On the possibility for inequality between the probabilities for recoilless absorption f' and re-emission f''

Using the scattering geometry in Moessbauer spectroscopy, the authors introduce the probability for recoilless re-emission of the gamma quanta f''. It is assumed that f' ≡ f'', where f' is Debye-Waller factor. The values of f' and f'' are measured for a lot of iron and tin containing compounds. A discrepancy between f' and f'' is observed and the differences exceeded many times the experimental errors reported in the literature. The typical values of the ratio f''/f' are in the range 1.2 - 1.5. In order to avoid possible influence of the sample dispersity and inhomogeneity on Moessbauer spectra, the monocrystal samples of sodium nitroprusside of two thicknesses within the error limits are used. The results agree with those obtained for polycrystalline powder samples. In general, the experimental results disagree with the commonly accepted assumption that there is no difference between the probabilities for recoilless absorption and re-emission. Two relaxation models are developed on this basis. (author)