Materials Literature
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The effects of various technological processes on the electronic structure of vanadium-doped TiO2 crystals have been studied. The EPR spectra give clear evidence that by suitable thermal treatment in a reducing atmosphere the tetravalent vanadium ions can be transferred from the substitutional to the interstitial posi…
The energy band structure and optical properties of the zinc-blende semiconductors $3C$-SiC, BP, and BN have been calculated using a nonlocal version of the empirical-pseudopotential method. The results of this investigation are discussed and compared to experiment. The agreement between theory and experiment is found…
A unified study is presented of the infrared behavior of the second-order electric susceptibilities ${\ensuremath{\chi}}^{(2)}$ in semiconducting compounds for both longitudinal and transverse fields. The molecular model used previously for the calculation of ${\ensuremath{\chi}}^{(2)}$ for frequencies above the latti…
The electroreflectance spectra of solution-grown ${\mathrm{Ga}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}\mathrm{P}$ alloys were measured at room temperature in the whole range of composition. The variation of the ${E}_{0}$, ${E}_{1}$, ${E}_{0}^{\ensuremath{'}}$, and ${E}_{2}$ energies with concentration is reported: It is…
New reflectance spectra are obtained for amorphous ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ and ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$. The spectra contain features not reported in earlier studies. Analysis of the spectra in terms of damped Lorentzian oscillators, combined with new Raman data, gives further support to th…
The bend and splay elastic constants of MBBA were measured over its nematic temperature range. The ratio of the two constants is 1.25± 0.05. The temperature dependence of the elastic constants is found to be adequately described by the simple mean-field models. A comparison is made between viscosity coefficients obtai…
The phosphorescence from benzophenone crystals has been investigated as a function of temperature between 7 and 77°K. Three types of T → S emission are detected and the importance of vitreous defects in crystalline benzophenone is examined.
The photoelectron spectra of vinyl bromide, cis- and trans-1,2-dibromoethylene and 2-bromopropene have been obtained. Interaction of the bromine "lone pair" electrons with those in the C=C π bond is discussed. The assignments are considered in relation to the chloroethylenes. The spectra provide experimental evidence…
It is assumed that the one-electron density function for a molecular crystal can be determined from x-ray diffraction data with the use of generalized x-ray scattering factors. The relationship between several physical properties and electron population parameters are given. These include molecular dipole moments and…
Energy bands of SrTi${\mathrm{O}}_{3}$ have been computed ab initio using a nonrelativistic self-consistent-field (SCF) procedure based upon the linear-combination-of-atomic-orbitals or tight-binding formalism. A slightly extended multicentered-atomic-orbital basis was used and integrals over them were evaluated in ke…
Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Ikram Morcos; Surface Tension of Stress‐Annealed Pyrolytic Graphite. J. Chem. Phys. 15 August 197…
The Raman spectra of the $2H$ and $4H$ structures of ZnS have been measured between room temperature and 60 K, and compared with the spectra from zinc blende ZnS. The observed phonons in each case are in good agreement with those expected from the known structural differences.
A phenomenological band-theoretic model for photoelectric emission which includes the effects of energy loss due to phonon scattering is developed. The model is applicable near threshold when the optical absorption depth is large compared to the phonon scattering length of hot electrons, and is particularly useful for…
Studies of the infrared-pumped visible luminescence of NaYF4 : Yb, Er show it to have at least twice the visible output of YF3 : Yb, Er when pumped with a narrow-band excitation source at the optimum frequency. It is also free from saturation effects until very intense excitation levels are reached. The mechanism for…
Vacuum-deposited films now replace the familiar ``rubbing'' process in substrate preparation for liquid-crystal cells. Films deposited at an angle provide an oriented surface for alignment of nematic liquid crystals far better than the well-known ``rubbed'' plate. The oblique deposit causes a film growth in a preferre…
The ac conductivity of scandium-oxide thin films in the audio-frequency range at temperatures between 4 and 295 K has been measured. The frequency-dependent component of the conductivity was found to obey an equation of the form ${\ensuremath{\sigma}}_{1}(\ensuremath{\omega})=A{\ensuremath{\omega}}^{s}$, where $\ensur…
The optical absorption spectrum of Tm 3+ in TmVO 4 has been studied to obtain information on the cooperative Jahn-Teller phase transition which occurs in this material at 2.14+or-0.04 K. The temperature dependence of the absorption lines below 2.14 K was in good agreement with the predictions of molecular field theory…
The adsorption of di- and tri-methylamine has been studied at 280 and 276°K, respectively, on a range of silica gels and on silica–alumina. Adsorption–desorption isotherms and isothermal calorimetric heats of adsorption were measured. Heats of adsorption for di-methylamine on silica gel varied from 29.0 kcal/mol at θ…
A phase diagram of the semiconducting uniaxial ferroelectric antiferromagnetic Fe1-xS covering the available experimental evidence is given.
Two aminoacylases [EC 3. 5. 1] from Mycobacterium smegmatis were purified as single protein components, based on analysis by ultracentrifugation and electrophoresis. The enzyme, “short acyl aminoacylase” which exhibited hydrolytic activity toward N-short chain fatty acyl amino acids, had a sedimentation coefficient s2…