Narrow Results

In this work we present the status of the Brazilian program on scientific time and frequency metrology established at Center of Optical and Photonical Science, in São Carlos four years ago [1]. We report major shifts evaluated, in order to characterize our standard. We have applied the method proposed by Makdissi et.al. [2,3] to our clock in order to determine the Rabi frequency, the second-order Doppler shift and the end-to-end cavity phase shift. By this method, we could also obtain information about the behavior of the shifts as a function of the modulation amplitude. The improvements here reported were responsible for a gain of two orders of magnitude in the frequency standard's stability. We present the evaluation of our frequency standard and a progress report of our atomic fountain.

This article describes recent frequency measurements performed with the LNE-SYRTE atomic clock ensemble. First, we report a new determination of the rubidium 87 hyperfine frequency, performed using Rb and Cs atomic fountains. The measurement has a statistical uncertainty below 10^-16 and an overall uncertainty of 1.1 parts in 10¹⁵. Second, we report the first laser spectroscopy of the ¹S₀-³P₀ optical clock transition at 265.6 nm in laser-cooled fermionic isotopes of neutral mercury. The absolute frequency is measured with a fractional uncertainty of ~ 5 parts in 10¹² which improves upon previous indirect determinations by more than 4 orders of magnitude, an important step toward the realization of an optical lattice clock.