Characterization of atmospheric electrodeless microwave plasma in nitrogen

In this study, we investigate atmospheric microwave plasmas produced without electrodes while having a larger plasma volume in pure nitrogen. Optical emission spectroscopy is conducted to measure the translational, rotational, and vibrational temperatures of the plasma. Subsequently, three-temperature plasma kinetic simulations that consider the trans-rotational, vibrational, and electron temperatures separately are developed and conducted to study reaction pathways that sustain the plasma. The translational, rotational, and vibrational temperatures of the plasma are found to be the same and reach approximately 6000 K independent of the flow rate. In the plasma region, the molecular nitrogen is found to be dissociated into atoms to a significant extent because of the high gas temperature, and the plasma is sustained via associative ionizations rather than the electron-impact ionizations.