Energy dependent photochemistry in the predissociation of V(OCO)+

Abstract
Photofragmentation of the V(OCO)+ molecular ion in the visible shows sharp resonant absorption features and two distinct dissociation pathways: V+(OCO)+→V++CO2 and V(OCO)+→VO++CO. The photodissociation excitation spectrum reveals two low frequency vibrational modes in the upper state of this molecule at 105 and 196 cm−1. This spectrum indicates that the same photoexcited state in V(OCO)+ is the precursor to both V+ and VO+ products. The branching ratio for VO+/V+ production depends on the excitation energy and upper state vibrational mode. An estimate of the barrier to the production of VO+ of 13 000 cm−1 (37 kcal/mole) above the ground state of V(OCO)+ is made from this data.