Rayleigh scattering from crystals and amorphous structures

Abstract

Elastic-scattering cross sections of photons for momentum transfer in the range 0.1\ensuremath{\le}x\ensuremath{\le}2.2 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$ with ${\mathit{E}}_{\ensuremath{\gamma}}$=59.5 and 316 keV were measured in order to test the limits of momentum transfer within which the scattering by real samples can be considered as being due to free-atom Rayleigh scattering. Polycrystalline aggregate, liquid, perfect-single-crystal, and crystal powder samples were used as scatterers. The measurements for ${\mathit{E}}_{\ensuremath{\gamma}}$=316 and 59.5 keV were carried out in the angular ranges \ensuremath{\theta}=0.5\ifmmode^\circ\else\textdegree\fi{}--10\ifmmode^\circ\else\textdegree\fi{} and 2\ifmmode^\circ\else\textdegree\fi{}--23\ifmmode^\circ\else\textdegree\fi{} with a geometrical resolution of 0.1\ifmmode^\circ\else\textdegree\fi{} and 1\ifmmode^\circ\else\textdegree\fi{}, respectively. At the present time, most of the experimental data on elastic photon scattering have been measured using solid molecular structures as scatterers. The present results allow the conclusion that highly precise data (\ensuremath{\Delta}d\ensuremath{\sigma}/d\ensuremath{\Omega}\ensuremath{\le}2%) on elastic scattering of photons can be compared with free-atom Rayleigh-scattering theories only for x>2 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$.