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  • American Institute of Physics (AIP)  (24)
  • 1990-1994  (17)
  • 1985-1989  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Visible and uv spectra of a polydiacetylene with a side group conjugated to the main chain (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5510-5517 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The polarized reflection spectra of single crystals of PDA-CPDO [poly-1-(N-carbazolyl)penta-1, 3-diyn-5-ol], which are π conjugated between the side groups and the main chain, have been measured in the photon energy region from 1.38 to 32 eV for the first time with a polarized synchrotron radiation source. Absorption spectra have been calculated using the Kramers–Kronig relation. Transitions in the visible absorption spectrum, which have been previously attributed to an interband transition in a similar polydiacetylene, have been found to be highly dichroic with respect to the direction along the polymer backbone. The absorption spectrum in this region reveals two broad (ΔE(approximately-greater-than)0.4 eV) peaks at 1.9 and 2.7 eV with an almost equal absorption coefficient of 7.5×104 cm−1. The spectral features in the range from 3 to 8 eV result from electronic transitions of the carbazolyl side groups. A single broad (ΔE∼10 eV) absorption band observed at 18 eV is due to either transitions of σ electrons to higher σ* or π* states of the carbazolyl group, or to ionization processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459620
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  • 2
    Electronic Resource
    Electronic Resource
    High-performance Zn-doped-base InP/InGaAs double-heterojunction bipolar transistors grown by metalorganic vapor phase epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1111-1113 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the successful growth of high-quality InP/InGaAs double-heterojunction bipolar transistors with heavily Zn-doped base layers (p=4×1019 cm−3) using metalorganic vapor phase epitaxy. Interrupting the growth for 30 min after growing a heavily Si-doped subcollector (n=2×1019 cm−3) is shown to eliminate the excessive nonequilibrium group III interstitials that enhance abnormal Zn diffusivity in the subsequently grown base region. Gummel plots of the fabricated microwave transistors show that they have ideal turn-on characteristics in spite of having only 5-nm-thick undoped spacer layers inserted between the emitter and base. The transistors obtain a maximum oscillation frequency fmax of 178 GHz and a current gain cutoff frequency fT of 126 GHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110844
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  • 3
    Electronic Resource
    Electronic Resource
    Broadband near-infrared pulse generation in KTiOPO4 (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2757-2760 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A broadband near-infrared pulse covering 700 nm around 2.4 μm has been generated by a dispersion-free parametric mixing in a KTiOPO4 crystal between the fundamental pulse (0.8 μm) from a Ti:sapphire regenerative amplifier and the white continuum pulse. It is tunable within the wavelength region of 1.7–2.9 μm. The comparison with a theoretical bandwidth indicates that the noncollinear phase matching plays a part for the spectral broadening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356213
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic properties and magnetostriction in grain-oriented (TbxDy1−x)(Fe1−yMny)1.95 compounds : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7024-7026 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties and magnetostriction in grain-oriented (TbxDy1−x)(Fe1−yMny)1.95 compounds with 0.3≤x≤0.5, 0≤y≤0.2 prepared by the Bridgman method have been investigated. It is confirmed that the Mn substitution not only lowers the spin reorientation temperature but also enhances λ〈100〉. This large λ〈100〉 is contradictory to the single-ion model. For Tb0.5Dy0.5 (Fe0.9Mn0.1)1.95 compound, no spin reorientation, which induces the sharp drop in the magnetostriction is seen in the temperature range from 77 to 400 K. In addition, by choosing the appropriate compressive stress, the quite excellent thermal stability and the large magnetostriction of 2000 ppm in the low applied field can be realized in the Tb0.5Dy0.5 (Fe0.9Mn0.1)1.95 compound. These features make Tb0.5Dy0.5 (Fe0.9Mn0.1)1.95 a promising material applicable to the various giant magnetostrictive actuators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358075
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  • 5
    Electronic Resource
    Electronic Resource
    Millimeter wave amplification in a free electron laser with a focusing wiggler (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 36-42 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mm wave amplifier experiment on a free electron laser was performed using an intense, mildly relativistic electron beam (0.7–0.9 MeV) with a combination of a focusing planar wiggler and a weak additional axial magnetic field in the so-called "group 1'' region. A beam transport ratio of over 80%, through the whole wiggler length, was realized. In an amplification experiment, a spatial growth rate of 56 dB/m was obtained at a frequency of 45 GHz, and a power saturation was observed at a level of 6 MW, where the total gain was estimated to be 52 dB. It was shown that the off-axis component of the beam contributes considerably to the rf amplification in the focusing wiggler.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355861
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  • 6
    Electronic Resource
    Electronic Resource
