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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7832-7841 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multiphoton dissociation processes of acetylene via a two-photon resonant predissociative state, v=0 of 1Σ+g, have been studied by three techniques: time-resolved photofragment excitation spectroscopy (TRPFES), laser-induced fluorescence (LIF) of the C2 fragments, and dispersed emission. We found that the major dissociation products are H atoms, H2 molecules, and C2 molecules in the X 1Σ+g, a 3Πu and A 1Πu states; among the latter, C2 X 1Σ+g molecules are formed by a sequential bond–rupture mechanism whereas some C2 in a 3Πu is formed by a concerted two-bond fission process. Other, minor dissociation channels due to three-photon processes, such as C2(d 3Πg)+2H(2S(1)/(2)), C2(d 3Πg)+H2(X 1Σ+g), C2(C 1Πg)+H2(X), C2(e 3Πg)+H2(X), and C2(D 1Σ+u)+H2(X), were also detected. In the 2+1 concerted dissociation yielding C2(C 1Πg)+H2(X), a long-lived intermediate C2H2, likely a cis isomer or other conformer in which the hydrogen atoms are relatively close to each other, was revealed by TRPFES; its zero-pressure lifetime was estimated to be (8±1) μs. A long-lived intermediate C2H was also found in the 2+1 sequential dissociation by TRPFES.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7872-7876 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Crystal growth of a sillenite structure with a composition of Bi12(Si1−xTix)O20 and the corresponding optical characteristics have been systematically examined. The incongruent melting materials Bi12TiO20(BTO) have been observed to form a solid solution with congruent melting materials Bi12SiO20(BSO) for the whole range of the x value. The cutoff wavelength increases and the optical activity decreases linearly with BTO content in the crystals. The photorefractive effect is modified significantly due to the addition of BTO. The diffraction efficiency (η) of the photorefractive grating increases first with BTO content for x≤0.33 and saturates for a larger amount of BTO addition. The response speed is, however, promoted markedly for x≥0.48.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5152-5154 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Acicular α-(FeO)OH particles were synthesized using the chemical coprecipitation method with the reaction system of Fe2Cl2-NaOH. The Mo-modified γ-Fe2O3 particles are obtained by adding the proper amount of sodium molybdate to the solution of geothite, followed by the processes of dehydration, reduction, and oxidation. The thermal stability was investigated by thermal differential analysis. It was found that the transition temperature of γ-Fe2O3→α-Fe2O3 increases from 544 °C for the unmodified particles to 720 °C for particles containing 4% by weight of molybdenum. The improved thermal stability has the advantage that the temperature for the oxidation of Fe3O4 particles can be considerably increased without the risk of forming nonmagnetic α-Fe2O3 particles. The magnetization (σs) and coercivity (Hc) of the magnetic acicular γ-Fe2O3 have been determined from room temperature to 200 °C with a vibrating sample magnetometer. The results indicate that both σs and Hc at room temperature decrease with increasing Mo content. The dependence of Hc can be approximately described by the linear equation Hc=Hc,0(1−AT) over that temperature range. The temperature coefficient A decreases with Mo content until the Mo content reaches 4 wt. %. The origin of improved thermal stability is discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7660-7662 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The tetragonal c-axis alignment of Tc=23 K Pr1.85Ce0.15CuO3.97 superconducting powder was achieved in a 1 T alignment field with rotating powder/epoxy holder perpendicular to the alignment field. The in-plane penetration depth λab for this electron-doped superconductor was derived using zero-field-cooled Meissner diamagnetic data with low applied field (Ba〈Hc1ab) parallel to the c-axis aligned powder. A small Pr paramagnetic contribution was subtracted. The temperature dependence of Δλab(T)=λab(T)−λab(0) [with λab(0)∼133 nm] up to ∼0.5 Tc can be fitted well with a non-s-wave or d-wave-like power law Δλab(T)=AT2+CT4, where the T2 law is dominated at low temperature. The present result agrees with recent phase-sensitive experiment, which indicates d-wave nature for these electron-doped 214 cuprates. © 2001 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7484-7486 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High oxygen pressure annealed PrBa2Cu3O7−y (y∼0) cuprates were prepared in order to study the effect of oxygen stoichiometric parameter y on the unusual Pr/Cu magnetic properties and/or recently reported superconductivity. The oxygen-rich orthorhombic 123-chain phase is highly unstable under high-oxygen pressure synthesis and decomposes completely in 10 bar pressure. For a smaller 2 bar prepared sample a relatively clean phase was preserved with an oxygen parameter y=0.05, as compared with y=0.11 from a conventional 1 bar flowing oxygen method. No superconductivity can be detected for all high-oxygen pressure prepared samples. Instead, Mott-insulator behavior with anomalous high Pr ordering TN(Pr)=19 K was observed for PrBa2Cu3O6.95. Comparison with other Pr/Ba intersubstituted Pr1−xBa2−xCu3O7−y cuprates is discussed. © 2001 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3607-3609 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Efficient CdTe/CdS thin film solar cells have been the recent focus, in which the CdTe layers were reported by close-spaced sublimation, and oxygen was used to control the p-type conductivity of the deposited films. Both the fundamental gap and the impurity level were determined by the wavelength modulation reflectance spectroscopy, which demonstrates that while oxygen atoms have an ionization energy of about 0.1 eV, they do not behave as a simple shallow acceptor. This finding is supported by the electrical characterization. The oxygen concentration incorporated in the CdTe thin films were found to be in the range of 1019–1020 cm−3 by the IR measurements, while a carrier concentration between 1010 and 1012 cm−3 was obtained by Hall measurements.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4972-4974 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A hybrid method has been presented for calculating the resonant tunneling energy levels in a complex quantum structure. It couples the Airy function and plane wave function methods. And the δ-type potential, which may be at the boundary of two materials, has also been included.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2505-2506 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multiple-δ-doped GaAs field effect transistors using graded-like δ-doping profile are demonstrated and investigated. An extremely high carrier density of 1.2×1013 (7.9×1012) cm−2 along with an enhanced Hall mobility of 1700 (3300) cm2/v s at 300 (77) K for a triple-δ-doped GaAs structure are achieved. The dc characteristic reveals an extrinsic transconductance as high as 110 mS/mm at room temperature with a gate length of 2 μm. Three separated peaks in the transconductance versus gate bias curve are observed. Meanwhile, a broad and flat transconductance region is obtained. © 1995 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2864-2866 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A δ-doped GaAs/In0.2Ga0.8As p-channel heterostructure field-effect transistor grown by low-pressure metalorganic chemical vapor deposition is demonstrated. The mobilities and two-dimensional hole gas concentrations at 300 (77) K are 260 (2600) cm2/v s and 1012 (5.5×1011) cm−2, respectively. For a gate length of 1.5 μm, the maximum extrinsic transconductances are 15 mS/mm at 300 K and 24 mS/mm at 77 K. The high transconductances extend a wide range versus gate voltage. © 1995 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1075-1077 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A δ-doped GaAs/graded InxGa1−xAs/GaAs pseudomorphic structure grown by low-pressure metal-organic chemical vapor deposition was demonstrated for the first time. The graded InxGa1−x As layer in which the composition x ranged from 0.25 to 0.20 was strained to obtain a pseudomorphic structure. Furthermore, a δ-doped high-electron mobility transistor( δ-HEMT) employing a graded InxGa1−x As layer was successfully fabricated. Due to better electron confinement and lower interface roughness scattering, the present structure reveals higher saturation current density, higher transconductance, and higher product of mobility and two-dimensional sheet density as compared to those of conventional HEMTs which were also fabricated by the same system and procedure.
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