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  • American Institute of Physics (AIP)  (103)
  • Wiley  (100)
  • Wiley-Blackwell  (60)
  • National Academy of Sciences  (16)
  • 1990-1994  (246)
  • 1970-1974  (33)
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  • 11
    Electronic Resource
    Electronic Resource
    Poor intergrain connectivity of PbMo6S8 in sintered Mo-sheathed wires and the beneficial effect of hot-isostatic-pressing treatments on the transport critical current density (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1606-1613 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure of Mo-sheathed Chevrel-phase superconducting wires was investigated by high-resolution scanning electron microscopy (SEM). Excess Pb forms small nodules (10–30 nm) on the Chevrel-phase grains or wetting layers between the Chevrel grains. The critical current density Jc is strongly reduced when wetting layers are present. However, second-phase Mo exists as islands as large as 2–10 μm and has little harmful effect on Jc. Although some Mo-sheathed wires sintered at 700 °C show relatively high Jc ( ≥ 2 × 108 A/m2 at 8 T), the Chevrel phase in these wires has a very porous microstructure, and the Jc values measured with a magnetic field parallel to the current, Jc((parallel)), were only about 10% higher than the Jc values measured with a field perpendicular to the current, Jc(⊥). This clearly suggests that the transport current flows percolatively in these wires. Much denser microstructures were obtained by hot-isostatic-pressing (HIP) treatments at 1200 °C, and very high Jc values, (approximately-greater-than) 5 × 108 A/m2 at 8 T and 9.3 × 107 A/m2 at 23 T, which are of the order of the highest Jc values so far reported, were observed. High-resolution SEM observations of HIP'ed wires demonstrate that the interconnectivity between the Chevrel grains was much improved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349525
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  • 12
    Electronic Resource
    Electronic Resource
    Characteristics of the electroluminescence and photoluminescence emission of erbium ions doped in InP and the energy transfer mechanism (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6993-6998 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The characteristics of impact excitation of the 1.54-μm emission due to intrashell transitions of 4f electrons of erbium atoms (4I13/2 →4 I15/2) doped into InP were investigated in comparison with the photoluminescence (PL) emission of the same peak from the same sample. The thermal quenching of this Er-related electroluminescence (EL) emission was found to be very small in contrast to the large thermal quenching of the PL emission. The EL emission intensity at room temperature was half that at 77 K, and the temperature dependence of the emission energy and the spectral width was very small. Due to almost temperature-independent nature of the impact excitation process, the quenching of the EL emission intensity reflected directly that of the fluorescence efficiency of this intrashell transitions of Er 4f electrons. Using this result, the temperature dependence of the PL energy transfer efficiency was also obtained. It was also found that the fine structure of the 1.54-μm emission was different between EL and PL. It was speculated that Er atoms on different lattice sites, which were in different crystal fields, were excited depending on excitation processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349801
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  • 13
    Electronic Resource
    Electronic Resource
    A thermally stimulated process in magnetic complex permeabilities of light illuminated yttrium iron garnet with some degrees of oxygen vacancy : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6034-6036 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: On warming the previously white light illuminated yttrium iron garnet with some deficiency of oxygen with a white light, an imaginary part of permeability μ‘ below 10 kHz has been found to show the triple peaks as a function of temperature, the activation energies of which are 0.095–0.22, 0.50, and 0.81 eV, respectively. Furthermore, the height of each peak depends strongly on the illuminating time of exciting light. These features have been discussed and interpreted based on a modified "two-center'' model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347781
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  • 14
    Electronic Resource
    Electronic Resource
    Background impurity dependence of redistributions of implanted gallium in silicon during annealing (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5385-5387 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: About 85% of Ga implanted into As doped Si, about 80% of that into Sb doped Si, and about 78% of that into P doped Si were lost into atmosphere during annealing at 950 °C for 30 min. The number lost depended on impurities in native oxide films on the Si surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347018
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  • 15
    Electronic Resource
    Electronic Resource
    Observation of torsional motion in the ground-state cation of jet-cooled tolane by two-color threshold photoelectron spectroscopy (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 1649-1654 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution threshold photoelectron spectra of jet-cooled tolane (C6H5–C≡C–C6H5) have been obtained by two-color (1+1') resonantly enhanced multiphoton ionization via the S1 state {1B1u(ππ*)}. From the threshold photoelectron spectra, the adiabatic ionization energy has been determined to be Ia = 63 917 ± 3 cm−1 (7.9243±0.0004 eV). A vibrational progression due to torsional motion in the cation ground state was observed up to its fifth quantum level with a fundamental frequency of 54 cm−1, showing small anharmonicity. From these results, we have evaluated the potential barrier height to the torsional motion to be 1980±60 cm−1. The threshold photoelectron spectra obtained via several S1 vibronic levels exhibit dominant peaks due to the Δv=0 ionization transitions. This fact indicates that no significant change occurs in molecular structure upon photoionization with removal of the antibonding π electron from the S1 state. Threshold photoelectron bands arising from formally forbidden odd quantum transitions in the torsional mode were also clearly observed with small intensities. The mechanism of the appearance of such a nontotally symmetric mode is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463153
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  • 16
    Electronic Resource
    Electronic Resource
