The spectroscopic investigation of broad C I and C II lines emitted from pulsed atmospheric pressure gas discharge source in argon and argon‑hydrogen mixture

Abstract

The spectroscopic investigation of pulsed atmospheric pressure needle-to-cylinder (NTC) gas discharge source with graphite cathode in argon and argon‑hydrogen mixture is performed. Numerous C2 molecular bands, of interest for rotational temperature Trot measurement, are recorded in the optical region of NTC discharge spectrum. Due to strong interference with C2 bands, the full set of C I and C II lines are not recorded. Nevertheless, we succeeded to obtain the spectra of broad C I multiplet at 477.0 nm, C II 274.7 nm line, and C II doublet at 283.7 nm. In addition, the hill-shaped-spectrum is recorded in the range 709–714 nm which is most probably the superposition of broad C II lines. Applying the appropriate fitting function on C II lines, the Stark broadening full-width-at-half-maximum (FWHM) is obtained and electron number density Ne estimated. The gas temperature Tg = 3500–4500 K, an important parameter for Ne diagnostics, is estimated from Trot calculated using C2, CH and CN molecular bands in the course of this study. The Ne ≈ 3 × 1016 cm−3 and Ne ≈ 1.5 × 1017 cm−3 are determined, which is consistent with our previous study with brass and stainless steel cathode NTC gas discharge.