On the ultrashort lifetime of electronically excited thiophenol

Highlights: • The relaxation of thiophenol excited to the S₁ ππ^∗, S₂ πσ^∗ and S₃ ππ^∗ states is tracked. • Sub 100 fs lifetimes are measured at all the studied excitation wavelengths. • The S₁ ππ^∗/S₂ πσ^∗ coupling is already accessible at the origin of the former. • The S₂ πσ^∗ surface drives the relaxation of the system. The relaxation dynamics of thiophenol, excited from the onset of the S₁ (1¹ππ^∗) state absorption, to the more intense S₃ (2¹ππ^∗) state band (290–244 nm), has been studied by time resolved ion yield spectroscopy. Along the studied energy range, the reached excited states relax in less 100 fs. These results evidence that the photophysics is dominated by the non-adiabatic coupling between the initially excited S₁ and S₃¹ππ^∗ states, and the dissociative character ¹πσ^∗ state. Contrarily to phenol, the 1¹ππ^∗/¹πσ^∗ crossing is reached from the origin of the 1¹ππ^∗ state absorption, through a nearly barrierless pathway.