Directional Compton profile measurements of aluminium with 412 and 60 keV radiation

Abstract

The [111], [110] and [100] directional Compton profiles of aluminium have been deduced from Compton-scattering measurements on single-crystal slices at gamma-ray-source energies of 412 and 60 keV. A quantitative comparison between profiles measured at these two energies has been made. Both experimental systems detect profile anisotropies ∼0·5% of the peak height, J(0). An APW calculation is in good agreement with experiment in that it predicts small, but significant, anisotropies of this order. Hartree–Fock (H–F) and tight-binding calculations however, overestimate the magnitude of the observed difference profiles by factors of roughly two and four, respectively, while a slowly-varying-density calculation predicts no profile anisotropy. The theoretical directional profiles, when compared with data obtained from the high-energy spectrometer, show excess momentum density ∼0·5–1% J(0) at low momenta, with the exception of the H–F calculation which shows a deficit.