Spectroscopic diagnostics and electric field measurements in the near-cathode region of an atmospheric pressure microplasma jet

Abstract

Linear Stark splitting of the H$_{\beta}$ Balmer line components and spatially resolved optical emission spectroscopy (OES) measurements were used to estimate the electric field gradient in the cathode sheath region (~70 μm long) of an atmospheric pressure direct current argon flow-stabilized microplasma jet. Also, plasma parameters in the negative glow region were investigated by both OES and electrical diagnostics. The microplasma jet was operated for current ranging from 10 to 110 mA. OH (A ² ${\rm\Sigma}^+$, v = 0 $\to$ X ² ${\rm\Pi}$, v’ = 0) rotational bands at 306.357 nm and also the Ar 603.213 nm line were used to determine the gas temperature, which ranges from 600 to 1000 K. Electron number density, ranging from 4.1 × 10¹⁴ to 8.5 × 10¹⁴ cm^-3, was determined through analysis of the H$_{\beta}$ line. Electron excitation temperature was also measured from the ratio of two Mo lines (8500–18 000 K) and from Boltzmann-plot of Ar 4p–4s and 5p–4s transitions (11 000–13 500 K).