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  • American Institute of Physics (AIP)  (17)
  • Cambridge University Press  (7)
  • 1985-1989  (24)
  • 1965-1969
  • 1989  (24)
  • 1
    Electronic Resource
    Electronic Resource
    An investigation of the annihilated unrestricted Hartree–Fock wave function and its use in second-order Møller–Plesset perturbation theory (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1789-1795 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The recently introduced annihilated unrestricted Hartree–Fock (AUHF) wave function—in which the first spin contaminant in an unrestricted Hartree–Fock (UHF) wave function has been annihilated self-consistently—is discussed in some detail with particular attention to its use as a basis for a perturbation expansion. A series of calculations are presented highlighting the advantages and disadvantages of a second-order Møller–Plesset (AUMP2) perturbation treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457084
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic field effects on triplet exciton fission and fusion in a polydiacetylene (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6642-6646 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have studied the origin and decay dynamics of triplet excitons in the conjugated polymer poly(4BCMU) in its sol(yellow) and gel(red) phases. Wavelength and intensity dependencies of the triplet yield show that the triplet exciton cannot be produced by excitation into the singlet exciton edge but only from higher lying states. The observed lifetime of the triplet state, coupled with the magnetic field dependence of the triplet state production and decay, indicate that the triplet state is created by a fission process from the excited singlet. The time and magnetic field dependence of the triplet exciton decay indicate that the triplet exciton decay in the red phase occurs by diffusive bimolecular fusion, but in the yellow phase the triplet exciton decay is nondiffusive. We postulate that the unimolecular decay of the triplet exciton in the yellow phase results from exciton pinning by conformational disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456281
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  • 3
    Electronic Resource
    Electronic Resource
    Solution to boundary value problems using the method of maximum entropy (1989)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 30 (1989), S. 302-306 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The method of maximum entropy is used to solve a class of linear boundary value problems. The method is based on using various moments of the differential equation as constraints when maximizing the entropy. Various examples are presented and compared to exact solutions for varying numbers of moments. It is found that the maximum entropy approximation is, in many cases, better than a Fourier series solution for a given number of expansion terms and moments. The method is very general and will find applications in many areas of physics. A comparison of the amount of work necessary for the maximum entropy solution versus finite difference techniques is presented and it is found that the maximum entropy technique shows promise as an alternative solution technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528445
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  • 4
    Electronic Resource
    Electronic Resource
    Carbon diffusion in undoped, n-type, and p-type GaAs (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 687-689 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of background doping, surface encapsulation, and As4 overpressure on carbon diffusion have been studied by annealing samples with 1000 A(ring) p-type carbon doping spikes grown within 1 μm layers of undoped (n−), Se-doped (n+), and Mg-doped (p+) GaAs. The layers were grown by low-pressure metalorganic chemical vapor deposition using CCl4 as the carbon doping source. Two different As4 overpressure conditions were investigated: (1) the equilibrium pAs4 over GaAs (no excess As), and (2) pAs4 ∼2.5 atm. For each As4 overpressure condition, both capless and Si3N4-capped samples of the n−-, n+-, and p+-GaAs crystals were annealed simultaneously (825 °C, 24 h). Secondary-ion mass spectroscopy was used to measure the atomic carbon depth profiles. The carbon diffusion coefficient is always low, but depends on the background doping, being highest in Mg-doped (p+) GaAs and lowest in Se-doped (n+) GaAs. The influence of surface encapsulation (Si3N4) and pAs4 on carbon diffusion is minimal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101822
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  • 5
    Electronic Resource
    Electronic Resource
    Oriented high Tc superconductive layers on silver by devitrification of glasses formed in the Bi-Sr-Ca-Cu oxide system (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 371-373 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Highly oriented crystalline layers of Bi4(Sr,Ca)3Cu4O16+x high Tc superconductors were produced by the devitrification of aerosol suspensions of glasses prepared from the mixed oxides when the suspensions were brought into rapid contact with heated silver substrates. The best magnetic susceptibility signals, produced by superconductivity at 77 K, were obtained when the glass was rapidly heated to about 850 °C from room temperature. The deposited layers are composed of a nearly pure superconductive phase in the form of flat platelets up to several hundred microns in diameter that are oriented with the c axis normal to the substrate. The addition of a small amount of Pb to the glass lowers the optimum deposition temperature and improves the crystal morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101453
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  • 6
    Electronic Resource
    Electronic Resource
    Observation of nonlinear optical transmission and switching phenomena in polydiacetylene-based directional couplers (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1829-1831 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear optical transmission and switching phenomena have been observed in directional coupler devices fabricated from soluble polydiacetylenes. Effects due to both slow thermal nonlinearities and ultrafast (picosecond) electronic nonlinearities were identified. At the operating wavelength of 1.06 μm used here, the ultrafast electronic nonlinear phenomena originated from intensity-dependent changes in the imaginary part of the refractive index due to two-photon absorption effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102179
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  • 7
    Electronic Resource
    Electronic Resource
    Heavy carbon doping of metalorganic chemical vapor deposition grown GaAs using carbon tetrachloride (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1905-1907 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mixture of 500 ppm CCl4 in H2 has been used to grow heavily doped p-type GaAs by low-pressure metalorganic chemical vapor deposition with TMGa and AsH3 as the group III and V sources, respectively. Carbon acceptor concentrations between 1×1016 and 1×1019 cm−3 were obtained. In addition, abrupt carbon-doping profiles were achieved with no noticeable memory effects. Carrier concentration was studied as a function of CCl4 flow, V/III ratio, growth temperature, and growth rate using electrochemical capacitance-voltage profiling. Carbon incorporation was found to depend on CCl4 flow, V/III ratio, and growth temperature. Carbon incorporation had no dependence on the growth rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101237
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  • 8
    Electronic Resource
    Electronic Resource
    Depth-dependent native-defect-induced layer disordering in AlxGa1−xAs-GaAs quantum well heterostructures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 262-264 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence measurements on annealed single-well Alx Ga1−x As-GaAs quantum well heterostructures demonstrate that layer disordering caused by native defects is strongly depth dependent. The depth-dependent layer disordering, as well as the corresponding depth-dependent net carrier concentration, is a consequence of the re-equilibration of the V−Ga vacancy and the As+Ga antisite native defect concentrations via the crystal surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100984
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  • 9
    Electronic Resource
    Electronic Resource
    CO2 large-area discharge laser using an unstable-waveguide hybrid resonator (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1950-1952 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A one-dimensional unstable resonator combining free-space and waveguide propagation is used to efficiently extract power from a large-area gain medium in a slab waveguide CO2 laser. A power of 240 W in a near-diffraction-limited beam has been attained at 12% conversion efficiency from a 38 cm gain length in a compact sealed-off laser head, corresponding to a specific power extraction of 14 kW m−2 of discharge area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101203
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  • 10
    Electronic Resource
    Electronic Resource
    Power scaling of large-area transverse radio frequency discharge CO2 lasers (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1833-1835 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report experimental results on gain medium area scaling of laser output power for large-area, transverse rf discharge excited carbon dioxide lasers. Power extraction to 20 kW/m2 has been achieved, indicating the significant potential of this technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101250
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