    Scanning Lorentz electron microscope with high resolution and observation of bit profiles recorded on sputtered longitudinal media (invited) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5811-5815 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A transmission electron microscope operating with a cold field emission source has been modified to facilitate differential phase contrast mapping and applied to the observation of microscopic magnetic features appearing in recorded longitudinal media. After describing the design and performance of the scanning Lorentz electron microscope, as we call it, results on the observation of bit patterns delineated on Co-based sputtered longitudinal media are presented. Relations of observed bit profiles to macroscopic magnetic properties of media and to device performance are discussed. Then, magnetization fluctuation on a scale of magnetic crystallites constituting the medium is examined. Also given is an account of a stray field effect inherent in hard magnetic materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353534
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  • 7
    Electronic Resource
    Electronic Resource
    Changes in soft magnetic properties of Fe multilayered films due to lattice mismatches between Fe and intermediate layers (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4338-4344 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe multilayered films with various intermediate layers are formed. Their magnetic properties and film structures are examined to understand the mechanism originating soft magnetic properties. The soft magnetic properties change with the lattice mismatches between Fe and intermediate layers, showing low coercive force and high relative permeability at lattice mismatches from 0.4 to 1.2%. It is thought that the lattice mismatches above 0.4% decrease Fe crystallite size and improve soft magnetic properties. Although Fe crystallite size is small at the lattice mismatches above 1.2%, the soft magnetic properties are poor. This is because the large lattice mismatch increases internal stress and magnetic anisotropy energy. This report indicates that the good soft magnetic properties are obtained when both Fe crystallite size and internal stress are small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343981
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  • 8
    Electronic Resource
    Electronic Resource
    Band lineup for a GaInP/GaAs heterojunction measured by a high-gain Npn heterojunction bipolar transistor grown by metalorganic chemical vapor deposition (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4898-4902 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A GaInP(N)/GaAs( p) heterojunction bipolar transistor was fabricated by metalorganic chemical vapor deposition (MOCVD) for the first time. The common-emitter current gain exceeded 200 at a current density around 10 A/cm2 and the offset voltage was as small as 50 mV. Thermionic emission theory indicates that the conduction-band discontinuity (ΔEc) at GaInP/GaAs heterointerface is as small as 30 meV at room temperature and this value was more than 160 meV smaller than 0.19–0.22 eV obtained by the C-V profile method. The band-gap energy for MOCVD-grown GaInP was 60 meV smaller than the intrinsic band-gap energy (1.91 eV), but this value is too small to explain the difference between the present ΔEc value and the previously reported ΔEc value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343205
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  • 9
    Electronic Resource
    Electronic Resource
    Triplet exciton formation due to interaction between singlet excitons in polydiacetylene (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7404-7416 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The time-resolved spectroscopy in polydiacetylene single crystals (PDA-MADF {poly-1-[3-(methylamino)phenyl]-4-[3,5-bis(trifluoromethyl)phenyl]-1, 3-butadiyne}) on femtosecond and picosecond time scales was performed. The time dependence of the photoinduced reflectance change in PDA-MADF exhibits three components with lifetimes ∼200 fs, 1–2 ps, and (very-much-greater-than)200 ps. These components are assigned to the free 1Bu excitons, self-trapped excitons, and triplet excitons. From the excitation intensity dependence of the reflectance change, a significant role of bimolecular interactions between singlet excitons for the formation of triplet excitons is clarified. A model of the mechanism of triplet exciton formation after the creation of singlet excitons is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465721
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  • 10
    Electronic Resource
    Electronic Resource
    4.8-keV x-ray backlight framing method for observing images of soft-x-ray-driven fusion capsules (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 706-710 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on a diagnostic method for observing the implosion asymmetry of soft-x-ray-driven fusion capsules. The method consists of an x-ray backlight source using a 4.8-keV quasi-monochromatic titanium x-ray source and a fast multiframe x-ray imaging system. With the proper combination of spectral filters and photocathode to reduce intense background x rays from a gold cavity plasma, x-ray backlighting images of the fusion capsules have been successively obtained with spatial and temporal resolutions of 20 μm and 80 ps, respectively. These images are used to study the implosion velocity and the lower-mode distortion caused by x-ray irradiation nonuniformity on the imploding fusion capsule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144202
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