Read Full Article (file size: 399305 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, A04303, doi:10.1029/2005JA011454, 2006

Analysis of electron impact ionization properties of methane

Xianming Liu

Planetary and Space Science Division, Space Environment Technologies, Pasadena, California, USA

Donald E. Shemansky

Planetary and Space Science Division, Space Environment Technologies, Pasadena, California, USA

Abstract

Published experimental photon and electron impact ionization cross sections of CH₄ have been reviewed and analyzed. Absolute partial ionization oscillator strengths (f _ij ) for CH₄ ⁺, CH₃ ⁺, CH₂ ⁺, CH⁺, H⁺, and H₂ ⁺ have been obtained. Electron impact ionization cross sections are recommended based on agreement between the oscillator strength values derived from photoionization and electron impact measurements. Analytic functions for cross sections of CH₄ ⁺, CH₃ ⁺, CH₂ ⁺, CH⁺, C⁺, H₂ ⁺, and H⁺ produced by electron impact ionization of CH₄ are established. The derived excitation cross-section functions are accurate from threshold to impact energies limited by relativistic effects (i.e., E < 0.2 MeV). The cross sections examined here are important for modeling Titan ionospheric chemistry.

Received 4 October 2005; accepted 6 January 2006; published 7 April 2006.

Keywords: electron-impact excitation function; ionization oscillator strength; methane ionization cross section.

Index Terms: 2423 Ionosphere: Ionization processes (7823); 2419 Ionosphere: Ion chemistry and composition (0335); 2447 Ionosphere: Modeling and forecasting; 7831 Space Plasma Physics: Laboratory studies and experimental techniques; 6280 Planetary Sciences: Solar System Objects: Saturnian satellites.

Read Full Article (file size: 399305 bytes)    Cited by

Citation: Liu, X., and D. E. Shemansky (2006), Analysis of electron impact ionization properties of methane, J. Geophys. Res., 111, A04303, doi:10.1029/2005JA011454.

Copyright 2006 by the American Geophysical Union.