Ab initio investigation of the ··· π<inf>g</inf>² (Χ³Σ<inf>g</inf>⁻, 1¹Δ<inf>g</inf>, 1¹Σ<inf>g</inf>⁺) electronic states of ncn study of the renner-teller effect in the 1¹Δ<inf>g</inf> state

Abstract

Large-scale CI calculations are carried out to obtain accurate potential energy surfaces for the ··· πg2 manifold (Χ3Σg−, 11Δg, 11Σg+) of electronic states of NCN. Separation of the low-lying singlet states from the triplet ground state is computed in close agreement with the results of a recent photoelectron study by T. R. Taylor, R. T. Bise, K. R. Asmis, and D. M. Neumark [Chem. Phys. Lett. 301, 413-416 (1999)]. Vibronic coupling (Renner-Teller effect) in the 11Δg state is studied by means of a perturbative and a variational approach. Results of the present ab initio study confirm explicitly the ρ4 dependence postulated for the splitting of bending potential curves in Δ electronic states at small deviations from linearity. © 2000 Academic Press.