Diffusion, Attachment and Attachment Cooling of Thermal Electrons in Oxygen and Oxygen Mixtures

Abstract

The Cavalieri electron density sampling technique has been used to measure the diffusion and attachment rate coefficients for thermal electrons in O2, and in O2–N2 and O2–C02 mixtures. The observed pressure dependence of the three-body attachment rate coefficient va/N2 is shown to be caused by the selective removal of electrons from the distribution at the attachment resonance energy, and the magnitude of this effect (so-called 'attachment cooling') is shown to be a measure of the magnitude of the rotational excitation cross sections in O2 and N2. Three-body rate coefficients for the formation of O2 involving O2, N2 and CO¯2 as third bodies have been found to be 2.2,011 and 3.5 X 10¯30 cm6 S¯l respectively. The value of the diffusion coefficient ND for thermal electrons in O2 is found to be (37 � 3) x 1021 cm¯1s¯1.