Relativistic eigenchannel R-matrix studies of the strong intrashell electron correlations in highly charged Ar13+ ions

Highly charged ion systems play an important role in simulation and diagnostics of astrophysical and fusion plasmas. Due to dominant strong Coulomb interactions from the nuclear charge, electron correlations are generally thought to be less prominent than relativistic effects and other effects in HCIs. In this paper, we demonstrate the importance of strong intrashell electron correlations from the quasidegeneracy of $2s, 2p$ orbitals in highly charged B-like ${\mathrm{Ar}}^{13+}$ ions. Such strong intrashell electron interactions manifest as an atomic system with many channel interactions, which will ultimately form a much more complex atomic spectrum than the neutral B atom in the isoelectronic sequence. As a typical example, the relativistic eigenchannel $R$-matrix method (R-R-eigen code) was successfully applied to investigate the complex spectrum of ${\mathrm{Ar}}^{13+}$ ions with ${J}^{\ensuremath{\pi}}=1.{5}^{+}$ symmetry in discrete and autoionization regions. Calculated results obviously show interesting behaviors of strong intrashell electron correlations in HCIs. Additionally, it is also beneficial to understand discrepancies in the low-energy electron-ion recombination spectra of Be-like ${\mathrm{Ar}}^{14+}$ ions between experimental observations at the main cooler-storage ring of the Heavy Ion Research Facility in Lanzhou and distorted wave calculation.