Ionization and attachment coefficients in CO2 : N2 : He and pure CO2

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Abstract
Values of the ionization (α/N) and attachment (η/N) coefficients have been determined from spatial current growth measurements in uniform fields E for a CO2 : N2 : He (1 : 2 : 3) mixture and for pure CO2 over the ranges 4.66×10−16⩽E/N⩽8.48×10−16 V cm2 and 7.63×10−16⩽E/N⩽9.89×10−16 V cm2, respectively, where N is the gas density. The limiting values of E/N, at which α=η, are found to be (4.66±0.14) ×10−16 V cm2 and (8.20±0.16) ×10−16 V cm2 for the CO2 : N2 : He mixture and for CO2, respectively. The present values of the coefficients are in reasonably good agreement with those calculated from a solution of the Boltzmann equation using electron‐collision cross sections. Nevertheless, the present results indicate that even closer agreement would be obtained if the attachment cross section used in the calculations is reduced by about 15%.