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  • 11
    Electronic Resource
    Electronic Resource
    Experimental determination of the S1 torsional potential of 9,9'-bianthryl in 2-methyl-butane by simultaneous Franck–Condon and band shape analysis of temperature dependent optical fluorescence spectra (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6371-6381 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Optical fluorescence spectra of anthracene (AN) and of 9,9'-bianthryl (BA) have been measured in the apolar solvent 2-methyl-butane (2MB) at seven different temperatures in the range 123 K to 298 K. The AN spectra are strongly structured and consist of simple Franck–Condon (FC) progressions. The BA spectra on the other hand are broad and show unusual temperature dependencies. These effects are interpreted within a two state model with five vibrational and one torsional degree of freedom. A FC analysis is carried out using vibronic band shape functions which are convolutions of two functions. The first one is a Gaussian representing the spectral broadening due to librations and intermolecular interactions. The second one results from a semiclassical treatment of the intramolecular torsional mode (large amplitude motion, LAM). Optical transitions are assumed to occur from ensembles which are thermally equilibrated with respect to their nuclear degrees of freedom. The Boltzmann distribution with respect to the LAM potentials in combination with a change of the transition frequency as a function of the torsional angle cursive-phi is identified as the predominant broadening mechanism. The LAM potentials in the S0 and S1 state are represented by a three parameter cosine series. A nonlinear least-squares fit of the experimental spectra leads to a single consistent set of model parameters valid for all temperatures. The S1 double minimum LAM potential of BA in 2MB is found to have minima at cursive-phieq=62° (and 118°) and a local barrier at cursive-phi=90° of 255 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461558
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  • 12
    Electronic Resource
    Electronic Resource
    Bulk diffusion measurements to study the effectiveness of barrier layers: I. Mathematical treatment (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3799-3809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The exchange of a tracer material, e.g., a radioactive isotope, between two samples forming a diffusion couple depends on the rate of the diffusion of the tracer in each of the two samples and also on the rate of the transfer of the tracer across the interface between these samples which may or may not contain a barrier layer with a different chemical composition and/or structure. Diffusion couples with three different initial tracer distributions are considered. In order to extract from experimental data values for tracer diffusion coefficients and for the rate constant for the tracer transport across the interface, a detailed analysis of the required mathematics is given. This analysis is of interest as well for obtaining true values for bulk diffusivities and also to characterize quantitatively the resistance of interfaces (=barriers) to the exchange of certain species. Some examples of experimental results are presented and briefly discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402150
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  • 13
    Electronic Resource
    Electronic Resource
    Bulk diffusion measurements to study the effectiveness of barrier layers: II. Exchange of sodium between liquid crystal display glass substrates with different barrier layers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3810-3815 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Na-22 tracer diffusion experiments were performed to study the exchange of Na ions between liquid crystal display glass substrates (Corning Code 1737) separated by different types of layers. Different types of layers were generated (i) by RCA cleaning, (ii) by preannealing in wet air, and (iii) by low pressure chemical vapor deposition. A sandwich configuration was used to study the effect of such layers between two glass substrates on the exchange of Na ions between these substrates. The sandwiches were of the type substrate 1 (containing Na-22 tracer)/layer/substrate 2. Diffusion annealing of such sandwiches led to a redistribution of the sodium tracer. This redistribution was analyzed experimentally with regard to the sodium tracer diffusion coefficient in the bulk and the rate of the sodium tracer transfer across the layer. It was found that all three types of layers considered act as barrier layers, i.e., they suppress the exchange of Na ions between glass substrates. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402151
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  • 14
    Electronic Resource
    Electronic Resource
    Magnetotransport and magnetic properties of molecular-beam epitaxy L10 FePt thin films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6854-6856 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetotransport and magnetic properties of chemically ordered (001) L10 FePt epitaxial thin films with small scale perpendicularly magnetized stripe domains have been investigated. Film growth conditions are used to systematically vary the degree of chemical order, the magnetic anisotropy, and magnetic domain sizes. The longitudinal and transverse (Hall) resistivities are correlated with both film chemical order and magnetic properties. The low-field magnetoresistance shows evidence of domain effects. In the highest anisotropy and most chemically ordered film studied, this low field magnetoresistance is consistent with an intrinsic domain wall scattering contribution to the resistivity. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372864
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  • 15
    Electronic Resource
    Electronic Resource
