Experimental and theoretical study of the photodissociation reaction of thiophenol at 243 nm: Intramolecular orbital alignment of the phenylthiyl radical

The photoinduced hydrogen (or deuterium) detachment reaction of thiophenol (C6H5SH) or thiophenol-d1 (C6H5SD) pumped at 243nm has been investigated using the H (D) ion velocity map imaging technique. Photodissociation products, corresponding to the two distinct and anisotropic rings observed in the H (or D) ion images, are identified as the two lowest electronic states of phenylthiyl radical (C6H5S∙). Ab initio calculations show that the singly occupied molecular orbital of the phenylthiyl radical is localized on the sulfur atom and it is oriented either perpendicular or parallel to the molecular plane for the ground (B1) and the first excited state (B2) species, respectively. The experimental energy separation between these two states is 2600±200cm−1 in excellent agreement with the authors’ theoretical prediction of 2674cm−1 at the CASPT2 level. The experimental anisotropy parameter (β) of −1.0±0.05 at the large translational energy of D from the C6H5SD dissociation indicates that the transition dipole m...