Ab initio calculations of the vibronically averaged hyperflne coupling constants in the 1²∏<inf>u</inf>(X²b<inf>1</inf>, a²a<inf>1</inf>) state of the water cation

Abstract

The hyperfine coupling constants (hfcc’s) Aiso and, Aij are calculated for all centres of H2O+ in its two lowest lying electronic states (X2B1, A2A1) at various molecular geometries by means of the ab initio multireference configuration method. The vibronically averaged values of the hfcc’s for the K = 0 and K= 1 levels in H172O in the energy range up to 25000cm-1 are computed. The study shows that the reliable hfcc’s of higher vibronic states can only be obtained if the vibronic coupling between the two electronic states is taken into account, while the lowest vibronic states of the X2B1 are nearly unaffected by the nuclear motion. Comparisons to the isoelectronic system NH2 are made. © 1993 Taylor & Francis Ltd.