Experimental study of a supersonic low-pressure nitrogen plasma jet

Abstract

A supersonic nitrogen arc plasma jet expanded in a low-pressure test chamber is studied. Radial measurements of temperatures and densities are performed in the expanding region over various sections from the nozzle exit. Nitrogen is highly dissociated in the arc chamber and the plasma is far from equilibrium. Electron temperature and density, as well as gas velocity, are measured by means of parallel and crossed electrostatic probes. Measurements of selected atomic and molecular line intensities are performed in the 250–850 nm spectral range to obtain number densities of various N2, N2+ and N excited levels. The rotationally resolved emission spectrum from the (0–0) band of the N2+ first negative system (B2Σ+u→X2Σ+g) is analyzed and compared to synthetic spectra to evaluate the rotational temperature within the flow field. The kinetic scheme of ionic recombination of N+ and N2+ is examined. A recombination path of the N2(C3Πu) electronic state via the N2(C″5Πu) state is proposed for the N(2D0)+N(4S0) nitrogen recombination.