Dissociation of energy-selected CH3CN+ in a region 15.1–16.5 eV: Vibrationally enhanced dissociation and mechanisms

Threshold photoelectron–photoion coincidence spectra of CH3CN were measured in a region 15.1–16.5 eV. We observed a small vibrational enhancement on dissociation of CH3CN+ and obtained kinetic energy releases for channels C2HN+ + H2 and CH 2 + + HCN . The kinetic energies released in channel C2HN+ + H2 are substantial; a linearly extrapolated dissociation threshold of 14.68 ± 0.01 eV agrees with a Gaussian-3 B3LYP prediction 14.70 eV for formation of HCCN+ + H2. In contrast, the small releases for channel CH 2 + + HCN agree with a statistical calculation. We describe a plausible dissociation mechanism with the Gaussian-3 B3LYP method to rationalize experimental results.