Electron impact cross sections for carbon monoxide and their importance in the electron kinetics of CO2–CO mixtures

Abstract

This work proposes a complete and consistent set of cross sections for electron impact collisions with carbon monoxide (CO), to be published in the IST-Lisbon database with LXCat. The set is validated by comparing swarm parameters calculated using the two-term Boltzmann solver LoKI-B with available experimental data. A severe inconsistency between the total rotational and effective cross sections reported in the literature for low values of the electron energy (ϵ < 0.1 eV) is pointed out. It is shown that inelastic and superelastic collisions involving rotationally excited levels, as well as superelastic collisions with the first vibrational excited level, have to be taken into account to accurately calculate the electron energy distribution function. The relevance of these mechanisms implies a dependence of the effective momentum transfer cross section on the gas and vibrational temperatures and suggests its replacement by an elastic momentum transfer cross section. The electron kinetics in CO2–CO mixtures are also discussed in detail, namely the influence of vibrational excitation and of the CO2/CO ratio on the electron energy distribution function, rate coefficients and power transfer. The vibrational temperatures of both CO and the different vibrational modes of CO2 have a marked influence on the results, due to the importance of superelastic collisions with the vibrationally excited states of both gases. The presence of CO in the mixture modifies the energy transfer pathways and, at moderate reduced electric fields (∼30−100 Td), the vibrational excitation of CO can become the dominant energy loss mechanism, affecting the input of electron energy into the asymmetric stretching mode of CO2.