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  • 1
    Electronic Resource
    Electronic Resource
    Simulation of ion transport through curved-solenoid macroparticle filters (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1740-1747 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion transport through curved-solenoid macroparticle filters is investigated using a parabolic potential model of the electric field. Consideration of the ion equations of motion shows that the filter efficiency will increase with the relative radius of curvature of the solenoid and decrease with the relative length of the input region. If the magnetic field is constant in the input region, transport efficiencies of up to 100% are predicted. We argue that the observed effect of axial magnetic field on the angular distribution of ions emitted from the cathode spot can be explained by electric fields changing ion trajectories after emission, rather than a change in spot behavior. Detailed calculations give the energy and angular distributions with which the ions exit the filter. Focusing effects are observed and seen to affect the ion transport−particularly when the ions are not emitted on the filter axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351697
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  • 2
    Electronic Resource
    Electronic Resource
    Polarization forces and conductivity effects in electrorheological fluids (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1334-1340 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Forces between particles aligned into chains by an applied electric field in an electrorheological (ER) fluid are calculated using finite-element techniques and, approximately, using a dipole approximation with local-field effects. Evaluation of the effective dielectric constant is emphasized and the shear modulus is derived from the shear dependence. For high-frequency (f(approximately-greater-than)0.1–1 kHz) applied electric fields, the forces and the modulus depend upon the dielectric constants of the suspending fluid and the dispersed particles. For low-frequency or dc electric fields, the conductivities of the components are dominant. These effects are treated within a Maxwell–Wagner approach. If the ratio of particle-to-fluid conductivities substantially exceeds the ratio of dielectric constants, a large enhancement of the modulus is found. Implications for the design of ER fluids are discussed briefly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351743
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  • 3
    Electronic Resource
    Electronic Resource
    Metal Schottky barrier contacts to alpha 6H-SiC (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4757-4760 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of Schottky barrier contacts to n-type 6H-SiC for a number of metals chosen to include a variety of physical and chemical properties has been investigated. The metals (Pd, Au, Ag, Tb, Er, Mn, Al, and Mg) were deposited onto room temperature surfaces terminated with a submonolayer coverage of oxygen. The metal/6H-SiC interface chemistry and Schottky barrier height φB during contact formation were obtained with x-ray photoemission spectroscopy; the electrical properties of subsequently formed thick contacts were characterized by current-voltage and capacitance-voltage techniques. The øB values for these metals extend over a wide 1.3 eV range. To a varying degree φB depends on the 6H-SiC crystal face (Si vs C). Mg and Al (Si face of latter) have φB=0.3 eV, a value which is suitable for nonalloyed ohmic contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352086
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  • 4
    Electronic Resource
    Electronic Resource
    Resolution limits of ion milling for fabricating Y1Ba2Cu3Ox nanostructures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2461-2463 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A process is described for fabricating 0.23-μm-wide lines in Y1Ba2Cu3Ox thin films where patterns are defined in a commercial, negative tone, epoxy-based resist by masked ion beam lithography and transferred to the superconducting film by argon ion milling. Lines in 80-nm-thick films had the same zero-resistance temperature (89 K) as the starting films, and a critical current density of 0.7×106 A/cm2 at 77 K, representing a threefold reduction from the starting value. A consistent interpretation of these results is that the line consists of a superconducting core 70 nm in width with the critical current density of the starting film and with 80-nm-wide nonsuperconducting sidewalls. The results were reproducible in lines which did not cross outgrowths in the superconducting film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351112
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic properties of silicon δ-doped InSb (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 671-675 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated magneto-transport and cyclotron resonance (CR) of two-dimensional electron gas in silicon δ-doped p-InSb under a magnetic field of up to 12 T at 4.2 K. Because there are multiple subbands occupied, Shubnikov–de Haas oscillations show a beating behavior. The CR spectra also display several peaks originating from different subbands. Effective masses of electrons associated with the lowest three subbands can therefore be directly determined, and they are in excellent agreement with a self-consistent calculation, which takes into account the electrostatic Poisson equation, the Schrödinger equation, and realistic sample parameters. Furthermore, we observed an absorption peak, whose resonance position has anomalous angle dependence. It is attributed to impurity CR where donors are in the vicinity of the δ-doped sheet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351850
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  • 6
    Electronic Resource
    Electronic Resource
    The reaction dynamics of sodium with ozone (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 2515-2521 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of sodium atoms (Na) with ozone (O3) has been studied using crossed molecular beams at a collision energy of 18 kcal/mole. The only product observed was NaO. The reaction occurs via an electron-transfer mechanism that yields NaO which is forward scattered with respect to the sodium beam. The translational energy distribution peaks near the forward stripping limit but extends out to the maximum allowed by energy conservation. The fragmentation ratio of NaO upon electron bombardment ionization I(NaO+)/[I(NaO+)+I(Na+)] as a function of product translational energy has been measured for an electron energy of 200 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463089
