Spectroscopy of berylliumlike xenon ions using dielectronic recombination

Abstract

Be-like ions have been investigated employing the resonant electron–ion collision process of dielectronic recombination (DR) as a spectroscopic tool. The experiments were performed at the experimental storage ring in Darmstadt, Germany, using its electron cooler as a target for free electrons. DR Rydberg resonance series for the associated intra-L-shell transitions and were observed with high resolution. In addition to these excitations from the ground state we determined resonances associated with excitations of ions initially in the metastable state. The corresponding excitation energies were determined to be and and . These excitation energies are compared with previous measurements and with recent state-of-the-art atomic structure calculations.

Absolute rate coefficients for photorecombination of beryllium-like and boron-like silicon ions

“…29 Si 10+ and 28 Si 9+ were provided by the MPIK tandem and linear accelerators and injected into TSR at energies of about 120 and 100 MeV, respectively. The choice of the less abundant isotope 29 Si with a natural abundance of only 4.7% for the measurements with Si 10+ is motivated below (section 2.1). The stored ion currents were typically 10-20 µA for Si 10+ and 1 µA for Si 9+ after injection and from then on decreased exponentially as a function of storage time.…”

“…For nuclei with a nonzero magnetic moment, hyperfine quenching shortens the 3 P 0 lifetime by 6 orders of magnitude. Recent calculations yield a value of about 17 s for the hyperfine induced (HFI) lifetime of the 29 Si 10+ (2s 2p 3 P 0 ) level [17,60]. In fact, one motivation for the present recombination measurement was to derive the HFI 3 P 0 lifetime using the same approach as already successfully applied for the HFI lifetime of the 2s 2p 3 P 0 level in Be-like 47 Ti 18+ [25] and 33 S 12+ [23].…”

“…After an ion-storage time of 2 s, only two levels remain significantly populated, i.e., the 2s 2 1 S 0 ground level and the 2s 2p 3 P 0 first excited level with their fractional populations amounting to 93% and 7%, respectively. At longer times, the 2s 2p 3 P 0 level is depopulated by the 2s 2p 3 P 0 → 2s 2 1 S 0 HFI decay in 29 Si 10+ . Since data collection in the experiment started only after an initial cooling time of 2 s, we assume in the following that the fraction of ions in the 2s 2p 3 P 0 level was at most 7%.…”

“…This is attributed to the fact that DR resonances of the 3 P 0 parent ions have been found to be weak and to be blended with the rich DR resonance structure of the 1 S 0 ground state parent ions. We estimated the 3 P 0 fraction in the parent beam by solving a set of rate equations [32] that accounts for the population and depopulation of the various 29 Si 10+ levels by radiative transitions. The corresponding rates were taken from [16,17] (table 1), and a Boltzmann distribution with a temperature of about 2100 eV (corresponding to the ion energy at the last stripping foil in the accelerator) was chosen as the initial population of the levels.…”

Physics book: CRYRING@ESR

“…At the ESR, the transition between the hyperfine levels of the ground state of H-like bismuth and uranium ions (Klaft et al, 1994;Seelig et al, 1998;Ullmann et al, 2015) has been induced by laser light (massively shifted in the rest frame of the fast ions), and an upper level lifetime in the millisecond range was measured (Klaft et al, 1994). Furthermore, DR spectroscopy was used to explore two-photon transitions in Be-like xenon ions (Bernhardt et al, 2012(Bernhardt et al, , 2015b. Hence, GSI has already demonstrated mastering atomic lifetime measurements on very highly charged ions.…”