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

Abstract

Abstract 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 ( T w ) of −20, 5, 25 and 50 ∘ C . The model includes O+O and O+O2 surface recombination reactions and a T w 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 T w = − 20 ∘ C and T w = 5 ∘ C the dominant recombination mechanisms involve physisorbed oxygen atoms ( O F ) in Langmuir–Hinshelwood (L-H) recombination O F + O F and in Eley–Rideal (E-R) recombination O 2 + O F , while for T w = 25 ∘ C and T w = 50 ∘ C processes involving chemisorbed oxygen atoms ( O S ) in E-R O + O S and L-H O F + O S 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.