Theory of nuclear resonant scattering of synchrotron radiation in the presence of diffusive motion of nuclei.

Abstract

A general theory of the time dependence of nuclear resonant forward scattering of synchrotron radiation in the presence of diffusive motion of nuclei is further developed. The scattering problem is solved for the two characteristic cases of diffusive motion. The first one is the continuous isotropic localized diffusion of a particle within a cage formed by a drift potential. The second case is the jump anisotropic unlimited diffusion of nuclei on a crystalline lattice. In both cases the frequency dependence of nuclear susceptibility has a complicated shape described by a superposition of Lorentzian functions having different weights and widths. Correspondingly several stages appear in the time evolution of the nuclear forward scattering which are characterized by different decay rates. In the thick absorber case the target can exhibit successively different partial thicknesses in the time evolution of forward scattering.