Scattering of Cold Atom Coherences by Hot Atoms: Frequency Shifts from Background Gas Collisions

TL;DR

This paper investigates how collisions between cold atoms and hot background gases cause frequency shifts in atomic clocks, finding these shifts are smaller than in room-temperature clocks and are influenced by van der Waals interactions.

Contribution

It demonstrates that cold-atom background-gas frequency shifts are significantly reduced and provides a method to estimate these shifts based on Ramsey fringe amplitude loss.

Findings

Frequency shifts are ~10 times smaller than in room-temperature clocks.

Van der Waals interactions contribute to the frequency shifts.

Loss of Ramsey fringe amplitude bounds the frequency shift.

Abstract

Frequency shifts from background gas collisions currently contribute significantly to the inaccuracy of atomic clocks. Because nearly all collisions with room-temperature background gases that transfer momentum eject the cold atoms from the clock, the interference between the scattered and unscattered waves in the forward direction dominates these frequency shifts. We show they are ~10 times smaller than in room-temperature clocks and that van der Waals interactions produce the cold-atom background-gas shift. General considerations allow the loss of Ramsey fringe amplitude to bound this frequency shift.