Low-energy limit to channelling effects in the inelastic scattering of fast electrons

By studying channelling effects in the core-loss excitations of the mineral anhydrite (CaSO4), it has been found that the impact parameter is two to three times smaller than previously reported. This means that channelling effects in elastic scattering of fast (beam) electrons should be observable down to energy losses as low as 200 eV. However, background subtraction for energy-loss spectra is a serious problem in the observation of channelling effects from electrons experiencing such low losses in energy. The low value of the impact parameter means that it is possible to use thin-window energy dispersive X-ray spectrometers to observe the variation in the intensity of the oxygen K X-ray peak and to apply the results to quantitative atomic site location. (author)