and serve as a excellent illustration for the unprecedented detail that 2D-EV will afford to photochemical reaction dynamics. PMID:24927586

  6. Vibrationally resolved UV/Vis spectroscopy with time-dependent density functional based tight binding

    CERN Document Server

    Rüger, Robert; van Lenthe, Erik; Heine, Thomas; Visscher, Lucas

    2016-01-01

    We report a time-dependent density functional based tight-binding (TD-DFTB) scheme for the calculation of UV/Vis spectra, explicitly taking into account the excitation of nuclear vibrations via the harmonic approximation. The theory of vibrationally resolved UV/Vis spectroscopy is first summarized from the viewpoint of TD-DFTB. The method is benchmarked against time-dependent density functional theory (TD-DFT) calculations for strongly dipole allowed excitations in various aromatic and polar molecules. Using the recent 3ob:freq parameter set of Elstner's group, excellent agreement with TD-DFT calculations using local functionals was achieved.

  7. Vibrational ladder-climbing in surface-enhanced, ultrafast infrared spectroscopy.

    Science.gov (United States)

    Kraack, Jan Philip; Hamm, Peter

    2016-06-28

    In a recent work (J. Phys. Chem. C 2016, 120, 3350-3359), we have introduced the concept of surface-enhanced, two-dimensional attenuated total reflectance (2D ATR IR) spectroscopy with modest enhancement factors (450), which allows for multi-quantum IR excitation of adsorbed molecules, a process known as "vibrational ladder-climbing", even for weakly absorbing (ε ultrafast dynamics of highly excited vibrational states or surface-sensitive coherent control experiments of ground-state reactions at solid-liquid interfaces. PMID:27265518

  8. Thermochromism in polyalkylthiophenes: Molecular aspects from vibrational spectroscopy

    Science.gov (United States)

    Zerbi, G.; Chierichetti, B.; Ingänas, O.

    1991-03-01

    It is known that polyalkylthiophenes show reversible thermochromism within a well-defined temperature range. The vibrational infrared and Raman spectra are used as structural probes for understanding the structures of polyhexyl and polyoctyl thiophenes at room temperature and their evolution with temperature during the thermochromic process. The seemingly sample IR and Raman spectra of these materials are explained in terms of the theory of the effective conjugation coordinate which also accounts for the observed ``dispersion'' of the Raman spectrum with exciting wavelength or from solid to solution states in terms of changes of effective conjugation length. A detailed description of the structure of the system is reached. At room T the sample consists mainly of two phases: (i) an ordered phase with the alkyl side chains in the transplanar structure and the main chain in a quasicoplanar or coplanar conformation and (ii) a disordered phase with the alkyl residue fully conformationally coiled and the main chain conformationally twisted with the torsional angle of ˜ 30°. Upon heating, the relative concentration of the disordered phase increases. The temperature dependence of the side chain and the main chain conformations are similar, thus showing that the coiling of the side chain drives the twisting of the main chain. The thermochromism is thus accounted for.

  9. Electron-Induced Vibrational Spectroscopy. A New and Unique Tool To Unravel the Molecular Structure of Polymer Surfaces

    OpenAIRE

    Pireaux, J. J.; Gregoire, Ch.; Caudano, R.; Rei Vilar, M.; Brinkhuis, R; Schouten, A.J.

    1991-01-01

    Among the surface-sensitive spectroscopies used to characterize clean and surface-modified polymers, one technique has rather recently emerged as a very promising complementary tool. High-resolution electron energy loss spectroscopy, or electron-induced vibrational spectroscopy, has potentially all the attributes of the well-known optical (infrared and Raman) spectroscopies; it clearly adds to X-ray photoelectron spectroscopy the possibility to go beyond surface elemental and chemical analysi...

  10. Vibrational relaxation dynamics in transient grating spectroscopy studied by rate equations based on time-dependent correlation function

    Institute of Scientific and Technical Information of China (English)

    Yu Guo-Yang; Song Yun-Fei; He Xing; Zheng Xian-Xu; Tan Duo-Wang; Chen Jun; Yang Yan-Qiang

    2012-01-01

    A modified model,a set of rate equations based on time-dependent correlation function,is used to study vibrational relaxation dynamics in transient grating spectroscopy.The dephasing,the population dynamics,and the vibrational coherence concerning two vibrational states are observed respectively in organic dye IR780 perchlorate molecules doped polyvinyl alcohol matrix.The result shows that in addition to the information concerning system-environment interaction and vibrational coherence,the vibrational energy transfer can be described by this modified model.

  11. Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy

    International Nuclear Information System (INIS)

    The far-infrared dielectric function of a wide range of organic molecules is dominated by vibrations involving a substantial fraction of the atoms forming the molecule and motion associated with intermolecular hydrogen bond vibrations. Due to their collective nature such modes are highly sensitive to the intra- and intermolecular structure and thus provide a unique fingerprint of the conformational state of the molecule and effects of its environment. We demonstrate the use of terahertz time-domain spectroscopy (THz-TDS) for recording the far-infrared (0.5-4.0 THz) dielectric function of the four nucleobases and corresponding nucleosides forming the building blocks of deoxyribose nucleic acid (DNA). We observe numerous distinct spectral features with large differences between the molecules in both frequency-dependent absorption coefficient and index of refraction. Assisted by results from density-functional calculations we interpret the origin of the observed resonances as vibrations of hydrogen bonds between the molecules

  12. Communication: Vibrational and vibronic coherences in the two dimensional spectroscopy of coupled electron-nuclear motion

    International Nuclear Information System (INIS)

    We theoretically investigate the photon-echo spectroscopy of coupled electron-nuclear quantum dynamics. Two situations are treated. In the first case, the Born-Oppenheimer (adiabatic) approximation holds. It is then possible to interpret the two-dimensional (2D) spectra in terms of vibrational motion taking place in different electronic states. In particular, pure vibrational coherences which are related to oscillations in the time-dependent third-order polarization can be identified. This concept fails in the second case, where strong non-adiabatic coupling leads to the breakdown of the Born-Oppenheimer-approximation. Then, the 2D-spectra reveal a complicated vibronic structure and vibrational coherences cannot be disentangled from the electronic motion

  13. Damage-free vibrational spectroscopy of biological materials in the electron microscope

    Science.gov (United States)

    Rez, Peter; Aoki, Toshihiro; March, Katia; Gur, Dvir; Krivanek, Ondrej L.; Dellby, Niklas; Lovejoy, Tracy C.; Wolf, Sharon G.; Cohen, Hagai

    2016-03-01

    Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an `aloof' electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies guanine crystals in their native state, resolving their characteristic C-H, N-H and C=O vibrational signatures with no observable radiation damage. The technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ~10 nm, simultaneously combined with imaging in the electron microscope.

  14. Communication: Vibrational and vibronic coherences in the two dimensional spectroscopy of coupled electron-nuclear motion

    Energy Technology Data Exchange (ETDEWEB)

    Albert, Julian; Falge, Mirjam; Hildenbrand, Heiko; Engel, Volker [Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Emil-Fischer-Str. 42, Campus Nord, Am Hubland, 97074 Würzburg (Germany); Gomez, Sandra; Sola, Ignacio R. [Departamento de Quimica Fisica, Universidad Complutense, 28040 Madrid (Spain)

    2015-07-28

    We theoretically investigate the photon-echo spectroscopy of coupled electron-nuclear quantum dynamics. Two situations are treated. In the first case, the Born-Oppenheimer (adiabatic) approximation holds. It is then possible to interpret the two-dimensional (2D) spectra in terms of vibrational motion taking place in different electronic states. In particular, pure vibrational coherences which are related to oscillations in the time-dependent third-order polarization can be identified. This concept fails in the second case, where strong non-adiabatic coupling leads to the breakdown of the Born-Oppenheimer-approximation. Then, the 2D-spectra reveal a complicated vibronic structure and vibrational coherences cannot be disentangled from the electronic motion.

  15. Two-dimensional vibrational spectroscopy of rotaxane-based molecular machines.

    Science.gov (United States)

    Bodis, Pavol; Panman, Matthijs R; Bakker, Bert H; Mateo-Alonso, Aurelio; Prato, Maurizio; Buma, Wybren Jan; Brouwer, Albert M; Kay, Euan R; Leigh, David A; Woutersen, Sander

    2009-09-15

    It has recently become possible to synthesize mechanical devices the size of a single molecule. Although it is tempting to regard such molecular machines as nanoscale versions of their macroscopic analogs, many notions from macroscopic mechanics no longer apply at a molecular level. For instance, the concept of viscous friction is meaningless for a molecular machine because the size of the solvent molecules that cause the friction is comparable to that of the machine itself. Furthermore, in many cases, the interactions between a molecular machine and its surroundings are comparable to the force driving the machine. As a result, a certain amount of intrinsic randomness exists in the motion of molecular machines, and the details of their mechanics are largely unknown. For a detailed understanding of the mechanical behavior of molecular machines, experiments that probe their motion on an ultrafast time scale, such as two-dimensional (2D) vibrational spectroscopy, are essential. This method uses coupling between vibrational modes in a molecule to investigate the molecular conformation. The coupling shows up as off-diagonal peaks in a 2D graph of the vibrational response of the molecule, analogous to the spin coupling observed in multidimensional NMR spectroscopy. Both spin coupling and vibrational coupling are sensitive probes of the molecular conformation, but 2D vibrational spectroscopy shows orders of magnitude better time resolution than NMR. In this Account, we use 2D vibrational spectroscopy to study molecular machines based on rotaxanes. These devices consist of a linear thread and a macrocycle that is noncovalently locked onto the thread. In the rotaxanes we study, the macrocycle and the thread both contain CO and NH groups. By determining the coupling between the stretching modes of these goups from the cross peaks in the 2D spectrum, we directly and quantitatively probe the relative position and orientation of the macrocycle and the thread for both a small

  16. Vibrational spectroscopy of the borate mineral kotoite Mg₃(BO₃)₂.

    Science.gov (United States)

    Frost, Ray L; Xi, Yunfei

    2013-02-15

    Vibrational spectroscopy has been used to assess the structure of kotoite a borate mineral of magnesium which is isostructural with jimboite. The mineral is orthorhombic with point group: 2/m 2/m 2/m. The mineral has the potential as a new memory insulator material. The mineral has been characterised by a combination of Raman and infrared spectroscopy. The Raman spectrum is dominated by a very intense band at 835 cm(-1), assigned to the symmetric stretching mode of tetrahedral boron. Raman bands at 919, 985 and 1015 cm(-1) are attributed to the antisymmetric stretching modes of tetrahedral boron. Kotoite is strictly an hydrous borate mineral. An intense Raman band observed at 3559 cm(-1) is attributed to the stretching vibration of hydroxyl units, more likely to be associated with the borate mineral hydroxyborate. The lack of observation of water bending modes proves the absence of water in the kotoite structure. PMID:23257343

  17. Nuclear resonance vibrational spectroscopy (NRVS) of rubredoxin and MoFe protein crystals

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yisong [University of California, Department of Applied Science (United States); Brecht, Eric [Montana State University, Department of Chemistry and Biochemistry (United States); Aznavour, Kristen [University of Southern California, Department of Chemistry (United States); Nix, Jay C. [Lawrence Berkeley National Laboratory, Physical Biosciences Division (United States); Xiao, Yuming; Wang, Hongxin [University of California, Department of Applied Science (United States); George, Simon J. [Lawrence Berkeley National Laboratory, Physical Biosciences Division (United States); Bau, Robert [University of Southern California, Department of Chemistry (United States); Keable, Stephen; Peters, John W. [Montana State University, Department of Chemistry and Biochemistry (United States); Adams, Michael W. W. [University of Georgia, Department of Biochemistry and Molecular Biology (United States); Jenney, Francis E. Jr. [Georgia Campus, Philadelphia College of Osteopathic Medicine (United States); Sturhahn, Wolfgang; Alp, Ercan E.; Zhao, Jiyong [Argonne National Laboratory, Advanced Photon Source (United States); Yoda, Yoshitaka [JASRI (Japan); Cramer, Stephen P., E-mail: spcramer@lbl.gov [University of California, Department of Applied Science (United States)

    2013-12-15

    We have applied {sup 57}Fe nuclear resonance vibrational spectroscopy (NRVS) for the first time to study the dynamics of Fe centers in Iron-sulfur protein crystals, including oxidized wild type rubredoxin crystals from Pyrococcus furiosus, and the MoFe protein of nitrogenase from Azotobacter vinelandii. Thanks to the NRVS selection rule, selectively probed vibrational modes have been observed in both oriented rubredoxin and MoFe protein crystals. The NRVS work was complemented by extended X-ray absorption fine structure spectroscopy (EXAFS) measurements on oxidized wild type rubredoxin crystals from Pyrococcus furiosus. The EXAFS spectra revealed the Fe-S bond length difference in oxidized Pf Rd protein, which is qualitatively consistent with the crystal structure.

  18. Detecting anharmonicity at a glance

    International Nuclear Information System (INIS)

    Harmonic motion is generally presented in such a way that most of the students believe that the small oscillations of a body are all harmonic. Since the situation is not actually so simple, and since the comprehension of harmonic motion is essential in many physical contexts, we present here some suggestions, addressed to undergraduate students and pre-service teachers, that allow one to find out at a glance the anharmonicity of a motion. Starting from a didactically motivated definition of harmonic motion, and stressing the importance of the interplay between mathematics and experiments, we give a four-point criterion for anharmonicity together with some emblematic examples. The role of linear damping is also analysed in relation to the gradual changing of harmonicity into anharmonicity when the ratio between the damping coefficient and the zero-friction angular frequency increases. (paper)

  19. Detecting anharmonicity at a glance

    Science.gov (United States)

    Giliberti, M.; Stellato, M.; Barbieri, S.; Cavinato, M.; Rigon, E.; Tamborini, M.

    2014-11-01

    Harmonic motion is generally presented in such a way that most of the students believe that the small oscillations of a body are all harmonic. Since the situation is not actually so simple, and since the comprehension of harmonic motion is essential in many physical contexts, we present here some suggestions, addressed to undergraduate students and pre-service teachers, that allow one to find out at a glance the anharmonicity of a motion. Starting from a didactically motivated definition of harmonic motion, and stressing the importance of the interplay between mathematics and experiments, we give a four-point criterion for anharmonicity together with some emblematic examples. The role of linear damping is also analysed in relation to the gradual changing of harmonicity into anharmonicity when the ratio between the damping coefficient and the zero-friction angular frequency increases.

  20. Structure and vibrational spectroscopy of salt water/air interfaces: Predictions from classical molecular dynamics simulations

    Czech Academy of Sciences Publication Activity Database

    Brown, E. C.; Mucha, Martin; Jungwirth, Pavel; Tobias, D. J.

    2005-01-01

    Roč. 109, - (2005), s. 7934-7940. ISSN 1520-6106 R&D Projects: GA MŠk(CZ) ME 644; GA MŠk(CZ) LC512 Grant ostatní: NSF(US) CHE 0431512 Institutional research plan: CEZ:AV0Z40550506 Keywords : vibrational spectroscopy * salt water * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.033, year: 2005

  1. Vibrational spectra of CO on Ni (100) studied by infrared emission spectroscopy

    International Nuclear Information System (INIS)

    We have developed the technique of infrared emission spectroscopy in order to observe vibrational modes of molecules adsorbed on clean, single crystal metal surfaces. A novel apparatus has been constructed which measures the emission from a single crystal sample in thermal equilibrium at room temperature. The apparatus consists of a liquid helium cooled infrared grating spectrometer coupled to an ultrahigh vacuum system equipped with surface preparation and characterization facilities. 3 references, 3 figures

  2. Anharmonic densities of states: A general dynamics-based solution

    Science.gov (United States)

    Jellinek, Julius; Aleinikava, Darya

    2016-06-01

    Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.

  3. Vibrational Spectral Signatures of Crystalline Cellulose Using High Resolution Broadband Sum Frequency Generation Vibrational Spectroscopy (HR-BB-SFG-VS)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Libing; Lu, Zhou; Velarde Ruiz Esparza, Luis A.; Fu, Li; Pu, Yunqiao; Ding, Shi-You; Ragauskas, Art J.; Wang, Hongfei; Yang, Bin

    2015-06-01

    Here we reported the first sub-wavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) study on both the C-H and O-H region spectra of crystalline cellulose. HR-BB-SFG-VS has about 10 times better resolution than the conventional scanning SFG-VS and is known to be able to measure the intrinsic spectral lineshape and to resolve much more spectral details. With HR-BB-SFG-VS, we found that in cellulose from different sources, including Avicel and cellulose crystals isolated from algae Valonia (Iα) and tunicates (Iβ), the spectral signatures in the OH regions were unique for different allomorphs, i.e. Iα and Iβ, while the spectral signatures in the C-H regions varied in all samples examined. Even though the origin of the different behaviors of the crystalline cellulose in the O-H and C-H vibrational frequency regions is yet to be correlated to the structure of cellulose, these results provided new spectroscopic methods and opportunities to classify and understand the basic crystalline structure, as well as variations, in polymorphism of the crystalline cellulose structure.

  4. Exciton–vibrational coupling in the dynamics and spectroscopy of Frenkel excitons in molecular aggregates

    International Nuclear Information System (INIS)

    The influence of exciton–vibrational coupling on the optical and transport properties of molecular aggregates is an old problem that gained renewed interest in recent years. On the experimental side, various nonlinear spectroscopic techniques gave insight into the dynamics of systems as complex as photosynthetic antennae. Striking evidence was gathered that in these protein–pigment complexes quantum coherence is operative even at room temperature conditions. Investigations were triggered to understand the role of vibrational degrees of freedom, beyond that of a heat bath characterized by thermal fluctuations. This development was paralleled by theory, where efficient methods emerged, which could provide the proper frame to perform non-Markovian and non-perturbative simulations of exciton–vibrational dynamics and spectroscopy. This review summarizes the state of affairs of the theory of exciton–vibrational interaction in molecular aggregates and photosynthetic antenna complexes. The focus is put on the discussion of basic effects of exciton–vibrational interaction from the stationary and dynamics points of view. Here, the molecular dimer plays a prominent role as it permits a systematic investigation of absorption and emission spectra by numerical diagonalization of the exciton–vibrational Hamiltonian in a truncated Hilbert space. An extension to larger aggregates, having many coupled nuclear degrees of freedom, becomes possible with the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method for wave packet propagation. In fact it will be shown that this method allows one to approach the limit of almost continuous spectral densities, which is usually the realm of density matrix theory. Real system–bath situations are introduced for two models, which differ in the way strongly coupled nuclear coordinates are treated, as a part of the relevant system or the bath. A rather detailed exposition of the Hierarchy Equations Of Motion (HEOM

  5. Exciton–vibrational coupling in the dynamics and spectroscopy of Frenkel excitons in molecular aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Schröter, M.; Ivanov, S.D.; Schulze, J. [Institut für Physik, Universität Rostock, D-18051 Rostock (Germany); Polyutov, S.P. [Institut für Physik, Universität Rostock, D-18051 Rostock (Germany); Laboratory for Nonlinear Optics and Spectroscopy, Siberian Federal University, Svobodniy, 79, 660041 Krasnoyarsk (Russian Federation); Yan, Y. [Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Normal College, Guizhou 550018 (China); Pullerits, T. [Department of Chemical Physics, Lund University, P.O. Box 124, S-22100 Lund (Sweden); Kühn, O., E-mail: oliver.kuehn@uni-rostock.de [Institut für Physik, Universität Rostock, D-18051 Rostock (Germany)

    2015-03-18

    The influence of exciton–vibrational coupling on the optical and transport properties of molecular aggregates is an old problem that gained renewed interest in recent years. On the experimental side, various nonlinear spectroscopic techniques gave insight into the dynamics of systems as complex as photosynthetic antennae. Striking evidence was gathered that in these protein–pigment complexes quantum coherence is operative even at room temperature conditions. Investigations were triggered to understand the role of vibrational degrees of freedom, beyond that of a heat bath characterized by thermal fluctuations. This development was paralleled by theory, where efficient methods emerged, which could provide the proper frame to perform non-Markovian and non-perturbative simulations of exciton–vibrational dynamics and spectroscopy. This review summarizes the state of affairs of the theory of exciton–vibrational interaction in molecular aggregates and photosynthetic antenna complexes. The focus is put on the discussion of basic effects of exciton–vibrational interaction from the stationary and dynamics points of view. Here, the molecular dimer plays a prominent role as it permits a systematic investigation of absorption and emission spectra by numerical diagonalization of the exciton–vibrational Hamiltonian in a truncated Hilbert space. An extension to larger aggregates, having many coupled nuclear degrees of freedom, becomes possible with the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method for wave packet propagation. In fact it will be shown that this method allows one to approach the limit of almost continuous spectral densities, which is usually the realm of density matrix theory. Real system–bath situations are introduced for two models, which differ in the way strongly coupled nuclear coordinates are treated, as a part of the relevant system or the bath. A rather detailed exposition of the Hierarchy Equations Of Motion (HEOM

  6. HOF分子非谐性力场、光谱常数和振动能级的迭代三激发耦合簇计算%The study of anharmonic force fields, spectroscopic constants and vibrational levels of HOF using iterative triplet couple cluster approach

    Institute of Scientific and Technical Information of China (English)

    陈恒杰; 方旺; 刘丰奎; 薛善增

    2014-01-01

    采用包含迭代三激发的耦合簇理论( CC3和CCSDT-3),在aug-cc-pVTZ基组水平上对HOF分子几何构型进行优化。通过解析二阶导数结合有限差分技术获得HOF二阶、完全三阶和半对角四阶力场。通过非谐性分析,得到其基频、旋振相互作用常数、非谐性常数和离心畸变光谱常数。应用二阶振动微扰理论(VPT2)得到HOF多个泛频峰位置。目前计算值与实验及其它文献结果符合良好。%The molecular equilibrium structure of HOF has been optimized using iterative triplet coupled cluster approach (CC3 and CCSDT-3) together with aug-cc-pVTZ basis set.Quadratic, full cubic and semidiagonal part of the quartic force field have been obtained by the analytic second derivatives and finite difference techniques. Fundamental frequencies, vibration-rotation interaction constants, anharmonic constants and centrifugal distor-tion constants have been evaluated according to the anharmonic analytics.Several overtones have been expected by the vibrational second-order perturbation theory ( VPT2 ) .The present calculation values are in good agree-ment with others theoretical and experimental results.

  7. 2D-IR spectroscopy of hydrogen-bond-mediated vibrational excitation transfer.

    Science.gov (United States)

    Chuntonov, Lev

    2016-05-18

    Vibrational excitation transfer along the hydrogen-bond-mediated pathways in the complex of methyl acetate (MA) and 4-cyanophenol (4CP) was studied by dual-frequency femtosecond two-dimensional infrared spectroscopy. We excited the energy-donating ester carbonyl stretching vibrational mode and followed the transfer to the energy-accepting benzene ring and cyano stretching vibrations. The complexes with no, one, and two hydrogen-bonded 4CP molecules were studied. Vibrational relaxation of the carbonyl mode is more efficient in both hydrogen-bonded complexes as compared with free MA molecules. The inter-molecular transport in a hydrogen-bonded complex involving a single 4CP molecule is slower than that in a complex with two 4CP molecules. In the former, vibrational relaxation leads to local heating, as shown by the spectroscopy of the carbonyl mode, whereas the local heating is suppressed in the latter because the excitation redistribution is more efficient. At early times, the transfer to the benzene ring is governed by its direct coupling with the energy-donating carbonyl mode, whereas at later times intermediate states are involved. The transfer to a more distant site of the cyano group in 4CP involves intermediate states at all times, since no direct coupling between the energy-donating and accepting modes was observed. We anticipate that our findings will be of importance for spectroscopic studies of bio-molecular structures and dynamics, and inter- and intra-molecular signaling pathways, and for developing molecular networking applications. PMID:27145861

  8. Spectroscopy

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    This introductory booklet covers the basics of molecular spectroscopy, infrared and Raman methods, instrumental considerations, symmetry analysis of molecules, group theory and selection rules, as well as assignments of fundamental vibrational modes in molecules.......This introductory booklet covers the basics of molecular spectroscopy, infrared and Raman methods, instrumental considerations, symmetry analysis of molecules, group theory and selection rules, as well as assignments of fundamental vibrational modes in molecules....

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

    Energy Technology Data Exchange (ETDEWEB)

    Cahoon, James Francis

    2008-12-16

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

  10. Vibrational emission analysis of the CN molecules in laser-induced breakdown spectroscopy of organic compounds

    International Nuclear Information System (INIS)

    Laser-induced breakdown spectroscopy (LIBS) of organic materials is based on the analysis of atomic and ionic emission lines and on a few molecular bands, the most important being the CN violet system and the C2 Swan system. This paper is focused in molecular emission of LIBS plasmas based on the CN (B2Σ–X2Σ) band, one of the strongest emissions appearing in all carbon materials when analyzed in air atmosphere. An analysis of this band with sufficient spectral resolution provides a great deal of information on the molecule, which has revealed that valuable information can be obtained from the plume chemistry and dynamics affecting the excitation mechanisms of the molecules. The vibrational emission of this molecular band has been investigated to establish the dependence of this emission on the molecular structure of the materials. The paper shows that excitation/emission phenomena of molecular species observed in the plume depend strongly on the time interval selected and on the irradiance deposited on the sample surface. Precise time resolved LIBS measurements are needed for the observation of distinctive CN emission. For the organic compounds studied, larger differences in the behavior of the vibrational emission occur at early stages after plasma ignition. Since molecular emission is generally more complex than that involving atomic emission, local plasma conditions as well as plume chemistry may induce changes in vibrational emission of molecules. As a consequence, alterations in the distribution of the emissions occur in terms of relative intensities, being sensitive to the molecular structure of every single material. - Highlights: • Vibrational emission of CN species in laser-induced plasmas has been investigated. • Distribution of vibrational emission of CN has been found to be time dependent. • Laser irradiance affects the vibrational distribution of the CN molecules. • Plume chemistry controls the excitation mechanisms of CN molecules in the

  11. Positive Anharmonicities: The Oxonide Anion as an Example

    Science.gov (United States)

    Lee, Timothy J.; Arnold, James O. (Technical Monitor)

    1997-01-01

    An accurate ab initio quartic force field for the ozonide anion has been determined at the singles and doubles coupled-cluster level of theory that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T), using the augmented valence triple-zeta correlation consistent one-particle basis set. Convergence of the harmonic frequencies with respect to the one-particle basis set has been demonstrated by computing quadratic force fields at the CCSD(T) level using augmented valence double-zeta and quadruple-zeta basis sets. Fundamental vibrational frequencies have been determined via second-order ro-vibrational perturbation theory and also using exact variational methods. Agreement is very good, and they both show that the antisymmetric O-O stretch, v 3, possesses a positive anharmonic correction (that is, the fundamental frequency is predicted to be higher in energy than the harmonic frequency). Comparison of the O_3 and O3 quartic force fields shows that the positive anharmonic correction is the result of a particularly large F3333 symmetry internal coordinate force constant. The reasonableness of this force constant has been tested by computing both F33 and F3333 at the CCSD, CCSD(T), and CASPT2 levels of theory. A discussion of known positive anharmonicities for stretching modes is presented.

  12. Detection of vibrational-overtone excitation in water via laser-induced grating spectroscopy

    International Nuclear Information System (INIS)

    In this paper we describe a method, based on the laser-induced grating technique, for studying the spectroscopy of vibrational overtone-excited gas-phase water. Two phase-coherent visible laser beams whose frequencies are in the range of the third overtone of the OH stretch in water are crossed in the gas-phase sample. As the wavelength of these excitation beams is scanned through individual rovibrational OH overtone transitions, vibrational energy is deposited into the water in a spatially sinusoidal pattern. A fixed-frequency 266 nm probe laser beam is diffracted from the resultant transmission diffraction grating in water. We show that under collision-free conditions, probe laser diffraction is observed from the initially excited grating, which is a necessary condition for using this technique to study the absorption spectroscopy of the vibrationally excited molecules. Under multiple collision conditions, a probe laser wavelength-independent refractive index grating is formed within the bulk sample. In addition, we observe temporal oscillations in the grating diffraction efficiency arising from excitation of standing acoustic waves

  13. Vibration-rotational overtones absorption of solid hydrogens using optoacoustic spectroscopy technique

    International Nuclear Information System (INIS)

    Vibrational-rotational overtones absorption solid hydrogens (H2, D2, HD) is studied using pulsed laser piezoeletric transducer (PULPIT) optoacoustic spectroscopy is studied. A general downward shift in energy from isolated molecular energies is observed. Studying normal-hydrogen it was observed that the phonon excitations associated with double-molecular transitions are predominantly transverse-optical phonons, whereas the excitations associated with single-molecular transitions are predominantly longitudinal - optical phonons. Multiplet structures were observed for certain double transitions in parahydrogen and orthodeuterium. The HD spectrum, besides presenting the sharp zero-phonon lines and the associated phonon side bands, like H2 and D2, showed also two different features. This observation was common to all the transitions involving pure rotational excitation in H2 and D2, which showed broad linewidths. This, together with some other facts (fluorescence lifetime *approx*105 sec; weak internal vibration and lattice coupling), led to the proposition of a mechanism for the fast nonradiative relaxation in solid hydrogens, implied from some observed experimental evidences. This relaxation, due to strong coupling, would happen in two steps: the internal vibration modes would relax to the rotational modes of the molecules, and then this rotational modes would relax to the lattice vibration modes. (Author)

  14. Accurate Lineshapes from Sub-1 cm-1 Resolution Sum Frequency Generation Vibrational Spectroscopy of α-Pinene at Room Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Mifflin, Amanda L.; Velarde Ruiz Esparza, Luis A.; Ho, Junming; Psciuk, Brian; Negre, Christian; Ebben, Carlena J.; Upshur, Mary Alice; Lu, Zhou; Strick, Benjamin; Thomson, Regan; Batista, Victor; Wang, Hongfei; Geiger, Franz M.

    2015-02-26

    Room temperature sub-wavenumber high-resolution broadband sum frequency generation (HR-BB-SFG) spectra of the common terpene (+)-α-pinene reveal ten peaks in the C–H stretching region. The spectral resolution exceeds that of Fourier transform infrared, femtosecond stimulated Raman, and traditional BB-SFG and scanning SFG spectroscopy of the same molecule. Experiment and simulation show the spectral lineshapes to be accurate. Homogeneous vibrational decoherence lifetimes of up to 1.7 psec are assigned to specific oscillators and compare favorably to lifetimes computed from density functional tight binding molecular dynamics calculations, while phase-resolved spectra yield orientation information for them. We propose the new spectroscopy as an attractive alternative to time-resolved vibrational spectroscopy or heterodyne-detection schemes for studying vibrational energy relaxation and vibrational coherences in molecules.

  15. Far-field nanoscale infrared spectroscopy of vibrational fingerprints of molecules with graphene plasmons

    CERN Document Server

    Hu, Hai; Zhai, Feng; Hu, Debo; Liu, Ruina; Liu, Kaihui; Sun, Zhipei; Dai, Qing

    2016-01-01

    Infrared spectroscopy, especially for molecular vibrations in the fingerprint region between 600 and 1500 cm-1, is a powerful characterization method for bulk materials. However, molecular fingerprinting at the nanoscale level still remains a significant challenge, due to weak light-matter interaction between micron-wavelengthed infrared light and nano-sized molecules. Here, we demonstrate molecular fingerprinting at the nanoscale level using our specially designed graphene plasmonic structure on CaF2 nanofilm. This structure not only avoids the plasmon-phonon hybridization, but also provides in situ electrically-tunable graphene plasmon covering the entire infrared fingerprint region, which was previously unattainable. In addition, undisturbed and highly-confined graphene plasmon offers simultaneous detection of in-plane and out-of-plane vibrational modes with ultrahigh detection sensitivity down to the sub-monolayer level, significantly pushing the current detection limit of far-field mid-infrared spectrosc...

  16. Structural information on ball milled magnesium hydride from vibrational spectroscopy and ab-initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Schimmel, H.G. [Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Johnson, M.R. [Institut Laue-Langevin, 6, rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Kearley, G.J. [Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Ramirez-Cuesta, A.J. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); Huot, J. [Institut de recherche sur l' hydrogene, Universite du Quebec a Trois-Rivieres, 3351 des Forges, PO Box 500, Trois-Rivieres, Que., G9A 5H7 (Canada); Mulder, F.M. [Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)]. E-mail: f.m.mulder@iri.tudelft.nl

    2005-05-03

    Ball milled magnesium hydride with an average size of about 40 nm and bulk magnesium hydride have been studied with vibrational spectroscopy together with density functional computer calculations. Using this combination of techniques structural information can now be obtained on a nanometer scale, which is especially important for nanosized samples. Such samples exhibit very broad diffraction lines, from which limited information about the structure can be extracted. It was found that ball milling distorts the vibrational spectra due to distribution in stresses over the sample. Cycling of the hydrogen content of ball milled samples results in the spectrum of unmilled samples, while the particle size remains small and hydrogen storage characteristics continue to be better for ball milled samples. We conclude that improved performance for hydrogen storage applications of ball milled magnesium hydride has to be attributed to the reduction of the particle size, while defect densities inside the particles play less of a role.

  17. Structural information on ball milled magnesium hydride from vibrational spectroscopy and ab-initio calculations

    International Nuclear Information System (INIS)

    Ball milled magnesium hydride with an average size of about 40 nm and bulk magnesium hydride have been studied with vibrational spectroscopy together with density functional computer calculations. Using this combination of techniques structural information can now be obtained on a nanometer scale, which is especially important for nanosized samples. Such samples exhibit very broad diffraction lines, from which limited information about the structure can be extracted. It was found that ball milling distorts the vibrational spectra due to distribution in stresses over the sample. Cycling of the hydrogen content of ball milled samples results in the spectrum of unmilled samples, while the particle size remains small and hydrogen storage characteristics continue to be better for ball milled samples. We conclude that improved performance for hydrogen storage applications of ball milled magnesium hydride has to be attributed to the reduction of the particle size, while defect densities inside the particles play less of a role

  18. Time-resolved two-dimensional vibrational spectroscopy of a short α-helix in water

    Science.gov (United States)

    Woutersen, Sander; Hamm, Peter

    2001-10-01

    Nonlinear two-dimensional (2D) vibrational spectroscopy has been used to investigate the amide I band of an alanine-based 21-residue α-helical peptide in aqueous solution. Whereas the linear absorption spectrum consists of a single, broad amide I band, the 2D vibrational spectrum clearly reveals that this band is composed of two amide I transitions, which are assigned to the A and E1 modes. The A-E1 frequency splitting is found to be approximately 10 cm-1. We find that the amide I band is inhomogeneously broadened due to conformational disorder of the helix. The 2D line shapes can be well described using distributions of the dihedral angles (φ,ψ) around their average values with a width of 20°, confirming previous molecular-dynamics studies. Time-resolved 2D measurements show that the conformation fluctuates on a time scale of picoseconds.

  19. Hydrogen bonding to carbonyl oxygen of nitrogen-pyramidalized amide - detection of pyramidalization direction preference by vibrational circular dichroism spectroscopy.

    Science.gov (United States)

    Wang, Siyuan; Taniguchi, Tohru; Monde, Kenji; Kawahata, Masatoshi; Yamaguchi, Kentaro; Otani, Yuko; Ohwada, Tomohiko

    2016-03-01

    Nitrogen-pyramidalization of amide increases electron density on nitrogen and decreases that on carbonyl oxygen. We identified hydrogen-bonding to carbonyl of nitrogen-pyramidalized bicyclic β-proline derivatives by crystallography, and by NMR and vibrational circular dichroism (VCD) spectroscopy in solution. Such hydrogen-bonding can switch the preferred nitrogen-pyramidalization direction, as detected by VCD spectroscopy. PMID:26889607

  20. Laser deposition, vibrational spectroscopy, NMR spectroscopy and STM imaging of C60 and C70

    International Nuclear Information System (INIS)

    The authors of this paper demonstrated that C60 and C70, as well as other fullerenes, can be deposited and accumulated on surfaces using laser ablation of graphite in an inert gas atmosphere. Indicating the presence of C60 in carbon soot, the authors showed that samples consisting exclusively of C60 and C70 can be sublimed from such soot. Vibrational Raman spectra of C60 and C70 were obtained from these samples. The C60 spectrum is consistent with the calculated spectrum of Buckminsterfullerene, and the strongest three lines can be assigned on the basis of frequency and polarization. The NMR spectrum of dissolved C60 was then obtained, and found to consist of a single resonance, establishing the Icosahedral symmetry of this molecule. STM images of the C60 molecules on a Au(111) crystal face show that these clusters form hexagonal arrays with an intercluster spacing of 11.0 Angstrom and are mobile at ambient temperature. Distinctly taller species evident in the arrays are believed to be C70 clusters. Vibrational Raman and infrared spectra have also been obtained for separated C60 and C70

  1. Vibrational spectroscopy: a tool being developed for the noninvasive monitoring of wound healing

    Science.gov (United States)

    Crane, Nicole J.; Elster, Eric A.

    2012-01-01

    Wound care and management accounted for over 1.8 million hospital discharges in 2009. The complex nature of wound physiology involves hundreds of overlapping processes that we have only begun to understand over the past three decades. The management of wounds remains a significant challenge for inexperienced clinicians. The ensuing inflammatory response ultimately dictates the pace of wound healing and tissue regeneration. Consequently, the eventual timing of wound closure or definitive coverage is often subjective. Some wounds fail to close, or dehisce, despite the use and application of novel wound-specific treatment modalities. An understanding of the molecular environment of acute and chronic wounds throughout the wound-healing process can provide valuable insight into the mechanisms associated with the patient's outcome. Pathologic alterations of wounds are accompanied by fundamental changes in the molecular environment that can be analyzed by vibrational spectroscopy. Vibrational spectroscopy, specifically Raman and Fourier transform infrared spectroscopy, offers the capability to accurately detect and identify the various molecules that compose the extracellular matrix during wound healing in their native state. The identified changes might provide the objective markers of wound healing, which can then be integrated with clinical characteristics to guide the management of wounds.

  2. Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions.

    Science.gov (United States)

    Choi, Jun-Ho; Kim, Heejae; Kim, Seongheun; Lim, Sohee; Chon, Bonghwan; Cho, Minhaeng

    2015-05-28

    The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O-D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O-D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O-D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O-D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O-D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O-D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O-D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O-D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O-D stretch mode is shown to be important and the asymmetric line shapes of the O-D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We anticipate that this

  3. Thermal expansion of mullite-type Bi{sub 2}Al{sub 4}O{sub 9}: A study by X-ray diffraction, vibrational spectroscopy and density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Mangir Murshed, M., E-mail: murshed@uni-bremen.de [Chemische Kristallographie fester Stoffe, Institut für Anorganische Chemie, Universität Bremens, Leobener Straße, D-28359 Bremen (Germany); Mendive, Cecilia B.; Curti, Mariano [Departamento de Química, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Dean Funes 3350, B7600AYL Mar del Plata (Argentina); Šehović, Malik [Chemische Kristallographie fester Stoffe, Institut für Anorganische Chemie, Universität Bremens, Leobener Straße, D-28359 Bremen (Germany); Friedrich, Alexandra [Institut für Geowissenschaften, Abteilung Kristallographie, Goethe-Universität Frankfurt, Altenhöferallee 1, D-60438 Frankfurt am Main (Germany); Fischer, Michael [Kristallographie, FB Geowissenschaften, Universität Bremen, Klagenfurter Straße, D-28359 Bremen (Germany); Gesing, Thorsten M. [Chemische Kristallographie fester Stoffe, Institut für Anorganische Chemie, Universität Bremens, Leobener Straße, D-28359 Bremen (Germany)

    2015-09-15

    Polycrystalline Bi{sub 2}Al{sub 4}O{sub 9} powder samples were synthesized using the glycerine method. Single crystals were produced from the powder product in a Bi{sub 2}O{sub 3} melt. The lattice thermal expansion of the mullite-type compound was studied using X-ray diffraction, Raman spectroscopy and density functional theory (DFT). The metric parameters were modeled using Grüneisen approximation for the zero pressure equation of state, where the temperature-dependent vibrational internal energy was calculated from the Debye characteristic frequency. Both the first-order and second-order Grüneisen approximations were applied for modeling the volumetric expansion, and the second-order approach provided physically meaningful axial parameters. The phonon density of states as well as phonon dispersion guided to set the characteristic frequency for simulation. The experimental infrared and Raman phonon bands were compared with those calculate from the DFT calculations. Selective Raman modes were analyzed for the thermal anharmonic behaviors using simplified Klemens model. The respective mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. - Graphical abstract: Crystal structure of mullite-type Bi{sub 2}Al{sub 4}O{sub 9} showing the edge-sharing AlO{sub 6} octahedra running parallel to the c-axis. - Highlights: • Thermal expansion of Bi{sub 2}Al{sub 4}O{sub 9} was studied using XRD, FTIR, Raman and DFT. • Metric parameters were modeled using Grüneisen approximation. • Phonon DOS and phonon dispersion helped to set the Debye frequency. • Mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. • Anharmonicity was analyzed for some selective Raman modes.

  4. Vibrational frequencies of anti-diabetic drug studied by terahertz time-domain spectroscopy

    Science.gov (United States)

    Du, S. Q.; Li, H.; Xie, L.; Chen, L.; Peng, Y.; Zhu, Y. M.; Li, H.; Dong, P.; Wang, J. T.

    2012-04-01

    By using terahertz time-domain spectroscopy, the absorption spectra of seven anti-diabetic pills have been investigated. For gliquidone, glipizide, gliclazide, and glimepiride, an obvious resonance peak is found at 1.37 THz. Furthermore, to overcome the limit of density functional theory that can analyze the normal mode frequencies of the ground state of organic material, we also present a method that relies on pharmacophore recognition, from which we can obtain the resonance peak at 1.37 THz can be attributed to the vibration of sulfonylurea group. The results indicate that the veracity of density functional theory can be increased by combining pharmacophore recognition.

  5. Unveiling Microscopic Structures of Charged Water Interfaces by Surface-Specific Vibrational Spectroscopy.

    Science.gov (United States)

    Wen, Yu-Chieh; Zha, Shuai; Liu, Xing; Yang, Shanshan; Guo, Pan; Shi, Guosheng; Fang, Haiping; Shen, Y Ron; Tian, Chuanshan

    2016-01-01

    A sum-frequency spectroscopy scheme is developed that allows the measurement of vibrational spectra of the interfacial molecular structure of charged water interfaces. The application of this scheme to a prototype lipid-aqueous interface as a demonstration reveals an interfacial hydrogen-bonding water layer structure that responds sensitively to the charge state of the lipid headgroup and its interaction with specific ions. This novel technique provides unique opportunities to search for better understanding of electrochemistry and biological aqueous interfaces at a deeper molecular level. PMID:26799031

  6. Communication: Atomic force detection of single-molecule nonlinear optical vibrational spectroscopy

    International Nuclear Information System (INIS)

    Atomic Force Microscopy (AFM) allows for a highly sensitive detection of spectroscopic signals. This has been first demonstrated for NMR of a single molecule and recently extended to stimulated Raman in the optical regime. We theoretically investigate the use of optical forces to detect time and frequency domain nonlinear optical signals. We show that, with proper phase matching, the AFM-detected signals closely resemble coherent heterodyne-detected signals. Applications are made to AFM-detected and heterodyne-detected vibrational resonances in Coherent Anti-Stokes Raman Spectroscopy (χ(3)) and sum or difference frequency generation (χ(2))

  7. Isotope-edited two-dimensional vibrational spectroscopy of trialanine in aqueous solution

    Science.gov (United States)

    Woutersen, S.; Hamm, P.

    2001-02-01

    Two-dimensional vibrational spectroscopy is applied to the amide I mode of trialanine and two of its isotopomers dissolved in heavy water. We use site-directed 13C isotope substitution to change the individual frequencies of the coupled oscillators, and hence to modify specific matrix elements of the molecular Hamiltonian. It is found that all of the results can be well described by an excitonic model for the amide I band, using the same coupling strength and dipole-dipole angle for all three isotopomers. This demonstrates that these two spectral parameters are determined by the secondary structure of the peptide, which remains unchanged upon isotope substitution.

  8. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    OpenAIRE

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-01-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labeled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F (DvMF) [NiFe]-hydrogenase. A unique ‘wagging’ mode involving H− motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy (NRVS) and density fu...

  9. Additional compact formulas for vibrational dynamic dipole polarizabilities and hyperpolarizabilities

    OpenAIRE

    Bishop, David M.; Luis Luis, Josep Maria; Kirtman, Bernard

    1998-01-01

    Compact expressions, complete through second order in electrical and/or mechanical anharmonicity, are given for the dynamic dipole vibrational polarizability and dynamic first and second vibrational hyperpolarizabilities. Certain contributions not previously formulated are now included

  10. The Clusters-in-a-Liquid Approach for Solvation: New Insights from the Conformer Specific Gas Phase Spectroscopy and Vibrational Optical Activity Spectroscopy

    OpenAIRE

    Perera, Angelo S.; Thomas, Javix; Poopari, Mohammad R.; Xu, Yunjie

    2016-01-01

    Vibrational optical activity spectroscopies, namely vibrational circular dichroism (VCD) and Raman optical activity (ROA), have been emerged in the past decade as powerful spectroscopic tools for stereochemical information of a wide range of chiral compounds in solution directly. More recently, their applications in unveiling solvent effects, especially those associated with water solvent, have been explored. In this review article, we first select a few examples to demonstrate the unique sen...

