Measurement of ionization, attachment, detachment and charge transfer rate coefficients in dry air around the critical electric field

We obtain pressure-dependent rate coefficients in dry synthetic air (79% N 2 , 21% O 2 ) by fitting Pulsed Townsend measurements over a pressure range from 10 to 100 kPa, around the critical density-reduced electric field from 86 to 104 Td. The physical processes are reviewed and set in relation to a suitable kinetic model. A procedure for fitting kinetic reaction rates, based on finite-volume simulations of charge carrier drift, is described. Rate coefficients are obtained for electron attachment, ionization and detachment, as well as for ion conversion. We find a quadratic pressure dependency in the conversion rate, consistent with three-body collisions, and observe a pressure dependency in the onset of electron avalanche growth in dry air.