Jahn-Teller effect and large-amplitude motion in [formula omitted] studied by high-resolution photoelectron spectroscopy of CH4

Abstract

This article presents the current status of the knowledge of the rovibronic energy-level structure of CH4+ obtained by high-resolution photoelectron spectroscopy. The results of previous investigations are summarized and extended by new results obtained by double-resonance experiments involving vacuum-ultraviolet and mid-infrared laser radiation. These experiments have led to assignments of the nuclear-spin symmetry of 303 rovibrational levels of CH4+ with up to 3575cm−1 of internal excitation. A two-dimensional model of the pseudorotational motion of CH4+ is also presented, with which the positions and vibronic symmetry of the low-lying vibronic levels of CH4+ can be predicted. The model maps the F⊗(f⊕e) Jahn-Teller problem for the e and f2 modes corresponding to the CH bending motion onto a sphere, including the effects of both linear and quadratic Jahn-Teller coupling terms. The pseudorotation eigenstates are obtained by solving the two-dimensional Schrödinger equation using a basis of spherical harmonics.