Jacek Halenka

Calibration of the width of the NI spectral line at 7915.42 Å for electron density determination

Abstract The Stark broadening of a NI spectral line at 7915.42 A has been calibrated for electron density determination of low temperature plasmas. The determined simple formula based on measured FWHM is applicable in the electron density range from 3×1015 to 10 16 cm −3 .

Analysis of the accuracy of computer simulations in calculations of the Stark broadening of hydrogen Lyα, Lyβ and Lyγ lines in plasmas

Abstract An analysis of the accuracy of numerical methods and physical models, applied in computer simulations of hydrogen line profiles, formed in plasmas, has been carried out. An electric microfield model has been proposed, reproducing the real microfields not worse than other hitherto existing models. The use of our model allows shortening the calculation time for a profile by a factor of three. The numerical code developed for this purpose allows one to control the accuracy of the simulation procedure. We present line profile results for Ly α , Ly β and Ly γ , which have been calculated with an accuracy being not worse than 3%. The results have been compared with other theoretical and experimental data.

PRESSURE SHIFT AND GRAVITATIONAL REDSHIFT OF BALMER LINES IN WHITE DWARFS: REDISCUSSION*

The Stark-induced shift and asymmetry, the so-called pressure shift (PS) of Hα and Hβ Balmer lines in spectra of DA white dwarfs (WDs), have been examined in detail as masking effects in measurements of the gravitational redshift in WDs. The results are compared with our earlier ones from a quarter of a century ago. In these earlier papers, the standard, symmetrical Stark line profiles, as a dominant constituent of the Balmer line profiles but shifted as a whole by the PS effect, were applied to all spectrally active layers of the WD atmosphere. At present, in each of the WD layers, the Stark line profiles (especially of Hβ) are inherently asymmetrical and shifted due to the effects of strong inhomogeneity of the perturbing fields in plasma. To calculate the Stark line profiles in successive layers of the WD atmosphere we used the modified Full Computer Simulation Method, able to take adequately into account the complexity of local elementary quantum processes in plasma. In the case of the Hα line, the present value of Stark-induced shift of the synthetic Hα line profile is about half the previous one and it is negligible in comparison with the gravitational redshift. In the case of the Hβ line, the present value of Stark-induced shift of the synthetic Hβ line profile is about twice the previous one. The source of this extra shift is the asymmetry of Hβ peaks.

On importance of the divergence of ionic microfields in plasmas for the shift and asymmetry of hydrogen spectral lines

It is shown that the contribution of the term proportional to the divergence of the ionic microfield to the total ionic shift and asymmetry of hydrogen lines is small compared to the others.

Perturber's charge effect on Stark broadened hydrogen lines in helium plasmas

Abstract The Stark line profiles for hydrogen Ly α , Ly β , Hα, and Hβ are calculated using the computer simulation method for helium plasmas in the range of electron concentration from 1018 to 10 19 cm −3 at increasing temperature values kT from 7 to 10 eV , according to the experimental measurements in dense plasmas (Bochum experiment). The calculation was carried out at two limiting assumptions about the perturbers: (a) in the helium plasma only singly ionized helium ions occur, and (b) in the plasma the doubly ionized ions exclusively exist. In the paper the ratio of the calculated full half-widths, FWHM(b)/FWHM(a), for these lines are presented. The ratio equals about to 1.1 for Lyβ and Hβ lines, about 1.0 for Hα, and about 0.9 for Lyα line.

The shift of Stark broadened Hγ line

Line profile of Hγ have been measured at low electron densities and parameters of the line shift have been determined. The experimental results have been compared with calculated ones.