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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. 5486-5492 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Starting from the formalism of collisional time-correlation functions, an expression is derived for the double differential cross section (with respect to scattering angles and final rotational energies) of molecules with a thermal distribution of initial rotational states, colliding with fast atoms. This expression is valid when the duration of the collision is short compared with the periods of internal motions of target molecules. The formulation leads to simple distributions in terms of error functions, which can be used to parametrize experimental results. The parameters in turn give the average rotational energy and its standard deviation for the final state. This procedure is followed to interpret recent experimental measurements of the final rotational distributions of CO and CO2 colliding with fast hydrogen atoms obtained from the photolysis of hydrides. For CO(v=1) and CO2(0001), in which the collisions are impulsive, the derived formula fits the experimental distribution very well. For CO(v=0), in which long-duration, complex-forming collisions play an important role, an additional statistical distribution can be introduced to satisfactorily explain the experimental results.
    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 91 (1989), S. 7557-7562 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rate of intramolecular electronic excitation energy transfer in 9,9' bifluorene has been investigated in a variety of solvents, using both time-correlated single photon counting and femtosecond fluorescence upconversion technique. The kinetics of energy transfer were determined in both cases by time dependent fluorescence anisotropy measurements. The energy transfer dynamics between fluorene moieties has been found to occur on a time scale of approximately 600 fs in different solvents and has been correlated with the T2 value calculated from the absorption linewidth and the β value obtained from jet measurements. The dihedral angle between the fluorene moieties was also calculated from the anisotropy measurement and compared with the values obtained from a solution phase NMR determination.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2316-2318 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diffusion of boron implanted into preamorphized silicon has been studied using secondary-ion mass spectroscopy and transmission electron microscopy. A surface preamorphized layer was created by double silicon ion implantation and the as-implanted boron profiles were confined completely within the preamorphized layer. Results show that boron diffusion during rapid thermal annealing (RTA) is anomalous in nature, and that the magnitude of the anomalous diffusion depends upon the RTA temperature. While RTA at 1150 °C shows an enhanced boron diffusion compared to that in single crystalline samples, a reduced diffusion is observed in preamorphized samples annealed at 1000 °C. Results are discussed in terms of the difference in the defect evolution during RTA.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1187-1189 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-quality stoichiometric films of YBa2 Cu3 O7−x have been grown epitaxially on SrTiO3 substrates by sputtering from a stoichiometric target of hemispherical shape using a Hg vapor triode plasma. Films exhibited superconducting transitions of a width ΔT∼2.5 K, with zero resistance being achieved at 89 K. From both the x rays and the temperature dependence of the normal-state electrical resistance it can be inferred that the films contain an admixture of domains with either the c or a axes normal to the plane.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1545-1547 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HgTe-CdTe superlattices and other microstructures such as single and double barrier tunneling structures are commonly grown by molecular beam epitaxy with the mercury flux continuously on the sample during the growth. This means that some mercury will be incorporated in the CdTe layers. We present here, for the first time, a measurement of the amount of mercury incorporated in thin layers of CdTe. X-ray photoelectron spectroscopy was used to measure the amount of mercury. The amount of mercury was found to be between 3 and 9% for CdTe (111)B, depending on the growth conditions. The amount of mercury was found to increase with mercury flux and to decrease as the substrate temperature was increased. Under the same conditions, it was found that much more mercury was incorporated in the (100) orientation. The type of substrate (CdTe or GaAs) was not found to influence the results. These results indicate that the amount of mercury in the CdTe layers of HgTe-CdTe superlattices is not quite as low as expected from measurements of thick CdTe layers, but it can be low enough that it does not influence significantly the results on the superlattice system in the (111) orientation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1865-1867 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a high-efficiency PpinN GaAs/AlGaAs waveguide phase modulator for high-speed operations. By introducing p- and n-GaAs layers beside the intrinsic GaAs layer of a P-i-N double heterostructure, the absorption edge-related effect, hardly used in P-i-N phase modulators, is utilized. We demonstrate a high phase shift efficiency of 37.5°/V mm at 1.3 μm wavelength. Although this corresponds to the highest expeirmental value reported for reverse-biased GaAs/AlGaAs phase modulators, our device operates with a low junction and a very low dynamic capacitance.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low-energy ultrahigh-vacuum compatible ion gun with single-grid optics was used to provide accelerated Sb ion doping during the growth of Si(100) by molecular beam epitaxy (MBE). The incorporation probability of accelerated Sb in MBE Si films grown at 800 °C with an ion acceleration potential of 150 eV was near unity, more than four orders of magnitude higher than for thermal Sb. The films exhibited complete dopant substitutionality and temperature-dependent electron mobilities were equal to the best reported bulk Si values for Sb concentrations up to 2×1019 cm−3, more than an order of magnitude higher than obtainable by thermal Sb doping during Si MBE. Transmission electron microscopy examination of all films showed no evidence of dislocations or other extended defects.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2649-2651 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial zinc blende structure metastable (GaAs)1−x(Si2)x alloys have been grown with 0〈x〈0.3 on As-stabilized GaAs(100) substrates by a hybrid sputter deposition/evaporation technique. The films, typically 2–3 μm thick, were deposited at 570 °C with growth rates between 0.7 and 1 μm h−1. Alloys with 0〈x〈0.12 were defect-free as judged by plan-view and cross-sectional transmission electron microscopy (TEM and XTEM) with x-ray diffraction peak widths approximately the same as that of the substrate, 30 arcsec 2θ. XTEM lattice images showed smooth abrupt interfaces. (GaAs)1−x(Si2)x alloys with x〉0.12 exhibited increasing evidence of interfacial defects associated with lattice strain when grown on GaAs. However, defect-free alloys with x up to 0.3 were obtained using (GaAs)1−x(Si2)x/GaAs strained-layer superlattice buffer layers to provide a better lattice match.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2370-2372 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the critical currents in rf-sputtered YBa2Cu3O7−x thin films deposited on polycrystalline yttria-stabilized zirconia substrates as a function of temperature down to 10 K. The dependence of the granular films at low temperature indicated exponential behavior which is similar to the superconductor-normal metal-superconductor (S-N-S) type tunneling junctions. For the films with a grain size of approximately 1 μm, we observed two exponential decay constants, which suggest that Josephson junctions limiting the transport critical current are possible both at the grain boundaries and at twin boundaries.
    Type of Medium: Electronic Resource
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