Polarization CI wavefunctions: the valence states of the NH radical

Abstract

The polarization configuration interaction (POL–CI) wavefunction is described. Calculations are reported for the X 3Σ−, a 1Δ, b 1Σ+, A 3Π, and c 1Π states of the NH molecules in a double zeta plus polarization Gaussian basis. Calculated excitation energies and spectroscopic constants are compared with results from more extensive calculations in this basis and with previously reported calculations. The starting point for POL–CI calculations is a generalized valence bond (GVB) calculation to insure proper dissociation. Results of using both ground state and excited state GVB orbitals show that a single set of (ground state) orbitals may be used for all states without loss of accuracy. Dipole moments and electronic transition moments as a function of R are also given.