High-accuracy measurement of the ground-state hyperfine splitting in an atomic fountain

¹ BNM-LPTF, Observatoire de Paris - 61 Av. Denfert-Rochereau, 75014 Paris, France
² Instituto de Física de São Carlos-USP, Departamento de Fisica e Ciência dos Materiais P.O. Box 369, Av. Dr. Carlos Botelho, 1465, São Carlos, SP, 13560-970, Brazil
³ Institutul National de Fizica Laserilor, Plasmei si Radiatiei P.O. Box-MG36, Bucuresti, Magurele, Romania
⁴ Laboratoire Kastler Brossel, Ecole Normale Supérieure 24 rue Lhomond, F-75231 Paris Cedex 05, France

Received: 4 November 1998
Accepted: 21 December 1998

Abstract

We describe the operation of a laser-cooled rubidium ⁸⁷Rb frequency standard. We present a new measurement of the ⁸⁷Rb hyperfine frequency with a relative accuracy, by comparison with a Cs fountain primary standard. The measured ⁸⁷Rb ground-state hyperfine splitting is  Hz. This value differs from previously published values (see Essen L., Hope E. G. and Sutcliffe D. ,Nature 189 1961 298; Penselin S., Moran T., Cohen W. and Wscinkler G., Phys. Rev., 127 1962 524; Arditi M. and Cerez P. IEEE Trans. Instrum. Meas. IM-21 1972 391) by about  Hz and is 10⁴ times more accurate. Because of the low collisional shift in ⁸⁷Rb, future improvements may lead to a stability of and a relative accuracy in the 10^-17 range.