Journal article

Publication year: 2019

Journal: Astronomy & Astrophysics

Volume number: 627

ISSN: 1432-0746

Open access status: Green

DOI Link: https://doi.org/10.1051/0004-6361/201935648

Publisher: EDP Sciences

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 Delta 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 Ni19+ 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 Delta N = 0 DR resonances dominate.

Harvard Citation style: Wang, S., Huang, Z., Wen, W., Chen, C., Schippers, S., Xu, X., et al. (2019) Dielectronic recombination rate coefficients of fluorine-like nickel, Astronomy & Astrophysics, 627, Article A171. https://doi.org/10.1051/0004-6361/201935648

APA Citation style: Wang, S., Huang, Z., Wen, W., Chen, C., Schippers, S., Xu, X., Sardar, S., Khan, N., Wang, H., Dou, L., Mahmood, S., Zhao, D., Zhu, X., Mao, L., Ma, X., Li, J., Tang, M., Mao, R., Yin, D., ...Zhu, L. (2019). Dielectronic recombination rate coefficients of fluorine-like nickel. Astronomy & Astrophysics. 627, Article A171. https://doi.org/10.1051/0004-6361/201935648