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  • 1
    Electronic Resource
    Electronic Resource
    Photon echoes of polyatomic molecules in condensed phases (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 179-190 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory of optical echo spectroscopies of large polyatomic molecules in condensed phases is developed. Using phase space correlation functions, we examine the interrelationships among the following optical measurements: ordinary photon echo, stimulated photon echo, accumulated photon echo, incoherent accumulated photon echo, and pump–probe absorption. Conditions for the elimination of inhomogeneous broadening in these experiments are specified. A multimode Brownian oscillator model is used to account for high frequency molecular vibrations, as well as solvent modes, and electronic dephasing processes. The effects of quantum beats, spectral diffusion, and homogeneous dephasing on the echo signals are studied and compared in detail with pump–probe and hole burning spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460376
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic dephasing, vibrational relaxation, and solvent friction in molecular nonlinear optical line shapes (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5160-5176 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The role of solvation dynamics in molecular nonlinear optical line shapes is analyzed using a reduced description based on the time evolution of the density matrix in Liouville space. Langevin equations are used to treat the coupling of the solvent to the molecular electronic and nuclear degrees of freedom. Electronic dephasing is calculated using a solvation coordinate which satisfies a generalized Fokker–Planck equation, and vibrational relaxation is related to the solvent viscosity and friction. The combined effect of both processes is incorporated into appropriate multitime correlation functions which are evaluated using a Liouville-space generating function. The present eigenstate-free approach is particularly suitable for calculating spectral line shapes as well as rate processes (isomerization, electron transfer) of large polyatomic molecules in condensed phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455634
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  • 3
    Electronic Resource
    Electronic Resource
    Intramolecular and solvent dynamics in femtosecond pump–probe spectroscopy (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3863-3873 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A density-matrix theory is applied to the calculation of femtosecond pump–probe experiments on solvated polyatomic molecules. Specific calculations are performed for a two-mode system, in which an optically active solute mode is represented by a pair of harmonic oscillators in the state representation, and the solute is modeled as an overdamped harmonic mode, using the Wigner phase space representation. No restrictions are placed on the relative time scales of the solute vibrational period, the solvent relaxation time scale and the pump pulse duration. The calculations demonstrate the physical phenomena observed in recent experiments on solvated dyes, both in the hole-burning limit, where the pump pulse is long compared to the relevant solute and solvent time scales, and the impulsive limit, for which the pump is short compared to the solute vibrational period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458772
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  • 4
    Electronic Resource
    Electronic Resource
    Semiclassical dynamics in Liouville space: Application to molecular electronic spectroscopy (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5735-5748 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A semiclassical theory of molecular dynamics and electronic spectroscopy, based on the propagation of a Liouville-space generating function (LGF) is developed. The method is particularly useful for treating the dynamics of systems, consisting of coupled classical and quantum degrees of freedom. Applications to intramolecular and intermolecular dynamics, correlation functions, and spectral line shapes in linear and nonlinear optical measurements are developed. The electronic absorption line shapes and Raman excitation profiles of model anharmonic molecules at finite temperatures are calculated as a demonstration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454533
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  • 5
    Electronic Resource
    Electronic Resource
    Non-Markovian optical dephasing dynamics in room temperature liquids investigated by femtosecond transient absorption spectroscopy: Theory and experiment (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 7855-7866 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper examines the electronic dephasing dynamics of the dye molecule HITCI in an ethylene glycol solution. Degenerate transient absorption data are presented as a function of laser pulse width and detuning from the absorption maximum. The dephasing dynamics revealed by the experimental results are shown to be non-Markovian. The experimental data cannot be quantitatively described by stochastic theories that assume a single relaxation time for the solvent. A model is presented that includes contributions from both fast and slow modulations to the absorption line shape. Using this approach, quantitative agreement is observed between theory and experiment. These results clearly indicate that multiple time scales for liquid dynamics contribute to the absorption line shape of solute molecules. The solvent parameters obtained are discussed in light of results from complementary experiments designed to measure characteristic relaxation times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466832
