Vibrational line shape theory

To conclude, even if there exist several processes that affect the vibrational line shape it seems probable that when most of them have been sorted out and with the good agreement between theory and experiment, the lifetime broadening for a chemisorbed CO molecule is of the order of a few cm, corresponding to a lifetime of a few ps. The main vibrational energy relaxation mechanism is creation of electron-hole pairs caused by the local charge oscillations between the metal and the 2n molecular resonance crossing the Fermi level. 

We shall now briefly review the Kubo-Oxtoby theory of vibrational line-shape. The starting point for most theories of vibrational dephasing is the stochastic theory of lineshape first developed by Kubo [131]. This theory gives a simple expression for the broadened isotropic Raman line shape (/(< )) in terms of the Fourier transform of the normal coordinate time correlation function by... 

The exact Eq. (4.2.17) takes into account the effect of the reservoir (the condensed phase) on the spectral line shape through the parameter 77. Consideration of a concrete microscopic model of the valence-deformation vibrations makes it possible to estimate the basic parameters y and 77 of the theory and to introduce the exchange mode anharmonicity caused by a reorientation barrier of the deformation vibrations thereby, one can fully take advantage of the GF representation in the form (4.2.11) which allows summation over a finite number of states. 

The response of the system concerned to an external electromagnetic field is conveniently described in terms of double-time Green s function (GF) which can be introduced in a variety of representations.144,218 221 In what follows we will involve the representation in Matsubara s frequency space218 which is accepted in the theory of anharmonic crystals197 and provides a number of exact solutions in the case of a single adsorbed molecule.I50,1 2 In this approach, the spectral line shape for high-frequency vibrations can be determined as follows 184... 

The details of the mechanism of decay of states in alkanes retain their interest. The effect of deuterium on fluorescence lifetimes has been discussed in terms of the theory of radiationless transitions. Analysis of fluorescence line shapes and Raman excitation profiles of tetradesmethyl-p-carotene in isopentane has been carried out at 190 and 230K . Solvation occurs over a time scale of about 100 fs whilst vibrational relaxation has a time scale of about 250 fs. The kinetics of the interaction of alcohols with the excited state of triethylamine shows involvement of a charge transfer exciplex . Ionizing radiation is a means of exciting saturated hydrocarbons and the complexity of three component systems containing saturated hydrocarbons, aromatic solvent, and fluorescent solute has been examined. ... 

D, F. Heller and S. Mukamel, Theory of vibrational overtone line shapes of polyatomic molecules, J. Chem. Phys. 70 463 (1979). 

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