Anisotropic photodissociation of vinyl chloride molecular cation in the ground and first excited electronic states

Photodissociation of the vinyl chloride molecular ion generated by charge exchange or electron impact ionization has been investigated using mass-analyzed ion kinetic energy spectrometry (MIKES). The MIKE spectra for the Cl and HCl losses from the vinyl chloride ion have been measured at 357, 488.0, and 514.5nm using 0 and 90° laser polarization angles. The anisotropy parameters and kinetic energy release distributions have been determined. The vinyl chloride ion in the ground state did not undergo photodissociation in the visible spectral region while the same ion generated by more energetic means displayed fairly strong photodissociation. Presence of the vinyl chloride ion in the very long-lived first excited electronic state reported previously is compatible with this observation. In addition, isotropic dissociation to C₂H₂^•+ occurring in the ground electronic state was observed. Results from the photoelectron spectroscopy and quantum chemical calculations at the TDDFT/UB3LYP/6-311++G** level were used to identify the reaction pathways involved.