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  • 1
    Electronic Resource
    Electronic Resource
    Study of high-field electron transport in semiconductors using balance equations for nonparabolic multivalley systems (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1504-1509 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Balance equations for high-field electron transport in nonparabolic multiband (multivalley) semiconductors are proposed based on the Heisenberg equations of motion for the total physical momentum, the total energy and the population of carriers in each energy band (each valley), and the statistical average with respect to an initial density matrix having a lattice wave-vector shift, an electron temperature, and a chemical potential for each energy band (each valley) as parameters. As an example, these equations are applied to the discussion of hot-electron transport in bulk Si, assuming Kane-type energy dispersion for six elliptical valleys. The theoretical results are in good agreement with experiments and with Monte Carlo simulations, over the entire range of the electric field up to 140 kV/cm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363024
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  • 2
    Electronic Resource
    Electronic Resource
    Adiabatic path integral molecular dynamics methods. II. Algorithms (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 2028-2035 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Efficient numerical algorithms are developed for use with two finite temperature semiclassical approximations to quantum dynamics both of which require trajectories generated on potentials of mean force derived from the path integral expression for the density matrix. The numerical algorithms are formed from the combination of a classical adiabatic relation similar to that used in the Car–Parrinello method and an efficient path integral molecular dynamics scheme. Results on model, an anharmonic oscillator and a realistic, fluid para-hydrogen, problem indicate that semiclassical dynamics can be obtained for virtually the same computational cost as structure and thermodynamics. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470959
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  • 3
    Electronic Resource
    Electronic Resource
    Simulation of negative-effective-mass terahertz oscillators (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2867-2873 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a model calculation of hole current oscillations in doped p+pp+ ballistic diodes using the nonparabolic balance-equation theory and a time-dependent drift-diffusion model. Such an oscillation originates from a negative effective mass (NEM) region in the hole dispersion relation. In the present balance-equation calculation, we consider the scatterings by hole-impurity, hole-acoustic phonon, hole-polar-phonon, and hole-nonpolar-phonon–hole interactions, and yield a "N-shape" velocity-field relation, which are quite different from the two-valley results for electrons in bulk GaAs. We provide a detailed analysis of the resulting oscillations as a function of the applied voltage, base length, base doping, and the dispersion relation. Typical frequencies for a 0.2 μm structure NEM oscillator are in the terahertz range. Qualitative agreement is obtained between the present calculations and the existing Boltzmann results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372270
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  • 4
    Electronic Resource
    Electronic Resource
    A picosecond electron gun for surface analysis (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1000-1009 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Theoretical and experimental investigations for a new design of an ultrashort pulsed laser activated electron gun for time resolved surface analysis are described. In addition, a novel electron detection and image analysis system, as it applies specifically to time resolved reflection high-energy electron diffraction in the multiple-shot operation, are reviewed. Special attention is directed to minimize the photoelectron transit-time spread from the electron gun, in spite of an unusually long focal length and a small convergence angle of the pulsed electron beam. Both requirements are necessary to use the electron gun for diffraction techniques. The design value for the temporal resolution in the synchroscan operation is 1.3 ps. Based on a thorough theoretical investigation, a new electron gun has been designed, constructed, and tested. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146036
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  • 5
    Electronic Resource
    Electronic Resource
    Whistler turbulence at the magnetopause: A nonlinear generation mechanism (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 272-276 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma maser effect in the existence of enhanced kinetic Alfvén wave turbulence is investigated as the generation mechanism of the whistler turbulence at the magnetopause. The numerical results of the growth rate show that on the scale of neither the ion inertial length nor the electron inertial length, the whistler waves can be excited, and the peak of the maximum growth rate occurs on the scale of the effective ion Larmor radius. The kinetic Alfvén wave dynamics associated with the scale length of the effective ion Larmor radius is intrinsically important in the magnetic reconnection and leads to the generation of whistler turbulence. The theoretical model of the generation of whistler turbulence is useful for explaining the observations of intense electromagnetic fluctuations at the magnetopause. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326063
