Ion-Molecule Reactions and Ion Kinetics in DC Townsend Discharges in Dielectric Gases

Published

January 1, 1999

Author(s)

MVVS. Rao, James K. Olthoff

Abstract

The transport of positive and negative ions plays an important role in the initiation and behavior of discharges in gaseous dielectrics. In many cases, the identities, intensities, and kinetic energies of ions are determined by ion-molecule collisions experienced by ions as they are accelerated through the discharge. To help delineate the role of various collisional processes, such as charge-exchange collisions, collisional detachment, and ion conversion, we have measured the kinetic-energy distributions (KEDs) of positive and negative ions formed in dc Townsend discharges generated in O₂ and SF₆ at high electric field-to-gas density ratios (E/N). The relative abundances and mean energies of the ions are obtained from these measurements, and the effective cross sections for the ion-molecule reactions, in some cases, may be calculated. The availability of ion-molecule collision cross sections for the negative ions formed in O₂ and SF₆ enable a reasonable understanding of the KED data. However, for these two molecules, attempts to analyze the KED data for these two gases highlight the lack of fundamental ion-molecule cross section data for positive ions formed in these discharges.

Proceedings Title

Proc., Intl. Symp. on Gaseous Dielectrics

Conference Dates

June 2-5, 1998

Conference Location

Virginia Beach, VA

Pub Type

Conferences

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Keywords

ion-energy distributions, ion-molecule reactions, oxygen, SF₆, Townsend discharge

Citation

Rao, M. and Olthoff, J. (1999), Ion-Molecule Reactions and Ion Kinetics in DC Townsend Discharges in Dielectric Gases, Proc., Intl. Symp. on Gaseous Dielectrics, Virginia Beach, VA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=21154 (Accessed December 13, 2024)