1 Introduction

The investigation of the influence of impacts with charged particles (Stark broadening) on spectral line shapes of oxygen and magnesium in various ionization stages is of importance for a number of problems in astrophysics, physics and technology. For example, Stark broadening parameters for such ions are needed for the modeling and theoretical considerations of subphotospheric layers (Seaton 1987), for stellar abundance determinations, opacity calculations, diagnostic of laser produced, fusion and laboratory plasmas. Data on O VII spectral lines are of interest for the interpretation and modelling of some hot star spectra as PG1159 type stars (Werner et al. 1991). The additional interest for such data is due to 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).

This paper is the twentieth of a series devoted to the research 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, 1997, 1998a-d). Within the frame of our project (see e.g. Dimitrijevic 1996) to obtain as large as possible set of reliable semiclassical Stark broadening data needed for the investigation, diagnostics and modeling of various plasmas in stellar and solar physics, laboratory, laser physics, fusion research, and various devices, we have calculated within the semiclassical-perturbation formalism (Sahal-Bréchot 1969a,b), electron-, proton-, and He III-impact line widths and shifts for 14 O VII and 18 Mg XI multiplets.