On the role of conical intersections of two potential energy surfaces of the same symmetry in photodissociation. I. CH3SH→CH3S+H and CH3+SH

Recent experimental/theoretical studies have demonstrated efficient photodissociation of CH3SH to CH3S+H and to CH3+SH. Avoided crossings have been implicated in the photodissociation process. This work demonstrates the existence of a surface of conical intersections of two states of the same symmetry relevant to the photodissociation offering new insights into the mechanism of the decomposition process. Using wave functions comprised of greater than 1.3 million configuration state functions convincing evidence is provided that the surface of conical intersections is a property of the system rather the particular expansion employed in this work. The conical intersections are determined directly, that is without prior determination of the potential energy surfaces in question.