Interatomic collisions in a tightly confined Bose gas - art. no. 012706

We discuss binary atomic collisions in a Bose gas tightly confined in one ( axial) direction and identify two regimes of scattering. In the quasi-two-d imensional (quasi-2D) regime, where the confinement frequency omega (0) gre atly exceeds the gas temperature T, the scattering rates exhibit 2D feature s of the particle motion. At temperatures T similar to(h) over bar omega (0 ) one has a confinement-dominated 3D regime, where the confinement can chan ge the momentum dependence of the scattering amplitudes. We describe the co llision-induced energy exchange between the axial and radial degrees of fre edom and analyze recent experiments on thermalization and spin-relaxation r ates in a tightly (axially) confined gas of Cs atoms.