Dissociative photodetachment (DPD) of the molecular anion HOCO-is used to probe the potential energy surface for the OH+CO-->H+CO2 reaction. The HOCO- anion, formed by electron impact on an expansion of CH4+N2O+CO, is characterized for the first time in these experiments by photoelectron spectroscopy and photoelectron angular distribution measurements. Photodetachment of HOCO- is found to produce H+CO2+e(-) and OH+CO+e(-) products in addition to stable HOCO radicals. Ab initio calculations of the energetics and structure of HOCO-and HOCO are consistent with the experimental results and show that photodetachment to the ground electronic HOCO surface samples the vicinity of the HOCO well. The product translational energy distributions observed on the ground state surface are consistent with unimolecular decomposition out of the HOCO well. In addition, direct DPD to a repulsive excited state of HOCO, correlating to ground state OH+CO products is observed.