Rovibronic analysis of the Jahn-Teller effect in CH2D2+ at low energies

Abstract

The Jahn-Teller effect in the ground state of CH2 D2+ has been studied by pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy. The lowest three bands have been assigned to the three isomers CH H Ds Ds+, CH Hs D Ds+, and CH s Hs D D+, in which the deuterium atoms are attached to the central carbon atom by two short bonds, one short and one long bond, and two long bonds, respectively, and which have different zero-point vibrational energies. Whereas CH H Ds Ds+ and CH s Hs D D+ can each be described by a single structure with C2v symmetry, CH Hs D Ds+ corresponds to four equivalent C1 structures that interconvert by tunneling. The rotational structure of these three bands is compared with predictions made on the basis of a tunneling Hamiltonian combined with a rotational Hamiltonian that incorporates the effects of the large-amplitude tunneling motion. The zero-point energies of CH HS D Ds+ and CHs Hs D D+ relative to that of CH H Ds D s+ are Δ=123.6 (5) cm-1 and Δ′ =243.2 (5) cm-1, respectively, and the tunneling matrix element σ coupling the four C2v equilibrium structures of CH Hs D Ds+ is -1.7 (4) cm-1. © 2009 American Institute of Physics.