Compton scattering and the study of electron momentum density distributions

The Doppler-broadening experienced by photons Compton scattered from bound electrons allows the momentum distribution of the target to be probed. The Compton profile so obtained turns out to be sensitive to the wave-mechanical description of the scatterer and has therefore been exploited, for example, to check band theoretical models of solids, to identify electron correlation effects and most recently to extract Fermi surface topography. The technique has suffered from the low photon energy and lack of monochromaticity of X-ray tube sources and the weakness of gamma emitting isotopes. Both these problems have been circumvented with the use of synchrotron radiation which has the added benefit of allowing spin densities to be studied through the extraction of circularly polarised photons. In this paper the interpretation of Compton line-shapes within the Impulse Approximation will be discussed and illustrated with a selection of recent results. (C) 1997 Elsevier Science Ltd.