DIRECT DYNAMICS SIMULATION OF THE LIFETIME OF TRIMETHYLENE

A direct trajectory method was employed to investigate the intramolecu lar dynamics and unimolecular decay of the trimethylene biradical over a range of energies. This method proved to be computationally viable when the internuclear forces were determined by semiempirical molecula r orbital theory. The trimethylene decay is double exponential at low energies, but becomes single exponential with a statistical rate const ant as the energy is increased. The non-statistical behavior at low en ergies arises from incomplete intramolecular vibrational energy redist ribution (IVR). The simulated results are in good agreement with the a vailable experimental data.