Materials Literature
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The absorption coefficient, reflectivity, and electroreflectance of SrTi${\mathrm{O}}_{3}$ in the neighborhood of the fundamental absorption edge are reported. The absorption coefficient shows an exponential rise with incident energy (Urbach rule) over five orders of magnitude. Its logarithm has a slope of $\frac{1}{\…
The frequency wave-vector dispersion relation for the normal modes of vibration of ${\mathrm{Li}}^{7}$F at 298\ifmmode^\circ\else\textdegree\fi{}K has been measured by means of slow-neutron inelastic scattering techniques. Triple-axis crystal spectrometers at two reactor facilities at the Oak Ridge National Laboratory…
A theoretical and experimental study was made of the shift in atomic core-electron binding energies caused by the chemical environment. Two models are presented to account for these “chemical shifts.” The first uses an energy cycle to break the core-electron binding energies into a free-ion contribution and a classica…
Abstract Bei Polyäthylen kann die senkrecht zur longitudinalen Lamellenoberfläche gemessene Kristalldimension l und damit der Schmelzpunkt der kristallinen Bereiche durch die Wahl der Kristallisationsbedingungen in weiten Grenzen variiert werden. Aus der nach der T HOMSON ‐Gleichung zu erwartenden und auch gefundenen…
The sharp-line spectrum of exchange-coupled chromium ion pairs has been investigated with the aid of piezospectroscopic techniques. The lines shift and split under stress in characteristic ways which permit positive identification of a principal fluorescent transition with each of the four nearest-neighbor pair types.…
The modified potassium dihydrogen phosphate (KDP) model of a two-dimensional ferroelectric with the inclusion of an arbitrary electric field $\mathcal{E}$ is considered. The nature of the phase transition is unaffected by the inclusion of an external field, whereas the transition temperature depends on $\mathcal{E}$ w…
Polarized Raman spectra of tetragonal BaTi${\mathrm{O}}_{3}$ have been obtained at room temperature with He-Ne laser excitation. Using several different crystallographic directions for the phonon wave vector q, most of the vibrational modes for q\ensuremath{\sim}0 have been classified using Raman data alone. Three pai…
The existence of two forms of cobaltous oxide, CoO(I) and CoO(II), has been established by M\"ossbauer, x-ray, and chemical techniques. CoO(I) has the NaCl structure as determined by a well-resolved powder x-ray pattern. Its density is measured to be 6.4 g/${\mathrm{cm}}^{3}$ from both x-ray and direct macroscopic exp…
In connection with the Cochran theory of ferroelectricity, the thermal conductivity has been investigated in SrTi${\mathrm{O}}_{3}$ between 5 and 300\ifmmode^\circ\else\textdegree\fi{}K and in KTa${\mathrm{O}}_{3}$ between 2.5 and 300\ifmmode^\circ\else\textdegree\fi{}K. For temperatures above its maximum value, the c…
The complex dielectric constant of Rochelle salt has been measured at frequencies from 2.5 to 13 GHz, and at 155 MHz. The measurements were made in a temperature range from -50 to 45\ifmmode^\circ\else\textdegree\fi{}C which includes the ferroelectric region and significant parts of both paraelectric regions. Measurem…
The consequences of a simple type of exchange interaction between free charge carriers in a broad energy band and localized magnetic moments are discussed. The interaction causes a splitting of the energy bands into bands for the two spin directions. It also leads to spin-disorder scattering of the charge carriers. Th…
The change in the free energy that occurs when electric and magnetic fields are simultaneously applied to a magnetoelectric medium is calculated. It is shown that a quadratic form related to this change in the free energy is positive definite, from which it follows that all elements of the magnetoelectric-susceptibili…
The electron-spin-echo phase memory ${T}_{M}$ has been studied both experimentally and theoretically for the specific case in which it is limited by the lattice relaxation processes occurring in the sample. The relevant mechanism is as follows. Lattice relaxation of any spins, whether or not they belong to the species…
Received 8 November 1968DOI:https://doi.org/10.1103/PhysRevLett.20.798©1968 American Physical Society
Two polymorphic forms of aspirin were characterized; the rates of dissolution of single crystals and of tablets were studied. One forms dissolves 50 percent faster than the other.
Hypervelocity impact effect on structural honeycomb spacecraft wall configurations, stressing design and wall thickness parameters
X-ray and electron spin resonance studies are reported of the paramagnetic material [(CH 3 ) 4 N] 2 Cu[S 2 C 2 (CN) 2 ] 2 in single-crystal form, and also of this compound diluted in its diamagnetic nickel analogue. This mixed crystal is triclinic, and the copper ion has axial magnetic symmetry, with the Hamiltonian p…
Abstract It is reported that mats formed by the sedimentation of single crystals of methyl‐ and ethyl‐branched polyethylene exhibit strength and ductility comparable with that of melt‐crystallized films. In fact, in the case of methyl‐branched polymers, extensions of up to 50× were obtained on cold drawing. Observatio…
Abstract Die bei 709°C durch peritektische Reaktion gebildete Hochtemperaturphase hat die Zusammensetzung Cu 9,5 As 4 , sie kristallisiert kubisch mit einer Formeleinheit im Elementarkörper. Bei langsamem Abkühlen zerfällt die Hochtemperaturphase peritektoid zwischen 360 und 340°C in β‐Cu 3 As und As. Durch Abschrecke…
Abstract Phase relationships of isotactic polypropylene in various organic diluents were investigated. The diluents used were aliphatic alcohols, alkyl phenols, aryl phenols, diphenyl derivatives, alkyl aryl ethers, esters, and others. Among the diluents examined, n ‐butyl alcohol, p‐tert ‐butyl phenol, p‐tert ‐amyl p…