Collision-Induced Spin Exchange of Alkali-Metal Atoms With \(^3\)He: An Ab Initio Study

Abstract

We present a rigorous quantum study of spin-exchange transitions in collisions of the alkali-metal atoms with (^3)He in the presence of an external magnetic field. Using accurate ab initio interaction potentials, we obtain refined estimates for the Fermi contact interaction constants for complexes of Na, K, and Rb atoms with (^3)He. Ab initio calculations show that the Fermi contact interaction in Li-(^3)He varies more slowly with inter-nuclear distance than predicted by the atomic model [R. M. Herman, Phys. Rev. 37, A1062 (1965)]. The calculated spin-exchange rate constants for Na, K, and Rb atoms in a gas of (^3)He are in good agreement with experimental data. Our calculations demonstrate that at a temperature of 0.5 K, collision-induced spin exchange of the alkali-metal atoms occurs at a very slow rate of ~10(^−22) cm(^3)/s, suggesting potential applications in cryogenic cooling, precision spectroscopy, and quantum optics.