[en] ¹¹⁹Sn Moessbauer investigations of the ferromagnetically diluted Nisub(2)Mnsub(x)Bsub(1-x)Sn(B=Ti, V) and Pdsub(2)Mnsub(x)Vsub(1-x)Sn Heusler-type systems have been performed and the results are reviewed and discussed. It has been found that distributions of the transferred hyperfine magnetic field as seen by a tin nucleus are very sensitive for a type of the local magnetic interaction in these simple ferromagnets, especially when studied versus the sample temperature. This sensitivity allows to reach some conclusions about the coupling mechanism between localised manganese magnetic moments. Namely, it is concluded that the interaction beyond the second neighbour shell is practically irrelevant for the magnetic ordering process. This very fact means that the free electron approach to the calculation of exchange integrals can not be applied for these particular systems. (Author)

[en] Separate abstracts were prepared for 2 of the papers in this report. The remaining 26 papers, dealing with the use but not with advances in the use of Moessbauer effect in studies of solid state physics, were considered outside the subject scope of INIS. (M.F.W.)

[en] The paper contains an analysis of the Moessbauer line shape after scattering by a resonance, isotropic target. It is shown that line-width depends on the scattering geometry and under special circumstances may be smaller than natural line-width. Line-width may be reduced under these special conditions up to 0.643 natural line-width in a single scattering process. (author)

[en] Application of nuclear methods such a uses of muon beams, level mixing resonance, Moessbauer effect in experimental studies of solid state physics are presented. (M.F.W.)

[en] A filter constructed on the basis of differential filters and a Fermi type function is described in application to the correction of the accuracy of determining line positions in Moessbauer spectroscopy. A general method of estimating the error of Moessbauer spectrum parameters fitted to a filtered spectrum is also described. This numerical method takes into consideration not only a linear approximation of the fitted function, but also all higher contributions. (author)

[en] The self-correlation functions for long-range diffusion via the monovacancy mechanism in FCC lattices have been calculated within the encounter approximation varying parameters of the five-frequency model. The validity of this approach to the existing single crystal Moessbauer data has been discussed. The so-called high temperature limit has been outlined and its applicability considered. A simple method for calculating the experimental solid angle correction has been introduced for diffusion-broadened Moessbauer spectra from the single crystal sources. (Auth.)

[en] Diffraction of X-rays or neutrons can not be used to obtain details about the atomic vibrational anisotropy in the case of amorphous materials due to the lack of well-defined Bragg reflections. Moessbauer spectroscopy can yield some information in such cases, either via the Goldanskii-Karyagin effect or by applying a magnetic field, preferably along the beam axis. The latter method can be applied to the (preferably diamagnetic) samples exhibiting an electric quadrupole interaction (preferably non-axial) and the magnetic field should be chosen in such a way as to produce significant off-diagonal elements in the hyperfine hamiltonian. The external magnetic field method is capable of yielding much more information than the Goldanskii-Karyagin effect in most cases, provided sufficiently strong magnetic fields are available. Some examples of the ¹²⁹I Moessbauer spectra have been calculated to show the usefulness and sensitivity of the external magnetic field method. (orig.)

[en] Space-time events are characterized by their coordinates x from the classical point of view. The same events from the quantum-mechanical point of view should be described rather by the expectation value of coordinates < X>. The expectation value could be evaluated by introducing a density operator rho(x,x') associated with the event. In the case where rho(x,x') cannot be described by delta functions strictly monochromatic radiation does not exist. If localizability is limited by Planck's length there are no narrower spectral lines than approximately 2X10^-29 E²(eV) where E stands for the photon energy. (author)

[en] The nuclear resonant scattering of the unpolarized Lorentzian-shaped collimated beam Z (ω) by the homogeneous, isotropic target was analysed. S₁ (ω) describes resonantly scattered γ-quanta. The normalized S₁ (ω) shape for different angles is presented for the particular example: the source was assumed to be ⁵⁷Co(Pd) and the target was taken as Fesub(0.05) Pdsub(0.95) alloy enriched up to 95 at % in ⁵⁷Fe. The energy profile of the back-scattered radiation from the thick target has exactly the same shape as the source Lorentzian spectrum. The nuclear resonantly scattered γ-beam has not longer Lorentzian profile and may be observed for thin targets as narrowed without any sidebands. (P.S.)

[en] Theories claiming existence of the anisotropy in the velocity of light are inconsistent with experimental data obtained by Mossbauer measurements. (author)