Trace element analysis of mineral grains by micro-PIXE demands prior knowledge of major element concentrations from which the appropriate matrix corrections are derived. We describe the micro-PIXE determination of maj...
Trace element analysis of mineral grains by micro-PIXE demands prior knowledge of major element concentrations from which the appropriate matrix corrections are derived. We describe the micro-PIXE determination of major elements using 750 keV protons. The major element concentrations measured for a variety of minerals are in good agreement with recommended values.
The infrared spectrum of the endohedral metallofullerene Li+ @ C60 is calculated. Vibrational and rotational motion of the charged inclusion leads to the emission and absorption of radiation. Our calculations assume t...
The infrared spectrum of the endohedral metallofullerene Li+ @ C60 is calculated. Vibrational and rotational motion of the charged inclusion leads to the emission and absorption of radiation. Our calculations assume this motion is governed by the intramolecular ''reflected Morse'' potential of Dunlap, Ballester and Schmidt. The predicted pure rotation band peaks near 40 cm-1. The fundamental vibration-rotation band at 350 cm-1 exhibits unusual band-head structure. Both bands are intense. The first overtone band at 700 cm-1 is also studied. Rotational structure is well resolved in all three bands;at room temperature, hot bands contribute significantly.
The inelastic depolarized light-scattering spectrum of the endohedral metallofullerene Li+ @ C60 is calculated for frequency shifts up to 1000 cm-1. In this species the motion of the charged inclusion within the bucky...
The inelastic depolarized light-scattering spectrum of the endohedral metallofullerene Li+ @ C60 is calculated for frequency shifts up to 1000 cm-1. In this species the motion of the charged inclusion within the buckyball cage generates an induced anisotropic polarizability through an interesting mechanism involving the hyperpolarizability B. The resulting Raman spectrum is quite intense. At room temperature, hot bands contribute significantly to the scattering.
We compute the far-infrared absorption spectrum of the endohedral metallofullerene K+ @ C60. This arises from the vibrational and rotational motion of the potassium ion about its equilibrium position at the center of ...
We compute the far-infrared absorption spectrum of the endohedral metallofullerene K+ @ C60. This arises from the vibrational and rotational motion of the potassium ion about its equilibrium position at the center of the buckyball cage. The spectrum is quite unusual. Although the permanent dipole moment of the complex is zero, absorption is very intense. The spectrum contains a pure rotation band, which peaks near 55 cm-1 at 25-degrees-C. There is also a fundamental vibration-rotation band, consisting of a strong P-branch at 70 cm-1, overlapping the rotational band, and a much weaker R-branch at 180 cm-1. Line-spacing is strongly dependent on the rotational quantum number. Hot bands contribute significantly to the intensity. We include a discussion of dipolar shielding effects.
Two-dimensional, partially flexible polymers interacting with each other through the Onsager-like excluded-volume interaction are shown to exhibit a second-order, isotropic-nematic transition at a sufficiently high de...
Two-dimensional, partially flexible polymers interacting with each other through the Onsager-like excluded-volume interaction are shown to exhibit a second-order, isotropic-nematic transition at a sufficiently high density. The instability of the free energy under the influence of a nematic state is investigated and the critical density at which the isotropic-nematic phase transition takes place is determined analytically. It is shown that both second- and fourth-rank order parameters must be included in order to deduce a Landau expansion of the free energy.
A numerical solution is obtained for the generalized Onsager problem for the isotropic-nematic interface of rigid rods, which accounts for the biaxial effect that was ignored in previous calculations. It is found that...
A numerical solution is obtained for the generalized Onsager problem for the isotropic-nematic interface of rigid rods, which accounts for the biaxial effect that was ignored in previous calculations. It is found that the biaxial effect on interfacial tension is indeed weak, as previously expected. The biaxiality becomes significant only near the isotropic side of the interface.
Fermion mean-field solutions for the Heisenberg and the t-J models have been obtained by considering particle-hole correlations and carrying out the mean-field-theory calculations in momentum space. At half-filling th...
Fermion mean-field solutions for the Heisenberg and the t-J models have been obtained by considering particle-hole correlations and carrying out the mean-field-theory calculations in momentum space. At half-filling the solutions have mixed (s±d)-wave-like symmetry and have a lower ground-state energy than the s (uniform phase) and the d phases. On doping, the solutions with mixed s and d symmetry still have lower ground-state energy than the uniform phase. In the presence of doping, the density of states at the Fermi level in the mixed phases is depressed from its value in the uniform phase and is in good agreement with the experimental data.
Scanning micro-PIXE is employed in conjunction with backscatter electron imaging and cathodoluminescence to study oscillatory zoning of minor and trace elements in natural and synthetic minerals. The scanning proton m...
Scanning micro-PIXE is employed in conjunction with backscatter electron imaging and cathodoluminescence to study oscillatory zoning of minor and trace elements in natural and synthetic minerals. The scanning proton microprobe (SPM) is also used to study surface features on individual mineral grains.
Angular correlations between Kα1 x rays and subsequent L3 x-ray transitions were measured using a Pa233 radionuclide source and high-resolution x-ray detectors. The results provide separately the values of A22(Kα1−L...
Angular correlations between Kα1 x rays and subsequent L3 x-ray transitions were measured using a Pa233 radionuclide source and high-resolution x-ray detectors. The results provide separately the values of A22(Kα1−Lα1) and A22(Kα1−Lα2) as opposed to the compound quantity A22(Kα1−Lα). For the Ll and Lα2 transitions, the A22 values agreed closely with those based upon theoretical (Hartree-Fock) E1 and M2 transition rates. For the less intense Lβ6 and Lβ2,15 transitions, agreement was also observed, although within larger uncertainties. In contrast, the value of A22(Kα1−Lα1) was 0.085±0.007, which is somewhat larger than the predicted value of 0.073. Possible causes for this discrepancy are explored.
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