Kinetic-energy Distributions of Positive and Negative Ions in Townsend Discharges in Oxygen

Published

April 1, 1999

Author(s)

MVVS. Rao, Richard J. Van Brunt, James K. Olthoff

Abstract

Translational flux-energy distributions of positive and negative ions have been measured at high electric field-to-gas density ratios (E/N) up to 40 x 10^-18 V m² (40 kTd) in diffuse, parallel-plate Townsend discharges in oxygen using an ion energy analyzer-mass spectrometer. The O₂+ ion is the most abundant ion detected in the discharge, and exhibits Maxwellian energy distributions for E/N < 20 x 10 ^-18 V m², which is consistent with predictions based upon the assumption that resonant symmetric charge exchange is the dominant ion-molecule collision process. The less abundant ions, O⁺, O₂^-, and O^-, exhibit non-Mawellian ion kinetic energy distributions at nearly all E/N, indicative of multiple ion-molecule reactions affecting the ion transport. Mean energies are obtained for each ion as a function of E/N from analysis of the energy distributions, and symmetric charge-exchange cross sections are calculated from the data where appropriate.

Citation

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)

Volume

59

Issue

4

Pub Type

Journals

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Keywords

cross-sections, ion-molecule reactions, kinetic-energy distributions, O2, oxygen, Townsend discharge

Citation

Rao, M. , Van Brunt, R. and Olthoff, J. (1999), Kinetic-energy Distributions of Positive and Negative Ions in Townsend Discharges in Oxygen, Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=6288 (Accessed October 13, 2025)