Measurement of the scalar third-order electric polarizability of the Cs ground state using CPT-spectroscopy in Ramsey geometry

Abstract

The AC Stark shift induced by blackbody radiation is a major source of systematic uncertainty in present-day cesium microwave frequency standards. The shift is parametrized in terms of a third-order electric polarizability $\hat{I}{\pm }_0^{(3)}$ that can be inferred from the static electric field displacement of the clock transition resonance. In this paper, we report on an all-optical CPT pump-probe experiment measuring the differential polarizability $\hat{I}”\hat{I}{\pm }_0^{(3)}=\hat{I}{\pm }_0^{(3)}(F=4)-\hat{I}{\pm }_0^{(3)}(F=3)$ on a thermal Cs atomic beam, from which we infer $\hat{I}{\pm }_0^{(3)}(F=4)=2.023(6{)}_{stat}(9{)}_{syst}Hz/(kV/cm{)}^2$, which corresponds to a scalar Stark shift parameter $k_s=-2.312(7{)}_{stat}(10{)}_{syst}Hz/(kV/cm{)}^2$. The result agrees within two standard deviations with a recent measurement in an atomic fountain, and rules out another recent result obtained in a Cs vapor cell.

15 pages, 16 figures