Isotopes through the looking glass

Nuclear distributions affect many aspects of atomic spectra. As an example, recent experimental results for the hyperfine anomaly in Fr isotopes are considered. These depend on nuclear charge and magnetization distributions. The variations in charge radii for these isotopes were studied earlier by measuring optical isotope shifts. The hyperfine anomalies for the odd-odd isotopes involve the neutron distributions, of interest for studies of parity nonconserving effects along a chain of isotopes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fabrication of photonic crystals in ZnS-doped glass

Three-dimensional photonic crystals were fabricated in a ZnS-doped silicate glass by use of a femtosecond pulsed laser. Woodpile structures consisting of 36 layers were produced by focusing with a 100x (1.35-numerical-aperture) objective. Attenuations of approximately 3-8 dB arising from a photonic bandgap were observed in the visible and the near-infrared regions.     

An examination of the longitudinal acoustic mode of polyethylene crystals

Chain lengths have been calculated from the peak positions of the longitudinal acoustic modes (LAM) of polyethylene single crystals grown at several different temperatures. The data are consistent with other experimental results when the crystalline elastic modulus is taken to be 3.6 × 10¹² dyn/cm². However, this is true only if the vibrations of the crystalline chain segments are unaffected by the presence of folds and cilia on the crystal surface. The LAMs of several crystal preparations were also deconvoluted with the first-order LAM of C₉₄H₁₉₀ in order to remove instrumental broadening. The band shapes of the deconvoluted spectra are consistent with the idea that the LAM of polyethylene crystals is composed of two contributions: One due to chain stems in 110 sectors and a second due to chains in 200 sectors.     

Fundamentals of liquid crystals and other liquid display technologies

A review of the fundamental concepts associated with passive displays based on liquid crystals and other liquid media is presented. The operation of dynamic scattering and field-effect type liquid crystal displays is discussed in detail. Electrophoretic, electrochromic, rotatable dipole, and liquid vapour displays are also described.     

Luminescence of doped lithium tetraborate single crystals and glass

Lithium tetraborate single crystal doped with Cu seems to be a promising new material for neutron detection. With the presence of Li and B, both having large cross section for neutron capture, efficient neutron detection is expected with high-energy deposits. In the present work, we chose 14 different dopants from Ia, Ib, IIIa, IVa and Va groups in the periodic table besides the rare earth Ce ion. The crystals were grown to a size of 20 mm in diameter and 70 mm in length by vertical Bridgman method. The grown crystals were characterized by optical transmittance and excitation–emission studies. Transmittance and emission characteristics of Ce-doped lithium borate glass are also reported.     

Raman spectroscopy of copper nanoparticle‐containing glass matrices: ancient red stained‐glass windows

A selection of red‐flashed and red‐coated medieval potash lime and 19th century soda lime stained glass pieces were studied in the laboratory using different instruments and laser wavelengths, both at lower and higher than the surface plasmon resonance (SPR) of copper. The Raman signatures of the transparent glass matrix and the red glass layers are discussed and compared with those recorded on model glasses containing a dispersion of Cu⁰ nanoparticles. Evidence is given that the conformation of the silica network in the vicinity of the metal nanoparticles differs from that of the glass matrix. Hematite and carbon traces are evidenced in the Cu⁰‐rich layers, which is consistent with the use of a combination of a reducing atmosphere and redox couples to control the growth of metallic copper particles. Copyright © 2009 John Wiley & Sons, Ltd.     

Scope for X-ray examination of packing-defect distributions in fcc crystals

A study has been made of the effects of packing-defect disposition in an fcc crystals on the diffraction pattern. A method has been devised for determining the defect-spacing distribution.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 69–73, January, 1983.     

Simulation of the passage of multiply charged ions through crystals

The effect of charge exchange processes on the angular distributions of quasi-isotropic beams of multiply charged ions passed through oriented crystals has been numerically simulated and the recently found effects of cooling and heating of the ion beams have been interpreted.     

