Silicon is present in stellar atmospheres and important for the consideration of physical processes in stellar plasmas. Data on its spectral lines, as well as on spectral lines from its various ionization stages are consequently of particular astrophysical interest. Stark broadening parameters of Si XI and Si XIII spectral lines are important not only for astrophysics, as e.g. for the consideration of radiative transfer through subphotospheric layers, but also for the fusion plasmas and laser produced plasmas research. The development of soft X-ray lasers, where Stark broadening data are needed to calculate gain values, model radiation trapping and to consider photoresonant pumping schemes (see e.g. Griem & Moreno 1990; Fill & Schöning 1994), provided an additional interest for such results.
This paper is the eighteenth of a series devoted to the investigation of Stark broadening parameters of spectral lines of multicharged ions (see Dimitrijevic & Sahal-Bréchot 1995 and references therein, as well as Dimitrijevic & Sahal-Bréchot 1996a,b, 1997a,b). As a continuation of our programme (see e.g. Dimitrijevic 1996) to obtain as large as possible set of reliable Stark broadening data needed for the consideration and modeling of astrophysical and laboratory plasmas as well as laser produced and fusion plasmas, and plasmas in various plasma devices in technology, we have calculated within the semiclassical-perturbation formalism (Sahal-Bréchot 1969a,b), electron-, proton-, and He III-impact line widths and shifts for 4 Si XI and 61 Si XIII multiplets. These data, together with Stark broadening data for Si IV (Dimitrijevic et al. 1991b,c) and Si XII (Dimitrijevic & Sahal-Bréchot 1993, 1994) will complete availlable results of large-scale Stark broadening calculations for multicharged silicon ion lines.