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  • Wiley-Blackwell  (54)
  • American Institute of Physics (AIP)  (46)
  • Blackwell Publishing Ltd  (24)
  • 1995-1999  (112)
  • 1975-1979  (12)
  • 1
    Electronic Resource
    Electronic Resource
    A three-dimensional wave-packet method for the CH overtone spectroscopy and intramolecular vibrational relaxation dynamics of the fluoroform molecule (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 445-456 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The overtone spectroscopy and intramolecular vibrational relaxation dynamics of CH chromophore in the fluoroform molecule is studied by a three-dimensional (3D) time-dependent wave-packet method, and the results are compared with the experiment and with those of a 2D (stretch–bend) wave-packet method. A third mode (CF symmetrical stretch) is included in order to explain the long time dynamics and the combination bands between the CF stretch fundamental and the Fermi polyad frequencies. The comparison with the 2D study is carried out by the use of a full set of dynamical and spectroscopic variables, based on the autocorrelation function of the bright states of each polyad. The spectroscopic variables then follow by Fourier transforming the autocorrelation function, while the dynamical ones emerge via survival probability in the frame of the dynamical statistical ensemble. These include several relaxation times and the number of cells and rates of phase–space exploration. The specific effect of the third mode is monitored by following the reduced dynamics of the system irrespective of the polyad stretch–bend dynamics, through population evolution. Dynamical results clearly reveal the third mode effects at very short and long times. In the last regime, we can observe a great span of different behaviors, depending on how the third mode excited states are involved. This richer variety of dynamical patterns cannot be observed in a two-mode model and justifies the present work. The spectroscopic results of both models are in good agreement with the experimental results. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473386
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron irradiation defects in gallium sulfide: Optical absorption measurements (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6651-6656 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gallium sulfide single crystals have been irradiated with different thermal neutron doses. Defects introduced by neutron irradiation turn out to be optically active, giving rise to absorption bands with energies ranging from 1.2 to 3.2 eV. Bands lying in the band-gap exhibit Gaussian shape. Their energies and widths are independent of the irradiation dose, but their intensities are proportional to it. Thermal annealing is completed in two stages, ending at around 500 and 720 K, respectively. Centers responsible for the absorption bands are proposed to be gallium-vacancy-galliuminterstitial complexes in which the distance between the vacancy (acceptor) and the interstitial (donor) determines the energy and intensity of the absorption band, as well as the annealing temperature. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365204
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  • 3
    Electronic Resource
    Electronic Resource
    Per-carrier nonlinear optical response of [111]-oriented piezoelectric InGaAs/GaAs multiple quantum wells (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 417-423 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measure the per-carrier nonlinear responses caused by photoexcited carriers in two strained [111]-oriented InGaAs/GaAs multiple-quantum-well structures, and we compare them to that measured in a [100]-oriented structure. Without an external bias, we find that the absorption coefficient changes per photogenerated carrier for the [111]-oriented piezoelectric materials are smaller than for the [100]-oriented materials, not larger, as originally suggested. Subsequently, measurements of the per-carrier nonlinear responses as a function of reverse bias voltage demonstrate that the smaller per-carrier nonlinearities measured for the [111] structures are partially the result of a broadening of the excitons by the huge in-well fields, but can be primarily attributed to the quality of the [111]-grown materials. When corrected for differing in-well fields and for differing excitonic linewidths, the per-carrier responses are similar in magnitude, suggesting that the [111] response may eventually approach that of [100] material, but probably will not significantly exceed it. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360846
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  • 4
    Electronic Resource
    Electronic Resource
    Polarized absorption of Nd3+ in LiNbO3: Effect of MgO codoping (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5929-5935 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation is presented of the polarized optical absorption of the Nd3+ ion in LiNbO3 and LiNbO3(MgO) crystals. Energy levels of Nd3+ are identified and labeled by appropriate crystal quantum numbers μ=1/2 or μ=3/2, in agreement with C3 local symmetry. The anisotropic Judd–Ofelt theory is applied to estimate spectroscopic parameters relevant for laser applications (radiative lifetimes and branching ratios from the 4F3/2 laser state). Fluorescence lifetimes are also determined to estimate the quantum efficiency from the 4F3/2 state: η=0.6 for LiNbO3:Nd and η=0.5 for LiNbO3(MgO):Nd. The effect of MgO codoping in the energy levels as well as in the spectroscopic parameters of the Nd3+ ion is evaluated and discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359174
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  • 5
