Nonadiabatic Effect in Photodissociation Dynamics of Thiophenol via the ¹ππ* State

Nonadiabatic photodissociation dynamics of thiophenol (PhSH) and deuterated thiophenol (PhSD) via the ¹ππ* state was investigated by a reduced three-dimensional (3D) quantum model based on the associated 3D diabatic potential energy surfaces constructed at the explicitly correlated multireference configuration interaction (MRCI-F12) level with the cc-pVTZ-F12 basis. The lifetimes of the low-lying vibronic S₁ states for PhSH and PhSD were calculated using a low-storage filter diagonalization method and were in reasonably good agreement with the available experimental results. The nonadiabatic effect was further examined in the photodissociation process by comparing the results in diabatic and adiabatic models. It was found that the adiabatic lifetimes were about 2-4 times shorter than the exact ones in the diabatic model for both PhSH and PhSD. More importantly, the exact ground wave function including the geometric phase (GP) possessed a node along the C-C-S-H/C-C-S-D torsional coordinate, while the node was absent when GP was not included in the adiabatic model. The node structure of the wave function was a hallmark of GP, which sheds light on the nonadiabatic photodissociation dynamics facilitated by the conical intersections.