Excited electronic potential-energy surfaces and transition moments for the H3 system

Abstract

Four electronic states of H3 have been studied using a multiple-reference double-excitation configuration-interaction method with an extensive basis set of 75 Gaussian-type atomic orbitals. A total of 1340 ab initio points were calculated over a wide range of H3 molecular geometries. These four states include the ground state and the Rydberg 2s A12′ and 2pz A22″ states, as well as the state that in equilateral triangular geometry is related to the ground state by a conical intersection. Electric-dipole transition moments were also obtained between these states. The results show that the atomic and diatomic energetic asymptotes are accurately described. The barriers, wells, and energy differences also show good agreement compared to literature values, where available. The potential energies of the ground state and the 2pz A22″ Rydberg state display smooth and regular behavior and were fitted over the whole molecular geometries using a rotated Morse curve-cubic spline approach. The other two potential-energy surfaces reveal more complicated behaviors, such as avoided crossings, and will require a different fitting procedure to obtain global fitting. Finally, dynamical implications of these potential surfaces and electric-dipole transition moments are discussed.