    Electronic Resource
    Electronic Resource
    Competing magnetic interactions in manganese perovskites : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5481-5483 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural and magnetotransport properties of L2/3A1/3MnO3 (A=Ca, Sr) oxides reveal the gradual increase of the magnetic frustration when bending the Mn–O–Mn bonds. The relative strength of competing magnetic interactions and thus the ferromagnetic ordering temperature TC are controlled not only by R0 (R0 is the mean radius of the lanthanides) but also by the electronegativity of the divalent cation. Consequently, the curve TC(R0) is not universal but it is sensitive to the alkaline ions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364633
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison between disaccommodation and ferromagnetic resonance measurements in polycrystalline yttrium–iron–garnet samples : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5436-5438 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline yttrium–iron–garnet (YIG) samples were sintered in air at temperatures ranging from 1350 to 1450 °C. Ferromagnetic resonance measurements have been accomplished at 11 GHz from 77 to 350 K. The different contributions to the linewidth have been analyzed. These results are compared with previous measurements of magnetic disaccommodation in the same samples. A qualitative relationship between both kind of measurements for polycrystalline YIG samples by means of an induced anisotropy formalism is provided. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362331
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  • 7
    Electronic Resource
    Electronic Resource
    Erratum: "Exponential critical-state model for magnetization of hard superconductors'' [J. Appl. Phys. 67, 3430 (1990)] (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1017-1017 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365547
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  • 8
    Electronic Resource
    Electronic Resource
    Light scattering in p-type GaAs:Ge (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2388-2395 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present in this work the results of a Raman spectroscopy study on the plasmon–phonon coupling in Ge-doped p-type gallium arsenide. A series of polarized Raman scattering experiments were carried out on epitaxial films grown by liquid-phase epitaxy on (100) GaAs substrates at 20, 100, and 300 K. The films were p type with free hole densities varying in the range of 5×1017–1×1020 cm−3. Under the scattering configurations employed, the longitudinal optical (LO) mode is forbidden for crossed polarization while the transverse optical (TO) mode is forbidden for both parallel and crossed polarizations. However, all the polarized Raman spectra showed two peaks with frequencies close to the TO and LO phonons of semi-insulating GaAs. The appearance of such forbidden modes was accounted for with a theoretical model which considers phonon–plasmon coupled modes with wave vectors much larger than those given by the regular q≈0 wave vector transferred by photons. Ionized acceptor impurities provide such additional wave vector transfer through elastic scattering of the photoexcited electrons and holes. It is demonstrated that the experimental values for position and linewidth of the peaks are well described by the theoretical calculations when Fröhlich-type and deformation potential mechanisms are considered as means of interaction. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363074
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  • 9
    Electronic Resource
    Electronic Resource
    Transport properties of amorphous CoZrNd thin films with very low Nd content (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6545-6545 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The composition and temperature dependence of electrical resistivity were studied for a series of amorphous (Co93Zr7)100−xNdx for x〈3.4 and for a temperature range between 77 and 300 K. The films were deposited by rf sputtering. Measurements of electrical resistivity were performed by the standard four probe technique with ac currents of 10 mA. The rate of heating and cooling was 1 K/min. The electrical resistivity is very sensitive to the presence of Nd ions, as the resistivity clearly increases with a very slight increase of Nd content. The temperature dependence of resistivity does not obey the T2 law predicted by the diffraction model as proposed by Meisel and Cote but follows very nicely the law ρ(T)=aT3/2−bT+c, a result also found for amorphous Gd–Co. The first term corresponds to the electron scattering from the magnetic spin and the second term to the electron scattering from the disordered configuration of atomic potentials. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361941
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  • 10
    Electronic Resource
    Electronic Resource
    The application of the photoacoustic transmittance oscillations for determining elastic constants in gallium and indium selenides (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3200-3204 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmittance periodic oscillations are observed in GaSe and InSe on excitation with optical pulses. Such oscillations are explained in terms of photoacoustic generation of dilatational waves, which become resonant within the crystal. Spectral analysis of those oscillations in samples of different thickness has led to an accurate determination of the longitudinal acoustic-wave velocity along the crystallographic axis c. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361219
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