Neutral gas temperature estimates and metastable resonance energy transfer for argon-nitrogen discharges

Rovibrational spectroscopy band fitting of the nitrogen (N₂) second positive system is a technique used to estimate the neutral gas temperature of N₂ discharges, or atomic discharges with trace amounts of a N₂ added. For mixtures involving argon and N₂, resonant energy transfer between argon metastable atoms (Ar∗) and N₂ molecules may affect gas temperature estimates made using the second positive system. The effect of Ar∗ resonance energy transfer is investigated here by analyzing neutral gas temperatures of argon-N₂ mixtures, for N₂ percentages from 1% to 100%. Neutral gas temperature estimates are higher than expected for mixtures involving greater than 5% N₂ addition, but are reasonable for argon with less than 5% N₂ addition when compared with an analytic model for ion-neutral charge exchange collisional heating. Additional spatiotemporal investigations into neutral gas temperature estimates with 10% N₂ addition demonstrate that although absolute temperature values may be affected by Ar∗ resonant energy transfer, spatiotemporal trends may still be used to accurately diagnose the discharge.