CH4+: a fluxional ion?

High resolution pulsed-field-ionization (PFI) zero-kinetic-energy (ZEKE) ph otoelectron spectra of CH4 and its isotopomers have been recorded for the f irst time. These spectra show extensive progressions of rotationally resolv ed transitions. The vibrational structure of the Jahn-Teller distorted ions at low excitation energies have been analysed in terms of a one-dimensiona l model for the pseudorotational motion of the ions. The analysis of the ro tational structure confirms a fluxional behavior for CH4+, whereas CD2H2+ i n its vibronic ground state can be treated as a rigid rotor. (C) 2000 Elsev ier Science B.V. All rights reserved.