Materials Literature
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Abstract Crystalline 9-cyanoanthracene undergoes photodimerization to give the trans dimer which is unexpected on the basis of the topochemical preformation theory. The possibility that the reaction occurs at defects is investigated; and the nature of the structural imperfections are described, as are also the types o…
Electric-field-induced scattering by normally Raman-inactive LO phonons is observed in the IV-VI-compound (NaCl structure) semiconductors PbTe and SnTe with Pb films on $p$-type samples to induce energy-band bending. The observed Raman peaks correspond to unscreened $q\ensuremath{\approx}0$ LO phonons. A discussion of…
For a duration of several times ${10}^{\ensuremath{-}12}$ sec, TO modes are excited to an occupation number exceeding the equilibrium value (at 300\ifmmode^\circ\else\textdegree\fi{}K) by more than thirteen orders of magnitude. The relaxation times of these phonos are measured directly and found to agree with the know…
A precision study has been made of the temperature dependence of the Hall effect and resistivity in five carefully selected natural semiconducting diamonds. The donor and acceptor concentrations in each sample have been calculated from the Hall effect data, and the acceptor concentrations are shown to correlate excell…
The thermal diffusivity of BN has been measured from 100 K-800 K using a 'flash' method; published specific heat data has been used to evaluate the thermal conductivity. Over a limited temperature range the results have been confirmed by steady state measurements. The thermal conductivity parallel to the deposition pl…
A short study of the anomalous wavelength dependence of photoresponse in insulating single crystals of GaSe is given. This anomaly can be roughly related to the number of structure defects in the crystal. From the nature of the effects it is concluded that the origin of the anomaly differs somewhat from the situation…
The phosphorescence spectra of benzaldehyde-h6, −1d1, −4d1, −3, 5d2 and −d6 have been studied optically in close packed matrices (acetophenone and methyl benzoate) and relaxed matrices (methylcyclohexane and perfluoro-n-hexane) at 4.2°K. All the spectra were sharp and could be analyzed vibrationally. In the close pack…
Past analyses of the kinetic equations governing thermally stimulated luminescence and conductivity have invariably involved certain approximations; however, the validity of these approximations has never been explicitly determined. In this paper we give a procedure for determining the conditions under which the appro…
An EPR study has been undertaken of Cr3+ in LiGa5O8. The site symmetry is rhombic and the system can be described by the spin Hamiltonian, H=gβH·S+D [Sz2− 1 3S (S+1)]+E (Sx2− S y2), where D=0.331±0.002 cm−1, E=0.018±0.002 cm−1, and the average g value, assumed isotropic, is 1.980±0.005. The axes of the spin Hamiltonia…
The polarized infrared and Raman spectra of SbSI have been measured in the paraelectric and the ferroelectric phases as a function of temperature. The frequencies and the symmetries of most of the optically active phonons have been determined in both phases. A strongly temperature-dependent $A$ mode which is simultane…
α-Zn 3 (VO 4 ) 2 , the low temperature form of this compound, crystallizes in the orthorhombic space group Cmca with a = 6.088(3), b = 11.489(3), and c = 8.280(3) Å and Z = 4. A total of 726 unique reflections were recorded from integrated precession photographs or with a manually set scintillation counter and used in…
Thermal-conductivity measurements have been made on crystals of $\ensuremath{\beta}$-boron, ${\mathrm{B}}_{12}$${\mathrm{P}}_{2}$, ${\mathrm{B}}_{12}$${\mathrm{As}}_{2}$, and Y${\mathrm{B}}_{66}$ from 3 to 300 K. Phonons are the dominant carriers of heat, and their mean free paths range from ${10}^{\ensuremath{-}5}$ c…
The statistical theory of paramagnetic clusters described in the literature to date is largely restricted to ``spin-only'' magnetism for which orbital angular momentum is quenched, or enters the calculations only as a trivially modified g factor. This paper discusses the extension of the theory to magnetic ions for wh…
The thermal conductivity of vitreous Si${\mathrm{O}}_{2}$, Se, and silica- and germania-based glasses has been measured between 0.05 and 100 \ifmmode^\circ\else\textdegree\fi{}K. Comparison with earlier work on noncrystalline solids shows that they all have the same conductivity within a factor of 5 over the entire te…
The Raman scattering spectrum of V${\mathrm{O}}_{2}$ is reported between 4.2 and 600\ifmmode^\circ\else\textdegree\fi{}K. In the semiconducting monoclinic phase only sharp phonon structure is observed. The metallic rutile phase exhibits a pronounced softening and damping in the observed phonon spectrum. This evidence…
Significant swelling (1 to 10 percent due to small voids have been found in stainless steel when it is exposed to fast neutron doses less than expected in commercial fast breeder reactors. The main features of this new effect are: (i) the voids are formed by the precipitation of a small fraction of the radiation-produ…
The diffraction of plane electromagnetic waves by ideally conducting bodies, the surface of which have discontinuities, is investigated in the report. The linear dimensions of the bodies are assumed to be large in comparison with the wavelength. The method developed takes into account the perturbation of the field in…
Accuracy of the beam-bending method used in viscosity measurements of glass is determined by using electric-melting fused quartz. Average viscosity of ten specimens is obtained as (5.96±0.16)×10 12 poise at 1200°C with the standard deviation of 8%. Limits of specimen dimensions applicable in this method is determined…
Abstract Potassium is deposited as kainite and/or carnallite by solar evaporation of sea and inland bitterns, respectively. The solubility of this natural kainite in water was found to be at 20 g magnesium chloride per 100 g water as against at 27.5 g obtained with synthetic kainite. As a result, the equilibrium data…
Summary Yttrotungstite occurs at Kramat Pulai mine, and at Tapah, Kinta, Perak, Malaysia, as yellow earthy material and as monoclinic laths, elongated along [001], flattened, and always twinned, on {100} to pseudo-orthorhombic symmetry, and frequently bevelled by {110}; crystals are very rarely terminated by {101}. γ…