Quasiperiodic trajectories in the unimolecular dissociation of ethyl radicals by time-frequency analysis

Direct classical trajectory calculations for ethyl radical, C2H5, at the HCTH147@6-31 +G**/6-31G** level of theory support the experimental observation that the dissociation of highly excited ethyl radicals to ethylene and and a hydrogen atom can occur much more slowly than predicted by statistical rate theories. Only 78% of the trajectories of ethyl radicals prepared in a microcanonical ensemble with 120-kcal/mol excitation energy above the zero-point energy and zero total angular momentum dissociate to form C2H4 + H. The remaining hot ground-state ethyl radicals have a lifetime of >2 ps, during which a time-frequency analysis finds them trapped for extended periods of time in long-lived quasiperiodic trajectories.