Reexamination of helium fine structure

Abstract

In order to explain discrepancies between theoretical predictions and experimental data for the helium fine structure, we check and recalculate all theoretical contributions up to orders m\alpha^7 and m^2/M\alpha^6. The previous result for the m\alpha^7 correction is improved by a much more accurate calculation of relativistic corrections to the Bethe logarithm. The theoretical values of the 2^3P_0-2^3P_1 and 2^3P_1-2^3P_2 fine structure intervals in helium are, correspondingly, \nu_{01} = 29616946.2(1.6) kHz and \nu_{12} = 2291177.3(1.6) kHz, with the uncertanties being due to higher-order effects. For the small interval \nu_{12}, the theoretical value agrees with the experimental data, whereas for the large interval \nu_{01}, a discrepancy of about 3 standard deviations is present.