    Vibrational spectra of aniline–Arn van der Waals cations (n=1 and 2) observed by two-color "threshold photoelectron'' [zero kinetic energy (ZEKE)-photoelectron] spectroscopy (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6399-6406 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements of mass-selected ion-current and threshold photoelectron spectra of jet-cooled aniline–Arn van der Waals complexes (n=1 and 2) have been carried out with a two-color resonantly enhanced multiphoton ionization (REMPI) technique using a high-resolution threshold photoelectron analyzer developed in this laboratory. From our (1+1') REMPI experiments via the respective excited S1 states, we have obtained photoelectron spectra with well-resolved vibrational progressions due to "low-frequency van der Waals modes'' of the cations; νvdW=16 cm−1 (n=1) and νvdW=11 cm−1 (n=2). From Franck–Condon calculations, we have assigned these low-frequency vibrations to the "van der Waals bending'' of the cations. We have also found that the angles of the van der Waals bonds in the cations are changed by 8.2 (n=1) and 8.8 (n=2) degrees with respect to the S1 states. The adiabatic ionization potentials (Ia) of aniline and the aniline–Arn complexes (n=1 and 2) have been determined as 62 268±4 cm−1 (aniline), 62 157±4 cm−1 (n=1), and 62 049±4 cm−1 (n=2). Their shifts ΔIa are 111 cm−1 (n=1) and 219 cm−1 (n=2) with respect to aniline. Spectral shifts due to complex formation have been observed for a total of 13 ring modes of the cations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462634
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  • 17
    Electronic Resource
    Electronic Resource
    Chemical equilibrium in simple fluids: Solvent density dependence of the dimerization equilibrium of 2-methyl-2-nitrosopropane in argon and xenon (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3824-3829 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have studied the dimerization equilibrium of 2-methyl-2-nitrosopropane (MNP) at 60 and 35 °C in argon and xenon up to densities about twice the critical density of the solvent. With an increase in the solvent density, the dimerization equilibrium constant at 60 °C decreases in the low-density region, whereas it increases in the high-density region. The inversion of the density dependence occurs around ρr(approximately-equal-to)0.8 in argon and ∼1.4 in xenon, where ρr means the density reduced by the critical density of the solvent fluid. The equilibrium constant in xenon at 35 °C increases with increasing solvent density in the low-density region (ρr〈∼0.5), while it decreases in the medium-density region (0.5〈ρr〈1.5). The equilibrium constant in argon at 35 °C has a similar density dependence to that at 60 °C. The internal energy change for the dimerization shows a large density dependence in the low-density region of xenon, while it changes little with density in argon. The theoretical calculation by the Percus–Yevick (PY) approximation for a simple reaction model gives a poor result for the density dependence of the equilibrium constant, although the temperature dependence of the equilibrium constant is reproduced qualitatively. The calculation for a more realistic model including the molecular anisotropy of MNP suggests that the density dependence at the low-density limit is sensitive to the interaction model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461887
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  • 18
    Electronic Resource
    Electronic Resource
    Absence of photoelectron spectroscopic evidence for "proton tunneling'' in the cation ground state of jet-cooled tropolone (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 9401-9403 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: From our high resolution REMPI threshold photoelectron measurements of jet-cooled tropolone, it has been found that no spectral doublet showing "proton tunneling'' in the cation ground state (D0) is observed within an experimental accuracy of 2 cm−1. The adiabatic ionization potential was obtained as Ia=68 365±5 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461168
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  • 19
    Electronic Resource
    Electronic Resource
    Vibronic coupling in the ground cationic state of naphthalene: A laser threshold photoelectron [zero kinetic energy (ZEKE)-photoelectron] spectroscopic study (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7763-7772 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The two-color (1+1') threshold photoelectron spectra of naphthalene in a supersonic free jet have been recorded via nine vibronic levels of the S1 electronic state up to about 1420 cm−1 above the S1 band origin. The threshold photoelectron spectra recorded via the S1 band origin and via totally symmetric ag vibronic levels show significant intensity in Δν=+1 transitions in nontotally symmetric vibrations having b1g symmetry indicating that the ionization transition gains significant intensity through a vibronic coupling mechanism between the two lowest doublet cationic states. The strongest departure from the expected Δν=0 propensity in the threshold photoelectron spectra occurs through excitation of the totally symmetric 8 mode having ag symmetry indicating that a considerable displacement occurs along the normal coordinate of this 8 mode upon ionization from the S1 state. The superior resolution of the threshold photoelectron technique over conventional photoelectron methods has allowed accurate values for the fundamental vibrational frequencies of naphthalene in its ground cationic state to be determined and it has also allowed a more rigorous investigation of the vibronic coupling mechanism that occurs between the two lowest doublet cationic states. Moreover, an improved value for the adiabatic ionization energy of naphthalene of 65 687±7 cm−1 (8.1442±0.0009 eV) has been determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464584
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  • 20
    Electronic Resource
    Electronic Resource
    Energy partitioning in the dissociation reaction Ar3+→Ar2++Ar (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 1022-1027 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Threshold-photoelectron photoion coincidence (TPEPICO) spectra of argon clusters ionized with synchrotron radiation have been observed, and the average kinetic energy of Ar2+, which originates from Ar3+, has been estimated. All the line shapes of the Ar2+ ion observed in the TPEPICO spectra have been appropriately simulated in terms of superposition of a sharp and a broad Gaussian function, where the sharp Gaussian function corresponds to ionization of the argon dimer Ar2. The observed line shapes agree very well with the simulated ones, implying that the excess energy in the Ar3 ionization is thermally or quasithermally partitioned to translational energy of the fragment species. From the average kinetic energies of Ar2+, it has been found that the percentage of excess energy in Ar3+, that is partitioned into the total translational energy of the fragment species, is dependent on the excitation energy. The percentage is slightly less than the value of 40% expected from statistical theory. It has also been found that complete dissociation of Ar3+ takes place in the excess energy range 0.3–1.1 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463281
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