Non-statistical effects in bond fission reactions of 1,2-difluoroethane

• Published in: Chemical physics letters 1991-08, Vol.182 (5), p.455-462
• Main Authors: Schranz, Harold W., Raff, Lionel M., Thompson, Donald L.
• Format: Article
• Language: English
• Subjects: Atomic and molecular collision processes and interactions; Atomic and molecular physics; Exact sciences and technology; Intramolecular energy transfer; intramolecular dynamics; dynamics of van der waals molecules; Physics
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/0009-2614(91)90107-K

A microcanonical, classical variational transition-state theory based on the use of the efficient microcanonical sampling (EMS) procedure is applied to simple bond fission in 1,2-difluoroethane. Comparison is made with results of trajectory calculations performed on the same global potential-energy surface. Agreement between the statistical theory and trajectory results for CC CF and CH bond fissions is poor with differences as large as a factor of 125. Most importantly, at the lower energy studied, 6.0 eV, the statistical calculations predict considerably slower rates than those computed from trajectories. We conclude from these results that the statistical assumptions inherent in the transition-state theory method are not valid for 1,2-difluoroethane in spite of the fact that the total intramolecular energy transfer rate out of CH and CC normal and local modes is large relative to the bond fission rates. The IVR rate is not globally rapid and the trajectories do not access all of the energetically available phase space uniformly on the timescale of the reactions.