Luminescence of argon in a spatially stabilized mono-filamentary dielectric barrier micro-discharge: spectroscopic and kinetic analysis

Abstract

The experimental work reported here is devoted to the temporal behaviour of a mono-filamentary dielectric barrier discharge in pure argon, from 100 to 700 Torr. A sinusoidal voltage supply is used, its frequency ranging from 10 to 90 kHz. An anode avalanche followed by a cathode streamer as well as the spatial stability of the micro-discharge is clearly seen in successive 3-ns snapshots in the visible range. Near the cathode, its diameter is about 0.2 mm, at 400 Torr. The electrical characteristics of the discharge are also evaluated, in particular the breakdown voltage and the energy deposited in the micro-discharge. The light output in the vacuum ultraviolet range is essentially due to the second continuum of argon, centred at 130 nm. The kinetic study of this continuum shows that primary excitation of the lowest argon atomic 4s and 4s′ states is practically achieved after 120 ns since beyond that time the luminescence decay of the second continuum is fairly described by only two exponential terms. So collisions between excited states, electronic collisions, and recombination of ionic species do not contribute significantly to this luminescence, after 120 ns. Surprisingly, we do not observe the contribution of the Ar(3P1) resonant state in the production of the argon excimers. The radiative lifetime of the Ar2[1u(3P2)]low v excimer ((3.18 ± 0.03) µs) and the three-body rate constant relative to the decay of the Ar(3P2) metastable state ((13.2 ± 0.9) Torr−2 s−1) leading to the formation of Ar2[1u(3P2)], are estimated. These results are consistent with those found from the literature. A simple kinetic scheme is proposed for times later than 120 ns.