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular fluorescence and near resonance Raman yield as a probe for solvation dynamics (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6085-6107 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A microscopic theory for spontaneous emission line shapes of polyatomic molecules in condensed phases is developed. The distinction between the Raman and the fluorescence component is discussed and a rigorous transform relation between the total Raman excitation profile and the absorption line shape is obtained. The effects of solvation are introduced via generalized solvent line shape functions corresponding to the solvent dynamics before and after the reorganization process which follows the electronic excitation. The Raman yield and its frequency dependence are shown to provide a sensitive probe for the solvent dynamics. Detailed calculations for model systems and for the retinal chromophore in bacteriorhodopsin are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452448
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  • 7
    Electronic Resource
    Electronic Resource
    Time–frequency theory of pump-probe absorption spectroscopy (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 2212-2224 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A variation of density matrix formulation based on the nature of field–matter interference in a mixed time–frequency domain is developed to study molecular pump-probe absorption spectra in condensed phases. Considered are both the integrated probe transmitant signals and the frequency-dispersed transient absorption coefficients for molecular systems with either two or three electronic surfaces involved. The present formulation is exact and applicable to any field with arbitrary timescale and shape, and it is valid when the pulses are overlapped as well as separated. The dual temporal-spectral effect of both the excitation and detection fields can be clearly elucidated via a transformation that preserves causality. The resulting field–matter interference picture of transient absorption in the correlated time-frequency domain is conceptually natural and physically transparent. The molecular dynamics, and the field–matter temporal/spectral coherence and interference phenomena can all be clearly demonstrated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473146
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  • 8
    Electronic Resource
    Electronic Resource
    Time-resolved fluorescence and hole-burning line shapes of solvated molecules: Longitudinal dielectric relaxation and vibrational dynamics (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5840-5857 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop a microscopic theory of time- and frequency-resolved fluorescence and hole-burning measurements of polar, polyatomic molecules in a polar solvent. The line shapes are expressed in terms of gas phase spectroscopic parameters of the solute, vibrational relaxation rates, laser pulse shapes, and the dynamics of a solvation coordinate. These dynamics are then related to the frequency and wave vector dependent dielectric function of the solvent. Both fluorescence and hole-burning line shapes are predicted to show significant line narrowing at short times, and to undergo broadening and a red shift as the solvent relaxes. We propose hole burning as an alternative to fluorescence measurements in probing solvation dynamics. The time scale of the solvent induced line shift and line broadening is found to be independent of the shape of the solute, in contrast with previous work. The effects of vibrational relaxation are distinguished from those of solvent relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453507
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  • 9
    Electronic Resource
    Electronic Resource
    Reduced equations of motion for semiclassical dynamics in phase space (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 3441-3454 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-dependent self-consistent equations for semiclassical dynamics in phase space are developed. The method is based on constructing a Gaussian density matrix, whose equations of motion are obtained by requiring that the first two moments of the coordinates and momenta have the correct time evolution. The method can yield, in principle, the exact values of these moments for all time. The present method can be applied for the time evolution of mixed states in phase space and may, therefore, be particularly useful for molecular dynamics in condensed phases. Raman excitation profiles in anharmonic molecules are calculated and show excellent agreement with exact calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452000
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  • 10
    Electronic Resource
    Electronic Resource
    Intramolecular dephasing and vibrational redistribution in the dispersed fluorescence of ultracold molecules: Application to anthracene (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2021-2035 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A reduced description for spectral line shapes in isolated ultracold polyatomic molecules is developed. The vibrational degrees of freedom are partitioned into a system and a bath. The system modes are treated using a Green function eigenstate-free procedure. The bath modes induce intramolecular vibrational redistribution (IVR) and in addition are responsible for intramolecular dephasing resulting from their thermal fluctuations. The effects of the bath are introduced statistically via correlation functions. Application is made to the dispersed fluorescence of ultracold anthracene in a supersonic beam, which shows progression of narrow lines (Raman) and broad redistributed fluorescence. The observed red shift (with respect to the absorption) and line broadening in the emission indicate that the frequencies of the bath modes are on the average 6.4% lower in the electronically excited state compared with the ground state. We further obtain the IVR rates in the high energy region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453177
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