Excited state dynamics of H2CN radicals

The photodissociation of H2CN radicals at 274–288 nm was studied using high-n Rydberg H-atom photofragment translational energy spectroscopy. A slight preference for H-atom scattering perpendicular to the laser polarization axis (β=−0.10±0.03) indicates that the near-UV transition corresponds to a "forbidden" 2B1←2B2 electronic transition made weakly allowed for excitation to A2 vibronic levels. Of the total excess energy (≈77 kcal/mol), on average approximately 65% appears as HCN internal excitation. Dissociation proceeds via an indirect mechanism likely involving the ground electronic state.