Ultra-cold Collisions

Abstract

Laser-cooling techniques were developed in the early 1980s for a variety of reasons, such as high-resolution spectroscopy. During the development of the techniques to cool and trap atoms, it became apparent that collisions between cold atoms in optical traps was one of the limiting factors in the achievement of high density samples. Trap loss experiments revealed that the main loss mechanisms were caused by laser-induced collisions. Further cooling and compression could only be achieved by techniques not exploiting laser light, such as evaporative cooling in magnetic traps (see Chapter 12). Elastic collisions between atoms in the ground state are essential in that case for the rethermalization of the sample, whereas inelastic collisions lead to destruction of the sample. Knowledge about collision physics at these low energies is therefore essential for the development of high-density samples of atoms using either laser or evaporative cooling techniques.