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  • 7
    Electronic Resource
    Electronic Resource
    Interactions between primitive electrical double layers (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9258-9266 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A free energy density functional theory is applied to predict the electrostatic force between charged surfaces immersed in the restricted primitive electrolyte, in which ions are represented by charged hard spheres and solvent by a uniform dielectric continuum. The particle correlation due to hard-core exclusions is incorporated in the nonlocal density functional of inhomogeneous hard sphere fluid. The ion–ion electrostatic correlation is treated in the mean spherical approximation. The surface force is found to depend strongly on the electrolyte concentration, surface charge density, and valency of the counterions. Attractive forces are often observed, especially in electrolytes containing divalent counterions. The maximum of the attraction can be an order of magnitude stronger than the van der Waals force evaluated at the same surface separation. The prediction of the classical Poisson–Boltzmann theory that the surface force is always repulsive is qualitatively correct only for monovalent electrolytes at low concentrations and surface charges. The results for an asymmetrical electrolyte resemble those of a symmetrical electrolyte with counterions of the same valency. The theoretical predictions agree well with available computer simulation results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463301
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  • 8
    Electronic Resource
    Electronic Resource
    A three-component model of the electrical double layer (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 494-503 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A three-component model of the electrical double layer is studied using a free energy density functional theory, which incorporates in an appropriate way the excluded volume effects and the electrostatic correlations. The new model differs from the primitive model in that the solvent is represented as a dense fluid of neutral hard spheres instead of as merely a dielectric continuum. The interfacial structure shows much richer features in the three-component electrolyte solution than either in the primitive electrolyte or in the pure hard sphere fluid. In particular we observe the coexistence of the particle layerings and the charge inversion. The electrical double layer in the three-component model is of comparatively shorter range and has a lower electrostatic potential difference across the interface than in the primitive model. The inclusion of the solvent also has large effects on the thermodynamic properties of the electrical double layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463595
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  • 9
    Electronic Resource
    Electronic Resource
    Structure of a dipolar hard sphere fluid near a neutral hard wall (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4639-4645 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The position-orientation distribution of a dipolar hard sphere fluid in contact with a neutral hard wall is studied using a density functional theory. Effects of hard sphere exclusions are incorporated in the excess hard sphere free energy density functional. Orientational correlations between the dipoles are taken into account through approximating the pair correlation function of the inhomogeneous dipolar fluid by that of the homogeneous one of the same chemical potential and dipole moment. The latter is obtained by solving reference quadratic hypernetted chain equation. Theoretical results agree well with those of computer simulations which are available at high density. The theory predicts a qualitatively different interfacial structure at low density and high dipole moments from that at high density; the former is very similar to the liquid/vapor interface of dipolar fluids with regard to both the density distribution and orientational order. The theory also demonstrates that different density distributions correspond closely to different orientational orderings of the dipoles at the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462800
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  • 10
    Electronic Resource
    Electronic Resource
    Reaction dynamics from orbital alignment dependence and angular distributions of ions produced in collision of Ba(1P) with NO2 and O3 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 2777-2785 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Angular distributions, orbital alignment dependence, and energy dependence of the relative cross sections of various ions produced in crossed beams collisions of electronically excited barium with O3 and NO2 were used to explore the dynamics of these reactions. The Ba+ product from both reactions showed strong dependence on alignment of the Ba(1P) p orbital with respect to the relative velocity vector. The Ba+ was generally forward or forward-sideways scattered, with the latter favored by the dominant perpendicular orbital alignment. Similar results for Ba+ from both O3 and NO2 suggest that electron transfer is favored for large impact parameter collisions in which the Ba p orbital is directed toward the molecule at the critical configuration, regardless of the symmetry of the available orbital in the isolated molecule. BaO+2 from the O3 reaction exhibited angular distributions and energy dependences which were reminiscent of the Ba+, albeit 2 orders of magnitude lower in intensity, indicating a close relationship between these two channels. Important differences in the dynamics for the BaO+ channel were suggested in the angular distributions, which show a substantial backscattered component, as well as the alignment effects and energy dependence. These indicate that the BaO+ probably derives from neutral BaO* which is sufficiently internally excited to undergo vibrational autoionization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462026
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