Adequacy of the plane wave approximation in the analysis of Compton profiles

The errors incurred in Compton scattering calculations by using the Impulse Approximation are evaluated. Distorted waves for the ejected electron are calculated in both the Hydrogenic and Hartree-Slater wavefunction approximations, the former analytically and the latter via extensive numerical calculations of the partial wave expansion. Corrections to Impulse include the appearance of a Compton defect, Compton profile asymmetry and secondary maxima. A characteristiccorrection parameter which is (binding energy)/(momentum transfer)2 is obtained. Recent x-ray and HEEIS experiments demonstrate the existence of these non-impulse effects. Estimates are also made of non-impulse effects (corrections to PWIA) for (e,2e) coincidence experiments