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

We report measured rate coefficients for electron–ion recombination of Si¹⁰⁺ forming Si⁹⁺ and of Si⁹⁺ forming Si⁸⁺, 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 Si⁹⁺ and from 0 to 2000 eV for Si¹⁰⁺, thus, extending previous measurements for Si¹⁰⁺ (Orban et al 2010 Astrophys. J. 721 1603) to much higher energies. Experimentally derived rate coefficients for the recombination of Si⁹⁺ and Si¹⁰⁺ 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 (Si⁹⁺ and Si¹⁰⁺) and in collisionally ionized plasmas (Si¹⁰⁺ only). In the corresponding temperature ranges, the experimentally derived rate coefficients agree with the latest corresponding theoretical results within the experimental uncertainties. (paper)