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  • 1
    Electronic Resource
    Electronic Resource
    Thermal boundary resistance and diffusivity measurements on thin YBa2Cu3O7−x films with MgO and SrTiO3 substrates using the transient grating method (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 850-857 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interface selective transient grating experiments are performed on oriented thin films (∼100 nm) of YBa2Cu3O7−x, with MgO and SrTiO3 substrates. The anisotropic YBa2Cu3O7−x thermal diffusivity constants and the thermal boundary resistance between the thin film and substrate are measured. Four different excitation and probe geometries are utilized such that each geometry results in a unique temporal decay. The grating has a significant amplitude on both sides of the film–substrate interface with a grating wave vector parallel to the interface. The four experimental geometries comprise an over-determined system that can be used to confirm the validity of the model assumptions. Numerical fits to the experimental data, using a straightforward diffusive model, are performed to obtain information on thermal diffusivity and to demonstrate the applicability of the technique to monitor anisotropic thermal relaxation processes in thin film–substrate structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353296
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  • 2
    Electronic Resource
    Electronic Resource
    Orientational correlation functions and polarization selectivity for nonlinear spectroscopy of isotropic media. II. Fifth order (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 13-21 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The influence of orientational relaxation on the fifth-order nonlinear polarization is evaluated for off-resonant Raman and dipole resonant experiments in the perturbative limit. The symmetry properties of the χ(5) tensor are discussed, and correlation functions for orientational diffusion are calculated for all fifth-order tensor elements relevant to isotropic media. The results allow generalization of the effect of orientational motion on the nonlinear experiment of arbitrary order. The general polarization dependence of the fifth-order experiments are obtained and used to address the selectivity of certain polarization geometries to orientational dynamics. It is shown that for χ(5) Raman spectroscopies, no combination of polarizations will give complete selectivity to the isotropic, anisotropic, or nonresonant contributions to the Raman polarizability tensor. Similar restriction of selectivity exists for resonant experiments. Polarization conditions are suggested to facilitate the comparison of third- and fifth-order spectroscopies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471859
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  • 3
    Electronic Resource
    Electronic Resource
    Vibrational Dynamics of Carbon Monoxide at the Active Site of Myoglobin: Picosecond Infrared Free-Electron Laser Pump-Probe Experiments (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 11213-11219 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100094a032
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  • 4
    Electronic Resource
    Electronic Resource
    Vibrational photon echoes in a liquid and glass: Room temperature to 10 K (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1741-1744 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Picosecond infrared vibrational photon echo experiments were performed on the asymmetric CO stretching mode (1983 cm−1) of tungsten hexacarbonyl in 2-methylpentane from room temperature to 10 K using a free electron laser. This is the first report of a room temperature infrared vibrational photon echo in a liquid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467731
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  • 5
    Electronic Resource
    Electronic Resource
    Homogeneous vibrational dynamics and inhomogeneous broadening in glass-forming liquids: Infrared photon echo experiments from room temperature to 10 K (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2810-2826 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A study of the temperature dependence of the homogeneous linewidth and inhomogeneous broadening of a high-frequency vibrational transition of a polyatomic molecule in three molecular glass-forming liquids is presented. Picosecond infrared photon echo and pump–probe experiments were used to examine the dynamics that give rise to the vibrational line shape. The homogeneous vibrational linewidth of the asymmetric CO stretch of tungsten hexacarbonyl (∼1980 cm−1) was measured in 2-methylpentane, 2-methyltetrahydrofuran, and dibutylphthalate from 300 K, through the supercooled liquids and glass transitions, to 10 K. The temperature dependences of the homogeneous linewidths in the three glasses are all well described by a T2 power law. The absorption linewidths for all glasses are seen to be massively inhomogeneously broadened at low temperature. In the room temperature liquids, while the vibrational line in 2-methylpentane is homogeneously broadened, the line in dibutylphthalate is still extensively inhomogeneously broadened. The contributions of vibrational pure dephasing, orientational diffusion, and population lifetime to the homogeneous line shape are examined in detail in the 2-methylpentane solvent. The complete temperature dependence of each of the contributions is determined. For this system, the vibrational line varies from inhomogeneously broadened in the glass and low temperature liquid to homogeneously broadened in the room temperature liquid. The homogeneous linewidth is dominated by the vibrational lifetime at low temperatures and by pure dephasing in the liquid. The orientational relaxation contribution to the line is significant at some temperatures but never dominant. Restricted orientational relaxation at temperatures below ∼120 K causes the homogeneous line shape to deviate from Lorentzian, while at higher temperatures the line shape is Lorentzian. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470517
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  • 6
    Electronic Resource
    Electronic Resource
    Vibrational spectral diffusion and population dynamics in a glass-forming liquid: Variable bandwidth picosecond infrared spectroscopy (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3919-3931 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temperature-dependent vibrational population dynamics and spectral diffusion of the CO stretching mode of tungsten hexacarbonyl in 2-methylpentane are observed from the room temperature liquid to the low temperature glass using picosecond infrared transient grating and pump–probe experiments. These experiments were performed between 10 and 300 K on the triply degenerate T1u asymmetric CO stretching mode at 1984 cm−1 using pulses with bandwidths narrower and wider than the absorption bandwidth of the transition. The rate of vibrational population relaxation (100≤T1〈150 ps) is observed to decrease with increasing temperature. The orientational dynamics for this transition are observed on a faster time scale than the population relaxation. Although the liquid viscosity changes over 14 orders of magnitude, the orientational relaxation rate slows by less than one order of magnitude over the full temperature range. By comparing polarization-dependent experiments performed with both narrow and broad bandwidth transform-limited pulses, it is possible to measure temperature-dependent spectral diffusion in both the liquid and the glass. The spectral diffusion and the orientational relaxation are shown to be intimately related. It is proposed that both arise from the time evolution of the superposition of the three degenerate states created by the excitation pulse. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468568
