Mapping energy bands in layer compounds from the angular dependence of ultraviolet photoemission

Photoelectron energy spectra have been measured on the layer compounds 1T?TaSe₂ and 1T?TaS₂ at various polar angles of emission. The azimuthal angle was set to select only those photoelectrons propagating in a plane containing the ГMLA points of the Brillouin zone. The results are used to map energy-vs-wave-vector curves which are found to compare favorably with the first principles calculations of Mattheiss.     

Photoelasticity in the assessment of structural integrity

The linear-elastic fracture mechanics concept of a stress-intensity factor considered as a parameter which may be used to assess the severity of a defect in a component. The photoelastic technique is presented as a convenient method of determining stress-intensity values in complex configurations. The limitations of the experimental technique are separated from those inherent in the stress-intensity-factor concept and the required accuracy discussed. Results of a number of two- and three-dimensional problems are reviewed.     

The resistivity and superconductivity of transition metals

A recently proposed and apparently successfully validated correlation between the temperature coefficient of resistivity for transition metals and β-W compounds and the characteristic coupling constant of superconductivity theory is re-examined. It is shown that the correlation implies that these materials may be regarded as a type of semi-metal, if a model is adopted in which the electrons occupy a free-electron-like band. A corresponding modification exists to the McMillan or similar expression for the critical temperature.     

ESR. Study of the Pentacoordinated Arsenic Radical Anion [(OH)3(O)AsCH2As(O)(OH)2]=

The anion [(OH)₃(O)AsCH₂As(O)(OH)₂] has been trapped in an X-irradiated single crystal of methylene diarsonic acid. The g -tensor and the hyperfine coupling tensors of the two ⁷⁵As-nuclei have been obtained and the spin densities in the arsenic 4s- and 4p-orbitals determined.