FREQUENCY COMPARISON BETWEEN CS AND MG STANDARDS AND STABILITY OF FUNDAMENTAL CONSTANTS

The frequency comparisons between Cs and Mg atomic standards performed during a period of 420 days are reported with an analysis of the effe ct of the temperature on the stability and the repeatability of the Mg output frequency. The Mg prototype shows a short-term stability sigma (y) = 1.2 10(-11) tau(-1/2) and a repeatability of 3 . 10(-13); its ac curacy has been evaluated to be at the level of 1 . 10(-12). The resul ts reported here for the frequency comparisons may well be interpreted from the point of view of the time stability of the quantity g(I)m(e) /m(p), with g(I) the gyromagnetic ratio of Cs, obtaining the limit 2.6 .(-13) yr.(-1) for the relative rate of change. From this value one c an deduce a limit for the relative rate of change of g(p)m(e)/m(p) and of alpha too. The results here reported may also be interpreted as a ''null'' gravitational red-shift experiment allowing a new test of the Einstein equivalence principle.