RAYLEIGH-SCATTERING FROM CRYSTALS AND AMORPHOUS STRUCTURES

Elastic-scattering cross sections of photons for momentum transfer in the range 0.1 less than or equal to x less than or equal to 2. 2 Angst rom(-1) with E(gamma) = 59.5 and 316 keV were measured in order to tes t the limits of momentum transfer within which the scattering by real samples can be considered as being due to free-atom Rayleigh scatterin g. Polycrystalline aggregate, liquid, perfect-single-crystal, and crys tal powder samples were used as scatterers. The measurements for E(gam ma) = 316 and 59.5 keV were carried out in the angular ranges theta = 0.5 degrees-10 degrees and 2 degrees-23 degrees with a geometrical res olution of 0.1 degrees and 1 degrees, respectively. At the present tim e, most of the experimental data on elastic photon scattering have bee n measured using solid molecular structures as scatterers. The present results allow the conclusion that highly precise data (Delta d sigma/ d Omega less than or equal to 2%) on elastic scattering of photons can be compared with free-atom Rayleigh-scattering theories only for x > 2 Angstrom(-1).