title: Stark shift of the Cs clock transition frequency: a new experimental approach.
abstract: The blackbody radiation shift, a manifestation of the Stark effect caused by blackbody radiation, contributes to the systematic uncertainty in Cs-based frequency standards at a level of 1 x 10(-15). Few measurements of the third-order scalar electric polarizability of the Cs ground states, mainly responsible for the ac Stark shift in atomic clocks, have given better than 10% accuracy. We report progress in the development of a fully optical Ramsey pump-probe measurement in a thermal atomic beam, based on coherent population trapping (CPT), for the measurement of the third-order scalar and tensor polarizabilities of the Cs ground states. We give details of the apparatus and measurement techniques as well as our first 500 Hz half-period Ramsey fringes.
authors.affiliation: Fribourg Group of Atomic Physics (FRAP), Department of Physics, University of Fribourg, Fribourg, Switzerland. jean-luc.robyr@unifr.ch
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Robyr
authors.forename: Paul
authors.initials: P
authors.lastname: Knowles
authors.forename: Antoine
authors.initials: A
authors.lastname: Weis