Investigation of low-temperature quantum diffusion in α-iron byμ + SR experiments on a single-crystal sphereSR experiments on a single-crystal sphere

The longitudinalμ ⁺-spin relaxation rate has been measured on a high-purity spherical α-iron single crystal at temperaturesT down to 20 mK and in applied magnetic fieldsB _appl parallel to 〈111〉 up to 3 T. Only above 1 K can the data be satisfactorily described by one rate constantГ. At 1 T≤B _appl≤2 T and 50 mK≤T≤300 mK, oscillations (“wiggles”) were in addition superimposed on the longitudinal relaxation. A qualitative understanding of the measurements may be achieved in terms of the increasing influence of internal stresses onμ ⁺ diffusion as the temperature is lowered.     

Infrared cyclotron resonances in InSb at megagauss magnetic fields

Cyclotron resonance was studied in reflection in InSb at room temperature using pulsed magnetic fields of up to 1.4 MG and laser-obtained wavelengths of 10.6 and 5.56 μ. At 10.6μ, four resonances were found while one resonance was found at 5.56 μ.     

Phonon scattering by electrons and low energy excitations in a metallic glass

Measurements of the thermal conductivity of a superconducting metallic glass Zr₇₀Cu₃₀ in zero field and in a magnetic field exceeding the upper critical field allow a quantitative determination of the strength of the phonon-electron scattering for the first time in amorphous metals. The temperature dependence of the residual phonon scattering by localized low energy excitations is similar to that found in insulating glasses.     

On Newton's method for entire functions

The Newton map N_f of an entire function f turns the roots off into attracting fixed points. Let U be the immediate attractingbasin for such a fixed point of N_f. We study the behavior ofN_f in a component V of \U. If V can be surrounded by an invariantcurve within U and satisfies the condition that for all z , N_f^–1({z}) V is a finite set,then it is shown that V contains another immediate basin ofN_f or a virtual immediate basin.     

Diffusionless crystal growth in rapidly solidifying eutectic systems

Using a local nonequilibrium model of solidification, experiments on rapid eutectic growth are analyzed. An analytical solution of a problem of rapid lamellar eutectic growth under local nonequilibrium conditions in the solute diffusion field is found. It is shown that solute diffusion-limited growth of a eutectic pattern is completely finished, and diffusionless growth of the chemically homogeneous crystalline phase begins to proceed at a critical point V = V(D), where V is the solid-liquid interface velocity and V(D) is the solute diffusion speed in bulk liquid. A suppression of eutectic decomposition occurs in the range V > or = V(D) that results in a growth of homogeneous crystal phase with the initial (nominal) chemical composition of the binary system.     

Supported Intermetallic PdZn Nanoparticles as Bifunctional Catalysts for the Direct Synthesis of Dimethyl Ether from CO‐Rich Synthesis Gas

The single‐step syngas‐to‐dimethyl ether (STD) process entails economic and technical advantages over the current industrial two‐step process. Pd/ZnO‐based catalysts have recently emerged as interesting alternatives to currently used Cu/ZnO/Al₂O₃ catalysts, but the nature of the active site(s), the reaction mechanism, and the role of Pd and ZnO in the solid catalyst are not well established. Now, Zn‐stabilized Pd colloids with a size of 2 nm served as the key building blocks for the methanol active component in bifunctional Pd/ZnO‐γ‐Al₂O₃ catalysts. The catalysts were characterized by combining high‐pressure operando X‐ray absorption spectroscopy and DFT calculations. The enhanced stability, longevity, and high dimethyl ether selectivity observed makes Pd/ZnO‐γ‐Al₂O₃ an effective alternative system for the STD process compared to Cu/ZnO/γ‐Al₂O₃.     

Kathodische Reduktion von Säureaziden Elektrolytische Untersuchungen an Vinylaziden, 8. Mitt.

The cathodic reduction of the O=C-N₃-system in aprotic solvent in the presence of anhydrides proves to be a convenient way to triacylammonia derivatives. Using the complexation of Li⁺ ions with the acid azide this synthetic methods can start from non-dangerous acid halides.The complex formation constant has been estimated and the chemical stability of N,N-diacylamides produced has been investigated. Mechanistic details about the role of Li⁺-ions in these electrolyses are given. Further reduction of the triacylammonia derivatives at more negative potentials results in protected aldehydic functions, i.e. 1-acyloxy-1-diacylaminomethanes, in good yields.

     

Muon depolarization in liquid3He

We report the first measurements of the positive-muon spin depolarization in liquid³He. The relaxation of the muon and muonium precession has been studied in transverse, longitudinal, and zero magnetic fields in the temperature range 0.5–2.5 K. The results are discussed in terms of two different depolarization mechanisms: recombinational depolarization (i.e. slow muonium formation) and magnetic relaxation due to the³He nuclear magnetic moments.     

Muon diffusion and trapping by defects in electron-irradiated Nb and Ta

The transverse spin relaxation of positive muons ( ⁺) has been measured on Nb and Ta after irradiation with 3 MeV electrons. In high-purity Nb the ⁺ diffusivity derived from the trapping at irradiation-induced defects above 100 K is explained in terms of adiabatic hopping. At lower temperatures there is evidence for the dominating processes to be fewphonon incoherent tunnelling and coherent hopping. Annealing results in the formation of new defects capable of trapping the ⁺. In Ta at least two types of irradiation-induced defects capable of trapping ⁺ survive up to annealing temperatures of 400 K.