Abstract
Electron interaction with methane molecule and accurate determination of its elastic cross-section is a demanding task for both experimental and theoretical standpoints and relevant for our better understanding of the processes in Earth’s and Solar outer planet atmospheres, the greenhouse effect or in plasma physics applications like vapor deposition, complex plasma-wall interactions and edge plasma regions of Tokamak. Methane can serve as a test molecule for advancing novel electron-molecule collision theories. We present a combined experimental and theoretical study of the elastic electron differential cross-section from methane molecule, as well as integral and momentum transfer cross-sections in the intermediate energy range (50–300 eV). The experimental setup, based on a crossed beam technique, comprising of an electron gun, a single capillary gas needle and detection system with a channeltron is used in the measurements. The absolute values for cross-sections are obtained by relative-flow method, using argon as a reference. Theoretical results are acquired using two approximations: simple sum of individual atomic cross-sections and the other with molecular effect taken into the account.
Highlights
We present a combined experimental and theoretical study of the elastic electron differential cross-section from methane molecule, as well as integral and momentum transfer cross-sections in the intermediate energy range (50–300 eV)
Theoretical results are shown in two approximations: the simple sum of individual atomic cross-sections and with molecular effects taken into account
Our calculations overestimate the measured differential cross-sections (DCSs), but it matches with shape and is in a good agreement with other theories [29,32] at high scattering angles, above 110°
Summary
Iga et al [31] used crossed beam apparatus to obtain scattering intensities (100–500 eV incident electron energies), which were converted to the absolute scale using relative flow method (Ne was used as a reference gas) They used Schwinger variational method combined with the distorted-wave approximation to study elastic electron scattering (1–500 eV) theoretically. The paper by Fuss et al [34] is interesting because they provided the recommended set of data for differential and integral cross-sections for methane, including elastic electron scattering They obtained their dataset by merging and averaging other authors’ data [19,25,30,33] for lower energies and calculating ones for high energies (40–10 keV).
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