Abstract
Second-order Zeeman frequency shift is one of the major systematic factors affecting the frequency uncertainty performance of cesium atomic fountain clock. Second-order Zeeman frequency shift is calculated by experimentally measuring the central frequency of the (1,1) or (−1,−1) magnetically sensitive Ramsey transition. The low-frequency transition method can be used to measure the magnetic field strength and to predict the central fringe of (1,1) or (−1,−1) magnetically sensitive Ramsey transition. In this paper, we deduce the formula for magnetic field measurement using the low-frequency transition method and measured the magnetic field distribution of 4 cm inside the Ramsey cavity and 32 cm along the flight region experimentally. The result shows that the magnetic field fluctuation is less than 1 nT. The influence of low-frequency pulse signal duration on the accuracy of magnetic field measurement is studied and the optimal low-frequency pulse signal duration is determined. The central fringe of (−1,−1) magnetically sensitive Ramsey transition can be predicted by using a numerical integrating of the magnetic field “map”. Comparing the predicted central fringe with that identified by Ramsey method, the frequency difference between these two is, at most, a fringe width of 0.3. We apply the experimentally measured central frequency of the (−1,−1) Ramsey transition to the Breit-Rabi formula, and the second-order Zeeman frequency shift is calculated as 131.03 × 10−15, with the uncertainty of 0.10 × 10−15.
Highlights
Atomic clocks have played an important role in the field of basic research and engineering technology [1,2,3], as the reference clock [4,5,6,7,8], cesium atomic fountain clock, calibrates other atomic clocks with the highest accuracy
A full map of the magnetic field at all points along the atomic trajectory within and above the Ramsey cavity is acquired by using the low-frequency transition method, and the central fringe of the (−1,−1) magnetically sensitive Ramsey transition can be calculated by a numerical integration of the field “map”
Second-order Zeeman frequency shift is a frequency bias induced by C-field, which limits the accuracy improvement of cesium atomic fountain clock
Summary
Atomic clocks have played an important role in the field of basic research and engineering technology [1,2,3], as the reference clock [4,5,6,7,8], cesium atomic fountain clock, calibrates other atomic clocks with the highest accuracy. Second-order Zeeman frequency shift and its uncertainty are calculated by measuring the central frequency of the (1,1) or ((−1,−1)) magnetically sensitive Ramsey transition fringes in space and time domains. The low-frequency transition method is method to measure the magnetic field of the cesium atomic fountain clocks. Ramsey transition can be predicted by a numerical integration of the magnetic field distribution obtained by the low-frequency transition meth magnetic field “map”, and the difference between the predicted fringe and the measured determine the position of the central fringe of the (−1,−1) magnetically sensitive fringe is less than 0.3 in width. The low-frequency transition method can determine thefrequency position of shift the central fringe of the (−1,−1) magnetically sensitive Ramsey transition, and the second-order Zeeman frequency shift can be calculated. 1 shows thecontains transitionsthree between theof ground state and theCesium excited state ofD2 line the cesium which three kinds transition band
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