Hβ Stark broadening in cold plasmas with low electron densities calibrated with Thomson scattering

Abstract

In the present work Stark broadening measurements have been carried out on low electron density (n e b 5·10 19 m −3) and (relatively) low gas temperature (T g b 1100 K) argon-hydrogen plasma, under low-intermediate pressure conditions (3 mbar-40 mbar). A line fitting procedure is used to separate the effects of the different broadening mechanisms (e.g. Doppler and instrumental broadening) from the Stark broadening. A Stark broadening theory is extrapolated to lower electron density values, below its theoretical validity regime. Thomson scattering measurements are used to calibrate and validate the procedure. The results show an agreement within 20%, what validates the use of this Stark broadening method under such low density conditions. It is also found that Stark broadened profiles cannot be assumed to be purely Lorentzian. Such an assumption would lead to an underestimation of the electron density. This implies that independent information on the gas temperature is needed to find the correct values of n e .

Electron density measurement in atmospheric pressure plasma jets: Stark broadening of hydrogenated and non-hydrogenated lines

“…As can be seen, as the ion temperature decreases, they begin to show a less dynamic behavior affecting the line shape. Finally, figure 12 shows the pure Stark profile at a lower electron density, close to some of the experimental conditions in [143]. As the electron density decreases, the Stark width of each component becomes of the order of, or smaller, than the separation between components for that density, and a higher structure of the line is observed.…”

“…Obviously, such a low electron density obtained through Stark broadening of the H β line without consideration of the fine structure of the line and ion dynamics can be used only as a rough and indicative value and as such requires additional confirmation by alternative methods. Some experimentalists [109,143] have employed approximate methods to obtain Stark profiles below the fine structure limits. In [143] a correction to the deconvolution procedure has been proposed in order to take into account the fine structure of the H β line.…”

“…Some experimentalists [109,143] have employed approximate methods to obtain Stark profiles below the fine structure limits. In [143] a correction to the deconvolution procedure has been proposed in order to take into account the fine structure of the H β line. The fine structure of H β has been convoluted with an instrumental function which was then used in the calculations.…”

Division B Commission 14 Working Group: Collision Processes

“…Also Stark broadening of H β has been investigated for cold plasmas with low electron densities (Palomares et al 2012).…”

Simple method for gas temperature determination in CO_2-containing discharges

“…The Hg line chosen for determination of the monochromator apparatus function is assumed to have (i) a spectral response similar to the one of the CO spectra (see Fig. 2), and (ii) Doppler, Stark and Van der Waals broadening much smaller than the instrumental broadening [14][15][16]. Based on Eq.…”