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  • American Institute of Physics (AIP)  (25)
  • International Union of Crystallography (IUCr)
  • 1
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    Nucleophilic substitution with two reactive centers: The CN− + CH3I case (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-11-13
    Description: The nucleophilic substitution reaction CN − + CH 3 I allows for two possible reactive approaches of the reactant ion onto the methyl halide, which lead to two different product isomers. Stationary point calculations predict a similar shape of the potential and a dominant collinear approach for both attacks. In addition, an H-bonded pre-reaction complex is identified as a possible intermediate structure. Submerged potential energy barriers hint at a statistical formation process of both CNCH 3 and NCCH 3 isomers at the experimental collision energies. Experimental angle- and energy differential cross sections show dominant direct rebound dynamics and high internal excitation of the neutral product. No distinct bimodal distributions can be extracted from the velocity images, which impedes the indication of a specific preference towards any of the product isomers. A forward scattering simulation based on the experimental parameters describes accurately the experimental outcome and shows how the possibility to discriminate between the two isomers is mainly hindered by the large product internal excitation.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
    Electronic Resource
    Electronic Resource
    TMX-U computer system in evolution (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1880-1882 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Over the past three years, the total TMX-U diagnostic data base has grown to exceed 10 Mbytes from over 1300 channels; roughly triple the originally designed size. This acquisition and processing load has resulted in an experiment repetition rate exceeding 10 min per shot using the five original Hewlett–Packard HP-1000 computers with their shared disks. Our new diagnostics tend to be multichannel instruments, which, in our environment, can be more easily managed using local computers. For this purpose, we are using HP series 9000 computers for instrument control, data acquisition, and analysis. Fourteen such systems are operational with processed format output exchanged via a shared resource manager. We are presently implementing the necessary hardware and software changes to create a local area network allowing us to combine the data from these systems with our main data archive. The expansion of our diagnostic system using the parallel acquisition and processing concept allows us to increase our data base with a minimum of impact on the experimental repetition rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139159
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  • 3
    Electronic Resource
    Electronic Resource
    Database tools for enhanced analysis of TMX-U data (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1929-1931 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A commercial database software package has been used to create several databases and tools that assist and enhance the ability of experimental physicists to analyze data from the Tandem Mirror Experiment-Upgrade (TMX-U) experiment. This software runs on a DEC-20 computer in M-Divisions's User Service Center at Lawrence Livermore National Laboratory (LLNL), where data can be analyzed off line from the main TMX-U acquisition computers. When combined with interactive data analysis programs, these tools provide the capability to do batch-style processing or interactive data analysis on the computers in the USC or the supercomputers of the National Magnetic Fusion Energy Computer Center (NMFECC) in addition to the normal processing done by the TMX-U acquisition system. One database tool provides highly reduced data for searching and correlation analysis of several diagnostic signals within a single shot or over many shots. A second database tool provides retrieval and storage of unreduced data for use in detailed analysis of one or more diagnostic signals. We will show how these database tools form the core of an evolving off-line data analysis environment on the USC computers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138799
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  • 4
    Electronic Resource
    Electronic Resource
    The hyperfine structure in the electronic A 2E″←X 2E′ system of the pseudorotating lithium trimer (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2590-2602 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Sub-Doppler laser spectroscopy of the A 2E″←X 2E′ band of Li3 shows well-resolved and characteristic hyperfine structures of rovibronic transitions which can be explained in all detail by the interplay between the underlying Fermi-contact interaction, the symmetry species of the rovibronic states and the Coriolis coupling of rotational and pseudorotational motions. Ab initio calculated electron spin densities reproduce the observed line splittings to within 3%. In this Jahn–Teller distorted molecule magnetic equivalence of identical nuclei is strictly valid only for rovibronic states of A symmetry. However, it also holds for rovibronic states of E symmetry if they are of pure A vibronic origin, and it is enforced for many E states of pure E vibronic origin by Coriolis coupling. In contrast, those transitions which involve states with dominant Kc=0 rotation functions and/or with strong vibronic E/A mixing show significant changes in the hyperfine patterns due to magnetic inequivalence, sometimes called "hyperfine doubling." © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1376631
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical investigation of the autoionization process in molecular collision complexes: He*(2 3S)+Li(2 2S)→He+Li++e− (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 1484-1491 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A complete ab initio treatment is applied to the autoionization process in the He*(2s 3S)+Li(2s 2S) collisional complex. Feshbach projection based on orbital occupancy, implemented in a multireference configuration interaction (MRCI) code, defines the resonance state and provides the entrance channel potential curve as well as all pertinent information on the resonance–continuum coupling. The l-dependent coupling elements in local approximation are obtained by projecting a compact one-electron function, named Penning molecular orbital (PMO), onto the wave function of the ejected electron with proper energy. The continuum wave function is obtained by coupled channel calculations in the static-exchange approximation. A converged set of seven complex coupling matrix elements, used in the nuclear dynamics calculation based on a complex Numerov algorithm, fully describes the electron angular momentum transfer. The calculated angle-dependent spectra, as well as the total, angle-, and energy-integrated ionization cross sections agree well with available experimental data. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481935