Deconstructing the glass transition through critical experiments on colloids

The glass transition is the most enduring grand-challenge problem in contemporary condensed matter physics. Here, we review the contribution of colloid experiments to our understanding of this problem. First, we briefly outline the success of colloidal systems in yielding microscopic insights into a wide range of condensed matter phenomena. In the context of the glass transition, we demonstrate their utility in revealing the nature of spatial and temporal dynamical heterogeneity. We then discuss the evidence from colloid experiments in favor of various theories of glass formation that has accumulated over the last two decades. In the next section, we expound on the recent paradigm shift in colloid experiments from an exploratory approach to a critical one aimed at distinguishing between predictions of competing frameworks. We demonstrate how this critical approach is aided by the discovery of novel dynamical crossovers within the range accessible to colloid experiments. We also highlight the impact of alternate routes to glass formation such as random pinning, trajectory space phase transitions and replica coupling on current and future research on the glass transition. We conclude our review by listing some key open challenges in glass physics such as the comparison of growing static length scales and the preparation of ultrastable glasses that can be addressed using colloid experiments.     

Orientation effects accompanying the propagation of ultrarelativistic electrons through crystals

The results obtained by experimentally investigating the dynamics of the propagation of 1.2-GeV electrons through a thin silicon single crystal are discussed. The orientation dependences of electron scattering into a small solid angle, which are measured at various scattering angles, under conditions where the effects of crystallographic axes and planes manifest themselves are interpreted. It is shown that there are such electron-scattering directions for which the orientation “independence” of the scattering intensity with respect to a specific crystallographic plane is observed and that there also exists a crystal-axis orientation for which the region of a uniform angular distribution of the intensity is observed.     

两种玻璃微通道阵列的制作技术及比较

微孔玻璃阵列是采用原子层沉积技术制作微通道板的基底板,其微孔阵列的分布均匀性以及每个通道内壁的光滑程度,对其后续制作合格微通道板至关重要。分别采用空芯工艺和实芯腐蚀工艺来制作上述基底板,分析了两种技术的优缺点,阐述了两种方法中的关键技术,并对原子沉积技术制作的微通道板与常规工艺制作的微通道板进行了性能比较,前者的信噪比优于后者。     

Observation of multiple higher-order stopgaps from three-dimensional chalcogenide glass photonic crystals

For the first time to our knowledge the observation of near-IR multiple higher-order stopgaps in three-dimensional photonic crystals (PhCs) fabricated using the direct-laser-writing method in thick chalcogenide glass films is reported. The fabrication and etching conditions necessary to realize well-defined structures are presented. The fabricated PhCs exhibit higher-order stopgaps, which are only evident in high-quality structures. The higher-order stopgaps observed permit these high-refractive-index and high-nonlinear PhCs to be used directly as functional photonic devices operating at telecommunication wavelengths without further miniaturizing structural dimensions.     

Propagation of waves through piezo-electric α-quartz crystals

Propagation of waves in piezo-electric -quartz crystals has been studied. The slowness surfaces and the wave surfaces have been derived. The wave surface has been found to contain cuspidal points which give directions of energy concentration.I take this opportunity to thank Dr. S. Das Gupta, for suggesting the investigation and for guiding me at various stages of the work.     

Analysis of the electronic structure of crystals through band structure unfolding

In this work, we consider an alternative implementation of the band structure unfolding method within the framework of the density functional theory, which combines the advantages of the basis of localized functions and plane waves. This approach has been used to analyze the electronic structure of the ordered CuCl_xBr_1–x copper halide alloys and F⁰ center in MgO that enables us to reveal qualitatively the features remaining hidden when using the standard supercell method, because of the complex band structure of systems with defects.     

Transmission of high-frequency phonons through thin glass films

By means of phonon spectroscopy we measured the transmission of high-frequency phonons through thin glass films in the frequency range from 100 to 300 GHz. The films were prepared by thermal oxydation of silicon single crystals. Our data obtained from films with different thicknesses suggest that the observed phonon attenuation is due to scattering processes at the silicon-glass interface and not to a bulk effect in the glass film. The phonon mean free path at 300 GHz turns out to be larger than 4microm. We find evidence for the absence of inelastic scattering processes.