Enhanced superconductivity in Sr2CuO4−v

A critical review of previous investigations of the superconductivity with enhanced T_c ∼ 95 K found in Sr₂CuO_4−v shows that new physics occurs in a highly overdoped region of the cuprate phase diagram. Moreover, evidence is adduced from the literature that 30% of the oxygen sites in the CuO₂ layers are vacant; a conclusion which is at odds with the universally made assumption that superconductivity originates in stoichiometric CuO₂ layers. While further research is needed in order to identify the pairing mechanism(s) responsible for the enhanced T_c, we suggest possible candidates.     

Entfernung von Luftanteilen aus isotopen Edelgasmischungen

Bei der Isotopengewinnung durch Thermodiffusion in der Gasphase werden die Verunreinigungen, wie z. B. Luftanteile, der Ausgangsgase ebenfalls angereichert. Es kommt auch vor, daß infolge undichter Hähne in Mischungen isotop markierter Edelgase bei längerer Lagerung Luft eindringt. In derartigen Fällen ist es erforderlich, die Luftbeimengungen nachträglich zu entfernen.     

The resistive-heating characterization of laser heating system and LaB6 characterization of X-ray diffraction of beamline 12.2.2 at advanced light source

X-ray diffraction from LaB₆ standards document a precision of 478 ppm in lattice-parameter determinations for beamline 12.2.2 at Lawrence Berkeley National Laboratory′s Advanced Light Source, a facility for characterizing materials at high pressures and temperatures using laser- and resistance-heated diamond cells. Melting of Ni, Mo, Pt and W, resistively heated at 1 atm pressure in Ar, provides a validation of the beamline spectroradiometric system that is used to determine sample temperatures. The known melting temperatures, which range from 1665 to 3860 K for these metals, are all reproduced to within ±80 K.     

The effect of pressure on the superconducting transition temperature in TaSe3

The transition temperature of TaSe₃ is found to decrease for pressures up to 10 kbar at a rate -7.5 ± 0.3×10^-5 °K/bar. This unusually large decrease can only be explained by both a pressure induced lattice stiffening and a decrease in the Fermi level density of states.     

ELECTRONICALLY EXCITED PRODUCTS IN THE PHOTODISSOCIATION OF Di-9-METHYLANTHRACENE

Abstract— Although the vast majority of photochemical reactions in condensed phase lead directly to product molecules in the ground states it might be expected that in favorable cases a certain fraction of the reacting species would escape deactivation long enough to attain the product configuration adiabatically in an electronically excited state. In this communication, we report that di-9-methylanthracene, in addition to its normal diabatic course, also leads to small but finite amounts of both excited singlet monomer and excimer species. Oxygen quenching experiments seem to indicate that the monomer and excimer are derived from excited di-9-methylanthracene with little mutual interconversion. The fluorescence yields were determined for these processes in aerated solution at room temperature to be φ₁= 0·00040 ± 0·00005 and φ₂= 0·00037 ± 0·00005 for monomer and excimer species, respectively.     

ARPES studies of the electronic structure of LaOFe(P, As)

We report a comparison study of LaOFeP and LaOFeAs, two parent compounds of recently discovered iron-pnictide superconductors, using angle-resolved photoemission spectroscopy. Both systems exhibit some common features that are very different from well-studied cuprates. In addition, important differences have also been observed between these two ferrooxypnictides. For LaOFeP, quantitative agreement can be found between our photoemission data and the LDA band structure calculations, suggesting that a weak coupling approach based on an itinerant ground state may be more appropriate for understanding this new superconducting compound. In contrast, the agreement between LDA calculations and experiments in LaOFeAs is relatively poor, as highlighted by the unexpected Fermi surface topology around (π, π). Further investigations are required for a comprehensive understanding of the electronic structure of LaOFeAs and related compounds.     

Optical reflectivity in A15 compounds

Optical reflectivity at normal incidence for a series of A15 compounds shows an absorption peak at 0.7 eV for V₃Si and V₃Ge and is attributed to a critical point in the joint density of states. No such peak was found in Ti₃Sb and V₃Pt.     

Shear at twin domain boundaries in YBa2Cu3O7-x

The microstructure and strain state of twin domains in YBa2Cu3O7-x are discussed based upon synchrotron white-beam x-ray microdiffraction measurements. Intensity variations of the fourfold twin splitting of Laue diffraction peaks are used to determine the twin domain structure. Strain analysis shows that interfaces between neighboring twin domains are strained in shear, whereas the interior of these domains are regions of low strain. These measurements are consistent with the orientation relationships of twin boundaries within and across domains and show that basal plane shear stresses can exceed 100 MPa where twin domains meet. Our results support stress field pinning of magnetic flux vortices by twin domain boundaries.     

The SAMPL3 blind prediction challenge: transfer energy overview

Prediction of the free energy of solvation of a small molecule, or its transfer energy, is a necessary step along the path towards calculating the interactions between molecules that occur in an aqueous environment. A set of these transfer energies were gathered from the literature for series of chlorinated molecules with varying numbers of chlorines based on ethane, biphenyl, and dibenzo-p-dioxin. This focused set of molecules were then provided as a blinded challenge to assess the ability of current computational solvation methods to accurately model the interactions between water and increasingly chlorinated compounds. This was presented as part of the SAMPL3 challenge, which represented the fourth iterative blind prediction challenge involving transfer energies. The results of this exercise demonstrate that the field in general has difficulty predicting the transfer energies of more highly chlorinated compounds, and that methods seem to be erring in the same direction.