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  • 6
    Electronic Resource
    Electronic Resource
    A Born–Oppenheimer approximation for path integrals with an application to electron solvation in polarizable fluids (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 2902-2916 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Born–Oppenheimer approximation is introduced into the path integral expression for the canonical partition function. It is difficult to apply this to simulations. We devise a new adiabatic expression which we call the free energy Born–Oppenheimer approximation which is much easier to simulate. It is shown that this approximation deviates from the exact path-integral expression by no more than does the standard Born–Oppenheimer approximation and we apply it to the problem of an excess electron dissolved in a polarizable fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465198
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  • 7
    Electronic Resource
    Electronic Resource
    Phase angle diffusion of newborn ions in the self-consistently generated fields in solar wind plasmas (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 696-700 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase angle diffusion, pitch angle diffusion, and energy diffusion of newborn ions in the self-consistently generated fields in solar wind plasmas are studied by means of a one-dimensional electromagnetic hybrid code. For newborn ions, the time for phase angle diffusing to 2π is a little shorter than the time for pitch angle scattering to a relatively thin complete shell, and it is much shorter than the energy scattering time for broadening of the shell toward a thermal distribution. The speed of phase angle diffusion increases monotonously with the injection velocity, but it does not change in the same way with the injection rate. The phase angle diffusion of heavier injected ions is slower than that of lighter injected ions. The complete pickup process of newborn ions should consist of four stages: (1) the creation of the newborn ions and macroperpendicular pickup due to the motional electric field; (2) phase angle diffusion; (3) pitch angle diffusion; and (4) energy diffusion. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873854
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  • 8
    Electronic Resource
    Electronic Resource
    A new quantum propagator for hard sphere and cavity systems (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 2382-2385 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new short time propagator for a particle interacting with a hard sphere or with a hard sphere cavity is derived. This new propagator is shown to be a much better approximation than the image approximations used in the literature and should prove useful for path integral or Green function Monte Carlo simulations. The simple example of the radial distribution function of a hard sphere gas is calculated using the new propagator as well as the older image approximation propagator and is shown to converge much more rapidly to the ab initio result.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463076
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  • 9
    Electronic Resource
    Electronic Resource
    Many-body dispersion forces of polarizable clusters and liquids (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8628-8636 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A system of atoms with embedded Drude dispersion oscillators interacting through dipole–dipole forces is simulated. Using path integrals it is shown that after the coordinates of the dispersion oscillators are integrated out, the atoms interact through many-body dispersion forces to all orders of the dipole–dipole interaction. Simulations are carried out on clusters to see if the presence of many-body forces leads to ground state geometries different from those predicted from two-body potentials. In addition, the polarizability tensor of clusters is determined as a function of cluster size. Simulations are also carried out for fluids to see how many-body forces affect the pair correlation function. Lastly, the long-range interaction between van der Waals clusters is compared with the predictions of a summation over site–site two-body interactions. It is found that many-body forces have only a minor effect on the low energy geometries of van der Waals clusters, a somewhat surprising result given that many-body forces do give an important contribution to surface free energies of clusters and liquids. The vibrational frequencies of the breathing mode decrease by approximately 10%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463381
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  • 10
    Electronic Resource
    Electronic Resource
    Multilayer mirrors for use as a wavelength-selective filter around 100 eV : INTERNATIONAL CONFERENCE ON SYNCHROTRON RADIATION INSTRUMENTATION (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2010-2013 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Multilayer mirrors have been designed, fabricated and tested for use as a wavelength-selective filter of ∼100 eV for photo-CVD experiments at the beamline 12C of Photon Factory, KEK. Mo/Si and Rh/Si multilayers were selected in accordance with new simple optical criteria and fabricated on super-polished CVD-SiC substrates by means of ion-beam sputtering. Both mirrors showed a reflectance of over 40% at around the designed angle of incidence of 45°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140862
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