Electron attachment to oxygen in nitrogen buffer gas at atmospheric pressure

Abstract

We have carried out experimental and theoretical studies of three body electron attachment (TBEA) to O₂ in N₂/O₂ mixtures. We have applied three different experimental methods to determine the apparent rate constant k for TBEA to O₂ for reduced electric fields E/ n from 0.5 Td up to 4.5 Td and O₂ concentrations from 0.02% up to 3%. From the apparent rate constant k we have evaluated three body rate constant for electron attachment to O₂ in pure O₂ $\left( {k_{O_2 } } \right)$ and in pure N₂ $\left( {k_{N_2 } } \right)$. The comparison of present data with former studies shows that the former values of $k_{N_2 }$ overestimated the efficiency of this reaction, while in case of $k_{O_2 }$ we have found agreement with earlier studies. We have solved numerically the Boltzmann equation of the electrons and calculated the values of k, $k_{N_2 }$ and $k_{O_2 }$ using well established cross sections. Using the known collision cross section set for TBEA to O₂, very good agreement between calculated and measured results for $k_{O_2 }$ was found, while in the case of k and $k_{N_2 }$ we had to introduce a scaling function, which describes the decrease of the efficiency of TBEA to O₂ in presence of N₂ and the dependence of the scaling function on E/n was determined.