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  • 1
    Electronic Resource
    Electronic Resource
    Model studies of a conceptually new approach to the total synthesis of quinine (1985)
    s.l. : American Chemical Society
    The @journal of organic chemistry 50 (1985), S. 29-31 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00201a006
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  • 2
    Electronic Resource
    Electronic Resource
    Plakortin, an antibiotic from Plakortis halichondrioides (1978)
    s.l. : American Chemical Society
    The @journal of organic chemistry 43 (1978), S. 3454-3457 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00412a006
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  • 3
    Electronic Resource
    Electronic Resource
    Ambipolar diffusion and carrier lifetime measurements in all-binary (InAs)2(GaAs)5 strained quantum wells grown on GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1868-1873 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The in-well ambipolar diffusion coefficients and carrier lifetimes in ordered all-binary quantum wells, composed of (InAs)2(GaAs)5 short-period strained-layer superlattices (SPSLSs) grown on [001]-oriented GaAs substrates, are measured using picosecond optically induced transient grating and pump-probe techniques. Quantum wells containing SPSLSs may be expected to exhibit higher in-plane hole mobilities compared to InGaAs ternary alloy quantum wells because of a larger average indium content and reduced disorder scattering in the SPSLS structures. The results obtained in the SPSLSs are compared to those obtained in InGaAs alloy quantum wells of comparable well width and confinement energies. This indicates that, for a given SPSLS and its equivalent alloy, the ambipolar diffusion coefficients are comparable while the carrier lifetimes in the SPSLSs are longer. The longer carrier lifetimes in the SPSLSs suggest that these binary structures possess fewer nonradiative recombination centers than the alloys. The absence of a dramatic improvement in the transport properties, however, may indicate that imperfect interfaces in the SPSLSs may be offsetting their possible advantages, in spite of the fact that optical measurements in the SPSLSs indicate high quality and x-ray and transmission electron microscopic measurements demonstrate the binary nature of these structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355301
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature dependence of the Γ8v-Γ6c gap of GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2742-2747 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoluminescence (PL) peak positions of the ground state heavy and light-hole excitons on high-quality Molecular Beam Epitaxy grown GaAs/AlxGa1−xAs (x=0.3 and 1) multiquantum-well structures have been experimentally determined in the temperature range 4.2≤T≤340 K. Using these values and the well-known low-temperature energy of the GaAs Γ8V-Γ6C gap [EgΓ(GaAs,T=0 K)=1.5192 eV], we propose the temperature dependence to be EgΓ(GaAs,T)= 1.5192+5.16×10−5×T−1.99×10−6×T2 +2.60×10−9×T3 (EgΓ in eV). The nearly linear variation of EgΓ(GaAs,T) versus the temperature in the range 170 K≤T≤340 K can be approximated by a coefficient (dEgΓ/dT)=−4.4×10−4 eV/K, in excellent agreement with theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354674
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  • 5
    Electronic Resource
    Electronic Resource
    Room-temperature optical nonlinearities in strained (InAs)2(GaAs)5 superlattice quantum wells (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3243-3248 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report room-temperature measurements of the nonlinear absorption cross section, σeh, and the nonlinear refraction coefficient, neh, associated with saturation of excitonic absorption and bandfilling, for high-quality multiple quantum well (MQW) structures in which each well consists of a highly strained, all binary (InAs)2(GaAs)5 short-period superlattice. The three samples studied, which have effective well thicknesses of 10.7, 14.8, and 18.8 nm, respectively, each display clearly resolved excitonic resonances at room temperature. Picosecond nonlinear transmission and transient grating measurements were performed on each sample in the spectral vicinity of the n = 1 heavy-hole excitonic resonance. The peak values of neh and σeh extracted from these measurements are comparable to those measured in high-quality GaAs/AlGaAs and unstrained InGaAs/InP MQWs. We determine the dependence of σeh and neh on the width of the quantum wells, and we discuss the fluence dependence of the nonlinearities. Consistency between the differential transmission and transient grating diffraction efficiency is demonstrated via a Kramers–Kronig analysis of the differential transmission spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348544
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  • 6
    Electronic Resource
    Electronic Resource
