Tunneling Facilitated Dissociation to H+CO2 in HOCO- Photodetachment

Dissociative photodetachment of HOCO- is investigated with both five- and six-dimensional quantum models on an ab initio based accurate HOCO potential energy surface. Three experimentally observed channels, namely, HOCO, H + CO2, and HO + CO, are identified in our theoretical simulations. Since the energy spectrum of the initial HOCO species prepared by photodetachment is mostly lower than both the HO + CO asymptote and dissociation barrier to H + CO2, the production of H + CO2 is almost exclusively via tunneling. However, the lowest-lying HOCO resonances are extremely long lived (similar to mu s), which might elude experimental measurements through its decay products H + CO2. Our results are in good agreement with almost all experimental data reported by the Continetti group using a new cryogenically cooled photoelectron-photofragment coincidence apparatus.