Two-body $P$-state energies at $\alpha^6$ order
Atomic Physics
2026-02-19 v3
Abstract
We present an analytical calculation of the complete correction to energies of -levels of two-body systems consisting of the spin- or extended-size particles with arbitrary masses and magnetic moments. The obtained results apply to a wide class of two-body systems such as hydrogen, positronium, muonium, and pionic or aniprotonic helium ion. We found an additional correction for -levels of positronium, which was previously overlooked. Our results are also relevant for light muonic atoms, whose accurate theoretical predictions are required for extracting the nuclear charge radii.
Keywords
Cite
@article{arxiv.2401.05922,
title = {Two-body $P$-state energies at $\alpha^6$ order},
author = {Vojtěch Patkóš and Vladimir A. Yerokhin and Krzysztof Pachucki},
journal= {arXiv preprint arXiv:2401.05922},
year = {2026}
}
Comments
14 pages, 1 figure, corrected the second-order iteration of the Breit Hamiltonian, final results for positronium P-states agree now with former calculations