MEASUREMENT OF THE GROUND-STATE AND METASTABLE ATOMIC NITROGEN NUMBERDENSITY IN A LOW-PRESSURE PLASMA-JET

The radial profiles of metastable and ground state atomic number densi ties at numerous sections of a supersonic nitrogen plasma jet have bee n derived from UV absorption and emission spectroscopy. An original me thod that provides the ground state number density from the ratio of t he intensities of the 119.955, 120.022 and 120.071 nm resonance lines has been developed. Along the jet axis direction, and similarly to the N and N-2(+) excited states, the N ground state density decreases mor e steeply at the centre of the jet than at its border. At the exit of the plasma source, our results throw doubt upon the nitrogen dissociat ion rate usually considered in the literature.