Accurate measurements of the x-ray intensity ratio I(Kβ)/I(Kα) from electron-capture radionuclides, using Si(Li) detectors of calibrated line shape, eliminate an existing large discrepancy between experiment and rel...
Accurate measurements of the x-ray intensity ratio I(Kβ)/I(Kα) from electron-capture radionuclides, using Si(Li) detectors of calibrated line shape, eliminate an existing large discrepancy between experiment and relativistic Hartree-Fock predictions. Small systematic discrepancies in the literature ratios for the mechanisms of photoionization, and electron and proton excitation, are attributed to omission of radiative Auger (RA) satellites in spectrum analysis. With the inclusion of RA peaks in the spectrum fitting, the present data support Scofield’s predictions of I(Kβ)/I(Kα) at the 1% accuracy level, an important conclusion for elemental analysis techniques such as proton-induced x-ray emission and x-ray fluorescence. The resulting radiative Auger intensities also agree quite well with calculations.
Spectra in the wavelength range of 300–600 nm have been acquired during proton‐beam irradiation of samples of solid hydrogen and deuterium at 4.2 K. Emission spectra from the transitions A′?3Δ u →X? 3Σ? g of O...
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Spectra in the wavelength range of 300–600 nm have been acquired during proton‐beam irradiation of samples of solid hydrogen and deuterium at 4.2 K. Emission spectra from the transitions A′?3Δ u →X? 3Σ? g of O2, 4S–2 D of N?i, and 1 D–1 S of O?i have been measured and attributed to an air impurity in the sample. Comparison is made of the vibrational constants derived from the molecular bands, the spectral shifts of all features, and the lifetime of the 2p 32 D multiplet of N?i obtained in the solid hydrogens with those obtained by matrix isolation studies using N2 and rare gas hosts.
Brillouin frequency shifts from light scattering are used to measure the variation with pressure of the zero‐frequency glass transition temperature T g in atactic polystyrene (PS) at pressures up to 3 kbar. These r...
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Brillouin frequency shifts from light scattering are used to measure the variation with pressure of the zero‐frequency glass transition temperature T g in atactic polystyrene (PS) at pressures up to 3 kbar. These results are extrapolated to high pressures and compared with theoretical predictions. Experimentally it is found that T g asymptotically approaches a critical value at high pressures. The equilibrium lattice model of DiMarzio, Gibbs, Fleming, and Sanchez which approximates the residual entropy of a polymeric glass correctly predicts the experimentally observed trends. The molecular theory of Bengtzelius, G?tze, and Sj?lander is also qualitatively correct at high pressures even though it deals with the glass transition of a classical monatomic fluid. Neither theory is quantitatively in agreement with our results.
作者：
M. SteslickaM. RadnyS. G. DavisonQuantum Theory Group
Department of Applied Mathematics and Department of Physics University of Waterloo Waterloo Ontario Canada N2L?1 and Guelph-Waterloo Program for Graduate Work in Physics University of Guelph Guelph Ontario Canada N1G?1
The effective-range approximation is adopted to study surface states of a linear array of scattering centers. It is shown that, depending on the values of the scattering length and effective range for the surface atom...
The effective-range approximation is adopted to study surface states of a linear array of scattering centers. It is shown that, depending on the values of the scattering length and effective range for the surface atom, two, one, or zero surface states can exist in the forbidden energy gap. The possibility of a smooth transition from true (stationary) surface states to virtual (decaying) states is discussed. A comparison is also made with the crystal-potential approach.
The role of pseudosymmetry for the spontaneous strain in tris-sarcosine calcium chloride (TSCC) crystals has been investigated through Mn++EPR spectra as a function of temperature and externally applied uniaxial stres...
The role of pseudosymmetry for the spontaneous strain in tris-sarcosine calcium chloride (TSCC) crystals has been investigated through Mn++EPR spectra as a function of temperature and externally applied uniaxial stress. The on-axis fine-structure splittings are a sensitive measure of the pseudosymmetry, and the spontaneous strain in improper ferroelastic TSCC crystals can be attributed to the anisotropic expansion or compression of the lattice. Although macroscopically insignificant, the off-axis splittings yielded evidence for a collective molecular mechanism to become significant toward higher temperatures. An anomaly was observed atTo≃ 10°C, indicating the lock-in transition of the modulated structure above this temperature. However, the lattice remained as paraelectric and ferroelastic throughout from the ferroelectric transition up to the decomposition temperature.