  11. Excited-State Vibrational Coherence in Perylene Bisimide Probed by Femtosecond Broadband Pump-Probe Spectroscopy.

    Science.gov (United States)

    Son, Minjung; Park, Kyu Hyung; Yoon, Min-Chul; Kim, Pyosang; Kim, Dongho

    2015-06-18

    Broadband laser pulses with ultrashort duration are capable of triggering impulsive excitation of the superposition of vibrational eigenstates, giving rise to quantum beating signals originating from coherent wave packet motions along the potential energy surface. In this work, coherent vibrational wave packet dynamics of an N,N'-bis(2,6-dimethylphenyl)perylene bisimide (DMP-PBI) were investigated by femtosecond broadband pump-probe spectroscopy which features fast and balanced data acquisition with a wide spectral coverage of >200 nm. Clear modulations were observed in the envelope of the stimulated emission decay profiles of DMP-PBI with the oscillation frequencies of 140 and 275 cm(-1). Fast Fourier transform analysis of each oscillatory mode revealed characteristic phase jumps near the maxima of the steady-state fluorescence, indicating that the observed vibrational coherence originates from an excited-state wave packet motion. Quantum calculations of the normal modes at the low-frequency region suggest that low-frequency C-C (C═C) stretching motions accompanied by deformation of the dimethylphenyl substituents are responsible for the manifestation of such coherent wave packet dynamics. PMID:25992707

  12. Vibrational self-trapping in beta-sheet structures observed with femtosecond nonlinear infrared spectroscopy.

    Science.gov (United States)

    Bodis, Pavol; Schwartz, Erik; Koepf, Matthieu; Cornelissen, Jeroen J L M; Rowan, Alan E; Nolte, Roeland J M; Woutersen, Sander

    2009-09-28

    Self-trapping of NH-stretch vibrational excitations in synthetic beta-sheet helices is observed using femtosecond infrared pump-probe spectroscopy. In a dialanine-based beta-sheet helix, the transient-absorption change upon exciting the NH-stretch mode exhibits a negative absorption change at the fundamental frequency and two positive peaks at lower frequencies. These two induced-absorption peaks are characteristic for a state in which the vibrational excitation is self-trapped on essentially a single NH-group in the hydrogen-bonded NH...OC chain, forming a small (Holstein) vibrational polaron. By engineering the structure of the polymer we can disrupt the hydrogen-bonded NH...OC chain, allowing us to eliminate the self-trapping, as is confirmed from the NH-stretch pump-probe response. We also investigate a trialanine-based beta-sheet helix, where each side chain participates in two NH...OC chains with different hydrogen-bond lengths. The chain with short hydrogen bonds shows the same self-trapping behavior as the dialanine-based beta-sheet helix, whereas in the chain with long hydrogen bonds the self-trapping is too weak to be observable. PMID:19791890

  13. Vibrational self-trapping in beta-sheet structures observed with femtosecond nonlinear infrared spectroscopy

    Science.gov (United States)

    Bodis, Pavol; Schwartz, Erik; Koepf, Matthieu; Cornelissen, Jeroen J. L. M.; Rowan, Alan E.; Nolte, Roeland J. M.; Woutersen, Sander

    2009-09-01

    Self-trapping of NH-stretch vibrational excitations in synthetic β-sheet helices is observed using femtosecond infrared pump-probe spectroscopy. In a dialanine-based β-sheet helix, the transient-absorption change upon exciting the NH-stretch mode exhibits a negative absorption change at the fundamental frequency and two positive peaks at lower frequencies. These two induced-absorption peaks are characteristic for a state in which the vibrational excitation is self-trapped on essentially a single NH-group in the hydrogen-bonded NH⋯OC chain, forming a small (Holstein) vibrational polaron. By engineering the structure of the polymer we can disrupt the hydrogen-bonded NH⋯OC chain, allowing us to eliminate the self-trapping, as is confirmed from the NH-stretch pump-probe response. We also investigate a trialanine-based β-sheet helix, where each side chain participates in two NH⋯OC chains with different hydrogen-bond lengths. The chain with short hydrogen bonds shows the same self-trapping behavior as the dialanine-based β-sheet helix, whereas in the chain with long hydrogen bonds the self-trapping is too weak to be observable.

  14. Sum Frequency Generation Vibrational Spectroscopy of Colloidal Platinum Nanoparticle Catalysts: Disordering versus Removal of Organic Capping

    KAUST Repository

    Krier, James M.

    2012-08-23

    Recent work with nanoparticle catalysts shows that size and shape control on the nanometer scale influences reaction rate and selectivity. Sum frequency generation (SFG) vibrational spectroscopy is a powerful tool for studying heterogeneous catalysis because it enables the observation of surface intermediates during catalytic reactions. To control the size and shape of catalytic nanoparticles, an organic ligand was used as a capping agent to stabilize nanoparticles during synthesis. However, the presence of an organic capping agent presents two major challenges in SFG and catalytic reaction studies: it blocks a significant fraction of active surface sites and produces a strong signal that prevents the detection of reaction intermediates with SFG. Two methods for cleaning Pt nanoparticles capped with poly (vinylpyrrolidone) (PVP) are examined in this study: solvent cleaning and UV cleaning. Solvent cleaning leaves more PVP intact and relies on disordering with hydrogen gas to reduce the SFG signal of PVP. In contrast, UV cleaning depends on nearly complete removal of PVP to reduce SFG signal. Both UV and solvent cleaning enable the detection of reaction intermediates by SFG. However, solvent cleaning also yields nanoparticles that are stable under reaction conditions, whereas UV cleaning results in aggregation during reaction. The results of this study indicate that solvent cleaning is more advantageous for studying the effects of nanoparticle size and shape on catalytic selectivity by SFG vibrational spectroscopy. © 2012 American Chemical Society.

  15. Far-field nanoscale infrared spectroscopy of vibrational fingerprints of molecules with graphene plasmons

    Science.gov (United States)

    Hu, Hai; Yang, Xiaoxia; Zhai, Feng; Hu, Debo; Liu, Ruina; Liu, Kaihui; Sun, Zhipei; Dai, Qing

    2016-01-01

    Infrared spectroscopy, especially for molecular vibrations in the fingerprint region between 600 and 1,500 cm−1, is a powerful characterization method for bulk materials. However, molecular fingerprinting at the nanoscale level still remains a significant challenge, due to weak light–matter interaction between micron-wavelengthed infrared light and nano-sized molecules. Here we demonstrate molecular fingerprinting at the nanoscale level using our specially designed graphene plasmonic structure on CaF2 nanofilm. This structure not only avoids the plasmon–phonon hybridization, but also provides in situ electrically-tunable graphene plasmon covering the entire molecular fingerprint region, which was previously unattainable. In addition, undisturbed and highly confined graphene plasmon offers simultaneous detection of in-plane and out-of-plane vibrational modes with ultrahigh detection sensitivity down to the sub-monolayer level, significantly pushing the current detection limit of far-field mid-infrared spectroscopies. Our results provide a platform, fulfilling the long-awaited expectation of high sensitivity and selectivity far-field fingerprint detection of nano-scale molecules for numerous applications. PMID:27460765

  16. Far-field nanoscale infrared spectroscopy of vibrational fingerprints of molecules with graphene plasmons

    Science.gov (United States)

    Hu, Hai; Yang, Xiaoxia; Zhai, Feng; Hu, Debo; Liu, Ruina; Liu, Kaihui; Sun, Zhipei; Dai, Qing

    2016-07-01

    Infrared spectroscopy, especially for molecular vibrations in the fingerprint region between 600 and 1,500 cm-1, is a powerful characterization method for bulk materials. However, molecular fingerprinting at the nanoscale level still remains a significant challenge, due to weak light-matter interaction between micron-wavelengthed infrared light and nano-sized molecules. Here we demonstrate molecular fingerprinting at the nanoscale level using our specially designed graphene plasmonic structure on CaF2 nanofilm. This structure not only avoids the plasmon-phonon hybridization, but also provides in situ electrically-tunable graphene plasmon covering the entire molecular fingerprint region, which was previously unattainable. In addition, undisturbed and highly confined graphene plasmon offers simultaneous detection of in-plane and out-of-plane vibrational modes with ultrahigh detection sensitivity down to the sub-monolayer level, significantly pushing the current detection limit of far-field mid-infrared spectroscopies. Our results provide a platform, fulfilling the long-awaited expectation of high sensitivity and selectivity far-field fingerprint detection of nano-scale molecules for numerous applications.

  17. Vibrational Spectroscopy of Chemical Species in Silicon and Silicon-Rich Nitride Thin Films

    Directory of Open Access Journals (Sweden)

    Kirill O. Bugaev

    2012-01-01

    Full Text Available Vibrational properties of hydrogenated silicon-rich nitride (SiN:H of various stoichiometry (0.6≤≤1.3 and hydrogenated amorphous silicon (a-Si:H films were studied using Raman spectroscopy and Fourier transform infrared spectroscopy. Furnace annealing during 5 hours in Ar ambient at 1130∘C and pulse laser annealing were applied to modify the structure of films. Surprisingly, after annealing with such high-thermal budget, according to the FTIR data, the nearly stoichiometric silicon nitride film contains hydrogen in the form of Si–H bonds. From analysis of the FTIR data of the Si–N bond vibrations, one can conclude that silicon nitride is partly crystallized. According to the Raman data a-Si:H films with hydrogen concentration 15% and lower contain mainly Si–H chemical species, and films with hydrogen concentration 30–35% contain mainly Si–H2 chemical species. Nanosecond pulse laser treatments lead to crystallization of the films and its dehydrogenization.

  18. Vibrational Sum Frequency Generation Spectroscopy Study of Hydrous Species in Soda Lime Silica Float Glass.

    Science.gov (United States)

    Luo, Jiawei; Banerjee, Joy; Pantano, Carlo G; Kim, Seong H

    2016-06-21

    It is generally accepted that the mechanical properties of soda lime silica (SLS) glass can be affected by the interaction between sodium ions and hydrous species (silanol groups and water molecules) in its surface region. While the amount of these hydrous species can be estimated from hydrogen profiles and infrared spectroscopy, their chemical environment in the glass network is still not well understood. This work employed vibrational sum frequency generation (SFG) spectroscopy to investigate the chemical environment of hydrous species in the surface region of SLS float glass. SLS float glass shows sharp peaks in the OH stretching vibration region in SFG spectra, while the OH stretch peaks of glasses that do not have leachable sodium ions and the OH peaks of water molecules in condensed phases are normally broad due to fast hydrogen bonding dynamics. The hydrous species responsible for the sharp SFG peaks for the SLS float glass were found to be thermodynamically more stable than physisorbed water molecules, did not exchange with D2O, and were associated with the sodium concentration gradient in the dealkalized subsurface region. These results suggested that the hydrous species reside in static solvation shells defined by the silicate network with relatively slow hydrogen bonding dynamics, compared to physisorbed water layers on top of the glass surface. A putative radial distribution of the hydrous species within the SLS glass network was estimated based on the OH SFG spectral features, which could be compared with theoretical distributions calculated from computational simulations. PMID:27254814

  19. The Molecular Surface Structure of Ammonium and Potassium Dinitramide : A Vibrational Sum Frequency Spectroscopy and Quantum Chemical Study

    OpenAIRE

    Rahm, Martin; Tyrode, Eric; Brinck, Tore; Johnson, Magnus

    2011-01-01

    Vibrational sum frequency spectroscopy (VSFS) and quantum chemical modeling have been employed to investigate the molecular surface structure of ammonium and potassium dinitramide (ADN and KDN) crystals. Identification of key vibrational modes was made possible by performing density functional theory calculations of molecular clusters. The surface of KDN was found to be partly covered with a thin layer of the decomposition product KNO3, which due to its low thickness was not detectable by inf...

  20. Vibrational spectroscopy of functional group chemistry and arsenate coordination in ettringite

    Science.gov (United States)

    Myneni, Satish C. B.; Traina, Samuel J.; Waychunas, Glenn A.; Logan, Terry J.

    1998-11-01

    The functional group chemistry and coordination of AsO 43--sorption complexes in ettringite [Ca 6Al 2(SO 4) 3(OH) 12·26H 2O] were evaluated as a function of sorption type (adsorption, coprecipitation) and pH using Raman and Fourier Transform infrared (FTIR) spectroscopies. The reactive functional groups of ettringite, ≡Al-OH, ≡Ca-OH 2, and ≡Ca 2-OH exhibit broad overlapping OH bands in the range 3600-3200 cm -1, prohibiting separation of component vibrational bands. The SO 42- polyhedra of the channels are present in three crystallographically different sites and exhibit weakly split S-O asymmetric stretch at 1136 cm -1 (with several components) and symmetric stretch at 1016, 1008, and 989 cm -1. During AsO 43- adsorption, the vibrational spectra of SO 42- were least affected, and the OH stretching intensities around 3600 cm -1 decreased with an increase in AsO 43- sorption. In contrast, the S-O symmetric stretch at 1016 and 1008 cm -1 were almost completely removed, and the OH vibrations were relatively unaffected during AsO 43--coprecipitation. The As-O asymmetric stretch of sorbed AsO 43- are split and occur as overlapping peaks around 870 cm -1. The As-O complexed stretching vibrations are at ˜800 cm -1. The low pH samples (pH = 10.3-11.0) exhibit distinct As-OH stretching vibrations at 748 cm -1, indicating that some of the sorbed AsO 43- ions are protonated. These spectral features demonstrate that AsO 43- directly interacts with ettringite surface sites during adsorption and substitute inside the channels during coprecipitation (preferentially for two of the three sites). The energy position of the As-O symmetric stretch vibrations suggest that the AsO 43- polyhedra interacts predominantly with ≡Ca-OH 2 and ≡Ca 2-OH sites rather than with ≡Al-OH sites. Sorption of more than one type of As species was evident in low pH (<11.0) samples.

  1. Nonlinear spectroscopy of superconducting anharmonic resonators

    CERN Document Server

    DiVincenzo, David P

    2011-01-01

    We formulate a model for the steady state response of a nonlinear quantum oscillator structure, such as those used in a variety of superconducting qubit experiments, when excited by a steady, but not necessarily small, ac tone. We show that this model can be derived directly from a circuit description of some recent qubit experiments in which the state of the qubit is read out directly, without a SQUID magnetometer. The excitation profile has a rich structure depending on the detuning of the tone from the small-signal resonant frequency, on the degree of damping, and on the excitation amplitude. We explore two regions in detail: First, at high damping there is a trough in the excitation response as a function of detuning, near where the classical Duffing bifurcation occurs. This trough has been understood as a classical interference between two metastable responses with opposite phase. We use Wigner function studies to show that while this picture is roughly correct, there are also more quantum mechanical asp...

  2. Nonlinear spectroscopy of superconducting anharmonic resonators

    International Nuclear Information System (INIS)

    We formulate a model for the steady state response of a nonlinear quantum oscillator structure, such as those used in a variety of superconducting qubit experiments, when excited by a steady, but not necessarily small, ac tone. We show that this model can be derived directly from a circuit description of some recent qubit experiments in which the state of the qubit is read out directly, without a superconducting quantum interference device (SQUID) magnetometer. The excitation profile has a rich structure depending on the detuning of the tone from the small-signal resonant frequency, on the degree of damping and on the excitation amplitude. We explore two regions in detail. Firstly, at high damping there is a trough in the excitation response as a function of detuning, near where the classical Duffing bifurcation occurs. This trough has been understood as a classical interference between two metastable responses with opposite phase. We use Wigner function studies to show that while this picture is roughly correct, there are also more quantum mechanical aspects to this feature. Secondly, at low damping we study the emergence of sharp, discrete spectral features from a continuum response. We show that these the structures, associated with discrete transitions between different excited-state eigenstates of the oscillator, provide an interesting example of a quantum Fano resonance. The trough in the Fano response evolves continuously from the ‘classical’ trough at high damping. (paper)

  3. Anharmonicity and hydrogen bonding in electrooptic sucrose crystal

    Science.gov (United States)

    Szostak, M. M.; Giermańska, J.

    1990-03-01

    The polarized absorption spectra of the sucrose crystal in the 5300 - 7300 cm -1 region have been measured. The assignments of all the eight OH stretching overtones are proposed and their mechanical anharmonicities are estimated. The discrepancies from the oriented gas model (OGM) in the observed relative band intensities, especially of the -CH vibrations, are assumed to be connected with vibronic couplings enhanced by the helical arrangement of molecules joined by hydrogen bondings. It seems that this kind of interactions might be important for the second harmonic generation (SHG) by the sucrose crystal.

  4. The Application of Vibrational Spectroscopy Techniques in the Qualitative Assessment of Material Traded as Ginseng

    Directory of Open Access Journals (Sweden)

    Maxleene Sandasi

    2016-04-01

    Full Text Available The name “ginseng” is collectively used to describe several plant species, including Panax ginseng (Asian/Oriental ginseng, P. quinquefolius (American ginseng, P. pseudoginseng (Pseudoginseng and Eleutherococcus senticosus (Siberian ginseng, each with different applications in traditional medicine practices. The use of a generic name may lead to the interchangeable use or substitution of raw materials which poses quality control challenges. Quality control methods such as vibrational spectroscopy-based techniques are here proposed as fast, non-destructive methods for the distinction of four ginseng species and the identification of raw materials in commercial ginseng products. Certified ginseng reference material and commercial products were analysed using hyperspectral imaging (HSI, mid-infrared (MIR and near-infrared (NIR spectroscopy. Principal component analysis (PCA and (orthogonal partial least squares discriminant analysis models (OPLS-DA were developed using multivariate analysis software. UHPLC-MS was used to analyse methanol extracts of the reference raw materials and commercial products. The holistic analysis of ginseng raw materials revealed distinct chemical differences using HSI, MIR and NIR. For all methods, Eleutherococcus senticosus displayed the greatest variation from the three Panax species that displayed closer chemical similarity. Good discrimination models with high R2X and Q2 cum vales were developed. These models predicted that the majority of products contained either /P. ginseng or P. quinquefolius. Vibrational spectroscopy and HSI techniques in tandem with multivariate data analysis tools provide useful alternative methods in the authentication of ginseng raw materials and commercial products in a fast, easy, cost-effective and non-destructive manner.

  5. The Application of Vibrational Spectroscopy Techniques in the Qualitative Assessment of Material Traded as Ginseng.

    Science.gov (United States)

    Sandasi, Maxleene; Vermaak, Ilze; Chen, Weiyang; Viljoen, Alvaro

    2016-01-01

    The name "ginseng" is collectively used to describe several plant species, including Panax ginseng (Asian/Oriental ginseng), P. quinquefolius (American ginseng), P. pseudoginseng (Pseudoginseng) and Eleutherococcus senticosus (Siberian ginseng), each with different applications in traditional medicine practices. The use of a generic name may lead to the interchangeable use or substitution of raw materials which poses quality control challenges. Quality control methods such as vibrational spectroscopy-based techniques are here proposed as fast, non-destructive methods for the distinction of four ginseng species and the identification of raw materials in commercial ginseng products. Certified ginseng reference material and commercial products were analysed using hyperspectral imaging (HSI), mid-infrared (MIR) and near-infrared (NIR) spectroscopy. Principal component analysis (PCA) and (orthogonal) partial least squares discriminant analysis models (OPLS-DA) were developed using multivariate analysis software. UHPLC-MS was used to analyse methanol extracts of the reference raw materials and commercial products. The holistic analysis of ginseng raw materials revealed distinct chemical differences using HSI, MIR and NIR. For all methods, Eleutherococcus senticosus displayed the greatest variation from the three Panax species that displayed closer chemical similarity. Good discrimination models with high R²X and Q² cum vales were developed. These models predicted that the majority of products contained either /P. ginseng or P. quinquefolius. Vibrational spectroscopy and HSI techniques in tandem with multivariate data analysis tools provide useful alternative methods in the authentication of ginseng raw materials and commercial products in a fast, easy, cost-effective and non-destructive manner. PMID:27077839

  6. Are giant resonances harmonic vibrations?

    International Nuclear Information System (INIS)

    Giant resonances are understood as the first quantum of collective vibrations. The non-linear response of a quantum anharmonic oscillator is investigated as a model for the excitation of giant resonances in heavy ion collisions. It is shown that the introduction of small anharmonicities and non-linearities can double the predicted cross section for the excitation of the two-phonon states. (R.P.)

  7. Geometry determination of complexes in a molecular liquid mixture using Electron-Vibration-Vibration two-dimensional infrared spectroscopy with a vibrational transition density cube method

    OpenAIRE

    Guo, Rui; Mukamel, Shaul; Klug, David R.

    2012-01-01

    We demonstrate the use of a new vibrational transition density cube (VTDC) method for determining the geometry of complexes in a molecular liquid mixture from electron-vibration-vibration two-dimensional infrared (EVV 2DIR) spectra. The VTDC method was used to calculate the electrically-mediated intermolecular vibrational coupling and thereby the EVV 2DIR spectra. Using the 1:1 benzonitrile-phenylacetylene liquid mixture as a test case, the new method leads to a distance of 3.60 Å between the...

  8. Vibrational properties of epitaxial Bi4Te3 films as studied by Raman spectroscopy

    International Nuclear Information System (INIS)

    Bi4Te3, as one of the phases of the binary Bi–Te system, shares many similarities with Bi2Te3, which is known as a topological insulator and thermoelectric material. We report the micro-Raman spectroscopy study of 50 nm Bi4Te3 films on Si substrates prepared by molecular beam epitaxy. Raman spectra of Bi4Te3 films completely resolve the six predicted Raman-active phonon modes for the first time. Structural features and Raman tensors of Bi4Te3 films are introduced. According to the wavenumbers and assignments of the six eigenpeaks in the Raman spectra of Bi4Te3 films, it is found that the Raman-active phonon oscillations in Bi4Te3 films exhibit the vibrational properties of those in both Bi and Bi2Te3 films

  9. Vibrational properties of epitaxial Bi4Te3 films as studied by Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Hao Xu

    2015-08-01

    Full Text Available Bi4Te3, as one of the phases of the binary Bi–Te system, shares many similarities with Bi2Te3, which is known as a topological insulator and thermoelectric material. We report the micro-Raman spectroscopy study of 50 nm Bi4Te3 films on Si substrates prepared by molecular beam epitaxy. Raman spectra of Bi4Te3 films completely resolve the six predicted Raman-active phonon modes for the first time. Structural features and Raman tensors of Bi4Te3 films are introduced. According to the wavenumbers and assignments of the six eigenpeaks in the Raman spectra of Bi4Te3 films, it is found that the Raman-active phonon oscillations in Bi4Te3 films exhibit the vibrational properties of those in both Bi and Bi2Te3 films.

  10. Exchanging conformations of a hydroformylation catalyst structurally characterized using two-dimensional vibrational spectroscopy.

    Science.gov (United States)

    Panman, Matthijs R; Vos, Jannie; Bocokić, Vladica; Bellini, Rosalba; de Bruin, Bas; Reek, Joost H N; Woutersen, Sander

    2013-12-16

    Catalytic transition-metal complexes often occur in several conformations that exchange rapidly (vibrational spectroscopy, a method that can be applied to any catalyst provided that the exchange between its conformers occurs on a time scale of a few picoseconds or slower. We find that, in one of the conformations, the OC-Rh-CO angle deviates significantly from the canonical value in a trigonal-bipyramidal structure. On the basis of complementary density functional calculations, we ascribe this effect to attractive van der Waals interaction between the CO and the xantphos ligand. PMID:24256078

  11. Theoretical study of sum-frequency vibrational spectroscopy on limonene surface

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Ren-Hui, E-mail: zrh@iccas.ac.cn; Liu, Hao; Jing, Yuan-Yuan; Wang, Bo-Yang; Shi, Qiang [Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190 (China); Wei, Wen-Mei [Department of Chemistry, College of Basic Medicine, Anhui Medical University, Hefei, Anhui 230032 (China)

    2014-03-14

    By combining molecule dynamics (MD) simulation and quantum chemistry computation, we calculate the surface sum-frequency vibrational spectroscopy (SFVS) of R-limonene molecules at the gas-liquid interface for SSP, PPP, and SPS polarization combinations. The distributions of the Euler angles are obtained using MD simulation, the ψ-distribution is between isotropic and Gaussian. Instead of the MD distributions, different analytical distributions such as the δ-function, Gaussian and isotropic distributions are applied to simulate surface SFVS. We find that different distributions significantly affect the absolute SFVS intensity and also influence on relative SFVS intensity, and the δ-function distribution should be used with caution when the orientation distribution is broad. Furthermore, the reason that the SPS signal is weak in reflected arrangement is discussed.

  12. Theoretical study of sum-frequency vibrational spectroscopy on limonene surface

    International Nuclear Information System (INIS)

    By combining molecule dynamics (MD) simulation and quantum chemistry computation, we calculate the surface sum-frequency vibrational spectroscopy (SFVS) of R-limonene molecules at the gas-liquid interface for SSP, PPP, and SPS polarization combinations. The distributions of the Euler angles are obtained using MD simulation, the ψ-distribution is between isotropic and Gaussian. Instead of the MD distributions, different analytical distributions such as the δ-function, Gaussian and isotropic distributions are applied to simulate surface SFVS. We find that different distributions significantly affect the absolute SFVS intensity and also influence on relative SFVS intensity, and the δ-function distribution should be used with caution when the orientation distribution is broad. Furthermore, the reason that the SPS signal is weak in reflected arrangement is discussed

  13. Description of cross peaks induced by intermolecular vibrational energy transfer in two-dimensional infrared spectroscopy

    CERN Document Server

    Villaeys, Albert A

    2013-01-01

    In the present work, the analytical description of an intermolecular vibrational energy transfer, analyzed by two dimensional infrared spectroscopy, is established. The energy transfer process takes place between the dark combination states of low frequency modes pertaining to different molecules. The appearance of the cross peaks results from coherent transfer between these combination states and an optically active state of the acceptor molecule. Such a process has recently been observed experimentally between the nitrile groups of acetonitrile-d3 and benzonitrile molecules. This molecular system will be used as a model for the simulations of their two-dimensional infrared spectra. The dependence of the cross-peak growth, which is a signature of the intermolecular energy transfer, will be discussed in detail as a function of the molecular dynamical constants.

  14. A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency

    Science.gov (United States)

    Guo, Yan-bo; Liu, Zi-zhong; Liu, Hong-xia; Zhang, Feng-ying; Yin, Jun-qing

    2016-07-01

    A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L = C, Si, Ge, n = 3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.0). There are high positive correlations between the theoretical calculated the NICS values and the value of the RSVRSF (A1g/A1‧) of the LnHn (L = C, Si, Ge, n = 3, 5-8). The bigger the aromatic degree, the bigger the RSVRSF is. The value of the RSVRSF is a new probe of aromaticity. Expectedly, it is predicted that the experimental determination of the aromatic degree can be achieved by the determination of the ring stretching vibration (A1g/A1‧) Raman spectrum frequencies for the aromatic target molecules.

  15. Metal-Catalyzed Chemical Reaction of Single Molecules Directly Probed by Vibrational Spectroscopy.

    Science.gov (United States)

    Choi, Han-Kyu; Park, Won-Hwa; Park, Chan-Gyu; Shin, Hyun-Hang; Lee, Kang Sup; Kim, Zee Hwan

    2016-04-01

    The study of heterogeneous catalytic reactions remains a major challenge because it involves a complex network of reaction steps with various intermediates. If the vibrational spectra of individual molecules could be monitored in real time, one could characterize the structures of the intermediates and the time scales of reaction steps without ensemble averaging. Surface-enhanced Raman scattering (SERS) spectroscopy does provide vibrational spectra with single-molecule sensitivity, but typical single-molecule SERS signals exhibit spatial heterogeneities and temporal fluctuations, making them difficult to be used in single-molecule kinetics studies. Here we show that SERS can monitor the single-molecule catalytic reactions in real time. The surface-immobilized reactants placed at the junctions of well-defined nanoparticle-thin film structures produce time-resolved SERS spectra with discrete, step-transitions of photoproducts. We interpret that such SERS-steps correspond to the reaction events of individual molecules occurring at the SERS hotspot. The analyses of the yield, dynamics, and the magnitude of such SERS steps, along with the associated spectral characteristics, fully support our claim. In addition, a model that is based on plasmonic field enhancement and surface photochemistry reproduces the key features of experimental observation. Overall, the result demonstrates that it is possible, under well-controlled conditions, to differentiate the chemical and physical processes contributing to the single-molecule SERS signals, and thus shows the use of single-molecule SERS as a tool for studying the metal-catalyzed organic reactions. PMID:26964567

  16. A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency.

    Science.gov (United States)

    Guo, Yan-Bo; Liu, Zi-Zhong; Liu, Hong-Xia; Zhang, Feng-Ying; Yin, Jun-Qing

    2016-07-01

    A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L=C, Si, Ge, n=3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.0). There are high positive correlations between the theoretical calculated the NICS values and the value of the RSVRSF (A1g/A1') of the LnHn (L=C, Si, Ge, n=3, 5-8). The bigger the aromatic degree, the bigger the RSVRSF is. The value of the RSVRSF is a new probe of aromaticity. Expectedly, it is predicted that the experimental determination of the aromatic degree can be achieved by the determination of the ring stretching vibration (A1g/A1') Raman spectrum frequencies for the aromatic target molecules. PMID:27085169

  17. Observation of the low frequency vibrational modes of bacteriophage M13 in water by Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Tsen Shaw-Wei D

    2006-09-01

    Full Text Available Abstract Background Recently, a technique which departs radically from conventional approaches has been proposed. This novel technique utilizes biological objects such as viruses as nano-templates for the fabrication of nanostructure elements. For example, rod-shaped viruses such as the M13 phage and tobacco mosaic virus have been successfully used as biological templates for the synthesis of semiconductor and metallic nanowires. Results and discussion Low wave number (≤ 20 cm-1 acoustic vibrations of the M13 phage have been studied using Raman spectroscopy. The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode has been shown to belong to one of the Raman-active axial torsion modes of the M13 phage protein coat. Conclusion It is expected that the detection and characterization of this low frequency vibrational mode can be used for applications in nanotechnology such as for monitoring the process of virus functionalization and self-assembly. For example, the differences in Raman spectra can be used to monitor the coating of virus with some other materials and nano-assembly process, such as attaching a carbon nanotube or quantum dots.

  18. From Vibrational Spectroscopy to Force Fields and Structures of Saccharides: New Computational Algorithms and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Pincu, Madeleine [UCI; Gerber, Robert Benny [Professor, UCI, Chemistry Dept.

    2013-07-17

    This work was undertaken with the main objective to investigate basic reactions that take place in relatively simple saccharides (mono-saccharides and cellobiose - the building block of cellulose) , in isolation and in cluster with few water molecules or with (gas-phase) clusters of few waters and ionic compounds (salt, isolated ions like H{sup +} or OH{sup -}). Within the context of this work, different potentials were investigated; among them, were the PM3 semi empirical potential, DFT/BLYP and a new hybrid potential constructed from MP2 for the harmonic part and from adjusted Hartree-Fock anharmonic interactions (VSCF-PT2). These potentials were evaluated by comparison with experimental data from published sources and from several collaborating groups. The findings show excellent agreement between experiments and predictions with the hybrid VSCF-PT2 potential and very good agreement with predictions obtained from dynamics with dispersion corrected DFT/BLYP potential. Investigation of hydration of cellobiose, was another topic of interest. Guided by a hydration motif demonstrated by our experimental collaborators (team of Prof J.P. Simons), we demonstrated large energetic and structural differences between the two species of cellobiose: cis and trans. The later, which is dominant in solid and liquid phases, is higher in energy in the gas-phase and compared to pure water, it does not disturb as much the network of H bonds. In contrast, the cis species exhibits asymmetric hydration in cluster with up to 25 waters, indicating that it has surfactant properties. Another highlight of this research effort was the successful first time spectrometric and spectroscopic study of a gas-phase protonated sugar derivative (alpha-D-Galactopyranoside) and its interpretation by Ab Initio molecular dynamics (AIMD) simulations. The findings demonstrate the formation of a motif in which a proton bridges between two Oxygen atoms (belonging to OH groups) at the sugar; The vibrational

  19. On the Applicability of the Caldeira-Leggett Model to Condensed Phase Vibrational Spectroscopy

    CERN Document Server

    Ivanov, Sergei D; Kühn, Oliver

    2014-01-01

    Formulating a rigorous system-bath partitioning approach remains an open issue. In this context the famous Caldeira-Leggett (CL) model that enables quantum and classical treatment of Brownian motion on equal footing has enjoyed popularity. Although this model is by any means a useful theoretical tool, its validity for describing anharmonic dynamics of real systems is often taken for granted. In this Letter we show that the model is not able to describe real systems unless the system part of the potential is taken effectively harmonic. We demonstrate that the deficiencies of the model are rooted in the anharmonicity. Further, we elaborate on the mathematical origin of the breakdown of the CL model.

  20. First-principles analysis of anharmonic nuclear motion and thermal transport in thermoelectric materials

    International Nuclear Information System (INIS)

    We show a first-principles approach for analyzing anharmonic properties of lattice vibrations in solids. We firstly extract harmonic and anharmonic force constants from accurate first-principles calculations based on the density functional theory. Using the many-body perturbation theory of phonons, we then estimate the phonon scattering probability due to anharmonic phonon-phonon interactions. We show the validity of the approach by computing the lattice thermal conductivity of Si, a typical covalent semiconductor, and selected thermoelectric materials PbTe and Bi2Te3 based on the Boltzmann transport equation. We also show that the phonon lifetime and the lattice thermal conductivity of the high-temperature phase of SrTiO3 can be estimated by employing the perturbation theory on top of the solution of the self-consistent phonon equation

  1. First-principles analysis of anharmonic nuclear motion and thermal transport in thermoelectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Tadano, Terumasa [Department of Applied Physics, The University of Tokyo, Tokyo 113-8656 (Japan); Tsuneyuki, Shinji [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan); Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581 (Japan)

    2015-12-31

    We show a first-principles approach for analyzing anharmonic properties of lattice vibrations in solids. We firstly extract harmonic and anharmonic force constants from accurate first-principles calculations based on the density functional theory. Using the many-body perturbation theory of phonons, we then estimate the phonon scattering probability due to anharmonic phonon-phonon interactions. We show the validity of the approach by computing the lattice thermal conductivity of Si, a typical covalent semiconductor, and selected thermoelectric materials PbTe and Bi{sub 2}Te{sub 3} based on the Boltzmann transport equation. We also show that the phonon lifetime and the lattice thermal conductivity of the high-temperature phase of SrTiO{sub 3} can be estimated by employing the perturbation theory on top of the solution of the self-consistent phonon equation.

  2. Infrared spectroscopy of methoxyphenols involved as atmospheric secondary organic aerosol precursors: Gas-phase vibrational cross-sections

    Science.gov (United States)

    Cuisset, A.; Coeur, C.; Mouret, G.; Ahmad, W.; Tomas, A.; Pirali, O.

    2016-08-01

    Methoxyphenols are emitted in the atmosphere from biomass burning and recent works have shown the potential role of these oxygenated aromatic species in the formation of secondary organic aerosols. IR spectroscopic data that would enable their remote measurement in the atmosphere remain scarce in the literature. Room temperature Far-IR cross-sections of 4 methoxyphenols (2-methoxyphenol or guaiacol, 3-methoxyphenol, 4-methoxyphenol and 2,6-dimethoxyphenol or syringol) have been determined using the THz synchrotron radiation available at SOLEIL. Mid- and near-IR regions have also been investigated with a conventional Fourier transform IR setup and allowed to provide a set of vibrational cross-sections of the studied methoxyphenols. Finally, gas-phase cross sections of two nitroguaiacol isomers (4-nitroguaiacol and 5-nitroguaiacol), two intermediate products involved in the formation of secondary organic aerosols have been measured in the mid- and near-IR with a heated multi-pass cell. Harmonic and anharmonic density functional theory calculations were carried out for all the studied compounds and allowed a full assignment of the recorded rovibrational bands.

  3. Spectroscopy of isolated PTCDA molecules on the KCl(100) surface: Vibrational spectra and azimuthal orientation

    Science.gov (United States)

    Müller, Mathias; Paulheim, Alexander; Marquardt, Christian; Sokolowski, Moritz

    2013-02-01

    Small amounts of the model molecule perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) were vacuum deposited on epitaxial KCl films on Ag(100). The use of a low substrate temperature (20 K) during deposition hampered molecular diffusion resulting in isolated monomers on the surface. Fluorescence and fluorescence excitation spectroscopy performed on these monomers yielded highly resolved spectra with narrow lines corresponding to individual vibronic modes. This high resolution in our spectra is caused by a very small inhomogeneous broadening due to well-defined adsorption sites of the molecule on the substrate. Indeed, by polarization dependent fluorescence spectroscopy we show that the flat-lying molecules exhibit a preferred azimuthal orientation on the surface, the long molecular axis being oriented along the [011] or the equivalent [0bar{1}1] direction of the substrate. Furthermore, the high resolution in the spectra allowed a detailed analysis of the vibronic modes. The vibrational modes of the adsorbed molecule are very similar to those of the free PTCDA molecule, but due to the presence of the substrate additional low energy modes which are relevant for the full understanding of the spectra couple to the transition.

  4. Characterizing interstate vibrational coherent dynamics of surface adsorbed catalysts by fourth-order 3D SFG spectroscopy

    Science.gov (United States)

    Li, Yingmin; Wang, Jiaxi; Clark, Melissa L.; Kubiak, Clifford P.; Xiong, Wei

    2016-04-01

    We report the first fourth-order 3D SFG spectroscopy of a monolayer of the catalyst Re(diCN-bpy)(CO)3Cl on a gold surface. Besides measuring the vibrational coherences of single vibrational modes, the fourth-order 3D SFG spectrum also measures the dynamics of interstate coherences and vibrational coherences states between two vibrational modes. By comparing the 3D SFG to the corresponding 2D and third-order 3D IR spectroscopy of the same molecules in solution, we found that the interstate coherences exist in both liquid and surface systems, suggesting that the interstate coherence is not disrupted by surface interactions. However, by analyzing the 3D spectral lineshape, we found that the interstate coherences also experience non-negligible homogenous dephasing dynamics that originate from surface interactions. This unique ability of determining interstate vibrational coherence dynamics of the molecular monolayer can help in understanding of how energy flows within surface catalysts and other molecular monolayers.

  5. Ultrafast dynamics in iron tetracarbonyl olefin complexes investigated with two-dimensional vibrational spectroscopy.

    Science.gov (United States)

    Panman, Matthijs R; Newton, Arthur C; Vos, Jannie; van den Bosch, Bart; Bocokić, Vladica; Reek, Joost N H; Woutersen, Sander

    2013-01-28

    The dynamics of iron tetracarbonyl olefin complexes has been investigated using two-dimensional infrared (2D-IR) spectroscopy. Cross peaks between all CO-stretching bands show that the CO-stretch modes are coupled, and from the cross-peak anisotropies we can confirm previous assignments of the absorption bands. From the pump-probe delay dependence of the diagonal peaks in the 2D-IR spectrum we obtain a correlation time of ∼3 ps for the spectral fluctuations of the CO-stretch modes. We observe a multi-exponential pump-probe delay dependence of the cross-peak intensities, with rate constants ranging from 0.1 ps(-1) to 0.6 ps(-1). To determine whether this delay dependence originates from fluxionality of the complex or from intramolecular vibrational relaxation (IVR), we modulate the free-energy barrier of fluxional rearrangement by varying the pi-backbonding capacities of the olefin ligand in two iron tetracarbonyl olefin complexes: Fe(CO)(4)(cinnamic acid) and Fe(CO)(4)(dimethyl fumarate). Since the pi-backbonding strongly influences the rate of fluxionality, comparing the dynamics in the two complexes allows us to determine to what extent the observed dynamics is caused by fluxionality. We conclude that on the time scale of our experiments (up to 100 ps) the cross-peak dynamics in the iron complexes is determined by intramolecular vibrational energy relaxation. Hence, in contrast to previously investigated irontricarbonyl and ironpentacarbonyl complexes, iron tetracarbonyl olefin complexes exhibit no fluxionality on the picosecond time scale. PMID:23223560

  6. Nature of Asymmetry in the Vibrational Line Shape of Single-Molecule Inelastic Electron Tunneling Spectroscopy with the STM

    Science.gov (United States)

    Xu, Chen; Chiang, Chi-lun; Han, Zhumin; Ho, W.

    2016-04-01

    Single molecule vibrational spectroscopy and microscopy was demonstrated in 1998 by inelastic electron tunneling with the scanning tunneling microscope. To date, the discussion of its application has mainly focused on the spatial resolution and the spectral energy and intensity. Here we report on the vibrational line shape for a single carbon monoxide molecule that qualitatively exhibits inversion symmetry when it is transferred from the surface to the tip. The dependence of the line shape on the molecule's asymmetric couplings in the tunnel junction can be understood from theoretical simulation and further validates the mechanisms of inelastic electron tunneling.

  7. Raman and surface-enhanced Raman spectroscopy of amino acids and nucleotide bases for target bacterial vibrational mode identification

    Science.gov (United States)

    Guicheteau, Jason; Argue, Leanne; Hyre, Aaron; Jacobson, Michele; Christesen, Steven D.

    2006-05-01

    Raman and surface-enhanced Raman spectroscopy (SERS) studies of bacteria have reported a wide range of vibrational mode assignments associated with biological material. We present Raman and SER spectra of the amino acids phenylalanine, tyrosine, tryptophan, glutamine, cysteine, alanine, proline, methionine, asparagine, threonine, valine, glycine, serine, leucine, isoleucine, aspartic acid and glutamic acid and the nucleic acid bases adenosine, guanosine, thymidine, and uridine to better characterize biological vibrational mode assignments for bacterial target identification. We also report spectra of the bacteria Bacillus globigii, Pantoea agglomerans, and Yersinia rhodei along with band assignments determined from the reference spectra obtained.

  8. Surface vibrational relaxation of N2 studied by CO2 titration with time-resolved quantum cascade laser absorption spectroscopy

    International Nuclear Information System (INIS)

    A new method for determination of the wall de-excitation probability γN2 of vibrationally excited N2 on different surfaces exposed to low-pressure plasmas has been developed. A short dc discharge pulse of only a few milliseconds was applied to a mixture containing 0.05-1% of CO2 in N2 at a pressure of 133 Pa. Due to a nearly resonant fast vibrational transfer between N2(v) and the asymmetric ν3 mode of CO2 the vibrational excitation of these titrating molecules is an image of the degree of vibrational excitation of N2. In the afterglow, the vibrational relaxation of CO2 was monitored in situ using quantum cascade laser absorption spectroscopy. The experimental results were interpreted in terms of a numerical model of non-equilibrium vibrational kinetics in CO2-N2 mixtures. Heterogeneous relaxation was the main quenching process of N2(v) under the conditions of this study, which allowed determination of the value of γN2 from the best agreement between the experiment and the model. The new method is suitable for γN2 determination in a single plasma pulse with the discharge tube surface pretreated by a low-pressure plasma. The relaxation probability of the first vibrational level of nitrogen γ1 = (1.1 ± 0.15) × 10-3 found for Pyrex and silica is in reasonable agreement with the literature data. Using the new technique the N2(v = 1) quenching probability was measured on TiO2 surface, γ1 = (9 ± 1) × 10-3. A linear enhancement of the N2(v) wall deactivation probability with an increase in the admixture of CO2 was observed for all studied materials. In order to explain this effect, a vibrational energy transfer mechanism between N2(v) and adsorbed CO2 is proposed. (paper)

  9. Anharmonic resonances with recursive delay feedback

    OpenAIRE

    Goldobin, Denis S.

    2011-01-01

    We consider application of the multiple time delayed feedback for control of anharmonic (nonlinear) oscillators subject to noise. In contrast to the case of a single delay feedback, the multiple one exhibits resonances between feedback and nonlinear harmonics, leading to a resonantly strong or weak oscillation coherence even for a small anharmonicity. Analytical results are confirmed numerically for van der Pol and van der Pol-Duffing oscillators. Highlights: > We construct general theory of ...

  10. Methanol Perturbing Modeling Cell Membranes Investigated using Linear and Nonlinear Vibrational Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Kangzhen Tian; Hongchun Li; Shuji Ye

    2013-01-01

    Cell membranes play a crucial role in many biological functions of cells.A small change in the composition of cell membranes can strongly influence the functions of membrane-associated proteins,such as ion and water channels,and thus mediate the chemical and physical balance in cells.Such composition change could originate from the introduction of short-chain alcohols,or other anesthetics into membranes.In this work,we have applied sum frequency generation vibrational spectroscopy (SFG-VS),supplemented by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR),to investigate interaction between methanol and 1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine (d54-DMPC) lipid bilayers.Lipid's hydrocarbon interior is deuterated while its head group is hydrogenated.At the same time,CH3 symmetric stretch from methanol and lipid head amine group has different frequency,thus we can distinguish the behaviors of methanol,lipid head amine group,and lipid hydrocarbon interior.Based on the spectral feature of the bending mode of the water molecules replaced by methanol,we determined that the methanol molecules are intercalated into the region between amine and phosphate groups at the lipid hydrophilic head.The dipole of CH3 groups of methanol and lipid head,and the water O-H all adopt the same orientation directions.The introduction of methanol into the lipid hydrophilic head group can strongly perturb the entire length of the alkyl chains,resulting that the signals of CD2 and CD3 groups from both leaflets can not cancel each other.

  11. Anharmonicity effects in the frictionlike mode of graphite

    Science.gov (United States)

    Menéndez, C.; Lobato, A.; Abbasi-Pérez, D.; Fernández-Núñez, J.; Baonza, V. G.; Recio, J. M.

    2016-04-01

    Graphite is a prototypical solid lubricant demanding a thorough understanding of its low-friction behavior. The E2 g(1) Raman active vibrational mode of graphite is associated with the rigid-layer relative movement of its graphene sheets. Thus, this mode can provide a good means of exploring the low resistance of graphene layers to slip with respect to each other. To take advantage of this fact, the anharmonicity of the E2 g(1) mode has to be carefully characterized and evaluated since the atomic arrangement of carbon atoms in the ambient condition ABA stacking of graphite evidences potential asymmetry. The calculated one-dimensional energetic profile of the E2 g(1) mode reveals this local anisotropy around the energy minima and can be microscopically interpreted in terms of electron density interactions. Morse-type potentials accurately fit the energetic profiles at different interlayer separations, and provide simple analytical expressions for evaluating harmonic and anharmonic contributions to the Γ -point E2 g(1) frequency ωE2g(1 ) under a perturbative algebraic treatment. We quantify how the anharmonic contribution increases with the available energy (E ) at zero pressure, and how this contribution decreases as hydrostatic pressure (p ) or uniaxial stress is applied for a given available energy. The calculated ωE2g(1 )-p and ωE2g(1 )-E trends indicate an increasing (decreasing) of frictional forces in graphite with pressure (temperature). Our conclusions are supported by the good agreement of the calculated frequencies with existing Raman experiments under hydrostatic pressure conditions.

  12. Spatially resolved localized vibrational mode spectroscopy of carbon in liquid encapsulated Czochralski grown gallium arsenide wafers

    International Nuclear Information System (INIS)

    Substitutional carbon on an arsenic lattice site is the shallowest and one of the most dominant acceptors in semi-insulating Liquid Encapsulated Czochralski (LEC) GaAs. However, the role of this acceptor in determining the well known ''W'' shape spatial variation of neutral EL2 concentration along the diameter of a LEC wafer is not known. In this thesis, we attempt to clarify the issue of the carbon acceptor's effect on this ''W'' shaped variation by measuring spatial profiles of this acceptor along the radius of three different as-grown LEC GaAs wafers. With localized vibrational mode absorption spectroscopy, we find that the profile of the carbon acceptor is relatively constant along the radius of each wafer. Average values of concentration are 8 x 10E15 cm-3, 1.1 x 10E15 cm-3, and 2.2 x 10E15 cm-3, respectively. In addition, these carbon acceptor LVM measurements indicate that a residual donor with concentration comparable to carbon exists in these wafers and it is a good candidate for the observed neutral EL2 concentration variation. 22 refs., 39 figs

  13. Peptide conformational heterogeneity revealed from nonlinear vibrational spectroscopy and molecular-dynamics simulations

    Science.gov (United States)

    Woutersen, Sander; Pfister, Rolf; Hamm, Peter; Mu, Yuguang; Kosov, Daniel S.; Stock, Gerhard

    2002-10-01

    Nonlinear time-resolved vibrational spectroscopy is used to compare spectral broadening of the amide I band of the small peptide trialanine with that of N-methylacetamide, a commonly used model system for the peptide bond. In contrast to N-methylacetamide, the amide I band of trialanine is significantly inhomogeneously broadened. Employing classical molecular-dynamics simulations combined with density-functional-theory calculations, the origin of the spectral inhomogeneity is investigated. While both systems exhibit similar hydrogen-bonding dynamics, it is found that the conformational dynamics of trialanine causes a significant additional spectral broadening. In particular, transitions between the poly(Gly)II and the αR conformations are identified as the main source of the additional spectral inhomogeneity of trialanine. The experimental and computational results suggest that trialanine adopts essentially two conformations: poly(Gly)II (80%) and αR (20%). The potential of the joint experimental and computational approach to explore conformational dynamics of peptides is discussed.

  14. Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD(.).

