The calculation and interpretation of average collisional energy transfer parameters

It is pointed out that the proper comparison to make between theoretical and experimental results on collisional energy transfer in highly excited molecules involves the rate of energy transfer (or its moments) rather than the average energy transfer per collision. This rate can be computed from trajectory studies without the need to define a "collision" or to omit arbitrary defined elastic trajectories. Illustrative calculations for CH3CH2Cl/Ne collisions are presented.