Since the beginning of the twentieth century, many experimental and theoretical works have been devoted to collisions between highly charged ions and atomic and molecular targets. It was realized that quantum mechanics is the only way, a priori, to describe such atomic phenomena. However, since quantum mechanics is very difficult to apply for collision systems with more than two particles, classical methods were very soon introduced and applied to simple collision systems and, subsequently, to more complicated systems. The results obtained by such classical methods were found to be surprisingly good, and classical mechanics is now well established, despite its approximations, as a replacement for or competition with quantum mechanics in many cases.

François Frémont is teacher at Caen University and researcher in atomic collisions. He spent 20 years in experiment at GANIL (Caen), using accelerator at low energies to get evidence for electron correlation and to understand the role of electron capture in ion molecule collisions, and 10 years in theoretical calculations to demonstrate the ability of classical mechanics to solve many-body problems.