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We measure the J = 1 to J = 2 fine structure interval in the ( 3)2P state of helium to be 2 291 175.9(1.0) kHz. We use laser excitation of an atomic beam along with an integrated electro-optic modulator technique to obtain this result. The result is consistent (2.9+/-3.2 kHz) with what could be considered an earlier version of this experiment but is not in good agreement ( 20+/-5 kHz and 22+/-8 kHz) with the two other precision determinations of this interval. The current theoretical prediction lies between and overlaps the experiments.

We measure 31,908,131.25(30) kHz for the 2(3)}P J=0 to 2 fine structure interval in helium. The difference between this and theory to order mα7 (20 Hz numerical uncertainty) implies 0.22(30) kHz for uncalculated terms. The measurement is performed by using atomic beam and electro-optic laser techniques. Various checks include a 3He 2{3}S hyperfine measurement. We can obtain an independent value for the fine structure constant α with a 5 ppb experimental uncertainty. However, dominant mα8 terms (potentially 1.2 kHz) limit the overall uncertainty to a less competitive 20 ppb in α.

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