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Dielectronic recombination (DR) is an important atomic physics process that is relevant to astrophysical plasma modeling. DR is responsible for the charge state balance as well as the cooling of plasmas, and it is the dominant electron-ion recombination process for most ions in both photoionized and collisionally-ionized plasmas. Accurate and reliable calculations for DR rate coefficients are needed to analyze the spectra obtained from astrophysical observations. Over the past few years, our group has computed reliable DR and radiative recombination (RR) data for all isoelectronic sequences up through Mg-like ions using a state-of-the-art multi-configuration Breit-Pauli (MCBP) approach. Recently, we have focused our work on the complex third-row M-shell isoelectronic sequences, especially Al-like. Although there exist some DR calculations for S3+, those calculations were performed only within a non-relativistic LS-coupling approximation and for electron-ionized, higher temperatures. Fe13+ DR calculations have been completed and tested against the Heidelberg heavy-ion Test Storage Ring facility measurements. Semi-relativistic DR cross section and rate coefficient calculations for Al-like S3+ using the level-resolved distorted-wave AUTOSTRUCTURE program will be presented. The effect of ground-state fine structure on the DR rates will be discussed. These calculations include final-state-resolved partial DR and RR rate coefficients from the initial ground and metastable levels spanning a temperature range of 10 z2 K–107 z2 K, where z is the initial ionic charge. Our computed Maxwellian DR rate coefficients are fitted into a simple formula for efficient dissemination of data and ease of use in plasma modeling codes, and comparisons to existing data will be shown. [ABSTRACT FROM AUTHOR]

The hydrogen Balmer beta line is used as a plasma diagnostics tool for a long time. It is well known that the experimental profiles of Hβ line exhibit an asymmetry while some of most commonly used theoretical models, due to the employed approximations, give unshifted and symmetrical profiles [1, 2]. In the present work the central part of Hβ profile is reanalyzed experimentally and in terms of two theoretical approaches based correspondingly on the Standard Theory (ST) assumptions [3] and on the electric field computer simulation method [4, 5]. The present experimental and theoretical results are compared with the obtained earlier experimental [6–12] and theoretical data [13]. [ABSTRACT FROM AUTHOR]

The Standard Theory (ST) of hydrogen spectral lines Stark broadening is applied within many-body approach to detailed description of profile asymmetry simultaneously accounting for the quadrupole interaction, quadratic Stark effect shifts and corrections to oscillator strengths. The influence of electronic collision shifts and impact widths, trivial asymmetry, the Boltzmann and dipole intensity scaling factors are studied as well. The consistent inclusion of the latter two factors in ST frames requests the line contour redefinition to avoid divergence. It is demonstrated that the asymmetry of hydrogen spectral lines is the many-parametric sensitive function of broadening mechanisms. The comparison with the precision experiment on stabilized arc data for Hβ line has shown good coincidence within assumption of nonequilibrium between electrons and heavy neutral particles. [ABSTRACT FROM AUTHOR]