Final-state interaction in Compton scattering from electron liquids

We present Compton profiles (CP's) of Li measured with momentum space resolution of 0.02 a.u. and 8--9 keV incident photon energy. The valence CP's are found to be asymmetric in shape and the predicted sharp features at the Fermi break are drastically smeared out. The observed additional broadening of the CP beyond experimental resolution is predominantly attributed to the finite width of the spectral density function of the excited particle. The asymmetry agrees well with calculations using a many-particle scheme, which will be useful for interpreting final states in soft x-ray and photoemission.