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  • 7
    Electronic Resource
    Electronic Resource
    Distance dependence of electronic energy transfer between donor and acceptor adlayers: p-terphenyl and 9,10-diphenylanthracene (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 1968-1980 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Investigations of energy transfer between adlayers on single-crystal surfaces provide a unique opportunity to explore electronic energy transfer in restricted geometries. In this study, laser induced fluorescence techniques and donor quantum yield measurements were used to examine the distance dependence of electronic energy transfer between donor and acceptor adlayers on Al2O3(0001). The donor adlayer was p-terphenyl, the acceptor adlayer was 9,10-diphenylanthracene, and n-butane was the variable spacer adlayer. The electronic energy transfer rates vs spacer thickness were determined at both 30 and 85 K in ultra high vacuum. The butane spacer experiments showed that the donor energy transfer rate decreased with a 1/d3 dependence, where d is the thickness of the spacer adlayer. Given a Förster quantum mechanical or a Kuhn classical energy transfer mechanism with randomly oriented dipoles, a 1/d3 distance dependence is consistent with resonance electronic energy transfer from a two-dimensional donor adlayer to a three-dimensional array of acceptors. The spacer measurements yielded a critical transfer distance of d0=44 ±4 A(ring) at 30 K and d0=33 ±6 A(ring) at 85 K. The differences in the critical transfer distance at 30 and 85 K could be explained by the redshift in the p-terphenyl fluorescence spectrum at 85 K that reduces the overlap between the donor fluorescence and acceptor absorption spectra. Values of d0=44 A(ring) at 30 K and d0=35 A(ring) at 85 K were calculated theoretically from a 1/d3 analysis and were in excellent agreement with the experimental measurements. The rate of donor–donor intralayer energy migration was also determined by measuring the electronic energy transfer rate versus donor coverage on the acceptor adlayer. The donor quantum yield measurements versus donor adlayer coverage were consistent with the spacer results and indicated that electronic energy migration does not occur within the p-terphenyl adlayer. These results vs spacer thickness and donor coverage reveal that electronic energy transfer in spatially confined geometries can be described using a modified Kuhn energy transfer mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466549
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature-dependent vibrational relaxation in polyatomic liquids: Picosecond infrared pump–probe experiments (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 9035-9043 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational lifetimes of metal carbonyl solutes in two liquids were studied as a function of temperature from the melting points to the boiling points. Picosecond infrared pump–probe experiments were performed at the absorption maxima of the T1u CO stretching vibration (∼1980 cm−1) of Cr(CO)6 and W(CO)6 dissolved in carbon tetrachloride (CCl4) and chloroform (CHCl3). The temperature dependencies of the lifetimes in CCl4 are dramatically different from those in CHCl3. A decrease in the vibrational lifetime with temperature is seen for both metal carbonyls in CCl4. However, the vibrational lifetime of W(CO)6 in CHCl3 becomes longer as the temperature is increased, while the lifetime of Cr(CO)6 decreases only slightly. To understand the vibrational dynamics in these systems it is necessary to consider the temperature dependencies of the thermal populations of low frequency phonons (instantaneous normal modes) of the liquids, the phonon density of states, and the anharmonic coupling matrix elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466709
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  • 9
    Electronic Resource
    Electronic Resource
    Theory of vibrational relaxation of polyatomic molecules in liquids (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 10618-10629 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple tractable theory of vibrational relaxation of polyatomic molecules in polyatomic solvents, which is also applicable to solid solutions, is presented. The theory takes as its starting point Fermi's golden rule, avoids additional assumptions such as the rotating wave or random phase approximations, and treats both the internal degrees of freedom of the relaxing molecule and the bath degrees of freedom in a fully quantum mechanical manner. The results yield intuitively understandable expressions for the relaxation rates. The treatment of the annihilation as well as the creation of all participating bosons allows the theory to go beyond earlier analyses which treated only cascade processes. New predicted features include temperature effects and asymmetry effects in the frequency dependence. The theory is constructed in a manner which facilitates the use of recent developments in the analysis of instantaneous normal modes of liquids. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467876
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  • 10
    Electronic Resource
    Electronic Resource
    The low frequency density of states and vibrational population dynamics of polyatomic molecules in liquids (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3325-3334 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Instantaneous normal mode calculations of the low frequency solvent modes of carbon tetrachloride (CCl4) and chloroform (CHCl3), and experiments on the vibrational population dynamics of the T1u CO stretching mode (∼1980 cm−1) of tungsten hexacarbonyl in CCl4 and CHCl3 are used to understand factors affecting the temperature dependence of the vibrational lifetime. Picosecond infrared pump–probe experiments measuring the vibrational lifetime of the T1u mode from the melting points to the boiling points of the two solvents show a dramatic solvent dependence. In CCl4, the vibrational lifetime decreases as the temperature is increased; however, in CHCl3, the vibrational lifetime actually becomes longer as the temperature is increased. The change in thermal occupation numbers of the modes in the solute/solvent systems cannot account for this difference. Changes in the density of states of the instantaneous normal modes and changes in the magnitude of the anharmonic coupling matrix elements are considered. The calculated differences in the temperature dependences of the densities of states appear too small to account for the observed difference in trends of the temperature dependent lifetimes. This suggests that the temperature dependence of the liquid density causes significant changes in the magnitude of the anharmonic coupling matrix elements responsible for vibrational relaxation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470266
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