Fall-off shape and incubation times in weak-collision thermal unimolecular reactions

A new formula for the weak-collision unimolecular rate constant is readily interpretable in terms of bottleneck concepts. This formula is used to explore the correlation between variations in relaxation structure and fall-off shape in weak-collision thermal unimolecular reactions; some information is also presented relating to collision efficiency factors β c , and to incubation times.It is conjectured that randomisation failure is an important feature which causes near-Lindemann behaviour to occur in practical weak-collision thermal reactions.