Stark broadening of lines from transition between statesn = 3 ton = 2 in neutral helium

Abstract

Context. The Stark broadening of the spectral lines of the wavelengths 501. 6, 667.8, 728.1, 388.9, 587.6, and 706.5 nm from neutral helium in plasmas are studied theoretically and experimentally. Aims. The aim of this work is to provide information about the connection between the shape and width of spectral lines and the electron density and temperature to be used as a diagnostic tool. Methods. The theoretical calculations were carried out through molecular dynamics computer simulations with noninteracting particles. The experimental measurements were done in a plasma of pure helium generated in an electromagnetically driven T-tube. The plasma diagnostics used previous results about the Stark broadening of the He I 447.1 nm and He I 492.2 nm lines and the coherence between the shape of these spectra and those obtained here. The electron temperature was obtained through a Boltzmann-plot of eight lines of Si II. Results. Several tables of width and shift are provided in a wide range of electron density and temperature. Furthermore, we supply several fitting formulas, which allow calculating the plasma electron density from the measured values of the spectral line widths. The results obtained in the laboratory and in the simulations are compared with the data from the literature.

Measurement of Stark Halfwidths of Spectral Lines of Ionized Oxygen and Silicon Emitted from T-tube Plasma

“…The presence of O II, Si II and Si III spectral lines in our experiments was first observed in the spectra emitted from the T-tube while using pure helium as the working gas [34,35]. Oxygen and silicon occur in our plasma as impurities originating from the glass walls of the discharge vessel.…”

Influence of Longitudinal Magnetic Field in the MPC Channel on the Density of Generated Plasma Stream

“…The analysis of the Stark-broadening spectral lines is one of the widely used plasma diagnostics techniques, especially formonitoring of the plasma electron density [15]. Distributions of plasma electron density N e (L) were obtained in the plasma stream and, in particular, in compression zone using Stark broadening of He I and He II spectral lines after the procedure of instrumental broadening exception (∆λ i = 0.2 Å).…”

“…3 shows the comparison of experimental and theoretical shapes of the He II (4685 Å) and He I (4471 Å) spectral lines. Presumably spectral lines of different ionization stages characterize different parts of plasma stream, so analysis of both contours provides more complete data about plasma density [15,16]. It must be pointed out that the fitting result includes only the purely Lorentz component of the spectral lines contour, excluding Gaussian one.…”

Spectral Line Shapes of He I Line 3889 Å

“…However, for strongly interacting plasmas (large plasma coupling parameter) or charged emitters, MD simulations accounting for the interactions between all the particles in the plasma (i.e., including the emitter) are required [48,49], though for the calculations in this work the independent particles technique was accurate enough. More details of the calculation can be seen in [11].…”

“…Several theoretical approaches have been applied to calculate Stark broadening, such as the well known semiclassical approximation the standard theory (ST) by Griem [1], or the quantum statistical approach of many-particle theory [2], where the motion of ion perturber is neglected during the inverse halfwidth of the line. Furthermore, the model microfield method (MMM) [3][4][5][6], the frequency fluctuation method (FFM) [7] or computer simulations [8][9][10][11] are used for calculating the line broadening including ion-dynamics effects, which lead to further broadening of the line shapes.…”