Channeling Revisited

The relation between classical and quantum mechanics was a central issue in Lindhard's theory of channeling. While ion channeling can be described by classical mechanics, there are strong quantal features for positrons and electrons. At high energy the description becomes classical also for these particles, and the transition provides an illustration of the correspondence between quantum and classical mechanics in the limit of large quantum numbers. With the discovery of channeling radiation in the late 70'ies, electron channeling gained new interest. Applications to the observation of solid-state properties were demonstrated, and electron channeling may provide interesting sources of hard photons.