作者：
DAMASKINOS, SDIXON, AEUniv of Waterloo
Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can Univ of Waterloo Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can
A scanning laser microscope was used to study the electronic and recombination properties at grain boundaries of bothn- andp-type Wacker polycrystalline silicon in a spatially resolved photoconductivity experiment. Th...
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A scanning laser microscope was used to study the electronic and recombination properties at grain boundaries of bothn- andp-type Wacker polycrystalline silicon in a spatially resolved photoconductivity experiment. The light energy falling on the samples was varied over five orders of magnitude from 10−1to 10−6 mW. Forp-type material the measuredLdecreased with beam intensity from 150 to 60 μm, reaching a constant value at very low beam intensities. The small focal spot of the microscope allowed the measurements to be extended to includen-type samples. Forthese samplesLwas found to change from 90 to 18 μm with decreasing beam intensity. The surface recombination velocitySGBwas evaluated for both samples. Forp-type samples it decreased from 25 000 to 6000 cm/s and forn-type samples from 21 000 to 3000 cm/s with decreasing beam intensity. The quasi-Fermi level separation was determined as a function of the excess minority-carrier-concentration density at the grain boundary and found to increase linearly with beam intensity.
Thin films of a-Si:C have been prepared by thermal evaporation from resistive- and rf-induction-heated carbon crucibles. Samples were prepared with and without electron-beam irradiation of the substrate during deposit...
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Thin films of a-Si:C have been prepared by thermal evaporation from resistive- and rf-induction-heated carbon crucibles. Samples were prepared with and without electron-beam irradiation of the substrate during deposition, and the resulting film properties (electrical and optical) were measured. Reference samples prepared with substrate temperatures from 150 to 250 °C and annealing temperatures from 200 to 250 °C had very similar film properties. The use of vitreous carbon instead of compressed carbon for the crucibles reduced the carbon content by about 30% and the oxygen content of the films by more than a factor of four. Electron-beam irradiation of the purer films produced a tenfold decrease in the conductivity at room temperature and an increase of the high-temperature activation energies compared with the reference samples.
A simple force constant model is developed and applied to the vibrations of the chorine, bromine, and iodine crystals. Fundamental frequencies are calculated and compared to those observed by infrared absorption, Rama...
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A simple force constant model is developed and applied to the vibrations of the chorine, bromine, and iodine crystals. Fundamental frequencies are calculated and compared to those observed by infrared absorption, Raman scattering, and inelastic neutron scattering. The dependence of the halogen–halogen force constants on atomic separation is investigated. Ein einfaches Kraftkonstantenmodell wird entwickelt und auf die Schwingungen der Chlor-, Brom- und Jodkristalle angewendet. Die Fundamentalfrequenzen werden berechnet und mit denen verglichen, die mittels Infrarotabsorption, Ramanstreuung und inelastischer Neutronenstreuung beobachtet werden. Die Abhängigkeit der Halogen–Halogen-Kraftkonstanten vom Atomabstand wird untersucht.
作者：
VONSACKEN, UBRODIE, DEUniv of Waterloo
Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can Univ of Waterloo Guelph-Waterloo Program for Graduate Work in Physics Waterloo Ont Can
Vacuum-deposited Zn3P2films, prepared with and without low-energy electron bombardment during the deposition process, have been characterized both structurally and electronically. Zinc phosphide was chosen for this st...
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Vacuum-deposited Zn3P2films, prepared with and without low-energy electron bombardment during the deposition process, have been characterized both structurally and electronically. Zinc phosphide was chosen for this study because it is a promising material for the absorbing layer in a low-cost thin-film solar cell. The structure of the films has been studied using glancing-angle X-ray diffraction and transmission electron microscopy. Electron bombardment can be used to modify the properties of zinc-phosphide films. The e-beam parameters used in this study increased the degree of preferred orientation and altered the nature of the glass–Zn3P2interface.
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