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  • Elsevier  (31)
  • Wiley-Blackwell  (14)
  • American Institute of Physics (AIP)  (6)
  • Oxford University Press  (4)
  • American Chemical Society (ACS)
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  • 1988  (55)
  • 1
    Publication Date: 1988-02-01
    Print ISSN: 0167-2738
    Electronic ISSN: 1872-7689
    Topics: Physics
    Published by Elsevier
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  • 2
    Publication Date: 1988-01-01
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3057-3062 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A nonperturbative theory of predissociation based upon an effective Hamiltonian is presented. For a model diatomic system in which a (bound-state) Morse potential-energy curve is crossed by an (unbound-state) exponential potential-energy curve, the exact effective Hamiltonian may be obtained in high precision for any well behaved interaction potential. The real and imaginary parts of the eigenvalues of the effective Hamiltonian give the (shifted) energies and widths, respectively, of the predissociative states. Numerical results are obtained and compared with both a semiclassical approximation and those derived from solutions of coupled Schrödinger equations. In the weak-coupling regime the agreement between the present method and semiclassical results is good, and better in general than the coupled-equations results, which apparently suffer from instability problems. For couplings of intermediate strength, the semiclassical method breaks down, as do fully quantum-mechanical first-order perturbation approximations, as is demonstrated by comparison with the converged nonperturbative results. Fixed points of the spectrum appear at "resonance'' values of the coupling strength which bring the exact energy eigenvalue into resonance with one of the adiabatic levels so that the imaginary part (level width) of the former vanishes. Thus beyond a critical coupling strength, stronger coupling enhances the stability of a resonance.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5984-5985 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nature of the metastable state of hydrogen trimers described by Ga and Kuppermann (ref.1) is further discussed. The analysis is based on linewidth measurements in the emission spectrum of the trimer, the quantum mechanical selection rules, and earlier beam and photoionization measurements.(AIP)
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4949-4956 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nuclear displacement operator (NDO) for Born–Oppenheimer electronic wave functions (BOEWF) is introduced and some recurrence formulas are obtained. The formulas for Born couplings and higher derivatives of BOEWF with respect to nuclear coordinates are derived from very general considerations and relations among these quantities are given. The series form, exponential, and integral forms of the NDO are exhibited. Particularly, it is proven that for the two-state systems the NDO has a very simple form by which it is convenient to study two-state dynamical processes. It is shown that the NDO satisfies a differential equation which is analogous to that for the time-evolution operator in the presence of a time-dependent perturbation. The physical meanings of these two operators are compared. It is demonstrated that the NDO is uniquely determined by the vector Born coupling matrix, and that the nuclear motion may be analyzed in terms of a local non-Abelian gauge transformation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4133-4135 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An unusually pure Mnx Fe3−x O4 sample (x(approximately-equal-to)1.3) from a regionally metamorphosed ore body is expected to exhibit an approach to thermodynamic equilibrium unattainable in synthetic materials. This expectation is confirmed by the observation of (1) a small tetragonal distortion and (2) a complete ordering of Fe on the B sublattice. 57Fe Mössbauer spectra, obtained at 298, 175, 125, and 92 K and in an external field of 30 kG at 92 K, exhibit magnetic hyperfine splitting requiring the fitting of two subspectra, I and II. At 298 K, Heff =418 kOe, α=0.36 mm s−1 , and ε≈0 for the more intense subspectrum I, whereas for II Heff =403 kOe, δ=0.34 mm s−1 , and ε(approximately-equal-to)−0.15 mm s−1 . The two subspectra are not split by a 30 kG external field. Subspectra I and II correspond to Fe3+ ions located on a single magnetic sublattice. Subspectrum II is assigned to Fe3+ ions in regions with locally, large tetragonal distortions as a consequence of Mn3+clustering, which has often been invoked to explain the crystal chemistry and physical properties of Mnx Fe3−x O4 .
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 45-48 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and construction of an imaging bandpass electron energy analyzer which operates in the intermediate magnetic field of a photoelectron spectromicroscope is described. Image electrons injected parallel to the magnetic field are guided, using crossed magnetic and nonuniform electrostatic fields, to a low-pass electron mirror and subsequently a high-pass retardation filter. The nonuniform electrostatic fields compensate for the energy-dependent dispersion of the crossed fields. A bandwidth-limited photoelectron image demonstrates the spatial integrity of the image after passage through the image bandpass filter. The performance of the device as an energy analyzer is assessed. An energy resolution of less than 30 meV is demonstrated and thermionic electron spectra are presented with electron energies ranging from 10 to 200 eV with a 250-meV bandwidth. Area-selected photoelectron spectra from Au and W show UPS and XPS performance of the device. In the case of Au, the spectrum was obtained from a 400-×400-nm area.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 7662-7670 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Formulation of the expectations of eight operators required for the evaluation of the Born corrections, the Born couplings, and higher derivatives of the Born–Oppenheimer wave functions are derived for the case of a Gaussian-lobe orbital (GLO) basis. The relative simplicity of these analytical formulas is a special advantage of GLO and reduces the computer time in these calculations. Some operators treated here require a modification of the Slater rules. As examples of applications of these techniques, ab initio calculations of the orbital stresses and the Born corrections for the ground state X 1Σ+g and excited states 1Σ+g(II), C, C' 3Πu, and 3Πu(II) of N2 are reported. The obtained results show that the Born correction near the avoided crossing region strongly depends upon the nuclear separation; in this region configuration interaction makes an important contribution.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 35 (1988), S. 1945-1953 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A polytheylene composite was prepared and tested. It was consisted of a high-density polyethylene (HDPE) matrix and uniaxial gel-spun high-modulus PE fiber. Aided by the similarity between matrix and fiber, transcrystallization of HDPE melt on the PE fiber surface was generated. Nucleating agents were not employed. The transcrystalline growth of HDPE on the PE fiber surface was found to consist of an inner and an outer zone. The inner zone, 2-3 μm thick, is composed of HDPE crystals nucleated on the PE fiber surface. Photomicrographs showed a well-defined region of row-nucleated HDPE on the surface of PE fiber. This means the fibrils of HDPE were found to grow out from the PE fiber axis and HDPE crystallites are oriented in planes perpendicular to the PE fiber axis. The fiber in the composite induced the transcrystalline growth of HDPE on the PE fiber surface at higher temperature than on cooling the melt. For 36 wt% fiber, the increase was 2.5°C, also resulting in ∼ 10% more crystals. Crystallization of a composite with 50 wt% fiber at 124°C involved two steps: The first a fast transcrystallization of HDPE on the PE fiber surface followed by the bulk crystallization of the HDPE.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 615-621 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collisionally activated decomposition of [M + H]+ ions, generated by fast atom bombardment (FAB) of glutathione conjugates, has been studied by tandem mass spectrometry (MS/MS) using hybrid sector/quadrupole instruments. Abundant fragments of diagnostic utility were present in the daughter ion spectra. Common fragmentation modes were observed but their relative importance was strongly dependent on the nature of the conjugated species. As an example of a general approach to the characterization of glutathione conjugates in biological samples, the acetaminophen-glutathione conjugate was identified in rat bile, following coadministration of (2H0)- and (2H3)acetaminophen, using the experimental sequence: (i) conventional FAB mass spectrometric analysis, (ii) MS/MS using constant neutral loss (129 u) scanning to identify parent ions corresponding to glutathione conjugates, (iii) MS/MS to yield daughter ion spectra of parents so identified and corresponding to (2H0)- and (2H3)-labeled conjugates.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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