Reaction kinetics of a high pressure helium fast discharge afterglow

Journal Article · Thu Apr 15 00:00:00 EST 1982 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.443521· OSTI ID:5576348

Stevefelt, J; Pouvesle, J M; Bouchoule, A

This work reports the study of elementary processes which govern the relaxation of the afterglow of a 3 kA 7 ns duration discharge in helium at atmospheric pressure. Populations of the dominant energy storing species were monitored as functions of time through measurements of the emission asnd absorption of radiation from the plasma. The atomic helium spectral lines, radiated during the discharge pulse, were found to rapidly transform into molecular helium bands in the visible and far ultraviolet (600--1000 A) regions during the afterglow. The observed features of this He/sub 2/ radiation were consistent with a collisional-radiative scheme of electronic recombination of molecular He/sub 2//sup +/ ions, the concentration of which was inferred from H/sub ..beta../ line broadening. A significant fraction of the He/sup +//sub 2/ recombination events were found to result in helium atoms in the metastable 2 /sup 3/S state, and the time dependence of this dissociation process correlated with that of He/sub 2/ populations characterized by quantum number n = 4. The concentration of 2 /sup 3/S atoms was comparable to the electron density, ranging from 10/sup 14/ to 10/sup 15/ cm/sup -3/. The concentration of molecular a /sup 3/..sigma../sup +//sub u/ metastables was found to be one order of magnitude lower, suggesting a collisional coupling to the radiating A /sup 1/..sigma../sup +//sub u/ state. From the data rate coefficients have been extracted for the processes of electron--ion recombination, ionizing collisions between atomic metastables, and superelastic electron--metastable collisions.

• Research Organization: G.R.E.M.I., University of Orleans, 45046 Orleans Cedex, France
• OSTI ID: 5576348
• Journal Information: J. Chem. Phys.; (United States), Vol. 76:8
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
AFTERGLOW
CHEMICAL REACTION KINETICS
HELIUM
RECOMBINATION
ABSORPTION SPECTRA
ELECTRIC DISCHARGES
EMISSION SPECTRA
HELIUM IONS
METASTABLE STATES
RELAXATION
CHARGED PARTICLES
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
GASES
IONS
KINETICS
NONMETALS
RARE GASES
REACTION KINETICS
SPECTRA
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory