Classical Unimolecular Rate Theory. III. Effect of Initial Conditions on Lifetime Distributions

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Abstract
The distribution of lifetimes of classical anharmonic and harmonic triatomic molecules capable of dissociation is found to depend upon the distribution of initial conditions immediately after collisional activation. Two types of collisional‐activation mechanisms are treated: one in which the density of initial points in phase space depends only upon the energy (the random mechanism), and the second in which the vibrational energy of the molecule is initially entirely kinetic (the impulsive mechanism). The random mechanism leads to a roughly exponential distribution of lifetimes for both harmonic and anharmonic molecules, in agreement with earlier work. The impulsive mechanism leads to lifetime distributions showing very marked peaks and minima for the harmonic model; this effect is much smaller for the anharmonic model.