Photodissociation dynamics of the phenyl radical via photofragment translational spectroscopy.

Photofragment translational spectroscopy was used to study the photodissociation dynamics of the phenyl radical C6H5 at 248 and 193 nm. At 248 nm, the only dissociation products observed were from H atom loss, attributed primarily to H+o-C6H4 (ortho-benzyne). The observed translational energy distribution was consistent with statistical decay on the ground state surface. At 193 nm, dissociation to H+C6H4 and C4H3+C2H2 was observed. The C6H4 fragment can be either o-C6H4 or l-C6H4 resulting from decyclization of the phenyl ring. The C4H3+C2H2 products dominate over the two H loss channels. Attempts to reproduce the observed branching ratio by assuming ground state dynamics were unsuccessful. However, these calculations assumed that the C4H3 fragment was n-C4H3, and better agreement would be expected if the lower energy i-C4H3+C2H2 channel were included. [ABSTRACT FROM AUTHOR]