A High Precision Electron Diffraction Unit for Gases

Abstract

An electron diffraction unit using counting techniques has been built which makes it possible to record relative total (elastic and inelastic) differential scattering cross sections directly. Features of the unit which deviate from those in conventional units (which incorporate a rotating sector and photographic plates) are described in detail. The possible uses and limitations of the new instrument are discussed. The total scattered intensities in the range 1.5≤s(Å−1)≤7.2 with 40 keV electrons from N2O and CO2 are presented as examples. The results are compared to the predictions of the independent atom model and differences due to chemical binding and electronic correlation effects are observed.