On the formation of rotationally hot H₂⁺ by dissociation of CH₄²⁺ dications

Abstract

Dissociation of CH₄²⁺ into CH₂⁺ ion pairs results in formation of H₂⁺ ions possessing a degree of rotational excitation which is high enough to enable formation of several rotational resonance states. These resonances give rise to unimolecular dissociation into H⁺ + H^· fragments. Ion translational energy spectrometry has been applied to measure such dissociation spectra, and a number of rotational resonances are observed. Rotational resonances are not observed whenH₂⁺ ions are generated from H₂ precursors. Two models based upon ideas of impulsive energy release are investigated which attempt to correlate the centre-of-mass kinetic energy released upon dissociation of CH₄²⁺ with the observation of the rotational resonances. There is good accord between the experimental results and the prediction of our models.