Survey of elastic scattering experiments in the X-ray and Delbrueck regimes

A detailed survey of recent experiments in the photon energy range (few keVs to tens of keVs) for which anomalous X-ray scattering is observed, through to the 0.6-12 MeV range where Delbrueck scattering becomes important is presented. Although accurate low photon-energy measurements have been performed in more recent years, using advanced detection capabilities, X-ray optical techniques and synchrotron sources, it is apparent that there remains much scope for systematic measurement and comparison with state-of-the-art calculations. In the photon-energy range within which Rayleigh scattering dominates other elastic processes, we note the generally good state-of-the-art S-matrix based Rayleigh amplitude calculations and experiment. No evidence of any systematic trends from agreement is observed. In the photon-energy range from 662 keV up to 11.4 MeV, within which the effect of Delbrueck scattering becomes first observable and then significant, the generally sparse nature of experimental data having direct bearing upon the Delbrueck process is noted. It is apparent that there also exists a need for detailed calculation of the Coulomb-correction terms in order to allow critical comparison between experiment and theory. (author). 159 refs., 6 figs., 1 tab