    Science.gov (United States)

    Biesheuvel, J; Karr, J-Ph; Hilico, L; Eikema, K S E; Ubachs, W; Koelemeij, J C J

    2016-01-01

    The simplest molecules in nature, molecular hydrogen ions in the form of H2(+) and HD(+), provide an important benchmark system for tests of quantum electrodynamics in complex forms of matter. Here, we report on such a test based on a frequency measurement of a vibrational overtone transition in HD(+) by laser spectroscopy. We find that the theoretical and experimental frequencies are equal to within 0.6(1.1) parts per billion, which represents the most stringent test of molecular theory so far. Our measurement not only confirms the validity of high-order quantum electrodynamics in molecules, but also enables the long predicted determination of the proton-to-electron mass ratio from a molecular system, as well as improved constraints on hypothetical fifth forces and compactified higher dimensions at the molecular scale. With the perspective of comparisons between theory and experiment at the 0.01 part-per-billion level, our work demonstrates the potential of molecular hydrogen ions as a probe of fundamental physical constants and laws. PMID:26815886

  15. Localised vibrational mode spectroscopy studies of self-interstitial clusters in neutron irradiated silicon

    Energy Technology Data Exchange (ETDEWEB)

    Londos, C. A.; Antonaras, G. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece); Chroneos, A. [Materials Engineering, The Open University, Milton Keynes MK7 6AA (United Kingdom); Department of Materials, Imperial College, London SW7 2AZ (United Kingdom)

    2013-07-28

    The evolution of self-interstitial clusters in silicon (Si), produced by fast neutron irradiation of silicon crystals followed by anneals up to 750 °C, is investigated using localised vibrational mode spectroscopy. A band at 582 cm{sup −1} appears after irradiation and is stable up to 550 °C was attributed to small self-interstitial clusters (I{sub n}, n ≤ 4), with the most probable candidate the I{sub 4} structure. Two bands at 713 and 758 cm{sup −1} arising in the spectra upon annealing of the 582 cm{sup −1} band and surviving up to ∼750 °C were correlated with larger interstitial clusters (I{sub n}, 5 ≤ n ≤ 8), with the most probable candidate the I{sub 8} structure or/and with chainlike defects which are precursors of the (311) extended defects. The results illustrate the presence of different interstitial clusters I{sub n}, at the various temperature intervals of the material, in the course of an isochronal anneal sequence. As the annealing temperature increases, they evolve from first-order structures with a small number of self-interstitials (I{sub n}, n ≤ 4) for the temperatures 50 < T < 550 °C, to second order structures (I{sub n}, 5 ≤ n ≤ 8) with a larger number of interstitials, for the temperatures 550 < T < 750 °C.

  16. Chemometrics and vibrational spectroscopy as green tools for mine phytoremediation strategies

    Science.gov (United States)

    Mokgalaka-Matlala, N. S.; Regnier, T.; Combrinck, S.; Kouekam, C. R.; Weiersbye, I. M.

    This study describes the use of near infrared (NIR) spectroscopy in combination with chemometrics to characterise Combretum erythrophyllum plant material to determine differences in the chemical profiles of samples harvested from mine contaminated areas and those of natural populations. The chemometric computation of near infrared vibrational spectra was used to generate principal component analysis and partial least squares models. These models were used to determine seasonal differences in the chemical matrices of samples harvested from the mine sites with different levels of contamination. Principal component analysis scatter plots illustrated clustering of phenolic profiles of samples depending on whether they originated from contaminated or uncontaminated soils. A partial least squares model was developed to link the variations in the chemical composition and levels of contamination in all samples collected in the same season (autumn). The levels of total soluble phenolic compounds in leaf extracts of C. erythrophyllum were measured using the Folin-Ciocalteau assay. Data analysis of the samples revealed that plants harvested from mine sites, particularly in summer, produced a higher level of phenolic compounds than those of the natural population, thereby displaying a good correlation with the chemometric models.

  17. Rebinding dynamics of NO to microperoxidase-8 probed by time-resolved vibrational spectroscopy.

    Science.gov (United States)

    Lee, Taegon; Kim, Jooyoung; Park, Jaeheung; Pak, Youngshang; Kim, Hyojoon; Lim, Manho

    2016-02-21

    Femtosecond vibrational spectroscopy was used to probe the rebinding kinetics of NO to microperoxidase-8 (Mp), an ideal model system for the active site of ligand-binding heme proteins, including myoglobin and hemoglobin, after the photodeligation of MpNO in glycerol/water (G/W) solutions at 294 K. The geminate rebinding (GR) of NO to Mp in viscous solutions was highly efficient and ultrafast and negligibly dependent on the solution viscosity, which was adjusted by changing the glycerol content from 65% to 90% by volume in G/W mixtures. The kinetics of the GR of NO to Mp in viscous solutions was well represented by an exponential function with a time constant of ca. 11 ps. Although the kinetic traces of the GR of NO to Mp in solutions with three different viscosities (18, 81, and 252 cP) almost overlap, they show a slight difference early in the decay process. The kinetic traces were also described by the diffusion-controlled reaction theory with a Coulomb potential. Since the ligand is deligated in a neutral form, an ionic pair of NO(-) and Mp(+) may be produced before forming the Mp-NO bond by an electron transfer from Mp to NO as the deligated NO is sufficiently near to the Fe atom of Mp. The strong reactivity between NO and ferrous heme may arise from the Coulomb interaction between the reacting pair, which is consistent with the harpooning mechanism for NO binding to heme. PMID:26813691

  18. Vibrational Spectroscopy of Intramolecular Hydrogen Bonds in the Infrared and Near-Infrared Regions

    DEFF Research Database (Denmark)

    Schrøder, Sidsel Dahl

    This PhD thesis describes the gas phase studies of four intramolecular hydrogen bonds: O-H···O (in methyl lactate), O-H···π (in methallyl carbinol and allyl carbinol), O-H···N (in methylated and triuoromethylated 2-aminoethanol) and N-H···N (in the diamines 1,2-diaminoethane, 1,3-diaminopropane and...... 1,4-diaminobutane). Experimentally, the hydrogen bonds have been studied with vibrational spectroscopy in the infrared and near-infrared regions. The focus is primarily on spectra recorded in the near-infrared regions, which in these studies are dominated by O-H and N-H stretching overtones...... spectra. The experimental characterization of hydrogen bonds have been complemented by theoretical analyzes. These analyzes are based on the electron density topology, natural bond orbital theory and visualization of the distribution of electrostatic potential energy in the molecules. In these studies...

  19. Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD+

    CERN Document Server

    Biesheuvel, J; Hilico, L; Eikema, K S E; Ubachs, W; Koelemeij, J C J

    2016-01-01

    The simplest molecules in nature, molecular hydrogen ions in the form of H2+ and HD+, provide an important benchmark system for tests of quantum electrodynamics in complex forms of matter. Here, we report on such a test based on a frequency measurement of a vibrational overtone transition in HD+ by laser spectroscopy. We find that the theoretical and experimental frequencies are equal to within 0.6(1.1) parts per billion, which represents the most stringent test of molecular theory so far. Our measurement not only confirms the validity of high-order quantum electrodynamics in molecules, but also enables the long predicted determination of the proton-to-electron mass ratio from a molecular system, as well as improved constraints on hypothetical fifth forces and compactified higher dimensions at the molecular scale. With the perspective of comparisons between theory and experiment at the 0.01 part-per-billion level, our work demonstrates the potential of molecular hydrogen ions as a probe of fundamental physica...

  20. Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy

    Science.gov (United States)

    Ogata, Hideaki; Krämer, Tobias; Wang, Hongxin; Schilter, David; Pelmenschikov, Vladimir; van Gastel, Maurice; Neese, Frank; Rauchfuss, Thomas B.; Gee, Leland B.; Scott, Aubrey D.; Yoda, Yoshitaka; Tanaka, Yoshihito; Lubitz, Wolfgang; Cramer, Stephen P.

    2015-08-01

    The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique `wagging' mode involving H- motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe-CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H- binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe-H moieties in other important natural and synthetic catalysts.

  1. Resonant intermolecular transfer of vibrational energy in liquid water

    Science.gov (United States)

    Woutersen, Sander; Bakker, Huib J.

    1999-12-01

    Many biological, chemical and physical processes involve the transfer of energy. In the case of electronic excitations, transfer between molecules is rapid, whereas for vibrations in the condensed phase, resonant energy transfer is an unlikely process because the typical timescale of vibrational relaxation (a few picoseconds) is much shorter than that of resonant intermolecular vibrational energy transfer. For the OH-stretch vibration in liquid water, which is of particular importance due to its coupling to the hydrogen bond, extensive investigations have shown that vibrational relaxation takes place with a time constant of 740 +/- 25 femtoseconds (ref. 7). So for resonant intermolecular energy transfer to occur in liquid water, the interaction between the OH-stretch modes of different water molecules needs to be extremely strong. Here we report time-resolved pump-probe laser spectroscopy measurements that reveal the occurrence of fast resonant intermolecular transfer of OH-stretch excitations over many water molecules before the excitation energy is dissipated. We find that the transfer process is mediated by dipole-dipole interactions (the Förster transfer mechanism) and additional mechanisms that are possibly based on intermolecular anharmonic interactions involving hydrogen bonds. Our findings suggest that liquid water may play an important role in transporting vibrational energy between OH groups located on either different biomolecules or along extended biological structures. OH groups in a hydrophobic environment should accordingly be able to remain in a vibrationally excited state longer than OH groups in a hydrophilic environment.

  2. Infrared and Raman Vibrational Spectroscopies Reveal the Palette of Frescos Found in the Medieval Monastery of Karaach Teke

    International Nuclear Information System (INIS)

    Vibrational spectroscopy is applied on samples obtained from the excavation area of the medieval Monastery (10th century) of Karaach-Teke in Bulgaria. The results of the corresponding study, reveal the type of materials used for the creation of the wall-paintings and give evidence of Byzantine influence, a fact that further supports the well known impact of Byzantium on the technology and thematic-aesthetic features of iconography in Bulgaria during this era. In addition, the complementarity of FTIR and -Raman spectroscopies in the identification of pigments is indicated

  3. Real-Time Structural Investigation of a Lipid Bilayer during Its Interaction with Melittin Using Sum Frequency Generation Vibrational Spectroscopy

    OpenAIRE

    Chen, Xiaoyun; Wang, Jie; Kristalyn, Cornelius B.; Chen, Zhan

    2007-01-01

    Interactions between membrane bilayers and peptides/proteins are ubiquitous throughout a cell. To determine the structure of membrane bilayers and the associated peptides/proteins, model systems such as supported lipid bilayers are often used. It has been difficult to directly investigate the interactions between a single membrane bilayer and peptides/proteins without exogenous labeling. In this work we demonstrate that sum frequency generation vibrational spectroscopy can be employed to stud...

  4. An Interim Investigation of the Potential of Vibrational Spectroscopy for the Dating of Cultural Objects in Ivory

    OpenAIRE

    O’Connor, Sonia; Edwards, Howell G.M.; Ali , Esam

    2013-01-01

    Radiocarbon dating of ivory requires destructive sampling on a scale not always compatible with the requirements of the preservation and curation of cultural objects. The development of a minimally-destructive dating technique is urgently needed. Raman spectroscopy can detect the changes in the organic and inorganic molecular components of ivory that occur with time. It has been suggested that these vibrational spectroscopic changes could be used to assess the relative date of mammoth ivories...

  5. Perturbation Theory of Anharmonicity Effects in Slow Neutron Inelastic Scattering by Crystals

    International Nuclear Information System (INIS)

    An earlier perturbation treatment of the corresponding X-ray scattering problem is generalized into a calculation of the effect of vibrational anharmonicity on the scattering of slow neutrons by crystals. Of an expansion of the lattice potential in powers of the deviations from the thermally averaged sites, the cubic terms are taken into account up to second order; only first order terms are kept in the quartic anharmonicities. All higher terms are neglected. In particular, formulae for the shifts and broadenings of the one-phonon peaks in coherent scattering are derived in terms of the third and fourth order coupling coefficients. As in X-ray scattering, a simple quadratic relation exists between the shifted ''effective frequencies'' of the long wavelength lattice vibrations and the isothermal elastic constants of the crystal. The lattice frequencies of the harmonic approximation may be obtained by extrapolating to absolute zero the linear dependence on temperature shown by the shifted frequencies above the Debye temperature. (author)

  6. Communication: Vibrationally resolved photoelectron spectroscopy of the tetracyanoquinodimethane (TCNQ) anion and accurate determination of the electron affinity of TCNQ

    International Nuclear Information System (INIS)

    Tetracyanoquinodimethane (TCNQ) is widely used as an electron acceptor to form highly conducting organic charge-transfer solids. Surprisingly, the electron affinity (EA) of TCNQ is not well known and has never been directly measured. Here, we report vibrationally resolved photoelectron spectroscopy (PES) of the TCNQ− anion produced using electrospray and cooled in a cryogenic ion trap. Photoelectron spectrum taken at 354.7 nm represents the detachment transition from the ground state of TCNQ− to that of neutral TCNQ with a short vibrational progression. The EA of TCNQ is measured accurately to be 3.383 ± 0.001 eV (27 289 ± 8 cm−1), compared to the 2.8 ± 0.1 eV value known in the literature and measured previously using collisional ionization technique. In addition, six vibrational peaks are observed in the photoelectron spectrum, yielding vibrational frequencies for three totally symmetric modes of TCNQ. Two-photon PES via a bound electronic excited state of TCNQ− at 3.100 eV yields a broad low kinetic energy peak due to fast internal conversion to vibrationally excited levels of the anion ground electronic state. The high EA measured for TCNQ underlies its ability as a good electron acceptor

  7. Effects of Plant Cell Wall Matrix Polysaccharides on Bacterial Cellulose Structure Studied with Vibrational Sum Frequency Generation Spectroscopy and X-ray Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yong Bum; Lee, Christopher M; Kafle, Kabindra; Park, Sunkyu; Cosgrove, Daniel; Kim, Seong H

    2014-07-14

    The crystallinity, allomorph content, and mesoscale ordering of cellulose produced by Gluconacetobacter xylinus cultured with different plant cell wall matrix polysaccharides were studied with vibrational sum frequency generation (SFG) spectroscopy and X-ray diffraction (XRD).

  8. Two-dimensional Infrared Spectroscopy of vibrational polaritons of molecules in an optical cavity

    CERN Document Server

    Saurabh, Prasoon

    2016-01-01

    Strong coupling of molecular vibrations to an infrared cavity mode affects their nature by creating dressed polariton states. We show how the single and double vibrational polariton manifolds may be controlled by varying the cavity coupling strength, and probed by a time domain 2DIR technique, Double Quantum Coherence (DQC). Applications are made to the amide-I ($CO$) and amide-II ($CN$) bond vibrations of $N-methylacetamide$ (NMA).

  9. Molecular eigenstate spectroscopy: Application to the intramolecular dynamics of some polyatomic molecules in the 3000 to 7000 cm-1 region

    International Nuclear Information System (INIS)

    This project uses high resolution infrared spectroscopy to probe the mechanism of intramolecular vibrational redistribution (IVR) in isolated polyatomic molecules. We have found only vibrationally anharmonic coupling in the C-H stretch region of 1-butyne but rotationally mediated coupling is evident in similar spectra of ethanol. The ''keyhole'' model of IVR was developed to account for the similarities and differences between these molecules. The concepts of the model are being implemented numerically in random matrix calculations. A second F-center laser has been purchased and is now being set up to develop an infrared double resonance technique which can be applied to this problem. 4 refs., 5 figs

  10. High-Pressure Hydrogen Sulfide from First Principles: A Strongly Anharmonic Phonon-Mediated Superconductor

    Science.gov (United States)

    Errea, Ion; Calandra, Matteo; Pickard, Chris J.; Nelson, Joseph; Needs, Richard J.; Li, Yinwei; Liu, Hanyu; Zhang, Yunwei; Ma, Yanming; Mauri, Francesco

    2015-04-01

    We use first-principles calculations to study structural, vibrational, and superconducting properties of H2S at pressures P ≥200 GPa . The inclusion of zero-point energy leads to two different possible dissociations of H2S , namely 3 H2S →2 H3S +S and 5 H2S →3 H3S +HS2 , where both H3S and HS2 are metallic. For H3S , we perform nonperturbative calculations of anharmonic effects within the self-consistent harmonic approximation and show that the harmonic approximation strongly overestimates the electron-phonon interaction (λ ≈2.64 at 200 GPa) and Tc. Anharmonicity hardens H-S bond-stretching modes and softens H-S bond-bending modes. As a result, the electron-phonon coupling is suppressed by 30% (λ ≈1.84 at 200 GPa). Moreover, while at the harmonic level Tc decreases with increasing pressure, the inclusion of anharmonicity leads to a Tc that is almost independent of pressure. High-pressure hydrogen sulfide is a strongly anharmonic superconductor.

  11. High-pressure hydrogen sulfide from first principles: a strongly anharmonic phonon-mediated superconductor.

    Science.gov (United States)

    Errea, Ion; Calandra, Matteo; Pickard, Chris J; Nelson, Joseph; Needs, Richard J; Li, Yinwei; Liu, Hanyu; Zhang, Yunwei; Ma, Yanming; Mauri, Francesco

    2015-04-17

    We use first-principles calculations to study structural, vibrational, and superconducting properties of H_{2}S at pressures P≥200  GPa. The inclusion of zero-point energy leads to two different possible dissociations of H2S, namely 3H2S→2H3S+S and 5H2S→3H3S+HS2, where both H3S and HS2 are metallic. For H3S, we perform nonperturbative calculations of anharmonic effects within the self-consistent harmonic approximation and show that the harmonic approximation strongly overestimates the electron-phonon interaction (λ≈2.64 at 200 GPa) and Tc. Anharmonicity hardens H─S bond-stretching modes and softens H─S bond-bending modes. As a result, the electron-phonon coupling is suppressed by 30% (λ≈1.84 at 200 GPa). Moreover, while at the harmonic level Tc decreases with increasing pressure, the inclusion of anharmonicity leads to a Tc that is almost independent of pressure. High-pressure hydrogen sulfide is a strongly anharmonic superconductor. PMID:25933334

  12. Femtosecond Stimulated Raman Exposes the Role of Vibrational Coherence in Condensed-Phase Photoreactivity.

    Science.gov (United States)

    Hoffman, David P; Mathies, Richard A

    2016-04-19

    Femtosecond spectroscopy has revealed coherent wave packet motion time and time again, but the question as to whether these coherences are necessary for reactivity or merely a consequence of the experiment has remained open. For diatomic systems in the gas phase, such as sodium iodide, the dimensionality of the system requires coordinated atomic motion along the reaction coordinate. Coherent dynamics are also readily observed in condensed-phase multidimensional systems such as chromophores in proteins and solvated charge transfer dimers. Is precisely choreographed nuclear motion (i.e., coherence) required for reactivity in these systems? Can this coherence reveal anything about the reaction coordinate? In this Account, we describe our efforts to tackle these questions using femtosecond stimulated Raman spectroscopy (FSRS). Results of four exemplary systems are summarized to illustrate the role coherence can play in condensed-phase reactivity, the exploitation of vibrational coherence to measure vibrational anharmonicities, and the development of two-dimensional FSRS (2D-FSRS). We begin with rhodopsin, the protein responsible for vertebrate vision. The rhodopsin photoreaction is preternaturally fast: ground-state photoproduct is formed in less than 200 fs. However, the reactively important hydrogen out-of-plane motions as well as various torsions and stretches remain vibrationally coherent long after the reaction is complete, indicating that vibrational coherence can and does survive reactive internal conversion. Both the ultrashort time scale of the reaction and the observed vibrational coherence indicate that the reaction in rhodopsin is a vibrationally coherent process. Next we examine the functional excited-state proton transfer (ESPT) reaction of green fluorescent protein. Oscillations in the phenoxy C-O and imidazolinone C═N stretches in the FSRS spectrum indicated strong anharmonic coupling to a low-frequency phenyl wagging mode that gates the ESPT reaction

  13. Ultrafast Relaxation Dynamics of Photoexcited Zinc-Porphyrin: Electronic-Vibrational Coupling.

    Science.gov (United States)

    Abraham, Baxter; Nieto-Pescador, Jesus; Gundlach, Lars

    2016-08-18

    Cyclic tetrapyrroles are the active core of compounds with crucial roles in living systems, such as hemoglobin and chlorophyll, and in technology as photocatalysts and light absorbers for solar energy conversion. Zinc-tetraphenylporphyrin (Zn-TPP) is a prototypical cyclic tetrapyrrole that has been intensely studied in past decades. Because of its importance for photochemical processes the optical properties are of particular interest, and, accordingly, numerous studies have focused on light absorption and excited-state dynamics of Zn-TPP. Relaxation after photoexcitation in the Soret band involves internal conversion that is preceded by an ultrafast process. This relaxation process has been observed by several groups. Hitherto, it has not been established if it involves a higher lying "dark" state or vibrational relaxation in the excited S2 state. Here we combine high time resolution electronic and vibrational spectroscopy to show that this process constitutes vibrational relaxation in the anharmonic S2 potential. PMID:27482847

  14. Surface structure of protonated R-plane-sapphire (1-102) studied by sum frequency vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sung, J.; Zhang, L.; Tian, C.; Waychunas, G. A.; Shen, Y. R.

    2011-04-01

    Sum frequency vibrational spectroscopy was used to study the protonated R-plane (1{bar 1}02 ) sapphire surface. The OH stretch vibrational spectra show that the surface is terminated with three hydroxyl moieties, two from AlOH{sub 2} and one from Al{sub 2}OH functional groups. The observed polarization dependence allows determination of the orientations of the three OH species. The results suggest that the protonated sapphire (1{bar 1}02 ) surface differs from an ideal stoichimetric termination in a manner consistent with previous X-ray surface diffraction (crystal truncation rod) studies. However, in order to best explain the observed hydrogenbonding arrangement, surface oxygen spacing determined from the X-ray diffraction study requires modification.

  15. Application of vibrational spectroscopy in the in vitro studies of carbon fiber-polylactic acid composite degradation.

    Science.gov (United States)

    Blazewicz, Marta; Gajewska, Maria Chomyszyn; Paluszkiewicz, Czeslawa

    1999-05-01

    Vibrational spectroscopy was used for assessment of new material for stomatology, for guided tissue regeneration (GTR) techniqe.Implants applied in the healing of periodontal defects using GTR technique have to meet stringent requirements concerning their chemical as well physical properties.At present the implants prepared from two layers membranes differing in porosity in their outer and inner layers are studied clinically. Composite plates prepared by us consist of three layers: polylactic acid film, carbon fibres coated with polylactic acid and carbon fabric.Vibrational spectroscopic studies of the material; polylactic acid- carbon fiber have made it possible to analyse chemical reactions occurring between the polymer and carbon surface. Analysis of the IR spectra of samples treated in Ringer solution allowed to describe the phenomena resulting from the composite degradation. It was shown that material biostability is related to the presence of carbon fibers.

  16. Linear and third- and fifth-order nonlinear spectroscopies of a charge transfer system coupled to an underdamped vibration

    International Nuclear Information System (INIS)

    We study hole, electron, and exciton transports in a charge transfer system in the presence of underdamped vibrational motion. We analyze the signature of these processes in the linear and third-, and fifth-order nonlinear electronic spectra. Calculations are performed with a numerically exact hierarchical equations of motion method for an underdamped Brownian oscillator spectral density. We find that combining electron, hole, and exciton transfers can lead to non-trivial spectra with more structure than with excitonic coupling alone. Traces taken during the waiting time of a two-dimensional (2D) spectrum are dominated by vibrational motion and do not reflect the electron, hole, and exciton dynamics directly. We find that the fifth-order nonlinear response is particularly sensitive to the charge transfer process. While third-order 2D spectroscopy detects the correlation between two coherences, fifth-order 2D spectroscopy (2D population spectroscopy) is here designed to detect correlations between the excited states during two different time periods

  17. Decongestion of methylene spectra in biological and non-biological systems using picosecond 2DIR spectroscopy measuring electron-vibration-vibration coupling

    International Nuclear Information System (INIS)

    Methylene is found in the repeat units of many polymers including proteins. In some cases it appears to be a useful reporter of variation in local environment whilst in other contexts average behaviour seems to dominate. In this paper we apply a particular 2DIR technique to a range of systems containing methylene groups, showing that mode frequencies, linewidths and splittings can be easily extracted even when the infrared absorption bands are too congested to allow reliable analysis. 2DIR spectra of polyethylene and several liquid alkanes are compared and it is shown for the case of L-arginine that the methylene scissor modes are split and that this can be resolved by tracking the 2DIR spectrum as a function of time. Calculations from first principles reveal that for most of the methylene modes studied, electrical anharmonicity is the dominant contributor to the 2DIR cross-peak intensity, with the mechanical anharmonicity making only a small contribution

  18. Vibrational spectroscopy of SnBr4 and CCl4 using Lie algebraic approach

    Indian Academy of Sciences (India)

    Joydeep Choudhury; Srinivasa Rao Karmuri; Nirmal Kumar Sarkar; Ramendu Bhattacharjee

    2008-09-01

    The stretching and bending vibrational energies of SnBr4 and CCl4 are calculated in the one-dimensional framework. The dynamical symmetry group of tetrahedral molecule was taken into consideration to construct the model Hamiltonian in this frame-work. Casimir and Majorana invariant operators were also determined accordingly. Using the model Hamiltonian so constructed, we reported the vibrational energy levels of SnBr4 and CCl4 molecules accurately.

  19. Surface deactivation of vibrationally excited N2 studied using infrared titration combined with quantum cascade laser absorption spectroscopy

    International Nuclear Information System (INIS)

    The wall de-excitation probability γN2 of vibrationally excited nitrogen molecules was determined using infrared (IR) titration with CO, CO2 and N2O. Gas mixtures of N2 with 0.05–0.5% of CO (CO2 or N2O) were excited by a pulsed dc discharge at p = 133 Pa in a cylindrical discharge tube. During the afterglow, the vibrational relaxation of titrating molecules was monitored in situ with quantum cascade laser absorption spectroscopy. The value of γN2 was deduced from measured vibrational relaxation times using a model of vibrational kinetics in N2. It was found that adsorption of IR tracers on the surface may increase the value of γN2 by a factor up to two, depending on the molecule and the surface material. It was demonstrated that N2O is the most inert and reliable tracer and it was used for the determination of γN2 on silica, Pyrex, TiO2, Al2O3 and anodized aluminum. Pretreatment of the silica surface by low-pressure plasma was found to have a strong effect on the vibrational de-excitation. Values of γN2 measured after O2, Ar and N2 plasma pretreatment of the same silica discharge tube were 5.7 × 10−4, 8.2 × 10−4 and 11 × 10−4, respectively. This study clearly demonstrates that the presence of adsorbed atoms and molecules on the surface may significantly alter the value of γN2. (paper)

  20. Nuclear resonance vibrational spectroscopy applied to [Fe(OEP)(NO)] : the vibrational assignments of five-coordinate ferrous heme-nitrosyls and implications for electronic structure.

    Energy Technology Data Exchange (ETDEWEB)

    Lehnert, N.; Galinato, M. I.; Paulat, F.; Richter-Addo, G. B.; Sturhahn, W.; Xu, N.; Zhao, J. (X-Ray Science Division); (Univ. of Michigan); (Univ. of Oklahoma)

    2010-01-01

    This study presents Nuclear Resonance Vibrational Spectroscopy (NRVS) data on the five-coordinate (5C) ferrous heme-nitrosyl complex [Fe(OEP)(NO)] (1, OEP{sup 2-} = octaethylporphyrinato dianion) and the corresponding {sup 15}N{sup 18}O labeled complex. The obtained spectra identify two isotope sensitive features at 522 and 388 cm{sup -1}, which shift to 508 and 381 cm{sup -1}, respectively, upon isotope labeling. These features are assigned to the Fe-NO stretch v(Fe-NO) and the in-plane Fe-N-O bending mode {delta}{sub ip}(Fe-N-O), the latter has been unambiguously assigned for the first time for 1. The obtained NRVS data were simulated using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Since complex 1 can potentially exist in 12 different conformations involving the FeNO and peripheral ethyl orientations, extended density functional theory (DFT) calculations and QCC-NCA simulations were performed to determine how these conformations affect the NRVS properties of [Fe(OEP)NO]. These results show that the properties and force constants of the FeNO unit are hardly affected by the conformational changes involving the ethyl substituents. On the other hand, the NRVS-active porphyrin-based vibrations around 340-360, 300-320, and 250-270 cm{sup -1} are sensitive to the conformational changes. The spectroscopic changes observed in these regions are due to selective mechanical couplings of one component of Eu-type (in ideal D4h symmetry) porphyrin-based vibrations with the in-plane Fe-N-O bending mode. This leads to the observed variations in Fe(OEP) core mode energies and NRVS intensities without affecting the properties of the FeNO unit. The QCC-NCA simulated NRVS spectra of 1 show excellent agreement with experiment, and indicate that conformer F is likely present in the samples of this complex investigated here. The observed porphyrin-based vibrations in the NRVS spectra of 1 are also assigned based on the QCC-NCA results. The obtained force

  1. Simulating two-dimensional infrared-Raman and Raman spectroscopies for intermolecular and intramolecular modes of liquid water.

    Science.gov (United States)

    Ito, Hironobu; Tanimura, Yoshitaka

    2016-02-21

    Full classical molecular dynamics (MD) simulations of two-dimensional (2D) infrared-Raman and 2D Raman spectroscopies of liquid water were carried out to elucidate a mode-mode coupling mechanism using a polarizable water model for intermolecular and intramolecular vibrational spectroscopy (POLI2VS). This model is capable of describing both infrared and Raman spectra. Second-order response functions, which consist of one molecular polarizability and two molecular dipole moments for 2D IR-Raman and three molecular polarizabilities for 2D Raman spectroscopies, were calculated using an equilibrium-non-equilibrium hybrid MD approach. The obtained signals were analyzed using a multi-mode Brownian oscillator (BO) model with nonlinear system-bath interactions representing the intramolecular OH stretching, intramolecular HOH bending, hydrogen bonded (HB)-intermolecular librational motion and HB-intermolecular vibrational (translational) motion of liquid water. This model was applied through use of hierarchal Fokker-Planck equations. The qualitative features of the peak profiles in the 2D spectra obtained from the MD simulations are accurately reproduced with the BO model. This indicates that this model captures the essential features of the intermolecular and intramolecular motion. We elucidate the mechanisms governing the 2D signal profiles involving anharmonic mode-mode coupling, the nonlinearities of the polarizability and dipole moment, and the vibrational dephasing processes of liquid water even in the case that the 2D spectral peaks obtained from the MD simulation overlap or are unclear. The mode coupling peaks caused by electrical anharmonic coupling (EAHC) and mechanical anharmonic coupling (MAHC) are observed in all of the 2D spectra. We find that the strength of the MAHC between the OH-stretching and HB-intermolecular vibrational modes is comparable to that between the OH-stretching and HOH bending modes. Moreover, we find that this OH-stretching and HB

  2. Femtosecond stimulated Raman spectroscopy as a tool to detect molecular vibrations in ground and excited electronic states

    Science.gov (United States)

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

    2016-05-01

    We give a detailed theoretical analysis of the simplest variant of femtosecond stimulated Raman spectroscopy, where a picosecond Raman pump pulse and a femtosecond Raman probe pulse are applied resonantly to a chromophore in thermal equilibrium in the ground electronic state. We demonstrate that this technique is capable of the detection of dephasing-free Raman-like lines revealing vibrational modes not only in the electronic ground state but also in the excited electronic state of the chromophore. The analytical results obtained with simplifying assumptions for the shape of the laser pulses are substantiated by numerical simulations with realistic laser pulses, employing the equation-of-motion phase-matching approach.

  3. Scattering of Neutrons by an Anharmonic Crystal

    International Nuclear Information System (INIS)

    Numerical calculations have been performed for the anharmonic effects in neutron scattering. The phonon frequency widths and shifts have been calculated as a function of neutron frequency at different wave numbers and temperatures for a potential with central symmetry and for a face-centered cubic lattice

  4. High Resolution Emission Spectroscopy of the Vibration-Rotation Bands of Hbo and Hbs.

    Science.gov (United States)

    Li, G.; Ram, R. S.; Hargreaves, R. J.; Bernath, P. F.; Li, H.

    2012-06-01

    The vibration-rotation spectra of HBO and HBS have been investigated at high resolution using a Fourier transform spectrometer. The HBO molecules were produced in a high temperature furnace from the reaction of H2O vapor with boron by heating a mixture of crystalline boron and boron oxide (B2O3) at a temperature ˜1350°C. The spectra were recorded in the 1100-2200 cm-1 and 1700-4000 cm-1 wavenumber regions covering the ν3 and ν1 fundamentals, respectively. In total 24 vibrational bands involving 30 vibrational levels of H11BO and 12 bands involving 18 levels of H10BO have been rotationally analyzed. After combining the existing microwave and infrared measurements, the absolute term values have been determined for a number of vibrationally-excited states of H11BO and H10BO. The HBS molecules were formed by the reaction of CS2 and water vapor with crystalline boron at a temperature ˜1300°C. The spectra were recorded in the 850-1500 cm-1 and 1750-4000 cm-1 wavenumber regions covering the ν3 and ν1 frequency regions. In total 29 vibrational bands involving 33 vibrationally-excited levels of H11BS and 9 bands involving 12 vibrational levels of H10BS have been analyzed. The fitted spectroscopic parameters agree very well with the results of our {ab initio} calculations. {L}-resonance interactions observed between the 0200 (Σ) and 0220 (Δ) levels of HBO and HBS were analyzed using a 2×2 matrix to yield deperturbed constants.

  5. The origin of phonon anharmonicity in MgB{sub 2} and related compounds

    Energy Technology Data Exchange (ETDEWEB)

    Boeri, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Bachelet, G B [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Cappelluti, E [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Pietronero, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy)

    2003-02-01

    The recent discovery of a superconducting transition at 39 K in MgB{sub 2} - made of alternating Mg and graphene-like B planes - has raised great interest, for both its technological and theoretical implications. It was clear since the very beginning that the properties of this material are related to an anomalous coupling between the charge carriers in the {sigma} bands - due to in-plane bonds between Boron atoms - and the phonon mode (E{sub 2g}) which involves in-plane vibrations of the B ions. Theoretical studies have thus been focused on the search for possible anomalies in the e-ph coupling: one of the first results was the discovery that the E{sub 2g} phonon is highly anharmonic, but the connection between anharmonicity and T{sub c} in this material is still a controversial point. We first present a detailed first-principles study of the E{sub 2g} phonon anharmonicity in MgB{sub 2} and analogous compounds which are not superconducting, AlB{sub 2} and graphite, and in a hypothetical hole-doped graphite (C{sup 2+}{sub 2}); we then introduce an analytical model which allows us to relate the onset of anharmonicity with the small Fermi energy of the carriers in {sigma} bands. Our study suggests a possible relation between anharmonicity and non-adiabaticity; non-adiabatic effects, which can lead to a sensible increase of T{sub c} with respect to values predicted by conventional theory, become in fact relevant when phonon frequencies are comparable to electronic energy scales.

  6. Vibrational structure of C 84 and Sc 2@C 84 analyzed by IR spectroscopy

    Science.gov (United States)

    Hulman, M.; Pichler, T.; Kuzmany, H.; Zerbetto, F.; Yamamoto, E.; Shinohara, H. N.

    1997-06-01

    The isomer III of Sc 2@C 84 was separated by multi-cycle HPLC purification. We present temperature dependent IR absorption measurements of Sc 2@C 84 which have been performed between 50 and 300 K and between 400 and 5000 cm -1, respectively. The vibrational structure of the endohedral compound is compared to the structure of unfilled C 84. We find a strong overall broadening of the vibrational modes in Sc 2@C 84. Also some of the vibrational absorption lines are strongly enhanced if compared to the spectrum for the empty cage. With decreasing temperature, a dramatic narrowing of the lines in the spectral range between 700 and 800 cm -1 is observed.

  7. Sum Frequency Generation Vibrational Spectroscopy of Adsorbed Amino Acids, Peptides and Proteins of Hydrophilic and Hydrophobic Solid-Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Holinga IV, George Joseph [Univ. of California, Berkeley, CA (United States)

    2010-09-01

    Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the interfacial properties of several amino acids, peptides, and proteins adsorbed at the hydrophilic polystyrene solid-liquid and the hydrophobic silica solid-liquid interfaces. The influence of experimental geometry on the sensitivity and resolution of the SFG vibrational spectroscopy technique was investigated both theoretically and experimentally. SFG was implemented to investigate the adsorption and organization of eight individual amino acids at model hydrophilic and hydrophobic surfaces under physiological conditions. Biointerface studies were conducted using a combination of SFG and quartz crystal microbalance (QCM) comparing the interfacial structure and concentration of two amino acids and their corresponding homopeptides at two model liquid-solid interfaces as a function of their concentration in aqueous solutions. The influence of temperature, concentration, equilibration time, and electrical bias on the extent of adsorption and interfacial structure of biomolecules were explored at the liquid-solid interface via QCM and SFG. QCM was utilized to quantify the biological activity of heparin functionalized surfaces. A novel optical parametric amplifier was developed and utilized in SFG experiments to investigate the secondary structure of an adsorbed model peptide at the solid-liquid interface.

  8. Vibrational autodetachment spectroscopy of Au-6 : Image-charge-bound states of a gold ring

    International Nuclear Information System (INIS)

    Spectral experiments on mass-selected negative cluster ions of gold and silver were performed in the wavelength range near the threshold for one-photon photodetachment of the extra electron. The Au-6 cluster ion displayed a uniquely well resolved spectrum consisting of a progression in a single vibrational mode. Details of this threshold photodetachment spectrum and the associated photoelectron energy distribution suggest an explanation based on autodetachment from totally symmetric vibrational levels of very weakly bound excited electronic state (bound by image charge forces) of the Au-6 cluster in the form of a planar, six-fold symmetric, gold ring

  9. Vibrational spectroscopy of shock-compressed fluid N2 and O2

    International Nuclear Information System (INIS)

    Single-pulse multiplex coherent anti-Stokes Raman scattering (CARS) was used to observe the vibrational spectra of liquid N2 shock-compressed to several pressures and temperatures up to 41 GPa and 5200 K and liquid O2 shock-compressed to several pressures and temperatures up to 10 GPa and 1000 K. For N2, the experimental spectra were compared to synthetic spectra calculated using a semiclassical model for CARS intensities and estimated vibrational frequencies, peak Raman susceptibilities, and Raman line widths. The question of excited state populations in the shock-compressed state is addressed

  10. Spectroscopy of electronic and vibrational excitations in semiconductors and oxide insulators

    Science.gov (United States)

    Bhosale, Jayprakash

    A temperature tuned light emitting diode (LED) has several advantages over conventional sources for optical spectroscopy. The large radiation density of LEDs, concentrated in a small spectral region, is ideal for Spectroscopic techniques where a high signal-to-noise (S/N) ratio is desired. A simple, inexpensive LED source leads to a superior performance at high resolutions exceeding that of a tungsten halogen lamp, from near infrared to ultraviolet spectral region. A theoretical investigation with ab initio techniques of the electron-phonon interaction of semiconductors with chalcopyrite structure and its comparison with modulated reflectivity experiments yield a striking difference between those with (AgGaS2) and without (ZnSnAs 2) d electrons in their valence bands. The former exhibit a non-monotonic temperature dependence of the band gaps whose origin is not yet fully understood. The analysis of this temperature dependence with the Bose-Einstein oscillator model involving two oscillator terms having weights of opposite signs, provides an excellent agreement with the experimental data and correlates well with the characteristic peaks in the phonon density of states associated with the acoustical phonon modes. This work underscores the need for theoretical understanding of the electron-phonon interaction involving d electrons, particularly in ab initio investigations. Spectroscopic signatures of point defects serve as insightful characterizations in basic studies on semiconductors and their applications. In this context, localized vibrational modes (LVMs) revealed in their infrared absorption spectra the appearance of vacancies and interstitials originating from the lack of exact stoichiometry is a special feature of compound semiconductors. A striking manifestation of the LVMs of oxygen impurities substitutionally incorporated into CdSe is observed in which cation vacancies are either generated or suppressed deliberately by adopting specific crystal growth

  11. Applications and Developments on the Use of Vibrational Spectroscopy Imaging for the Analysis, Monitoring and Characterisation of Crops and Plants.

    Science.gov (United States)

    Cozzolino, Daniel; Roberts, Jessica

    2016-01-01

    The adaptation and use of advanced technologies is an effective and encouraging way to efficiently and reliably characterise crops and plants. Additionally advances in these technologies will improve the information available for agronomists, breeders and plant physiologists in order to develop best management practices in the process and commercialization of agricultural products and commodities. Methods based on vibrational spectroscopy such as near infrared (NIR) spectroscopy using either single spot or hyperspectral measurements are now more available and ready to use than ever before. The main characteristics of these methodologies (high-throughput, non-destructive) have determined a growth in basic and applied research using NIR spectroscopy in many disciplines related with crop and plant sciences. A wide range of studies have demonstrated the ability of NIR spectroscopy to analyse different parameters in crops. Recently the use of hyperspectral imaging techniques have expanded the range of applications in crop and plant sciences. This article provides an overview of applications and developments of NIR hyperspectral image for the analysis, monitoring and characterisation of crops and plants. PMID:27294902

  12. Evidences of rare-earth nanophases embedded in silica using vibrational spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Vedda, A.; Chiodini, N.; Fasoli, M.; Lauria, A.; Moretti, F.; Di Martino, D.; Baraldi, A.; Buffagni, E.; Capelletti, R.; Mazzera, M.; Boháček, Pavel; Mihóková, Eva

    2010-01-01

    Roč. 57, č. 3 (2010), s. 1361-1369. ISSN 0018-9499 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z10100520 Keywords : nano-phases * rare-earths * scintillators * vibrational properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.519, year: 2010

  13. Evidence for cooperative vibrational relaxation of the NH-, OH-, and OD-stretching modes in hydrogen-bonded liquids using infrared pump-probe spectroscopy.

    Science.gov (United States)

    Shaw, D J; Panman, M R; Woutersen, S

    2009-11-27

    Vibrational energy relaxation of the NH-, OH-, and OD-stretching modes in hydrogen-bonded liquids has been investigated by means of infrared pump-probe spectroscopy. The relaxation rates have been determined both in neat liquids and in isotopic mixtures with systematically varied isotope fractions. In all liquids, the vibrational relaxation rate increases as the isotope fraction is increased and reaches a maximum in the neat liquid. The dependence of the relaxation rate on the isotope fraction suggests a relaxation channel in which the vibrational energy is partitioned between accepting modes of two neighboring molecules. PMID:20366125

  14. Evidence for Cooperative Vibrational Relaxation of the NH-, OH-, and OD-Stretching Modes in Hydrogen-Bonded Liquids Using Infrared Pump-Probe Spectroscopy

    Science.gov (United States)

    Shaw, D. J.; Panman, M. R.; Woutersen, S.

    2009-11-01

    Vibrational energy relaxation of the NH-, OH-, and OD-stretching modes in hydrogen-bonded liquids has been investigated by means of infrared pump-probe spectroscopy. The relaxation rates have been determined both in neat liquids and in isotopic mixtures with systematically varied isotope fractions. In all liquids, the vibrational relaxation rate increases as the isotope fraction is increased and reaches a maximum in the neat liquid. The dependence of the relaxation rate on the isotope fraction suggests a relaxation channel in which the vibrational energy is partitioned between accepting modes of two neighboring molecules.

  15. Quantum anharmonic oscillator: The airy function approach

    Energy Technology Data Exchange (ETDEWEB)

    Maiz, F., E-mail: fethimaiz@gmail.com [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia); University of Cartage, Nabeul Engineering Preparatory Institute, Merazka, 8000 Nabeul (Tunisia); AlFaify, S. [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia)

    2014-05-15

    New and simple numerical method is being reported to solve anharmonic oscillator problems. The method is setup to approach the real potential V(x) of the anharmonic oscillator system as a piecewise linear potential u(x) and to solve the Schrödinger equation of the system using the Airy function. Then, solutions continuity conditions lead to the energy quantification condition, and consequently, the energy eigenvalues. For testing purpose, the method was applied on the sextic and octic oscillators systems. The proposed method is found to be realistic, computationally simple, and having high degrees of accuracy. In addition, it can be applied to any form of potential. The results obtained by the proposed method were seen closely agreeing with results reached by other complicated methods.

  16. Anharmonic oscillations of a conical buoy

    CERN Document Server

    Oliveira, J Brochado; da Silva, J M Machado

    2011-01-01

    A study of the foating of a circular cone shaped buoy in an ideal fluid has revealed some new interesting results. Using reduced variables it is shown, that at a crossover value (3/4) of the ratio of the specific masses of the fluid and of the buoy, the anharmonicity of the oscillation is the highest and that, unexpectedly, above this crossover value the normalized period is constant.

  17. Vibrational spectroscopy investigation and density functional theory calculations on (E)-N‧-(4-methoxybenzylidene) benzohydrazide

    Science.gov (United States)

    Saleem, H.; Subashchandrabose, S.; Ramesh Babu, N.; Syed Ali Padusha, M.

    2015-05-01

    The FT-IR, FT-Raman and UV-Vis spectra of the Schiff base compound (E)-N‧-(4-methoxybenzylidene) benzohydrazide (MBBH) have been recorded and analyzed. The optimized geometrical parameters were calculated. The complete vibrational assignments were performed on the basis of TED of the vibrational modes, calculated with the help of SQM method. NBO analysis has been carried out to explore the hyperconjugative interactions and their second order stabilization energy within the molecule. The molecular orbitals (MO's) and its energy gap were studied. The first order hyperpolarizability (β0) and related properties (β, α0, Δα) of MBBH are also calculated. All theoretical calculations were performed on the basis of B3LYP/6-311++G(d,p) level of theory.

  18. Structure and vibrational spectroscopy investigation of 2-(4-chlorophenyliminomethyl)-8-hydroxyquinoline

    Science.gov (United States)

    Zhao, Bin; Wang, Yang-yang; Zhang, Yu-hua; Dai, Li; Zhou, Zheng-yu

    2011-10-01

    2-(4-Chlorophenyliminomethyl)-8-hydroxyquinoline was synthesized and crystal data was obtained in the orthorhombic space group P-1, with Z = 4. Unit cell parameters a = 4.744(7) Å, b = 9.981(15) Å, c = 27.27(4) Å and V = 12915(3) Å 3. In this paper the structural properties and vibrational frequencies of 8-hydroxyquinoline derivative, 2CP8HQ, are studied with the B3LYP and HF methods. Two stable conformers are obtained. The calculated frequencies are in good agreement with the experiment results. It is indicated that both of theoretical calculations were suitable for molecular vibrational frequencies study and the scaled B3LYP method was superior to the scaled HF methods.

  19. Vibrationally highly excited molecules and intramolecular mode coupling through high-overtone spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wong, J.S.; Moore, C.B.

    1981-08-01

    High overtone spectra of organic molecules can be interpreted using the local mode model for absorptions by the inequivalent C-H bonds. The spectra can be assigned using either observed C-H bond lengths or isolated fundamental frequencies. The spectra of trihalomethanes indicate that the dominant intramolecular mode coupling for the C-H stretching overtones is Fermi resonance with combination states with one less C-H stretching quantum plus two quanta of the C-H bending vibrations.

