Extended Affine Root Systems I (Coxeter transformations)
§ 1. Root System Belonging to a Quadratic Form § 2. Marked Extended Affine Root System (R
Materials Literature
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Potential models for ionic oxides
The authors present a systematic approach to the derivation of empirical potential parameters for binary oxides; they also consider their modification for use in mixed oxide systems. Shell-model potentials are used but, unlike the case of the alkali halides within which polarisability and short-range interaction param…
[2 + 2] Photocycloadditions in the Synthesis of Chiral Molecules
A strategy for the synthesis of chiral molecules that receives growing popularity among organic chemists employs the photochemically mediated [2 + 2] cycloaddition reaction. These reactions can be performed on a multigram scale and often proceed with high yield and with stereocontrol. These features, in combination wi…
Electrically Conductive Metallomacrocyclic Assemblies
The design, synthesis, and study of electrically conductive molecular and polymeric substances constitute a new scientific endeavor involving the interaction of chemists, physicists, and materials scientists. The strategies, developments, and challenges in these two closely related fields are analyzed via a class of m…
Fluorescence spectrum, energy level scheme and crystal field analysis of europium(+III) doped lanthanum magnesium borate LaMgB5O10:Eu3+
The fluoresence spectrum of europium(+III) doped LaMgB5O10 was studied at 77 and 300K under U.V. and visible dye laser excitation. A phenomenological crystal field analysis was conducted on the basis of the observed 34 7 F 0-5 level energies. A descending symmetry method from D 2d to C 2v and C 2 symmetries was used i…
The energy and elastic dipole tensor of defects in ionic crystals calculated by the supercell method
The energy, the elastic dipole tensor and the entropy of point defects in ionic crystals are usually calculated by the Mott-Littleton approach, which treats a single defect in an infinite crystal. The authors suggest that there may be advantages, particularly for the dipole tensor and the entropy, in performing the ca…
The superposition of thermal activation in dislocation movement
The thermally activated movement of a dislocation intersecting a small density of strong point obstacles imbedded in a large density of weak obstacles is calculated analytically by modelling the geometrical correlations. The superposition of the flow stresses for the isolated processes is only valid for zero temperatu…
Derivatives of transmittance and reflectance for an absorbing multilayer stack
The formulas for a fast computation method are derived for the derivatives of transmittance and reflectance with respect to the thickness d, the refractive index n, and the extinction coefficient k of any layer in an absorbing multilayer stack.
Single-layer antireflection coatings on absorbing substrates for the parallel and perpendicular polarizations at oblique incidence
Explicit equations are derived that determine the refractive index of a single layer that suppresses the reflection of p- or s -polarized light from the planar interface between a transparent and an absorbing medium at any given angle of incidence. The required layer thickness and the system reflectance for the orthog…
Electric-field-induced first-order Raman scattering in pure KCl and KBr
Electric-field-induced first-order Raman scattering (FIFORS) by the normally Raman inactive LO and TO phonons is observed in the pure alkali halide crystals KCl and KBr under electric fields of 2.5\ifmmode\times\else\texttimes\fi{}${10}^{5}$ V/cm. Cross sections for the FIFORS--active modes are calibrated and the resu…
Effect of pressure on the Raman and electronic absorption spectra of naphthalene- and perylenetetracarboxylic dianhydrides
The effect of pressure on the optical absorption and Raman spectra of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) and on the optical absorption edge in 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) was investigated, using a diamond anvil cell. In NTCDA the absorption edge shifts red by about 8000 cm−…
Native defects in undoped semi-insulating CdSe studied by photoluminescence and absorption
Recombination of carriers in semi-insulating undoped CdSe was studied using infrared absorption and both the polarization and excitation power dependence of the photoluminescence spectra. The photoluminescence measurements showed that a deep donor and a shallow-acceptor state dominate the recombination process, which…
Saturation photoconductivity in CdIn 2 S 4
At excitation energies corresponding to definite extrinsic transitions in ${\mathrm{CdIn}}_{2}$${\mathrm{S}}_{4}$, the photoconductivity is investigated as a function of light intensity over a maximum of 12 orders of magnitude ${(10}^{16}$ to ${10}^{28}$ photons/${\mathrm{m}}^{2}$ sec). For certain wavelength ranges a…
Low-temperature heat transport by charge carriers in doped semiconductors
The electronic contribution to the thermal conductivity in degenerate semiconductors has been measured at low temperature in fine-grained ceramic samples in which the lattice thermal conductivity is reduced by grain-boundary scattering of the phonons. The validity of the Wiedemann-Franz-Lorenz law has been demonstrate…
Dielectric Properties on 72 K Phase Transition of KOH-doped Ice
The temperature dependence of the dielectric dispersion of KOH-doped ice was measured at the temperature range from 55 K to 90 K at frequencies 0.002 Hz∼1 Hz. The phase transition at 72 K was clearly observed only at the heating stage from the temperature dependence of the dielectric constant and the relaxation time.…
Site-selection spectroscopy and energy transfer studies of Eu3+ ions in glass hosts
Time-resolved site-selection spectroscopy techniques using a pulsed tunable dye laser were used to investigate the spectral structure and dynamics of Eu3+ ions in six oxide and one fluoride glass hosts. Network modifier ions were found to be important in determining the details of the spectral structure which can be r…
Weak Localization in Graphite
Conductivity and magnetoconductivity have been measured for various kinds of graphite crystals at low temperatures down to 0.03 K. Anomalous behaviours have been found in polycrystalline (but well oriented) specimens of graphite. At low temperatures below 0.1 K, the conductivity shows T 1/2 dependence in and without m…
Spontaneous decay of TA phonons
Anharmonic decay of high-energy transverse acoustic (TA) phonons satisfying \ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\gg}${k}_{B}$T is studied taking account of the elastic anisotropy of real crystalline solids. Dispersive effects are assumed to be small. We find that the decay rate is very anisotropic. The p…
Surface dipole and Fermi-level position on clean, oxygen-, and water-covered cylindrical Si crystals: A photoelectron spectroscopy study
Photoelectron spectroscopy, including emission from the Si 2p core level, was used to investigate the orientation dependence of the photoionization threshold \ensuremath{\xi}(\ensuremath{\alpha}) and the surface position of the valence-band edge below the Fermi level, ${E}_{\mathrm{VFS}}$(\ensuremath{\alpha}), on a cy…
Onset of hopping conduction in carbon-ion-implanted diamond
The conduction of diamond implanted with carbon ions, at a target temperature of 250 \ifmmode^\circ\else\textdegree\fi{}C, was studied as a function of ion energy using the electrical sheet resistance of these implanted layers as a probe. It was found that ion doses at which the onset of hopping conduction occurs incr…