Negative ion clusters in oxygen: collision cross sections and transport coefficients

• Published in: The European physical journal. D, Atomic, molecular, and optical physics Vol. 55; no. 3; pp. 637 - 643
• Main Authors: de Urquijo, J., Bekstein, A., Ducasse, O., Ruíz-Vargas, G., Yousfi, M., Benhenni, M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2009; EDP Sciences
• Subjects: Applications of Nonlinear Dynamics and Chaos Theory; Atomic; Exact sciences and technology; Molecular; Monte carlo methods; Optical and Plasma Physics; Physical Chemistry; Physics; Physics and Astronomy; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma Physics; Plasma properties; Plasma simulation; Quantum Information Technology; Quantum Physics; Spectroscopy/Spectrometry; Spintronics; Transport properties; 52.80.Dy Low-field and Townsend discharges; 52.20.-j Elementary processes in plasmas; 52.25.Fi Transport properties; 52.80.-s Electric discharges; Oxygen; Digital simulation; Theoretical study; Experimental study; Transients; Pressure dependence; Negative ions; Monte Carlo methods; Algorithms; Momentum transfer; Transport coefficient; Plasma transport processes; Diffusion; Curve fitting; Cross sections
• ISSN: 1434-6060; 1434-6079
• DOI: 10.1140/epjd/e2009-00248-8

Using a pulsed Townsend experiment, we have observed the formation of two negative ion species in oxygen over the pressure range 100–600 torr, and the density-normalised electric field strength, E/N, from 2 to 14 Td. The peculiar shape of these transients has led us to propose a scheme of three-body ion-molecule reactions leading to the formation of O 4 - and O 6 - , which is substantiated by a curve fitting procedure. The resulting mobility data of these two ionic species have been used to calculate their respective momentum transfer collision cross sections, together with the dissociation cross sections that are needed to extend the range of calculation of mobility and diffusion (transverse and longitudinal) to 1000 Td. These calculations were based on an optimised Monte Carlo algorithm, using collision cross sections obtained from a JWKB approximation (Jeffreys-Wentzel-Kramers-Brillouin) or taken from literature.