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  • 1
    Electronic Resource
    Electronic Resource
    Nonequilibrium kinetics of the reaction H+Br2 in xenon within a Lorentz gas model (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2425-2430 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction H+Br2→products in the carrier gas xenon is studied in the framework of the Lorentz gas model. The nonequilibrium velocity distribution function fH of the light component H is calculated from the Lorentz–Fokker–Planck equation. This permits the determination of the nonequilibrium temperature TH and the nonequilibrium rate coefficient k of this reaction. These kinetic quantities are numerically calculated and compared with various other approaches for solutions of the appropriate Boltzmann equation (Kostin method, Chapman–Enskog and Shizgal perturbation method, Keizer approximation).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459699
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  • 2
    Electronic Resource
    Electronic Resource
    Nonequilibrium contributions to the rate of chemical reaction in the Lorentz gas: A comparison of perturbation and numerical solutions of the Boltzmann equation (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 197-203 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The corrections to the equilibrium rate of the chemical reaction A+B→products are analyzed for the Lorentz gas composed of light particles A reacting with heavy particles B in the presence of heavy particles of a carrier gas C. Particles B and C are treated as a heat bath. The reaction is analyzed under conditions in which the products can be neglected. The model of reacting hard spheres (line-of-centers model) introduced by Present is used. Analysis is performed in two ways: (1) By obtaining analytical expressions following from the Chapman–Enskog perturbation solution of the Boltzmann equation generalized for gases reacting chemically. (2) By obtaining numerical results which follow from a numerical solution of a partial differential equation which can be derived from the Boltzmann equation for the reactive Lorentz gas. It is shown that for a specified region of system parameters both types of solution of the Boltzmann equation coincide. The comparison of both methods permits us to find out under which conditions the perturbation method of solution may be used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455504
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic losses in stripline/microstrip circulators : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5739-5741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have included losses in the analysis of a 3N-port stripline/microstrip circulator and have reformulated the circulation conditions previously postulated for the lossless case. Our calculations have been compared to three published data on circulator designs biased below and above ferrimagnetic resonance. Scattering parameters at each port have been calculated as a function of assumed material losses and coupling capacitance of a multiport circulator. Wide transmission band or wide stop bands may be possible for a six port circulator biased above ferrimagnetic resonance. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361848
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  • 4
    Electronic Resource
    Electronic Resource
    Deposition and analysis of silicon clusters generated by laser-induced gas phase reaction (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5302-5306 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon clusters have been generated by CO2-laser-induced decomposition of SiH4 in a flow reactor. By introducing a conical nozzle into the reaction zone, they are extracted into a molecular beam apparatus and analyzed with a time-of-flight mass spectrometer. The mass spectra show that the cluster source emits, besides small clusters, also nanosized species containing around 103 atoms. These clusters were deposited on silicon and sapphire targets at room temperature. The deposited films have been analyzed with a Raman spectrometer and with a field emission scanning electron microscope (FE-SEM). The Raman spectra reveal a broad amorphouslike band and a relatively sharp peak at 518.1 cm−1. Interpretation of the sharp Raman feature, based on the phonon confinement model, suggests the presence of silicon nanocrystallites in the deposited films with a particle size of about 3–3.6 nm in diameter. The FE-SEM micrographs show an agglomerate of spherical particles of 3–12 nm in diameter, with a pronounced maximum in the size distribution at around 3.5 nm. The various methods of characterization allow us to conclude that the size of the nanoclusters is largely preserved if they are deposited on the substrate. Therefore, the technique presented here might be an efficient means to produce silicon quantum dots of about 3 nm in diameter. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360737
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  • 5
    Electronic Resource
    Electronic Resource
    Remarks on nonequilibrium contributions to the rate of chemical reaction in the Lorentz gas (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6192-6193 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The conception of nonequilibrium Shizgal–Karplus temperature is analyzed for a chemical reaction in three component Lorentz gas. The results for nonequilibrium contributions to the rate of chemical reaction obtained by this conception are similar to those obtained from perturbation method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461594
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  • 6
    Electronic Resource
    Electronic Resource
