Assessing the role of surface and volume processes for atomic oxygen losses in CO2 glow discharges in Pyrex

This work examines how to estimate an effective O(3P) surface recombination probability γO in CO2 plasmas in Pyrex from the temporal evolution of its density, measured in modulated current conditions in DC glow discharges. Zero-dimensional simulations are used under steady-state and current modulation conditions to analyse experimental data available for pressures in the range 0.2-5 Torr and currents between 10 mA and 50 mA. It is shown that the estimation of γO is simpler in CO2 than in O2, as in the former case it can be realistically estimated by assuming that the net losses of O(3P) correspond to surface recombination losses only, while in the latter case volume recombination and flow losses have to be additionally taken into account.