Materials Literature
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The structure of regenerated cellulose is shown by x-ray diffraction to be comprised of an array of antiparallel chain molecules. The determination was based on the intensity data from rayon fibers and utilized rigid-body least-squares refinement techniques. The unit cell is monoclinic with space group P2(1) and dimen…
The frequent practice of combining X-ray and neutron diffraction for distinguishing vibrational smearing from charge deformation due to chemical bonding is neither necessary nor completely satisfactory. The two effects occur principally in distinct regions of real and reciprocal space. They can be distinguished by X-r…
The present situation in theoretical and experimental studies on one-dimensional magnetic systems is fully discussed. Equal-time as well as the dynamic properties are included with an emphasis on the latter. Four model systems are examined in detail: TMMC (Heisenberg antiferromagnet), CsNiF3 (planar ferromagnet), CoCl…
Share Icon Share Twitter Facebook Reddit LinkedIn Reprints and Permissions Cite Icon Cite Search Site Citation G. Ertl, J. Küppers, Robert L. Park; Low‐Energy Electrons and Surface Chemistry. Physics Today 1 March 1976; 29 (3): 57. https://doi.org/10.1063/1.3023372 Download citation file: Ris (Zotero) Reference Manage…
Collagenase cleavage of human Type II and III collagens has been studied using a highly purified preparation of rabbit tumor collagenase. Progress of the reactions in solution was followed by viscometry and the results indicated that under the conditions employed Type III collagen molecules were cleaved at approximate…
Abstract The 1.945eV band is the dominant end product of annealing radiation damage in diamonds containing isolated substitutional nitrogen atoms. In this paper uniaxial stress experiments are described which show the band to be a transition between A1 (ground) and E (excited) electronic states of a trigonal centre, t…
The mixed-basis method has been used to compute the energy bands of an idealized $\ensuremath{\beta}$-cristobalite form of silicon dioxide. A direct-forbidden optical-absorption edge is predicted. Peaks in observed x-ray emission and optical-absorption spectra identified with critical points in the densities of states.
Infrared absorption spectra of ferroelectric NaNO2 crystals are obtained in the frequency range 700 to 950 cm−1 with polarized infrared rays. Periodic fine structures with spacing 4.35 cm−1 are observed for c-polarized rays in some of the specimens. These fine structures are attributed to the summation band of the v2…
X-ray and magnetic studies have been carried out for the f.c.c. CoV alloys containing V up to 30.1 at%. The X-ray measurements showed that the lattice parameter does not obey Vegard's law in the whole composition range observed in this work. The composition dependence of the lattice parameter can be related to the ma…
Angle-resolved photoemission, using synchrotron radiation, from the chemisorption system W(001) + H shows a very large doublet of peaks at initial energies -1.3 and -0.6 eV for quarter-monolayer coverage which disappear at higher coverage. The emission lobes are strongly peaked in the $〈110〉$ azimuths and are attribut…
Phase transitions in triammonium hydrogen disulfate (NH4)3H(SO4)2 were studied by means of dielectric measurements and differential thermal analysis. Below room temperature three phase transitions were observed at −8, −132, and −140°C. The dielectric constant along the c*-direction shows breaks at the −8 and −132°C tr…
The α → β phase transition in quartz and in the isostructural AlPO4 has been studied in situ in an electron microscope. A very high density of defects was observed close to the transition temperature. A diffraction contrast analysis allowed us to identify these defects as dauphiné twins. In the neighbourhood of the tr…
The Raman spectra of ammonium iodide have been measured under hydrostatic pressure up to 6.4 kbar and at temperatures between 130 and 300 K. The strong change of the Raman spectra of NH4I allows the determination of the phase diagram of NH4I. The triple point is found to be at 5.5±0.1 kbar and 170±2 K. The temperature…
The retention of hydrogen isotopes in Mo at room temperature after ion implantation damage has been studied by measurements of H depth profiles and total D retained in the near-surface region. Implantations of He, O, Ne, and Bi in a fluence range 3×1014–2×1017/cm2 were followed by 8-keV hydrogen bombardment to fluence…
A report on fabric and garment flammability which represents a synthesis and overview of research conducted by four independent labs, sponsored jointly by the Government Industry Research Committee on Flammable Fabrics and by the Office of Flammable Fabrics of the National Bureau of Standards. It is intended as a refe…
Measurements of DC and AC conductivity and thermopower show that VO 2 : W can be treated as a conventional n-type extrinsic semiconductor with a donor level 0.06–0.08 eV below the conduction band. For samples with an impurity content from 0.67 → 1.70 at.% W, an effective mass ratio m*/m of 65 ± 10 and a compensation r…
The quantum-mechanical single-configurational-coordinate model is used to interpret Y2O2S:Eu+3 and La2O2S:Eu+3 7F→charge-transfer state (CTS) absorption, 5Di→5Di−1 one-step and 5D→CTS→5D two-step quenchings, and CTS→5Di feeding fractions. The preferred fit requires unequal force constants and a small downshifting of t…
The thermoelectric power of a series of isostructural organic charge-transfer salts has been measured. The compounds consist of a tetracyanoquinodimethane (TCNQ) anion with cations of tetrathiafulvalene, cis/trans-diselenadithiafulvalene, and tetraselenafulvalene. The salts are metallic at high temperatures with a sha…
A general expression is obtained for the magnetoresistance tensor of a solid containing a small number of macroscopic inhomogeneities. The result is used to show that a wide variety of inclusions will generate a linear transverse magnetoresistance in a free-electron metal at high fields. Voids or other nonconducting d…
Measurements of the electrical resistivity as a function of temperature have been made on a series of bcc V-Cr solid solutions over the range 285 to 1200\ifmmode^\circ\else\textdegree\fi{}K (and at 4.2\ifmmode^\circ\else\textdegree\fi{}K). The deviations from a linear temperature dependence of the resistivity at tempe…