Weak collision effects: Non‐steady‐state thermal unimolecular reactions

Bench‐mark calculations for non‐steady‐state thermal systems are presented. Although the equations and calculations were modeled for the isomerization of cyclopropane in the single‐pulse shock tube, the results are qualitatively and semiquantitatively correct for any experimental technique in which a finite time is required to energize the reactant to the reaction temperature. A useful parameter in describing this nonequilibrium behavior is the induction time τ 95 ; the log of τ 95 is linearly related to the collision frequency ω. For the model cyclopropane system a steady state is reached in ∼1 msec when ω ≈ 10 8 sec −1 and T ≈ 1500 K.