[en] Single crystals of Nd₃ClS₂[SiS₄] were prepared from the elements. Data collection was carried out using a STOE image plate detector at 293K. The compound crystallizes in the orthorhombic space group Pnma with eight familiar units in a cell of dimension:a=1240.3(2),b=1035.8(2),c=1616.4(3)pmThe corresponding residual (all data) for the refined structures is 3.45%. In the crystal structure, the chloride ions form chains along [010] with trigonal coordination by the lanthanide ions.The magnetic behavior of powdered crystals was interpreted by ligand field calculations where the influence of the ligand field was taken into account by applying the angular overlap model and magnetic exchange by the molecular field approximation

[en] Single crystals of Gd(HF₂CCOO)₃(H₂O)₂·H₂O have been obtained by reaction of Gd₂O₃ with HF₂CCOOH in water. Data collection was carried out using a STOE imaging plate diffractometer at 173 K. The compound crystallizes in the triclinic space group P1-bar (Z=2) with a=833.1(2) pm, b=943.5(2) pm, c=944.9(2) pm; α=66.78(3), β=79.54(3) and γ=77.61(3). The corresponding residual (all data) for the refined structure is 2.98%. The magnetic behaviour of the compound was investigated in the temperature range of 1.7-300 K. The magnetic data were interpreted considering exchange interaction effects in the dinuclear Gd³⁺-Gd³⁺ unit. The exchange coupling constant J=-0.024 cm^-1 indicates antiferromagnetic interaction, whereas J=+0.05 cm^-1 for Gd(H₃CCOO)₃(H₂O)₂·2H₂O a ferromagnetic one

[en] Single crystals of the title compound were prepared from the elements by a solid state reaction in an iodine atmosphere. Data collection were carried out using a STOE image plate detector at 293 K. The compound crystallizes in the space group P2 1/n of the monoclinic system isotypically to Tb₄[SiS₄] 3 with four formular units in cells of dimensions: a=986.7(2) pm, b=1099.69(19) pm, c=1646.2(4) pm, β=102.67(3) deg. The corresponding residual (all data) for the refined structure is 3.09%. The magnetic behavior of the compound was investigated on powdered samples in a temperature range between 1.7 and 300 K. The deviations from the Curie-behavior could be interpreted by the molecular field approach

[en] The magnetism of the three compounds Pr₃X[SiS₄]₂ (X=Cl, Br, I) has been measured in the temperature range between 1.7 and 300 K. For the theoretical calculations to interpret the magnetic behavior the angular overlap model was employed to reproduce the ligand field influence and the molecular field approach to take magnetic interaction into account

[en] Ar-40/Ar-39 studies of seven low petrographic type L and H chondrites from Antarctica are presented. The hypothesis of McKinley et al. (1981) that the L3 chondrites ALHA77015, -77167, -77249, and -77260 are from a common fall is confirmed. It is shown that the Ar-degassing patterns of the four meteorites are identical. Also, the chondrites have similar K, Ca, Cl, and trapped Ar-39 contents and Ar-40/Ar-39 ages. 19 references

[en] Short Communication

[en] Sections of interplanetary dust particles (IDPs) have been analyzed with proton-induced X-ray emission (PIXE) and scanning transmission ion microscopy (STIM) in order to determine trace element contents and distributions on a micrometer scale as well as particle densities and masses. To accomplish this, several improvements of the proton microprobe and of the data acquisition system, as well as special sample preparation were necessary

[en] Resonance ionization mass spectrometry offers high sensitivity and elemental selectivity in microanalysis, but the isotopic precision attainable by this technique has been limited. Here we report instrumental modifications to improve the precision of RIMS isotope ratio measurements. Special attention must be paid to eliminating pulse-to-pulse variations in the time-of-flight mass spectrometer through which the photoions travel, and resonant excitation schemes must be chosen such that the resonance transitions can be substantially power-broadened to cover the isotope shifts. We report resonance ionization measurements of chromium isotope ratios with statistics-limited precision better than 1%.

[en] Optical profilers are valuable tools for the characterization of microelectromechanical systems (MEMSs). They use phase sifting interferometry (PSI) or vertical scanning interferometry to measure the topography of microscale structures with nanometer resolution. However, for many emerging MEMS applications, the sample needs to be imaged while placed in a liquid or in a package with a glass window. The increased refractive index of the transparent medium degrades the interference image contrast and prevents any measurement of the sample. We report on the modification of a Veeco NT1100 optical profiler to enable PSI measurements through refractive media. This approach can be applied to any other optical profiler with PSI capability. The modification consists in replacing the original illumination source with a custom-built narrow linewidth source, which increases the coherence length of the light and the contrast of the interference image. We present measurements taken with the modified configuration on samples covered with 3 mm water or 500 μm glass, and we compare them to measurements of uncovered samples. We show that the measurement precision is only slightly reduced by the water and glass, and that it is still sufficiently high for typical MEMS applications. The described method can be readily used for measuring through other types and thicknesses of refractive materials.

[en] Presolar silicon carbide grains of type X account for 1% of presolar SiC and, in all likelihood, formed in the ejecta of core-collapse supernovae. This is indicated by, e.g., large overabundances of the (primary) ²⁸Si isotope relative to the (secondary) ²⁹Si and ³⁰Si isotopes, as well as a large abundance of ⁴⁴Ti at the time of formation, now showing up as the decay product ⁴⁴Ca (e.g.). More recently, subtypes X0, X1, and X2 have been defined, depending on the detailed position in a Si three-isotope diagram. Here we review available literature data for barium and strontium in X1 and X2 grains. Grains of type X2, to first order, are enriched in s-process Ba compared to Solar System Ba. X1 grains contain, in addition, a variable admixture of a component low in ¹³⁵Ba and ¹³⁶Ba (relative to solar and ¹³⁷Ba), but high in ¹³⁸Ba. This component may represent r-process Ba or Ba produced by a neutron burst like the one proposed by. The delayed appearance of ¹³⁷Ba due to the 30 a half-life of its precursor ¹³⁷Cs may allow to date condensation of X1 grains from supernova ejecta, suggesting 5 a for the case of r-process Ba and 8 a in case of the neutron burst of. The value from the r-process depends sensitively on the r-process production of ¹³⁸Ba, which is, however, highly uncertain because of the predominance of s-process ¹³⁸Ba in the Solar System abundance distribution. Data for Sr are scarcer and more enigmatic, but, to first order, compatible with the inferences from Ba. X1 grains are rich in ⁸⁸Sr, while the signature in X2 grains is characterized by uniquely low ⁸⁷Sr/⁸⁶Sr ratios (down to 0.4 vs. the normal value of 0.7), possibly indicative of contributions from an s-process that was extremely weak. (author)