On the ultrashort lifetime of electronically excited thiophenol.

The relaxation dynamics of thiophenol, excited from the onset of the S 1 (1 1 ππ ∗ ) state absorption, to the more intense S 3 (2 1 ππ ∗ ) 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 S 1 and S 3 1 ππ ∗ states, and the dissociative character 1 πσ ∗ state. Contrarily to phenol, the 1 1 ππ ∗ / 1 πσ ∗ crossing is reached from the origin of the 1 1 ππ ∗ state absorption, through a nearly barrierless pathway. [ABSTRACT FROM AUTHOR]