Hyperfine-frequency shifts of alkali-metal atoms during long-range collisions

TL;DR

This paper provides an improved estimate of the long-range hyperfine-frequency shifts in alkali-metal atoms during collisions, which are crucial for understanding pressure shifts, spin interactions, and ultracold molecule formation.

Contribution

The paper introduces a refined calculation of the asymptotic hyperfine-shift interaction for Na, K, Rb, and Cs atoms, and tests it against electric field effects.

Findings

Improved long-range hyperfine shift estimates for alkali metals.

Reasonable agreement with hyperfine change under static electric fields.

Implications for ultracold molecule magnetoassociation.

Abstract

Collisions with chemically inert atoms or molecules change the hyperfine coupling of an alkali-metal atom through the hyperfine-shift interaction. This interaction is responsible for the pressure shifts of the microwave resonances of alkali-metal atoms in buffer gases, is an important spin interaction in alkali-metal--noble-gas van der Waals molecules, and is anticipated to enable the magnetoassociation of ultracold molecules such as RbSr. An improved estimate is presented for the long-range asymptote of this interaction for Na, K, Rb, and Cs. To test the results, the change in hyperfine coupling due to a static electric field is estimated and reasonable agreement is found.