Ab initio investigation of the vibronic structure in the C<inf>2</inf>H spectrum: Spin-orbit splitting of the vibronic levels

Abstract

An ab initio study of the simultaneous vibronic and spin-orbit coupling in the X2Σ+-A2Π system of the ethynyl radical is reported. The value for the spin-orbit constant in the 2Π electronic state, calculated at its equilibrium geometry, is {reversed tilde equals}25 cm-1. The difficulties in calculating the spin-orbit splittings for the vibronic levels which are strongly shared between different potential energy surfaces is discussed. © 1991.