Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Elastic properties of the Ta–V system: bcc Ta0.33V0.67 and C15 TaV2

Resonant ultrasound spectroscopy was used to measure the elastic constants of bcc Ta_0.33V_0.67 over the temperature range 3.5–300?K; the results were compared to earlier measurements on C15 TaV₂. The temperature dependence of the polycrystalline shear modulus is completely different in the two phases; that of the bcc phase decreases with temperature whereas that of the C15 phases increases in an anomalous fashion. This difference is consistent with a model involving doubly-degenerate levels at the X point of the Brillouin zone in the C15 phase with the Fermi level lying near the doubly degenerate level. This model accounted for the unusual behaviour of the C15 phase. Debye temperatures were determined from the ultrasonic measurements: 295?K for the C15 phase and 315?K for the bcc phase.     

The rubbing supplemented atmospheric plasma process for tunable liquid crystal alignment

Processing of the liquid crystal (LC) aligning substrates by a flux of atmospheric plasma provides controllable pretilt angle and anchoring energy, but rather poor alignment uniformity on macroscopic scale. The result is however radically improved by combination of this process with rubbing. In this case, high-quality tilted alignment is realized with a pretilt angle continuously tuned in the range 0-90°. The corresponding cells show excellent electro-optic performance. This makes combination of atmospheric plasma and rubbing processes rather attractive for industry, especially for those cases where the LC pretilt angle and anchoring energy should be patterned or continuously tuned.     

The fragmentation of negative ions of fullerene C60 trifluoromethyl derivatives

The formation and decay of gas-phase negative ions of trifluoromethylated fullerenes C₆₀(CF₃) _n (n = 2–10) were studied. The resonance electron capture mass spectra were measured to find that the main fragmentation channel of negative ions was the detachment of trifluoromethyl groups. The degree of fragmentation directly depended on the energy of electrons and reached the complete splitting off of all the CF₃ addends with the formation of C₆₀⁻ ions. The observed metastable ion signals were analyzed to determine the scheme of sequential fragmentation of negative ions.     

New interpretation algorithm for molecular negative ion resonance states

A new interpretation algorithm for molecular negative ion resonance states is proposed. This algorithm may be used when there exists a set of resonance states where the energetic distance between the resonances coincides with the corresponding distance between ionization energies. This set arises by a mechanism of electron-excited Feschbach resonance. In this mechanism, during the collision of electrons with a molecule, one electron from an occupied molecular orbital (MO) is promoted to an unoccupied MO and the striking electron is captured to the same MO. An assumed MO, excited in the set of resonances, is determined by quantum chemical calculations. This assumption is checked by the construction of correlation diagrams for electron states. The algorithm was applied to the monothiocarbonates and perfluoroalkenes and gave satisfactory results.     

Rearrangement and predissociation processes in negative molecular ions of nitrobenzenes

The reactions of resonant electron capture by the molecules of benzene nitroderivatives has been studied in the gas phase. Some fragment negative ions were found to be unstable with respect to electron autodetachment. This circumstance has been used for the determination of their structure. In particular, it has been established that the low measured appearance energy of neutral component of [M? H]^? ion beam is a result of isomerization of nitrobenzenes' molecular ion, leading to the 2‐nitrosophenol structure with the subsequent formation of the phenoxide anion in the autodetaching state. The effective yield curves of some types of fragment ions demonstrate fine vibrational structures, testifying the predissociation mechanism of ion formation. For all detected ions, the absolute cross sections of formation have been measured. Copyright © 2009 John Wiley & Sons, Ltd.