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

Abstract

Abstract. We report measured rate coefficients for electron-ion recombination for Si 10+ forming Si 9+ and for Si 9+ forming Si 8+ , respectively. The measurements were performed using the electron-ion merged-beams technique at a heavy-ion storage ring. Electron-ion collision energies ranged from 0 to 50 eV for Si 9+ and from 0 to 2000 eV for Si 10+ , thus, extending previous measurements for Si 10+ [Orban et al 2010 Astrophys. J. 721 1603] to much higher energies. Experimentally derived rate coefficients for the recombination of Si 9+ and Si 10+ ions in a plasma are presented along with simple parameterizations. These rate coefficients are useful for the modeling of the charge balance of silicon in photoionized plasmas (Si 9+ and Si 10+ ) and in collisionally ionized plasmas (Si 10+ only). In the corresponding temperature ranges, the experimentally derived rate coefficients agree with the latest corresponding theoretical results within the experimental uncertainties.

Dielectronic recombination rate coefficients of carbon-like Kr30+

“…Particularly, a rather large discrepancy below 1.5 eV has been observed. In general, the strong electronic correlation effects are challenging for the theoretical calculations at low energies, where numerous resonances are predominated by fine structures near the autoionization threshold, thus making the theoretical treatment difficult [56]. In addition, some resonances such as 2s2p 3 [ 3 P 2 ]7l are widely distributed in the range of 0-7 eV, which makes the situation more complex.…”

Dielectronic recombination strengths and plasma rate coefficients of multiply charged ions

“…While a few very accurate measurements of DR spectra are known for selected ions (e.g., Schippers et al 2001;Kieslich et al 2003;Schuch et al 2005, Bernhardt et al 2016), more often than not detailed ab initio calculations are required in order to describe the resonances and plasma rate coefficients for a wide range of ions across the periodic table. Especially, and perhaps apart from few-electron ions with rather simple shell structures, the low-lying DR resonances and strengths are still a challenge for current atomic theory.…”