Milan S Dimitrijević

In this work we studied the Stark widths of Ar iv ion which are important for modelling atmosphere of some particular stars. Using semiclassical perturbation and modified semi-empirical approach, we present in this work Stark widths of triply ionized argon Ar iv spectral lines which will be implemented in the STARK-B data base. Energy levels and oscillator strengths needed as input for Stark width calculations were obtained from the atomic structure data base TOPbase. If we need to interpolate these Stark widths at different temperatures for the studied transitions of Ar iv, we use a simple and accurate fitting formula based on a least-squares method. The calculated values were compared to the existing experimental and calculated Stark width values.

We provide in this paper new Stark broadening parameters for the four ions Ga IV, Ga V, Ge IV, and Ge V. The calculations have been performed using our quantum mechanical method. To the best of our knowledge, the only available Stark broadening results are those of the Ge IV ion, where the semiclassical perturbation and the modified semi-empirical methods have been used. For the three other ions, no data have been found. In 2020 and for the first time, about five hundred lines of trans-iron elements including gallium (Ga) and germanium (Ge) have been identified in the ultraviolet (UV) spectrum of a DAO-type white dwarf BD-22°3467. Other precedent observations showed the existence of Ga IV–V lines in two white dwarfs (G191-B2B and RE 0503-289), and those of Ge IV and Ge V in the UV spectrum of RE 0503-289. Theoretical evaluations and measurements of atomic and Stark broadening data are a pre-requisite for stellar-atmosphere modelling, which is a tool for the determination of the photospheric Ga and Ge abundance in white dwarfs. Since there is no Stark broadening data for the three ions Ga IV, Ga V, and Ge V, our calculations come to fill this gap, and the obtained results can be used for the abundance determination of elements, the calculation of stellar opacity, the interpretation and modelling of stellar spectra, and the estimation of the relative transfer through stellar plasmas. They will be also implemented into the data base of Stark broadening parameters, STARK-B.

Stark widths for 23 transitions in Al IV have been calculated by employing the modified semiempirical method. The results are obtained for an electron density of 1017 cm−3 and temperatures from 10,000 K to 160,000 K. The results obtained in this investigation are used for the examination of the influence of Stark broadening in Al IV stellar spectra, as well as to check the Stark width regular behavior and similarites within the Al IV spectrum.

We present in this paper new quantum Half Widths at Half intensity Maximum (HWHM) for 101 spectral lines of the following ions: O II (35 lines), O III (20 lines), Si II (9 lines), Si III (12 lines), and Al III (25 lines). The present quantum results are compared to new experimental ones. No previous quantum calculations have been performed for these ions. The relatively high differences found between the new and previous measurements and the available theoretical calculations encourage us to conduct these quantum calculations. Our quantum method has been used many years ago and has given good results compared to other approaches, so it can be a useful tool to check the new experimental results or to understand the disagreement found for some lines. Furthermore, the obtained results can be used for the abundance determination of elements, the calculation of stellar opacity, the interpretation and modelling of stellar spectra, and the estimation of the relative transfer through stellar plasmas, etc. Part of the present results will be also implemented to the data base of Stark broadening parameters STARK-B.