Benchmarking Dielectronic Recombination Rate Coefficients for Carbon-like Ca14+

Abstract

Dielectronic recombination (DR) rate coefficients for C-like Ca ^14+ were measured by Wen et al. at the electron cooler storage ring in Lanzhou, China. The measured DR rate coefficients from 0 to 92 eV cover most of the DR resonances associated with the 2 s ^2 2 p ^2 → 2 s ^2 2 p ^2 and 2 s ^2 2 p ^2 → 2 s 2 p ^3 core transitions. In addition, Wen et al. reported theoretical results calculated with the Flexible Atomic Code (FAC) and AUTOSTRUCTURE (AS). However, these theoretical results show widespread and significant differences from the measured DR spectrum in both resonance energies and strengths, as well as between each other. In the present work, we uncover the reasons behind these large differences, both theoretical and experimental. The new FAC and AS results reproduce the observed spectrum in detail, especially at resonance energies below 8 eV, and they are in very close agreement with each other. The present plasma rate coefficients agree with the experimentally determined values to within 20% and 2% in the photoionized plasma (PP) and collisional ionized plasma (CP) temperature ranges, respectively. This is in contrast to the previous theoretical results, which showed differences with the experiment of up to ∼40% over the PP temperature range. The present FAC and AS results agree with each other within 5% in the PP and CP temperature ranges. Thus, the theoretical uncertainty is greatly reduced for the DR of Ca ^14+ and the present benchmarking with the experiment gives confidence to data users modeling non–local thermodynamic equilibrium plasma.

Keywords

• Atomic data
• Atomic data benchmarking
• Plasma astrophysics
• Collisional processes
• Atomic physics