Effect of plasma screening on electron impact excitation and ionization of Fe16+ in a dense environment. Issue 4 (3rd May 2021)

• Record Type: Journal Article
• Authors: Zeng, Jiaolong; Li, Yongjun; Yuan, Jianmin
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 504:Issue 4(2021)
• Page Start: 4785
• Page End: 4792
• Publication Date: 2021-05-03
• Subjects: atomic data -- atomic processes -- dense matter -- Sun: interior -- stars: interiors; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1230
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Electron impact excitation and ionization with atoms and ions within a dense plasma are fundamental microscopic processes that determine the ionization balance, physical properties (such as electron conductive opacity and thermal conductivity) and plasma formation and dynamics. While collision cross-sections and rates are well studied in dilute systems, similar investigations are scarce for dense plasmas under stellar interior conditions using an appropriate plasma-screening potential. Here we investigate the plasma-screening effect on the electron impact excitation and ionization cross-sections, effective collision strengths, and rate coefficients within plasmas under stellar interior conditions in a mass density range of 1–15.748 g cm −3 and a temperature range of 200–1000 eV. These investigations were carried out using our recently developed plasma-screening model, taking Fe 16+ as an example. The results show that the cross-sections of the electron impact excitation are generally decreased, whereas they are always significantly increased for the collision ionization due to the plasma screening. In a plasma at a temperature of 200 eV and density of 15.748 g cm −3, the plasma screening causes a decrease in the excitation cross-section of 36 per cent for the dipole-allowed transition $2\mathrm{ s}^22\mathrm{ p}^6~^1\mathrm{ S}_0 \rightarrow 2\mathrm{ s}^22\mathrm{ p}^53\mathrm{ d}~^1\mathrm{ P}^o_1$ and of 50 per cent for the dipole-forbidden transition $2\mathrm{ s}^22\mathrm{ p}^6~^1\mathrm{ S}_0 \rightarrow 2\mathrm{ s}^22\mathrm{ p}^53\mathrm{ d}~^3\mathrm{ D}^o_1$ . However, the collision ionization cross-section of a 2p electron from the ground level of Fe 16+ is increased by 500 per cent and 100 per cent under an incident electron energy of 1500 and 10 000 eV, respectively. This results in the rate coefficient increasing by a factor of 18.5 at a temperature of 200 eV and density of 15.748 g cm −3 .