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  • 1
    Electronic Resource
    Electronic Resource
    Effects of dephasing and vibronic structure on the first hyperpolarizability of strongly charge-transfer molecules (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1917-1924 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dispersion of the first molecular hyperpolarizability β of strongly charge-transfer chromophores is investigated. The investigation extends the well-known Oudar–Chemla nonresonant two-level model into the resonant regime. An equation for β that includes the effect of dephasing and vibrational structure of electronic states is derived. It is shown that if only the dephasing mechanism is included in the two-level model, the intrinsic hyperpolarizability β0 calculated using the Oudar–Chemla equation from the hyper-Rayleigh scattering (HRS) experimental data will decrease with decreasing the excitation wavelength. The trend is reversed when the vibrational structure is also incorporated. It is concluded that in order to obtain a consistent β0 in the HRS experiment using an excitation wavelength in the resonance regime, it is inadequate to include only the dephasing mechanism. The vibronic structure also plays an important role and needs to be considered in the data analysis in order to obtain a β0 to agree with the off-resonance experimental result. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480754
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  • 2
    Electronic Resource
    Electronic Resource
    Composition and structure of the O-specific side chain of endotoxin from Serratia marcescens (1973)
    s.l. : American Chemical Society
    Biochemistry 12 (1973), S. 309-315 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00726a021
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  • 3
    Electronic Resource
    Electronic Resource
    Composition and structure of the O-specific side chain of endotoxin from Serratia marcescens 08 (1973)
    s.l. : American Chemical Society
    Biochemistry 12 (1973), S. 1948-1955 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00734a018
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  • 4
    Electronic Resource
    Electronic Resource
    Cathodoluminescence analysis of cleaved facets of a ZnSe p–n junction (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3823-3828 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnSe diodes grown on (100) GaAs substrates by molecular beam epitaxy were investigated using cathodoluminesence (CL) measurements at sample temperatures between 50 and 300 K. The CL line scans at different photon energies were performed on cleaved p–n junctions at 50 and 300 K, respectively. Taking into account surface recombination, carrier generation volume, carrier diffusion and internal built-in electric field and related carrier drift, the CL measurements from cleaved p–n junctions could be qualitatively explained. The charge depletion layer has a strong influence on the CL measurements. The calculated charge depletion width is in good agreement with CL measurements. The experimental data from the spatially resolved CL on the cleaved ZnSe diodes revealed important information of the carrier dynamics and recombination processes in these devices. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372420
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  • 5
    Electronic Resource
    Electronic Resource
    Resonant and nonresonant hyper–Rayleigh scattering of charge-transfer chromophores (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4209-4217 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first molecular hyperpolarizabilities (β) of a series of charge-transfer nonlinear optical (NLO) chromophores are measured with the hyper-Rayleigh scattering (HRS) technique using two excitation wavelengths at 1064 and 1907 nm. The 1907 nm wavelength is the longest excitation wavelength used for the HRS experiment. For some of these chromophores, β values in excess of 1000×10−30 esu at 1907 nm are obtained, and due to two-photon enhancement, even greater β values are found with the 1064 nm excitation. Chromophores with such large hyperpolarizability are expected to have potential applications in practical electro-optical devices. The dispersion of β is analyzed using a two-vibronic-state model developed previously in our laboratory. The study shows that it is necessary to consider the vibronic structure of the chromophore in the excited state in order to account for the behavior of the first molecular hyperpolarizability of the charge-transfer NLO chromophores. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1354636
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  • 6
    Electronic Resource
    Electronic Resource
    Nanostructure of thin amorphous hydrogenated carbon films studied by positron annihilation and photoluminescence (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 404-410 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We deposited polymer-like a-C:H films using the plasma-enhanced chemical vapor deposition technique and characterized film microstructure by variable-energy positron lifetime spectroscopy, photoluminescence (PL), and UV-visible absorption spectroscopy. It was confirmed that PL occurs from a chromophore in a sp2 cluster as a result of fast recombination of a photoexcited electron-hole pair. Positron annihilation lifetime spectroscopy showed that positronium (Ps) formation takes place via electron-positron recombination in the sp3 matrix. The lifetime of ortho-positronium (o-Ps) in our a-C:H films was similar to that in polyethylene, indicating their polymer-like nature. The relative PL efficiency increased by about an order of magnitude with increasing film band gap from 1.3 to 3.4 eV, which can be related to the decreasing concentration of nonradiative centers. On the other hand, Ps formation was much less influenced by the band gap and nonradiative centers. Comparison of this result with that for polyethylene mixed with carbon-black nanoparticles, where a considerable reduction in Ps formation was observed, showed that nonradiative centers were of a different nature from the defects on the carbon nanoparticle surface. This work demonstrated the usefulness of positron lifetime spectroscopy combined with optical measurements to study the nanostructure of a-C:H. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378063
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  • 7
    Electronic Resource
    Electronic Resource
    The Preparation of 3,3-Dimethylphthalide and Several of its Derivatives1 (1947)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 69 (1947), S. 1909-1911 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01200a019
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  • 8
    Electronic Resource
    Electronic Resource
    Shear force scanning near-field optical microscope based on a piezoelectric bimorph cantilever (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 2344-2349 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we present a simple, nonoptical shear force detection scheme to control probe–sample distance for a scanning near-field optical microscope (SNOM). Shear force detection is realized by attaching a tapered optical fiber probe to a piezoelectric bimorph cantilever in which one piezo layer generates a maximum piezo voltage when the cantilever is excited at resonance by the other piezo layer. The amplitude of the piezo voltage will decrease as the probe approaches a sample's surface due to probe–sample interacting shear force. Keeping the piezo voltage constant provides a very sensitive method by which to control probe–sample distance. Based on the shear force detection scheme, a shear force SNOM system has been built, operating in transmission collection mode. Shear force topographic and optical images have been taken using uncoated optical fiber probes fabricated by a chemical etching technique. The results suggest that the system is very reliable, repeatable, and easy to use. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1367360
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  • 9
    Electronic Resource
    Electronic Resource
    Stokes slip flow through a grid of circular cylinders (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 14 (2002), S. 3358-3360 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Stokes flow through a row of equally spaced circular cylinders with partial slip on the boundaries is studied by domain decomposition and matching. The pressure drop or resistance across the grid is found for various slip and normalized cylinder radii. Asymptotic formulas are found for sparcely and closely spaced cylinders. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1499127
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  • 10
    Electronic Resource
    Electronic Resource
    Raman depolarization ratio and short-range order in liquid crystals (1972)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 94 (1972), S. 8605-8607 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00779a067
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