RELAXATION THEORY FOR CURVE-CROSSING CORRECTIONS TO ELECTRONIC ABSORPTION-LINE SHAPES IN CONDENSED PHASES

Citation
Dg. Evans et Rd. Coalson, RELAXATION THEORY FOR CURVE-CROSSING CORRECTIONS TO ELECTRONIC ABSORPTION-LINE SHAPES IN CONDENSED PHASES, The Journal of chemical physics, 99(9), 1993, pp. 6264-6277
Citations number
65
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics, Atomic, Molecular & Chemical
ISSN journal
0021-9606
Volume
99
Issue
9
Year of publication
1993
Pages
6264 - 6277
Database
ISI
SICI code
0021-9606(1993)99:9<6264:RTFCCT>2.0.ZU;2-7
Abstract
A quantum mechanical relaxation theory is developed to enable approxim ate computation o electronic absorption line shapes of condensed phase systems where nonadiabatic coupling effects are important. At the sim plest level, these computations require a time kernel (termed a memory kernel) which can be obtained from a sequence of wave packet propagat ions, each carried out on a single Born-Oppenheimer potential surface. Complications associated with the need to evolve wave packets on seve ral nonadiabatically coupled surfaces are thereby avoided. Moreover, f or many condensed phase problems the memory kernel can be computed via semiclassical techniques which rely on classical trajectories and sim ple Monte Carlo methods. The promise of the theory is demonstrated by numerical applications to the spectroscopic spin boson model [R. D. Co alson, J. Chem. Phys. 86, 995 (1987)], a nontrivial multimode model of electronic absorption lineshapes involving two nonadiabatically coupl ed excited state surfaces. The relevant quantum dynamics for the spect roscopic spin boson model can be computed exactly via path integration techniques. In this way, the accuracy of the proposed relaxation theo ry can be benchmarked, and the applicability of various semiclassical prescriptions for computing the memory kernel ascertained.