[en] A clean paramagnetic ⁵⁷Fe Moessbauer spectrum due to an isotropic hyperfine interaction was observed at 'almost free' Fe atoms in a frozen argon matrix. It was obtained by ion implantation of ⁵⁷Co in an argon matrix at 4.2 K and it is due to ⁵⁷Fe (3d⁷) ions in a magnetically isotropic Γ₆ or Γ₇ Kramers state. The hyperfine coupling constant of the free ⁵⁷Fe (3d⁷) ion in the nuclear groundstate is deduced to be A=5.0(3), 7.9(5) or 11.1(6) MHz, depending whether the Fe⁺ (3d⁷) is in a J=9/2, 7/2 or 5/2 state respectively. (orig.)

[en] Iodine Moessbauer-effect sources in the form of Mg₃TeO₆ and Ca₃TeO₆ were developed. Due to the unusual solid state properties of these crystals and the high coordination symmetry of Te in their matrices, it is possible to obtain single and narrow emission lines with a recoilless fraction at room temperature of 0.55, ten times larger than that of the conventional Zn and Sn telluride sources. The compounds can be prepared and repeatedly irradiated without any perceivable radiation damage and with negligible residual activity from the other constituent elements. This allows for the first time the use of ¹²⁹I Moessbauer spectroscopy at room temperature and significantly improves the performance of ¹²⁷I at low temperatures. It is suggested to adopt the Mg₃TeO₆ as a standard iodine Moessbauer source. (orig.)

[en] ⁵⁷Co was implanted in different reactive and non reactive frozen gases like Ne, Ar, N₂, Xe, CH₄ and C₂H₄. Higher ionization states of Fe and cryochemical compounds are detected. (Auth.)

[en] ¹²⁵Te and ¹²⁹I Moessbauer spectra were studied of AuTe₂, AuAgTe₄, and AuCuTe₄. A distribution in hyperfine parameters is needed to obtain a satisfactory fit of the ¹²⁹I spectra, and is interpreted in favor of lattice displacement waves recently observed in these compounds. (Auth.)

[en] Absorption Moessbauer spectra were measured on low temperature (6-21 mK) oriented nuclei. For magnetic orientation this method allows the determination of the sign of the parent state magnetic moment. The method enables the determination of the parent state quadrupole coupling even for a polycrystalline sample. Signs of ground state magnetic moments for ¹⁹¹Pt and ¹⁹³Os, and electric quadrupole moments for ¹²⁵Te^m and ¹²⁹Te are determined. (orig.)

[en] It is demonstrated that the detection of low temperature nuclear orientation by Moessbauer spectroscopy, rather than by the observation of the angular distribution of the emitted radiation, allows to determine nuclear quadrupole interaction strengths generated by randomly oriented defect-induced electric field gradients in cubic lattices. Also the cooling behaviour of radioactive nuclei implanted in semiconductors is studied. (orig.)

[en] Defect-induced field electric field gradients, generated by ion implantation of ¹²⁵I in α- and β-Sn and in graphite, were used to obtain local nuclear orientation at low temperatures. The resulting nuclear orientation at the parent ¹²⁵I state was detected by ¹²⁵Te Moessbauer spectroscopy. From the measured nuclear quadrupole interaction strengths at the parent state, the electric field gradient and the cooling behavior of implanted atoms were studied. (orig.)