Experimental Stark widths in the Pb IV and Pb V spectra

Context. The triply and fourthly ionized lead (Pb IV and Pb V, respectively) spectral line shapes have been investigated in the laboratory helium plasma at electron densities ranging between 5.1 x 10(22) m(-3) and 9.1 x 10(22) m(-3) and electron temperatures around 22 000 K (+/- 9%), both interesting for astrophysics. Aims. The aim of this work is to present experimental Stark FWHM (full-width at half of the maximum line intensity, W) for 34 spectral lines from Pb IV and 4 spectral lines from Pb V spectra emitted by the pulsed helium discharge, which is optically thin at the wavelengths of the investigated lines. The values presented in this paper are the first published experimental W data in the Pb IV and Pb V spectra. Methods. The lead atoms were sputtered from the cylindrical lead plates that are located in the homogenous part of the pulsed helium discharge at a pressure of 665 Pa in a flowing regime. The Pb IV and Pb V spectral line profiles were recorded using the McPherson model 209 spectrograph and the Andor ICCD camera as the detection system. Results. The Stark FWHMs of 34 Pb IV and 4 Pb V spectral lines were measured in the wavelength interval between 200 nm and 461 nm. Our experimental Pb IV W values are compared with the existing theoretical data. Twenty four Pb IV W values from the above mentioned set haven't been calculated so far. The isotope shift, caused by the four natural Pb isotopes, and the hyperfine structure have no influence on the observed symmetry of the measured Pb IV and Pb V line shapes at our plasma parameters. Conclusions. At the mentioned plasma parameters we found a tolerable agreement (within the accuracy of the experiment and uncertainties of the theoretical approaches used) between the measured and calculated ten Pb IV W values. For the Pb V spectral lines no comparison is possible because as far as we are aware, no experimental and theoretical W data exist.