Stark broadening and regularities of prominent multiply ionized nitrogen spectral lines.

Abstract

Stark widths of four N ii, fourteen N iii, five N iv, and two N v spectral lines have been measured in a linear-pinch discharge plasma and compared with existing experimental and theoretical results. Electron densities determined with single-wavelength laser interferometry with use of the visible 632.8-nm transition of a He-Ne laser cover the range of (0.40--1.80)\ifmmode\times\else\texttimes\fi{}${10}^{23}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$. The electron temperature of 50 000 K was determined from the Boltzmann slope of several N iii spectral lines, and from the relative intensity ratios of several N ii to N iii and N iii to N iv spectral lines. Since the majority of investigated N iii spectral lines originate from the 3s-3p and 3p-3d transition arrays, the Stark-width (w) dependence on the upper level ionization potential (I) of corresponding lines belonging to these two transition arrays was discussed and found to be of the form w=${\mathrm{aI}}^{\mathrm{\ensuremath{-}}b}$, where a and b are constants independent of the ionization potential. Similarly, the overall Stark width trends, using data obtained from the 3s-3p transition of the N ii, N iii, N iv, and N v spectral lines, were determined and discussed including the influence of emitter net charge on the Stark broadening dependence on the upper-level ionization potential. The established overall trend was used to predict the Stark width of uninvestigated spectral lines originating from the given 3s-3p transition with an accuracy better than 30%.