Effects of helium gas mixing on the production of active species in nitrogen plasma

Optical emission spectroscopy is used to investigate the effects of helium gas mixing on the electron temperature and the production of active species in nitrogen plasma generated by 50 Hz pulsed-DC power source. The electron temperature is determined from He–I line intensities, using Boltzmann's plot method. The relative changes in the concentration of active species N2(C Πu3) and N+2(B Σu+2) are monitored by measuring the emission intensities of nitrogen (0–0) bands of the second positive and the first negative systems. It is found that the electron temperature can be raised considerably by mixing helium in nitrogen plasma, which in return plays a significant role in enhancing the concentration of active species through Penning effect of metastable states of the helium.