Contributions of dielectronic, trielectronic, and metastable channels to the resonant intershell recombination of highly charged silicon ions

Abstract

Intershell, resonant electronic recombination is studied experimentally in an electron-beam ion trap for O-like Si⁶⁺ to He-like Si¹²⁺ ions at plasma temperatures in the megakelvin range similar to those found in the solar radiative zone and is compared to extended multiconfiguration Dirac-Fock and relativistic configuration-interaction predictions. For this low-Z ion, the higher-order electronic recombination processes are comparable in strength to the first-order one. The ratio of trielectronic to dielectric recombination for B-like species agrees well with predictions, whereas for C-like ions the measured value is only half as large. This difference is explained by the influence of metastable states populated in the recombining plasma

Investigation of the intershell higher order resonant recombination and polarization of X‐ray emission of B‐like silicon ions

“…Our calculated resonance energies agree well with the FAC results calculated by Baumann et al, and there is a slight difference less than 0.5% between our results and the multiconfiguration Dirac‐Fock (MCDF) results by Baumann et al and Chen et al For the stronger resonances ( S id >10 −21 cm 2 eV ) , our calculated resonance strengths are closer to the FAC results by Baumann et al and the MCDF results by Chen et al with the difference about 0.5–6.3% and 11.9–26.3%, respectively, except for the [1 s 2 s 2 2 p 1/2 2 p 2 ] 1 (labeled 5) and [1 s 2 s 2 2 p 1/2 2 p 2 ] 1 (labeled 8). However, the MCDF results by Baumann et al differ from our results by 59%. It should be noted that in Table , the two resonance states (labeled 6) and [1 s 2 s 2 2 p 1/2 2 p 2 ] 2 (labeled 9) correspond to DR and TR processes respectively.…”

“…It should be noted that in Table , the two resonance states (labeled 6) and [1 s 2 s 2 2 p 1/2 2 p 2 ] 2 (labeled 9) correspond to DR and TR processes respectively. But these are misidentified in the study of Baumann et al, which lead to an overestimation of TR contributions.…”

“…Recently, many theoretical and experimental studies have been performed to investigate the K‐shell DR process and X‐ray radiative spectra of highly charged Si ions. For instance, absolute cross sections for DR of Li‐like Si 11+ ions associated with Δ n =1(1 s →2 l ) and Δ n =2(1 s →3 l ) transitions have been measured with high energy resolution at heavy ion storage ring by Kenntner et al The prominent Δ n =1 DR resonances in H‐ and He‐like Si have been detected in an electron beam ion trap (EBIT) by Ali et al The intershell resonant electronic recombination have also been studied experimentally in EBIT for O‐like Si 6+ to He‐like Si 12+ ions by Baumann et al They demonstrated that higher order (HO) electronic recombination process, such as trielectronic recombination (TR) and quadruelectronic recombination (QR) significantly influence the K‐shell recombination cross section. In anisotropic plasmas, such as solar flares, pulsars, Tokamak plasmas, and laser‐produced plasmas, X‐ray emission following intershell resonant processes is usually anisotropic and polarized .…”

“…In this study, we focus mainly on KLL‐resonant recombination and the polarization of X‐ray emission of B‐like Si . Using the Flexible Atomic Code (FAC) based on the relativistic configuration interaction approach, the resonance energy, resonance strength, and cross section are carefully calculated for the recombination of initially Si 9+ ions in the ground state 2 P 1/2 and the long‐lived metastable state 2 P 3/2 ( τ =345ms). The contributions of HO TR and QR processes are revealed.…”

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

“…[47]. In addition, detailed measurements of recombination resonances have been conducted using x-ray spectroscopy of silicon ions in an electron-beam ion-trap (EBIT) [48]. The previous experimental data for Si 10+ [22] cover a limited range of electron-ion collision energies of 0-43 eV.…”