Specific rigidity factors in simple unimolecular bond fission reactions

Abstract

Specific rate constants, k(E, J), and thermally averaged rate constants for simple unimolecular bond fission reactions and the corresponding combination reactions to a first approximation are represented by phase space theory (PST) which neglects the anisotropy of the potential-energy surface. A central quantity in this treatment is the number of open reaction channels, W(E, J), which in PST can be expressed in approximate analytical form. Accounting for the anisotropy of the potential introduces additional specific rigidity factors, f _rigid (E, J), being between zero and unity, which have to be multiplied by W(E, J) from PST. After thermal averaging, thermal rigidity factors, f _rigid (T), are obtained. This article shows examples of specific rigidity factors as derived from the statistical adiabatic channel model (SACM) for selected anisotropies of the potential.