Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Collisional Frequency Shifts in 133Cs Fountain Clocks



P J. Leo, Paul S. Julienne, F H. Mies, Carl J. Williams


We present a theoretical analysis of the pressure shift in Cs fountain clocks using the highly constrained binary collision model described by Leo et al. [Phys. Rev. Lett. xx, xx (2000)]. We predict a reversal in the pressure shift at temperatures near 0.08 K which could allow elimination of a large source of uncertainty in the Cs fountain clock. Our results show that s-waves dominate the collision process however as a consequence of the large scattering lengths in Cs the pressure shift is strongly temperature dependent and does not reach a constant Wigner-law value until temperatures are less than 0.1 nK.
Physical Review Letters
No. 17


cesium, clock shift, fountain clock, ultracold scattering


Leo, P. , Julienne, P. , Mies, F. and Williams, C. (2001), Collisional Frequency Shifts in <sup>133</sup>Cs Fountain Clocks, Physical Review Letters (Accessed December 9, 2023)
Created April 1, 2001, Updated February 17, 2017