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  • 1
    Electronic Resource
    Electronic Resource
    The semiclassical limit of the two-dimensional quantum Yang–Mills model (1994)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 35 (1994), S. 5354-5361 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The semiclassical limit of the quantum Yang–Mills partition function on a compact oriented surface is related to the symplectic volume of the moduli space of flat connections, by using an explicit expression for the symplectic form. This gives an independent proof of some recent results of Witten and Forman.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530756
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  • 2
    Electronic Resource
    Electronic Resource
    An explicit description of the symplectic structure of moduli spaces of flat connections (1994)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 35 (1994), S. 5338-5353 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The moduli space of flat connections on a principal G-bundle over a compact oriented surface of genus g≥1 is considered herein. Using the holonomies around noncontractible loops, the moduli space is described as a quotient of a submanifold of G2g. An explicit expression is obtained for the symplectic form on the smooth part of moduli space, and several properties of this form are established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530755
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  • 3
    Electronic Resource
    Electronic Resource
    Role of the HNO3↔NOH Isomerization in reactions (i) NH(3Σ−)+O(3P) and (ii) N(4S)+OH(2Π): Ab initio calculations and quantum statistical Rice–Ramsperger–Kassel analysis of the potential energy surfaces (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3906-3915 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The minimum energy potential energy surfaces for combination of NH(3Σ−)+O(3P) to form HNO(1A',3A‘) and N(4S)+OH(2Π) to form NOH(3A‘), and the isomerization of HNO(1A',3A‘) to NOH(1A',3A‘), decomposition of NOH(1A',3A‘) to N(4S)+OH(2Π) as well as to H(2S)+NO(2Π) and HNO(3A‘) to H(2S)+NO(2Π) have been obtained by the ab initio methods with geometry optimization at the 6–311G**/MP2=full level with corrections for electron correlation at the MP4SDTQ=full level. At all stationary points on the potential energy surfaces (PES), correction for the zero point vibrational energies are made. The addition reactions to form energized adducts have then been analyzed using a bimolecular version of the quantum statistical Rice–Ramsperger–Kassel (QRRK) theory at different temperatures and pressures. Our analysis predicts that at all temperatures isomerization of HNO(3A‘) to NOH(3A‘) and its reverse isomerization are important. Formation of NO(2Π) in the interstellar clouds can take place from decomposition of NOH(3A‘) as well as HNO(3A‘).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467508
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrafast nonexponential dynamics in a polymer glass forming liquid (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 1673-1683 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The orientational dynamics of phenyl side groups in poly(methylphenylsiloxane) (PMPS) melts are examined over a broad range of viscosity/temperature (η/T) using subpicosecond transient grating optical Kerr effect (TGOKE) measurements. Measurements on poly(dimethylsiloxane) are also reported. Following ultrafast (hundreds) of fs librational dynamics, the phenyl side group orientational dynamics occur over a range of times from 2 ps to a few hundred ps. The experiments were performed from 25 to 143 °C, resulting in η/T changing by a factor of 40. In spite of the large change in η/T, the side group dynamics remain unchanged throughout the entire temperature range. Comparison of the dynamics of PMPS in the melt and PMPS in dilute CCl4 solution shows that chain–chain interactions influence the phenyl side group dynamics in the melt. The dynamics are described as local orientational relaxation of phenyl groups in the microenvironments defined by the backbone geometry and side group steric interactions rather than rotational diffusion. The dynamics exhibit power-law behavior, t−α, over two decades of signal decay. Two possible physical processes that can give rise to a power-law decay are discussed. The relationship of the observed dynamics to the β and α relaxations of glass forming liquids is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466595
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  • 5
    Electronic Resource
    Electronic Resource
    Current density dependence of the activation energy in type II superconductors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 592-595 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have conducted magnetic relaxation experiments to calculate the effective activation energy, U, as a function of critical current density. We have shown that, from the nonlinearity of U, one can explain the nonlogarithmic decay of magnetization in type II superconductors. The nonlinearity of U was considered by expanding U about a current density, J0. The coefficients of expansion were determined experimentally and were used to develop the relationship between U and J for both conventional type II superconductors (Nb3Sn filamentary) and high-Tc superconductors (YBa2Cu3O7−δ and Bi2Sr2CaCu2Oy single crystals). Both types of superconductor were observed to behave in similar fashion. We have also calculated U0 using the standard formulas and the intercepts of the tangent of the U vs M curve and have found the results to be comparable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351837
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  • 6
    Electronic Resource
    Electronic Resource
