Angular distribution of electrons elastically scattered from CH₄

Abstract

Differential elastic (vibrationally) scattering cross sections of CH, by electron impact have been measured using a modulated crossed-beam method. The energy and angular range covered were from 5 to 50 eV and from 12 to 156", respectively. The integrated and momentum transfer cross sections were obtained from the differential cross sections. The present results are compared with the earlier data of Tanaka er a / and with theoretical results of Lima et a1 and Jain and Thompson. Some discrepancies were found in the measurements and theoretical results.

Cross Sections for Electron Collisions with Methane

“…Two sets of data by Tanaka and collaborators 36,43 differ in the spectrometers used, the normalization procedures, and extrapolation formula for differential cross sections. The newer MTCS 36 are higher than the earlier ones by some 30% and give the highest cross sections about the maximum at 39 100-500 10-135 Sakae et al (1989) 40 75-700 5-135 Shyn and Cravens (1990) 41 5 51 Modified effective range theory is expected to match with the elastic and momentum transfer cross sections in the low energy range. However, due to the high value of the dipole polarizability, the applicability of this method in methane is limited to energies below 0.5 eV.…”

“…Therefore, experiments at high angles are important. Out of several data sources listed in Table 4, the measurements by Shyn and Cravens, 41 who used an electrostatic analyzer extending up to 168 • , and Allan 35 and Cho et al, 38 who used a magnetic-field angle-changer extending up to 180 • , sample high angles. Two sets of data by Tanaka and collaborators 36,43 differ in the spectrometers used, the normalization procedures, and extrapolation formula for differential cross sections.…”

Modeling the electron-impact dissociation of methane

“…In the top panel, we present the representative examples of previous experimental and theoretical studies of elastic electron−methane scattering, including the experimental results of Ferch et al, 6 Lohmann and Buckman, 13 Boesten and Tanaka, 1 Bundschu et al, 60 Shyn and Cravens, 17 Sohn et al, 61 and Tanaka et al, 62 as well as theoretical calculations using the variational Schwinger method by Iga et al 10 and Machado et al, 63 and the results of R-matrix calculations by Nestmann et al, 35 Varambhia et al, 36 and Vinodkumar et al 37 We also show the recommended values for the elastic cross sections by Fuss et al 42 In the middle panel, our R-matrix elastic cross sections can be seen for the equilibrium structure of methane. We compare the results for cc-pVDZ, cc-pVTZ, 6-31G(d), and 6-311G(d) bases for the target using 10 states (24 CI roots for cc-pVDZ and 23 for other bases) in the calculations.…”

R-matrix calculations of low-energy electron alkane collisions

“…The long-range polarization potential will induce minor contributions from higher partial waves. This problem was studied by OʼMalley (1963) for collisions with rare gas atoms for which the polarizability is also the Müller et al (1985); light blue circles: Shyn and Cravens (1990); yellow circles: Curry et al (1985); dark blue circles: Tanaka et al (1982).…”