2 Results and discussion

Calculations have been performed within the frame of the semiclassical perturbation formalism, which, as well as the corresponding computer code (Sahal-Bréchot 1969a,b), have been updated and improved several times (Sahal-Bréchot 1974; Fleurier et al. 1977; Dimitrijevi & Sahal-Bréchot 1984; Dimitrijevi et al. 1991; Dimitrijevi & Sahal-Bréchot 1996b). Short reviews of the semiclassical perturbation method used here, have been published several times as e.g. in Dimitrijevi & Sahal-Bréchot (1996c) and Dimitrijevi (1996). The atomic energy levels of Na X needed for calculations, have been taken from Martin & Zalubas (1981). The oscillator strengths have been calculated within the Coulomb approximation (Bates & Damgaard 1949, and the tables of Oertel & Shomo 1968). For higher levels, the method of Van Regemorter et al. (1979) has been used.

Our results for electron-, proton-, and He II-impact line widths and shifts for 57 Na X multiplets are shown in Table 1 (accessible only in electronic form), for perturber densities 10¹⁷-10²⁴ cm^-3 and temperatures T = 200 000 - 5 000 000 K. The complete set of data is given for the perturber density of 10¹⁹ cm^-3, while for lower densities, only data needed for better interpolation are given. Stark broadening parameters for densities lower than tabulated, or for transitions not tabulated for perturber densities lower than 10¹⁹ cm^-3, are proportional to the perturber density. We present in Table 1 as well, a parameter c (Dimitrijevi & Sahal-Bréchot 1984), which gives an estimate for the maximum perturber density for which the line may be treated as isolated, when it is divided by the corresponding full width at half maximum. For each value given in Table 1, the collision volume (V) multiplied by the perturber density (N) is much less than one and the impact approximation is valid (Sahal-Bréchot 1969a,b). Values for NV > 0.5 are not given and values for $0.1 < NV \le 0.5$ are denoted by an asterisk. When the impact approximation is not valid, the ion broadening contribution may be estimated by using the quasistatic approach (Sahal-Bréchot 1991 or Griem 1974). In the region between where neither of these two approximations is valid, a unified type theory should be used. For example in Barnard et al. (1974), a simple analytical formula for such a case is given. The accuracy of the results obtained decreases when broadening by ion interactions becomes important.

Acknowledgements

This work is a part of the project "Astrometrical, Astrodynamical and Astrophysical Investigations", supported by Ministry of Science and Technology of Serbia.