Density measurements from the asymmetry of the Lyman xi line in a vacuum spark lithium discharge

A lithium spectrum is obtained form vacuum spark discharges using a grazing -incidence flat;field spectrometer. Hydrogen-like lines up to Lyman eta are identified in the spectrum. The spectrum is analyzed, and it is found that the experimental line widths increase along the Lyman series. An asymmetry between the blue and red wings appears in the profile of the Lyman epsilon line, and becomes significant in the profile of the Lyman xi line. A relat ively new method is used to estimate an electron density of 1 +/- 0.4 x 10( 18) cm(-3) from the experimental degree of asymmetry between the blue and t he red wings of the Lyman xi line. This result is compared with an analysis of the experimental widths of two optically thin lines, namely, Lyman delt a and Lyman xi. In this analysis an electron density of 1.2 +/- 0.5 x 10(18 ) cm(-3) is deduced. The principal quantum number of Lyman eta (n=8) is use d in the Inglis-Teller formula for the last line seen before the merging of the lines with the continuum, and the estimated electron density is found to be 2.0 x 10(18) cm(-3) for the lithium plasma. Thus, it is demonstrated that the new method employing the asymmetry of the lineshapes in dense plas mas yields results consistent with the analysis of the widths of the lines. However, it requires obtaining the profile of just one spectral line, whic h is a great advantage. The reference data on the Stark broadening of the L yman xi line is also tabulated, which was previously unavailable in the lit erature.