La48Br81Os8: isolated clusters in an unusual superstructure with significantly greater intercluster bonding

Exploration of reactions in the La-Br-Z system for Z = Fe, Ru, and Os in welded Nb containers at 900-950 degrees C resulted in only the title phase. The La48Br81Os8 stoichiometry is very close to that of known triclinic Pr6Br10Os but with an approximately 32-times larger cell, 138 independent atoms, and completely different intercluster connectivities in a complex monoclinic superstructure (a = 33.076(5) A, b = 23.466(3) A, c = 23.537(2) A, beta = 110.701(4) degrees, P2(1)/c (No. 14), Z = 4, 23 degrees C). Tetragonally compressed, approximately 16 e- lanthanum octahedra centered by Os are heavily interbridged by Br, including Br(f-a) (f = face) and Br(i-a-a) functions, to increase coordination numbers about some Br (to 4) and La (to 6) and to give an average of 19.63 bonded Br/La6Os vs the usual 18. These result in a cell volume 10% less than for an equivalent (hypothetical) La6Br10Os and Br-Br contacts as short as 3.30 A. Increased polar La-Br interactions presumably drive these changes. Optimal atom sizes for this structure have been found so far only in this novel compound.     

Radiation damage,defects and surfaces

The status of radiation damage and defects in bulk metallic, covalent and ionic systems is reviewed, including damage production processes, defect configurations and defect migration mechanisms. These results are then considered in the vicinity of a surface. The physical surface and the electronic surface can alter bulk defect processes, but little experimental data is available on defect processes in the vicinity of the surface.     

A partial-wave analysis of the neutral 3π system produced in the reaction π−p → (π+π−π0) n at 12 and 15 GeV/c

Data on the charge-exchange reaction π^?p → (π⁺π^?π⁰)n have been taken at beam momenta of 12 and 15 GeV/c, using the CERN Omega Multiparticle Spectrometer. A partial-wave analysis has been made of the (3π)⁰ system. We observe both natural and unnatural spin-parity production. The natural parity states can be identified with established resonances. In addition a natural spin-parity enhancement is observed at a mass of about 2 GeV/c² with J^P = 4⁺ preferred. We have called this effect the A₂¹ (2030). The unnatural spin-parity production found is consistent with reggeized Deck model predictions. No unambiguous A₁ or A₃ production is observed.     

Production of A20and ω1 (1675) in the reaction π−p → π+π−π0n at 12 and 15 GeV/c

Data on the reaction π^?p → π⁺π^?π⁰ have been taken at 12 and 15 GeV/c with the CERN Omega multiparticle spectrometer. In a 3-pion partial-wave analysis strong production of $\text{A}{}_2{}^0\text{(1310)}\text{and}\text{ω}{}^1\text{(1675)}$ is observed. Total and differential cross sections are determined and density matrix elements presented as a function of t in the t- and s-channel frames. The energy dependence of A₂⁰ production is studied, and a comparison of $\text{ω(780),}\text{A}{}_2{}^0\text{(1310)}\text{and}\text{ω}{}^1\text{(1675)}$ production is made.     

The determination of tellurium in weathered outcrop,mineralized and barren rock

Sensitive and specific methods have been developed for the determination of tellurium in a wide variety of rocks and minerals. X-ray fluorescence is used for concentrations above 1 μg g^-1 and carbon furnace atomization a.a.s. for concentrations of 0.01–1μg g^-1. The tellurium is separated by precipitation as elemental tellurium after dissolution in acid; alternative dissolution procedures have been investigated.