High-precision measurements of n=2→n=1 transition energies and level widths in He- and Be-like argon ions

Abstract

We performed a reference-free measurement of the transition energies of the 1s2p 1 P 1 → 1s 2 1 S 0 line in He-like argon, and of the 1s2s 2 2p 1 P 1 → 1s 2 2s 2 1 S 0 line in Be-like argon ions. The highlycharged ions were produced in the plasma of an Electron-Cyclotron Resonance Ion Source. Both energy measurements were performed with an accuracy better than 3 parts in 10 6 , using a double flat-crystal spectrometer, without reference to any theoretical or experimental energy. The 1s2s 2 2p 1 P 1 → 1s 2 2s 2 1 S 0 transition measurement is the first reference-free measurement for this core-excited transition. The 1s2p 1 P 1 → 1s 2 1 S 0 transition measurement confirms recent measurement performed at the Heidelberg Electron-Beam Ion Trap (EBIT). The width measurement in the He-like transition provides test of a purely radiative decay calculation. In the case of the Be-like argon transition, the width results from the sum of a radiative channel and three main Auger channels. We also performed Multiconfiguration Dirac-Fock (MCDF) calculations of transition energies and rates and have done an extensive comparison with theory and other experimental data. For both measurements reported here, we find agreement with the most recent theoretical calculations within the combined theoretical and experimental uncertainties.

Reference-free measurements of the1s2s2p2P1/2,3/2o→Machado1, Bian2, Paul3 et al. 2020Phys. Rev. ASelf Cite141130View full textAdd to dashboardCite

“…These measurements are relative to the theoretical predictions of the M1 line energy by Artemyev et al [20]. The only available reference-free measurement of a transition from a core-excited autoionizing level is that of the 1s2s 2 2p 1 P 1 → 1s 2 2s 2 1 S 0 transition in Be-like argon [19]. The very accurate measurements of several coreexcited lines performed using an EBIT and the PETRA III synchrotron radiation facility use K edges of several elements (Mn, Fe, Co, Ni, and Cu) for calibration [50].…”

“…There have also been high-accuracy reference-free measurements of two-electron ions using both EBITs [15,17] and electron cyclotron resonance ion sources (ECRISs) [18,19]. Agreement between measurements in heliumlike ions and QED calculations [20] is also excellent (see Refs.…”

“…Agreement between measurements in heliumlike ions and QED calculations [20] is also excellent (see Refs. [1,19] for a detailed review of available measurements and a comparison with theory). For three-electron ions there are very accurate measurements and calculations for the 1s 2 2p 2 P J → 1s 2 2s 2 S 1/2 transitions, for elements up to very heavy ones like lead, bismuth, thorium, and uranium [21][22][23][24][25][26][27][28] using both EBITs and accelerators.…”

Stringent tests of QED using highly charged ions

“…Although the experimental results of a number of works (see Refs. [15,16,17,18,19,20]) for the transition energies in He-like ions agree with the most elaborated QED calculations [21], independent theoretical predictions would be very desirable. In Table 2 we present the results of our calculation of the 1s2p 1 P 1 − 1s 2 1 S 0 transition energy in heliumlike titanium and compare them with the theoretical result of Ref.…”

Highly charged ions: Optical clocks and applications in fundamental physics

“…For two-electron systems, and specifically for heliumlike ions, there is abundant theoretical literature (Andreev et al, 2001;Indelicato et al, 1987;Johnson et al, 1995;Lindgren et al, 2001Lindgren et al, , 1995. At medium Z, relativistic configuration interaction and perturbative many-body methods (Chen et al, 1993;Cheng et al, 1994;Plante et al, 1994) as well as unified-method calculations (Drake, 1979(Drake, , 1988(Drake, , 2002Yan and Drake, 1995) have yielded reasonably accurate results in close agreement with measurements of the 1s − 2p x-ray transitions (Amaro et al, 2012;Briand et al, 1984;Bruhns et al, 2007;Epp et al, 2015;Indelicato et al, 1986;Kubiček et al, 2012;Machado et al, 2018;Rudolph et al, 2013;Kubiček et al, 2014;Widmann et al, 1996).…”