Simultaneous measurement of nitrogen and hydrogen dissociation from vacuum ultraviolet self-absorption spectroscopy in a developing low temperature plasma at atmospheric pressure

摘要

We demonstrate a method for determining the dissociation density of N and H atoms present in a developing low temperature plasma, based on the emission and self-absorption of vacuum ultraviolet radiation produced from the plasma. Spark plasmas are produced via pulsed discharge in N2/H2 mixtures at atmospheric pressure, where information on the dissociated densities of the constituent gas molecules is desired without employing invasive diagnostic techniques. By analyzing the self-absorption line profile of 121.5?nm Lyman-α H radiation emitted within the first ～1.0?mm of plasma near the anode tip, a peak dissociated H atom concentration of 5.6?×?1017?cm-3 was observed ～100?ns into spark formation, with an estimated electron density of 2.65?×?1018?cm-3 determined from Stark broadening. Similarly, simultaneous line fitting of the N 120.0/124.3?nm emission profiles revealed a peak dissociated N atom concentration of 3.8?×?1017?cm-3 during the same discharge period.