Experimental studies of inelastic X-ray and gamma-ray scattering

Abstract

Studies of inelastic scattering of X-rays and gamma-rays of energies higher than 30 keV performed with the help of NaI(Tl) and semi-conductor detectors of moderate and good resolution, respectively, are considered in the first part of this review. Theoretical treatments based on the non-relativistic (e(2)/2mc(2))A(2) interaction term, the impulse approximation, the incoherent scattering function approximation, the (-e/mc)P . A interaction term, and the relativistic second order S matrix approach have been used to understand a few representative experimental results concerning Compton scattering from K- and L-shells, and from whole atoms for values of the momentum transfer parameter x larger than about 2 Angstrom(-1), where x = sin(theta/2)/lambda, theta is the scattering angle and lambda is the wavelength of the incident radiation. Techniques of detection of recoil ions have been described in the context of recent measurements of relative probabilities for double and single ionization in Compton scattering from helium. The second part of this review deals with high resolution measurements concerning inelastic scattering of X-rays of energies lower than about 20 keV. A recently demonstrated dependence of K and L X-ray fluorescence spectra on incident photon energy near respective thresholds is highlighted along with its explanation based on crystal momenta and a single step resonant inelastic scattering treatment. Non-resonant inelastic scattering studies involving the excitation of plasmons and phonons in condensed matter are also discussed. Nonlinear photon-density dependent effects interpreted as Compton scattering, and final remarks are then presented. (C) 1997 .