Experiments and theory in cold and ultracold collisions

The authors review progress in understanding the nature of atomic collision s occurring at temperatures ranging from the millidegrees Kelvin to the nan odegrees Kelvin regime. The review includes advances in experiments with at om beams, light traps, and purely magnetic traps. Semiclassical and fully q uantal theories are described and their appropriate applicability assessed. The review divides the subject into two principal categories: collisions i n the presence of one or more light fields and ground-state collisions in t he dark. [S0034-6861(99)00101-4].