Fourier spectra of resonant nuclear forward scattering: lineshape dependence on absorber thickness distribution

摘要

We report on recent developments in the analysis of nuclear forward scattering (NFS) using the Fourier transformation of measured time spectra. In the frequency domain, it is shown that the lineshape is generally described by the convolution of two intensity factors. One of them is Lorentzian related to free decay. We derived the expressions for the second factor related to the Frenkel exciton polariton formed in M?ssbauer media. For stray particles of a powder spread over a 2D surface the particle size distribution can be derived from M?ssbauer thickness distribution. The thickness-related lineshape is deconvolved through sharpening the Fourier NFS spectra. The lineshapes in these sharpened spectra are theoretically expressed via the parameters of the particle size distributions. Through fitting the lineshapes with our theoretical expressions the particle size distribution parameters were determined.