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Coupled equations approach to multiphoton molecular processes
Author(s) -
Bandrauk André D.,
Gélinas Nadia
Publication year - 1987
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540080407
Subject(s) - diatomic molecule , electronic structure , scattering , chemistry , atomic electron transition , radiative transfer , ab initio , molecule , raman scattering , quantum mechanics , coupled cluster , nonlinear system , physics , raman spectroscopy , spectral line
Using the dressed molecule picture of molecule radiation interactions (A.D. Bandrauk et al., J. Chem. Phys. , 79 , 3256; 80 , 4926; 83 , 2840) one can deduce multiphoton processes (absorption, scattering, nonlinear optical properties, etc.) amplitudes from coupled second‐order differential equations with electronic surfaces and transition moments as input data obtainable from quantum chemical calculations. The present approach enables one to include in the calculation bound and continuum states simultaneously by the use of appropriate boundary conditions for the numerical solutions of these coupled equations. In the case of weak radiative couplings, one recovers the usual Fermi‐Golden rule expressions for electronic absorption, raman scattering, etc. The method is thus quite general, bridging the weak field (traditional photochemistry) and the strong field (laser chemistry) regimes which are attainable with today's lasers. The numerical solutions of the coupled equations give us the stationary states of the molecule + radiation system, called dressed molecule. Preparation of the initial state can be mimicked in the coupled equations by an artificial channel method for processes involving a final‐state dissociation. Examples of such calculations will be presented in the diatomic Cl 2 for which several ab initio electronic states and transition moments were available.