LAUSR

We have derived the complete formula for the αm contribution to energy levels of an arbitrary triplet state of the helium atom, performed numerical calculations for the 2S and 2P states, and thus improved the theoretical accuracy of ionization energies of these states by more than an order of magnitude. Using the nuclear charge radius extracted from the muonic helium Lamb shift, we obtain the theoretical prediction in excellent agreement with the measured 2S − 2P transition energy [X. Zheng et al., Phys. Rev. Lett. 199, 263002 (2017)]. At the same time we observe significant discrepancies with experiments for the 2S − 3D and 2P − 3D transitions.