Atomic Density Measurements in Nitrogen, Oxygen, and Hydrogen Afterglow Plasmas PDF Download

Author: Ewen Austin McLennan
Publisher:
ISBN:
Category : Atoms
Languages : en
Pages : 168

Get Book Here

Book Description
Densities of ground-state N, O and H atoms, formed by dissociation of the parent molecular gases in dc and rf discharges, were measured over the range 10 to the 10th power to 10 to the 16th power/cc. Sensitive and unambiguous measurements that did not disturb the system under study were made by electron spin resonance (ESR) and atomic resonance absorption spectroscopy (RAS). Quantitative measurements were made by calibration of the atomic ESR resonance lines against an O2 ESR resonance line standard. Densities determined by ESR and by gas titration agreed within 20 per cent. Densities of ground -state atoms were investigated in the afterglows of pulsed and continuous rf discharges, and pulsed dc discharges, in both stationary and flowing gases. Dissociation of the parent molecular gas was found to be a strong function of the type of discharge and of the gas impurity content: rf discharges in gases with a few tenths per cent H2O impurity typically produced four orders of magnitude more atoms than did pulsed dc discharges in 'pure' gases. Atomic densities were measurable up to 10 sec in rf discharge afterglows. The slow recombination of the atoms provides a long-lived energy source throughout the afterglow. Experiments were performed to show that the concentration of N atoms in the afterglow of a pulsed dc discharge in N2 markedly affects the electron density, temperature, and collision frequency.