Dissociative Recombination of H3O+

Abstract

Ab initio molecular orbital calculations have been performed on potential energy surfaces associated with products of dissociative recombination (DR) of H3O+ + e- experiments carried out in the ASTRID heavy-ion storage ring. Gradient geometry optimizations and frequency calculations on critical points on the H3O ground-electronic-state surface and its dissociation paths were performed at levels of theory up to and including MP2(full)/6-311G(d,p) with extra diffuse functions added to the oxygen atom; single-point calculations subsequently were performed at levels up to CCSD(T) with the same basis set. Dissociation pathways of the two lowest-energy valence-to-Rydberg H3O excited states were studied using CIS single-point calculations on SCF-level optimized geometries along ground-state H3O dissociation pathways, and no barriers to fragmentation were observed. The most exothermic ground-state dissociation pathway connects H3O to H2O (X1A1) + H; however, OH(X2Π) + H2 and OH(X2Π) + 2H also are energetically ac...