Authors: Zanchet, Alexandre; Garcia, Gustavo A.; Nahon, Laurent; Banares, Luis; Poullain, Sonia Marggi
Journal: PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Publication date: 2020/06/21
Abstract: The valence-shell photoionization of formaldehyde is investigated by means of combining Photo-Electron Photo-Ion COincidence (PEPICO) experiments and ab initio calculations. The formation of three ion fragments: HCO+, CO+ and H-2(+), via dissociative photoionization following excitation at 17 eV is discussed. The experimental results consisting of electron-ion kinetic energy correlation diagrams for the corresponding coincident events, i.e. (HCO+, e(-)), (CO+, e(-)) and (H-2(+), e(-)), as well as the fragment abundance as a function of the binding energy, are complemented by high level electronic structure calculations including potential energy curves and on-the-fly trajectories. The results are consistent with a main relaxation process via internal conversion into rovibrationally excited levels of the H2CO+ ground state, followed by statistical dissociation, preferentially into HCO+. The analysis of the experimental results reveals nevertheless the signature of a conical intersection controlling the dynamics and favoring dissociation into the molecular channel, CO+ + H-2. In addition, the minor formation of the H-2(+) ion is suggested to occur through a roaming pathway on the cation excited state.