Materials Literature
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Anomalous EPR line intensities observed in the photoexcited triplet state of porphyrins at 100°K are discussed. A kinetic model consisting of the singlet ground state and the first excited triplet state is developed. The EPR signal intensities are expressed in terms of the kinetic rate constants and are given as linea…
An experimental study of the microwave properties of pure crystals of the organic salt tetrathiofulvalene-tetracyanoquinodimethan (TTF-TCNQ) is presented. Included are electron spin resonance and a complete study of the dielectric function, ${\ensuremath{\epsilon}}_{1}\ensuremath{-}i{\ensuremath{\epsilon}}_{2}$, from…
The effect of pressure on the solubility of CaCO 3 (calcite), CaF 2 , and SrSO 4 in water was investigated for temperatures between 0 and 35 °C for pressures up to 1000 atm. It was found that for SrSO 4 at 0 °C, and at 22 °C above 500 atm, and CaCO 3 the high pressure solubility products were appreciably lower than th…
Methyl 5-bromolevulinate (30%) is obtained directly by brominating levulinic acid in methanol. The synthesis of 5-aminolevulinic acid over the 5-phthalimido ester thus becomes a three-step one.
Transformation formulas have been derived for conversions between the various conventional systems for reporting zero field splitting data using the Hamiltonian H = D [Sz2 − (1/3)S(S + 1)] + E(Sx2−Sy2). It is recommended that all future work be reported in the standard system corresponding to the range −1≤3E/D≤0.
The dc resistivity and low-field Hall effect of the transition-metal oxide Re${\mathrm{O}}_{3}$ have been measured as a function of temperature. The samples used were oriented single crystals which were large enough for measurements to be made by a conventional four-point probe method. The samples of Re${\mathrm{O}}_{…
The polarized emission and absorption spectra of single crystals of europium ultra(penta)phosphate, EuP5O14, were measured and interpreted. Most of the observed transitions were identified and the energy level structure of the 7F multiplet defined. The over-all site symmetry is found to be extremely low (C1), but in t…
The spectrum and intensity of depolarized light scattered from binary solutions of the nematic MBBA and carbon tetrachloride have been measured. The results are interpreted in terms of pair correlations in the orientation of MBBA molecules. A systematic approach to the study of the orientational structure in nematic l…
The perovskite PrAl${\mathrm{O}}_{3}$ is known to exhibit an apparently complicated series of structural phase transitions from cubic to rhombohedral orthorhombic to monoclinic and ultimately tetragonal symmetry at temperatures of 1320, 205, and 151 K, respectively. The 1320-K cubic-rhombohedral transition is a simple…
We study the thermoelectric power of a narrow-band Hubbard chain with an arbitrary number of electrons per site. The calculations are carried out to the lowest order in the transfer integral. We find a characteristic electron density ($\ensuremath{\rho}=\frac{2}{3}$) below which the thermoelectric power is negative at…
High-resolution measurements of the Huang diffuse scattering from dislocation loops in neutron-irradiated copper and cobalt precipitates in Cu:1-wt%-Co crystals have been carried out close to the (200) and (111) reflections using a three-axis x-ray diffractometer. These measurements have been compiled in the form of d…
We have measured the luminescence spectrum of Mn-doped GaAs at liquid-He temperatures with and without an applied uniaxial stress. At zero stress we found clearly resolved donor-acceptor (DA) and band-acceptor recombination bands involving Mn. From these measurements we get a precise acceptor binding energy of 113 \if…
The influence of molecular weight (900 to 1.8 × 10 6 ) on the glass transition temperature of low polydispersity polystyrene (anionically prepared) has been studied by differential scanning calorimetry at heating rates of 5 to 80 °C min −1 . Over the range of molecular_weight studied, and at an extrapolated heating ra…
Abstract Certain rare diamonds have had epochs of growth during which they were bounded by two surface forms: normal {111} facets together with non-flat surfaces of mean {100} orientation (‘cuboid’ surfaces). Differences of lattice imperfection content in octahedral and cuboid growth sectors (i. e. in regions that ha…
A straightforward attempt to estimate the influence of the first vertex correction for a homogeneous electron gas is made. The approximation scheme is also tested on a solvable model of a core electron coupled to an electron gas.
For a constant rate G of generation of electron-hole pairs, lg J ph (J ph is the photocurrent) increases as T -1 at high temperatures and reaches a maximum value of J m at T=T m . Thereafter, lg J ph decreases as T -1 with further decrease in temperature and finally, at low temperatures, J ph becomes independent of te…
The magnetic properties of the distorted perovskite GdCrO 3 have been investigated by magnetic moment measurements in the temperature range below 100K and specific heat measurements below 10K. Measurements show that the canting of the Cr 3+ ions from a simple antiferromagnetic alignment is due to antisymmetric exchang…
Hot-pressed ceramics of the lead titanate zirconate system with different grain sizes were prepared and some of their electrical properties measured. The values of the dielectric and piezoelectric properties were analysed together with information on barium titanate ceramics already published in the literature. Many s…
An exact solution to the one-dimensional electron gas with a particular attractive-interaction strength for scattering across the Fermi "surface" is given. It is shown that conductivity enhancement occurs for physically interesting values of the coupling constants. Scaling arguments are advanced to demonstrate that th…
Abstract The molecular motion of unsintered polytetrafluoroethylene (PTFE) was studied by dynamic viscoelastic measurements. From results for variously heat treated suspension polymerized (molding powder) PTFE, the following conclusions are drawn. Molding powder, as received, has a high degree of crystallinity accordi…