Spectral momentum densities in matter determined by electron scattering.

In electron momentum spectroscopy (EMS), an incoming energetic electron (50 keV in this work) ionizes the target and the scattered and ejected electrons are detected in coincidence (at energies near 25 keV). From the energy and momentum of the detected particles, the energy omega and momentum q transferred to the target can be inferred. The observed intensity distribution I(omega, q) is proportional to the spectral momentum density of the target and hence provides a direct challenge to many-body theoretical descriptions of condensed matter. This is illustrated by comparing some many-body calculations with EMS measurements on graphite and polycrystalline aluminium.