An experimental study of the spin-exchange frequency shift in a laser-cooled cesium fountain frequency standard
LPTF/BNM - 61 Avenue de l'Observatoire, Paris 75014, France
2 NPL - Teddington, Middlesex TW11 0LW, UK
Accepted: 14 August 1996
The spin-exchange frequency shift due to cold collisions between ground-state atoms appears to be the systematic effect which could limit the accuracy of a laser-cooled cesium fountain operating as a frequency standard. We have investigated this shift for atoms distributed among all the Zeeman substates of either the F=4 or F=3 hyperfine level of the ground state of cesium and for the case where most of the atoms are prepared in F=3, MF=0 sublevel. The measured relative frequency shifts are respectively , and . These results agree with the measurements performed by Gibble and Chu at higher atom densities with atoms prepared in F=3, MF=0 sublevel. However, the precision of our frequency measurements is much better and is only limited at by the H-maser used as a reference oscillator. Finally, we show that the relative frequency shift due to cold collisions can be reduced to 10-15, while preserving a short-term frequency stability of about .
PACS: 32.80.Pj – Optical cooling of atoms; trapping / 34.90.+q – Other topics in atomic and molecular collision processes and interactions / 42.50.Vk – Mechanical effects of light on atoms, molecules, electrons, and ions
© EDP Sciences, 1996