Kinetics of Ar^*₂in high-pressure pure argon

Abstract

The kinetics of argon dimer (Ar * 2) are studied in detail by model calculations. The model is applicable to discharge as well as e-beam excitation of high-pressure argon gas. The time-transient behaviour of the temperature and the vibration-translational relaxation of the excited state dimer have been considered in the model calculations. The model validity is verified by comparing the model predictions with discharge and e-beam experiments. Excellent agreement has been reached for the e-beam experiments. The predicted discharge voltage and current waveforms are in good agreement with the experiments of Ninomiya and Nakamura. The predicted net gain of 0.002 cm −1 at 3.5 atm is about three times smaller.

Atmospheric Pressure Low Temperature Direct Plasma Technology: Status and Challenges for Thin Film Deposition

“…For example, using noble gases, there is always a strong contribution of dimers, He 2 *or Ar 2 *. Indeed, at atmospheric pressure, and due to the formation of dimers, the lifetime of He(2 3 S) metastable decreases to 2 µs60 and that of Ar( 3 P) metastable decreases below 0.1 µs 61, 62. A direct consequence is that in Ar AP discharges, the [Ar 2 *]/[Ar*] ratio can be of several thousand,63 Ar 2 * becoming the main actor in the Penning ionization process.…”

“…A direct consequence is that in Ar AP discharges, the [Ar 2 *]/[Ar*] ratio can be of several thousand,63 Ar 2 * becoming the main actor in the Penning ionization process. Similarly to the other metastables states, neutral excimers can also play a dominant role some microseconds after the end of the discharge: for example the lifetime of Ar 2 *(3Σ u ) state at high pressure is longer than 3 µs 62…”

“…In noble gases, in the same way than for the neutral dimers, dimer ions are usually formed by a 3‐body reaction involving an atomic ion. This reaction rate can be really high: in Ar at atmospheric pressure and at room temperature, the dimer ion formation takes place in less than 10 ns 62. As a consequence, in noble gases, if the main ion is not the one created by Penning ionization, the dimer ion is usually dominant over the atomic ion.…”

“…Radiative dimers are at the origin of an important VUV radiation. This is particularly intense in Ar AP discharges where dimer radiative deexcitation leads to an emission centered at 126 nm 62. Moreover, resonant energy transfer from argon dimers to atomic oxygen impurities allows the emission of oxygen triplet lines around 130 nm 64–66…”

Atmospheric-pressure plasma jets: Effect of gas flow, active species, and snake-like bullet propagation

“…This species is quickly converted to the excited Ar 2 * through three-body collisions. Then, due to the short lifetime (less than 3.2 ls) of the excited Ar 2 * species, 37 it quickly quenches to the ground state by emitting a photon before the following discharge pulse. Hence, Ar m * species are also not the cause of the observed phenomenon.…”