High-Resolution Laser Spectroscopy and Time Variation of Fundamental Constants
Résumé
In 2003, we remeasured the frequency of the IS (F = 1, m(F) = 1) -> 2S (F' = 1, m(F) = 1) two-photon transition in atomic hydrogen with a self-referenced optical frequency comb relative to the Cs-133 ground-state hyperfine splitting. By comparison with an earlier measurement made in 1999, we can set an upper limit on its time variation of -29(57) Hz within 44 months. Combining this result with recently published absolute frequency measurements of optical transitions in single trapped Hg+ and Yb+ ions, we deduce (partial derivative/partial derivative t)ln alpha = (-0.3 +/- 2.0) x 10(-15) yr(-1) and (partial derivative/partial derivative t)ln(mu(Cs)/mu(B)) = (2.4 +/- 6.8) x 10(-15) yr(-1) as limits on the fractional time variation of the fine structure constant (x and the ratio of the Cs-133 nuclear magnetic moment mu(Cs) and the Bohr magneton mu(B), respectively. Using frequency comparisons of microwave Rb-87 and Cs-133 fountain clocks, we deduce additional stringent limits on the fractional time variation of mu(Rb)/mu(Cs) and mu(Rb), where mu(Rb) is the magnetic moment of the Rb-87 nucleus. All limits are compatible with zero drift and, for the first time, do not require any model assumptions about the relative drifts of fundamental constants.