Fine-structure electric-dipole matrix elements of He-like ions for x-ray line-shape calculations

Dipole matrix elements have been calculated with different methods in the intermediate-coupling scheme to study their impact on the Stark effect of highly charged ions. Special emphasis has been devoted to the 1s3l fine structure of He-like ions that is widely employed for Stark broadening analysis in dense plasmas. Apart from a wavelength shift in the total He_β group in the x-ray energy range, important differences in the Stark width, induced line dips, and relative intensities of maxima are demonstrated for different methods of calculation. We found that these differences were related to the precision of the fine-structure dipole matrix elements and related wavelengths and explored the particularities of atomic structure precision for line broadening purposes that was distinct from the current database approaches. Based on advanced multi-configuration-Dirac-Fock simulations, we propose a complete set of high-precision matrix elements and wavelengths. Detailed numerical results are presented for He-like aluminum. We also discuss the influence of relativistic approximations in atomic structure on the line broadening.