Stimulated emission pumping spectroscopy of CH3O (<i>X</i> 2<i>E</i>, ν6): New observations on the Jahn–Teller effect

Abstract

Experiments have been carried out using hot band laser induced fluorescence (LIF) excitation and stimulated emission pumping (SEP) spectroscopy to characterize the excited doubly degenerate ν6 vibrational mode of CH3O (X̃ 2E) which is of interest with respect to the Jahn–Teller effect in the molecule. Rotationally resolved spectra were recorded for the à 2A1↔X̃ 2E, 610 and 310610 bands. The observed line structures indicate that these bands must be assigned to Δj=3/2 parallel (ΔK=0) vibronic bands. No evidence could yet be obtained for the corresponding Δj=1/2 vibronic transitions assumed previously. The results imply that the linear Jahn–Teller effect for ν6 is very small. Instead, coupling between the à 2A1 and the X̃ 2E states by a pseudo-Jahn–Teller interaction operator is suggested as a plausible mechanism for the observation of the forbidden transitions.