Analysis of electron impact ionization properties of methane

Published experimental photon and electron impact ionization cross sections of CH 4 have been reviewed and analyzed. Absolute partial ionization oscillator strengths ( f ij ) for CH 4 + , CH 3 + , CH 2 + , CH + , H + , and H 2 + 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 CH 4 + , CH 3 + , CH 2 + , CH + , C + , H 2 + , and H + produced by electron impact ionization of CH 4 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.