Electron scattering differential cross sections for C 2H 2, C 2H 4, and C 2H 6 by gas phase electron diffraction - binding effects

Abstract

Experimental differential cross sections for 40 keV electrons scattered by C 2H 2, C 2H 4 and C 2H 6 molecules were measured using the gas electron diffraction method in the range of the scattering variable s from s = 1 A −1 to s = 30 A −1. The differential cross sections for neon were also measured and compared with calculated differential cross sections to calibrate the diffractograph. Experimental differential cross sections show significant deviations with respect to theoretical differential cross sections calculated from the Debye-Ehrenfest model, mainly in the range of small scattering angles. The observed differences are connected to chemical binding effects. From the experimental data, an estimation of the binding energy was carried out. The deduced values: −0.58 ± 0.20 au for C 2H 2, −0.94 ± 0.30 au for C 2H 4 and −1.23 ± 0.40 au for C 2H 6 are in agreement with those obtained by thermochemical methods.