School of Chemistry, Bristol University, Bristol BS8 1TS, UK
Abstract:
Ab initio valence-bond calculations have been performed on the low-lying states of H2O+, with special attention being focused on the 2B2 state of the ion. The calculated potential energy surface for the 2B2 state is in qualitative agreement with several previously published molecular orbital calculations in predicting an equilibrium angle of about 60°. This prediction is, however, inconsistent with the most recent interpretation of the high-resolution photoelectron spectrum of H2O. Examination of the potential energy surfaces for geometries which have been distorted from C2v symmetry indicates that the 2B2 and Ã2A1 states are strongly coupled by the asymmetric stretching motion of the molecular ion. The presence of such a coupling supports the interpretation of the H2O photoelectron spectrum which invokes excitation of the asymmetric stretching vibration of the ion.