Dielectronic recombination rate coefficients of fluorine-like nickel

Abstract

Electron-ion recombination rate coefficients for fluorine-like nickel ions have been measured by employing the merged-beam technique at the cooler storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. The measured spectrum covers the energy range of 0-160 eV, including all the dielectronic recombination (DR) resonances associated with ∆N = 0 core excitations. The DR cross sections in this energy range were calculated by a relativistic configuration interaction method using the flexible atomic code (FAC). Radiative recombination (RR) cross sections were obtained from a modified version of the semi-classical Bethe & Salpeter (1957, Quantum Mechanics of One-and Two-Electron 56 Systems (Springer)) formula for hydrogenic ions. The comparison between the measurement and the calculation shows that the present theoretical model still needs to be improved at low collision energies. Temperature dependent plasma recombination rate coefficients were derived from the measured DR rate coefficients in the temperature range of 10 3 -10 8 K and compared with the presently calculated result as well as previous available data in the literature. The experimentally derived data agree well with the theoretical calculations for temperatures where Ni 19+ ions form in collisionally ionized plasmas. At lower temperatures typical for photo-ionized plasmas, discrepancies are found beyond the experimental uncertainty, which can be attributed to the disagreement between the measurement and the calculation of the low-lying DR resonances. The present experimental result benchmarks the plasma DR rate coefficients, in particular for temperatures below 10 5 K where the ∆N = 0 DR resonances dominate.

Absolute dielectronic recombination rate coefficients of highly charged ions at the storage ring CSRm and CSRe

“…Since the first calibration DR experiment with Lilike Ar 15+ ions at the CSRm in 2015, [20] DR rate coefficients of a series of HCIs, including 40 Ar 12+,13+,14+ , [21][22][23] 40 Ca 14+,16+,17+ , [24][25][26] 58 Ni 19+ , [28] 112 Sn 35+ , [31] and 073401-2…”

“…More recently, the main cooler storage ring (CSRm) and the experimental cooler storage ring (CSRe) at the Heavy Ion Research Facility in Lanzhou (HIRFL) started contributing DR rate coefficients for HCIs. Recombination experiments with 36 Ar 15+ , 40 Ar 12+,13+,14+,15+ , 40 Ca 14+,16+,17+ , 56 Fe 17+ , 58 Ni 19+ , and 76 Kr 25+ ions [20][21][22][23][24][25][26][27][28][29] have been accomplished at the CSRm in the past few years, and the first calibration experiment with Na-like Kr 25+ ions has been successfully performed at the CSRe. [30] In this paper, the recent progress on DR experiments at the HIRFL-CSRm and CSRe is overviewed.…”

Absolute rate coefficients for dielectronic recombination of Na-like Kr25+

“…Measurements of the electron-ion recombination rate coefficients were performed at the main cooler storage ring (CSRm) at IMP in Lanzhou, China. A detailed description of the experimental setup and method can be found in the literature [42,43]. Here, we will only briefly describe the electron-ion recombination experiment of sodiumlike Kr 25+ at the CSRm.…”

Enhancement of electron–ion recombination rates at low energy range in the heavy ion storage ring CSRm*

“…The details about the DR calculation method for Be-like Ar 14+ , Be-like Ca 16+ , and F-like Ni 19+ can be found in Refs. [2,36,37]. Instead of separate calculations of RR and DR contributions, the total recombination rate coefficient can be derived by adding the continuous RR background to the DR spectrum including the AUTOSTRUCTURE and FAC calculations.…”

“…[1] The experimentally obtained electron-ion recombination rate coefficients can be not only used to study the energy level structure of highly charged ions, thereby testing the theoretical methods for atomic structures calculation, but also used as the basic input parameters for plasma diagnosis and modeling to interpret the emission spectrum of astrophysical and man-made plasmas. [2] Additionally, the electron-ion recombination also reduces the lifetime of the ion beam which leads to the positive ions loss mechanism during electron cooling, particularly at high ion charge state and high beam velocity when the residual gas processes become less important. [3] The electron-ion recombination with its large cross section and rates at the low energies also provides a very favorable scheme for the production of antihydrogen.…”