An ab initio calculation of the rotation-vibration energies of singlet and triplet NH 2+ using the morbid Hamiltonian

Abstract

For the X̃ 3B 1, ã 1A 1 and b̃ 1B 1 electronic states of the NH 2 + molecular ion we have calculated ab initio points on the potential energy surfaces using a complete second-order configuration interaction calculation for the six valence electrons. For the X̃ and ã states the rotation-vibration energies were calculated from these surfaces using the MORBID Hamiltonian. For the X̃ state we obtain r e = 1.0338 Å, α e = 153.17°, and a barrier to linearity of only 209 cm −1. Our best estimate for the vibrational frequencies are ν 1 = 3118 cm −1, ν 2 = 918 cm −1 and ν 3 = 3363 cm −1. For the ã state we obtain r e = 1.0510 Å, α e = 108.37°, ν 1 = 3027 cm −1, ν 2 = 1289 cm −1, and ν 3 = 3111 cm −1.