Testing strong-field QED to second-order in the highly correlated atomic system berylliumlike Pb78+ by electron-ion recombination spectroscopy
S. Schippers, C. Brandau, S. Fuchs, M. Lestinsky, S. X. Wang, C. Y. Zhang, N. R. Badnell, A. Borovik Jr., M. Fogle, V. Hannen, Z. Harman, P. -M. Hillenbrand, E. B. Menz, Y. Zhang, Z. Andelkovic, F. Herfurth, R. Heß, A. Kalinin, C. Kozhuharov, C. Krantz, S. Litvinov, B. Lorentz, U. Spillmann, M. Steck, G. Vorobyev, D. Banaś, S. Fritzsche, E. Lindroth, X. Ma, A. Müller, R. Schuch, A. Surzhykov, M. Trassinelli, K. Ueberholz, C. Weinheimer, Th. Stöhlker
公開日: 2025/2/21
Abstract
A low-energy storage ring with an ultracold electron cooler has been coupled with a heavy-ion accelerator facilitating high-resolution electron-ion collision spectroscopy of the heaviest few-electron ions. In the present work resonant electron-ion recombination of berylliumlike Pb$^{78+}$ ions was measured in the collision-energy range 9.3-16.5eV and a value of 244.937(30) eV is derived for the Pb$^{78+}$($2s^2\;^1S_0 - 2s\,2p\;^3P_1$) excitation energy. This result agrees with the most recent (less accurate) theoretical value of 244.942(52) eV [Malyshev et al., Physical Review A 110, 062824 (2024)], which has been calculated by applying strong-field QED rigorously up to the second order. The present investigation suggests that further technical improvements can potentially increase the experimental accuracy by an order of magnitude.