Collisional Energy Transfer; New Light on an Old Problem

Abstract

Energy transfer collisions in molecules play a central role in many areas of chemistry and physics and the detailed understanding of these relatively simple interactions could lead to greater insight into the more complex processes that involve bond breaking and making. However, it would be wrong to suppose that our level of understanding of the simplest (molecular) collision process is satisfactory. The contrast to photon-induced quantum state changes, is stark. Here it is possible to predict energy levels and transition probabilities with high precision once some relatively basic information on the molecule is established. In collisionally induced quantum state changes, no such predictability is available. Theory is not sufficiently transparent that even simple ‘rules of thumb’ concerning energy transfer may be extracted. This unsatisfactory state of affairs may not be inherent in the collisional problem and may be more a function of our chosen way of addressing the issue.