Photolysis of tert-Butylthionitrite via Excitation to the S1 and S2 States Studied by 3d-REMPI Spectroscopy

S-Nitrosothiols serve as carriers and donors of NO in several important biological signaling systems. In these compounds the S−NO bond is rather labile and NO can be released thermally or photochemically. This paper reports on the photolytical decomposition of tert-butylthionitrite (t-BuSNO) in the visible and near-UV spectral regions. Between 500 and 605 nm several vibronic levels of the S1 (nπ*) state were excited, including the electronic origin. At 360 nm t-BuSNO is excited near the maximum of the first UV band assigned to the S2 (ππ*) state. The velocity distributions of several hundred rovibrational states of the NO fragments were recorded with the recently developed 3d-REMPI method. A global fit to these data yields populations of the rovibrational states in both spin−orbit components of the 2Π electronic state of NO as well as their velocity distributions and angular anisotropies β. These data also carry the distribution functions for internal and kinetic energy of the counterfragment, the t-BuS r...