Energy dependence of experimental Be Compton profiles

High-resolution Compton scattering measurements on Be single crystals along three main crystallographic directions ([10.0], [11.0], and [00.1]) have b een carried out using incident photon energies of 10, 29, and 56 keV to stu dy the energy dependence of the scattering cross:section. The experimental Compton profiles are in good agreement with theoretical profiles employing the local density approximation-based band theory framework. Extensive comp arisons between the computed and measured profiles, their first derivatives , and anisotropies defined as differences between various pairs of profiles show an excellent level of accord. The details related to the Fermi surfac e are clearly seen in the experimental Compton profiles. However, subtle bu t systematic direction-dependent discrepancies remain between the experimen tal and theoretical profiles, suggesting that a better treatment of electro n correlation effects in the inhomogeneous electron gas is needed to develo p a satisfactory description of the momentum density in Be. Our analysis al so indicates that the effective momentum resolution in low-energy Compton e xperiments possesses intrinsic limitations due to final-state interactions and possibly cannot be enhanced arbitrarily by improving the instrumental r esolution.