Determination of absolute O(3P) and O2(a1Δg) densities and kinetics in fully modulated O2 dc glow discharges from the O2(X3Σg-) afterglow recovery dynamics - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Plasma Sources Science and Technology Année : 2020

Determination of absolute O(3P) and O2(a1Δg) densities and kinetics in fully modulated O2 dc glow discharges from the O2(X3Σg-) afterglow recovery dynamics

Résumé

A method is presented for the determination of the absolute densities of O(3P) atoms and O2(a1Δg) molecules in an O2 electrical discharge, which does not depend on any calibration procedure or knowledge of optical transition strengths. It is based on observing the recovery dynamics of the O2(X3Σg -) density in the afterglow of a fully-modulated discharge, and is demonstrated in a dc glow discharge in pure О2 at pressures of 0.2-4 Torr. The time-resolved O2(X3Σg -) density was measured by VUV absorption spectroscopy using the monochromator branch of the VUV DESIRS beamline at Synchrotron SOLEIL, but this methodology could be used with another density measurement technique. During the active discharge, the O2(X3Σg -) density is depleted by a combination of О2 dissociation, excitation into metastable states (principally (a1Δg) ) and gas heating/dilation. After discharge extinction, the O2(X3Σg -) density progressively recovers to its initial (before discharge) value, with three distinct time-constants due to: i) gas cooling (fast), ii) O(3P) atom recombination (intermediate), and iii)O2(a1Δg) quenching (slow). The O(3P) and O2(a1Δg) dynamics can be separated easily, allowing the O(3P) and O2(a1Δg) afterglow loss kinetics to be determined, as well as their mole fractions in the steady-state discharge. Both the O(3P) and (a1Δg) mole-fractions increase with current (up to the highest current studied, 40 mA) and pass through maxima with pressure at 1 Torr, reaching 16.5% and 8%, respectively. O(3P) atoms are principally lost by recombination at the borosilicate tube surface, with a loss probability in the afterglow of ~8x10-4, nearly independent of gas pressure and discharge current (in contrast to previous observations in the active discharge [1] . The (a1Δg) dynamics were also measured by IR emission spectroscopy. In the late afterglow this agrees well with the O2(X3Σg -) recovery dynamics, corresponding to an (a1Δg) surface loss probability of ~2.2x10-4. The initial (a1Δg) loss is faster than in the later afterglow, indicating that it is also quenched by O atoms.
Fichier principal
Vignette du fichier
O2_VUV_revised August 2020.pdf (2.72 Mo) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)

Dates et versions

hal-02933186 , version 1 (08-09-2020)

Identifiants

Citer

Jean-Paul Booth, Abhyuday Chatterjee, Olivier Guaitella, Joao Santos Sousa, Dmitry Lopaev, et al.. Determination of absolute O(3P) and O2(a1Δg) densities and kinetics in fully modulated O2 dc glow discharges from the O2(X3Σg-) afterglow recovery dynamics. Plasma Sources Science and Technology, 2020, 29, pp.115009. ⟨10.1088/1361-6595/abb5e7⟩. ⟨hal-02933186⟩
89 Consultations
151 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More