    Schottky diodes using poly(3-hexylthiophene) (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2957-2958 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Schottky barrier diodes have been fabricated using poly(3-hexylthiophene)(P3HT) as the semiconductor and indium as the metal. P3HT was doped with FeCl3 at room temperature to form a p-type semiconductor. The Schottky junctions of In on FeCl3-doped P3HT using pressure contact exhibit rectification ratios ranging from 104:1 to 106:1 at a bias of ±1 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355319
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  • 7
    Electronic Resource
    Electronic Resource
    Spectroscopic ellipsometry studies of YBa2Cu3O7−δ deposited on SrTiO3 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 8272-8276 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric function ε=ε1−iε2 of the YBa2Cu3O7−δ high-Tc superconducting films grown on (100) SrTiO3 (c-axis oriented) and (110) SrTiO3 (ab-oriented) substrate was measured by spectroscopic polarization modulation ellipsometry (SPME) and changes in film orientation were studied by comparing films of various thicknesses. The films deposited on SrTiO3 (100) substrates demonstrated an isotropic ε1 that changed with film thickness. It is observed that the decrease in the metallic dielectric behavior associated with the increase in the thickness of the films grown on (100) SrTiO3 substrates is mainly due to a change in the orientation of the films. The films deposited on SrTiO3 (110) showed anisotropic dielectric behavior when the plane of polarization is parallel and perpendicular to the c-axis of the film. These studies show that for this high-temperature superconductor with anisotropic dielectric behavior, SPME is a highly sensitive technique capable of measuring small changes in the film orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347435
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  • 8
    Electronic Resource
    Electronic Resource
    Diatomic molecules, rotations, and path-integral Monte Carlo simulations: N2 and H2 on graphite (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 6031-6051 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational motion of homonuclear diatomic molecules confined to two dimensions at finite temperatures is discussed within the framework of path-integral Monte Carlo (PIMC) techniques. For single rotators the symmetry restriction on the total wave function coupling nuclear spin and rotations of these diatomic molecules is carried over to PIMC for fermionic and bosonic diatomic molecules. Three experimentally relevant quantum statistical averages are formulated, and quantum effects due to discrete level spacing and exchange are separated with the help of these averages. The method is applied to single N2 and H2 rotators adsorbed on graphite in the frozen-in crystal field which is due to the commensurate ((square root of)3×(square root of)3)R30° "2-in'' herringbone phase. Contrary to H2, exchange effects are negligible for N2 in the relevant temperature range. The resulting sign problem for certain combinations of molecule and averaging procedure is discussed. PIMC simulations of the phase transition from the translationally (square root of)3-ordered and orientationally disordered phase to the herringbone phase were carried out for complete N2 monolayers without a symmetry restriction on the wave function. Due to dispersive quantum fluctuations, transition temperature and ground-state order parameter are depressed by roughly 10% as compared to classical MC simulations of the same realistic model. In addition, the PIMC results are compared to quasiharmonic and quasiclassical approximations. The quasiharmonic treatment yields the correct order parameter suppression, the quasiclassical simulation the lowering of the transition temperature, but only the full quantum PIMC simulations describe the entire temperature range of interest correctly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466186
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  • 9
    Electronic Resource
    Electronic Resource
    Generation of Tollmien–Schlichting waves by harmonic excitation (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 1213-1222 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The creation of wavy disturbances (Tollmien–Schlichting waves) by a localized two-dimensional disturbance source vibrating periodically at a fixed frequency in a Blasius boundary layer is discussed. The initial-boundary value problem mathematically models the vibrating ribbon experiment of Schubauer and Skramstad. By considering the ribbon vibration to start at t=0, in the model one gets the transient and the eventual periodic part of the solution. The results of the full simulation are compared with the time-asymptotic solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868290
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  • 10
    Electronic Resource
    Electronic Resource
    Flux pinning in hot isostatically pressed Bi2Sr2CaCu2Ox (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2823-2825 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic hysteresis data were taken from 4.2 to 35 K on Bi2Sr2CaCu2Ox samples that were hot isostatically pressed at 105 MPa in an inert atmosphere at 825 °C. One set of samples was pressed for only 15 min while the other was pressed for 120 min. The samples pressed for 15 min contained a high density of dislocations and planar faults, while the samples pressed for 120 min contained fewer dislocations and faults, with most dislocations present within subgrain boundaries. The samples with the complex dislocation/planar fault structures exhibited substantially larger hysteresis loops, suggesting enhanced flux pinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108049
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