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[en] Published in summary form only

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[en] From reported experimental values of Moessbauer isomer shifts the change in nuclear mean-square charge radius, delta(r²), upon excitation was extracted, using electron densities calculated through a Dirac-Fock-Slater routine. Application of a uniform scheme of evaluation should give better insight in systematic trends of delta(r²). Also reported are generally more accurate ratios of delta(r²) either for different resonances in one element or for resonances in chemically similar elements. The literature has been surveyed through June 1973. (U.S.)

[en] Due to their wider radial extend the 5f electrons may form bands of different width and hybridization in metallic compounds of the light actinides. This leads to a broad spectrum of magnetic properties ranging from the localized magnetism of the lanthanides to the itinerant electron magnetism often found in transition metal compounds. Also, the influence of the crystalline electric field tends to be more pronounced than in rare earth compounds, but is usually not as dominant as in the 3d series. Magnetic structures and the question of 5f electron delocalization are reviewed with respet to actinide Moessbauer data and new results are presented. In particular the influence of applying external pressure is discussed. 60 references, 24 figures

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[en] Muon spin relaxation measurements have been performed on a powder sample of UPdSn. μSR verifies the existence of the two separate antiferromagnetic states (denoted AFM 1 and AFM 2) found by neutron diffraction, with transitions near 40 and 24 K, and with different magnitudes of their local fields. Both phase transitions extend over a region of ∼5 K width where two magnetic phases (para/AFM 1 and AFM 1/AFM 2) coexist. No evidence for a fluctuating and/or disordered spin component could be detected in AFM 1. It is concluded that the spins in AFM 2 are about 30% larger in magnitude than those in AFM 1. The absence of partial LRO ordering in UPdSn in contrast to the μSR results for the magnetic ground state of isostructural CeCuSn can be taken as another indicator that Cu-Sn disorder in the latter may be decisive, since similar disorder in the Pd-Sn sublattices is definitely absent. The spontaneous frequency in AFM 1 attains its highest value around T_N and then decreases on cooling. A similar behavior was observed in CeCuSn for the LRO portion of its magnetic ground state. This striking similarity in non-standard behavior most likely indicates that spin-structural properties of the LRO portion in CeCuSn are similar to the ones of AFM 1 in UPdSn

[en] Detailed information on electronic structure properties of actinide compounds has been obtained by the methods of Moessbauer spectroscopy (MS), perturbed angular correlations (PAC), and muon spin rotation (μSR). We shall give a brief overview of the possibilities for measurements on transuranic elements and of the physical parameters which can be obtained. MS, especially on neptunium compounds, is the workhorse in the field and we shall discuss some results concerning structural properties of neptunyl compounds and magnetic properties of neptunium intermetallics. The most interesting recent case here is NpSn3 where high pressure data have shown unexpected results. μSR has only recently been extended beyond uranium and preliminary data on NpA12 will be presented