Neutron Scattering on Magnetic Materials Under Extreme Conditions

Many materials exhibit various magnetic phenomena as a function of magnetic field, temperature and/or pressure. Usually, bulk magnetic measurements provide first information on the magnetic state of the material by measuring their response on the applied magnetic field. However, it is necessary to investigate materials also on a microscopic scale. This is often done by means of neutron scattering. In this contribution we discuss basic ideas of this method and we report on few experimental results obtained with a split-pair coil 14.5 T superconducting magnet which can be combined with dilution stick offering temperatures as low as 30 mK and/or with a small clamped-type pressure cell which offers pressure up to 1.0 GPa.     

The small momentum transfer k L o C→K S 0 C regeneration at high energies

Results of the first elastic K _S ^o regeneration experiment on carbon, using magnetic spark chamber spectrometer, are presented in the beam momentum interval 10p50 GeV/c. The d ifferentia cross section d/dt is reconstructed in the range 0·0025–t0·02 (GeV/c)² and its slopeB is found to be momentum independent with an average valueB=(65±11) (GeV/c)^–2. The results are in agreement with the calculations using the coherent production model.     

Analysis of Weinberg's algebraic relations

Implications of Weinberg's algebraic relations when only p-wave pions are taken into account are investigated. It is shown that decay rates and mass spectra of hadrons assigned to certain classes of unitary irreducible representations of theSU(4) group are in a strong disagreement with experimental data.     

Sequences with constant number of return words

An infinite word has the property R _m if every factor has exactly m return words. Vuillon showed that R ₂ characterizes Sturmian words. We prove that a word satisfies R _m if its complexity function is (m ? 1)n + 1 and if it contains no weak bispecial factor. These conditions are necessary for m = 3, whereas for m = 4 the complexity function need not be 3n + 1. A new class of words satisfying R _m is given.     

Cellulose liquefaction in acidified ethylene glycol

Wood pulp cellulose was used in a study of its catalyzed liquefaction in the presence of ethylene glycol, p-toluene sulfonic acid monohydrate or sulphuric acid being the catalysts. For this study, microcrystalline cellulose, Whatman filter paper no. 1 and cotton linters with molar masses of 76,000, 699,000 and 1,910,000 g mol⁻¹, respectively were used. This liquefaction was studied by gravimetric determinations, by X-ray diffraction analysis of the residual cellulose and by monitoring of the molar mass decrease over different time intervals, using size-exclusion chromatography. The disordered regions, even of cellulose with the highest molar mass degraded in the initial minute of liquefaction. However, the highly ordered cellulose regions remained relatively stable for a longer time. None the less, partial degradation of the highly ordered regions of the cellulose was achieved.     

Study of dehalogenation of halogenoanilines using Raney Al–Ni alloy in aqueous medium at room temperature

Abstract  

Dehalogenation of halogenated anilines by action of powdered aluminium–nickel alloy in aqueous alkaline solution at room temperature has been studied. The reaction course was monitored by means of ¹H nuclear magnetic resonance (NMR) spectroscopy. The rates of dehalogenation of 4-bromo-, 4-chloro-, 4-fluoro- and 3-chloroaniline were compared under conditions of minimum necessary excess of Al–Ni alloy as reducing agent in edetane buffer medium at pH 10.9. The dehalogenation rates of halogenated anilines decreased in the following order: 3-chloroaniline > 4-bromoaniline ≥ 4-chloroaniline > 4-fluoroaniline. On the basis of the results obtained in buffers, the dehalogenation method of aqueous solutions of halogenoanilines was verified using NaOH as the base.     

Laser Desorption Ionization of As<Subscript>2</Subscript>Ch<Subscript>3</Subscript> (Ch = S,Se, and Te) Chalcogenides Using Quadrupole Ion Trap Time-of-Flight Mass Spectrometry: A Comparative Study

Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study As₂Ch₃ (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S _p ^+/– and As _m ^+/– ) and 34 binary (As _m S _p ^+/– ) species for As₂S₃ glass, 2 unary (Se _q ^+/– ) and 26 binary (As _m Se _q ^+/– ) species for As₂Se₃ glass, 7 unary (Te _r ^+/– ) and 23 binary (As _m Te _r ^+/– ) species for As₂Te₃ material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials.

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