    Determination of the Na–Kr interaction potential in the XΣ and AΠ state by laser spectroscopy (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5865-5874 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have extended our previous laser spectroscopic investigation of the AΠ–XΣ transition of the van der Waals molecule NaKr84. Our experimental data consist now of about 1300 absorption lines and of the spectral intensity distribution of the fluorescence light. Spectroscopic parameters have been derived for the vibrational states 0,...,2 of the XΣ state and 7,...,14 of the AΠ state. The interatomic potentials of the XΣ and the AΠ states have been determined in a fully quantum-mechanical approach using analytical HFD or Tang–Toennies functions. For the equilibrium distance and the well depth we obtain 4.918(4) A(ring), 68.4(5) cm−1 for XΣ and 3.03(4) A(ring), 3.05(4) A(ring) and 795(25) cm−1, 760(20) cm−1 for AΠ1/2 and AΠ3/2, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460470
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  • 16
    Electronic Resource
    Electronic Resource
    Particle acceleration in three-dimensional reconnection regions: A new test particle approach (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 4318-4327 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic Reconnection is an efficient and fast acceleration mechanism by means of direct electric field acceleration parallel to the magnetic field. Thus, acceleration of particles in reconnection regions is a very important topic in plasma astrophysics. In this paper we show that the conventional analytical models and numerical test particle investigations can be misleading concerning the energy distribution of the accelerated particles, since they oversimplify the electric field structure by the assumption that the field is homogeneous. These investigations of the acceleration of charged test particles are extended by considering three-dimensional field configurations characterized by localized field-aligned electric fields. Moreover, effects of radiative losses are discussed. The comparison between homogeneous and inhomogeneous electric field acceleration in reconnection regions shows dramatic differences concerning both, the maximum particle energy and the form of the energy distribution. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873696
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  • 17
    Electronic Resource
    Electronic Resource
    Extrinsic and intrinsic magnetoresistance contributions of CrO2 thin films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7699-7701 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of (010)-oriented CrO2 thin films on Al2O3(0001) substrates leads to a higher grain boundary density than the growth of (100)-oriented CrO2 thin films on isostructural TiO2(100) substrates. For both types of films an intrinsic linear contribution to the high field magnetoresistance (MR) due to spin disorder has been determined at T=300 K. This contribution does not depend on the crystalline quality of the films and supports the suggested intrinsic double exchange mechanism for CrO2. At low temperature (T=10 K) intergrain tunneling MR and Lorentz MR appear, which strongly depend on the crystalline properties of the CrO2 films. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362658
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  • 18
    Electronic Resource
    Electronic Resource
    Micromagnetics of mesoscopic epitaxial (110) Fe elements with nanoshaped ends (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5501-5503 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization reversal and magnetic domain configurations of 0.5-μm-wide epitaxial (110) Fe particles with rectangular and needle-shaped ends and competing magnetic anisotropies have been investigated. Magnetic force microscopy imaging and longitudinal Kerr hysteresis loop measurements in conjunction with micromagnetic simulations have been used to elucidate the basic micromagnetic behavior. End shape is shown to be a determining factor for the nucleation of magnetization reversal and the resulting magnetic domain configurations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369875
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  • 19
    Electronic Resource
    Electronic Resource
    Magnetoresistance, micromagnetism, and domain wall effects in epitaxial Fe and Co structures with stripe domains (invited) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5243-5248 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We review our recent magnetotransport and micromagnetic studies of lithographically defined epitaxial thin film structures of body-centered-cubic Fe and hexagonal-closed-packed (hcp) Co with stripe domains. Micromagnetic structure and resistivity anisotropy are shown to be the predominant sources of low field magnetoresistance (MR) in these microstructures, with domain wall (DW) effects smaller but observable (DW-MR(approximately-less-than)1%). In Fe, at low temperature, in a regime in which fields have a significant effect on electron trajectories, a novel negative DW contribution to the resistivity is observed. In hcp Co microstructures, temperature dependent transport measurements for current perpendicular and parallel to walls show that any additional resistivity due to DW scattering is very small. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369956
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  • 20
    Electronic Resource
    Electronic Resource
    A Langmuir/Mach probe array for edge plasma turbulence and flow : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 377-380 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have installed and operated a reciprocating Langmuir/Mach probe to simultaneously measure parallel and perpendicular plasma flow profiles along with density, temperature, floating potential profiles, and fluctuating parameters such as fluctuation driven particle flux and wave number on a single shot. Plasma facing components are made from boron nitride and the probe tips are 1-mm-diam carbon cylinders. The Mach probe, designed following the Gundestrup model, has 12 probes arranged in a circular array. Four Langmuir probes mounted at the front of the Mach probe array measure floating potential, ion saturation current, and temperature. The perpendicular flow velocity measurements reduced from the Mach probe array compare well with the phase velocity measured from the proud Langmuir probes and the Er×B poloidal rotation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147834
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