Three-Body Collision Based Recombination Rate Constants from Quasi Classical Trajectory Calculations

摘要

We present gas phase recombination rate constants computed using Quasi Classical Trajectory (QCT) data without a direct appeal to detailed balance. The recombination rate constant is the product of a triple collision rate and a probability of recombination from triple collisions. We evaluate the triple collision rate as a binary collision rate between colliding pairs and third particles using the lifetimes of colliding pairs from QCT simulations. The lifetimes of O + O_2 collisions are shown to be much longer than for O + O pairs because the O_2 internal modes absorb translational energy and trap the particles in their interaction potential. The recombination probabilities are calculated from three body QCT simulations where, per collision, recombination from O + O + O collisions is shown to be more likely than recombination from O + O + O_2 collisions by a factor of ≈ 2. Even so, calculated recombination rate constants are shown to be dominated by O + O + O_2 collisions because the triple collision rate involving O + O_2 pairs is « 10 times larger.