Conical intersection dynamics in the photodissociation of thioanisoles

초록

Conical intersection plays a key role in the nonadiabatic transition, which is ubiquitous in excited-state reaction dynamics. Here, we report the case of the photodissociation of thioanisoles. Upon UV excitation, this molecule produces the methyl and thiophenyl radicals as products. Since ground and first excited states of the latter are both energetically accessible, the branching ratio between these two states could be determined from the kinetic energy distribution of the nascent methyl radical product. It is found that this branching ratio is strongly dependent on the vibronic quantum nature of the initially prepared reactant state whereas the nonadiabatic transition responsible for the energy-dependent branching ratio is dertermined at the conical intersection, which is located far from the initial nuclear configuration. The extent of the kinetic energy release, which is one of the key dynamic observables, changes also in accord with the change of the branching ratio, reflecting dynamic role of the initial quantum state on the product output in terms of the nonadiabatic transition probability. We discuss the dynamics in detail with the aid of ab initio calcuations.