Ab initio study of H photodetachment from the ethyl radical

Minimal energy pathways for hydrogen motion in excited electronic states of C2H5 have been studied at the CASSCF and MRCI levels. The calculations reveal that after photoexcitation to the 3s and 3p Rydberg states a proton from the CH3 fragment slides to the bridging position over the center of the CC bond. In 3s (22A′) the resulting configuration (12A1, C2v) is unstable and dissociates to H and C2H4 in the ground electronic states without barrier. All three 3p Rydberg states of C2H5 are stable relative to the H splitting, and a rapid proton exchange can occur before the dissociation.