Erlangen 2022 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 21: Highly charged ions and their applications
A 21.3: Poster
Mittwoch, 16. März 2022, 16:30–18:30, P
Redefined vacuum approach and gauge-invariant subsets in two-photon-exchange diagrams — •Romain Soguel1, Andrey Volotka2, Dmitry Glazov3, and Stephan Fritzsche1 — 1Helmholtz-Institut Jena, Jena, 07743, Germany — 2ITMO University, St. Petersburg, 197101, Russia — 3St. Petersburg State University, St. Petersburg, 199034, Russia
Within bound-state QED, the interelectronic interaction is treated perturbatively as an expansion over the number of exchanged photons. So far, zeroth-order many-electron wave-function constructed as a Slater determinant (or sum of Slater determinants) with all electrons involved were used in the performed derivations. The vacuum redefinition in QED, which is extensively used in MBPT to describe the states with many electrons involved, is proposed as a path towards an extension of two-photon-exchange calculations to other ions and atoms.
The two-photon-exchange diagrams for atoms with single valence electron are investigated. Calculation formulas are derived for an arbitrary state within rigorous bound-state QED framework utilizing the redefined vacuum formalism. This approach enables the identification of gauge-invariant subsets at two- and three-electron diagrams and separate between the direct and exchange contributions at two-electron graphs. Thus, the consistency of the obtained results is verified by comparing the results for each identified subset in different gauges. The gauge invariance of found subsets is demonstrated both analytically (for an arbitrary state) as well as numerically for 2s, 2p1/2, and 2p3/2 valence electron in Li-like ions.