Eur. Phys. J. D (2016) 70: 124
https://doi.org/10.1140/epjd/e2016-70102-1

Regular Article

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

¹ Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
² Instituto Tecnológico da Aeronáutica, Departamento de Ciência e Tecnologia Aeroespacial, 12228-900, São José dos Campos, São Paulo, Brazil

^a e-mail: llalves@tecnico.ulisboa.pt

Received: 15 February 2016
Received in final form: 12 April 2016
Published online: 2 June 2016

Abstract

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^-3–10³ Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O(³P) ground-state, dissociation of O₂(X,a,b) (including dissociative ionisation and attachment) and of O₃, and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O((⁴S⁰)3p ⁵P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N₂: 20% O₂), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary (R = 345 μm) at low pressure (p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ∼1.5.