Theoretical study of the Jahn–Teller effect in X̃ 2E CH3O

The Jahn–Teller effect in X 2E CH3O is theoretically investigated in considerable detail. Making use of ab initio calculations carried out at the MRC-level we present the global shape of the adiabatic potential surfaces. Both sheets of the Jahn–Teller split X 2E electronic state are used to determine the linear, quadratic and bilinear coupling constants of the e and a1 modes, as well as selected third-order constants. Dynamical calculations for the vibronic structure have been performed with these parameters. The dynamical Jahn–Teller problem is solved by taking into account all the three e modes or, alternatively, two e modes and two a1 modes. The resulting vibronic spectra are compared with those of previous work. Furthermore, ab initio calculated transition moments for A 2A1↔X 2E are used to give an explanation for the forbidden Δj=32 transitions which were found by different experimental groups.