Electron scattering cross sections for the modelling of oxygen-containing plasmas*

This work proposes a set of electron scattering cross sections for molecular and atomic oxygen, with interest for the modelling of oxygen-containing plasmas. These cross sections, compiled for kinetic energies up to 1 keV, are part of the IST-LISBON database with LXCat, being used as input data to the LoKI (LisbOn KInetics) numerical code. The cross sections for ground-state molecular oxygen describe elastic and inelastic collision mechanisms, the latter including rotational excitations/de-excitations (treated using either a discrete or a continuous approach), vibrational and electronic excitations (including dissociation), dissociative attachment and ionisation. This set yields calculated swarm parameters that reproduce measurements within 5–20% (transport parameters) and within a factor of 2 difference (Townsend coefficients), for reduced electric fields in the range 10 -3 –10 3  Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O( 3 P) ground-state, dissociation of O 2 (X,a,b) (including dissociative ionisation and attachment) and of O 3 , and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O(( 4 S 0 )3 p 5 P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N 2 : 20% O 2 ), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary ( R = 345  μ m) at low pressure ( p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ∼1.5.