Mössbauer diffraction on ferroelectric Li2Ge7O15

Room temperature Mössbauer diffraction experiments on Li₂Ge₇O₁₅ are reported. Due to the presence of additional lattice points near the surface of the Ewald sphere of the used geometry a minimum appears in the inelastically scattered contribution of the 0-0-8 reflection. No elastically scattered intensity is observed at the angular range corresponding to the 0-0-9 reflection supporting Pbcn as space group at room temperature. The calculated ratio of the first order thermal diffuse scattered intensity included, in the background to the total thermal diffuse scattered intensity differs strongly from the experimental results.     

Über Herstellung von Quecksilbersolen durch Reduktion

Zusammenfassung Es wurden zwei Methoden zur Darstellung von kolloidem Quecksilber durch Reduktion von Merkurisalzen ausgearbeitet. Der Dissoziationsgrad der angewandten Merkurisalze ist von gro?em Einflu? auf das Gelingen der Soldarstellung. Es erwies sich, da? nur dann bei der Reduktion von Quecksilbersalzen das Metall in kolloider Form erhalten wird, wenn schon als Zwischenprodukt ein Sol auftritt. Und zwar ist Bedingung, da? dieses Sol Teilchen enth?lt, welche, wie die von Quecksilbersol, negativ geladen sind. Diese Bedingung wird z. B. von Merkuro-, nicht dagegen von Merkurioxydsol erfüllt.     

Photoemission on highT c superconductors

Ultrathin-layer (AlAs) _m (GaAs) _m superlattices withm = 1, 2, and 3 were grown by molecular beam epitaxy and characterized by x-ray diffraction and photoluminescence measurements. The appearance of distinct satellite peaks around the Bragg reflections demonstrate the formation of high-quality layered crystals. The observed luminescence shows a maximum at 2.033 eV form = 3, and the emission energy decreases form = 2 andm = 1 as well as for them = 4 superlattice. This result for the monolayer superlattice is in good agreement with recent theoretical calculations, and it shows that the (AlAs)₁(GaAs)₁ superlattice represents a new artificial semiconductor material with novel electronic properties.On leave from Mitsubishi Electric Corp., Central Research Laboratory, Amagasaki, Hyogo 661, JapanOn leave from Institute of Semiconductors, Academia Sinica, Beijing, PR China     

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Search for direct photons from S-Au collisions at 200 GeV/nucleon

The CERES experiment has measured inclusive photon production in S-Au collisions of 200 GeV/nucleon at the CERN SPS. No evidence for direct emission of photons was found. For the kinematic region 2.1<y<2.65 and 0.4 GeV/c<p??<2.0 GeV/c the yield andp??-dependence of the observed photons are well reproduced by hadron decays. Furthermore, their production rate is found to be proportional to the charged particle density. The systematic errors comparing the measured and expected photon yield result in an upper limit of 14% for the emission of direct photons in central S-Au collisions. For a photon source with a yield depending quadratically on the charged particle density the limit can be reduced to 7%.     

A convergent and precise finite element scheme for Landau–Lifschitz–Gilbert equation

In this paper, we propose a new scheme for the numerical integration of the Landau–Lifschitz–Gilbert (LLG) equations in their full complexity, in particular including stray-field interactions. The scheme is consistent up to order 2 (in time), and unconditionally stable. It combines a linear inner iteration with a non-linear renormalization stage for which a rigorous proof of convergence of the numerical solution toward a weak solution is given, when both space and time stepsizes tend to \(0\) . A numerical implementation of the scheme shows its performance on physically relevant test cases. We point out that to the knowledge of the authors this is the first finite element scheme for the LLG equations which enjoys such theoretical and practical properties.