Microwave electrode discharge in nitrogen: Structure and characteristics of the electrode region

Abstract

The parameters of the electrode region of an electrode microwave discharge in nitrogen are studied by emission spectroscopy. The radial and axial distributions of the intensities of the bands of the second (N2(C3Πu → B3Πg)) and first (N2(B3Πg → A3Σu+)) positive systems of molecular nitrogen and the first negative system of nitrogen ions (N2+ (B2Σu+ → X2Σg+)), the radial profiles of the electric field E and the electron density Ne, and the absolute populations of the vibrational levels vC = 0–4 of the C3Πu excited state of N2 and the vibrational level vBi = 0 of the B2Σu+ excited state of a molecular nitrogen ion are determined. The population temperature of the first vibrational level TV of the ground electronic state X1Σg+ of N2 and the excitation temperature TC of the C3Πu state in the electrode region of the discharge are measured. The radius of the spherical region and the spatially integrated plasma emission spectra are studied as functions of the incident microwave power and gas pressure. A method for determining the electron density and the microwave field strength from the plasma emission characteristics is described in detail.