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+CO(2), 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+CO(2), the production of H+CO(2) is almost exclusively via tunneling. However, the lowest-lying HOCO resonances are extremely long lived (~μs), which might elude experimental measurements through its decay products H+CO(2). 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.