Accurate spectroscopic calculations of the 12 Λ-S states and 27 Ω states of NF+ cation including the spin–orbit coupling effect

Abstract

This paper studies the potential energy curves (PECs) of 27 Ω states generated from the 12 Λ-S states (X2Π, 12Σ+, 12Σ−, 22Σ−, A2Π, 12Δ, 14Σ+, 14Σ−, 24Σ−, 14Π, 24Π and 14Δ), which are attributed to the first dissociation channel of NF+ cation. Of these 12 states, only 22Σ− and 24Π are the repulsive ones, which are very different from those reported by G.-S. Kim and D. M. Hirst, Mol. Phys. 86, 1183–1193 (1995). In addition, the 12Δ and 14Σ− states are found to possess the double well. 14Σ+, 14Σ− and 14Δ are found to be the inverted states with the spin–orbit coupling effect taken into account, and 12Σ+, 12Σ−, 12Δ, 14Σ+, 24Σ− and 14Δ are found to be the weakly bound states. The PECs are calculated by the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with Davidson correction. The convergent behaviour of the present calculations is discussed with respect to the basis set and level of theory. All the PECs are extrapolated to the complete basis set limit. Core–valence correlation and scalar relativistic corrections are included at the same time. The spin–orbit coupling effect is accounted for by the state interaction method with the Breit–Pauli Hamiltonian. The spectroscopic parameters are evaluated and compared with available measurements and other theoretical results. The effect of spin–orbit coupling on the spectroscopic parameters is discussed. The Franck–Condon factors and radiative lifetimes of the transitions from the 14Π3/2, 14Σ−3/2, 12Δ3/2 and A2Π1/2 states to the X2Π1/2 state are calculated for several low vibrational levels and some necessary discussion is done. It shows that the spectroscopic results reported in this paper can be expected to be reliably predicted ones.