STIMULATED-EMISSION PUMPING SPECTROSCOPY OF CH3O (X)OVER-TILDE2E, NU-6) - NEW OBSERVATIONS ON THE JAHN-TELLER EFFECT

Experiments have been carried out using hot ban laser induced fluorescence (LIF) excitation and stimulated emission pumping (SEP) spectroscopy to characterize the excited doubly degenerate nu6 vibrational mode of CH3O (X2E) which is of interest with respect to the Jahn-Teller effect in the molecule. Rotationally resolved spectra were recorded for the A2 A1 <-> X2E, 6(1)0 and 3(1)0(6)1(0) bands. The observed line structures indicate that these bands must be assigned to DELTAj=3/2 parallel (DELTAK=0) vibronic bands. No evidence could yet be obtained for the corresponding DELTAj=1/2 vibronic transitions assumed previously. The results imply that the linear Jahn-Teller effect for nu6 is very small. Instead, coupling between the A2A1 and the X2E states by a pseudo-Jahn-Teller interaction operator is suggested as a plausible mechanism for the observation of the forbidden transitions.