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  • 1
    Electronic Resource
    Electronic Resource
    Electrical and Optical Alignment Processes in Some Novel Liquid-Crystalline Side-Chain Polymers As Studied by Dielectric Relaxation Spectroscopy (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 8463-8469 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00129a001
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental and theoretical studies of the performance of quantum-well infrared photodetectors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 993-1003 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the performance of GaAs/AlGaAs quantum-well infrared detectors exhibiting intersubband absorption in the 8–14 μm band. The dark current characteristics have been investigated as a function of barrier width and electron density in the well and compared with a model which takes into account thermionic emission and thermally assisted tunneling in the Wentzel–Kramers–Brillouin approximation. The model gives a good description of the data and is extended to predict the variation of detectivity and background limited operating temperature with structural parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349612
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  • 3
    Electronic Resource
    Electronic Resource
    Photoluminescence studies of free-standing quantum boxes (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3472-3480 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report photoluminescence measurements made on free-standing, lattice-matched GaAs/AlGaAs and pseudomorphic InGaAs/GaAs quantum boxes fabricated by laterally patterning quantum wells using electron-beam lithography and either reactive ion etching or ion beam milling. At temperatures below 10–20 K the luminescence efficiency of most of the GaAs quantum-box arrays tends to scale with the volume of quantum-well material remaining after processing even for the smallest boxes which have lateral dimensions of only 40–50 nm. These observations indicate that the surface recombination rate in GaAs submicron structures can be small relative to the radiative recombination rate at low temperatures. In contrast, radiative recombination in the InGaAs/GaAs quantum boxes is strongly quenched for lateral dimensions less than 500 nm. We suggest that this is because photoexcited carriers are laterally localized in the GaAs boxes by potentials of the order of a few meV, possibly associated with interface disorder or strain relaxation, and that such localization effects are smaller in the InGaAs boxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345337
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  • 4
    Electronic Resource
    Electronic Resource
    Drude conductivity of highly doped GaAs at terahertz frequencies (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2382-2385 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time domain spectroscopy has been used to measure the room temperature transmission of highly doped GaAs in the frequency range from 0.2 to above 3 THz. We studied n- and p-type layers, with carrier densities between 1016 and 2×1018 cm−3, which had been grown on undoped GaAs substrates. Transmission spectra could be fitted within experimental error by using a Drude model for the conductivity. Fitted carrier densities for both carrier types and mobilities for p-type GaAs were in good agreement with the results of Hall measurements. In the case of n-GaAs, the optically determined mobility appeared to underestimate slightly the Hall mobility. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372238
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  • 5
    Electronic Resource
    Electronic Resource
    Polarization-dependent efficiency of photoconducting THz transmitters and receivers (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2069-2071 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The emission and detection efficiencies of photoconducting THz transmitters and receivers are found to be sensitive to the polarization of the optical gating pulse. Signal amplitudes from GaAs coplanar stripline transmitters and silicon-on-sapphire dipole receivers vary by factors of up to 4 and 3, respectively, with rotation of the exciting pulse polarization. In both cases, maximum signal is obtained when the polarization of the normally incident light is perpendicular to the edge of the metal electrodes. This polarization sensitivity, which appears to arise from differences in the spatial distribution of photoexcited carriers in the semiconductor, needs to be considered when optimizing the signal-to-noise ratio in coherent THz spectroscopy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121278
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  • 6
    Electronic Resource
    Electronic Resource
    Coherent control of cyclotron emission from a semiconductor using sub-picosecond electric field transients (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2647-2649 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated the excitation and control of coherent cyclotron emission from a semiconductor using a THz beam containing pairs of sub-picosecond electric field pulses closely spaced in time. The source of THz radiation in these experiments is a biased coplanar stripline fabricated on semi-insulating GaAs and edge illuminated with pairs of temporally and spatially separated 70 fs pulses of near infrared light. A GaAs/AlGaAs two-dimensional electron gas was used in the experiments because of its long intraband phase relaxation time. Changes in the amplitude and phase of the cyclotron emission are observed when varying the interpulse delay and are well described within the theoretical framework of a two level system. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120167
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  • 7
    Electronic Resource
    Electronic Resource
    Double-charge-transfer spectroscopy using a modified Finnigan 8230 spectrometer (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 548-551 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A Finnigan 8230 mass spectrometer has been converted to a translational-energy-loss spectrometer suitable for double-charge-transfer (DCT) spectroscopy. Its performance was investigated by obtaining DCT spectra when 3keV OH+ projectile ions interacted with xenon atoms and ethene molecules. Well-separated peaks were obtained which correspond to the populating of dicationic electronic states differing in energy by about 1 eV.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070629
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  • 8
    Electronic Resource
    Electronic Resource
    A comparative study of theoretical methods for the analysis of high-resolution double-charge-transfer spectra, applied to the ethene molecule (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 552-554 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The low-energy electronic states of the ethene dication are investigated theoretically, a comparison being made between the predictions of the ab initio ADC(2) Green's function method and of the recently developed semi-empirical MSXα method. Both methods provide a consistent unambiguous analysis of the closely-spaced peak structure recently observed in a high-resolution double-charge-transfer spectrum for the ethene molecule.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070630
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular mobility of substituted poly(p-phenylenes) characterized by a range of polymer relaxation techniques (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1465-1481 
    Details
    ISSN: 0887-6266
    Keywords: poly(phenylene) ; dielectric ; dynamic mechanical ; relaxation ; free volume ; positron annihilation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The free volume and related mobility properties of substituted poly(p-phenylene) polymers are examined. The techniques used range from positron annihilation, dielectric relaxation, and dynamic mechanical spectroscopy to thermally stimulated currents. Fractional free volume is determined for the samples with different substituted side groups and related to the glass transition temperature. Bulkier groups lead to a greater fractional free volume and lower glass transition temperatures. Comparison of molecular relaxation times using the different characterization techniques demonstrates that there is strong coupling between motion of the main chain and the side groups, on which the dipoles reside. Intermolecular coupling between the main chains at the primary relaxation is shown in this work to be related to the nature of the side chains and resultant free volume, as are the temperature locations of local, secondary relaxations. A qualitative model describing the effect of regiochemistry on the motions and packing of these materials is also proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1465-1481, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Measured and calculated double-ionization energies of 2-haloethanolsIn recognition of the outstanding service of John Holmes to the mass spectrometry community during his 15 years as Editor of Organic Mass Spectrometry. (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 1144-1147 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Double-charge-transfer spectroscopy was used to measure the double-ionization energies of the 2-haloethanols FCH2CH2OH, ClCH2CH2OH, BrCH2CH2OH and ICH2CH2OH; the values obtained were 30.1 ± 0.5, 28.1 ± 0.5, 27.6 ± 0.5 and 26.9 ± 0.5 eV, respectively. In addition, the energies were calculated using ab initio methods and the GAUSSIAN 90 program package. The measured and calculated values for FCH2CH2OH are in agreement, but for the three other molecules the calculated values are significantly lower than those measured. The discrepancies in the calculations are due mainly to the underestimation of correlation energies by the appropriate MP2 method, which becomes progressively worse with increasing number of electrons in the system.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210281027
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