Sign reversal of the spin-orbit constant for the C³Πᵤ state of N₂

Abstract

Ab initio calculations are performed at the multireference configuration-interaction level of theory on the diagonal spin-orbit functions for the lowest non-Rydberg states of ³Πᵤ symmetry in molecular nitrogen. Spin-orbit constants deduced from the ab initio results confirm the recent suggestion, based on new experimental results, that the C³Πᵤ state of N₂, long known to be regular in the region of its potential-energy curve minimum, becomes inverted at higher energies. By removing the effects of the crossing C′ ³Πᵤ state, it is shown that Av for the C state changes sign from positive to negative near v=8, corresponding to a change in principal molecular-orbital configuration from (1σg)²(1σu)²(2σg)²(2σu)(3σg)²(1πu)⁴(1πg) to (1σg)²(1σu)²(2σg)²(2σu)²(3σg)(1πu)³(1πg)² at an internuclear distance near 1.4 Å.This work was supported by the Australian Research Council Discovery Program under Grant Nos. DP0558962 and DP0773050