Hyperfine frequencies of 87Rb and 133Cs atoms in Xe gas

TL;DR

This study investigates the nonlinear pressure dependence of hyperfine transition frequencies of 87Rb and 133Cs atoms in Xe gas, revealing discrepancies with existing theories and highlighting the role of spin-rotation interactions.

Contribution

It provides new experimental data on hyperfine frequency shifts in Xe gas and improves theoretical understanding by including spin-rotation interactions.

Findings

Nonlinear frequency shifts in Xe are opposite in sign to those in Ar and Kr.

Discrepancies with previous theory are largely resolved by considering spin-rotation interactions.

Shifts in He, Ne, and N2 gases are linear with pressure.

Abstract

The microwave resonant frequencies of ground-state 87Rb and 133Cs atoms in Xe buffer gas are shown to have a relatively large nonlinear dependence on the Xe pressure, presumably because of RbXe or CsXe van der Waals molecules. The nonlinear shifts for Xe are opposite in sign to the previously measured shifts for Ar and Kr, even though all three gases have negative linear shifts. The Xe data show striking discrepancies with the previous theory for nonlinear shifts. Most of this discrepancy is eliminated by accounting for the spin-rotation interaction in addition to the hyperfine-shift interaction in the molecules. To the limit of our experimental accuracy, the shifts of 87Rb and 133Cs in He, Ne, and N2 were linear with pressure.