The kinetics of the H2 (D2) loss from C2H4+ (C2D4+) ions

The unimolecular H2/D2 loss from C2H4+/C2D4+ ions has been investigated in a threshold photoelectron photoion coincidence spectrometer with electron time of flight discrimination. The experiment shows that the reaction takes place on the microsecond timescale, i.e. is metastable right at the threshold. The experimental breakdown curve for d4-ethene is shifted by 103 meV to a higher excitation energy compared to h4-ethene. The entire breakdown curves were simulated based on model k(E) curves. Best agreement between experiment and simulation was observed for threshold values of k(E0)=7.0×105 s-1 for h4-ethene and k(E0)=2.5×104 s-1 for d4-ethene.