Theoretical study of the X2B1, A2A1, 2B2 valence-shell and the first πu23s-type doublet and quartet Rydberg states of NH2

The angular potential energy curves of the X2B1, A2A1, B2B2 valence-shell and 4Σg−, 2Σg− (22B1), 2Δg (22A1, 32B1), and 2Σg+ Rydberg states arising from πu2 3s configurations are calculated by configuration interaction techniques. The data obtained reproduce very satisfactorily all X2B1 and A2A1 characteristics deduced from experiments; they support the previous theoretical prediction of a small-angle 2B2 state but find a very low |Re′e′′|2 value for the 2B2–A2A1 transition. The 4Σg− as well as three of the above four doublet Rydberg multiplets are found to prefer linear (or nearly linear) geometry and larger NH separations (in the symmetric structure) than NH2 in its ground state. A relatively large electronic transition moment for combination with both X2B1 and A2A1 is calculated for the lowest Rydberg multiplet which lies roughly 5.3 eV above the A2A1 state, while the intensity of transitions of the higher 3s states is found to be considerably smaller. Finally it is pointed out that the former Rydberg transition fits in well with recent emission experiments in this wavelength region recently reported by Herzberg.