Energy-dependent perturbation theory: Possibility for improved tests of quantum-electrodynamics

TL;DR

This paper introduces an energy-dependent perturbation theory to enhance the accuracy of quantum-electrodynamics calculations for highly charged ions, potentially resolving existing experimental-theoretical discrepancies.

Contribution

It develops a novel energy-dependent perturbative approach that integrates QED effects into many-body calculations more rigorously than before.

Findings

Numerical results demonstrate improved theoretical accuracy.

The method accounts for effects previously neglected in such calculations.

Further work is ongoing to compare with experimental discrepancies.

Abstract

Measurements of energy separations in highly charged ions can in many cases nowadays be performed with very high accuracy, an accuracy that sometimes cannot be matched by the corresponding theoretical calcula- tions. Furthermore, it has recently been demonstrated that there is a systematic deviation between experimental and theoretical results for the K- alpha lines of medium-heavy heliumlike ions. We have during a number of years been developing a general procedure for energy-dependent perturbative calcu- lations, which opens up a unique possibility of incorporating the energy- dependent QED perturbations into the all-order many-body perturbation expansion in a rigorous way. Such an expansion will yield several important effects, never before accounted for in this type of analysis, which is expected to increase the theoretical accuracy considerably. Calculation of some of these effects have been performed at our laboratory in Gothenburg, and numerical results are given. Further work along this line is now in progress. To what extent the improved procedure might explain the discrepancy found by Chantler et al. remains to be seen.