THEORY OF THERMAL UNIMOLECULAR REACTIONS AT LOW-PRESSURES .3. SUPERPOSITION OF WEAK AND STRONG COLLISIONS

Biexponential models for collisional energy transfer are formulated representing superimposed weak and strong collisions. Analytical solutions of the master equation for low pressure thermal unimolecular reactions at steady state are derived for such models. Nonequilibrium populations of excited states as well as collision efficiencies beta(c) in the low pressure rate constant differ considerably from the corresponding quantities for simple exponential collision models. The results are analyzed in terms of general expressions of the collision efficiency beta(c) as a function of the average energy transfer quantities [DELTA-E] and [DELTA-E2].