  20. The Application of Vibrational Spectroscopy Techniques in the Qualitative Assessment of Material Traded as Ginseng

    OpenAIRE

    Maxleene Sandasi; Ilze Vermaak; Weiyang Chen; Alvaro Viljoen

    2016-01-01

    The name “ginseng” is collectively used to describe several plant species, including Panax ginseng (Asian/Oriental ginseng), P. quinquefolius (American ginseng), P. pseudoginseng (Pseudoginseng) and Eleutherococcus senticosus (Siberian ginseng), each with different applications in traditional medicine practices. The use of a generic name may lead to the interchangeable use or substitution of raw materials which poses quality control challenges. Quality control methods such as vibrational spec...

  1. Obtaining Sulfur from Sulfur Hexafluoride and Studying the Sulfur Isotopes Properties by Using Vibrational Spectroscopy

    OpenAIRE

    Egorov, Nikolai Borisovich; Akimov, Dmitry Vasilievich; Zhuravlev, Nikolay

    2015-01-01

    Scheme of isotopically enriched SF[6] to elemental sulfur with orthorhombic modification conversion is offered. This scheme includes SF[6] reduction to Li2S by using lithium. The yield of isotopically enriched sulfur is not less than 97% with chemical purity not less than 99.9%. The results which show the dependence of the experimental frequencies in the vibrational spectra on the molecular weight of the sulfur isotope have been obtained.

  2. Direct observation of the fundamental vibration-rotation transitions within the NiD X2Δ ground state by CO-Faraday-L.M.R. spectroscopy and zero field transitions in NiH

    Science.gov (United States)

    Lipus, K.; Simon, U.; Bachem, E.; Nelis, Th.; Urban, W.

    We report the first direct observation of the vibration-rotation spectrum of nickel-deuteride in its X2Δ ground state by CO-Faraday-L.M.R. spectroscopy. A set of effective molecular parameters is given. We present first results on the vibration-rotation spectroscopy of NiH, employing a tunable diode laser spectrometer.

  3. Applicability of Quantum Thermal Baths to Complex Many-Body Systems with Various Degrees of Anharmonicity.

    Science.gov (United States)

    Hernández-Rojas, Javier; Calvo, Florent; Noya, Eva Gonzalez

    2015-03-10

    The semiclassical method of quantum thermal baths by colored noise thermostats has been used to simulate various atomic systems in the molecular and bulk limits, at finite temperature and in moderately to strongly anharmonic regimes. In all cases, the method performs relatively well against alternative approaches in predicting correct energetic properties, including in the presence of phase changes, provided that vibrational delocalization is not too strong-neon appearing already as an upper limiting case. In contrast, the dynamical behavior inferred from global indicators such as the root-mean-square bond length fluctuation index or the vibrational spectrum reveals more marked differences caused by zero-point energy leakage, except in the case of isolated molecules with well separated vibrational modes. To correct for such deficiencies and reduce the undesired transfer among modes, empirical modifications of the noise power spectral density were attempted to better describe thermal equilibrium but still failed when used as semiclassical preparation for microcanonical trajectories. PMID:26579740

  4. Salt Effects on Surface Structures of Polyelectrolyte Multilayers (PEMs) Investigated by Vibrational Sum Frequency Generation (SFG) Spectroscopy.

    Science.gov (United States)

    Ge, Aimin; Matsusaki, Michiya; Qiao, Lin; Akashi, Mitsuru; Ye, Shen

    2016-04-26

    Sum frequency generation (SFG) vibrational spectroscopy was employed to investigate the surface structures of polyelectrolyte multilayers (PEMs) constructed by sequentially alternating adsorption of poly(diallyldimethylammonium chloride) (PDDA) and poly(styrenesulfonate) (PSS). It was found that the surface structures and surface charge density of the as-deposited PEMs of PDDA/PSS significantly depend on the concentration of sodium chloride (NaCl) present in the polyelectrolyte solutions. Furthermore, it was found that the surface structure of the as-deposited PEMs is in a metastable state and will reach the equilibrium state by diffusion of the polyelectrolyte chain after an aging process, resulting in a polyelectrolyte mixture on the PEM surfaces. PMID:27045932

  5. Femtosecond stimulated Raman spectroscopy as a tool to detect molecular vibrations in ground and excited electronic states.

    Science.gov (United States)

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

    2016-05-14

    We give a detailed theoretical analysis of the simplest variant of femtosecond stimulated Raman spectroscopy, where a picosecond Raman pump pulse and a femtosecond Raman probe pulse are applied resonantly to a chromophore in thermal equilibrium in the ground electronic state. We demonstrate that this technique is capable of the detection of dephasing-free Raman-like lines revealing vibrational modes not only in the electronic ground state but also in the excited electronic state of the chromophore. The analytical results obtained with simplifying assumptions for the shape of the laser pulses are substantiated by numerical simulations with realistic laser pulses, employing the equation-of-motion phase-matching approach. PMID:27179484

  6. Vibrational dynamics of single-crystal YVO4 studied by polarized micro-Raman spectroscopy and ab initio calculations

    Science.gov (United States)

    Sanson, Andrea; Giarola, Marco; Rossi, Barbara; Mariotto, Gino; Cazzanelli, Enzo; Speghini, Adolfo

    2012-12-01

    The vibrational properties of yttrium orthovanadate (YVO4) single crystals, with tetragonal zircon structure, have been investigated by means of polarized micro-Raman spectroscopy and ab initio calculations. Raman spectra were taken at different polarizations and orientations carefully set by the use of a micromanipulator, so that all of the twelve Raman-active modes, expected on the basis of the group theory, were selected in turn and definitively assigned in wave number and symmetry. In particular the Eg(4) mode, assigned incorrectly in previous literature, has been observed at 387 cm-1. Moreover, the very weak Eg(1) mode, peaked at about 137 cm-1, was clearly observed only under some excitation wavelengths, and its peculiar Raman excitation profile was measured within a wide region of the visible. Finally, ab initio calculations based on density-functional theory have been performed in order to determine both Raman and infrared vibrational modes and to corroborate the experimental results. The rather good agreement between computational and experimental frequencies is slightly better than in previous computational works and supports our experimental symmetry assignments.

  7. Vibrational spectroscopy at interfaces by IR-VIS sum-frequency generation using CLIO FEL

    International Nuclear Information System (INIS)

    IR-vis sum-frequency generation (SFG) has developed into a versatile technique for probing the vibrational structure of interfaces. To overcome the limited spectral range accessible by benchtop IR lasers, we have developed an SFG spectrometer that makes use of the broad band tuneable infrared beam provided by the CLIO-FEL. We will evaluate the gain in sensitivity of the FEL-SFG spectrometer in comparison to that of benchtop lasers, taking account of the surface damage by laser heating. Thereafter, we review the different research projects undertaken using this facility: (1) The interface selectivity of SFG makes it particularly suitable for probing buried liquid/solid interface. We took advantage of the spectrometer sensitivity to monitor the electrochemical deposition of hydrogen on platinum single crystals at under- and overpotential (2) Because of its sensitivity to the molecular symmetry, SFG allows probing the conformation of self assembled monolayers deposited on metals. We discuss SFG spectra of ω(4-nitroanilino)-dodecane adsorbed on polycrystalline gold and silver films; in the 1550 - 900 cm-1 spectral range. (3) We have undertaken a spectroscopic approach for the investigation of polymer films adhesion on glass. Polyurethane/glass interface is investigated in the 2200 - 1600 cin-1 spectral region. (4) The use of the CLIO FEL allows probing of the vibrational dynamics of the prominent IR active vibrations between 1500 and 500 cm-1 of fullerene epitaxial films. These modes are modified upon charge transfer from the substrate to the C60 molecules. Preliminary SFG spectra of C60/Ag interface are presented. (5) Site specific detection of CO adsorption and CO + O coadsorption on Pd(111) are studied

  8. Accurate ab initio anharmonic force field and heat of formation for silane, $SiH_{4}$

    CERN Document Server

    Martin, J M L; Lee, T J; Martin, Jan M.L.; Baldridge, Kim K.; Lee, Timothy J.

    1999-01-01

    From large basis set coupled cluster calculations and a minor empirical adjustment, an anharmonic force field for silane has been derived that is consistently of spectroscopic quality ($\\pm 1 cm^{-1}$ on vibrational fundamentals) for all isotopomers of silane studied. Inner-shell polarization functions have an appreciable effect on computed properties and even on anharmonic corrections. From large basis set coupled cluster calculations and extrapolations to the infinite-basis set limit, we obtain TAE_0=303.80 \\pm 0.18 kcal/mol, which includes an anharmonic zero-point energy (19.59 kcal/mol), inner-shell correlation (-0.36 kcal/mol), scalar relativistic corrections (-0.70 kcal/mol), and atomic spin-orbit corrections (-0.43 kcal/mol). In combination with the recently revised \\HVSI{0}, we obtain $\\Delta H^{\\circ}_{f,0}[SiH_4(g)]=9.9 \\pm 0.4 kcal/mol$, in between the two established experimental values.

  9. Combined electron microscopy and vibrational spectroscopy study of corroded Magnox sludge from a legacy spent nuclear fuel storage pond

    International Nuclear Information System (INIS)

    Graphical abstract: Spent Magnox fuel corroding in-situ in storage ponds forms sludges comprised of brucite and other Mg based phases with uranium oxide particles. Display Omitted Research highlights: → Caracterization study of highly radioactive corroded Magnox sludges. → Unique data from samples of actual corroded nuclear fuel. → Combined electron microscopy and vibrational spectroscopy study. → Analysis of particles from legacy spent fuel storage pond at Sellafield. → Supports major UK decommissioning and nuclear clean up challenge. - Abstract: Samples of filtered particulates and sludges, formed from corroding magnesium alloy clad uranium metal ('Magnox') fuel elements, collected from one of the legacy nuclear fuel storage ponds located at Sellafield (UK) were investigated by Environmental Scanning Electron Microscopy with Energy Dispersive X-Ray analysis (ESEM/EDX), micro-Raman spectroscopy and Fourier transform infra-red spectroscopy (FT-IR). ESEM imaging confirmed the dominant morphology to be clusters of interlocking platelets typical of brucite (Mg(OH)2). EDX analysis was suggestive of some conversion to the related phase, hydrotalcite (Mg6Al2(CO3)(OH)16.4H2O), due to elevated levels of Al associated with Mg. Other apparent morphologies were less commonly observed including flaky sheets, consistent with earlier stages of Magnox alloy corrosion. In a few specific cases, rods were also observed suggestive of some conversion to Mg-hydroxycarbonate phases. Discrete phases rich in U were also identified. Fluorescence in the Raman spectroscopy also indicated surface coatings of organic macromolecules and iron sulphide on hematite containing particles, attributed to microbial activity within the open air pond. Some specific differences in the solid phases between pond areas with differing conditions were apparent.

  10. Combined electron microscopy and vibrational spectroscopy study of corroded Magnox sludge from a legacy spent nuclear fuel storage pond

    Energy Technology Data Exchange (ETDEWEB)

    Gregson, Colin R., E-mail: colin.r.gregson@nnl.co.uk [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale CA20 1PG (United Kingdom); Goddard, David T., E-mail: dave.t.goddard@nnl.co.uk [National Nuclear Laboratory, Preston Laboratory, Springfields, Salwick, Preston PR4 0XJ (United Kingdom); Sarsfield, Mark J., E-mail: mark.j.sarsfield@nnl.co.uk [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale CA20 1PG (United Kingdom); Taylor, Robin J., E-mail: robin.j.taylor@nnl.co.uk [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale CA20 1PG (United Kingdom)

    2011-05-01

    Graphical abstract: Spent Magnox fuel corroding in-situ in storage ponds forms sludges comprised of brucite and other Mg based phases with uranium oxide particles. Display Omitted Research highlights: > Caracterization study of highly radioactive corroded Magnox sludges. > Unique data from samples of actual corroded nuclear fuel. > Combined electron microscopy and vibrational spectroscopy study. > Analysis of particles from legacy spent fuel storage pond at Sellafield. > Supports major UK decommissioning and nuclear clean up challenge. - Abstract: Samples of filtered particulates and sludges, formed from corroding magnesium alloy clad uranium metal ('Magnox') fuel elements, collected from one of the legacy nuclear fuel storage ponds located at Sellafield (UK) were investigated by Environmental Scanning Electron Microscopy with Energy Dispersive X-Ray analysis (ESEM/EDX), micro-Raman spectroscopy and Fourier transform infra-red spectroscopy (FT-IR). ESEM imaging confirmed the dominant morphology to be clusters of interlocking platelets typical of brucite (Mg(OH){sub 2}). EDX analysis was suggestive of some conversion to the related phase, hydrotalcite (Mg{sub 6}Al{sub 2}(CO{sub 3})(OH){sub 16}.4H{sub 2}O), due to elevated levels of Al associated with Mg. Other apparent morphologies were less commonly observed including flaky sheets, consistent with earlier stages of Magnox alloy corrosion. In a few specific cases, rods were also observed suggestive of some conversion to Mg-hydroxycarbonate phases. Discrete phases rich in U were also identified. Fluorescence in the Raman spectroscopy also indicated surface coatings of organic macromolecules and iron sulphide on hematite containing particles, attributed to microbial activity within the open air pond. Some specific differences in the solid phases between pond areas with differing conditions were apparent.

  11. Proceedings of the Thirteenth International Conference on Time-Resolved Vibrational Spectroscopy

    OpenAIRE

    Laubereau, Alfred; Mantel, Karl-Heinz; Zinth, Wolfgang

    2007-01-01

    The thirteenth meeting in a long-standing series of “Time-Resolved Vibrational Spectroscopy” (TRVS) conferences was held May 19th to 25th at the Kardinal Döpfner Haus in Freising, Germany, organized by the two Munich Universities - Ludwig-Maximilians-Universität and Technische Universität München. This international conference continues the illustrious tradition of the original in 1982, which took place in Lake Placid, NY. The series of meetings was initiated by leading, world-renowned exp...

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

    Directory of Open Access Journals (Sweden)

    Kobayashi Takayoshi.

    2013-03-01

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

  13. Vibrational spectroscopy and chemometrics for rapid, quantitative analysis of bitter acids in hops (Humulus lupulus).

    Science.gov (United States)

    Killeen, Daniel P; Andersen, David H; Beatson, Ron A; Gordon, Keith C; Perry, Nigel B

    2014-12-31

    Hops, Humulus lupulus, are grown worldwide for use in the brewing industry to impart characteristic flavor and aroma to finished beer. Breeders produce many varietal crosses with the aim of improving and diversifying commercial hops varieties. The large number of crosses critical to a successful breeding program imposes high demands on the supporting chemical analytical laboratories. With the aim of reducing the analysis time associated with hops breeding, quantitative partial least-squares regression (PLS-R) models have been produced, relating reference data acquired by the industrial standard HPLC and UV methods, to vibrational spectra of the same, chemically diverse hops sample set. These models, produced from rapidly acquired infrared (IR), near-infrared (NIR), and Raman spectra, were appraised using standard statistical metrics. Results demonstrated that all three spectroscopic methods could be used for screening hops for α-acid, total bitter acids, and cohumulone concentrations in powdered hops. Models generated from Raman and IR spectra also showed potential for use in screening hops varieties for xanthohumol concentrations. NIR analysis was performed using both a standard benchtop spectrometer and a portable NIR spectrometer, with comparable results obtained by both instruments. Finally, some important vibrational features of cohumulone, colupulone, and xanthohumol were assigned using DFT calculations, which allow more insightful interpretation of PLS-R latent variable plots. PMID:25485767

  14. Terahertz Vibrations and Hydrogen-Bonded Networks in Crystals

    Directory of Open Access Journals (Sweden)

    Masae Takahashi

    2014-03-01

    Full Text Available The development of terahertz technology in the last few decades has made it possible to obtain a clear terahertz (THz spectrum. THz vibrations clearly show the formation of weak bonds in crystals. The simultaneous progress in the code of first-principles calculations treating noncovalent interactions has established the position of THz spectroscopy as a powerful tool for detecting the weak bonding in crystals. In this review, we are going to introduce, briefly, the contribution of weak bonds in the construction of molecular crystals first, and then, we will review THz spectroscopy as a powerful tool for detecting the formation of weak bonds and will show the significant contribution of advanced computational codes in treating noncovalent interactions. From the second section, following the Introduction, to the seventh section, before the conclusions, we describe: (1 the crystal packing forces, the hydrogen-bonded networks and their contribution to the construction of organic crystals; (2 the THz vibrations observed in hydrogen-bonded molecules; (3 the computational methods for analyzing the THz vibrations of hydrogen-bonded molecules; (4 the dispersion correction and anharmonicity incorporated into the first-principles calculations and their effect on the peak assignment of the THz spectrum (5 the temperature dependence; and (6 the polarization dependence of the THz spectrum.

  15. Ultrafast dynamics of water at the water-air interface studied by femtosecond surface vibrational spectroscopy

    Directory of Open Access Journals (Sweden)

    Bakker Huib J.

    2013-04-01

    Full Text Available We study the dynamics of water molecules at the water-air interface, using surfacespecific two-dimensional infrared sum-frequency generation (2D-SFG spectroscopy. The data reveal the occurrence of surprisingly fast energy transfer and reorientational dynamics at aqueous interfaces.

  16. Spectral methods for study of the G-protein-coupled receptor rhodopsin: I. Vibrational and electronic spectroscopy

    Science.gov (United States)

    Struts, A. V.; Barmasov, A. V.; Brown, M. F.

    2015-05-01

    Here we review the application of modern spectral methods for the study of G-protein-coupled receptors (GPCRs) using rhodopsin as a prototype. Because X-ray analysis gives us immobile snapshots of protein conformations, it is imperative to apply spectroscopic methods for elucidating their function: vibrational (Raman, FTIR), electronic (UV-visible absorption, fluorescence) spectroscopies, and magnetic resonance (electron paramagnetic resonance, EPR), and nuclear magnetic resonance (NMR). In the first of the two companion articles, we discuss the application of optical spectroscopy for studying rhodopsin in a membrane environment. Information is obtained regarding the time-ordered sequence of events in rhodopsin activation. Isomerization of the chromophore and deprotonation of the retinal Schiff base leads to a structural change of the protein involving the motion of helices H5 and H6 in a pH-dependent process. Information is obtained that is unavailable from X-ray crystallography, which can be combined with spectroscopic studies to achieve a more complete understanding of GPCR function.

  17. Azide-water intermolecular coupling measured by 2-color 2D IR spectroscopy

    Directory of Open Access Journals (Sweden)

    Perakis F.

    2013-03-01

    Full Text Available We present 2-color two-dimensional infrared spectroscopy of intermolecular coupling between azide ions and their solvation shell water molecules. The cross-peak between azide asymmetric stretch vibration and the OD-stretch vibration is a result of low- probability uphill population transfer. Narrow bleach/excited state absorption peak shows selectivity to solvation shell water molecules only and the characteristics of the cross-peak suggest that the solvation shell hydrogen bond potential has similar anharmonic properties as the hydrogen bond in ice Ih. Population and depopulation of the excited state of the OD-stretch vibration happen on 150 fs and 1.7 ps timescales, respectively, with early manifesting heating effects that limit the selectivity to population times up to 1 ps.

  18. Interfacial Water Structure in Langmuir Monolayer and Gibbs Layer Probed by Sum Frequency Generation Vibrational Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    张贞; 郭源

    2012-01-01

    Langmuir monolayer and Gibbs layer exhibit surface-active properties and it can be used as simple model systems to investigate the physicochemical properties of biological membranes. In this report, we presented the OH stretching vibration of H2O in the 4"-n-pentyl-4-cyano-p-terphenyl (5CT), nonadecanenitrile (C18CN) Langmuir monolayer and compared them with CH3CN Gibbs layer at the air/water interface with polarization SFG-VS. This study demonstrated that the hydrogen bond network is different in the Langmuir monolayer of 5CT, C18CN from CH3CN Gibbs layer at the air/water interface which showed two different water structures on the different surface layer. The results provided a deeper insight into understanding the hydrogen bond on the interfaces.

  19. Enhanced formation of thermal donors in irradiated germanium: local vibrational mode spectroscopy

    International Nuclear Information System (INIS)

    Oxygen-rich Ge samples were irradiated with fast electrons (E = 4 MeV) at 80 deg C and subjected to isochronal (100-340 deg C) and isothermal (350 deg C) annealings. Infra-red absorption spectra were measured at room temperature. Preliminary irradiation is found to enhance strongly the development of the absorption bands in the range 600 and 780 cm-1 upon heating the Ge crystals at 350 deg C. The bands are assigned to local vibrational modes (LVM) of thermal donors (TD). It is inferred from the annealing studies that a radiation-induced complex with the LVM at about 770-780 cm-1 is likely responsible for the enhanced growth of TD. The oxygen dimer is suggested to be such a complex

  20. Identification and characterization of phyllosilicate minerals from Republic of Macedonia by vibrational spectroscopy

    International Nuclear Information System (INIS)

    Identification and characterization of several phyllosilicate minerals collected from the Republic of Macedonia: Mg3Si2O5(OH)4; antigorite, (Mg,Fe2+)3Si2O5(OH)4; talc, Mg3Si4O10(OH)2; clinochlore, (Mg,Fe2+)5Al(Si3Al)O10(OH)8; cymrite, BaAl2Si2O8·H2O; muscovite, KAl2(Si3Al)O10(OH,F)2; phlogopite, KMg3(Si3Al)O10(F, OH)2; montmorillonite, (Na,Ca)0..33(Al, Mg)2Si4O10(OH)2·nH2O; sherindanite, (Mg,Al)6(Si,Al)4O10(OH)8 and biotite, K(Mg,Fe2+)3AlSiO10(OH,F)2 is performed using their infrared and Raman vibrational spectra. In contrast to Raman spectra, the above-mentioned minerals showed IR spectral similarities in the region bellow 1200 cm-1 mainly due to their common structural characteristics. The bands appearing in the 1100-900 cm-1 spectral region were prescribed to ν(Si-O-Si)modes, whereas most of the lower-frequency bands were interpreted as either δ(OH) or δ(Si-O-Si) vibrations. The presence of sharp peak at 1630 cm-1, registered only in the infrared spectra of cymrite and montmorillonite, enables to discriminate between hydroxide and water-containing minerals. Various types of ion substitutions, which appear in this group of minerals, sometimes could led to wrong identification. Therefore, the authenticity of the three samples, muscovite (Nezhlevo), biotite (Chanishte) and sherindanite (Sivets), was checked with results obtained from chemical composition analysis. (Author)

  1. Equivalent linearization technique for quantum anharmonic oscillators

    International Nuclear Information System (INIS)

    Quantum dynamics means studying the evolution of an initially prescribed wave function. This is analytically tractable for special wavefunctions for the simplest of the situations—free particle and simple harmonic oscillator. The purely anharmonic oscillators are virtually impossible to handle. We show here that the study of Ehrenfest's equation provides an alternative route to studying quantum dynamics. It does not give exact answers but clarifies some basic aspects of quantum dynamics by providing a prescription for constructing equivalent simple harmonic oscillators. (paper)

  2. Application of multivariate analysis and vibrational spectroscopy in classification of biological systems

    Science.gov (United States)

    Salman, A.; Shufan, E.; Lapidot, I.; Tsror, L.; Zeiri, L.; Sahu, R. K.; Moreh, R.; Mordechai, S.; Huleihel, M.

    2015-12-01

    Fourier Transform Infrared (FTIR) and Raman spectroscopies have emerged as powerful tools for chemical analysis. This is due to their ability to provide detailed information about the spatial distribution of chemical composition at the molecular level. A biological sample, i.e. bacteria or fungi, has a typical spectrum. This spectral fingerprint, characterizes the sample and can therefore be used for differentiating between biology samples which belong to different groups, i.e., several different isolates of a given fungi. When the spectral differences between the groups are minute, multivariate analysis should be used to provide a good differentiation. We hereby review several results which demonstrate the differentiation success obtained by combining spectroscopy measurements and multivariate analysis.

  3. Ultrafast Strong-Field Vibrational Dynamics Studied by Femtosecond Extreme-Ultraviolet Transient Absorption Spectroscopy

    OpenAIRE

    Hosler, Erik Robert

    2013-01-01

    Femtosecond time-resolved extreme-ultraviolet core-level absorption spectroscopy has developed into a powerful tool for investigating chemical dynamics due to its sensitivity for detecting changes in electronic structure. By probing the core-levels of atoms and molecules, dynamics may be monitored with elemental specificity, as well as localized sensitivity to the oxidation state around the atomic absorber. Previous experiments with this technique demonstrated the capability to quantitatively...

  4. In situ investigations of biological molecules using vibrational sum-frequency-generation spectroscopy

    OpenAIRE

    Howell, Caitlin

    2011-01-01

    The molecular-level understanding of biological molecules on solid surfaces is critical in areas including medicine, biologically-based industry, and the development of biotechnologies. In order to gain further knowledge of the orientation and organization of biological molecules adsorbed on surfaces, we used the label-free, interface-specific technique of sum-frequency generation (SFG) spectroscopy. This technique has the distinct advantage of being able to be operated in situ as well as ex ...

  5. X-ray and vibrational spectroscopy of manganese complexes relevant to the oxygen-evolving complex of photosynthesis

    International Nuclear Information System (INIS)

    Manganese model complexes, relevant to the oxygen-evolving complex (OEC) in photosynthesis, were studied with Mn K-edge X-ray absorption near-edge spectroscopy (XANES), Mn Kb X-ray emission spectroscopy (XES), and vibrational spectroscopy. A more detailed understanding was obtained of the influence of nuclearity, overall structure, oxidation state, and ligand environment of the Mn atoms on the spectra from these methods. This refined understanding is necessary for improving the interpretation of spectra of the OEC. Mn XANES and Kb XES were used to study a di-(mu)-oxo and a mono-(mu)-oxo di-nuclear Mn compound in the (III,III), (III,IV), and (IV,IV) oxidation states. XANES spectra show energy shifts of 0.8 - 2.2 eV for 1-electron oxidation-state changes and 0.4 - 1.8 eV for ligand-environment changes. The shifts observed for Mn XES spectra were approximately 0.21 eV for oxidation state-changes and only approximately 0.04 eV for ligand-environment changes. This indicates that Mn Kb XES i s more sensitive to the oxidation state and less sensitive to the ligand environment of the Mn atoms than XANES. These complimentary methods provide information about the oxidation state and the ligand environment of Mn atoms in model compounds and biological systems. A versatile spectroelectrochemical apparatus was designed to aid the interpretation of IR spectra of Mn compounds in different oxidation states. The design, based on an attenuated total reflection device, permits the study of a wide spectral range: 16,700 (600 nm) - 225

  6. X-ray and vibrational spectroscopy of manganese complexes relevant to the oxygen-evolving complex of photosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Visser, Hendrik

    2001-05-16

    Manganese model complexes, relevant to the oxygen-evolving complex (OEC) in photosynthesis, were studied with Mn K-edge X-ray absorption near-edge spectroscopy (XANES), Mn Kb X-ray emission spectroscopy (XES), and vibrational spectroscopy. A more detailed understanding was obtained of the influence of nuclearity, overall structure, oxidation state, and ligand environment of the Mn atoms on the spectra from these methods. This refined understanding is necessary for improving the interpretation of spectra of the OEC. Mn XANES and Kb XES were used to study a di-(mu)-oxo and a mono-(mu)-oxo di-nuclear Mn compound in the (III,III), (III,IV), and (IV,IV) oxidation states. XANES spectra show energy shifts of 0.8 - 2.2 eV for 1-electron oxidation-state changes and 0.4 - 1.8 eV for ligand-environment changes. The shifts observed for Mn XES spectra were approximately 0.21 eV for oxidation state-changes and only approximately 0.04 eV for ligand-environment changes. This indicates that Mn Kb XES i s more sensitive to the oxidation state and less sensitive to the ligand environment of the Mn atoms than XANES. These complimentary methods provide information about the oxidation state and the ligand environment of Mn atoms in model compounds and biological systems. A versatile spectroelectrochemical apparatus was designed to aid the interpretation of IR spectra of Mn compounds in different oxidation states. The design, based on an attenuated total reflection device, permits the study of a wide spectral range: 16,700 (600 nm) - 225

  7. Quantum dissipative effect of one dimension coupled anharmonic oscillator

    International Nuclear Information System (INIS)

    Quantum dissipative effect of one dimension coupled anharmonic oscillator is investigated. The systems are two coupled harmonic oscillator with the different masses. The dissipative effect is studied based on the quantum state diffusion formalism. The result show that the anharmonic effect increase the amplitude but the lifetime of the oscillation depend on the damping coefficient and do not depend on the temperature

  8. Quantum dissipative effect of one dimension coupled anharmonic oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Sulaiman, A. [Badan Pengkajian dan Penerapan Teknologi, BPPT Bld. II (19thfloor), Jl. M.H. Thamrin 8, Jakarta 10340 (Indonesia); Indonesia Center for Theoretical and Mathematical Physics (ICTMP), Jl. Ganesha 10, Bandung 40132 (Indonesia); Zen, Freddy P. [Theoretical Physics Laboratory (THEPI), Department of Physics, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia); Indonesia Center for Theoretical and Mathematical Physics (ICTMP), Jl. Ganesha 10, Bandung 40132 (Indonesia)

    2015-04-16

    Quantum dissipative effect of one dimension coupled anharmonic oscillator is investigated. The systems are two coupled harmonic oscillator with the different masses. The dissipative effect is studied based on the quantum state diffusion formalism. The result show that the anharmonic effect increase the amplitude but the lifetime of the oscillation depend on the damping coefficient and do not depend on the temperature.

  9. Dynamics of Rhodobacter capsulatus [2Fe-2S] Ferredoxin VI and Aquifex aeolicus Ferredoxin 5 Via Nuclear Resonance Vibrational Spectroscopy (NRVS) and Resonance Raman Spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Yuming; Tan, Ming-Liang; Ichiye, Toshiko; Wang, Hongxin; Guo, Yisong; Smith, Matt C.; Meyer, Jacques; Sturhahn, Wolfgang; Alp, E. E.; Zhao, Jiyong; Yoda, Yoshitaka; Cramer, Stephen P.

    2008-06-24

    We have used (57)Fe nuclear resonance vibrational spectroscopy (NRVS) to study the Fe(2)S(2)(Cys)(4) sites in oxidized and reduced [2Fe-2S] ferredoxins from Rhodobacter capsulatus (Rc FdVI) and Aquifex aeolicus (Aa Fd5). In the oxidized forms, nearly identical NRVS patterns are observed, with strong bands from Fe-S stretching modes peaking around 335 cm(-1), and additional features observed as high as the B(2u) mode at approximately 421 cm(-1). Both forms of Rc FdVI have also been investigated by resonance Raman (RR) spectroscopy. There is good correspondence between NRVS and Raman frequencies, but because of different selection rules, intensities vary dramatically between the two kinds of spectra. For example, the B(3u) mode at approximately 288 cm(-1), attributed to an asymmetric combination of the two FeS(4) breathing modes, is often the strongest resonance Raman feature. In contrast, it is nearly invisible in the NRVS, as there is almost no Fe motion in such FeS(4) breathing. NRVS and RR analysis of isotope shifts with (36)S-substituted into bridging S(2-) ions in Rc FdVI allowed quantitation of S(2-) motion in different normal modes. We observed the symmetric Fe-Fe stretching mode at approximately 190 cm(-1) in both NRVS and RR spectra. At still lower energies, the NRVS presents a complex envelope of bending, torsion, and protein modes, with a maximum at 78 cm(-1). The (57)Fe partial vibrational densities of states (PVDOS) were interpreted by normal-mode analysis with optimization of Urey-Bradley force fields. Progressively more complex D(2h) Fe(2)S(2)S'(4), C(2h) Fe(2)S(2)(SCC)(4), and C(1) Fe(2)S(2)(Cys)(4) models were optimized by comparison with the experimental spectra. After modification of the CHARMM22 all-atom force field by the addition of refined Fe-S force constants, a simulation employing the complete protein structure was used to reproduce the PVDOS, with better results in the low frequency protein mode region. This process was then repeated

  10. The Clusters-in-a-Liquid Approach for Solvation: New Insights from the Conformer Specific Gas Phase Spectroscopy and Vibrational Optical Activity Spectroscopy.

    Science.gov (United States)

    Perera, Angelo S; Thomas, Javix; Poopari, Mohammad R; Xu, Yunjie

    2016-01-01

    Vibrational optical activity spectroscopies, namely vibrational circular dichroism (VCD) and Raman optical activity (ROA), have been emerged in the past decade as powerful spectroscopic tools for stereochemical information of a wide range of chiral compounds in solution directly. More recently, their applications in unveiling solvent effects, especially those associated with water solvent, have been explored. In this review article, we first select a few examples to demonstrate the unique sensitivity of VCD spectral signatures to both bulk solvent effects and explicit hydrogen-bonding interactions in solution. Second, we discuss the induced solvent chirality, or chiral transfer, VCD spectral features observed in the water bending band region in detail. From these chirality transfer spectral data, the related conformer specific gas phase spectroscopic studies of small chiral hydration clusters, and the associated matrix isolation VCD experiments of hydrogen-bonded complexes in cold rare gas matrices, a general picture of solvation in aqueous solution emerges. In such an aqueous solution, some small chiral hydration clusters, rather than the chiral solutes themselves, are the dominant species and are the ones that contribute mainly to the experimentally observed VCD features. We then review a series of VCD studies of amino acids and their derivatives in aqueous solution under different pHs to emphasize the importance of the inclusion of the bulk solvent effects. These experimental data and the associated theoretical analyses are the foundation for the proposed "clusters-in-a-liquid" approach to account for solvent effects effectively. We present several approaches to identify and build such representative chiral hydration clusters. Recent studies which applied molecular dynamics simulations and the subsequent snapshot averaging approach to generate the ROA, VCD, electronic CD, and optical rotatory dispersion spectra are also reviewed. Challenges associated with the

  11. Sum frequency generation vibrational spectroscopy at solid gas interfaces: CO adsorption on Pd model catalysts at ambient pressure

    Science.gov (United States)

    Rupprechter, Günther; Unterhalt, Holger; Morkel, Matthias; Galletto, Paolo; Hu, Linjie; Freund, Hans-Joachim

    2002-04-01

    Carbon monoxide adsorption on Pd(1 1 1) and Pd nanoparticles supported by Al 2O 3/NiAl(1 1 0) was examined by vibrational sum frequency generation spectroscopy from 10 -8 to 1000 mbar, and from 100 to 400 K. Identical CO saturation structures were observed on Pd(1 1 1) under ultrahigh vacuum (˜10 -7 mbar, 95 K) and at high pressure (e.g. ⩾1 mbar, 190 K) with no indications of pressure-induced surface rearrangements. Special attention was paid to experimental artifacts that may occur under elevated pressure and may be misinterpreted as "high pressure effects". Vibrational spectra of CO on defect-rich Pd(1 1 1) exhibited an additional peak that originated from CO bound to defect (step or edge) sites. The CO adsorbate structure on supported Pd nanoparticles was different from Pd(1 1 1) but more similar to stepped Pd(1 1 1). At low pressure (10 -7 mbar CO) the adsorbate structure depended strongly on the Pd morphology revealing specific differences in the adsorption properties of supported nanoparticles and single crystal surfaces. At high pressure (e.g. 200 mbar CO) these differences were even more pronounced. Prominent high coverage CO structures on Pd(1 1 1) could not be established on Pd particles. However, in spite of structural differences between well faceted and rough Pd nanoparticles nearly identical adsorption site occupancies were observed in both cases at 200 mbar CO. Initial tests of the catalytic activity of Pd/Al 2O 3/NiAl(1 1 0) for ethylene hydrogenation at 1 bar revealed a remarkable activity and stability of the model system with catalytic properties similar to impregnated catalysts.

  12. 3D Motions of Iron in Six-Coordinate {FeNO}(7) Hemes by Nuclear Resonance Vibration Spectroscopy.

    Science.gov (United States)

    Peng, Qian; Pavlik, Jeffrey W; Silvernail, Nathan J; Alp, E Ercan; Hu, Michael Y; Zhao, Jiyong; Sage, J Timothy; Scheidt, W Robert

    2016-04-25

    The vibrational spectrum of a six-coordinate nitrosyl iron porphyrinate, monoclinic [Fe(TpFPP)(1-MeIm)(NO)] (TpFPP=tetra-para-fluorophenylporphyrin; 1-MeIm=1-methylimidazole), has been studied by oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS). The crystal was oriented to give spectra perpendicular to the porphyrin plane and two in-plane spectra perpendicular or parallel to the projection of the FeNO plane. These enable assignment of the FeNO bending and stretching modes. The measurements reveal that the two in-plane spectra have substantial differences that result from the strongly bonded axial NO ligand. The direction of the in-plane iron motion is found to be largely parallel and perpendicular to the projection of the bent FeNO on the porphyrin plane. The out-of-plane Fe-N-O stretching and bending modes are strongly mixed with each other, as well as with porphyrin ligand modes. The stretch is mixed with v50 as was also observed for dioxygen complexes. The frequency of the assigned stretching mode of eight Fe-X-O (X=N, C, and O) complexes is correlated with the Fe-XO bond lengths. The nature of highest frequency band at ≈560 cm(-1) has also been examined in two additional new derivatives. Previously assigned as the Fe-NO stretch (by resonance Raman), it is better described as the bend, as the motion of the central nitrogen atom of the FeNO group is very large. There is significant mixing of this mode. The results emphasize the importance of mode mixing; the extent of mixing must be related to the peripheral phenyl substituents. PMID:26999733

  13. High-pressure vibrational and polymorphic response of 1,1-diamino-2,2-dinitroethene single crystals: Raman spectroscopy.

    Science.gov (United States)

    Dreger, Zbigniew A; Tao, Yuchuan; Gupta, Yogendra M

    2014-07-10

    Raman spectroscopy was used to examine the vibrational and polymorphic behavior of 1,1-diamino-2,2-dinitroethene (FOX-7) to elucidate its structural and chemical stability under high pressure. Measurements were performed on single crystals compressed in a diamond anvil cell, and data were obtained over the entire frequency range of FOX-7 Raman activity. Several new features were observed with increase of pressure: (i) new vibrational peaks and discontinuity in the shifts of the peaks at 2 and 4.5 GPa, (ii) apparent coupling or mixing of several modes, and (iii) changes in the NH2 stretching spectral shape and modes shift. The spectral changes at 2 GPa, in contrast to previous reports, involved only a few peaks and likely resulted from a small molecular transformation. In contrast, changes at 4.5 GPa involved most of the modes, and the pressure for the onset and completion of the changes depended on the pressure medium. A large pressure hysteresis regarding the changes at 4.5 GPa implies a reconstructive transformation. We suggest that this transformation reflects a change in the balance between interlayer (van der Waals) and in-layer (H-bonding) interactions. Despite these transformations, further compression to 40 GPa and subsequent release of pressure did not cause any irreversible changes. This finding implies that FOX-7 has remarkable chemical stability under high pressures. The observed coupling between the various modes with increasing pressure was analyzed within the Fermi resonance model. The potential implication of the coupling of modes for shock insensitivity of FOX-7 is briefly discussed. PMID:24941445

  14. Vibrational spectroscopy and analytical electron microscopy studies of Fe-V-O and In-V-O thin films

    International Nuclear Information System (INIS)

    Orthovanadate (M3+VO4; M= Fe, In) and vanadate (Fe2V4O13) thin films were prepared using sol-gel synthesis and dip coating deposition. Using analytical electron microscopy (AEM), the chemical composition and the degree of crystallization of the phases present in the thin Fe-V-O films were investigated. TEM samples were prepared in both orientations: parallel (plan view) and perpendicular (cross section) to the substrate. In the first stages of crystallization, when the particle sizes were in the nanometer range, the classical identification of phases using electron diffraction was not possible. Instead of measuring d values, experimentally selected area electron diffraction (SAED) patterns were compared to calculated (simulated) patterns in order to determine the phase composition. The problems of evaluating the ratio of amorphous and crystalline phases in thin films are reported. Results of TEM and XRD as well as IR and Raman spectroscopy showed that the films made at lower temperatures (300 oC) consisted of nanograins embedded in the dominating amorphous phase. Characteristic vibrational spectra allowed to distinguish between the different crystalline phases, since the IR and Raman bands showed broadening due to the decreasing particle size of the films thermally treated at lower temperatures. Vibrational analysis also showed that the electrochemical cycling of crystalline films led to spectra that were in close agreement with the spectra of the nanocrystalline films prepared at lower temperatures. The formation of a nanocrystalline structure is therefore a prerequisite for obtaining a higher charging/discharging stability of Fe-V-O and In-V-O films. (author)

  15. Far-infrared VRT spectroscopy of the water dimer: Characterization of the 20 μm out-of-plane librational vibration

    International Nuclear Information System (INIS)

    We report the first high-resolution spectra for the out-of-plane librational vibration in the water dimer. Three vibrational subbands comprising a total of 188 transitions have been measured by diode laser spectroscopy near 500 cm−1 and assigned to (H2O)2 libration-rotation-tunneling eigenstates. The band origin for the Ka = 1 subband is ~524 cm−1. Librational excitation increases the interchange and bifurcation hydrogen bond rearrangement tunneling splittings by factors of 3-5 and 4-40, respectively. Analysis of the rotational constants obtained from a nonlinear least squares fit indicates that additional external perturbations to the energy levels are likely

  16. Towards the Limits of Vibrational Circular Dichroism Spectroscopy: VCD Spectra of Some Alkyl Vinylethers.

    Science.gov (United States)

    Zinna, Francesco; Pescitelli, Gennaro

    2016-02-01

    Three alkyl vinylethers from our collection of chiral samples were investigated through VCD spectroscopy, in combination with Density Functional Theory (DFT) calculations. Despite the simplicity of the compounds, reproducing all the spectral features is an involved task, since the many significantly populated conformers contribute to the total VCD spectrum with bands which often have opposite signatures. Nevertheless, we show that certain bands can be satisfactorily reproduced by calculation and therefore they may be employed for the determination of absolute configuration in these and similar compounds, for which no simple alternative method is available. Chirality 28:143-146, 2016. © 2015 Wiley Periodicals, Inc. PMID:26634887

  17. Statistical strategies to reveal potential vibrational markers for in vivo analysis by confocal Raman spectroscopy

    Science.gov (United States)

    Oliveira Mendes, Thiago de; Pinto, Liliane Pereira; Santos, Laurita dos; Tippavajhala, Vamshi Krishna; Téllez Soto, Claudio Alberto; Martin, Airton Abrahão

    2016-07-01

    The analysis of biological systems by spectroscopic techniques involves the evaluation of hundreds to thousands of variables. Hence, different statistical approaches are used to elucidate regions that discriminate classes of samples and to propose new vibrational markers for explaining various phenomena like disease monitoring, mechanisms of action of drugs, food, and so on. However, the technical statistics are not always widely discussed in applied sciences. In this context, this work presents a detailed discussion including the various steps necessary for proper statistical analysis. It includes univariate parametric and nonparametric tests, as well as multivariate unsupervised and supervised approaches. The main objective of this study is to promote proper understanding of the application of various statistical tools in these spectroscopic methods used for the analysis of biological samples. The discussion of these methods is performed on a set of in vivo confocal Raman spectra of human skin analysis that aims to identify skin aging markers. In the Appendix, a complete routine of data analysis is executed in a free software that can be used by the scientific community involved in these studies.

  18. Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy

    International Nuclear Information System (INIS)

    An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2–3 cm−1. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance

  19. Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy

    Science.gov (United States)

    Reppert, Mike; Tokmakoff, Andrei

    2015-08-01

    An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2-3 cm-1. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance.

  20. Distinguishing gramicidin D conformers through two-dimensional infrared spectroscopy of vibrational excitons

    Science.gov (United States)

    Stevenson, Paul; Tokmakoff, Andrei

    2015-06-01

    Gramicidin D is a short peptide which dimerizes to form helical pores, adopting one of two conformations in the process. These conformations differ primarily in number of residues per turn and the hydrogen-bond registry between rungs of the helix. Using amide I 2D infrared (IR) and FTIR, we have demonstrated that it is possible to distinguish between the different conformers of gramicidin D in solution. We show that the spectra observed for this helical peptide bear no resemblance to the spectra of α- or 310-helices and that while the FTIR spectra appear similar to spectra of β-sheets, 2D IR reveals that the observed resonances arise from vibrational modes unlike those observed in β-sheets. We also present an idealized model which reproduces the experimental data with high fidelity. This model is able to explain the polarization-dependence of the experimental 2D IR data. Using this model, we show the coupling between the rungs of the helix dominates the spectra, and as a consequence of this, the number of residues per turn can greatly influence the amide I spectra of gramicidin D.

  1. Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Reppert, Mike [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States); Tokmakoff, Andrei, E-mail: tokmakoff@uchicago.edu [Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States)

    2015-08-14

    An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2–3 cm{sup −1}. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance.

  2. Structural study of human growth hormone-releasing factor fragment (1?29) by vibrational spectroscopy

    Science.gov (United States)

    Carmona, P.; Molina, M.; Lasagabaster, A.

    1995-05-01

    The conformational structure of fragment 1-29 of human growth hormone releasing factor, hGHRF (1-29), in aqueous solution and in the solid state is investigated by infrared and Raman spectroscopy. The polypeptide backbone is found to be unordered in the solid state. However, the spectra of the peptide prepared as 5% (w/w) aqueous solutions show that approximately 28% of the peptide is involved in intermolecular β-sheet aggregation. The remainder of the peptide exists largely as disordered and β-sheet conformations with a small portion of α-helices. Tyrosine residues are found to be exposed to the solvent. The secondary structures are quantitatively examined through infrared spectroscopy, the conformational percentages being near those obtained by HONDAet al. [ Biopolymers31, 869 (1991)] using circular dichroism. The fast hydrogen/deuterium exchange in peptide groups and the absence of any NMR sign indicative of ordered structure [ G. M. CLOREet al., J. Molec. Biol.191, 553 (1986)] support that the solution conformations of the non-aggregated peptide interconvert in dynamic equilibrium. Some physiological advantages that may derive from this conformational flexibility are also discussed

  3. Final Technical Report Structural Dynamics in Complex Liquids Studied with Multidimensional Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tokmakoff, Andrei [Univ. of Chicago, IL (United States); Fiechtner, Gregory J. [Univ. of Chicago, IL (United States)

    2015-12-10

    This grant supported work in the Tokmakoff lab at the University of Chicago aimed at understanding the fundamental properties of water at a molecular level, and how water participates in proton transport in aqueous media. The physical properties of water and aqueous solutions are inextricably linked with efforts to develop new sustainable energy sources. Energy conversion, storage, and transduction processes, particularly those that occur in biology and soft matter, make use of water for the purpose of storing and moving charge. Water’s unique physical and chemical properties depend on the ability of water molecules to participate in up to four hydrogen bonds, and the rapid fluctuations and ultrafast energy dissipation of its hydrogenbonded networks. Our work during the grant period led to advances in four areas: (1) the generation of short pulses of broadband infrared light (BBIR) for use in time-resolved twodimensional spectroscopy (2D IR), (2) the investigation of the spectroscopy and transport of excess protons in water, (3) the study of aqueous hydroxide to describe the interaction of the ion and water and the dynamics of proton transfer, and (4) the coupled motion of water and its hydrogen-bonding solutes.

