Ab initio study of the vibronic and spin-orbit coupling in the X ²Π<inf>u</inf> state of C<inf>2</inf>H<inf>2</inf>⁺

Abstract

A variational approach for treating the Renner-Teller effect in tetra-atomic molecules [Perić et al., Mol. Phys. 55, 1159 (1985)] is extended to account for the effect of spin-orbit coupling. The approach is applied to compute the spin-orbit splittings of the vibronic levels in the X 2Πu state of C2H2+. The bending potential curves employed in a previous study [Perić and Peyerimhoff, J. Chem. Phys. (in press)] are improved by carrying out ab initio calculations at a higher level of sophistication. The results of the computations enable a reliable interpretation of recent experimental findings [Pratt et al., J. Chem. Phys., 99, 66 (1993)]. © 1995 American Institute of Physics.