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  • 1985-1989  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2274-2282 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We compare the sensitivities to initial conditions for both direct (regular) and long-lived (chaotic) trajectories in classical scattering calculations with the corresponding properties of trajectories of position and momentum expectation values for quantum wave packets. The collinear H+H2 reaction is used as an example. The results show that the high sensitivity seen in chaotic trajectories is not reflected in the quantum dynamics. We conclude that it is possible for a classical ensemble consisting of only regular trajectories to respond trajectory by trajectory to perturbations in much the same way as a quantum wave packet. (There will of course be cases that are exceptions to this rule.) The response of an ensemble consisting of chaotic trajectories may on the average be similar to that of a wave packet, but not at the level of individual trajectories. In addition, the sensitivities of these trajectories to variations in the potential are analyzed. We conclude that the large contributions to the sensitivities from particular long-lived trajectories must approximately cancel when an exact ensemble average is taken. An algorithm is presented to smoothly account for the contributions to the sensitivities from these trajectories.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2263-2273 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The corresponding effects of features in the potential on classical, semiclassical, and quantum mechanics are probed using the technique of functional sensitivity analysis. It is shown that the classical and quantum functional sensitivities are equivalent in the classical (small (h-dash-bar)) and harmonic limits. Classical and quantum mechanics are known to react in qualitatively similar ways provided that features on the potential are smooth on the length scale of oscillations in the quantum wave function. By using functional sensitivity analysis, we are able to show in detail how the classical and quantum dynamics differ in the way that they sense the potential. Two examples are given, the first of which is the harmonic oscillator. This problem is well understood by other means but is useful to examine because it illustrates the detailed information about the interaction of the potential and the dynamics which can be provided by functional sensitivity analysis, simplifying the analysis of more complex systems. The second example is the collinear H+H2 reaction. In that case there are a number of detailed and striking differences between the ways that classical and quantum mechanics react to features on the potential. For features which are broad compared to oscillations in the wave function, the two react in qualitatively the same way. The sensitivities are oscillatory, however, and there are phasing differences between the classical and quantum sensitivity functions. This means that using classical mechanics plus experimental data in an inversion scheme intended to find the "true'' potential will necessarily introduce sizeable errors.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2435-2437 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We first report on migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layer on Si substrates (GaAs/Si). Excellent surface morphology GaAs layers were successfully grown on (100)Si substrates misoriented 4° toward the [110] direction. The MEMBE growth method is described, and material properties are compared with those of normal two-step MBE-grown or in situ annealed layers. Micrographs of cross-section view transmission electron microscopy (TEM) and scanning surface electron microscopy (SEM) of MEMBE-grown GaAs/Si showed dislocation densities of 1×107 cm−2, over ten times lower than those of normal two-step MBE-grown or in situ annealed layers. AlGaAs/GaAs double heterostructures have been successfully grown on MEMBE GaAs/Si by both metalorganic chemical vapor deposition and liquid phase epitaxy.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 53 (1988), S. 5379-5381 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3671-3671 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of a new heat treatment technique and a conventional annealing process on the high-frequency core losses (20 kHz) of Fe76Mo3(SiB)21 amorphous alloys have been investigated. The result shows that the remanence and the high-frequency losses can be reduced remarkably by this special treatment. Meanwhile, its coercivity remains lower in the range of 2.39–4.79 (A/m). In studying, it is found that under the condition of this special treatment the phenomena of the enrichment and the depletion of atoms (Fe, Si, B) become more heavier, and the state between the surface layers of metallic glass core is changed, and the degree of partial crystallization of α-Fe can be controlled. The magnetic properties of Fe76Mo3(SiB)21 metallic glasses obtained by the treatment under the technological parameters selected properly are satisfied, as follows: Fe76Mo3(SiB)21—I P2/20 K =5.27 w/kg, P5/20 K =32.61 w/kg, B1=1.043 T, Hc1 =2.88 A/m, Br1/B1 =0.18. Fe76Mo3(SiB)21—I P2/20 K =5.59 w/kg, P5/20 K =37.25 w/kg, B1=0.656 T, Hc1 =4.79 A/m, Br1/B1 =0.11, in which the properties of high-frequency losses are superior to those of the conventional annealed alloys (P2/20 K =12–14 w/kg), and are comparable to those of VITROVAC Co66Fe4(MoSiB)30 and others.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Al0.3Ga0.7As/Al0.05Ga0.95As double-heterostructure light-emitting diodes (LED's) were successfully grown for the first time by liquid phase epitaxy on a GaAs-coated Si substrate that was prepared by a sequential process of migration-enhanced epitaxy and molecular beam epitaxy. The edge-emitting LED's had diode ideality factors of 1.54 at a forward-biased voltage higher than 0.9 V and external quantum efficiencies of 3.3×10−3 W/A per facet. This efficiency is 50 times higher than the previously reported value, and is on the same order as that of AlGaAs homojunction LED's fabricated on the GaAs substrates by liquid phase epitaxy.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 42 (1988), S. 893-896 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied some anomalous hemoglobins by Mössbauer spectroscopy. We found that there is a correspondence between the physical conditions of the respective patients and the additional components of the Mössbauer spectra found for their hemoglobins.
    Type of Medium: Electronic Resource
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