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Semiclassical time‐dependent theory of two‐photon spectroscopy. The effect of dephasing in the virtual level on the two‐photon excitation spectrum of isotachysterol
Author(s) -
Birge Robert R.,
Pierce Brian M.
Publication year - 1986
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560290407
Subject(s) - dephasing , semiclassical physics , virtual particle , excitation , photon , atomic physics , physics , wave packet , population , spectroscopy , chemistry , quantum mechanics , demography , sociology , quantum
Abstract It is commonly assumed that the nonlinear absorption of two photons is a process involving the simultaneous capture of two radiation quanta. The purpose of this paper is to evaluate semiclassically the spectroscopic consequences of relaxing this assumption by permitting dephasing in the virtual level. Semiclassical wave‐packet propagation theory is used to model the vibronic consequences of finite, virtual‐state population times. We demonstrate that extremely short virtual‐state lifetimes (1‒10 femtoseconds) can have a profound effect on two‐photon excitation line shapes and total vibronic envelopes. We provide experimental evidence suggesting that virtual state dephasing has an important influence on the two‐photon excitation spectrum of the polyene chromophore of isotachysterol. Our analysis suggests that dephasing in the virtual state is of poetntial importance in defining the vibronic development of two photon spectra of many polyatomic molecules in solution.