Surface recombination in Pyrex in oxygen DC glow discharges: mesoscopic modelling and comparison with experiments

Surface recombination in an oxygen DC glow discharge in a Pyrex (borosilicate glass) tube is studied via mesoscopic modelling and comparison with measurements of recombination probability. A total of 106 experimental conditions are assessed, with discharge current varying between 10 and 40 mA, pressure values ranging between 0.75 and 10 Torr, and fixed outer wall temperatures (Tw) of −20, 5, 25 and 50 ºC. The model includes O+O and O+O2 surface recombination reactions and a Tw dependent desorption frequency. The model is validated for all the 106 studied conditions and intends to have predictive capabilities. The analysis of the simulation results highlights that for Tw = −20 ºC and Tw = 5 ºC the dominant recombination mechanisms involve physisorbed oxygen atoms (OF) in Langmuir-Hinshelwood (L-H) recombination OF + OF and in Eley-Rideal (E-R) recombination O2 + OF, while for Tw = 25 ºC and Tw = 50 ºC processes involving chemisorbed oxygen atoms (OS) in E-R O + OS and L-H OF + OS also play a relevant role. A discussion is taken on the relevant recombination mechanisms and on ozone wall production, with relevance for higher pressure regimes.