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

Understand

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.