Lifetime distribution of energized molecules in unimolecular reactions

Abstract

AbstractThe lifetime distribution of energized molecules is examined within the framework of classical description of the molecular dynamics and in the connection with model theories of unimolecular reactions. If the reacting molecule represents an ergodic system, the lifetime distribution function of the molecules represented immediately after activation by the points in the phase space region corresponding to the internal energy ϵ to ϵ + δϵ (RRKM model) may be introduced; in a non‐ergodic case, the distribution function may be defined in that part of this phase space region, the point of which satisfy a supplementary condition of decomposition (Slater's model). It is shown that allowing a rapid intramolecular redistribution of internal energy of the molecule in the originally harmonic model, we obtain lifetime densities approximating the exponential (random) density. Some general features of the lifetime distribution in an ensemble of molecules with a uniform phase space density after activation are deduced from the qualitative analysis of the phase space trajectories.