# Threshold photoelectron-photoion coincidence study of the fragmentation of valence states of CH2F-CH3+

Weidong Zhou, Richard P Tuckett, DJ Collins, Raymond Chim

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We have carried out a comprehensive study of the decay dynamics of the valence electronic states of CH$$_2$$F–CH$$_3^+$$, by using threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy and a tunable vacuum ultraviolet synchrotron radiation source. Threshold photoelectron spectroscopy (TPES) has been recorded for the first time in the photon energy range of ~12–24 eV. Ion yield curves and breakdown diagrams have been determined in the energy range of ~ 11.5–18 eV. The dissociation process and fragmental mechanism of the valence states of the parent ion are discussed. The mean translational kinetic energy releases for fragmentation of CH$$_2$$F–CH$$_3^+$$, via a single bond cleavage have been measured and compared with the predictions of statistical and impulsive mechanisms. For dissociation CH$$_2$$F–CH$$_3^+$$ $$\rightarrow$$ CHF–CH$$_3^+$$ + H+e−, a non-statistical decay is assumed, and there seems to be a transition to statistical behaviour with increasing photon energy. For cleavage of the C–C bond to form CH$$_2$$F$$^+$$, there seems again to be a transition to statistical decay. The ionization threshold measured from the TPES and the appearance energies (AEs) identified from the ion yield curves are presented. An upper limit for the ionization threshold of CH$$_2$$F–CH$$_3$$ (11.66 ± 0.03 eV) and the enthalpy of formation of CH$$_2$$F–CH$$_3^+$$ at 298 K (679 ± 3 kJ mol$$^{−1}$$) are determined.