  4. Anharmonicity of multi-octupole-phonon excitations in $^{208}$Pb: analysis with multi-reference covariant density functional theory and subbarrier fusion of $^{16}$O+$^{208}$Pb

    CERN Document Server

    Yao, J M

    2016-01-01

    We discuss anharmonicity of the multi-octupole-phonon states in $^{208}$Pb based on a covariant density functional theory, by fully taking into account the interplay between the quadrupole and the octupole degrees of freedom. Our results indicate the existence of a large anharmonicity in the transition strengths, even though the excitation energies are similar to those in the harmonic limit. We also show that the quadrupole-shape fluctuation significantly enhances the fragmentation of the two-octupole-phonon states in $^{208}$Pb. Using those transition strengths as inputs to coupled channels calculations, we then discuss the fusion reaction of $^{16}$O+$^{208}$Pb at energies around the Coulomb barrier. We show that the anharmonicity of the octupole vibrational excitation considerably improves previous coupled-channels calculations in the harmonic oscillator limit, significantly reducing the height of the main peak in the fusion barrier distribution.

  5. A variable-temperature scanning tunneling microscope capable of single-molecule vibrational spectroscopy

    International Nuclear Information System (INIS)

    The design and performance of a variable-temperature scanning tunneling microscope (STM) is presented. The microscope operates from 8 to 350 K in ultrahigh vacuum. The thermally compensated STM is suspended by springs from the cold tip of a continuous flow cryostat and is completely surrounded by two radiation shields. The design allows for in situ dosing and irradiation of the sample as well as for the exchange of samples and STM tips. With the STM feedback loop off, the drift of the tip-sample spacing is approximately 0.001 Angstrom/min at 8 K. It is demonstrated that the STM is well-suited for the study of atomic-scale chemistry over a wide temperature range, for atomic-scale manipulation, and for single-molecule inelastic electron tunneling spectroscopy (IETS). copyright 1999 American Institute of Physics

  6. Vibrational spectroscopy study of doped-CaZrO3 ceramics

    International Nuclear Information System (INIS)

    Doped-CaZrO3 materials were prepared by solid-state reaction. The substitution was either on the A site of the perovskite (Mg, Ca, Ba) or on the B site (Ti, Hf). The samples were pre-calcined and sintered at 1673 K for 6 h. They were analysed using Fourier transform-infrared spectroscopy. The microwave dielectric function was determined by a Kramers-Kronig analysis. The reflectance spectra were then adjusted using the classical dispersion equations taking into account the longitudinal/transverse optic (LO/TO) modes splitting. The calculated values of the Q factor match very well with the measured ones and follow a linear tendency depending on the reduced mass of the oscillator composed of Ca- and Zr-like virtual-ions. The first phonon mode is (as in many perovskite) the most incident mode on the dielectric losses. Numerous modes' parameters are dependent on both the mass of the dopant and its concentration

  7. Nanoscale chemical and mechanical characterization of thin films:sum frequency generation (SFG) vibrational spectroscopy at buriedinterfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kweskin, S.J.

    2006-05-19

    Sum frequency generation (SFG) surface vibrational spectroscopy was used to characterize interfaces pertinent to current surface engineering applications, such as thin film polymers and novel catalysts. An array of advanced surface science techniques like scanning probe microscopy (SPM), x-ray photoelectron spectroscopy (XPS), gas chromatography (GC) and electron microscopy were used to obtain experimental measurements complementary to SFG data elucidating polymer and catalyst surface composition, surface structure, and surface mechanical behavior. Experiments reported in this dissertation concentrate on three fundamental questions: (1) How does the interfacial molecular structure differ from that of the bulk in real world applications? (2) How do differences in chemical environment affect interface composition or conformation? (3) How do these changes correlate to properties such as mechanical or catalytic performance? The density, surface energy and bonding at a solid interface dramatically alter the polymer configuration, physics and mechanical properties such as surface glass transition, adhesion and hardness. The enhanced sensitivity of SFG at the buried interface is applied to three systems: a series of acrylates under compression, the compositions and segregation behavior of binary polymer polyolefin blends, and the changes in surface structure of a hydrogel as a function of hydration. In addition, a catalytically active thin film of polymer coated nanoparticles is investigated to evaluate the efficacy of SFG to provide in situ information for catalytic reactions involving small mass adsorption and/or product development. Through the use of SFG, in situ total internal reflection (TIR) was used to increase the sensitivity of SFG and provide the necessary specificity to investigate interfaces of thin polymer films and nanostructures previously considered unfeasible. The dynamic nature of thin film surfaces is examined and it is found that the non

  8. Theory of sum-frequency generation spectroscopy of adsorbed molecules using the density matrix method-broadband vibrational sum-frequency generation and applications

    International Nuclear Information System (INIS)

    A generalized theory of frequency- and time-resolved vibrational sum-frequency generation (SFG) spectroscopy of adsorbates at surfaces is presented using the density matrix formalism. Our theoretical treatment is specifically aimed at addressing issues that accompany the relatively novel SFG approach using broadband infrared pulses. The ultrashort duration of these pulses makes them ideally suited for time-resolved investigations, for which we present a complete theoretical treatment. A second key characteristic of these pulses is their large bandwidth and high intensity, which allow for highly non-linear effects, including vibrational ladder climbing of surface vibrations. We derive general expressions relating the density matrix to SFG spectra, and apply these expressions to specific experimental results by solving the coupled optical Bloch equations of the density matrix elements. Thus, we can theoretically reproduce recent experimentally demonstrated hot band SFG spectra using femtosecond broadband infrared excitation of carbon monoxide (CO) on a Ru(001) surface

  9. Rapid vibrational and rotational energy-transfer rates in heated carbon dioxide collisions by double-resonance laser spectroscopy

    International Nuclear Information System (INIS)

    Rates for resonant vibrational and rotational energy transfer from the 001 state by CO2 + CO2 collisions have been measured. All data were obtained by double resonance spectroscopy with CO2 lasers in a 2.5 meter absorption cell at 7000K. Results for rotation transfer include pumped-level relaxation and the response of other 001 levels with ΔJ up to 18. These data are compared to four relevant collision models via a 35-level rate equation analysis. Sequence-band (002 → 101) and hot-band (011 → 110) lasting have been used to observe resonant nu3-transfer relaxation involving 001 + 001 reversible 002 + 000, 001 + 100 reversible 101 + 000, and 001 + 010 reversible 011 + 000. A multilevel rate analysis has been utilized to determine the rate coefficients for 001 going to the 002, the 101, and the 011 levels. Part of the hot-band data has been interpreted as due to 110 + 000 reversible 100 + 010, and the associated rate constant has been estimated. The results of the study are compared to the theory and to other experiments

  10. Rapid vibrational and rotational energy-transfer rates in heated carbon dioxide collisions by double-resonance laser spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Thomason, M.D.

    1982-07-01

    Rates for resonant vibrational and rotational energy transfer from the 001 state by CO/sub 2/ + CO/sub 2/ collisions have been measured. All data were obtained by double resonance spectroscopy with CO/sub 2/ lasers in a 2.5 meter absorption cell at 700/sup 0/K. Results for rotation transfer include pumped-level relaxation and the response of other 001 levels with ..delta..J up to 18. These data are compared to four relevant collision models via a 35-level rate equation analysis. Sequence-band (002 ..-->.. 101) and hot-band (011 ..-->.. 110) lasting have been used to observe resonant nu/sub 3/-transfer relaxation involving 001 + 001 reversible 002 + 000, 001 + 100 reversible 101 + 000, and 001 + 010 reversible 011 + 000. A multilevel rate analysis has been utilized to determine the rate coefficients for 001 going to the 002, the 101, and the 011 levels. Part of the hot-band data has been interpreted as due to 110 + 000 reversible 100 + 010, and the associated rate constant has been estimated. The results of the study are compared to the theory and to other experiments.

  11. Vibrational properties of epitaxial Bi{sub 4}Te{sub 3} films as studied by Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hao; Pan, Wenwu; Chen, Qimiao; Wu, Xiaoyan [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049 (China); Song, Yuxin, E-mail: songyuxin@mail.sim.ac.cn, E-mail: shumin@chalmers.se; Gong, Qian [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Lu, Pengfei [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Wang, Shumin, E-mail: songyuxin@mail.sim.ac.cn, E-mail: shumin@chalmers.se [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China); Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg (Sweden)

    2015-08-15

    Bi{sub 4}Te{sub 3}, as one of the phases of the binary Bi–Te system, shares many similarities with Bi{sub 2}Te{sub 3}, which is known as a topological insulator and thermoelectric material. We report the micro-Raman spectroscopy study of 50 nm Bi{sub 4}Te{sub 3} films on Si substrates prepared by molecular beam epitaxy. Raman spectra of Bi{sub 4}Te{sub 3} films completely resolve the six predicted Raman-active phonon modes for the first time. Structural features and Raman tensors of Bi{sub 4}Te{sub 3} films are introduced. According to the wavenumbers and assignments of the six eigenpeaks in the Raman spectra of Bi{sub 4}Te{sub 3} films, it is found that the Raman-active phonon oscillations in Bi{sub 4}Te{sub 3} films exhibit the vibrational properties of those in both Bi and Bi{sub 2}Te{sub 3} films.

  12. Chiral recognition between lactic acid derivatives and an aromatic alcohol in a supersonic expansion: electronic and vibrational spectroscopy.

    Science.gov (United States)

    Seurre, N; Le Barbu-Debus, K; Lahmani, F; Zehnacker, A; Borho, N; Suhm, M A

    2006-02-28

    Jet-cooled diastereoisomeric complexes formed between a chiral probe, (+/-)-2-naphthyl-1-ethanol, and chiral lactic acid derivatives have been characterised by laser-induced fluorescence and IR fluorescence-dip spectroscopy. Complexes with non chiral alpha-hydroxyesters and chiral beta-hydroxyesters have also been studied for the sake of comparison. DFT calculations have been performed to assist in the analysis of the vibrational spectra and the determination of the structures. The observed 1 : 1 complexes correspond to the addition of the hydroxy group of the chromophore on the oxygen atom of the hydroxy in alpha-position relative to the ester function. Moreover, (+/-)-methyl lactate and (+/-)-ethyl lactate complexes with (+/-)-2-naphthyl-1-ethanol show an enantioselectivity in the size of the formed adducts: while fluorescent 1 : 1 complexes are the most abundant species observed when mixing (S)-2-naphthyl-1-ethanol with (R)-methyl or ethyl lactate, they are absent in the case of the SS mixture, which only shows 1 : 2 adducts. This property has been related to steric hindrance brought by the methyl group on the hydroxy-bearing carbon atom. PMID:16482344

  13. In Situ Potentiodynamic Analysis of the Electrolyte/Silicon Electrodes Interface Reactions--A Sum Frequency Generation Vibrational Spectroscopy Study.

    Science.gov (United States)

    Horowitz, Yonatan; Han, Hui-Ling; Ross, Philip N; Somorjai, Gabor A

    2016-01-27

    The key factor in long-term use of batteries is the formation of an electrically insulating solid layer that allows lithium ion transport but stops further electrolyte redox reactions on the electrode surface, hence solid electrolyte interphase (SEI). We have studied a common electrolyte, 1.0 M LiPF6/ethylene carbonate (EC)/diethyl carbonate (DEC), reduction products on crystalline silicon (Si) electrodes in a lithium (Li) half-cell system under reaction conditions. We employed in situ sum frequency generation vibrational spectroscopy (SFG-VS) with interface sensitivity in order to probe the molecular composition of the SEI surface species under various applied potentials where electrolyte reduction is expected. We found that, with a Si(100)-hydrogen terminated wafer, a Si-ethoxy (Si-OC2H5) surface intermediate forms due to DEC decomposition. Our results suggest that the SEI surface composition varies depending on the termination of Si surface, i.e., the acidity of the Si surface. We provide the evidence of specific chemical composition of the SEI on the anode surface under reaction conditions. This supports an electrochemical electrolyte reduction mechanism in which the reduction of the DEC molecule to an ethoxy moiety plays a key role. These findings shed new light on the formation mechanism of SEI on Si anodes in particular and on SEI formation in general. PMID:26651259

  14. pH dependence of the conformation of small peptides investigated with two-dimensional vibrational spectroscopy.

    Science.gov (United States)

    Huerta-Viga, Adriana; Shaw, Daniel J; Woutersen, Sander

    2010-11-25

    We investigate how the conformation of small peptides is influenced by the presence or absence of charge on the C-terminus and on the side groups. To this purpose, the conformations of two tripeptides, with acidic and basic side groups, is determined at several pD values using two-dimensional infrared (2DIR) spectroscopy. The investigated pD values are chosen relative to the C-terminal and side-chain pK(a) values in such a way that the C-terminus and side groups are in well-defined protonation states. The measurements are analyzed quantitatively using an excitonic model for the Amide I' mode. From the vibrational coupling and the angle between the Amide I' transition dipoles obtained in this way, the dihedral angles (φ,ψ) of the central C(α) atom are determined. Interestingly, our measurements show that the backbone structure of the peptides is remarkably stable against changing the charges of both the side groups and the C-terminal carboxylate groups. This is probably a consequence of effective screening of the Coulomb interactions between the charged groups by the water molecules between them. We also find that the (φ,ψ) confidence regions obtained from 2DIR measurements can have highly irregular shapes as a consequence of the nonlinear relation between the dihedral angles and the experimentally determined Amide I' coupling and transition-dipole angle. PMID:20977228

  15. Hydrogenated graphene on Ir(111): A high-resolution electron energy loss spectroscopy study of the vibrational spectrum

    Science.gov (United States)

    Kyhl, Line; Balog, Richard; Angot, Thierry; Hornekær, Liv; Bisson, Régis

    2016-03-01

    Hydrogen atom adsorption on high-quality graphene on Ir(111) [gr/Ir(111)] is investigated using high-resolution electron energy loss spectroscopy. The evolution of the vibrational spectrum, up to 400 meV, of gr/Ir(111) upon increasing hydrogen atom exposures is measured. The two dominant binding configurations of atomic hydrogen are identified as (1) graphanelike hydrogen clusters on the parts of the graphene more strongly interacting with the Ir(111) surface and (2) dimers bound more weakly to the freestanding parts of the graphene. The graphanelike surface structures lead to increased corrugation of the graphene sheet, yielding graphane-related phonon components. Additionally, a recent theoretical prediction of the existence of a bending character for a LO/TO graphane chair phonon mode is experimentally verified. No clear evidence was found for hydrogen bound on both sides of a high-quality graphene sheet and phonon features strongly suggest interactions between graphanelike hydrogen clusters and Ir atoms in the substrate.

  16. New Insights from Sum Frequency Generation Vibrational Spectroscopy into the Interactions of Islet Amyloid Polypeptides with Lipid Membranes

    Directory of Open Access Journals (Sweden)

    Li Fu

    2016-01-01

    Full Text Available Studies of amyloid polypeptides on membrane surfaces have gained increasing attention in recent years. Several studies have revealed that membranes can catalyze protein aggregation and that the early products of amyloid aggregation can disrupt membrane integrity, increasing water permeability and inducing ion cytotoxicity. Nonetheless, probing aggregation of amyloid proteins on membrane surfaces is challenging. Surface-specific methods are required to discriminate contributions of aggregates at the membrane interface from those in the bulk phase and to characterize protein secondary structures in situ and in real time without the use of perturbing spectroscopic labels. Here, we review the most recent applications of sum frequency generation (SFG vibrational spectroscopy applied in conjunction with computational modeling techniques, a joint experimental and computational methodology that has provided valuable insights into the aggregation of islet amyloid polypeptide (IAPP on membrane surfaces. These applications show that SFG can provide detailed information about structures, kinetics, and orientation of IAPP during interfacial aggregation, relevant to the molecular mechanisms of type II diabetes. These recent advances demonstrate the promise of SFG as a new approach for studying amyloid diseases at the molecular level and for the rational drug design targeting early aggregation products on membrane surfaces.

  17. IR and Vibrational Circular Dichroism Spectroscopy of Matrine- and Artemisinin-Type Herbal Products: Stereochemical Characterization and Solvent Effects.

    Science.gov (United States)

    Zhang, Yuefei; Poopari, M Reza; Cai, Xiaoli; Savin, Aliaksandr; Dezhahang, Zahra; Cheramy, Joseph; Xu, Yunjie

    2016-04-22

    Five Chinese herbal medicines--matrine, oxymatrine, sophoridine, artemisinin, and dihydroartemisinin--were investigated using vibrational circular dichroism (VCD) experiments and density functional theory calculations to extract their stereochemical information. The three matrine-type alkaloids are available from the dry roots of Sophora flavescens and have long been used in various traditional Chinese herbal medicines to combat diseases such as cancer and cardiac arrhythmia. Artemisinin and the related dihydroartemisinin, discovered in 1979 by Professor Youyou Tu, a 2015 Nobel laureate in medicine, are effective drugs for the treatment of malaria. The VCD measurements were carried out in CDCl3 and DMSO-d6, two solvents with different dielectric constants and hydrogen-bonding characteristics. A "clusters-in-a-liquid" approach was used to model both explicit and implicit solvent effects. The studies show that effectively accounting for solvent effects is critical to using IR and VCD spectroscopy to provide unique spectroscopic features to differentiate the potential stereoisomers of these Chinese herbal medicines. PMID:27070079

  18. Evidence for Tautomerisation of Glutamine in BLUF Blue Light Receptors by Vibrational Spectroscopy and Computational Chemistry

    Science.gov (United States)

    Domratcheva, Tatiana; Hartmann, Elisabeth; Schlichting, Ilme; Kottke, Tilman

    2016-03-01

    BLUF (blue light sensor using flavin) domains regulate the activity of various enzymatic effector domains in bacteria and euglenids. BLUF features a unique photoactivation through restructuring of the hydrogen-bonding network as opposed to a redox reaction or an isomerization of the chromophore. A conserved glutamine residue close to the flavin chromophore plays a central role in the light response, but the underlying modification is still unclear. We labelled this glutamine with 15N in two representative BLUF domains and performed time-resolved infrared double difference spectroscopy. The assignment of the signals was conducted by extensive quantum chemical calculations on large models with 187 atoms reproducing the UV-vis and infrared signatures of BLUF photoactivation. In the dark state, the comparatively low frequency of 1,667 cm‑1 is assigned to the glutamine C=O accepting a hydrogen bond from tyrosine. In the light state, the signature of a tautomerised glutamine was extracted with the C=N stretch at ~1,691 cm‑1 exhibiting the characteristic strong downshift by 15N labelling. Moreover, an indirect isotope effect on the flavin C4=O stretch was found. We conclude that photoactivation of the BLUF receptor does not only involve a rearrangement of hydrogen bonds but includes a change in covalent bonds of the protein.

  19. In situ vibrational spectroscopy of thin organic films confined at the solid-solid interface

    CERN Document Server

    Haydock, S A

    2002-01-01

    Raman scattering was used to study thin films, of hexadecane, octamethyltetrasiloxane (OMCTS), 1-undecanol and Langmuir-Blodgett (LB) monolayers consisting of zinc stearate, zinc arachidate and zinc behenate, all at the solid-solid interface. This thesis contains the first unenhanced Raman spectrum of an organic monolayer confined in the contact between two solid surfaces. The LB monolayers were also investigated with sum-frequency spectroscopy in order that comparisons could be made between results from the two techniques. Thin films were confined between an optical prism and an optical lens at pressures ranging from 30 MPa to 200 MPa. I have shown that the deposited LB monolayers were conformationally ordered and that this high degree of order was retained at applied pressures of up to 200 MPa. However, the application of pressure caused the hydrocarbon chains to tilt from the surface normal. The changes observed in the overall intensity of the Raman spectra on formation of the solid-solid contact can be ex...

  20. Evidence for Tautomerisation of Glutamine in BLUF Blue Light Receptors by Vibrational Spectroscopy and Computational Chemistry

    Science.gov (United States)

    Domratcheva, Tatiana; Hartmann, Elisabeth; Schlichting, Ilme; Kottke, Tilman

    2016-01-01

    BLUF (blue light sensor using flavin) domains regulate the activity of various enzymatic effector domains in bacteria and euglenids. BLUF features a unique photoactivation through restructuring of the hydrogen-bonding network as opposed to a redox reaction or an isomerization of the chromophore. A conserved glutamine residue close to the flavin chromophore plays a central role in the light response, but the underlying modification is still unclear. We labelled this glutamine with 15N in two representative BLUF domains and performed time-resolved infrared double difference spectroscopy. The assignment of the signals was conducted by extensive quantum chemical calculations on large models with 187 atoms reproducing the UV-vis and infrared signatures of BLUF photoactivation. In the dark state, the comparatively low frequency of 1,667 cm−1 is assigned to the glutamine C=O accepting a hydrogen bond from tyrosine. In the light state, the signature of a tautomerised glutamine was extracted with the C=N stretch at ~1,691 cm−1 exhibiting the characteristic strong downshift by 15N labelling. Moreover, an indirect isotope effect on the flavin C4=O stretch was found. We conclude that photoactivation of the BLUF receptor does not only involve a rearrangement of hydrogen bonds but includes a change in covalent bonds of the protein. PMID:26947391

  1. Copper/oxide interface formation: a vibrational and electronic investigation by electron spectroscopies

    Science.gov (United States)

    Conard, T.; Ghijsen, J.; Vohs, J. M.; Thiry, P. A.; Caudano, R.; Johnson, R. L.

    1992-04-01

    In this study, we deposited copper on a MgO(100) surface at room temperature (using a Knudsen cell) and studied the interface formation using electron spectroscopy. The evolution of the AES peak intensities showed that copper grows on MgO(100) in the Stranski-Krastanov mode. In HREELS experiments, the intensity and the position of the energy loss corresponding to the MgO surface optical phonon at 80.7 meV, both decrease with increasing Cu coverage. These results agree with theoretical spectra simulated from the dielectric theory by considering a Cu 2O overlayer on a semi-infinite MgO crystal substrate at the beginning of the growth. From the HREELS data, both the formation of a homogeneous Cu metallic overlayer or a CuO overlayer on MgO can be ruled out. The synchrotron-radiation (SR) photoemission measurements were performed in the vicinity of the Cu3p3d resonance. The positions of the Cu resonance peaks as a function of Cu coverage on MgO show that at low coverage the difference in energy between the main Cu 3d peak and the resonance peak is close to that found in Cu 2O and at higher coverage close to metallic copper indicating the formation of an interacting phase at the beginning followed by the growth of metallic copper.

  2. Anharmonic potential in the oscillator representation

    International Nuclear Information System (INIS)

    In the non relativistic and relativized Schroedinger equation the Wick ordering method called the oscillator representation is proposed to calculate the energy spectrum for a wide class of potentials allowing the existence of a bound state. The oscillator representation method gives a unique regular way to describe and calculate the energy levels of ground as well as orbital and radial excitation states for a wide class of potentials. The results of the zeroth approximation oscillator representation are in good agreement with the exact values for the anharmonic potentials. The oscillator representation method was applied to the relativized Schroedinger equation too. The perturbation series converges fairly fast, i.e., the highest perturbation corrections over the interaction Hamiltonian are small enough. 29 refs.; 4 tabs. (author)

  3. The vibrational structure of (E,E’)-1,4-diphenyl-1,3-butadiene. Linear dichroism FTIR spectroscopy and quantum chemical calculations

    DEFF Research Database (Denmark)

    Hansen, Bjarke Knud Vilster; Møller, Søren; Spanget-Larsen, Jens

    2006-01-01

    The title compound (DPB) was investigated by FTIR spectroscopy in liquid solutions and by FTIR linear dichroism (LD) measurements on samples aligned in stretched polyethylene. The LD data provided experimental assignments of molecular transition moment directions and vibrational symmetries for mo...... of a nearly complete assignment of the IR active fundamentals of DPB, involving reassignment of a number of transitions. In addition, previously published Raman spectra of DPB were well predicted by the B3LYP/cc-pVTZ calculations....

  4. Vibrational sum frequency spectroscopy studies at solid/liquid interfaces : Influence of the experimental geometry in the spectral shape and enhancement

    OpenAIRE

    Liljeblad, Jonathan F.D.; Tyrode, Eric

    2012-01-01

    The influence of the experimental geometry, specifically the angles of incidence (AOI) of the exciting beams, on the enhancement of the vibrational sum frequency spectroscopy (VSFS) spectra has been systematically investigated, particularly when approaching total internal reflection (TIR) conditions. Theoretical simulations of the spectral intensity as a function of the AOI and infrared wavelength at three different polarization combinations were critically compared to experimental data obtai...

  5. In situ vibrational spectroscopy of thin organic films confined at the solid-solid interface

    International Nuclear Information System (INIS)

    Raman scattering was used to study thin films, of hexadecane, octamethyltetrasiloxane (OMCTS), 1-undecanol and Langmuir-Blodgett (LB) monolayers consisting of zinc stearate, zinc arachidate and zinc behenate, all at the solid-solid interface. This thesis contains the first unenhanced Raman spectrum of an organic monolayer confined in the contact between two solid surfaces. The LB monolayers were also investigated with sum-frequency spectroscopy in order that comparisons could be made between results from the two techniques. Thin films were confined between an optical prism and an optical lens at pressures ranging from 30 MPa to 200 MPa. I have shown that the deposited LB monolayers were conformationally ordered and that this high degree of order was retained at applied pressures of up to 200 MPa. However, the application of pressure caused the hydrocarbon chains to tilt from the surface normal. The changes observed in the overall intensity of the Raman spectra on formation of the solid-solid contact can be explained by changes in electric field strengths, but this interpretation cannot be made in the case of the SF spectra. The SF signal arising from the monolayer confined between the two solid surfaces was often much lower than predicted, and this is discussed in terms of structural changes and transfer of monolayer material from one surface to the other. Liquid lubricants were squeezed almost completely out of the solid-solid contact at pressures of 40 MPa. However, the use of a total internal reflection (TIR) excitation geometry in the Raman experiments increased the sensitivity of this technique sufficiently for spectra to be obtained from sub-monolayer amounts of material that had collected in small surface defects, with acquisition times of minutes. (author)

  6. Homogeneous and inhomogeneous broadenings and the Voigt line shapes in the phase-resolved and intensity sum-frequency generation vibrational spectroscopy

    Science.gov (United States)

    Chen, Shun-Li; Fu, Li; Gan, Wei; Wang, Hong-Fei

    2016-01-01

    In this report, we show that the ability to measure the sub-1 cm-1 resolution phase-resolved and intensity high-resolution broadband sum frequency generation vibrational spectra of the -CN stretch vibration of the Langmuir-Blodgett (LB) monolayer of the 4-n-octyl-4'-cyanobiphenyl (8CB) on the z-cut α-quartz surface allows the direct comparison and understanding of the homogeneous and inhomogeneous broadenings in the imaginary and intensity SFG vibrational spectral line shapes in detail. The difference of the full width at half maximum (FWHM) of the imaginary and intensity sum-frequency generation vibrational spectroscopy spectra of the same vibrational mode is the signature of the Voigt line shape and it measures the relative contribution to the overall line shape from the homogeneous and inhomogeneous broadenings in SFG vibrational spectra. From the phase-resolved and intensity spectra, we found that the FWHM of the 2238.00 ± 0.02 cm-1 peak in the phase-resolved imaginary and intensity spectra is 19.2 ± 0.2 cm-1 and 21.6 ± 0.4 cm-1, respectively, for the -CN group of the 8CB LB monolayer on the z-cut α-quartz crystal surface. The FWHM width difference of 2.4 cm-1 agrees quantitatively with a Voigt line shape with a homogeneous broadening half width of Γ = 5.29 ± 0.08 cm-1 and an inhomogeneous standard derivation width Δω = 5.42 ± 0.07 cm-1. These results shed new lights on the understanding and interpretation of the line shapes of both the phase-resolved and the intensity SFG vibrational spectra, as well as other incoherent and coherent spectroscopic techniques in general.

  7. Synchrotron FT-FIR spectroscopy of nitro-derivatives vapors: New spectroscopic signatures of explosive taggants and degradation products

    Science.gov (United States)

    Cuisset, Arnaud; Gruet, Sébastien; Pirali, Olivier; Chamaillé, Thierry; Mouret, Gaël

    2014-11-01

    We report on the first successful rovibrational study of gas phase mononitrotoluene and dinitrotoluene in the TeraHertz/Far-Infrared (THz/FIR) spectral domain. Using the AILES beamline of the synchrotron SOLEIL and a Fourier Transform spectrometer connected to multipass cells, the low-energy vibrational cross-sections of the different isomers of mononitrotoluene have been measured and compared to calculated spectra with the density functional theory including the anharmonic contribution. The active FIR modes of 2,4 and 2,6 dinitrotoluene have been assigned to the vibrational bands measured by Fourier Transform FIR spectroscopy of the gas-phase molecular cloud produced in an evaporating/recondensating system. This study highlights the selectivity of gas phase THz/FIR spectroscopy allowing an unambiguous recognition and discrimination of nitro-aromatic compounds used as explosive taggants.

  8. Ultrafast vibrational spectroscopy (2D-IR) of CO{sub 2} in ionic liquids: Carbon capture from carbon dioxide’s point of view

    Energy Technology Data Exchange (ETDEWEB)

    Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean, E-mail: sgr@pitt.edu [Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260 (United States)

    2015-06-07

    The CO{sub 2}ν{sub 3} asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO{sub 2} is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C{sub 4}C{sub 1}im][X], where [X]{sup −} is the anion from the series hexafluorophosphate (PF{sub 6}{sup −}), tetrafluoroborate (BF{sub 4}{sup −}), bis-(trifluoromethyl)sulfonylimide (Tf{sub 2}N{sup −}), triflate (TfO{sup −}), trifluoroacetate (TFA{sup −}), dicyanamide (DCA{sup −}), and thiocyanate (SCN{sup −})). In the ionic liquids studied, the ν{sub 3} center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO{sub 2} and from CO{sub 2} to the cation. The charge transfer drives geometrical distortion of CO{sub 2}, which in turn changes the ν{sub 3} frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν{sub 2} and ν{sub 3} normal modes of CO{sub 2}. Thermal fluctuations in the ν{sub 2} population stochastically modulate the ν{sub 3} frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO{sub 2}. The results suggest that the picosecond dynamics of CO{sub 2} are gated by local diffusion of anions and cations.

  9. Ultrafast vibrational spectroscopy (2D-IR) of CO2 in ionic liquids: Carbon capture from carbon dioxide's point of view

    Science.gov (United States)

    Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean

    2015-06-01

    The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X]- is the anion from the series hexafluorophosphate (PF 6- ), tetrafluoroborate (BF 4- ), bis-(trifluoromethyl)sulfonylimide (Tf2N-), triflate (TfO-), trifluoroacetate (TFA-), dicyanamide (DCA-), and thiocyanate (SCN-)). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations.

  10. Ultrafast vibrational spectroscopy (2D-IR) of CO2 in ionic liquids: Carbon capture from carbon dioxide’s point of view

    International Nuclear Information System (INIS)

    The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X]− is the anion from the series hexafluorophosphate (PF6−), tetrafluoroborate (BF4−), bis-(trifluoromethyl)sulfonylimide (Tf2N−), triflate (TfO−), trifluoroacetate (TFA−), dicyanamide (DCA−), and thiocyanate (SCN−)). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations

  11. Quantitative determination of molecular structure in multilayered thin films of biaxial and lower symmetry from photon spectroscopies. I. Reflection infrared vibrational spectroscopy

    Science.gov (United States)

    Parikh, Atul N.; Allara, David L.

    1992-01-01

    A semitheoretical formalism based on classical electromagnetic wave theory has been developed for application to the quantitative treatment of reflection spectra from multilayered anisotropic films on both metallic and nonmetallic substrates. Both internal and external reflection experiments as well as transmission can be handled. The theory is valid for all wavelengths and is appropriate, therefore, for such experiments as x-ray reflectivity, uv-visible spectroscopic ellipsometry, and infrared reflection spectroscopy. Further, the theory is applicable to multilayered film structures of variable number of layers, each with any degree of anisotropy up to and including full biaxial symmetry. The reflectivities (and transmissivities) are obtained at each frequency by solving the wave propagation equations using a rigorous 4×4 transfer matrix method developed by Yeh in which the optical functions of each medium are described in the form of second rank (3×3) tensors. In order to obtain optical tensors for materials not readily available in single crystal form, a method has been developed to evaluate tensor elements from the complex scalar optical functions (n̂) obtained from the isotropic material with the limitations that the molecular excitations are well characterized and obey photon-dipole selection rules. This method is intended primarily for infrared vibrational spectroscopy and involves quantitative decomposition of the isotropic imaginary optical function (k) spectrum into a sum of contributions from fundamental modes, the assignment of a direction in molecular coordinates to the transition dipole matrix elements for each mode, the appropriate scaling of each k vector component in surface coordinates according to a selected surface orientation of the molecule to give a diagonal im(n̂) tensor, and the calculation of the real(n̂) spectrum tensor elements by the Kramers-Kronig transformation. Tensors for other surface orientations are generated by an

  12. An approach to global rovibrational analysis based on anharmonic ladder operators: Application to Hydrogen Selenide (H280Se)

    International Nuclear Information System (INIS)

    Graphical abstract: Schematic diagram of a bent triatomic molecule, depicting the atom numbering, and molecular axis system. An algebraic approach to perform global rovibrational analysis is presented. Highlights: ► Novel approach for a global rovibrational analysis of polyatomic molecules spectra. ► One-dimensional vibron model limit combined with rotational degrees of freedom. ► Phase space Hamiltonian written in terms of anharmonic ladder operators. ► Algebraic calculations performed with a symmetry-adapted rovibrational basis. ► Description of the rovibrational spectrum of H2Se in the ground electronic state. - Abstract: An algebraic approach to perform global rovibrational analysis of molecular spectra is presented. The approach combines the one-dimensional limit of the vibron model with rotational degrees of freedom. The model is based on the expression of the phase space Hamiltonian in terms of anharmonic ladder operators and the use of a symmetry-adapted basis set given by the linear combination of products of local vibrational and rotational wavefunctions. As an example we model the rovibrational spectra of a bent triatomic molecule, providing a global analysis for vibrational bands up to polyad 12 and Jmax = 5 of Hydrogen Selenide (H2Se). Satisfactory fits of vibrational and rovibrational energies are obtained. A prediction of 2579 rovibrational energies up to J ⩽ 5 and polyad 12 for the 140 lowest vibrational bands is also obtained. A possible extension of the model to reach spectroscopic quality results in larger molecular systems is also given.

  13. Two-dimensional resonance Raman spectroscopy of oxygen- and water-ligated myoglobins

    Science.gov (United States)

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

    2016-07-01

    Two-dimensional resonance Raman (2DRR) spectroscopy has recently been developed as a tool for studies of structural heterogeneity and photochemical dynamics in condensed phases. In this paper, 2DRR spectroscopy is used to investigate line broadening mechanisms of both oxygen- and water-ligated myoglobins. General signatures of anharmonicity and inhomogeneous line broadening are first established with model calculations to facilitate signal interpretation. It is shown that the present quasi-degenerate version of 2DRR spectroscopy is insensitive to anharmonicity, because signal generation is allowed for harmonic modes. Rather, the key information to be gained from 2DRR spectroscopy pertains to the line broadening mechanisms, which are fairly obvious by inspection of the data. 2DRR signals acquired for both heme protein systems reveal significant heterogeneity in the vibrational modes local to the heme's propionic acid side chains. These side chains are known to interact with solvent, because they protrude from the hydrophobic pocket that encloses the heme. Molecular dynamics simulations suggest that the heterogeneity detected in our 2DRR experiments reflects fluctuations in the geometries of the side chains. Knowledge of such thermal motions will be useful for understanding protein function (e.g., ligand binding) because the side chains are an effective "gateway" for the exchange of thermal energy between the heme and solvent.

  14. Probing anharmonicity of a quantum oscillator in an optomechanical cavity

    Science.gov (United States)

    Latmiral, Ludovico; Armata, Federico; Genoni, Marco G.; Pikovski, Igor; Kim, M. S.

    2016-05-01

    We present a way of measuring with high precision the anharmonicity of a quantum oscillator coupled to an optical field via radiation pressure. Our protocol uses a sequence of pulsed interactions to perform a loop in the phase space of the mechanical oscillator, which is prepared in a thermal state. We show how the optical field acquires a phase depending on the anharmonicity. Remarkably, one only needs small initial cooling of the mechanical motion to probe even small anharmonicities. Finally, by applying tools from quantum estimation theory, we calculate the ultimate bound on the estimation precision posed by quantum mechanics and compare it with the precision obtainable with feasible measurements such as homodyne and heterodyne detection on the cavity field. In particular we demonstrate that homodyne detection is nearly optimal in the limit of a large number of photons of the field and we discuss the estimation precision of small anharmonicities in terms of its signal-to-noise ratio.

  15. Linear delta expansion technique for the solution of anharmonic oscillations

    Indian Academy of Sciences (India)

    P K Bera; J Datta

    2007-01-01

    The linear delta expansion technique has been developed for solving the differential equation of motion for symmetric and asymmetric anharmonic oscillators. We have also demonstrated the sophistication and simplicity of this new perturbation technique.

  16. In situ speciation of the functional groups at mineral/electrolyte interfaces by sum frequency vibrational spectroscopy

    International Nuclear Information System (INIS)

    Full text of publication follows: In order to describe surface reactivity and adsorption/desorption processes on the molecular level, a large number of functional groups has been postulated. In most cases, however, a direct proof for the existence of these species in real aquatic environment is lacking because it is difficult to obtain chemical analytical information in situ under electrolyte with interface selectivity. Here we apply interface selective sum frequency (SF) vibrational spectroscopy to study the (001) and (110) surfaces of sapphire (α-Al2O3) under water between pH 4 and 12. This work is part of an ongoing fundamental study of the sorption mechanism of actinides on single crystals faces of sapphire by various experimental and theoretical techniques. Sapphire is used as a simple model for natural clay minerals and related iron phases. In the O-H stretch region of the infrared spectrum between 2800 and 4000 cm-1, we observe a surprisingly large number of 8 SF bands in total. Two of them are due to the polar ordered water film near the mineral surface which is well known from various aquatic interfaces. The other bands originate from up to 6 different aluminol species or from specifically [1] bound water molecules. The prominent peak of the (001) surface (SF intensity maximum at 3690 cm-1), we attribute to an OH species bridging two [1-4] aluminium atoms. At the (110) surface, the concentration of this species is considerably smaller. Another aluminol species that can be detected at the (001) and the (110) surface (signal maximum near 3450 cm-1) exhibits O-H bonds which are almost parallel to the interface plane. This species is probably the in-plane aluminol group predicted in recent molecular dynamics calculations [4]. SF spectroscopy allows us also to measure the absolute polar orientation of the water molecules adjacent to the mineral surface. The inversion of the molecules polar orientation upon alteration of the pH indicates the point of zero

  17. Adsorption and Vibrational Study of Folic Acid on Gold Nanopillar Structures Using Surface-enhanced Raman Scattering Spectroscopy

    DEFF Research Database (Denmark)

    Castillo, John J.; Rindzevicius, Tomas; Rozo, Ciro E.;

    2015-01-01

    This paper presents a study of adsorption and vibrational features of folic acid, using surface-enhanced Raman scattering (SERS). A gold-capped silicon nanopillar (Au NP) with a height of 600 nm and a width of 120 nm was utilized to study the vibrational features of FA molecules adsorbed on the n...

  18. Application of high-resolution photoelectron spectroscopy: Vibrational resolved C 1s and O 1s spectra of CO adsorbed on Ni(100)

    Energy Technology Data Exchange (ETDEWEB)

    Foehlisch, A.; Nilsson, A.; Martensson, N. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    There are various effects which determine the line shape of a core-level electron spectrum. These are due to the finite life-time of the core hole, inelastic scattering of the outgoing photoelectron, electronic shake-up and shake-off processes and vibrational excitations. For free atoms and molecules the different contributions to the observed line shapes can often be well separated. For solids, surfaces and adsorbates the line shapes are in general much broader and it has in the past been assumed that no separation of the various contributions can be made. In the present report the authors will show that this is indeed not the case. Surprisingly, the vibrational fine structure of CO adsorbed on Ni(100) can be resolved in the C 1s and O 1s electron spectra. This was achieved by the combination of highly monochromatized soft X-rays from B18.0 with a high resolution Scienta 200 mm photoelectron spectrometer. X-ray photoelectron spectroscopy (XPS) with tunable excitation energy yields as a core level spectroscopy atomic and site-specific information. The presented measurements allow for a determination of internuclear distances and potential energy curves in corehole ionized adsorbed molecules. The authors analysis of the c(2x2) phase CO/Ni(100) on {open_quotes}top{close_quotes} yielded a vibrational splitting of 217 +/- 2 meV for C 1s ionization. For O 1s ionization a splitting of 173 +/- 8 meV was found.

  19. Living systems as coherent anharmonic oscillators

    International Nuclear Information System (INIS)

    A model of living systems considered as coherent, time-dependent anharmonic oscillators is presented. It is based on the concept of space-like coherent states minimizing the time-energy uncertainty relation, adapted to the case of biological systems whose growth is described by the Gompertz or West-Brown-Enquist functions. The coherent states of biological growth evolve coherently in space being localized along the classical time trajectory; hence, the growth is predicted to be coherent in space. It is proven that the Gompertz function is a special solution of the space-like Horodecki-Feinberg equation for the time-dependent Morse oscillator in the dissociation state. Its eigenvalue represents the momentum of biological growth, associated with a space-like component whose properties resemble those attributed by vitalists to the life momentum or vital impulse. The physical characteristics of the life energy and momentum and their connection with the concept of zero-point momentum of vacuum are presented.

  20. Systematic Vibration Studies on a Cryogen-Free ^3He/^4He Dilution Refrigerator for X-ray Spectroscopy at Storage Rings

    Science.gov (United States)

    Scholz, P. A.; Kraft-Bermuth, S.; Andrianov, V.

    2016-08-01

    High-precision X-ray spectroscopy of highly charged ions at storage rings provides a sensitive test of quantum electrodynamics in strong Coulomb fields. To increase the precision of such experiments, silicon microcalorimeters have already been applied successfully. To minimize the interruption of beam times due to maintenance, a new cryogen-free ^3He/^4He dilution refrigerator has been designed and is under commissioning. However, in cryogen-free systems microphonic noise due to vibrations contributes considerably to the overall noise and may limit the detector energy resolution. Therefore, we report on systematic vibration studies on a cryogen-free ^3He/^4He dilution refrigerator which is specially adapted for experiments at storage rings.

  1. Investigation of polarized infrared spectra of the hydrogen bond in molecular crystals. New spectral effects in the vibrational spectroscopy of hydrogen bonded systems

    International Nuclear Information System (INIS)

    A review of the experimental as well as of the theoretical studies, performed on the area of the infrared spectroscopy of hydrogen bonded molecular crystals, is given. Discussion of some physical phenomena is presented, responsible for basic spectral effects registered in the infrared spectra, as breaking of vibrational dipole selection rules in the IR spectra, linear dichroic as well as temperature effects, observed in the frequency range of the proton stretching vibrations. Also some newly recognized H/D isotopic effects for hydrogen bonded systems are presented, deduced from a quantitative analysis of the polarized spectra in the IR, namely the so called 'self-organization' effects and the 'long-range' H/D isotope effects. (author)

  2. Systematic Vibration Studies on a Cryogen-Free ^3 He/^4 He Dilution Refrigerator for X-ray Spectroscopy at Storage Rings

    Science.gov (United States)

    Scholz, P. A.; Kraft-Bermuth, S.; Andrianov, V.

    2016-01-01

    High-precision X-ray spectroscopy of highly charged ions at storage rings provides a sensitive test of quantum electrodynamics in strong Coulomb fields. To increase the precision of such experiments, silicon microcalorimeters have already been applied successfully. To minimize the interruption of beam times due to maintenance, a new cryogen-free ^3 He/^4 He dilution refrigerator has been designed and is under commissioning. However, in cryogen-free systems microphonic noise due to vibrations contributes considerably to the overall noise and may limit the detector energy resolution. Therefore, we report on systematic vibration studies on a cryogen-free ^3 He/^4 He dilution refrigerator which is specially adapted for experiments at storage rings.

  3. Mode- and Direction-Dependent Mechanical Energy Dissipation in Single-Crystal Resonators due to Anharmonic Phonon-Phonon Scattering

    Science.gov (United States)

    Iyer, Srikanth S.; Candler, Robert N.

    2016-03-01

    In this work, we determine the intrinsic mechanical energy dissipation limit for single-crystal resonators due to anharmonic phonon-phonon scattering in the Akhiezer (Ω τ ≪1 ) regime. The energy loss is derived using perturbation theory and the linearized Boltzmann transport equation for phonons, and includes the direction- and polarization-dependent mode-Grüneisen parameters in order to capture the strain-induced anharmonicity among phonon branches. This expression reveals the fundamental differences among the internal friction limits for different types of bulk-mode elastic waves. For cubic crystals, 2D-extensional modes have increased dissipation compared to width-extensional modes because the biaxial deformation opposes the natural Poisson contraction of the solid. Additionally, we show that shear-mode vibrations, which preserve volume, have significantly reduced energy loss because dissipative phonon-phonon scattering is restricted to pure-shear phonon branches, indicating that Lamé- or wineglass-mode resonators will have the highest upper limit on mechanical efficiency. Finally, we employ key simplifications to evaluate the quality factor limits for common mode shapes in single-crystal silicon devices, explicitly including the correct effective elastic storage moduli for different vibration modes and crystal orientations. Our expression satisfies the pressing need for a reliable analytical model that can predict the phonon-phonon dissipation limits for modern resonant microelectromechanical systems, where precise manufacturing techniques and accurate finite-element methods can be used to select particular vibrational mode shapes and crystal orientations.

  4. Structural and vibrational properties of Co nanoparticles formed by ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Sprouster, D.J.; Giulian, R.; Araujo, L.L.; Kluth, P.; Johannessen, B.; Cookson, D.J.; Foran, G.J.; Ridgway, M.C. (Aust. Synch.); (ANU)

    2010-02-19

    We report on the structural and vibrational properties of Co nanoparticles formed by ion implantation and thermal annealing in amorphous silica. The evolution of the nanoparticle size, phase, and structural parameters were determined as a function of the formation conditions using transmission electron microscopy, small-angle x-ray scattering, and x-ray absorption spectroscopy. The implantation fluence and annealing temperature governed the spherical nanoparticle size and phase. To determine the latter, x-ray absorption near-edge structure analysis was used to quantify the hexagonal close packed, face-centered cubic and oxide fractions. The structural properties were characterized by extended x-ray absorption fine structure spectroscopy (EXAFS) and finite-size effects were readily apparent. With a decrease in nanoparticle size, an increase in structural disorder and a decrease in both coordination number and bondlength were observed as consistent with the non-negligible surface-area-to-volume ratio characteristic of nanoparticles. The surface tension of Co nanoparticles calculated using a liquid drop model was more than twice that of bulk material. The size-dependent vibrational properties were probed with temperature-dependent EXAFS measurements. Using a correlated anharmonic Einstein model and thermodynamic perturbation theory, Einstein temperatures for both nanoparticles and bulk material were determined. Compared to bulk Co, the mean vibrational frequency of the smallest nanoparticles was reduced as attributed to a greater influence of loosely bonded, undercoordinated surface atoms relative to the effect of capillary pressure generated by surface curvature.

