Collision-Induced Spin Depolarization of Alkali-metal Atoms in Cold \(^3\)He Gas

Abstract

We present a joint experimental and theoretical study of spin depolarization in collisions of alkali-metal atoms with \(^3\)He in a magnetic field. A rigorous quantum theory for spin-changing transitions is developed and applied to calculate the spin exchange and spin relaxation rates of Li and K atoms in cryogenic \(^3\)He gas. Magnetic trapping experiments provide upper bounds to the spin exchange rates for Li-\(^3\)He and K-\(^3\)He, which are in agreement with the present theory. Our calculations demonstrate that the alkali-metal atoms have extremely slow spin depolarization rates, suggesting a number of potential applications in precision spectroscopy and quantum optics.