O2 X, a and b densities and kinetics in pure O2 DC discharges: VUV absorption, IR emission and Cavity Ring Down Spectroscopy measurements
Résumé
O2 metastable a and b states are important reactive intermediates in O2 plasmas. We have measured their density and kinetics in a uniform positive column DC discharge in a thermostated Pyrex tube. The DESIRS FTS was used to measure high resolution VUV absorption spectra of O2 X, a and b in steady state discharge. The a state density was also measured by CRDS, and the b state by absolute IR emission measurements, allowing the VUV absorption cross-sections to be determined, and compared to ab-initio calculations. Using monochromatic VUV absorption the kinetics of the three states was monitored in pulse-modulated discharges to probe their loss processes over the pressure range .2-7.5 Torr and discharge current 10-40mA.