Theory of thermal unimolecular reactions at high pressures

A simplified version of a statistical adiabatic channel model for unimolecular simple bond fission and the reverse radical association reactions is presented. The pattern of threshold energies for individual channels is analyzed and expressed empirically. High pressure rate constants for thermal dissociation and recombination are given in explicit form and applied to practical examples. The present theory interpolates between rigid and loose activated complex theory in a simple way with an account for angular momentum couplings. The interpolation parameter is the ratio α/β of the Morse parameter β and the looseness parameter α.