Vibronic Interaction in Molecules and Ions. II. The first order Jahn-Teller interaction and spin-orbit coupling in doubly degenerate electronic states of C3v type molecules

Abstract

A quantitative treatment invoking first-order Jahn-Teller interaction together with spin-orbit coupling is employed to determine the energy levels of 2E electronic states of C3v type molecules. Both the static and dynamic nature of the interactions are discussed. The vibronic energies as well as vibrational transition probabilities of 1A1→2E transitions are presented from two sets of calculations corresponding to different magnitudes of the spin-orbit coupling. An application is made to explain the vibronic structure of the 2e electron band of the high resolution electron spectra of CH3Cl, CH3Br and CH3I. The magnitude of the vibronic coupling is determined in terms of a Jahn-Teller coupling parameter. The result for CH3Cl+ suggests that the spin-orbit splitting is quenched and the geometry of the ground ionic state is distorted to Cs or C1 symmetry.