Measuring the fine structure constant using helium fine structure

The fine structure of the 2/sup 3/S-2/sup 3/P transition in helium has been precisely measured using laser excitation of an atomic beam. The results give /spl alpha//sup -1/=137.035 853 (3) (7) (99). The three values of standard deviation are from the uncertainty in the measured atomic frequency interval, the total experimental error (including the frequency calibration), and helium theory (1978 value), respectively.<
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