An ab Initio Study of the NH2+ Absorption Spectrum

In a previous publication (1997. P. Jensen, J. Mol. Spectrosc. 181, 207-214), rotation-vibration energy levels for the electronic ground state X3B1 of the amidogen ion, NH2+, were predicted using the MORBID Hamiltonian and computer program with an ab initio potential energy surface. In the present paper we calculate a new ab initio potential energy surface for the X3B1 state, and we calculate ab initio the potential energy surfaces of the a1A1 and b1B1 excited singlet electronic states (which become degenerate as a 1Delta state at linearity). We use the multireference configuration interaction (MR-CI) level of theory with molecular orbital bases that are optimized separately for each state by complete-active-space SCF (CASSCF) calculations. For the X state we use the MORBID Hamiltonian and computer program to obtain the rotation-vibration energies. For the a and b excited singlet electronic states we calculate the rovibronic energy levels using the RENNER Hamiltonian and computer program. We also calculate ab initio the dipole moment surfaces for the X, a, and b electronic states, and the out-of-plane transition moment surface for the b <-- a electronic transition. We use this information to simulate absorption spectra within X3B1 and a1A1 state and of the b1B1 <-- a1A1 transition in order to aid in the search for them. Copyright 1997 Academic Press. Copyright 1997Academic Press