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 v_a/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.