Temperature sensors and optical sensors

The dependence of temperature on the fluorescence lifetime and fluorescence intensity ratio using Stark sublevels and thermally coupled (close lying) levels in triply ionized rare earth ions, doped into a variety of glasses and fibers, have been reviewed. Also, it is claimed that not only for the two closely lying levels of triply ionized rare earth ion of the same kind, but also for two different triply ionized rare earth ions, having their excited levels very close to each other, may be used to monitor the temperature. PACS 42.70.Ce     

Self-organized ZnAl2O4 nanostructures grown on -sapphire

Self-organized ZnAl₂O₄ nanostructures with the appearance (in SEM) of high aspect ratio horizontal nanowires are grown on uncatalysed c-sapphire by vapour phase transport. The nanostructures grow as three equivalent crystallographic variants on c-sapphire. Raman and cathodoluminescence spectroscopy confirm that the nanostructures are not ZnO and TEM shows that they are the cubic spinel, zinc aluminate, ZnAl₂O₄, formed by the reaction of Zn and O with the sapphire substrate.     

Study of photon-induced L3 vacancy alignment for elements La to U

Alignment of photon-induced L₃ vacancies is studied in rare earth and highZ elements at energies of experimental interest, near thresholds to 60 keV, under nonrelativistic dipole approximation. Numerical calculations of the matrix element are undertaken to produce theoretical data for comparison with the experimental findings. The A₂ values being s>0.1 at photoelectron energies <20 keV are certainly higher than 5–8% uncertainties quoted in experimental results. Present findings are from a very basic model, hydrogen-like and can further be treated as reference to observe the impact of screening, relativistic, multipole and retardation corrections to the model     

The case of missing incommensurate smectic A phases

Two binary mixtures of polar liquid crystal materials were previously reported to exhibit three incommensurate smectic A phases predicted for such materials on the basis of phenomenological theory. Results of our recent high-resolution X-ray scattering experiments show that no incommensurate phases exist in the two systems. Wide coexistence regions are found at first order transitions between various frustrated smectic phases of these mixtures. These regions were previously identified as the incommensurate smectic A phases. The phase diagrams of the two systems determined with high-resolution X-ray technique are shown to be in excellent agreement with Baroisa-Prost-Lubensky theory.     

Study of the effect of swift heavy Ni ion irradiation on ruby single crystal by using the XANES and EXAFS techniques

We have made the XAFS measurements at the Cr–K-edge on natural Indian ruby single crystals (corundum) and its two irradiated samples with fluence 1×10¹² Ni⁶⁺ and 5×10¹² Ni⁶⁺ ions/cm². Irradiated samples show interesting changes in their physical appearance. XANES measurements show progressive decrease in Δ_oct value on increase of Ni fluence in irradiated samples. EXAFS measurements on these samples show decrease in Cr–O distance on increase of Ni fluence. Lowering of Δ_oct value is correlated with the increase of Cr–O distance.