Ultraviolet photodissociation dynamics of HN3: the H+N3 channel

The H+N3(X̃ 2Πg) channel in the ultraviolet photodissociation of HN3 has been studied at 248.3 and 193.3 nm using the high-n Rydberg H-atom time-of-flight technique. In 248.3 nm photodissociation, center-of-mass translational energy distribution reveals a propensity toward product translation (〈ftrans〉=0.71) and N3 bending and symmetric stretching excitation. An anisotropic product angular distribution (β≈−0.8) indicates a perpendicular electronic transition and rapid dissociation on the excited-state surface. H–N bond energy is estimated: D0(H–N3)⩽88.7±0.5 kcal/mol. At 193.3 nm, 〈ftrans〉 is smaller and product angular distribution is energy-dependent, suggesting multiple dissociation pathways via different electronic states.