Energy efficiency of N₂ vibrational excitation in the spark-and-glow phases of a long-pulse air discharge at atmospheric pressure

Abstract

The vibrational excitation of N2 molecules has a significant impact on plasma chemical synthesis, including nitrogen fixation and ammonia formation, by reducing the energy barrier of chemical reactions. However, experimental data for energy efficiency of N2 vibrational excitation is very rare. In this work, vibrational coherent anti-stokes Raman scattering (CARS) was applied to a 200 μs long-pulse air plasma, and the time behaviours of rotational and vibrational temperatures of N2 in two different discharge modes, namely the spark and glow modes in the long discharge pulse, were quantified. It reveals that the spark discharge produced a vibrational temperature exceeding 5000 K but with a gas temperature as low as 400 K, while the glow discharge resulted in efficient gas heating with a gas temperature as high as 3500 K and a vibrational temperature higher than 5000 K. Combined with the 0D simulation of the air plasma, it demonstrates that the energy efficiency of N2 vibrational excitation in the glow phase is about three times higher than that of the spark phase. These results provide essential inspiration for further studies of plasma chemical synthesis dominated by N2 vibrational excitation.

Assessing the efficacy of an atmospheric air DC glow discharge system for sustainable nitrogen fixation: a vibrational coherent anti-Stokes Raman scattering study

“…The CARS spectroscopy involves the interaction of three beams, namely the pump, Stokes, and probe, with a molecule, generating the fourth signal beam, namely the anti-Stokes beam. The optical setup of CARS measurement in this work, similar to the one used in our previous work [40], is illustrated in figure 1. Briefly summarized, the second harmonic of a Nd:YAG laser (532 nm, Beamtech, Dawa 200, 7 ns FWHM, 20 Hz repetition rate) was divided into two parts; one was used to pump a broadband dye laser, while the other was divided further to serve as pump or probe beam for CARS measurement.…”

Dynamic climbing behavior and self-extinction mechanism of DC arc in a gradually changed air gap

“…In addition, other researches were also carried out in the aspect of arc emission spectrum to analyze arc physical parameters, such as excitation temperature and electron density. Jun-Jie Qiao conducted some experiments, in which the vibrational coherent anti-Stokes Raman scattering was applied to a 200 μs long-pulse air plasma, and the time behaviours of rotational and vibrational temperatures of N 2 in two different discharge modes were quantified [17]. T. Namihira measured the temperature and electron density of a pulsed discharge plasma which was produced under water.…”