SIMBAD references

The neutral and ionized silicon spectral line shapes have been investigated in the laboratory helium plasma at electron densities ranging between 3.7x10²²m^–3 and 1.1x10²³m^–3 and electron temperatures between 12500K and 19000K, both interesting for astrophysics. The aim of this work is to present experimental Stark FWHM (full-width at half of the maximum line intensity, W) for number of spectral lines from neutral (SiI), singly (SiII), doubly (SiIII), and triply (SiIV) ionized silicon spectra emitted by the pulsed helium discharge, which is optically thin at the wavelengths of the investigated ionic silicon lines. A specific method for estimating self-absorbtion is presented in detail. For investigated SiI spectral lines, applying the proposed method, an optical depth of less than 0.38 is found. Appropriate corrections of the SiI Stark widths were made. The Stark widths of different ionic species, presented in this paper, are measured for the first time in the essentially same laboratory plasma. The silicon atoms were evaporated from the walls of the specially designed pyrex discharge tube in the pulsed helium discharge at a pressure of 665 Pa in a flowing regime. The SiI, SiII, SiIII, and SiIV spectral line profiles were recorded using the McPherson model 209 spectrograph and the Andor ICCD camera as the detection system. The Stark FWHMs of 13 SiI, 15 SiII, 28 SiIII, and 9 SiIV spectral lines were measured in the wavelength interval between 206nm and 640nm. Five SiI, four SiII, eleven SiIII, and one SiIV W values from the above set not had measured or calculated. Our W values are compared with the existing theoretical and experimental data. At the mentioned plasma parameters tolerable agreement was found (within the accuracy of the experiment and uncertainties of the theoretical approaches used) between measured and calculated Stark FWHM values. We recommend the Stark FWHMs of the intense 254.182nm, 308.624nm, and 309.342nm SiIII, and 314.956nm and also 316.571nm SiIV lines for the plasma diagnostic purposes.