  5. A method for the direct measurement of electronic site populations in a molecular aggregate using two-dimensional electronic-vibrational spectroscopy.

    Science.gov (United States)

    Lewis, Nicholas H C; Dong, Hui; Oliver, Thomas A A; Fleming, Graham R

    2015-09-28

    Two dimensional electronic spectroscopy has proved to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale. PMID:26429003

  6. A method for the direct measurement of electronic site populations in a molecular aggregate using two-dimensional electronic-vibrational spectroscopy

    International Nuclear Information System (INIS)

    Two dimensional electronic spectroscopy has proved to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale

  7. A method for the direct measurement of electronic site populations in a molecular aggregate using two-dimensional electronic-vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Nicholas H. C.; Dong, Hui; Oliver, Thomas A. A.; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720 (United States)

    2015-09-28

    Two dimensional electronic spectroscopy has proved to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale.

  8. Vibrational relaxation and coupling of two OH-stretch oscillators with an intramolecular hydrogen bond.

    Science.gov (United States)

    Lock, A J; Gilijamse, J J; Woutersen, S; Bakker, H J

    2004-02-01

    We studied the vibrational dynamics of the OH-stretch oscillators of an alcohol with two vicinal OH groups using femtosecond midinfrared pump-probe spectroscopy. The absorption spectrum of pinacol (2,3-dimethyl-2,3-butanediol) in CDCl3 shows two OH-stretch peaks belonging to hydrogen bonded and free OH groups. The anharmonicities of the hydrogen-bonded and free OH-stretch vibrations are 180 and 160 cm(-1), respectively. The lifetime T1 of the OH-stretch vibration is found to be 3.5 +/- 0.4 ps for the hydrogen bonded and 7.4 +/- 0.5 ps for the free OH group. We observed sidebands in the transient spectra after excitation of the bonded OH group, which we attribute to a progression in a low-frequency hydrogen-bond mode. The sideband is redshifted 60 cm(-1) with respect to the 0 --> 1 transition. Due to the coupling between the two OH groups and the presence of the sidebands, simultaneous excitation of both OH-stretch vibrations leads to oscillations on the pump-probe signal with frequencies of 40 and 60 cm(-1). PMID:15268374

  9. Vibrational relaxation and coupling of two OH-stretch oscillators with an intramolecular hydrogen bond

    Science.gov (United States)

    Lock, A. J.; Gilijamse, J. J.; Woutersen, S.; Bakker, H. J.

    2004-02-01

    We studied the vibrational dynamics of the OH-stretch oscillators of an alcohol with two vicinal OH groups using femtosecond midinfrared pump-probe spectroscopy. The absorption spectrum of pinacol (2,3-dimethyl-2,3-butanediol) in CDCl3 shows two OH-stretch peaks belonging to hydrogen bonded and free OH groups. The anharmonicities of the hydrogen-bonded and free OH-stretch vibrations are 180 and 160 cm-1, respectively. The lifetime T1 of the OH-stretch vibration is found to be 3.5±0.4 ps for the hydrogen bonded and 7.4±0.5 ps for the free OH group. We observed sidebands in the transient spectra after excitation of the bonded OH group, which we attribute to a progression in a low-frequency hydrogen-bond mode. The sideband is redshifted 60 cm-1 with respect to the 0→1 transition. Due to the coupling between the two OH groups and the presence of the sidebands, simultaneous excitation of both OH-stretch vibrations leads to oscillations on the pump-probe signal with frequencies of 40 and 60 cm-1.

  10. High-resolution synchrotron infrared spectroscopy of acrolein: The vibrational levels between 850 and 1020 cm-1

    Science.gov (United States)

    McKellar, A. R. W.; Billinghurst, B. E.; Xu, Li-Hong; Lees, R. M.

    2015-11-01

    Using spectra obtained at the Canadian Light Source synchrotron radiation facility, a previously unobserved out-of-plane vibration of trans-acrolein (propenal) is reliably assigned for the first time. Its origin is at 1002.01 cm-1, which is about 20 cm-1 higher than usually quoted in the past. This mode is thus labelled as v14, leaving the label v15 for the known vibration at 992.66 cm-1. Weak combination bands 171182 ← 182, 171131 ← 131, 121182 ← 181, and 171182 ← 181 are studied for the first time, and assignments in the known v11, v16, and v15 fundamental bands are also extended. The seven excited vibrations involved in these bands are analyzed, together with five more unobserved vibrations in the same region (850-1020 cm-1), in a large 12-state simultaneous fit which accounts for most of the many observed perturbations in the spectra.

  11. Detailed structural study of β-artemether: Density functional theory (DFT) calculations of Infrared, Raman spectroscopy, and vibrational circular dichroism

    Science.gov (United States)

    Wang, Zhiqiang; Chen, Jianchao; Li, Linwei; Zhou, Zhixu; Geng, Yiding; Sun, Tiemin

    2015-10-01

    In this study, the experimental and theoretical studies on the structure of β-artemether are presented. The optimized molecular structure, Mulliken atomic charges, vibrational spectra (IR, Raman and vibrational circular dichroism), and molecular electrostatic potential have been calculated by density functional theory (DFT) using B3LYP method with the 6-311++G (2d, p) basis set. Reliable vibrational assignments for Artemether have been made on the basis of potential energy distribution (PED). The vibrational circular dichroism (VCD) has been explored by ab initio calculations, and then was used to compare with the experimental VCD. The consistence between them confirmed the absolute configuration of Artemether. In addition, HOMO-LUMO of the title compound as well as thermo-dynamical parameters has illustrated the stability of β-artemether.

  12. Determination of populations of vibrational levels of carbon dioxide molecules in gas dynamic lasers by ir spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bakhir, L.P.; Overchenko, Yu.V.

    1979-01-01

    The absorption and emission spectra of some vibrational and rotational transitions of the carbon dioxide molecule in the range of 4.3, 10, and 15 ..mu.. m are analyzed under non-equilibrium conditions at the outlet of a gas-dynamic laser; and an examination is made of the possibility of their use to determine the populations of lower vibrational levels of carbon dioxide at different degrees of expansion. In view of the sharp distinction of relaxation rates for various degrees of freedom in a gas-dynamic laser, the vibrational temperatures of various levels of CO/sub 2/ may differ significantly from each other, as well as from rotational and translational temperatures. In describing populations in terms of the length of a jet, vibrational and rotational energies are separated and population temperatures equal to mode temperatures are assumed for purely symmetric deformation and asymmetric vibrations. A method for determining the absolute populations of low vibrational levels of the carbon dioxide molecule is developed according to measurements of absorption and brightness of a non-equilibrium jet near given frequencies.

  13. Quantum versus semiclassical description of selftrapping: anharmonic effects

    International Nuclear Information System (INIS)

    Selftrapping has been traditionally studied on the assumption that quasiparticles interact with harmonic phonons and that this interaction is linear in the displacement of the phonon. To complement recent semiclassical studies of anharmonicity and nonlinearity in this context, we present below a fully quantum mechanical analysis of a two-site system, where the oscillator is described by a tunably anharmonic potential, with a square well with infinite walls and the harmonic potential as its extreme limits, and wherein the interaction is nonlinear in the oscillator displacement. We find that even highly anharmonic polarons behave similar to their harmonic counterparts in that selftrapping is preserved for long times in the limit of strong coupling, and that the polaronic tunneling time scale depends exponentially on the polaron binding energy. Further, in agreement with earlier results related to harmonic polarons, the semiclassical approximation agrees with the full quantum result in the massive oscillator limit of small oscillator frequency and strong quasiparticle-oscillator coupling. (author)

  14. Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, Hal

    1968-01-01

    This booklet discusses spectroscopy, the study of absorption of radiation by matter, including X-ray, gamma-ray, microwave, mass spectroscopy, as well as others. Spectroscopy has produced more fundamental information to the study of the detailed structure of matter than any other tools.

  15. Catalyzed hydrogenation of nitrogen and ethylene on metal (Fe, Pt) single crystal surfaces and effects of coadsorption: A sum frequency generation vibrational spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Westerberg, Staffan Per Gustav

    2004-12-15

    High-pressure catalytic reactions and associated processes, such as adsorption have been studied on a molecular level on single crystal surfaces. Sum Frequency Generation (SFG) vibrational spectroscopy together with Auger Electron Spectroscopy (AES), Temperature Programmed Desorption (TPD) and Gas Chromatography (GC) were used to investigate the nature of species on catalytic surfaces and to measure the catalytic reaction rates. Special attention has been directed at studying high-pressure reactions and in particular, ammonia synthesis in order to identify reaction intermediates and the influence of adsorbates on the surface during reaction conditions. The adsorption of gases N{sub 2}, H{sub 2}, O{sub 2} and NH{sub 3} that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by sum frequency generation vibrational spectroscopy using an integrated Ultra-High Vacuum (UHV)/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH{sub 2} ({approx}3325 cm{sup -1}) and NH ({approx}3235 cm{sup -1}) under high pressure of ammonia (200 Torr) on the clean Fe(111) surface. Addition of 0.5 Torr of oxygen to 200 Torr of ammonia does not significantly change the bonding of dissociation intermediates to the surface. However, it leads to a phase change of nearly 180{sup o} between the resonant and non-resonant second order non-linear susceptibility of the surface, demonstrated by the reversal of the SFG spectral features. Heating the surface in the presence of 200 Torr ammonia and 0.5 Torr oxygen reduces the oxygen coverage, which can be seen from the SFG spectra as another relative phase change of 180{sup o}. The reduction of the oxide is also supported by Auger electron spectroscopy. The result suggests that the phase change of the spectral features could serve as a sensitive indicator of the chemical environment of the adsorbates.

  16. Vibrational Heat Transport in Molecular Junctions

    Science.gov (United States)

    Segal, Dvira; Agarwalla, Bijay Kumar

    2016-05-01

    We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules.

  17. Vibrational Heat Transport in Molecular Junctions.

    Science.gov (United States)

    Segal, Dvira; Agarwalla, Bijay Kumar

    2016-05-27

    We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules. PMID:27215814

  18. Nonlinear effects in infrared action spectroscopy of silicon and vanadium oxide clusters: experiment and kinetic modeling.

    Science.gov (United States)

    Calvo, Florent; Li, Yejun; Kiawi, Denis M; Bakker, Joost M; Parneix, Pascal; Janssens, Ewald

    2015-10-21

    For structural assignment of gas phase compounds, infrared action spectra are usually compared to computed linear absorption spectra. However, action spectroscopy is highly nonlinear owing to the necessary transfer of the excitation energy and its subsequent redistribution leading to statistical ionization or dissociation. Here, we examine by joint experiment and dedicated modeling how such nonlinear effects affect the spectroscopic features in the case of selected inorganic clusters. Vibrational spectra of neutral silicon clusters are recorded by tunable IR-UV two-color ionization while IR spectra for cationic vanadium oxide clusters are obtained by IR multiphoton absorption followed by dissociation of the bare cluster or of its complex with Xe. Our kinetic modeling accounts for vibrational anharmonicities, for the laser interaction through photon absorption and stimulated emission rates, as well as for the relevant ionization or dissociation rates, all based on input parameters from quantum chemical calculations. Comparison of the measured and calculated spectra indicates an overall agreement as far as trends are concerned, except for the photodissociation of the V3O7(+)-Xe messenger complex, for which anharmonicities are too large and poorly captured by the perturbative anharmonic model. In all systems studied, nonlinear effects are essentially manifested by variations in the intensities as well as spectral broadenings. Differences in some band positions originate from inaccuracies of the quantum chemical data rather than specific nonlinear effects. The simulations further yield information on the average number of photons absorbed, which is otherwise unaccessible information: several to several tens of photons need to be absorbed to observe a band through dissociation, while three to five photons can be sufficient for detection of a band via IR-UV ionization. PMID:26208251

  19. Spectroscopy

    CERN Document Server

    Walker, S

    1976-01-01

    The three volumes of Spectroscopy constitute the one comprehensive text available on the principles, practice and applications of spectroscopy. By giving full accounts of those spectroscopic techniques only recently introduced into student courses - such as Mössbauer spectroscopy and photoelectron spectroscopy - in addition to those techniques long recognised as being essential in chemistry teaching - sucha as e.s.r. and infrared spectroscopy - the book caters for the complete requirements of undergraduate students and at the same time provides a sound introduction to special topics for graduate students.

  20. Vibrational study of the structural phase transition in bis(pyrrolidinium)-chloride-hexachloroantimonate(V) by infrared spectroscopy

    Science.gov (United States)

    Bednarska-Bolek, B.; Jakubas, R.; Bator, G.; Baran, J.

    2002-09-01

    Infrared spectra of bis(pirrolidinium)-chloride-hexachloroantimonate(V) {(C 4H 8NH 2+) 2SbCl 6-·Cl -} in the region of the internal vibrations of the pyrrolidinium cations (3500-400 cm -1) around the phase transition at T c=134 K are presented and discussed. A detailed analysis has been performed for the bands assigned to the stretching and deformation vibrations of the C 4N ring as well as the NH 2+ and CH 2 groups of the cation. It has been suggested that the mechanism of the phase transition is connected with a change in the dynamical state of the pyrrolidinium cation.

  1. Diagrammatic Vibrational Coupled-Cluster

    Science.gov (United States)

    Faucheaux, Jacob A.; Hirata, So

    2015-06-01

    A diagrammatic vibrational coupled-cluster method for calculation of zero-point energies and an equation-of-motion coupled-cluster method for calculation of anharmonic vibrational frequencies are developed. The methods, which we refer to as XVCC and EOM-XVCC respectively, rely on the size-extensive vibrational self-consistient field (XVSCF) method for reference wave functions. The methods retain the efficiency advantages of XVSCF making them suitable for applications to large molecules and solids, while they are numerically shown to accurately predict zero-point energies and frequencies of small molecules as well. In particular, EOM-XVCC is shown to perform well for modes which undergo Fermi resonance where traditional perturbative methods fail. Rules for the systematic generation and interpretation of the XVCC and EOM-XVCC diagrams to any order are presented.

  2. Studies of Heterogeneously Catalyzed Liquid-Phase Alcohol Oxidation on Platinum bySum-frequency Generation Vibrational Spectroscopy and Reaction Rate Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Christopher [Univ. of California, Berkeley, CA (United States)

    2014-05-15

    Compared to many branches of chemistry, the molecular level study of catalytically active surfaces is young. Only with the invention of ultrahigh vacuum technology in the past half century has it been possible to carry out experiments that yield useful molecular information about the reactive occurrences at a surface. The reason is two-fold: low pressure is necessary to keep a surface clean for an amount of time long enough to perform an experiment, and most atomic scale techniques that are surface speci c (x-ray photoelectron spectroscopy, electron energy loss spectroscopy, Auger electron spectroscopy, etc.) cannot be used at ambient pressures, because electrons, which act as chemical probes in these techniques, are easily scattered by molecules. Sum-frequency generation (SFG) vibrational spectroscopy is one technique that can provide molecular level information from the surface without the necessity for high vacuum. Since the advent of SFG as a surface spectroscopic tool it has proved its worth in the studies of surface catalyzed reactions in the gas phase, with numerous reactions in the gas phase having been investigated on a multitude of surfaces. However, in situ SFG characterization of catalysis at the solid-liquid interface has yet to be thoroughly pursued despite the broad interest in the use of heterogeneous catalysts in the liquid phase as replacements for homogeneous counterparts. This work describes an attempt to move in that direction, applying SFG to study the solid-liquid interface under conditions of catalytic alcohol oxidation on platinum.

  3. Differences in the Vibrational Dynamics of H2O and D2O: Observation of Symmetric and Antisymmetric Stretching Vibrations in Heavy Water.

    Science.gov (United States)

    De Marco, Luigi; Carpenter, William; Liu, Hanchao; Biswas, Rajib; Bowman, Joel M; Tokmakoff, Andrei

    2016-05-19

    Water's ability to donate and accept hydrogen bonds leads to unique and complex collective dynamical phenomena associated with its hydrogen-bond network. It is appreciated that the vibrations governing liquid water's molecular dynamics are delocalized, with nuclear motion evolving coherently over the span of several molecules. Using two-dimensional infrared spectroscopy, we have found that the nuclear motions of heavy water, D2O, are qualitatively different than those of H2O. The nonlinear spectrum of liquid D2O reveals distinct O-D stretching resonances, in contrast to H2O. Furthermore, our data indicates that condensed-phase O-D vibrations have a different character than those in the gas phase, which we understand in terms of weakly delocalized symmetric and antisymmetric stretching vibrations. This difference in molecular dynamics reflects the shift in the balance between intra- and intermolecular couplings upon deuteration, an effect which can be understood in terms of the anharmonicity of the nuclear potential energy surface. PMID:27115316

  4. Structure Sensitivity in Pt Nanoparticle Catalysts for Hydrogenation of 1,3-Butadiene: In Situ Study of Reaction Intermediates Using SFG Vibrational Spectroscopy

    KAUST Repository

    Michalak, William D.

    2013-01-31

    The product selectivity during 1,3-butadiene hydrogenation on monodisperse, colloidally synthesized, Pt nanoparticles was studied under reaction conditions with kinetic measurements and in situ sum frequency generation (SFG) vibrational spectroscopy. SFG was performed with the capping ligands intact in order to maintain nanoparticle size by reduced sintering. Four products are formed at 75 C: 1-butene, cis-2-butene, trans-2-butene, and n-butane. Ensembles of Pt nanoparticles with average diameters of 0.9 and 1.8 nm exhibit a ∼30% and ∼20% increase in the full hydrogenation products, respectively, as compared to Pt nanoparticles with average diameters of 4.6 and 6.7 nm. Methyl and methylene vibrational stretches of reaction intermediates observed under working conditions using SFG were used to correlate the stable reaction intermediates with the product distribution. Kinetic and SFG results correlate with previous DFT predictions for two parallel reaction pathways of 1,3-butadiene hydrogenation. Hydrogenation of 1,3-butadiene can initiate with H-addition at internal or terminal carbons leading to the formation of 1-buten-4-yl radical (metallocycle) and 2-buten-1-yl radical intermediates, respectively. Small (0.9 and 1.8 nm) nanoparticles exhibited vibrational resonances originating from both intermediates, while the large (4.6 and 6.7 nm) particles exhibited vibrational resonances originating predominately from the 2-buten-1-yl radical. This suggests each reaction pathway competes for partial and full hydrogenation and the nanoparticle size affects the kinetic preference for the two pathways. The reaction pathway through the metallocycle intermediate on the small nanoparticles is likely due to the presence of low-coordinated sites. © 2012 American Chemical Society.

  5. Communication: He-tagged vibrational spectra of the SarGlyH+ and H+(H2O)2,3 ions: Quantifying tag effects in cryogenic ion vibrational predissociation (CIVP) spectroscopy

    International Nuclear Information System (INIS)

    To assess the degree to which more perturbative, but widely used “tag” species (Ar, H2, Ne) affect the intrinsic band patterns of the isolated ions, we describe the extension of mass-selective, cryogenic ion vibrational spectroscopy to the very weakly interacting helium complexes of three archetypal ions: the dipeptide SarGlyH+ and the small protonated water clusters: H+(H2O)2,3, including the H5O2+ “Zundel” ion. He adducts were generated in a 4.5 K octopole ion trap interfaced to a double-focusing, tandem time-of-flight photofragmentation mass spectrometer to record mass-selected vibrational predissociation spectra. The H2 tag-induced shift (relative to that by He) on the tag-bound NH stretch of the SarGlyH+ spectrum is quite small (12 cm−1), while the effect on the floppy H5O2+ ion is more dramatic (125 cm−1) in going from Ar (or H2) to Ne. The shifts from Ne to He, on the other hand, while quantitatively significant (maximum of 10 cm−1), display the same basic H5O2+ band structure, indicating that the He-tagged H5O2+ spectrum accurately represents the delocalized nature of the vibrational zero-point level. Interestingly, the He-tagged spectrum of H+(H2O)3 reveals the location of the non-bonded OH group on the central H3O+ ion to fall between the collective non-bonded OH stretches on the flanking water molecules in a position typically associated with a neutral OH group

  6. Terahertz spectroscopy and solid-state density functional theory calculation of anthracene: Effect of dispersion force on the vibrational modes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Feng; Tominaga, Keisuke, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-0013 (Japan); Hayashi, Michitoshi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp; Wang, Houng-Wei [Center for Condensed Matter Sciences, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China); Kambara, Ohki; Sasaki, Tetsuo [Research Institute of Electronics, Shizuoka University, 3-5-1 Jyohoku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Nishizawa, Jun-ichi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Jun-ichi Nishizawa Memorial Research Center, Tohoku University, 519-1176 Aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)

    2014-05-07

    The phonon modes of molecular crystals in the terahertz frequency region often feature delicately coupled inter- and intra-molecular vibrations. Recent advances in density functional theory such as DFT-D{sup *} have enabled accurate frequency calculation. However, the nature of normal modes has not been quantitatively discussed against experimental criteria such as isotope shift (IS) and correlation field splitting (CFS). Here, we report an analytical mode-decoupling method that allows for the decomposition of a normal mode of interest into intermolecular translation, libration, and intramolecular vibrational motions. We show an application of this method using the crystalline anthracene system as an example. The relationship between the experimentally obtained IS and the IS obtained by PBE-D{sup *} simulation indicates that two distinctive regions exist. Region I is associated with a pure intermolecular translation, whereas region II features coupled intramolecular vibrations that are further coupled by a weak intermolecular translation. We find that the PBE-D{sup *} data show excellent agreement with the experimental data in terms of IS and CFS in region II; however, PBE-D{sup *} produces significant deviations in IS in region I where strong coupling between inter- and intra-molecular vibrations contributes to normal modes. The result of this analysis is expected to facilitate future improvement of DFT-D{sup *}.

  7. Vibrational circular dichroism spectroscopy as a tool to study DNA structural changes: Experimental and computional approaches (Lecture)

    Czech Academy of Sciences Publication Activity Database

    Andrushchenko, Valery; Wieser, H.; Bouř, Petr

    Kharkiv : Institute of Radiophysics and Electronics NASU, 2007, 28/145. [Kharkiv Young Scientist Conference on Radiophysics and Electronics /7./. Kharkiv (UA), 12.12.2007-14.12.2007] Institutional research plan: CEZ:AV0Z40550506 Keywords : vibrational circular dichroism * DNA * RNA Subject RIV: CF - Physical ; Theoretical Chemistry www.ire.kharkov.ua/ysc

  8. Oriented single-crystal nuclear resonance vibrational spectroscopy of [Fe(TPP)(MI)(NO)] : quantitative sssessment of the trans effect of NO.

    Energy Technology Data Exchange (ETDEWEB)

    Lehnert, N.; Sage, J. T.; Silvernail, N.; Scheidt, W. R.; Alp, E. E.; Sturhahn, W.; Zhao, J. (X-Ray Science Division); (Univ. of Michigan); (Northeastern Univ.); (Univ. of Notre Dame)

    2010-01-01

    This paper presents oriented single-crystal Nuclear Resonance Vibrational Spectroscopy (NRVS) data for the six-coordinate (6C) ferrous heme-nitrosyl model complex [{sup 57}Fe(TPP)(MI)(NO)] (1; TPP{sup 2-} = tetraphenylporphyrin dianion; MI = 1-methylimidazole). The availability of these data enables for the first time the detailed simulation of the complete NRVS data, including the porphyrin-based vibrations, of a 6C ferrous heme-nitrosyl, using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Importantly, the Fe-NO stretch is split by interaction with a porphyrin-based vibration into two features, observed at 437 and 472 cm{sup -1}. The 437 cm{sup -1} feature is strongly out-of-plane (oop) polarized and shows a {sup 15}N{sup 18}O isotope shift of 8 cm{sup -1} and is therefore assigned to v(Fe-NO). The admixture of Fe-N-O bending character is small. Main contributions to the Fe-N-O bend are observed in the 520-580 cm{sup -1} region, distributed over a number of in-plane (ip) polarized porphyrin-based vibrations. The main component, assigned to {delta}{sub ip}(Fe-N-O), is identified with the feature at 563 cm{sup -1}. The Fe-N-O bend also shows strong mixing with the Fe-NO stretching internal coordinate, as evidenced by the oop NRVS intensity in the 520-580 cm{sup -1} region. Very accurate normal mode descriptions of ?(Fe-NO) and {delta}{sub ip}(Fe-N-O) have been obtained in this study. These results contradict previous interpretations of the vibrational spectra of 6C ferrous heme-nitrosyls where the higher energy feature at {approx}550 cm{sup -1} had usually been associated with v(Fe-NO). Furthermore, these results provide key insight into NO binding to ferrous heme active sites in globins and other heme proteins, in particular with respect to (a) the effect of hydrogen bonding to the coordinated NO and (b) changes in heme dynamics upon NO coordination. [Fe(TPP)(MI)(NO)] constitutes an excellent model system for ferrous NO adducts of myoglobin

  9. Oriented single-crystal nuclear resonance vibrational spectroscopy of [Fe(TPP)(MI)(NO)]: quantitative assessment of the trans effect of NO.

    Science.gov (United States)

    Lehnert, Nicolai; Sage, J Timothy; Silvernail, Nathan; Scheidt, W Robert; Alp, E Ercan; Sturhahn, Wolfgang; Zhao, Jiyong

    2010-08-01

    This paper presents oriented single-crystal Nuclear Resonance Vibrational Spectroscopy (NRVS) data for the six-coordinate (6C) ferrous heme-nitrosyl model complex [(57)Fe(TPP)(MI)(NO)] (1; TPP(2-) = tetraphenylporphyrin dianion; MI = 1-methylimidazole). The availability of these data enables for the first time the detailed simulation of the complete NRVS data, including the porphyrin-based vibrations, of a 6C ferrous heme-nitrosyl, using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Importantly, the Fe-NO stretch is split by interaction with a porphyrin-based vibration into two features, observed at 437 and 472 cm(-1). The 437 cm(-1) feature is strongly out-of-plane (oop) polarized and shows a (15)N(18)O isotope shift of 8 cm(-1) and is therefore assigned to nu(Fe-NO). The admixture of Fe-N-O bending character is small. Main contributions to the Fe-N-O bend are observed in the 520-580 cm(-1) region, distributed over a number of in-plane (ip) polarized porphyrin-based vibrations. The main component, assigned to delta(ip)(Fe-N-O), is identified with the feature at 563 cm(-1). The Fe-N-O bend also shows strong mixing with the Fe-NO stretching internal coordinate, as evidenced by the oop NRVS intensity in the 520-580 cm(-1) region. Very accurate normal mode descriptions of nu(Fe-NO) and delta(ip)(Fe-N-O) have been obtained in this study. These results contradict previous interpretations of the vibrational spectra of 6C ferrous heme-nitrosyls where the higher energy feature at approximately 550 cm(-1) had usually been associated with nu(Fe-NO). Furthermore, these results provide key insight into NO binding to ferrous heme active sites in globins and other heme proteins, in particular with respect to (a) the effect of hydrogen bonding to the coordinated NO and (b) changes in heme dynamics upon NO coordination. [Fe(TPP)(MI)(NO)] constitutes an excellent model system for ferrous NO adducts of myoglobin (Mb) mutants where the distal histidine (His64

  10. Methyl group dynamics and the onset of anharmonicity in myoglobin

    International Nuclear Information System (INIS)

    The role of methyl groups in the onset of low-temperature anharmonic dynamics in a crystalline protein at low temperature is investigated using atomistic molecular dynamics (MD) simulation. Anharmonicity appears at 150 ∼ K, far below the much-studied solvent-activated dynamical transition at ∼ 220 K. A significant fraction of methyl groups exhibit nanosecond time scale rotational jump diffusion at 150 K. The splitting and shift in peak position of both the librational band (around 100 cm-1) and the torsional band (around 270?300 cm-1) also differ significantly among methyl groups, depending on the local environment. The simulation results provide no evidence for a correlation between methyl dynamics and solvent exposure, consistent with the hydration-independence of the low-temperature anharmonic dynamics observed in neutron scattering experiments. The calculated proton mean-square fluctuation and methyl NMR order parameters show a systematic nonlinear dependence on the rotational barrier which can be described using model functions. The methyl groups that exhibit many rotational excitations are located near xenon cavities, suggesting that cavities in proteins act as activation centers of anharmonic dynamics. The dynamic heterogeneity and the environmental sensitivity of motional parameters and low-frequency spectral bands of CH3 groups found here suggest that methyl dynamics may be used as a probe to investigate the relation between low-energy structural fluctuations and packing defects in proteins

  11. Rotational spectroscopy of pyridazine and its isotopologs from 235-360 GHz: equilibrium structure and vibrational satellites.

    Science.gov (United States)

    Esselman, Brian J; Amberger, Brent K; Shutter, Joshua D; Daane, Mitchell A; Stanton, John F; Woods, R Claude; McMahon, Robert J

    2013-12-14

    The rotational spectrum of pyridazine (o-C4H4N2), the ortho disubstituted nitrogen analog of benzene, has been measured and analyzed in the gas phase. For the ground vibrational state of the normal isotopolog, over 2000 individual rotational transitions have been identified between 238 and 360 GHz and have been fit to 13 parameters of a 6th-order centrifugal distortion Hamiltonian. All transitions in this frequency region can now be predicted from this model to near experimental accuracy, i.e., well enough for the purpose of any future radio-astronomical search for this species. Three isotopologs, [3-(13)C]-C4H4N2, [4-(13)C]-C4H4N2, and [1-(15)N]-C4H4N2, have been detected in natural abundance, and several hundred lines have been measured for each of these species and fit to 6th-order Hamiltonians. Ten additional isotopologs were synthesized with enhanced deuterium substitution and analyzed to allow for a complete structure determination. The equilibrium structure (Re) of pyridazine was obtained by correcting the experimental rotational constants for the effects of vibration-rotation coupling using interaction constants predicted from CCSD(T) calculations with an ANO0 basis set and further correcting for the effect of electron mass. The final Re structural parameters are determined with excellent accuracy, as evidenced by their ability to predict 28 independent moments of inertia (Ia and Ib for 14 isotopologs) very well from 9 structural parameters. The rotational spectra of the six lowest-energy fundamental vibrational satellites of the main isotopolog have been detected. The rotational spectra of the five lowest-energy vibrational satellites have been assigned and fit to yield accurate rotational and distortion constants, while the fit and assignment for the sixth is less complete. The resultant vibration-rotation interaction (α) constants are found to be in excellent agreement with ones predicted from coupled-cluster calculations, which proved to be the key

  12. Resonance-enhanced multiphoton ionization (REMPI) spectroscopy of bromobenzene and its perdeuterated isotopologue: Assignment of the vibrations of the S(0), S(1), and D(0)(+) states of bromobenzene and the S(0) and D(0)(+) states of iodobenzene.

    Science.gov (United States)

    Andrejeva, Anna; Tuttle, William D; Harris, Joe P; Wright, Timothy G

    2015-12-28

    We report vibrationally resolved spectra of the S1←S0 transition of bromobenzene using resonance-enhanced multiphoton ionization spectroscopy. We study bromobenzene-h5 as well as its perdeuterated isotopologue, bromobenzene-d5. The form of the vibrational modes between the isotopologues and also between the S0 and S1 electronic states is discussed for each species, allowing assignment of the bands to be achieved and the activity between states and isotopologues to be established. Vibrational bands are assigned utilizing quantum chemical calculations, previous experimental results, and isotopic shifts. Previous work and assignments of the S1 spectra are discussed. Additionally, the vibrations in the ground state cation, D0 (+), are considered, since these have also been used by previous workers in assigning the excited neutral state spectra. We also examine the vibrations of iodobenzene in the S0 and D0 (+) states and comment on the previous assignments of these. In summary, we have been able to assign the corresponding vibrations across the whole monohalobenzene series of molecules, in the S0, S1, and D0 (+) states, gaining insight into vibrational activity and vibrational couplings. PMID:26723684

  13. Resonance-enhanced multiphoton ionization (REMPI) spectroscopy of bromobenzene and its perdeuterated isotopologue: Assignment of the vibrations of the S0, S1, and D0+ states of bromobenzene and the S0 and D0+ states of iodobenzene

    International Nuclear Information System (INIS)

    We report vibrationally resolved spectra of the S1←S0 transition of bromobenzene using resonance-enhanced multiphoton ionization spectroscopy. We study bromobenzene-h5 as well as its perdeuterated isotopologue, bromobenzene-d5. The form of the vibrational modes between the isotopologues and also between the S0 and S1 electronic states is discussed for each species, allowing assignment of the bands to be achieved and the activity between states and isotopologues to be established. Vibrational bands are assigned utilizing quantum chemical calculations, previous experimental results, and isotopic shifts. Previous work and assignments of the S1 spectra are discussed. Additionally, the vibrations in the ground state cation, D0+, are considered, since these have also been used by previous workers in assigning the excited neutral state spectra. We also examine the vibrations of iodobenzene in the S0 and D0+ states and comment on the previous assignments of these. In summary, we have been able to assign the corresponding vibrations across the whole monohalobenzene series of molecules, in the S0, S1, and D0+ states, gaining insight into vibrational activity and vibrational couplings

  14. Insight into structural phase transitions from the decoupled anharmonic mode approximation.

    Science.gov (United States)

    Adams, Donat J; Passerone, Daniele

    2016-08-01

    We develop a formalism (decoupled anharmonic mode approximation, DAMA) that allows calculation of the vibrational free energy using density functional theory even for materials which exhibit negative curvature of the potential energy surface with respect to atomic displacements. We investigate vibrational modes beyond the harmonic approximation and approximate the potential energy surface with the superposition of the accurate potential along each normal mode. We show that the free energy can stabilize crystal structures at finite temperatures which appear dynamically unstable at T  =  0. The DAMA formalism is computationally fast because it avoids statistical sampling through molecular dynamics calculations, and is in principle completely ab initio. It is free of statistical uncertainties and independent of model parameters, but can give insight into the mechanism of a structural phase transition. We apply the formalism to the perovskite cryolite, and investigate the temperature-driven phase transition from the P21/n to the Immm space group. We calculate a phase transition temperature between 710 and 950 K, in fair agreement with the experimental value of 885 K. This can be related to the underestimation of the interaction of the vibrational states. We also calculate the main axes of the thermal ellipsoid and can explain the experimentally observed increase of its volume for the fluorine by 200-300% throughout the phase transition. Our calculations suggest the appearance of tunneling states in the high temperature phase. The convergence of the vibrational DOS and of the critical temperature with respect of reciprocal space sampling is investigated using the polarizable-ion model. PMID:27269514

  15. Insight into structural phase transitions from the decoupled anharmonic mode approximation

    Science.gov (United States)

    Adams, Donat J.; Passerone, Daniele

    2016-08-01

    We develop a formalism (decoupled anharmonic mode approximation, DAMA) that allows calculation of the vibrational free energy using density functional theory even for materials which exhibit negative curvature of the potential energy surface with respect to atomic displacements. We investigate vibrational modes beyond the harmonic approximation and approximate the potential energy surface with the superposition of the accurate potential along each normal mode. We show that the free energy can stabilize crystal structures at finite temperatures which appear dynamically unstable at T  =  0. The DAMA formalism is computationally fast because it avoids statistical sampling through molecular dynamics calculations, and is in principle completely ab initio. It is free of statistical uncertainties and independent of model parameters, but can give insight into the mechanism of a structural phase transition. We apply the formalism to the perovskite cryolite, and investigate the temperature-driven phase transition from the P21/n to the Immm space group. We calculate a phase transition temperature between 710 and 950 K, in fair agreement with the experimental value of 885 K. This can be related to the underestimation of the interaction of the vibrational states. We also calculate the main axes of the thermal ellipsoid and can explain the experimentally observed increase of its volume for the fluorine by 200–300% throughout the phase transition. Our calculations suggest the appearance of tunneling states in the high temperature phase. The convergence of the vibrational DOS and of the critical temperature with respect of reciprocal space sampling is investigated using the polarizable-ion model.

  16. Role of energy exchange in vibrational dephasing processes in liquids and solids

    International Nuclear Information System (INIS)

    Three theories which claim relevance to the dephasing of molecular vibrations in condensed phase matter are presented. All of these theories predict (in certain limiting cases) that the widths and shifts of molecular vibrations will obey an Arrhenius temperature dependence. The basic tenets of the theories are detailed so that the differences between them may be used in an experiment to distinguish between them. One model, based on intermolecular energy exchange of low-frequency modes, results in dephasing the high-frequency modes when anharmonic coupling is present. A computer analysis of temperature dependent experimental lineshapes can result in the extraction of various parameters such as the anharmonic shifts and the exchange rates. It is shown that, in order to properly assess the relative validity of the three models, other evidence must be obtained such as the spectral parameters of the low-frequency modes, the combination bands, and the isotopic dilution behavior. This evidence is presented for d14-durene (perdeutero-1,2,4,5-tetramethylbenzene) and compared to previous data obtained on pure h14-durene. An extension of the (HSC) intermolecular energy exchange model which allows for the possibility of partial delocalization of the low-frequency modes gives an adequate description of the experimental evidence. Isotopic dilution experiments, in particular, have resulted in a detailed picture of the energy transfer dynamics of the low-frequency modes. A section in which some spontaneous Raman spectra support a model of inhomogeneous broadening in liquids based on results of picosecond stimulated Raman spectroscopy is presented. The model is that a distribution of environmental sites is created by a distribution in the local density and thus creates inhomogeneous broadening

  17. Anharmonic effects in the optical and acoustic bending modes of graphene

    Science.gov (United States)

    Ramírez, R.; Chacón, E.; Herrero, C. P.

    2016-06-01

    The out-of-plane fluctuations of carbon atoms in a graphene sheet have been studied by means of classical molecular dynamic simulations with an empirical force field as a function of temperature. The Fourier analysis of the out-of-plane fluctuations often applied to characterize the acoustic bending mode of graphene is extended to the optical branch, whose polarization vector is perpendicular to the graphene layer. This observable is inaccessible in a continuous elastic model of graphene but it is readily obtained by the atomistic treatment. Our results suggest that the long-wavelength limit of the acoustic out-of-plane fluctuations of a free layer without stress is qualitatively similar to that predicted by a harmonic model under a tensile stress. This conclusion is a consequence of the anharmonicity of both in-plane and out-of-plane vibrational modes of the lattice. The most striking anharmonic effect is the presence of a linear term, ωA=vAk , in the dispersion relation of the acoustic bending band of graphene at long wavelengths (k →0 ). This term implies a strong reduction of the amplitude of out-of-plane oscillations in comparison to a flexural mode with a k2 dependence in the long-wavelength limit. Our simulations show an increase of the sound velocity associated to the bending mode, as well as an increase of its bending constant, κ , as the temperature increases. Moreover, the frequency of the optical bending mode, ωO(Γ ), also increases with the temperature. Our results are in agreement with recent analytical studies of the bending modes of graphene using either perturbation theory or an adiabatic approximation in the framework of continuous layer models.

  18. FT-IR, FT-Raman, UV-Visible, and NMR spectroscopy and vibrational properties of the labdane-type diterpene 13-epi-sclareol

    Science.gov (United States)

    Chain, Fernando E.; Leyton, Patricio; Paipa, Carolina; Fortuna, Mario; Brandán, Silvia A.

    2015-03-01

    In this work, FT-IR, FT-Raman, UV-Visible and NMR spectroscopies and density functional theory (DFT) calculations were employed to study the structural and vibrational properties of the labdane-type diterpene 13-epi-sclareol using the hybrid B3LYP method together with the 6-31G∗ basis set. Three stable structures with minimum energy found on the potential energy curves (PES) were optimized, and the corresponding molecular electrostatic potentials, atomic charges, bond orders, stabilization energies and topological properties were computed at the same approximation level. The complete assignment of the bands observed in the vibrational spectrum of 13-epi-sclareol was performed taking into account the internal symmetry coordinates for the three structures using the scaled quantum mechanical force field (SQMFF) methodology at the same level of theory. In addition, the force constants were calculated and compared with those reported in the literature for similar compounds. The predicted vibrational spectrum and the calculated 1H NMR and 13C NMR chemical shifts are in good agreement with the corresponding experimental results. The theoretical UV-Vis spectra for the most stable structure of 13-epi-sclareol demonstrate a better correlation with the corresponding experimental spectrum. The study of the three conformers by means of the theory of atoms in molecules (AIM) revealed different H bond interactions and a strong dependence of the interactions on the distance between the involved atoms. Furthermore, the natural bond orbital (NBO) calculations showed the characteristics of the electronic delocalization for the two six-membered rings with chair conformations.

  19. Vibrational spectroscopy of the phosphate mineral lazulite--(Mg, Fe)Al2(PO4)2·(OH)2 found in the Minas Gerais, Brazil.

    Science.gov (United States)

    Frost, Ray L; Xi, Yunfei; Beganovic, Martina; Belotti, Fernanda Maria; Scholz, Ricardo

    2013-04-15

    This research was done on lazulite samples from the Gentil mine, a lithium bearing pegmatite located in the municipality of Mendes Pimentel, Minas Gerais, Brazil. Chemical analysis was carried out by electron microprobe analysis and indicated a magnesium rich phase with partial substitution of iron. Traces of Ca and Mn, (which partially replaced Mg) were found. The calculated chemical formula of the studied sample is: (Mg0.88, Fe0.11)Al1.87(PO4)2.08(OH)2.02. The Raman spectrum of lazulite is dominated by an intense sharp band at 1060 cm(-1) assigned to PO stretching vibrations of of tetrahedral [PO4] clusters presents into the HPO4(2-) units. Two Raman bands at 1102 and 1137 cm(-1) are attributed to both the HOP and PO antisymmetric stretching vibrations. The two infrared bands at 997 and 1007 cm(-1) are attributed to the ν1PO4(3-) symmetric stretching modes. The intense bands at 1035, 1054, 1081, 1118 and 1154 cm(-1) are assigned to the ν3PO4(3-) antisymmetric stretching modes from both the HOP and tetrahedral [PO4] clusters. A set of Raman bands at 605, 613, 633 and 648 cm(-1) are assigned to the ν4 out of plane bending modes of the PO4, HPO4 and H2PO4 units. Raman bands observed at 414, 425, 460, and 479 cm(-1) are attributed to the ν2 tetrahedral PO4 clusters, HPO4 and H2PO4 bending modes. The intense Raman band at 3402 and the infrared band at 3403 cm(-1) are assigned to the stretching vibration of the OH units. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral lazulite to be understood. PMID:23434550

  20. Excited-state intramolecular hydrogen transfer (ESIHT) of 1,8-Dihydroxy-9,10-anthraquinone (DHAQ) characterized by ultrafast electronic and vibrational spectroscopy and computational modeling

    KAUST Repository

    Mohammed, Omar F.

    2014-05-01

    We combine ultrafast electronic and vibrational spectroscopy and computational modeling to investigate the photoinduced excited-state intramolecular hydrogen-transfer dynamics in 1,8-dihydroxy-9,10-anthraquinone (DHAQ) in tetrachloroethene, acetonitrile, dimethyl sulfoxide, and methanol. We analyze the electronic excited states of DHAQ with various possible hydrogen-bonding schemes and provide a general description of the electronic excited-state dynamics based on a systematic analysis of femtosecond UV/vis and UV/IR pump-probe spectroscopic data. Upon photoabsorption at 400 nm, the S 2 electronic excited state is initially populated, followed by a rapid equilibration within 150 fs through population transfer to the S 1 state where DHAQ exhibits ESIHT dynamics. In this equilibration process, the excited-state population is distributed between the 9,10-quinone (S2) and 1,10-quinone (S1) states while undergoing vibrational energy redistribution, vibrational cooling, and solvation dynamics on the 0.1-50 ps time scale. Transient UV/vis pump-probe data in methanol also suggest additional relaxation dynamics on the subnanosecond time scale, which we tentatively ascribe to hydrogen bond dynamics of DHAQ with the protic solvent, affecting the equilibrium population dynamics within the S2 and S1 electronic excited states. Ultimately, the two excited singlet states decay with a solvent-dependent time constant ranging from 139 to 210 ps. The concomitant electronic ground-state recovery is, however, only partial because a large fraction of the population relaxes to the first triplet state. From the similarity of the time scales involved, we conjecture that the solvent plays a crucial role in breaking the intramolecular hydrogen bond of DHAQ during the S2/S1 relaxation to either the ground or triplet state. © 2014 American Chemical Society.

  1. Interpenetrating polymer network membranes for fuel cells: infrared vibrational spectroscopy; Membranes baseadas dm redes polimericas interpenetrantes para celulas a combustivel: estudo por espectroscopia vibracional no infravermelho

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, Felipe A.M.; Rocco, Ana Maria [Grupo de Materiais Condutores e Energia, Escola de Quimica, Universidade Federal do Rio de Janeiro, RJ (Brazil)], e-mail: amrocco@eq.ufrj.br; Pereira, Robson Pacheco [Instituto de Ciencias Exatas, Universidade Federal Fluminense (UFF), Volta Redonda, RJ (Brazil)

    2011-07-01

    In the present work, proton conductive membranes based on IPN matrices doped with H{sub 3}PO{sub 4} were developed. The characterization by infrared vibrational spectroscopy evidenced the polymerization of DGEBA and the immobilization of PEI chains, originating a structure containing basic sites suitable for proton coordination and conduction. The FTIR characterization evidenced the polymerization of DGEBA in the presence of PEI thus forming Semi-IPN membranes which, after doped with H{sub 3}PO{sub 4}, exhibited conductivity values of 10{sup -4} W{sup -1}cm{sup -1} at room temperature and 10{sup -3} {omega}{sup -1}cm{sup -1} at 80 degree C, as well as a dependency of conductivity with temperature following the Arrhenius model. The activation energy values (14,33 and 12,96 kJ.mol{sup -1}) indicated a proton conduction mechanism predominantly vehicular in the matrices studied under 100% relative humidity. (author)

  2. Sum Frequency Generation Vibrational Spectroscopy and Kinetic Study of 2-Methylfuran and 2,5-Dimethylfuran Hydrogenation over 7 nm Platinum Cubic Nanoparticles

    KAUST Repository

    Aliaga, Cesar

    2011-04-28

    Sum frequency generation vibrational spectroscopy and kinetic measurements obtained from gas chromatography were used to study the adsorption and hydrogenation of 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) over cubic Pt nanoparticles of 7 nm average size, synthesized by colloidal methods and cleaned by ultraviolet light and ozone treatment. Reactions carried out at atmospheric pressure in the temperature range of 20-120 °C produced dihydro and tetrahydro species, as well as ring-opening products (alcohols) and ring-cracking products, showing high selectivity toward ring opening throughout the entire temperature range. The aromatic rings (MF and DMF) adsorbed parallel to the nanoparticle surface. Results yield insight into various surface reaction intermediates and the reason for the significantly lower selectivity for ring cracking in DMF hydrogenation compared to MF hydrogenation. © 2011 American Chemical Society.

  3. Use of vibrational spectroscopy to study protein and DNA structure, hydration, and binding of biomolecules: A combined theoretical and experimental approach

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.; Jürgensen, Vibeke Würtz; Claussen, Anetta;

    2006-01-01

    We report on our work with vibrational absorption, vibrational circular dichroism, Raman scattering, Raman optical activity, and surface-enhanced Raman spectroscopy to study protein and DNA structure, hydration, and the binding of ligands, drugs, pesticides, or herbicides via a combined theoretical...... and experimental approach. The systems we have studied systematically are the amino acids (L-alanine, L-tryptophan, and L-histidine), peptides (N-acetyl L-alanine N'-methyl amide, N-acetyl L-tryptophan N'-methyl amide, N-acetyl L-histidine N'-methyl amide, L-alanyl L-alanine, tri-L-serine, N-acetyl L......-alanine L-ploline L-tyrosine N'-methyl amide, Leu-enkephalin, cyclo-(gly-L-pro), N-acetyl (L-alanine)(n) N'-methyl amide), 3-methyl indole, and a variety of small molecules (dichlobenil and 2,6-dochlorobenzamide) of relevance to the protein systems under study. We have used molecular mechanics, the SCC...

