Reexamination of helium fine structure

TL;DR

This paper revisits helium fine structure calculations, improving theoretical precision up to order m and resolving discrepancies with experimental data for some intervals, but not all.

Contribution

It provides a more accurate calculation of relativistic corrections to the Bethe logarithm and updates helium fine structure predictions.

Findings

Theoretical value for ^3P_0-2^3P_1 interval is 29616946.2(1.6) kHz.

Theoretical value for ^3P_1-2^3P_2 interval is 2291177.3(1.6) kHz.

Discrepancy of about 3 standard deviations remains for the ^3P_0-2^3P_1 interval.

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.