Ab initio study on the photodissociation of CH3O and CH3S radicals : The effect of spin-orbit coupling

Abstract

The methoxy family CH3X (X = O, S) is a series of very interesting radicals from several perspectives [1]. They are important compounds in environmental and combustion chemistry, in astrophysics and atmospheric reactions. Numerous references to the practical importance of these radicals have been compiled [2]. Although the literature on CH3O and CH3S is quite extensive, the most germane works from the viewpoint of photodissociation dynamics are the spectroscopic [3] and theoretical investigations [1,4] of the electronic structure of methoxy. In the present work, new ab initio data have been calculated on the 2E, 2A1, 2A2, 4E, and 4A2 five electronic states of CH3O and CH3S that correlate with the asymptotes O(S)(3P) + CH3 and O(S)(1D) + CH3, including spin-orbit coupling for the first time. Potential energy surfaces for the above electronic states have been computed as a function of CO(CS) distance and OCH(SCH) angle under C3v symmetry, using multireference internally contracted single and double excitation configuration interaction method with the aug-cc-pCVQZ basis set. The possible photodissociation mechanisms of CH3O and CH3S are discussed in the light of these potentials.