    A novel medium-energy ion emitter for active spacecraft potential control (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2293-2297 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ion emission instrument has been developed to actively control the electrostatic surface potential of a spacecraft in orbit. Spacecraft surfaces tend to charge positive when their conductive surfaces are partially sunlit, and photoelectrons emitted, and the spacecraft is positioned outside of the very dense plasma region which is referred to as plasmasphere. A small, lightweight instrument with a lifetime of more than 104 h at a nominal emission current of 10 μA was the design goal. The ion emitter is based on the liquid metal ion source principle; a constant stream of liquified indium is evaporated from the tip of a needle and ionized; the ions are then extracted by a strong electric field. The size of the instrument is about 18 by 15 by 23 cm (length×width×height) and the entire instrument weighs about 1.9 kg and consumes 2.4 W of electrical power in the nominal emission mode. An instrument of this type is already operational on the Japanese Geotail spacecraft, while five more instruments are at the stage of flight model assembly for integration on the Russian Interball satellite and the ESA/NASA four-spacecraft Cluster mission. The Geotail instrument is functioning as expected. Preliminary results show that the ion emitter is able to reduce surface potentials of +70 V (highest value observed up to now) down to 2–4 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143924
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  • 7
    Electronic Resource
    Electronic Resource
    Interference method for monitoring the refractive index and the thickness of transparent films during deposition (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1200-1203 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An interferometric method is described for simultaneous measurement of the refractive index and the thickness of transparent isotropic films during the deposition process. Two laser beams are focused impinging at two different angles onto the film. The intensity of the beams reflected from the growing film shows minima and maxima, which are counted and evaluated to determine the refractive index n and the thickness d of the film in the range of some 100 nm up to several micrometers using 633-nm laser light. n and d can be determined within an accuracy better than 1%, if the thickness is larger than three times the vacuum wavelength of the laser. The measurements are well in accordance with calculations of the intensity modulation. The method can easily be extended to multilayer systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141212
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  • 8
    Electronic Resource
    Electronic Resource
    Band-gap renormalization and band filling in Si-doped GaN films studied by photoluminescence spectroscopy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4400-4402 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied band-gap renormalization and band filling in Si-doped GaN films with free-electron concentrations up to 1.7×1019 cm−3, using temperature-dependent photoluminescence (PL) spectroscopy. The low-temperature (2 K) PL spectra showed a line-shape characteristic for momentum nonconserving band-to-band recombination. The energy downshift of the low-energy edge of the PL line with increasing electron concentration n, which is attributed to band-gap renormalization (BGR) effects, could be fitted by a n1/3 power law with a BGR coefficient of −4.7×10−8 eV cm. The peak energy of the room-temperature band-to-band photoluminescence spectrum was found to decrease as the carrier concentration increases up to about 7×1018 cm−3, followed by a high-energy shift upon further increasing carrier concentration, due to the interplay between the BGR effects and band filling. The room-temperature PL linewidth showed a monotonic increase with carrier concentration, which could be described by a n2/3 power-law dependence. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371377
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  • 9
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    Simultaneous neutron and x-ray imaging of inertial confinement fusion experiments along a single line of sight at Omega (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-04-17
    Description: Neutron and x-ray imaging provide critical information about the geometry and hydrodynamics of inertial confinement fusion implosions. However, existing diagnostics at Omega and the National Ignition Facility (NIF) cannot produce images in both neutrons and x-rays along the same line of sight. This leads to difficulty comparing these images, which capture different parts of the plasma geometry, for the asymmetric implosions seen in present experiments. Further, even when opposing port neutron and x-ray images are available, they use different detectors and cannot provide positive information about the relative positions of the neutron and x-ray sources. A technique has been demonstrated on implosions at Omega that can capture x-ray images along the same line of sight as the neutron images. The technique is described, and data from a set of experiments are presented, along with a discussion of techniques for coregistration of the various images. It is concluded that the technique is viable and could provide valuable information if implemented on NIF in the near future.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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  • 10
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    Quantifying equation-of-state and opacity errors using integrated supersonic diffusive radiation flow experiments on the National Ignition Facility (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-04-25
    Description: A well diagnosed campaign of supersonic, diffusive radiation flow experiments has been fielded on the National Ignition Facility. These experiments have used the accurate measurements of delivered laser energy and foam density to enable an investigation into SESAME 's tabulated equation-of-state values and CASSANDRA 's predicted opacity values for the low-density C 8 H 7 Cl foam used throughout the campaign. We report that the results from initial simulations under-predicted the arrival time of the radiation wave through the foam by ≈22%. A simulation study was conducted that artificially scaled the equation-of-state and opacity with the intended aim of quantifying the systematic offsets in both CASSANDRA and SESAME . Two separate hypotheses which describe these errors have been tested using the entire ensemble of data, with one being supported by these data.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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