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  • 6
    Electronic Resource
    Electronic Resource
    A simple predictive model of chemical potentials: H2(1Σg) and Li2(1Σg) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1144-1150 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple model for van der Waals potentials presented earlier [J. Chem. Phys. 80, 3726 (1984)] has been extended to describe chemical bonds by including the exchange-dispersion term of Herring and Flicker. For H2, the 1Σ ground state potential is predicted in excellent agreement with the accurately known ab initio potential, the well depth being reproduced to within 0.6%. New two configuration self-consistent-field (SCF) calculations for the 1Σ and the 3Σ states of Li2 have made it possible to test the model for this system as well. Here the discrepancy is only 3% in the well depth for the 1Σ Li2 potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461144
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  • 7
    Electronic Resource
    Electronic Resource
    Theoretical investigation of the autoionization process in molecular collision complexes: Computational methods and applications to He*(23S)+H(12S) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7139-7161 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The first complete ab initio treatment is applied to the autoionization process in the He*(2s3S)+H(1s) collisional complex. The autoionizing resonance state is defined through Feshbach projection based on orbital occupancy, and the corresponding potential is determined from multireference–configuration interaction (MR-CI) calculations with an accuracy of about 10 meV. The energy-dependent coupling with the continuum is derived from a compact (L2) molecular orbital (MO) without any phase information being lost. This "Penning MO" is projected onto the states of the continuum electron for energies that comply with the resonance condition thus providing the l-dependent coupling elements in local approximation. The continuum electron functions are calculated within the static-exchange approximation for up to 25 coupled angular momentum channels. The nuclear dynamics calculation is based on a complex Numerov algorithm and uses a converged set of seven complex coupling matrix elements. Weighting with experimental collision energy distributions finally gives the angle-dependent, as well as the angle-integrated, electron spectra for Penning and associative ionization processes. The results are discussed with respect to previous, either partial or model studies, and are compared with the recent most detailed experimental study of the angular-dependent Penning ionization electron spectra. The close agreement of theory and experiment demonstrates the adequacy of the local complex potential approach, as well as the importance of electron angular momentum transfer so far neglected in theoretical treatments. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473735
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  • 8
    Electronic Resource
    Electronic Resource
    Hole defects in molecular beam epitaxially grown p-GaAs introduced by alpha irradiation (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1222-1224 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial aluminum Schottky barrier diodes on molecular beam epitaxially grown p-GaAs with a free carrier density of 2×1016 cm−3 were irradiated with alpha particles at room temperature using an americium-241 (Am-241) radio nuclide. For the first time, the radiation induced hole defects are characterized using conventional deep level transient spectroscopy (DLTS). The introduction rates and DLTS "signatures'' of three prominent radiation induced defects Hα1, Hα4, and Hα5, situated 0.08, 0.20, and 0.30 eV above the valence band, respectively, are calculated and compared to those of similar defects introduced during electron irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356460
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  • 9
    Electronic Resource
    Electronic Resource
    Dual dielectric silicon metal-oxide-semiconductor field-effect transistors as radiation sensors (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1972-1976 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new design for radiation-sensing field-effect transistors (RADFETs) is presented, involving the use of very thick silicon nitride layers deposited on top of a high-quality thermal silicon dioxide. In contrast to previous RADFET fabrication procedures, no attempt was made to introduce hole traps into the thermal oxide. Instead the trapping layer at the nitride oxide interface was used to store the positive charge which forms the basis for operation of the RADFET. Data is presented which shows hole transport in the thermal oxide. Models explaining the field dependence of the response and the saturation behavior of the dual dielectric device are given. These RADFETs are more stable than any previously described in the literature and have a sensitivity of 86 μV/rad dose at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342887
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  • 10
    Electronic Resource
    Electronic Resource
    The two-dimensional structure of radiative divertor plasmas in the DIII-D tokamak : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1761-1773 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent measurements of the two-dimensional (2-D) spatial profiles of divertor plasma density, temperature, and emissivity in the DIII-D tokamak [J. Luxon et al., in Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1987), p. 159] under highly radiating conditions are presented. Data are obtained using a divertor Thomson scattering system and other diagnostics optimized for measuring the high electron densities and low temperatures in these detached divertor plasmas (ne≤1021 m−3, 0.5 eV≤Te). D2 gas injection in the divertor increases the plasma radiation and lowers Te to less than 2 eV in most of the divertor volume. Modeling shows that this temperature is low enough to allow ion–neutral collisions, charge exchange, and volume recombination to play significant roles in reducing the plasma pressure along the magnetic separatrix by a factor of 3–5, consistent with the measurements. Absolutely calibrated vacuum ultraviolet spectroscopy and 2-D images of impurity emission show that carbon radiation near the X-point, and deuterium radiation near the target plates contribute to the reduction in Te. Uniformity of radiated power (Prad) (within a factor of 2) along the outer divertor leg, with peak heat flux on the divertor target reduced fourfold, was obtained. A comparison with 2-D fluid simulations shows good agreement when physical sputtering and an ad hoc chemical sputtering source (0.5%) from the private flux region surface are used. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872278
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