  4. Vibrational spectroscopic characterisation of salmeterol xinafoate polymorphs and a preliminary investigation of their transformation using simultaneous in situ portable Raman spectroscopy and differential scanning calorimetry

    International Nuclear Information System (INIS)

    Knowledge and control of the polymorphic phases of chemical compounds are important aspects of drug development in the pharmaceutical industry. Salmeterol xinafoate, a long acting β-adrenergic receptor agonist, exists in two polymorphic Forms, I and II. Raman and near infrared spectra were obtained of these polymorphs at selected wavelengths in the range of 488-1064 nm; significant differences in the Raman and near-infrared spectra were apparent and key spectral marker bands have been identified for the vibrational spectroscopic characterisation of the individual polymorphs which were also characterised with X ray diffractometry. The solid-state transition of salmeterol xinafoate polymorphs was studied using simultaneous in situ portable Raman spectroscopy and differential scanning calorimetry isothermally between transitions. This method assisted in the unambiguous characterisation of the two polymorphic forms by providing a simultaneous probe of both the thermal and vibrational data. The study demonstrates the value of a rapid in situ analysis of a drug polymorph which can be of potential value for at-line in-process control

  5. Coherent vibrational dynamics

    CERN Document Server

    Lanzani, Guglielmo; De Silvestri, Sandro

    2007-01-01

    Vibrational spectroscopy is a powerful investigation tool for a wide class of materials covering diverse areas in physics, chemistry and biology. The continuous development in the laser field regarding ultrashort pulse generation has led to the possibility of producing light pulses that can follow vibrational motion coupled to the electronic transitions in molecules and solids in real time. Aimed at researchers and graduate students using vibrational spectroscopy, this book provides both introductory chapters as well as more advanced contents reporting on recent progress. It also provides a good starting point for scientists seeking a sound introduction to ultrafast optics and spectroscopic techniques.

  6. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction

    Science.gov (United States)

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-01

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe–Fe bonds, was found by EXAFS.

  7. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction.

    Science.gov (United States)

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-01

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe-Fe bonds, was found by EXAFS. PMID:27385480

  8. Structural, Potential Surface and Vibrational Spectroscopy Studies of Hypophosphorous Acid in the Gas Phase and Chain Conformation. A Theoretical Study

    International Nuclear Information System (INIS)

    The potential energy surfaces (PES), molecular and vibrational structure of hypophosphours acid (HPA) were investigated by HF, MP2 and DFT-B3LYP level of theory using 6-31G** basis set. In order to approach solid state spectra we optimized mono-, di-, tri-, tetra- and penta-mer structures and computed frequencies and intensities of the vibrational modes of VCD and IR. It is found that by increasing the number of HPA molecules in the chain, some of calculated vibrational frequencies approach to the experimental solid state values. The potential energy surfaces of HPA are calculated in a wide range on the plane perpendicular to the P-O bond where the hydrogen can rotate 360 degree through O=P-O-H dihedral angle. A circular valley is found going up and down on the plane, the valley is centered to the continuation of P-O bond. There are two minima at angles ±42.5.deg. to the O=P-O plane giving two mirror conformers and one saddle point in between with a height of 284.87 cm-1 at the angles 0.deg. and a complex barrier with a height of 2089.40 cm-1 at the angle 180.deg. to the same plane. On top of the complex barrier, there is a small well with depth of 15.65 cm-1. To study the tunneling effect and pathway between the two conformers, the molecule is considered to have CS symmetry and a symmetric double minimum potential energy well with a barrier of 284.87 cm-1 height in the middle. With the constructed potential, the torsional motion of P-O-H (Hindered Rotation) of the monomer, using variation method and harmonic oscillator wave functions is studied and IR frequencies and relative intensities of vibrational modes are calculated. Due to the width of the well and the trigonometric shape of the barrier, tunneling can occur at the ground state and the next excited state does not feel the barrier at all

  9. Microelemental and mineral compositions of pathogenic biomineral concrements: SRXFA, X-ray powder diffraction and vibrational spectroscopy data

    Energy Technology Data Exchange (ETDEWEB)

    Moroz, T.N. [Institute of Geology and Mineralogy, SB RAS, Pr. Akad. Koptyuga, 3, 630090 Novosibirsk (Russian Federation)], E-mail: moroz@uiggm.nsc.ru; Palchik, N.A.; Dar' in, A.V. [Institute of Geology and Mineralogy, SB RAS, Pr. Akad. Koptyuga, 3, 630090 Novosibirsk (Russian Federation)

    2009-05-11

    X-ray fluorescence analysis using synchrotron radiation (SRXRF), X-ray powder diffraction, infrared and Raman spectroscopy had been applied for determination of microelemental and mineral composition of the kidney stones, gallstones and salivalities from natives of Novosibirsk and Novosibirsk region, Russia. The relationship between mineral, organic and microelemental composition of pathogenic calcilus was shown.

  10. Thermal weights for semiclassical vibrational response functions

    Energy Technology Data Exchange (ETDEWEB)

    Moberg, Daniel R.; Alemi, Mallory; Loring, Roger F., E-mail: roger.loring@cornell.edu [Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 (United States)

    2015-08-28

    Semiclassical approximations to response functions can allow the calculation of linear and nonlinear spectroscopic observables from classical dynamics. Evaluating a canonical response function requires the related tasks of determining thermal weights for initial states and computing the dynamics of these states. A class of approximations for vibrational response functions employs classical trajectories at quantized values of action variables and represents the effects of the radiation-matter interaction by discontinuous transitions. Here, we evaluate choices for a thermal weight function which are consistent with this dynamical approximation. Weight functions associated with different semiclassical approximations are compared, and two forms are constructed which yield the correct linear response function for a harmonic potential at any temperature and are also correct for anharmonic potentials in the classical mechanical limit of high temperature. Approximations to the vibrational linear response function with quantized classical trajectories and proposed thermal weight functions are assessed for ensembles of one-dimensional anharmonic oscillators. This approach is shown to perform well for an anharmonic potential that is not locally harmonic over a temperature range encompassing the quantum limit of a two-level system and the limit of classical dynamics.

  11. Anharmonic phonons and magnons in BiFeO3

    International Nuclear Information System (INIS)

    The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 < T < 750K, using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. We do not find any evidence for a spin gap. A strong T-dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large amplitude motions of Bi and O ions observed with neutron diffraction. These results highlight the importance of spin-phonon coupling in this material.

  12. Anharmonic phonons and magnons in BiFeO3

    Energy Technology Data Exchange (ETDEWEB)

    Delaire, Olivier A [ORNL; Ma, Jie [ORNL; Stone, Matthew B [ORNL; Huq, Ashfia [ORNL; Gout, Delphine J [ORNL; Brown, Craig [National Institute of Standards and Technology (NIST); Wang, Kefeng [Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing; Ren, Zhifeng [Boston College, Chestnut Hill

    2012-01-01

    The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 < T < 750K , using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. We do not find any evidence for a spin gap. A strong T-dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large amplitude motions of Bi and O ions observed with neutron diffraction. These results highlight the importance of spin-phonon coupling in this material.

  13. Lattice thermal conductivity of filled skutterudites: An anharmonicity perspective

    International Nuclear Information System (INIS)

    We report a phenomenological model to calculate the high-temperature lattice thermal conductivity of filled skutterudite antimonides. The model needs no phonon resonant scattering terms. Instead, we assume that umklapp processes dominate the high-temperature phonon scattering. In order to represent the anharmonicity introduced by the filling atom, we introduce a Gaussian term into the relaxation time of the umklapp process. The developed model agrees remarkably well with the experimental results of REfCo4Sb12 and REfFe4Sb12 (RE = Yb, Ba, and Ca) alloys. To further test the validity of our model, we calculate the lattice thermal conductivity of nanostructured or multi-filled skutterudites. The calculation results are also in good agreement with experiment, increasing our confidence in the developed anharmonicity model.

  14. Dirac bound states of anharmonic oscillator in external fields

    Energy Technology Data Exchange (ETDEWEB)

    Hamzavi, Majid, E-mail: majid.hamzavi@gmail.com [Department of Physics, University of Zanjan, Zanjan (Iran, Islamic Republic of); Ikhdair, Sameer M., E-mail: sikhdair@gmail.com [Department of Physics, Faculty of Science, an-Najah National University, Nablus, West Bank, Palestine (Country Unknown); Department of Electrical and Electronic Engineering, Near East University, 922022 Nicosia, Northern Cyprus, Mersin 10 (Turkey); Falaye, Babatunde J., E-mail: fbjames11@physicist.net [Theoretical Physics Section, Department of Physics, University of Ilorin, P. M. B. 1515, Ilorin (Nigeria)

    2014-02-15

    We explore the effect of the external magnetic and Aharonov–Bohm (AB) flux fields on the energy levels of Dirac particle subjects to mixed scalar and vector anharmonic oscillator field in the two-dimensional (2D) space. We calculate the exact energy eigenvalues and the corresponding un-normalized two-spinor-components wave functions in terms of the chemical potential parameter, magnetic field strength, AB flux field and magnetic quantum number by using the Nikiforov–Uvarov (NU) method. -- Highlights: • Effect of the external fields on the energy levels of Dirac particle with the anharmonic oscillator is investigated. • The solutions are discussed in view of spin and pseudospin symmetries limits. • The energy levels and wave function are presented by the Nikiforov–Uvarov method.

  15. Superfluid Fermi Gases in a Rotating Anharmonic Trap

    Institute of Scientific and Technical Information of China (English)

    MA Juan; XUE Ju-Kui

    2011-01-01

    The quadrupole mode frequency, the monopole mode frequency, and the critical rotational frequency for stirring a single vortex nucleation along the BEC-BCS crossover are obtained. The results show that, in a rotating anisotropic anharmonic trap, the quadrupole mode frequency and the critical rotational frequency for stirring a single vortex nucleation are modified significantly when the system crosses from the BEC side to the BCS side: the anisotropy of the trap induces a downshift of the quadrupole mode frequency and the critical rotational frequency and helps the vortex formation in the system, while an anharmonic trap induces an upshift of the quadrupole mode frequency and the critical rotational frequency and suppresses the vortex formation in the system.

  16. Finite-element time evolution operator for the anharmonic oscillator

    Science.gov (United States)

    Milton, Kimball A.

    1995-01-01

    The finite-element approach to lattice field theory is both highly accurate (relative errors approximately 1/N(exp 2), where N is the number of lattice points) and exactly unitary (in the sense that canonical commutation relations are exactly preserved at the lattice sites). In this talk I construct matrix elements for dynamical variables and for the time evolution operator for the anharmonic oscillator, for which the continuum Hamiltonian is H = p(exp 2)/2 + lambda q(exp 4)/4. Construction of such matrix elements does not require solving the implicit equations of motion. Low order approximations turn out to be extremely accurate. For example, the matrix element of the time evolution operator in the harmonic oscillator ground state gives a results for the anharmonic oscillator ground state energy accurate to better than 1 percent, while a two-state approximation reduces the error to less than 0.1 percent.

  17. Path Integral Solution for an Angle-Dependent Anharmonic Oscillator

    Institute of Scientific and Technical Information of China (English)

    S.Haouat

    2012-01-01

    We have given a straightforward method to solve the problem of noncentral anharmonic oscillator in three dimensions. The relative propagator is presented by means of path integrals in spherical coordinates. By making an adequate change of time we are able to separate the angular motion from the radial one. The relative propagator is then exactly calculated. The energy spectrum and the corresponding wave functions are obtained.

  18. The role of damping for the driven anharmonic quantum oscillator

    CERN Document Server

    Guo, Lingzhen; André, Stephan; Schön, Gerd

    2011-01-01

    For the model of a linearly driven quantum anharmonic oscillator, the role of damping is investigated. We compare the position of the stable points in phase space obtained from a classical analysis to the result of a quantum mechanical analysis. The solution of the full master equation shows that the stable points behave qualitatively similar to the classical solution but with small modifications. Both the quantum effects and additional effects of temperature can be described by renormalizing the damping.

  19. A resurgence analysis for cubic and quartic anharmonic potentials

    CERN Document Server

    Gahramanov, Ilmar

    2016-01-01

    In this work we explicitly show resurgence relations between perturbative and one instanton sectors of the resonance energy levels for cubic and quartic anharmonic potentials in one-dimensional quantum mechanics. Both systems satisfy the Dunne-Unsal relation and hence we are able to derive one-instanton non-perturbative contributions with the fluctuation terms to the energy merely from the perturbative data. We confirm our results with previous results obtained by Zinn-Justin et al.

  20. Jacobian elliptic wave solutions in an anharmonic molecular crystal model

    International Nuclear Information System (INIS)

    Explicit Jacobian elliptic wave solutions are found in the anharmonic molecular crystal model for both the continuum limit and discrete modes. This class of wave solutions include the famous pulse-like and kink-like solitary modes. We would also like to report on the existence of some highly discrete staggered solitary wave modes not found in the continuum limit. (author). 9 refs, 1 fig

  1. Low energy electron diffraction (LEED) and sum frequency generation (SFG) vibrational spectroscopy studies of solid-vacuum, solid-air and solid-liquid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoffer, Saskia

    2002-08-19

    Electron based surface probing techniques can provide detailed information about surface structure or chemical composition in vacuum environments. The development of new surface techniques has made possible in situ molecular level studies of solid-gas interfaces and more recently, solid-liquid interfaces. The aim of this dissertation is two-fold. First, by using novel sample preparation, Low Energy Electron Diffraction (LEED) and other traditional ultra high vacuum (UHV) techniques are shown to provide new information on the insulator/vacuum interface. The surface structure of the classic insulator NaCl has been determined using these methods. Second, using sum frequency generation (SFG) surface specific vibrational spectroscopy studies were performed on both the biopolymer/air and electrode/electrolyte interfaces. The surface structure and composition of polyetherurethane-silicone copolymers were determined in air using SFG, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). SFG studies of the electrode (platinum, gold and copper)/electrolyte interface were performed as a function of applied potential in an electrochemical cell.

  2. Phonon anharmonicity and negative thermal expansion in SnSe

    Science.gov (United States)

    Bansal, Dipanshu; Hong, Jiawang; Li, Chen W.; May, Andrew F.; Porter, Wallace; Hu, Michael Y.; Abernathy, Douglas L.; Delaire, Olivier

    2016-08-01

    The anharmonic phonon properties of SnSe in the P n m a phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy, in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. The origin of the anharmonic phonon thermodynamics is linked to the electronic structure.

  3. Vibrational mid-infrared photothermal spectroscopy using a fiber laser probe: asymptotic limit in signal-to-baseline contrast.

    Science.gov (United States)

    Totachawattana, Atcha; Liu, Hui; Mertiri, Alket; Hong, Mi K; Erramilli, Shyamsunder; Sander, Michelle Y

    2016-01-01

    We report on a mid-infrared photothermal spectroscopy system with a near-infrared fiber probe laser and a tunable quantum cascade pump laser. Photothermal spectra of a 6 μm-thick 4-octyl-4'-cyanobiphenyl liquid crystal sample are measured with a signal-to-baseline contrast above 103. As both the peak photothermal signal and the corresponding baseline increase linearly with probe power, the signal-to-baseline contrast converges to an asymptotic limit for a given pump power. This limit is independent of the probe power and characterizes the best contrast achievable for the system. This enables sensitive quantitative spectral characterization of linear infrared absorption features directly from photothermal spectroscopy measurements. PMID:26696188

  4. The influence of external weak magnetic field on anharmonic nanocontacts of Josephson type

    International Nuclear Information System (INIS)

    The work considers the influence of weak external magnetic field on anharmonic Josephson's nanocontacts. The coordinate dependences of phase differences φ(x), superconducting current Is(x) and magnetic field H(x) anharmonic nanocontacts were found. It was defined the anharmonism parameter increase leads to phase difference φ(x) decaying faster, and penetration of magnetic field decreases. It was shown the considered contacts react on external weak magnetic field in more passive way

  5. Airy function approach and Numerov method to study the anharmonic oscillator potentials V(x = Ax2α + Bx2

    Directory of Open Access Journals (Sweden)

    N. Al Sdran

    2016-06-01

    Full Text Available The numerical solutions of the time independent Schrödinger equation of different one-dimensional potentials forms are sometime achieved by the asymptotic iteration method. Its importance appears, for example, on its efficiency to describe vibrational system in quantum mechanics. In this paper, the Airy function approach and the Numerov method have been used and presented to study the oscillator anharmonic potential V(x = Ax2α + Bx2, (A>0, B<0, with (α = 2 for quadratic, (α =3 for sextic and (α =4 for octic anharmonic oscillators. The Airy function approach is based on the replacement of the real potential V(x by a piecewise-linear potential v(x, while, the Numerov method is based on the discretization of the wave function on the x-axis. The first energies levels have been calculated and the wave functions for the sextic system have been evaluated. These specific values are unlimited by the magnitude of A, B and α. It’s found that the obtained results are in good agreement with the previous results obtained by the asymptotic iteration method for α =3.

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

    International Nuclear Information System (INIS)

    Resonance Raman and electronic absorption spectra are reported for the S0 and T1 states of the carotenoids β-carotene, zeaxanthin, echinenone, canthaxanthin, dihydroxylycopene, astaxanthin, decapreno(C50)-β-carotene, β-apo-8'-carotenal, and ethyl β-apo-8'-carotenoate. The results reveal qualitatively similar ground-state spectra and similar frequency shifts in all observed resonance Raman modes between S0 and T1, regardless of carotenoid structure. Examinations of the relationship of the putative C--C and C==C frequencies in S0 and T1 reveals anomalous shifts to lower frequency in the ''single-bond'' mode upon electronic excitation. These shifts may be due to molecular distortions in the excited state which force changes in molecular motions comprising the observed modes. However, another possibility requiring no distortion is that the interaction (off-diagonal) force constants connecting the C--C and C==C modes change sign upon electronic excitation. This latter phenomenon may provide a unitary explanation for the ''anomalous'' frequency shifts in the C--C and C==C modes, both in the T1 states of carotenoids and in the S1 states of simpler polyenes, without postulating large, unpredicted structural changes upon excitation or general errors in existing vibrational or theoretical analyses. Resonance Raman and absorbance studies with 35-ps time resolution suggest that S1 lifetime (of the 1B/sub u/ and/or the 1A/sub g/* states) of β-carotene in benzene is less than 1 ps

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1981-12-16

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

  8. Vibrational Spectroscopy and X-ray Diffraction of Cd(OH)2 to 28 GPa at 300 K

    OpenAIRE

    Shim, Sang-Heon; Rekhi, Sandeep; Martin, Michael C.; Jeanloz, Raymond

    2006-01-01

    We report Raman and infrared absorption spectroscopy along with X-ray diffraction for brucite-type beta-Cd(OH)2 to 28 GPa at 300 K. The OH-stretching modes soften with pressure and disappear at 21 GPa with their widths increasing rapidly above 5 GPa, consistent with a gradual disordering of the H sublattice at 5 20 GPa similar to that previously observed for Co(OH)2. Asymmetry in the peak shapes of the OH-stretching modes suggests the existence of diverse disordered sitesfor H atoms in C...

  9. Evaluation of non-radioactive lutetium- and yttrium-labeled immunoconjugates of rituximab - a vibrational spectroscopy study

    OpenAIRE

    Gjorgieva Ackova, Darinka; Smilkov, Katarina; Janevik-Ivanovska, Emilija; Stafilov, Trajče; Arsova-Sarafinovska, Zorica; Makreski, Petre

    2015-01-01

    Fourier Transform Infrared (FT-IR) and Raman Spectroscopy were used to study the molecular structure of the recombinant monoclonal antibody and anti-CD20-conjugates which are intended to be used as anti-cancer therapeutic agents. We characterized the secondary structure of a therapeutic immunoconjugates of rituximab, formulated with three different bifunctional chelating agents (p-SCN-Bn-DOTA, p-SCN-Bn-DTPA, 1B4M-DTPA) and labeled with non-radioactive lutetium and yttrium. The secondary struc...

  10. Vibrational spectroscopy of hydrated potassium hexauranate for the phase study of the UO3-KCl-H2O system

    International Nuclear Information System (INIS)

    In the study of the UO3-KCl-H2O system, a phase, called C phase, was isolated; it has a radiocrystallogram very close to the hexauranate K2U6O19,11H2O, but K+ and Cl- are found in its composition. Links between these two phases are studied and especially structure relationships. Hydrated potassium hexauranate structure was determined previously with a natural crystal. Position of potassium and uranium atoms only are known. As monocrystal preparation is impossible a direct structural study is impossible too. Vibrational spectroscopic analysis was selected for this study. Hexauranate structure is determined and results are extended for the study of the C phase. The hydrate UO3.0.8 H2O a stable and well defined compound is chosen for the hydrothermal synthesis of the different phases. Four main phases are evidenced: the chloro-uranate Ksub(x)UO3Clsub(x) (already known), a hydrated potassium uranate and two phases (one is the C phase) containing chloride ions are intermediaries between the chloro-uranate and the uranate

  11. Vibrational spectroscopy characterization of low level laser therapy on mammary culture cells: a micro-FTIR study

    Science.gov (United States)

    Magrini, Taciana D.; Villa dos Santos, Nathalia; Pecora Milazzotto, Marcella; Cerchiaro, Giselle; da Silva Martinho, Herculano

    2011-03-01

    Low level laser therapy (LLLT) is an emerging therapeutic approach for several clinical conditions. The clinical effects induced by LLLT presumably go from the photobiostimulation/photobioinibition at cellular level to the molecular level. The detailed mechanism underlying this effect is still obscure. This work is dedicated to quantify some relevant aspects of LLLT related to molecular and cellular variations. This goal was attached by exposing malignant breast cells (MCF7) to spatially filtered light of a He-Ne laser (633 nm) with 28.8 mJ/cm2 of fluency. The cell viability was evaluated by microscopic observation using Trypan Blue viability test. The vibrational spectra of each experimental group (micro- FTIR technique) were used to identify the relevant biochemical alterations occurred due the process. The red light had influence over RNA, phosphate and serine/threonine/tyrosine bands. Light effects on cell number or viability were not detected. However, the irradiation had direct influence on metabolic activity of cells.

  12. Hydrogen local vibrational modes in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    McCluskey, M D [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-06-01

    Following, a review of experimental techniques, theory, and previous work, the results of local vibrational mode (LVM) spectroscopy on hydrogen-related complexes in several different semiconductors are discussed. Hydrogen is introduced either by annealing in a hydrogen ambient. exposure to a hydrogen plasma, or during growth. The hydrogen passivates donors and acceptors in semiconductors, forming neutral complexes. When deuterium is substituted for hydrogen. the frequency of the LVM decreases by approximately the square root of two. By varying the temperature and pressure of the samples, the microscopic structures of hydrogen-related complexes are determined. For group II acceptor-hydrogen complexes in GaAs, InP, and GaP, hydrogen binds to the host anion in a bond-centered orientation, along the [111] direction, adjacent to the acceptor. The temperature dependent shift of the LVMs are proportional to the lattice thermal energy U(T), a consequence of anharmonic coupling between the LVM and acoustical phonons. In the wide band gap semiconductor ZnSe, epilayers grown by metalorganic chemical vapor phase epitaxy (MOCVD) and doped with As form As-H complexes. The hydrogen assumes a bond-centered orientation, adjacent to a host Zn. In AlSb, the DX centers Se and Te are passivated by hydrogen. The second, third, and fourth harmonics of the wag modes are observed. Although the Se-D complex has only one stretch mode, the Se-H stretch mode splits into three peaks. The anomalous splitting is explained by a new interaction between the stretch LVM and multi-phonon modes of the lattice. As the temperature or pressure is varied, and anti-crossing is observed between LVM and phonon modes.

  13. Two-dimensional-vibrational spectroscopy: Development and testing of a two-dimensional ultrafast Raman spectrometer with Time-Frequency Detection

    Science.gov (United States)

    Urbanek, Diana Camila

    The major emphasis of this dissertation will be given toward the theoretical tools necessary to acquire high resolution femtosecond Raman spectra from broadband femtosecond pulses. The theory of simultaneous Time-Frequency Detection (TFD) will be discussed and demonstrated to be a robust technique to acquire the vibrational coherence information. Finally, two experimental cases that demonstrate the feasibility of femtosecond TFD-CARS for acetonitrile and nitrobenzene will be presented. In the introductory first chapter, the motivation and fundamentals for developing 2D-vibrational spectroscopy using femtosecond Raman detection is presented. For coherent Raman spectroscopies, common femtosecond pulses often lie in an intermediate regime: their bandwidth is too wide for measurements in the frequency domain, but their temporal width is too broad for homodyne measurements in the time domain. A recent paper [Phys. Rev. Lett. 97 , 267401 (2006)] showed that complete Raman spectra can be recovered from intermediate length pulses by using simultaneous time and frequency detection (TFD). Heterodyne detection and a phase-stable local oscillator at the anti-Stokes frequency are not needed with TFD. Phase-control, pulse shaping or pulses of widely differing duration are not required. To demonstrate the TFD method, a high resolution Raman spectrum of nitrobenzene obtained from 60 fs pulses is discussed theoretically and experimentally in the second chapter. In the third chapter model calculations illustrate how information on the Raman spectrum is smoothly transferred from the frequency domain to the time domain as the pulse width shortens. When data is collected in both dimensions, the Raman spectrum is completely determined to high resolution, regardless of the probe pulse width. The TFD method is tested on experimental CARS data from acetonitrile in the fourth chapter. Compared to theoretical models, experimental data are complicated by noise and incomplete knowledge of the

  14. Ultrafast vibrational dynamics of the DNA backbone at different hydration levels mapped by two-dimensional infrared spectroscopy.

    Science.gov (United States)

    Guchhait, Biswajit; Liu, Yingliang; Siebert, Torsten; Elsaesser, Thomas

    2016-07-01

    DNA oligomers are studied at 0% and 92% relative humidity, corresponding to N  20 water molecules per base pair. Two-dimensional (2D) infrared spectroscopy of DNA backbone modes between 920 and 1120 cm(-1) maps fluctuating interactions at the DNA surface. At both hydration levels, a frequency fluctuation correlation function with a 300 fs decay and a slow decay beyond 10 ps is derived from the 2D lineshapes. The fast component reflects motions of DNA helix, counterions, and water shell. Its higher amplitude at high hydration level reveals a significant contribution of water to the fluctuating forces. The slow component reflects disorder-induced inhomogeneous broadening. PMID:26798841

  15. Vibrational spectroscopy and electrophoresis as a "golden means" in monitoring of polysaccharides in medical plant and gels

    Science.gov (United States)

    Pielesz, A.

    In recent years, some bioactive polysaccharides isolated from natural sources have attracted much attention in the field of biochemistry and pharmacology. Of them, polysaccharides or their glycoconjugates were shown to exhibit multiple biological activities including anticarcinogenic, anticoagulant, immunostimulating, antioxidant, etc. Pharmacotherapy using plant-derived substances can be currently regarded as a very promising future alternative to conventional therapy. The advanced biotechnologies available today enable chemical investigation of well-defined bioactive plant components as sources of novel drugs. The need for safer drugs without side effects has led to the use of natural ingredients with proven safety. Special interest is focused on plant polysaccharides. This article attempts to review the current structural and conformational characterization of some importantly bioactive monosaccharides isolated from following plant cell-wall: Symphytum officinale (comfrey), Thymus pulegioides (thyme), Trigonella foenum-graecum L. (fenugreek), Tussilago farfara L. (coltsfoot), Hyssopus officinalis (hyssop), Althaea officinalis L. (marshmallow) and Equisetum arvense L. (horsetail). The chemical structures of monosaccharides were analysed using FTIR and Raman spectroscopies as well as cellulose acetate membrane electrophoresis (CAE). The dried plant samples were gently hydrolysed with sulphuric acid. The presence of glucuronic acid, galacturonic acid, alginic acid, glucose, mannose and xylose in the hydrolysates of reference substances and non-defatted plant films was proved. The possibility of a taxonomic classification of plant cell walls based on infrared and Raman spectroscopies and the use of spectral fingerprinting for authentication and detection of adulteration of products rich in cell-wall materials are discussed. Individual bands were selected to monitor the sugar content in medical plant cell walls and to confirm the identity of the analysed plants.

  16. AKARI near-infrared spectroscopy of the extended green object G318.05+0.09: Detection of CO fundamental ro-vibrational emission

    CERN Document Server

    Onaka, Takashi; Sakon, Itsuki; Ardaseva, Aleksandra

    2016-01-01

    We present the results of near-infrared (2.5--5.4um) long-slit spectroscopy of the extended green object (EGO) G318.05+0.09 with AKARI. Two distinct sources are found in the slit. The brighter source has strong red continuum emission with H2O ice, CO2 ice, and CO gas and ice absorption features at 3.0, 4.25um, 4.67um, respectively, while the other greenish object shows peculiar emission that has double peaks at around 4.5 and 4.7um. The former source is located close to the ultra compact HII region IRAS 14498-5856 and is identified as an embedded massive young stellar object. The spectrum of the latter source can be interpreted by blue-shifted (-3000 ~ -6000km/s) optically-thin emission of the fundamental ro-vibrational transitions (v=1-0) of CO molecules with temperatures of 12000--3700K without noticeable H2 and HI emission. We discuss the nature of this source in terms of outflow associated with the young stellar object and supernova ejecta associated with a supernova remnant.

  17. Structural and vibrational investigation on species derived from the cyclamic acid in aqueous solution by using HATR and Raman spectroscopies and SCRF calculations

    Science.gov (United States)

    Brizuela, Alicia B.; Raschi, Ana B.; Castillo, María V.; Davies, Lilian; Romano, Elida; Brandán, Silvia A.

    2014-09-01

    In this study, aqueous solutions at different molar concentrations of sodium cyclamate in water were completely characterized by HATR (Horizontal Attenuated Total Reflectance) and Raman spectroscopies. The theoretical structures of cyclamate ion, the zwitterionic and neutral forms of the cyclamic acid and its dimer were optimized in gas and aqueous solution phases by using the hybrid B3LYP/6-31G* method. The solvent effects for the four species in aqueous solutions were simulated by using self-consistent reaction field (SCRF) calculations employing the integral equation formalism variant (IEFPCM) model. The complete assignments of the vibrational spectra of all the forms of cyclamic acid were performed taking into account the factor group analysis with the Scaled Quantum Mechanics Force Field (SQMFF) methodology. The existence of the zwitterionic and neutral forms of the cyclamic acid and its dimer in a solution of cyclamate in water is evidenced by characteristic bands in the HATR and Raman spectra. The dimerization of cyclamate in aqueous solution was previously reported by conductimetric method. The natural population analysis (NPA) and Merz-Kollman (MK) charges, molecular electrostatic potential (MEP), natural bond orbital (NBO) and atoms in molecules (AIM) calculations predict for all the species the principal donor and acceptor sites for the H bonds formation in aqueous solution. The SQM force fields for the cyclamate ion, the zwitterionic and neutral species of the cyclamic acid were obtained and their corresponding force constants in both phases were reported. Additionally, the solvation energies for those species were reported.

  18. IR and SFG vibrational spectroscopy of the water bend in the bulk liquid and at the liquid-vapor interface, respectively

    International Nuclear Information System (INIS)

    Vibrational spectroscopy of the water bending mode has been investigated experimentally to study the structure of water in condensed phases. In the present work, we calculate the theoretical infrared (IR) and sum-frequency generation (SFG) spectra of the HOH bend in liquid water and at the water liquid/vapor interface using a mixed quantum/classical approach. Classical molecular dynamics simulation is performed by using a recently developed water model that explicitly includes three-body interactions and yields a better description of the water surface. Ab-initio-based transition frequency, dipole, polarizability, and intermolecular coupling maps are developed for the spectral calculations. The calculated IR and SFG spectra show good agreement with the experimental measurements. In the theoretical imaginary part of the SFG susceptibility for the water liquid/vapor interface, we find two features: a negative band centered at 1615 cm−1 and a positive band centered at 1670 cm−1. We analyze this spectrum in terms of the contributions from molecules in different hydrogen-bond classes to the SFG spectral density and also compare to SFG results for the OH stretch. SFG of the water bending mode provides a complementary picture of the heterogeneous hydrogen-bond configurations at the water surface

  19. Adsorption of F2Cdbnd CFCl on TiO2 nano-powder: Structures, energetics and vibrational properties from DRIFT spectroscopy and periodic quantum chemical calculations

    Science.gov (United States)

    Tasinato, Nicola; Moro, Daniele; Stoppa, Paolo; Pietropolli Charmet, Andrea; Toninello, Piero; Giorgianni, Santi

    2015-10-01

    Photodegradation over titanium dioxide (TiO2) is a very appealing technology for removing environmental pollutants from the air, the adsorption interaction being the first step of the whole reaction pathway. In the present work the adsorption of F2Cdbnd CFCl (chlorotrifluoroethene, halon 1113), a compound used by industry and detected in the atmosphere, on a commercial TiO2 nano-powder is investigated experimentally by in situ DRIFT spectroscopy and theoretically through periodic ab initio calculations rooted in DFT. The spectra of the adsorbed molecule suggest that the anchoring to the surface mainly takes place through F atoms. Theoretically, five adsorption configurations for the molecule interacting with the anatase (1 0 1) surface are simulated at B3LYP level and for each of them, structures, binding energies and vibrational frequencies are derived. The interplay between theory and experiments shows the coexistence of different adsorption configurations, the foremost ones featuring the interaction of one F atom with a fivefold coordinated Ti4+ of the surface. These two adsorption models, which mostly differ for the orientation of the adsorbate with respect to the surface, feature a binding energy of -45.6 and -41.0 kJ mol-1 according to dispersion corrected DFT calculations. The favorable adsorption interaction appears as an important requirement toward the application of titanium dioxide technologies for the photocatalytic degradation of halon 1113.

  20. Hydrogenation of the alpha,beta-Unsaturated Aldehydes Acrolein, Crotonaldehyde, and Prenal over Pt Single Crystals: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

    Energy Technology Data Exchange (ETDEWEB)

    Kliewer, C.J.; Somorjai, G.A.

    2008-11-26

    Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three {alpha},{beta}-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr aldehyde, 100 Torr hydrogen) in the temperature range of 295K to 415K. SFG-VS data showed that acrolein has mixed adsorption species of {eta}{sub 2}-di-{sigma}(CC)-trans, {eta}{sub 2}-di-{sigma}(CC)-cis as well as highly coordinated {eta}{sub 3} or {eta}{sub 4} species. Crotonaldehyde adsorbed to Pt(111) as {eta}{sub 2} surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the {eta}{sub 2} adsorption species, and became more highly coordinated as the temperature was raised to 415K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation 'cracking' product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotylalcohol.

  1. Antifouling and antimicrobial mechanism of tethered quaternary ammonium salts in a cross-linked poly(dimethylsiloxane) matrix studied using sum frequency generation vibrational spectroscopy.

    Science.gov (United States)

    Ye, Shuji; Majumdar, Partha; Chisholm, Bret; Stafslien, Shane; Chen, Zhan

    2010-11-01

    Poly(dimethylsiloxane) (PDMS) materials containing chemically bound (''tethered'') quaternary ammonium salt (QAS) moieties are being developed as new contact-active antimicrobial coatings. Such coatings are designed to inhibit the growth of microorganisms on surfaces for a variety of applications which include ship hulls and biomedical devices. The antimicrobial activity of these coatings is a function of the molecular surface structure generated during film formation. Sum frequency generation (SFG) vibrational spectroscopy has been demonstrated to be a powerful technique to study polymer surface structures at the molecular level in different chemical environments. SFG was successfully used to characterize the surface structures of PDMS coatings containing tethered QAS moieties that possess systematic variations in QAS chemical composition in air, in water, and in a nutrient growth medium. The results indicated that the surface structure was largely dependent on the length of the alkyl chain attached to the nitrogen atom of the QAS moiety as well as the length of alkyl chain spanning between the nitrogen atom and silicon atom of the QAS moiety. The SFG results correlated well with the antimicrobial activity, providing a molecular interpretation of the activity. This research showed that SFG can be effectively used to aid in the development of new antimicrobial coating technologies by correlating the chemical structure of a coating surface to its antimicrobial activity. PMID:20345165

  2. Calculation of anharmonic couplings and THz linewidths in crystalline PETN

    International Nuclear Information System (INIS)

    We have developed a method for calculating the cubic anharmonic couplings in molecular crystals for normal modes with the zero wave vector in the framework of classical mechanics, and have applied it, combined with perturbation theory, to obtain the linewidths of all infrared absorption lines of crystalline pentaerythritol tetranitrate in the terahertz region (−1). Contributions of the up- and down-conversion processes to the total linewidth were calculated. The computed linewidths are in qualitative agreement with experimental data and the results of molecular dynamics simulations. Quantum corrections to the linewidths in the terahertz region are shown to be negligible

  3. Analytic WKB energy expressions for three-dimensional anharmonic oscillators

    International Nuclear Information System (INIS)

    A direct evaluation of the lowest-order WKB integral for three-dimensional quartic (V(r)=r4) and quartic anharmonic (V(r)=1/2ω2r2 + lambdar4) oscillators is carried out. The highly implicit relation for the energy defined by the WKB quantisation condition is expressed in terms of complete elliptic integrals. An approximate non-perturbative inversion of the implicit relation provides explicit analytic expressions for the energy which reproduce known energy values quite accurately. (author)

  4. Perfect Lattice Perturbation Theory A Study of the Anharmonic Oscillator

    CERN Document Server

    Bietenholz, W

    1999-01-01

    As an application of perfect lattice perturbation theory, we construct an O(\\lambda) perfect lattice action for the anharmonic oscillator analytically in momentum space. In coordinate space we obtain a set of 2-spin and 4-spin couplings \\propto \\lambda, which we evaluate for various masses. These couplings never involve variables separated by more than two lattice spacings. The O(\\lambda) perfect action is simulated and compared to the standard action. We discuss the improvement for the first two energy gaps \\Delta E_1, \\Delta E_2 and for the scaling quantity \\Delta E_2 / \\Delta E1 in different regimes of the interaction parameter, and of the correlation length.

  5. Effect of Anharmonicity on the Phonon Spectrum near its Discontinuity

    International Nuclear Information System (INIS)

    The method based on Green's function is used in investigating the effect of anharmonicity on the phonon spectrum near its discontinuity. In contrast to the usual case, the effect that phonon branches, which are independent in the harmonic approximation, have on one another requires the solution of the Dyson system of equations. The authors consider cases of significant and irregular discontinuity and show that for irregular discontinuity the excitations which arise can have a widely varying lifetime and frequency renormalization with respect to both value and temperature dependence. In particular, the one-phonon coherent neutron scattering cross section near the spectrum discontinuity is analysed. (author)

  6. Vibrational optical activity

    International Nuclear Information System (INIS)

    Recent vibrational activity (VOA) research is discussed. The vibrational circular dichroism (VCD) experiments were carried out with a Fourier transform infrared spectrometer. One of the major anticipations from VOA spectroscopy is to be able to derive new pathways for determining the molecular structure. Shown is Fourier transform infrared absorption and VCD spectra of lyxopyranose in pyradine-d5 solvent. Raman optical activity measurements are discussed, and depolarized Raman and Raman optical activity spectra for (+)-alpha-pinene are presented. It was concluded that at present Raman optical activity can be measured in the entire vibrational spectral region, where as VCD has not been measured below 600 cm-1

  7. Exploring the relationship between vibrational mode locality and coupling using constrained optimization

    Science.gov (United States)

    Molina, Andrew; Smereka, Peter; Zimmerman, Paul M.

    2016-03-01

    The use of alternate coordinate systems as a means to improve the efficiency and accuracy of anharmonic vibrational structure analysis has seen renewed interest in recent years. While normal modes (which diagonalize the mass-weighted Hessian matrix) are a typical choice, the delocalized nature of this basis makes it less optimal when anharmonicity is in play. When a set of modes is not designed to treat anharmonicity, anharmonic effects will contribute to inter-mode coupling in an uncontrolled fashion. These effects can be mitigated by introducing locality, but this comes at its own cost of potentially large second-order coupling terms. Herein, a method is described which partially localizes vibrations to connect the fully delocalized and fully localized limits. This allows a balance between the treatment of harmonic and anharmonic coupling, which minimizes the error that arises from neglected coupling terms. Partially localized modes are investigated for a range of model systems including a tetramer of hydrogen fluoride, water dimer, ethene, diphenylethane, and stilbene. Generally, partial localization reaches ˜75% of maximal locality while introducing less than ˜30% of the harmonic coupling of the fully localized system. Furthermore, partial localization produces mode pairs that are spatially separated and thus weakly coupled to one another. It is likely that this property can be exploited in the creation of model Hamiltonians that omit the coupling parameters of the distant (and therefore uncoupled) pairs.

  8. Calculating vibrational spectra without determining excited eigenstates: Solving the complex linear equations of damped response theory for vibrational configuration interaction and vibrational coupled cluster states.

    Science.gov (United States)

    Godtliebsen, Ian H; Christiansen, Ove

    2015-10-01

    It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde. PMID:26450293

  9. Vibrational spectroscopy and x-ray diffraction of Cd(OH)2 to 28 GPa at 300 K

    International Nuclear Information System (INIS)

    We report Raman and infrared absorption spectroscopy along with x-ray diffraction for brucite-typeβ-Cd(OH)2 to 28 GPa at 300 K. The OH-stretching modes soften with pressure and disappear at 21 GPa with their widths increasing rapidly above 5 GPa, consistent with a gradual disordering of the H sublattice at 5-20 GPa similar to that previously observed for Co(OH)2. Asymmetry in the peak shapes of the OH-stretching modes suggests the existence of diverse disordered sites for H atoms in Cd(OH)2 under pressure. Above 15 GPa, the A1g(T) lattice mode shows nonlinear behavior and softens to 21 GPa, at which pressure significant changes are observed: some Raman modes appear, two Raman-active lattice modes and the OH-stretching modes of the low-pressure phase disappear, and the positions of some x-ray diffraction lines change abruptly with the appearance of weak diffraction features. These observations suggest that amorphization of the H sublattice is accompanied by a crystalline-to-crystalline transition at 21 GPa in Cd(OH)2, which has not been previously observed in the brucite-type hydroxides. The Raman spectra of the high-pressure phase of Cd(OH)2 is similar to those of the high-pressure phase of single-crystal Ca(OH)2 of which structure has been tentatively assigned to the Sr(OH)2 type

  10. Vibrational spectroscopy and analytical electron microscopy studies of Fe-V-O and In-V-O thin films

    CERN Document Server

    Vuk, A S; Drazic, G; Colomban, P

    2002-01-01

    Orthovanadate (M sup 3 sup + VO sub 4; M= Fe, In) and vanadate (Fe sub 2 V sub 4 O sub 1 sub 3) thin films were prepared using sol-gel synthesis and dip coating deposition. Using analytical electron microscopy (AEM), the chemical composition and the degree of crystallization of the phases present in the thin Fe-V-O films were investigated. TEM samples were prepared in both orientations: parallel (plan view) and perpendicular (cross section) to the substrate. In the first stages of crystallization, when the particle sizes were in the nanometer range, the classical identification of phases using electron diffraction was not possible. Instead of measuring d values, experimentally selected area electron diffraction (SAED) patterns were compared to calculated (simulated) patterns in order to determine the phase composition. The problems of evaluating the ratio of amorphous and crystalline phases in thin films are reported. Results of TEM and XRD as well as IR and Raman spectroscopy showed that the films made at lo...

  11. Direct probing of photoinduced electron transfer in a self-assembled biomimetic [2Fe2S]-hydrogenase complex using ultrafast vibrational spectroscopy.

    Science.gov (United States)

    Li, Ping; Amirjalayer, Saeed; Hartl, František; Lutz, Martin; de Bruin, Bas; Becker, René; Woutersen, Sander; Reek, Joost N H

    2014-05-19

    A pyridyl-functionalized diiron dithiolate complex, [μ-(4-pyCH2-NMI-S2)Fe2(CO)6] (3, py = pyridine (ligand), NMI = naphthalene monoimide) was synthesized and fully characterized. In the presence of zinc tetraphenylporphyrin (ZnTPP), a self-assembled 3·ZnTPP complex was readily formed in CH2Cl2 by the coordination of the pyridyl nitrogen to the porphyrin zinc center. Ultrafast photoinduced electron transfer from excited ZnTPP to complex 3 in the supramolecular assembly was observed in real time by monitoring the ν(C≡O) and ν(C═O)NMI spectral changes with femtosecond time-resolved infrared (TRIR) spectroscopy. We have confirmed that photoinduced charge separation produced the monoreduced species by comparing the time-resolved IR spectra with the conventional IR spectra of 3(•-) generated by reversible electrochemical reduction. The lifetimes for the charge separation and charge recombination processes were found to be τCS = 40 ± 3 ps and τCR = 205 ± 14 ps, respectively. The charge recombination is much slower than that in an analogous covalent complex, demonstrating the potential of a supramolecular approach to extend the lifetime of the charge-separated state in photocatalytic complexes. The observed vibrational frequency shifts provide a very sensitive probe of the delocalization of the electron-spin density over the different parts of the Fe2S2 complex. The TR and spectro-electrochemical IR spectra, electron paramagnetic resonance spectra, and density functional theory calculations all show that the spin density in 3(•-) is delocalized over the diiron core and the NMI bridge. This delocalization explains why the complex exhibits low catalytic dihydrogen production even though it features a very efficient photoinduced electron transfer. The ultrafast porphyrin-to-NMI-S2-Fe2(CO)6 photoinduced electron transfer is the first reported example of a supramolecular Fe2S2-hydrogenase model studied by femtosecond TRIR spectroscopy. Our results show that TRIR

  12. Anharmonicity in light scattering by optical phonons in GaAs1-xBix

    Science.gov (United States)

    Joshya, R. S.; Rajaji, V.; Narayana, Chandrabhas; Mascarenhas, A.; Kini, R. N.

    2016-05-01

    We present a Raman spectroscopic study of GaAs1-xBix epilayers grown by molecular beam epitaxy. We have investigated the anharmonic effect on the GaAs-like longitudinal optical phonon mode ( LOGaAs' ) of GaAs1-xBix for different Bi concentrations at various temperatures. The results are analyzed in terms of the anharmonic damping effect induced by thermal and compositional disorder. We have observed that the anharmonicity increases with Bi concentration in GaAs1-xBix as evident from the increase in the anharmonicity constants. In addition, the anharmonic lifetime of the optical phonon decreases with increasing Bi concentration in GaAs1-xBix.

  13. Anharmonicity in Light Scattering by Optical Phonons in GaAs1-xBix

    Energy Technology Data Exchange (ETDEWEB)

    Joshya, R. S.; Rajaji, V.; Narayana, Chandrabhas; Mascarenhas, Angelo; Kini, R. N.

    2016-05-28

    We present a Raman spectroscopic study of GaAs 1-xBix epilayers grown by molecular beam epitaxy. We have investigated the anharmonic effect on the GaAs-like longitudinal optical phonon mode (LO'GaAs) of GaAs 1-xBix for different Bi concentrations at various temperatures. The results are analyzed in terms of the anharmonic damping effect induced by thermal and compositional disorder. We have observed that the anharmonicity increases with Bi concentration in GaAs 1-xBix as evident from the increase in the anharmonicity constants. In addition, the anharmonic lifetime of the optical phonon decreases with increasing Bi concentration in GaAs 1-xBix.

  14. Quantum dynamics and electronic spectroscopy within the framework of wavelets

    International Nuclear Information System (INIS)

    This paper serves as a first-time report on formulating important aspects of electronic spectroscopy and quantum dynamics in condensed harmonic systems using the framework of wavelets, and a stepping stone to our future work on developing anharmonic wavelets. The Morlet wavelet is taken to be the mother wavelet for the initial state of the system of interest. This work reports daughter wavelets that may be used to study spectroscopy and dynamics of harmonic systems. These wavelets are shown to arise naturally upon optical electronic transition of the system of interest. Natural birth of basis (daughter) wavelets emerging on exciting an electronic two-level system coupled, both linearly and quadratically, to harmonic phonons is discussed. It is shown that this takes place through using the unitary dilation and translation operators, which happen to be part of the time evolution operator of the final electronic state. The corresponding optical autocorrelation function and linear absorption spectra are calculated to test the applicability and correctness of the herein results. The link between basis wavelets and the Liouville space generating function is established. An anharmonic mother wavelet is also proposed in the case of anharmonic electron–phonon coupling. A brief description of deriving anharmonic wavelets and the corresponding anharmonic Liouville space generating function is explored. In conclusion, a mother wavelet (be it harmonic or anharmonic) which accounts for Duschinsky mixing is suggested. (paper)

  15. Stochastic Simulation of Chemical Exchange in Two Dimensional Infrared Spectroscopy

    CERN Document Server

    Sanda, F; Sanda, Frantisek; Mukamel, Shaul

    2006-01-01

    The stochastic Liouville equations are employed to investigate the combined signatures of chemical exchange (two-state-jump) and spectral diffusion (coupling to an overdamped Brownian oscillator) in the coherent response of an anharmonic vibration to three femtosecond infrared pulses. Simulations reproduce the main features recently observed in the OD stretch of phenol in benzene.

  16. Femtosecond nonlinear spectroscopy at surfaces: Second-harmonic probing of hole burning at the Si(111)7x7 surface and Fourier-transform sum-frequency vibrational spectroscopy

    International Nuclear Information System (INIS)

    The high temporal resolution and broad bandwidth of a femtosecond laser system are exploited in a pair of nonlinear optical studies of surfaces. The dephasing dynamics of resonances associated with the adatom dangling bonds of the Si(111)7 x 7 surface are explored by transient second-harmonic hole burning, a process that can be described as a fourth-order nonlinear optical process. Spectral holes produced by a 100 fs pump pulse at about 800 nm are probed by the second harmonic signal of a 100 fs pulse tunable around 800 nm. The measured spectral holes yield homogeneous dephasing times of a few tens of femtoseconds. Fits with a Lorentzian spectral hole centered at zero probe detuning show a linear dependence of the hole width on pump fluence, which suggests that charge carrier-carrier scattering dominates the dephasing dynamics at the measured excitation densities. Extrapolation of the deduced homogeneous dephasing times to zero excitation density yields an intrinsic dephasing time of ∼ 70 fs. The presence of a secondary spectral hole indicates that scattering of the surface electrons with surface optical phonons at 570 cm-1 occurs within the first 200 fs after excitation. The broad bandwidth of femtosecond IR pulses is used to perform IR-visible sum frequency vibrational spectroscopy. By implementing a Fourier-transform technique, we demonstrate the ability to obtain sub-laser-bandwidth spectral resolution. FT-SFG yields a greater signal when implemented with a stretched visible pulse than with a femtosecond visible pulse. However, when compared with multichannel spectroscopy using a femtosecond IR pulse but a narrowband visible pulse, Fourier-transform SFG is found to have an inferior signal-to-noise ratio. A mathematical analysis of the signal-to-noise ratio illustrates the constraints on the Fourier-transform approach

  17. Femtosecond nonlinear spectroscopy at surfaces: Second-harmonic probing of hole burning at the Si(111)7x7 surface and fourier-transform sum-frequency vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, John Andrew

    2004-11-24

    The high temporal resolution and broad bandwidth of a femtosecond laser system are exploited in a pair of nonlinear optical studies of surfaces. The dephasing dynamics of resonances associated with the adatom dangling bonds of the Si(111)7 x 7 surface are explored by transient second-harmonic hole burning, a process that can be described as a fourth-order nonlinear optical process. Spectral holes produced by a 100 fs pump pulse at about 800 nm are probed by the second harmonic signal of a 100 fs pulse tunable around 800 nm. The measured spectral holes yield homogeneous dephasing times of a few tens of femtoseconds. Fits with a Lorentzian spectral hole centered at zero probe detuning show a linear dependence of the hole width on pump fluence, which suggests that charge carrier-carrier scattering dominates the dephasing dynamics at the measured excitation densities. Extrapolation of the deduced homogeneous dephasing times to zero excitation density yields an intrinsic dephasing time of {approx} 70 fs. The presence of a secondary spectral hole indicates that scattering of the surface electrons with surface optical phonons at 570 cm{sup -1} occurs within the first 200 fs after excitation. The broad bandwidth of femtosecond IR pulses is used to perform IR-visible sum frequency vibrational spectroscopy. By implementing a Fourier-transform technique, we demonstrate the ability to obtain sub-laser-bandwidth spectral resolution. FT-SFG yields a greater signal when implemented with a stretched visible pulse than with a femtosecond visible pulse. However, when compared with multichannel spectroscopy using a femtosecond IR pulse but a narrowband visible pulse, Fourier-transform SFG is found to have an inferior signal-to-noise ratio. A mathematical analysis of the signal-to-noise ratio illustrates the constraints on the Fourier-transform approach.

  18. Resonant squeezing and the anharmonic decay of coherent phonons

    Science.gov (United States)

    Fahy, Stephen; Murray, Éamonn D.; Reis, David A.

    2016-04-01

    We show that the anharmonic decay of large-amplitude coherent phonons in a solid generates strongly enhanced squeezing of the phonon modes near points of the Brillouin zone where energy conservation in the three-phonon decay process is satisfied. The squeezing process leads to temporal oscillations of the mean-square displacement of target modes in resonance with the coherent phonon, which are characteristic of coherent phonon decay and do not occur in the decay of a phonon in a well-defined number state. For realistic material parameters of optically excited group-V semimetals, we predict that this squeezing results in strongly enhanced oscillations of the x-ray diffuse scattering intensity at sharply defined values of the x-ray momentum transfer. Numerical simulations of the phonon dynamics and the x-ray diffuse scattering in optically excited bismuth, using harmonic and anharmonic force parameters calculated with constrained density functional theory, demonstrate oscillations of the diffuse scattering intensity of magnitude 10%-20% of the thermal background at points of the Brillouin zone, where resonance occurs. Such oscillations should be observable using time-resolved optical-pump and x-ray-probe facilities available at current x-ray free-electron laser sources.

  19. Anharmonic lattice interactions in improper ferroelectrics for multiferroic design

    International Nuclear Information System (INIS)

    The design and discovery of new multiferroics, or materials that display both ferroelectricity and long-range magnetic order, is of fundamental importance for new electronic technologies based on low-power consumption. Far too often, however, the mechanisms causing these properties to arise are incompatible or occur at ordering temperatures below room temperature. One design strategy which has gained considerable interest is to begin with a magnetic material, and find novel ways to induce a spontaneous electric polarization within the structure. To this end, anharmonic interactions coupling multiple lattice modes have been used to lift inversion symmetry in magnetic dielectrics. Here we provide an overview of the microscopic mechanisms by which various types of cooperative atomic displacements result in ferroelectricity through anharmonic multi-mode coupling, as well as the types of materials most conducive to these lattice instabilities. The review includes a description of the origins of the displacive modes, a classification of possible non-polar lattice modes, as well as how their coupling can produce spontaneous polarizations. We then survey the recent improper ferroelectric literature, and describe how the materials discussed fall within a proposed classification scheme, offering new directions for the theoretical design of magnetic ferroelectrics. Finally, we offer prospects for the future discovery of new magnetic improper ferroelectrics, as well as detail remaining challenges and open questions facing this exciting new field. (topical review)

  20. Quantum Interference in the Vibrational Relaxation of the O-H Stretch Overtone of Liquid H2O.

    Science.gov (United States)

    van der Post, Sietse T; Woutersen, Sander; Bakker, Huib J

    2016-05-26

    Using femtosecond two-color infrared pump-probe spectroscopy, we study the vibrational relaxation of the O-H stretch vibrations of liquid H2O after excitation of the overtone transition. The overtone transition has its maximum at 6900 cm(-1) (1.45 μm), which is a relatively high frequency in view of the central frequency of 3400 cm(-1) of the fundamental transition. The excitation of the overtone leads to a transient induced absorption of two-exciton states of the O-H stretch vibrations. When the overtone excitation frequency is tuned from 6600 to 7200 cm(-1), the vibrational relaxation time constant of the two-exciton states increases from 400 ± 50 fs to 540 ± 40 fs. These values define a limited range of relatively long relaxation time constants compared to the range of relaxation time constants of 250-550 fs that we recently observed for the one-exciton O-H stretch vibrational state of liquid H2O ( S. T. van der Post et al., Nature Comm. 2015 , 6 , 8384 ). We explain the high central frequency and the limited range of relatively long relaxation time constants of the overtone transition from the destructive quantum interference of the mechanical and electrical anharmonic contributions to the overtone transition probability. As a result of this destructive interference, the overtone transition of liquid H2O is dominated by molecules of which the O-H groups donate relatively weak hydrogen bonds to other H2O molecules. PMID:27070075

  1. Determination of the anharmonicity constant of GaAs by means of the Bijvoet relation of the weak (666) reflection

    International Nuclear Information System (INIS)

    As a result of the influence of anomalous dispersion the weak (hhh) and ( anti h anti h anti h) reflections of the zinc blende structure differ from each other. At large scattering vectors this difference, described by the Bijvoet relation B, depends solely on the size of the anharmonic force constant β. It can be determined by measuring B near the K-absorption edge of any constituent. This experiment was performed for the (666) and ( anti 6 anti 6 anti 6) reflections of GaAs between λ=0.90 and 0.97 A using synchrotron radiation. Outside the extended X-ray absorption fine-structure spectroscopy region the integrated intensities decrease in a different manner with increasing λ for both reflections measured at 'umweganregung' free azimuthal positions. Under the assumption of βGa=-βAs and using the measured wavelength dependence of B, the anharmonicity constant is evaluated to β=-1.75(0.15)x10-17 J A-3 which is nearly the same as that for germanium. (orig.)

  2. Vibrations of the S1 state of fluorobenzene-h5 and fluorobenzene-d5 via resonance-enhanced multiphoton ionization (REMPI) spectroscopy

    OpenAIRE

    Harris, Joe P.; Andrejeva, Anna; Tuttle, William D.; Pugliesi, Igor; Schriever, Christian; Wright, Timothy G.

    2014-01-01

    We report resonance-enhanced multiphoton ionization spectra of the isotopologues fluorobenzeneh5 and fluorobenzene-d5. By making use of quantum chemical calculations, the changes in the wavenumber of the vibrational modes upon deuteration are examined. Additionally, the mixing of vibrational modes both between isotopologues and also between the two electronic states is discussed. The isotopic shifts lead to dramatic changes in the appearance of the spectrum as vibrations shift in and out of F...

  3. Rotationally resolved vibrational spectra of AsH3 + (" separators=" X ˜ 2 A2 ″) : Tunneling splittings studied by zero-kinetic-energy photoelectron spectroscopy

    Science.gov (United States)

    Sun, Wei; Dai, Zuyang; Wang, Jia; Mo, Yuxiang

    2016-06-01

    The rotationally resolved vibrational spectra of AsH3 + (" separators=" X ˜ 2 A2 ″) have been measured for the first time with vibrational energies up to 6000 cm-1 above the ground state using the zero-kinetic-energy photoelectron method. The symmetric inversion vibrational energy levels ( v2 +) and the corresponding rotational constants for v2 + = 0 -15 have been determined. The tunneling splittings of the inversion vibration energy levels have been observed and are 0.8 and 37.7 (±0.5) cm-1 for the ground and the first excited vibrational states, respectively. The first adiabatic ionization energy for AsH3 was determined as 79 243.3 ± 1 cm-1. The geometric parameters of AsH3 + (" separators=" X ˜ 2 A2 ″) as a function of inversion vibrational numbers have been determined, indicating that the geometric structure of the cation changes from near-planar to pyramidal with increasing inversion vibrational excitation. In addition to the experimental measurements, a two-dimensional theoretical calculation considering the two symmetric vibrational modes was performed to determine the energy levels of the symmetric inversion, which are in good agreement with the experimental results. The inversion vibrational energy levels of SbH3 + (" separators=" X ˜ 2 A2 ″) have also been calculated and are found to have much smaller energy splittings than those of AsH3 + (" separators=" X ˜ 2 A2 ″) .

  4. Chemical spectroscopy

    International Nuclear Information System (INIS)

    The purpose of chemical spectroscopy with neutrons is to utilize the dependence of neutron scattering cross-sections on isotope and on momentum transfer (which probes the spatial extent of the excitation) to understand fundamental and applied aspects of the dynamics of molecules and fluids. Chemical spectroscopy is divided into three energy ranges: vibrational spectroscopy, 25-500 MeV, for which much of the work is done on Be-filter analyzer instruments; low energy spectroscopy, less than 25 MeV; and high resolution spectroscopy, less than 1 MeV, which typically is performed on backscattering spectrometers. Representative examples of measurements of the Q-depenence of vibrational spectra, higher energy resolution as well as extension of the Q-range to lower values at high energy transfers, and provisions of higher sensitivities in vibrational spectroscopy are discussed. High resolution, high sensitivity, and polarization analysis studies in low energy spectroscopy are discussed. Applications of very high resolution spectroscopy are also discussed

  5. Simulations of Vibrational Spectra of Macromolecular Aggregates

    Czech Academy of Sciences Publication Activity Database

    Kessler, Jiří; Dračínský, Martin; Kiederling, T. A.; Bouř, Petr

    Kobe : -, 2013. P231-P231. [International Conference on Advanced Vibrational Spectroscopy /7./. 25.08.2013-30.08.2013, Kobe] Institutional support: RVO:61388963 Keywords : VCD * molecular spectroscopy * quantum chemistry Subject RIV: CF - Physical ; Theoretical Chemistry

  6. Validation of Spectra and Phase in Sub-1 cm-1 Resolution Sum-Frequency Generation Vibrational Spectroscopy through Internal Heterodyne Phase-Resolved Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Li; Chen, Shunli; Wang, Hongfei

    2016-03-03

    Reliably determination of the spectral features and their phases in sum-frequency generation vibrational spectroscopy (SFG-VS) for surfaces with closely overlapping peaks has been a standing issue. Here we present two approaches towards resolving such issue. The first utilizes the high resolution and accurate lineshape from the recently developed sub-wavenumber high resolution broadband SFG-VS (HR-BB-SFG-VS), from which the detail spectral parameters, including relative spectral phases, of overlapping peaks can be determined through reliable spectral fitting. These results are further validated by using the second method that utilizes the azimuthal angle phase dependence of the z-cut α-quartz crystal, a common phase standard, through the spectral interference between the SFG fields of the quartz surface, as the internal phase reference, and the adsorbed molecular layer. Even though this approach is limited to molecular layers that can be transferred or deposited onto the quartz surface, it is simple and straightforward, as it requires only an internal phase standard with a single measurement that is free of phase drifts. More importantly, it provides unambiguous SFG spectral phase information of such surfaces. Using this method, the absolute phase of the molecular susceptibility tensors of the CH3, CH2 and chiral C-H groups in different Langmuir-Blodgett (LB) molecular monolayers and drop-cast peptide films are determined. These two approaches are fully consistent with and complement to each other, making both easily applicable tools in SFG-VS studies. More importantly, as the HR-BB-SFG-VS technique can be easily applied to various surfaces and interfaces, such validation of the spectral and phase information from HR-BB-SFG-VS measurement demonstrates it as one most promising tool for interrogating the detailed structure and interactions of complex molecular interfaces.

  7. Electronic and vibrational Raman spectroscopy of Nd0.5Sr0.5MnO3 through the phase transitions

    Indian Academy of Sciences (India)

    Md Motin Seikh; A K Sood; Chandrabhas Narayana

    2005-01-01

    Raman scattering experiments have been carried out on single crystals of Nd0.5Sr0.5MnO3 as a function of temperature in the range of 320–50 K, covering the paramagnetic insulator–ferromagnetic metal transition at 250 K and the charge-ordering antiferromagnetic transition at 150 K. The diffusive electronic Raman scattering response is seen in the paramagnetic phase which continue to exist even in the ferromagnetic phase, eventually disappearing below 150 K. We understand the existence of diffusive response in the ferromagnetic phase to the coexistence of the different electronic phases. The frequency and linewidth of the phonons across the transitions show significant changes, which cannot be accounted for only by anharmonic interactions.

  8. Positron-attachment to small molecules: Vibrational enhancement of positron affinities with configuration interaction level of multi-component molecular orbital approach

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, Masanori [Quantum Chemistry Division, Graduate School of NanoBioScience, Yokohama City University, 22-2 Seto, Kanazawa, Yokohama 236-0027 (Japan)

    2015-12-31

    To theoretically demonstrate the binding of a positron to small polarized molecules, we have calculated the vibrational averaged positron affinity (PA) values along the local vibrational contribution with the configuration interaction level of multi-component molecular orbital method. This method can take the electron-positron correlation contribution into account through single electronic - single positronic excitation configurations. The PA values are enhanced by including the local vibrational contribution from vertical PA values due to the anharmonicity of the potential.

  9. Effective field theory for nuclear vibrations with quantified uncertainties

    CERN Document Server

    Pérez, E A Coello

    2015-01-01

    We develop an effective field theory (EFT) for nuclear vibrations. The key ingredients - quadrupole degrees of freedom, rotational invariance, and a breakdown scale around the three-phonon level - are taken from data. The EFT is developed for spectra and electromagnetic moments and transitions. We employ tools from Bayesian statistics for the quantification of theoretical uncertainties. The EFT consistently describes spectra and electromagnetic transitions for $^{62}$Ni, $^{98,100}$Ru, $^{106,108}$Pd, $^{110,112,114}$Cd, and $^{118,120,122}$Te within the theoretical uncertainties. This suggests that these nuclei can be viewed as anharmonic vibrators.

  10. Effective field theory for nuclear vibrations with quantified uncertainties

    Science.gov (United States)

    Coello Pérez, E. A.; Papenbrock, T.

    2015-12-01

    We develop an effective field theory (EFT) for nuclear vibrations. The key ingredients—quadrupole degrees of freedom, rotational invariance, and a breakdown scale around the three-phonon level—are taken from data. The EFT is developed for spectra and electromagnetic moments and transitions. We employ tools from Bayesian statistics for the quantification of theoretical uncertainties. The EFT consistently describes spectra and electromagnetic transitions for 62Ni,100,98Ru,108,106Pd, 110,112,114Cd, and 118,120,122Te within the theoretical uncertainties. This suggests that these nuclei can be viewed as anharmonic vibrators.

  11. Cohesive and anharmonic elastic properties of mixed fluorite crystals

    International Nuclear Information System (INIS)

    The cohesive and anharmonic elastic properties of four mixed fluorite crystals (CaxSr1-xF2, SrxBa1-xF2, BaxCa1-xF2 and CdxPb1-xF2) have been investigated by means of a three-body potential (TBP) model which consists of the long-range Coulomb and three-body interactions and the short-range van der Waals attraction and overlap repulsion effective upto the second neighbour ions. Due to the lack of measured data on cohesive energy, third-order elastic constants and pressure derivatives of the second-order elastic constants of mixed fluorites, the accuracy of the present results has been tested by comparing them with the so-called experimental results generated by the application of Vegard's law to their corresponding experimental values for the host fluorites. (author). 32 refs, 3 figs, 1 tab

  12. Approximation methods for the partition functions of anharmonic systems

    International Nuclear Information System (INIS)

    The analytical approximations for the classical, quantum mechanical and reduced partition functions of the diatomic molecule oscillating internally under the influence of the Morse potential have been derived and their convergences have been tested numerically. This successful analytical method is used in the treatment of anharmonic systems. Using Schwinger perturbation method in the framework of second quantization formulism, the reduced partition function of polyatomic systems can be put into an expression which consists separately of contributions from the harmonic terms, Morse potential correction terms and interaction terms due to the off-diagonal potential coefficients. The calculated results of the reduced partition function from the approximation method on the 2-D and 3-D model systems agree well with the numerical exact calculations

  13. 1/N-expansion for the anharmonic oscillator

    International Nuclear Information System (INIS)

    The properties of the 1/N-expansion for the anharmonic oscillator in quantum mechanics have been investigated. The first seven terms of the expansion for the energy of ground and first excited levels are obtained analytically. The high-order behaviour of the 1/N-expansion coefficients in closed form was found, the asymptotic series obtained being Borel summable. The formulae derived was used to find the first seven coefficients of the perturbative expansion in powers of the coupling constant in the case of the double-well potential for arbitrary number of components N. These exact expressions enable us to guess the large-order behaviour of the perturbative coefficients for N=0, 1, ... 4. An example of summing the asymptotic series in powers of 1/N applying the Pade-Borel method is given

  14. Critical rotation of an anharmonically trapped Bose-Einstein condensate

    Institute of Scientific and Technical Information of China (English)

    Ma Juan; Li Zhi; Xue Ju-Kui

    2009-01-01

    We consider rotational motion of an interacting atomic Bose-Einstein condensate (BEC) with both two- and threebody interactions in a quadratic-plus-quartic and harmonic-plus-Gaussian trap. By using the variational method, the influence of the three-body interaction and the anharmonicity of the trap on the lowest energy surface mode excitation and the spontaneous shape deformation (responsible for the vortex formation) in a rotating BEC is discussed in detail. It is found that the repulsive three-body interaction helps the formation of the vortex and reduces the lowest energy surface mode frequency and the critical rotational frequency of the system. Moreover, the critical rotational frequency for the vortex formation in the harmonic-plus-Gaussian potential is lower than that in the quadratic-plus-quartic potential.

  15. Vibrationally high-resolved electronic spectra of MCl2 (M=C, Si, Ge, Sn, Pb) and photoelectron spectra of MCl2(.).

    Science.gov (United States)

    Ran, Yibin; Pang, Min; Shen, Wei; Li, Ming; He, Rongxing

    2016-10-01

    We systematically studied the vibrational-resolved electronic spectra of group IV dichlorides using the Franck-Condon approximation combined with the Duschinsky and Herzberg-Teller effects in harmonic and anharmonic frameworks (only the simulation of absorption spectra includes the anharmonicity). Calculated results showed that the band shapes of simulated spectra are in accordance with those of the corresponding experimental or theoretical ones. We found that the symmetric bend mode in progression of absorption is the most active one, whereas the main contributor in photoelectron spectra is the symmetric stretching mode. Moreover, the Duschinsky and anharmonic effects exert weak influence on the absorption spectra, except for PbCl2 molecule. The theoretical insights presented in this work are significant in understanding the photophysical properties of MCl2 (M=C, Si, Ge, Sn, Pb) and studying the Herzberg-Teller and the anharmonic effects on the absorption spectra of new dichlorides of this main group. PMID:27280730

  16. FTIR spectroscopy of borate crystals

    Science.gov (United States)

    Kovacs, Laszlo; Beregi, E.; Polgar, K.; Peter, A.

    1999-03-01

    Infrared absorption spectroscopy has been used to study the vibrational modes in various borate crystals, the electronic transitions of Nd3+ ions in NYAB, and the stretching vibration of hydroxyl ions in CLBO crystals.

  17. Coriolis and anharmonicity couplings in the intramolecular vibrational energy flow: H+3 potential

    International Nuclear Information System (INIS)

    A classical study was conducted on the effects of Coriolis coupling on the internal energy flow between the two degenerate normal mode oscillations of H+3 . Strong correlations between the energy flow and the types of trajectories with the direction of the molecular rotation are revealed. The angle at which a trajectory, near its onset, approaches the isoenergetic contour on the potential surface is shown to determine the type of the trajectory and general characteristics of the system

  18. Anharmonic vibrations around a triaxial nuclear deformation “frozen” to γ = 30°

    Energy Technology Data Exchange (ETDEWEB)

    Buganu, Petrica, E-mail: buganu@theory.nipne.ro; Budaca, Radu [Department of Theoretical Physics, National Institute of Physics and Nuclear Engineering, Str. Reactorului 30, RO-077125, POB-MG6, Bucharest-Magurele (Romania)

    2015-12-07

    The Davydov-Chaban Hamiltonian with a sextic oscillator potential for the variable β and γ fixed to 30° is exactly solved for the ground and β bands and approximately for the γ band. The model is called Z(4)-Sextic in connection with the already established Z(4) solution. The energy spectra, normalized to the energy of the first excited state, and several B(E2) transition probabilities, normalized to the B(E2) transition from the first excited state to the ground state, depend on a single parameter α. By varying α within a sufficiently large interval, a shape phase transition from an approximately spherical shape to a deformed one is evidenced.

  19. A CRITICAL TEST OF VIBRATIONAL DEPHASING THEORIES IN SOLIDS USING SPONTANEOUS RAMAN SCATTERING IN ISOTOPICALLY MIXED CRYSTALS

    Energy Technology Data Exchange (ETDEWEB)

    Marks, S.; Cornelius, P.A.; Harris, C.B.

    1980-04-01

    A series of experiments has been conducted in order to evaluate the relative importance of several recent theories of vibrational dephasing in solids. The theories are discussed briefly, and are used to interpret the temperature dependence of the C-H and C-D stretch bands in the spontaneous Raman spectra of h{sub 14} - and d{sub 14}-1,2,4,5-tetramethyl benzene (durene). The infrared spectra of these same molecules are also reported in the region of the combination bands involving C-H (or C-D) stretches and low-frequency modes. The results support the applicability of the model of Harris, et. al., based on energy exchange in anharmonically coupled low-frequency modes. This theory is then used, in connection with Raman spectra obtained in isotopically mixed samples of durene, to elucidate the vibrational dynamics underlying the dephasing. It is found that the results are consistent with the hypothesis that some low-frequency modes in this molecule are significantly delocalized or 'excitonic' in character, and that this delocalization may be studied by means of a Raman spectroscopy on the low-frequency modes themselves, as well as by exchange analysis of the coupled high-frequency modes. These conclusions represent a generalization and extension of the previously published exchange model.

  20. Vibrations of the S1 state of fluorobenzene-h5 and fluorobenzene-d5 via resonance-enhanced multiphoton ionization (REMPI) spectroscopy.

    Science.gov (United States)

    Harris, Joe P; Andrejeva, Anna; Tuttle, William D; Pugliesi, Igor; Schriever, Christian; Wright, Timothy G

    2014-12-28

    We report resonance-enhanced multiphoton ionization spectra of the isotopologues fluorobenzene-h5 and fluorobenzene-d5. By making use of quantum chemical calculations, the changes in the wavenumber of the vibrational modes upon deuteration are examined. Additionally, the mixing of vibrational modes both between isotopologues and also between the two electronic states is discussed. The isotopic shifts lead to dramatic changes in the appearance of the spectrum as vibrations shift in and out of Fermi resonance. Assignments of the majority of the fluorobenzene-d5 observed bands are provided, aided by previous results on fluorobenzene-h5. PMID:25554159

  1. Vibrational behavior of Gelucire 50/13 by Raman and IR spectroscopies: A focus on the 1800-1000 cm-1 spectral range according to temperature and degree of hydration

    Science.gov (United States)

    El Hadri, M.; Achahbar, A.; El Khamkhami, J.; Khelifa, B.; Tran Le Tuyet, C.; Faivre, V.; Abbas, O.; El Marssi, M.; Bougrioua, F.; Bresson, S.

    2015-03-01

    The present paper reports on physical and thermal properties of polyoxyethylene glycol glycerides (Gelucire 50/13) used as sustained release matrix forming agent in pharmaceutical applications. Gelucire 50/13 was essentially studied by Raman and IR spectroscopies according to the temperature and the degree of hydration. The hydration behavior of this amphiphilic excipient has been investigated with increasing water contents to study the behavior during dissolution. In the spectral range 1800-1000 cm-1, Raman and IR spectroscopies of Gelucire 50/13 were performed to characterize the contribution of its each components at room temperature, with emphasis placed on the evolution of the CH2 wagging and twisting, ν(Csbnd C) and ν(Csbnd O) vibrational modes regions (1400-1000 cm-1), along with analysis of the IR and Raman-active δ(CH2) deformation region (1500-1400 cm-1). In comparison with temperature and degree of hydration, in the spectral range 1800-1000 cm-1, the vibrational changes were directly correlated with conformational changes of the Gelucire structure. Overall, IR and Raman spectroscopy clearly demonstrated that the different functional groups studied could be characterized independently, allowing for the understanding of their role in Gelucire structure.

  2. Advanced techniques for actinide spectroscopy (ATAS 2012). Abstract book

    International Nuclear Information System (INIS)

    The abstract book of the International workshop on advanced techniques for actinide spectroscopy (ATAS 2012) include contributions concerning the following issues: environmental applications, NMR spectroscopy, vibrational spectroscopy, X-ray spectroscopy and theory, technical application: separation processes, emission spectroscopy.

  3. Advanced techniques for actinide spectroscopy (ATAS 2012). Abstract book

    Energy Technology Data Exchange (ETDEWEB)

    Foerstendorf, Harald; Mueller, Katharina; Steudtner, Robin (eds.)

    2012-07-01

    The abstract book of the International workshop on advanced techniques for actinide spectroscopy (ATAS 2012) include contributions concerning the following issues: environmental applications, NMR spectroscopy, vibrational spectroscopy, X-ray spectroscopy and theory, technical application: separation processes, emission spectroscopy.

  4. Fermi-Decay Law of Bose—Einstein Condensate Trapped in an Anharmonic Potential

    International Nuclear Information System (INIS)

    The Fermi-decay law of Bose—Einstein condensate, which is trapped by a cigar-shaped anharmonic trap and subjected to a weak random perturbation, is investigated by numerically calculating quantum fidelity (Loschmidt echo), to reveal the coherence loss of the condensate. We find that there are three indispensable factors, anharmonic trap, weak random perturbation and nonlinear interaction, in charging of the Fermi-decay law. The anharmonic trap creates anharmonic oscillations, and the weak random perturbation causes coherence loss by disturbing their coherent oscillations, while the nonlinear interaction enhances the loss to the Fermi-decay law. Based on the Fermi-decay law, some suggestions are presented to prolong the coherent time during coherently manipulating condensates. (general)

  5. Phase equilibrium in poly(rA).poly(rU) complexes with Cd2+ and Mg2+ ions, studied by ultraviolet, infrared, and vibrational circular dichroism spectroscopy.

    Science.gov (United States)

    Blagoi, Yurii; Gladchenko, Galina; Nafie, Laurence A; Freedman, Teresa B; Sorokin, Victor; Valeev, Vladimir; He, Yanan

    2005-08-01

    Ultraviolet (UV) and infrared (IR) absorption and vibrational circular dichroism (VCD) spectroscopy were used to study conformational transitions in the double-stranded poly(rA). poly(rU) and its components-single-stranded poly(rA) and poly(rU) in buffer solution (pH 6.5) with 0.1M Na+ and different Mg2+ and Cd2+ (10(-6) to 10(-2) M) concentrations. Transitions were induced by elevated temperature that changed from 10 up to 96 degrees C. IR absorption and VCD spectra in the base-stretching region were obtained for duplex, triplex, and single-stranded forms of poly(rA) . poly(rU) at [Mg2+],[Cd2+]/[P] = 0.3. For single-stranded polynucleotides, the kind of conformational transition (ordering --> disordering --> compaction, aggregation) is conditioned by the dominating type of Me2+-polymer complex that in turn depends on the ion concentration range. The phase diagram obtained for poly(rA) . poly(rU) has a triple point ([Cd2+] approximately 10(-4)M) at which the helix-coil (2 --> 1) transition is replaced with a disproportion transition 2AU --> A2U + poly(rA) (2 --> 3) and the subsequent destruction of the triple helix (3 --> 1). The 2 --> 1 transitions occur in the narrow temperature interval of 2 degrees -5 degrees . Unlike 2 --> 1 and 3 --> 1 melting, the disproportion 2 --> 3 transition is a slightly cooperative one and observed over a wide temperature range. At [Me2+] approximately 10(-3) M, the temperature interval of A2U stability is not less than 20 degrees C. In the case of Cd2+, it increases with the rise of ion concentration due to the decrease of T(m) (2-->3). The T(m) (3-->1) value is practically unchanged up to [Cd2+] approximately 10(-3)M. Differences between diagrams for Mg(2+) and Cd2+ result from the various kinds of ion binding to poly(rA).poly-(rU) and poly(rA). PMID:15892121

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

    Science.gov (United States)

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

    2013-10-01

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

  7. Vibrational relaxation in pyridine upon supersonic expansion

    Science.gov (United States)

    Maris, Assimo; Favero, Laura B.; Danieli, Roberto; Favero, Paolo G.; Caminati, Walther

    2000-11-01

    The rotational spectra of five vibrational states of pyridine have been assigned and measured by millimeter wave absorption spectroscopy in a supersonic expansion. The intensities of the lines of the vibrational satellites with respect to the ground state after the supersonic expansion depend on the kind of carrier gas, backing pressure, pyridine concentration, and symmetry of the rotational and vibrational states. Several rotational transitions of the vibrational satellites have also been measured in a conventional cell to complete the spectral assignment.

  8. Vibrational analysis of phenol/(methanol)1

    Science.gov (United States)

    Gerhards, M.; Beckmann, K.; Kleinermanns, K.

    1994-09-01

    Ab initio calculations at the Hartree-Fock 4-31G* level were performed in order to calculate binding energies and vibrational frequencies of the phenol/CH3OH-cluster and two deuterated isotopomers ( d-phenol/CH3OD, d-phenol-CD3OD). The minimum energy structure is trans-linear, as for the phenol/H2O-cluster. The calculated frequencies of phenol and methanol as well as the intramolecular frequencies of the phenol/CH3OH-cluster are assigned to experimental values. The calculated intermolecular frequencies of the phenol/CH3OH-cluster are compared with the available experimental frequencies of the S 0 (and S 1)-state of the phenol/methanol-cluster and the similar p-cresol/methanol-cluster. Assignments are suggested for the σ and p 1-mode. In order to clarify the assignment of the low frequency vibration at 22 cm-1 anharmonic corrections for the β2-mode of the phenol/CH3OH-cluster are calculated. These calculations show only slight anharmonicity compared with the β2-mode calculations carried out for the phenol/H2O-cluster.

  9. Theoretical vibrational spectroscopy of intermediates and the reaction mechanism of the guanosine triphosphate hydrolysis by the protein complex Ras-GAP.

    Science.gov (United States)

    Khrenova, Maria G; Grigorenko, Bella L; Nemukhin, Alexander V

    2016-09-01

    The structures and vibrational spectra of the reacting species upon guanosine triphosphate (GTP) hydrolysis to guanosine diphosphate and inorganic phosphate (Pi) trapped inside the protein complex Ras-GAP were analyzed following the results of QM/MM simulations. The frequencies of the phosphate vibrations referring to the reactants and to Pi were compared to those observed in the experimental FTIR studies. A good correlation between the theoretical and experimental vibrational data provides a strong support to the reaction mechanism of GTP hydrolysis by the Ras-GAP enzyme system revealed by the recent QM/MM modeling. Evolution of the vibrational bands associated with the inorganic phosphate Pi during the elementary stages of GTP hydrolysis is predicted. PMID:27214270

  10. Vibrational spectroscopy of size-assigned p-cresol/H 2O-clusters in the S 0 and S 1 state

    Science.gov (United States)

    Pohl, M.; Schmitt, M.; Kleinermanns, K.

    1991-02-01

    Vibrational spectra of supersonically cooled complexes of p-cresol with H 2O and CH 3OH were analysed by mass-resolved two-photon ionisation, dispersed fluorescence and stimulated emission, detected by two-colour ionisation dip. In p-cresol·(H 2O) 1 progressions of the intermolecular cluster stretch vibration and its combination bands with intramolecular cluster vibrations were observed with similar frequencies in the S 0 and S 1 state. In p-cresol·(H 2O) 3 and p-cresol·(CH 3OH) 1, further intense intermolecular bands arise, namely the hydrogen-bridge bending and torsion vibration. This can be attributed to the lower symmetry of these clusters. Ab initio quantum chemical calculations show p-cresol·(H 2O) 3 to have a higher H-bond stretch frequency than p-cresol·(H 2O) 1 because its (unsymmetric) cyclic structure is more rigid.

  11. Theoretical vibrational spectroscopy of intermediates and the reaction mechanism of the guanosine triphosphate hydrolysis by the protein complex Ras-GAP

    Science.gov (United States)

    Khrenova, Maria G.; Grigorenko, Bella L.; Nemukhin, Alexander V.

    2016-09-01

    The structures and vibrational spectra of the reacting species upon guanosine triphosphate (GTP) hydrolysis to guanosine diphosphate and inorganic phosphate (Pi) trapped inside the protein complex Ras-GAP were analyzed following the results of QM/MM simulations. The frequencies of the phosphate vibrations referring to the reactants and to Pi were compared to those observed in the experimental FTIR studies. A good correlation between the theoretical and experimental vibrational data provides a strong support to the reaction mechanism of GTP hydrolysis by the Ras-GAP enzyme system revealed by the recent QM/MM modeling. Evolution of the vibrational bands associated with the inorganic phosphate Pi during the elementary stages of GTP hydrolysis is predicted.

  12. Ground state properties of a Bose-Einstein condensate confined in an anharmonic external potential

    Institute of Scientific and Technical Information of China (English)

    Wang Deng-Long; Yan Xiao-Hong; Tang Yi

    2004-01-01

    In light of the interference experiment of Bose-Einstein condensates, we present an anharmonic external potential model to study ground state properties of Bose-Einstein condensates. The ground state energy and the chemical potential have been analytically obtained, which are lower than those in harmonic trap. Additionally, it is found that the anharmonic strength of the external potential has an important effect on density and velocity distributions of the ground state for the Thomas-Fermi model.

  13. Vibrational coherence and energy transfer in two-dimensional spectra with the optimized mean-trajectory approximation

    International Nuclear Information System (INIS)

    The optimized mean-trajectory (OMT) approximation is a semiclassical method for computing vibrational response functions from action-quantized classical trajectories connected by discrete transitions that represent radiation-matter interactions. Here, we extend the OMT to include additional vibrational coherence and energy transfer processes. This generalized approximation is applied to a pair of anharmonic chromophores coupled to a bath. The resulting 2D spectra are shown to reflect coherence transfer between normal modes

  14. The importance of anharmonicity in thermal transport across solid-solid interfaces

    International Nuclear Information System (INIS)

    Understanding interfacial thermal transport is of great importance for applications like energy devices and thermal management of electronics. Despite the significant efforts in the past few decades, thermal transport across solid-solid interfaces is still not fully understood and cannot be accurately predicted. Anharmonicity is often ignored in many prediction models, such as the mismatch models, the wave-packet method, and the Atomic Green's function. In this paper, we use molecular dynamics to systematically study the role of anharmonicity in thermal transport across solid-solid interfaces. The interatomic interactions are modeled using force constants up to the third order. This model allows controlling the anharmonicity independently by tuning the cubic force constants. The interfacial thermal conductance as a function of anharmonicity inside the materials and that at the interface is studied. We found that the anharmonicity inside the materials plays an important role in the interfacial thermal transport by facilitating the energy communication between different phonon modes. The anharmonicity at the interface has much less impact on the interfacial thermal transport. These results are important to the modification of traditional models to improve their prediction power

  15. Overtone spectroscopy of some benzaldehyde derivatives

    Indian Academy of Sciences (India)

    P K Srivastava; D K Rai; S B Rai

    2001-06-01

    Overtone spectrum of , and -nitrobenzaldehydes and -chlorobenzaldehyde has been studied in 2000–12000 cm-1 region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of -disubstituted benzenes, the shift in aryl CH bond is proportional to sum of the Hammet of the substituents. However in the case of -disubstituted benzenes it is only 80% of the para-substituted shift.

  16. Accurate calculation of vibrational frequencies using explicitly correlated coupled-cluster theory.

    Science.gov (United States)

    Rauhut, Guntram; Knizia, Gerald; Werner, Hans-Joachim

    2009-02-01

    The recently proposed explicitly correlated CCSD(T)-F12x (x = a,b) approximations [T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106 (2007)] are applied to compute equilibrium structures and harmonic as well as anharmonic vibrational frequencies for H(2)O, HCN, CO(2), CH(2)O, H(2)O(2), C(2)H(2), CH(2)NH, C(2)H(2)O, and the trans-isomer of 1,2-C(2)H(2)F(2). Using aug-cc-pVTZ basis sets, the CCSD(T)-F12a equilibrium geometries and harmonic vibrational frequencies are in very close agreement with CCSD(T)/aug-cc-pV5Z values. The anharmonic frequencies are evaluated using vibrational self-consistent field and vibrational configuration interaction methods based on automatically generated potential energy surfaces. The mean absolute deviation of the CCSD(T)-F12a/aug-cc-pVTZ anharmonic frequencies from experimental values amounts to only 4.0 cm(-1). PMID:19206956

  17. Structure and intermolecular vibrations of 7-azaindole-water 2:1 complex in a supersonic jet expansion: Laser-induced fluorescence spectroscopy and quantum chemistry calculation

    Indian Academy of Sciences (India)

    Montu K Hazra; Moitrayee Mukherjee; V Ramanathan; Tapas Chakraborty

    2012-01-01

    Laser-induced fluorescence spectra of a 2:1 complex between 7-azaindole and water, known as `non-reactive dimer’ of the molecule, have been measured in a supersonic jet expansion. The dispersed fluorescence spectrum of the electronic origin band of the complex shows a very large number of low-frequency vibrational features corresponding to different intermolecular modes of the complex in the ground electronic state. Geometries of several possible isomeric structures of the complex and their vibrational frequencies at harmonic approximation were calculated by electronic structure theory method at MP2/6-31G∗∗ level. An excellent agreement is observed between the measured and calculated intermolecular vibrational mode frequencies for the energetically most favoured structure of the complex, where the water molecule is inserted within one of the two N$\\cdots$H-N hydrogen bonds of the 7AI dimer.

  18. Homogeneous and inhomogeneous broadenings and the Voigt line shapes in the phase-resolved and intensity sum-frequency generation vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shunli; Fu, Li; Gan, Wei; Wang, Hongfei

    2016-01-21

    In this report we show that the ability to measure the sub-1 cm-1 resolution phase-resolved and intensity high-resolution broadband sum frequency generation vibrational spectra (HR-BB-SFG-VS) of the –CN stretch vibration of the Langmuir-Blodgett (LB) monolayer of the 4-n-octyl-4’-cyanobiphenyl (8CB) on the z-cut α-quartz surface allows for the first time the direct comparison and understanding of the homogeneous and inhomogeneous broadenings in the imaginary and intensity SFG vibrational spectral lineshapes in detail. The difference of the full width at half maxima (FWHM) of the imaginary and intensity SFG-VS spectra of the same vibrational mode is the signature of the Voigt lineshape and it measures the relative contribution to the overall lineshape from the homogeneous and inhomogeneous broadenings in SFG vibrational spectra. From the phase-resolved and intensity spectra, we found that the FWHM of the 2238.00 ±0.02 cm-1 peak in the phase-resolved imaginary and intensity spectra is 19.2 ± 0.2 cm-1 and 21.6 ± 0.4 cm-1, respectively, for the –CN group of the 8CB LB monolayer on the z-cut α-quartz crystal surface. The FWHM width difference of 2.4 cm-1 agrees quantitatively with a Voigt lineshape with a homogeneous broadening half width of Γ = 5.29 ± 0.08 cm-1 and a inhomogeneous standard derivation width Δω = 5.42 ± 0.07 cm-1. These results shed new lights on the understanding and interpretation of the lineshapes of both the phase-resolved and the intensity SFG vibrational spectra, as well as other incoherent and coherent spectroscopic techniques in general.

  19. Theoretical Vibrational Spectroscopy of the E3B (Explicit Three-Body) Water Model and Evidence for a Liquid-Liquid Critical Point in Supercooled Water within This Model

    Science.gov (United States)

    Ni, Yicun

    Water, one of the most common substances on earth, is of tremendous importance for our daily life and many disciplines of science. Despite its simple molecular structure, water is very complicated and has many anomalies in condensed phases, mostly due to its vast and continuously changing hydrogen-bonding network. Experimentally, vibrational spectroscopy, especially in the OH bond stretch frequency region, is an ideal tool to investigate the microscopic structure and dynamics of this network. However, the interpretation of the experimental measurements usually needs the assistance of theoretical calculation. This thesis presents our recent work in simulating linear and non-linear vibrational spectroscopy of liquid water in diverse environments using a novel model. We believe our results provide new insights into this important and interesting field. In this thesis, we use a newly developed water model, named E3B, which explicitly includes three-body interaction terms in its Hamiltonian. We begin with the simulation of the two-dimensional sum frequency generation spectroscopy at the water/vapor interface. The result reveals the slow hydrogen-bond switching dynamics at the water liquid/vapor interface. Then we evaluate the E3B model by comparing the temperature dependence of the theoretical non-linear vibrational spectra to experimental data. The result shows that the E3B model outperforms other commonly used models in terms of the microscopic dynamics of liquid water in a wide temperature range. Next, we propose a spectroscopic map for the water bend mode, and use it to study the vibrational spectra of this mode in the bulk liquid and the surface. The result has a reasonable agreement with the experimental data. We suggest that the bend mode, although studied less often than the OH-stretch mode, provides complementary information about the microscopic structure of water. At last, we discuss another interesting topic, which is the proposed liquid-liquid critical

  20. Vibrational Microspectroscopy for Cancer Screening

    Directory of Open Access Journals (Sweden)

    Fiona M. Lyng

    2015-02-01

    Full Text Available Vibrational spectroscopy analyses vibrations within a molecule and can be used to characterise a molecular structure. Raman spectroscopy is one of the vibrational spectroscopic techniques, in which incident radiation is used to induce vibrations in the molecules of a sample, and the scattered radiation may be used to characterise the sample in a rapid and non-destructive manner. Infrared (IR spectroscopy is a complementary vibrational spectroscopic technique based on the absorption of IR radiation by the sample. Molecules absorb specific frequencies of the incident light which are characteristic of their structure. IR and Raman spectroscopy are sensitive to subtle biochemical changes occurring at the molecular level allowing spectral variations corresponding to disease onset to be detected. Over the past 15 years, there have been numerous reports demonstrating the potential of IR and Raman spectroscopy together with multivariate statistical analysis techniques for the detection of a variety of cancers including, breast, lung, brain, colon, oral, oesophageal, prostate and cervical cancer. This paper discusses the recent advances and the future perspectives in relation to cancer screening applications, focussing on cervical and oral cancer.