    Picosecond optical nonlinearities in a strained InAs/GaAs hetero n-i-p-i structure (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 929-932 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear optical properties of a n-i-p-i structure containing strained superlattice quantum wells in the intrinsic regions are studied using picosecond pump and probe pulses of the same photon energy. For pump fluences as low as 1.1 μJ/cm2, a blue shift of the excitonic resonance, caused by the screening of the built-in space-charge field and the accompanying reduction in the quantum-confined Stark effect, is clearly observed. At higher fluences, the onset of bleaching of the excitonic absorption is observed. The nonlinearities associated with the quantum confined Stark effect in the hetero n-i-p-i are directly compared to those arising from excitonic bleaching in identical strained superlattice quantum wells under flatband conditions. The picosecond time resolution allows a more accurate estimation of the carrier density in the hetero n-i-p-i by ignoring the density-dependent recombination and a quantitative comparison between the strength of the nonlinearities in the two structures. Although such comparisons depend on the optical fluence and structure of the hetero n-i-p-i, we find that the magnitudes of the nonlinearities in these two specific structures are comparable on a per carrier basis, although their spectral signatures are quite distinct.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351315
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  • 7
    Electronic Resource
    Electronic Resource
    Optical nonlinearities and ultrafast charge transport in all-binary InAs/GaAs strained hetero n-i-p-i's (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6891-6897 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use picosecond differential spectroscopy to temporally and spectrally resolve the formation and decay of nonlinearities and space-charge fields in a hetero n-i-p-i that contains quantum wells in the intrinsic regions that are composed of all-binary InAs/GaAs short-period strained-layer superlattices. The evolution of the optical response is determined by competition between excitonic bleaching and the excitonic shift caused by screening of the built-in electric field of the n-i-p-i. The relative contributions of the two resulting optical nonlinearities are complicated functions of fluence, time, and wavelength, with the detailed dynamics determined by thermionic emission from the wells, picosecond charge transport over nanometer dimensions, screening, and recombination. At low fluences, excitonic bleaching is the source of an ultrafast nonlinear response that can be turned on and off in 〈10 ps. This initial excitonic bleaching gives way to a blue shift of the exciton as the carriers escape the wells in ∼3 ps and drift to screen the built-in field in 〈10 ps. The blue shift persists until the carriers recombine nonexponentially on microsecond time scales. At higher fluences, excitonic bleaching and the blue shift are observed simultaneously, since only a fraction of the carriers are required to screen the field and the wells remain partially occupied. On the time scale of ∼10 ns, the bleaching contribution disappears as the carriers within the wells recombine, leaving only the persistent blue shift.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349813
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  • 8
    Electronic Resource
    Electronic Resource
    Close-coupling optical model analysis: A refined optical potential surface for He*(2 1S)+H2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 240-245 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A complex-arithmetic version of Johnson's log–derivative integration method has enabled a straightforward extension of the close-coupling approximation to complex-potential surfaces. The complex-potential close-coupling (CPCC) method is applied to the determination from our earlier scattering measurements of an improved anisotropic optical potential for the He*(2 1S)+H2 Penning ionization system, with the aid of a new, nonpiecewise potential surface function based on the improved Tang–Toennies model. The potential is compared to earlier ab initio results, and the CPCC method is used to assess the shortcomings of the complex-infinite-order-sudden (CIOS) approximation. Variation of differential and ionization cross sections with the initial rotational state of H2 predicted by CPCC may be experimentally observable, and may also provide an explanation for the observed H2/D2 isotope effect in quenching rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455511
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  • 9
    Electronic Resource
    Electronic Resource
    Collision energy dependence of Penning ionization electron spectra in crossed supersonic beams: He*(2 1S)+N2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5347-5348 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Penning ionization electron spectra are reported at five collision energies E in the range 1.6–4.9 kcal/mol. A preliminary analysis of the E dependence of the intensities, shapes, and positions of the vibronic lines reveals details of the ionization dynamics, features of the highly anisotropic potential surface, and connections with N2 orbital structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459655
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  • 10
    Electronic Resource
    Electronic Resource
    Collision energy dependence of product branching in Penning ionization: He*(2 1S, 2 3S) + H2, D2, and HD (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1564-1576 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Relative ionization cross sections for the title systems with articulation of all product ion channels have been measured in the collision energy range 1.5–4.0 kcal/mol using crossed supersonic molecular beams; the H2 results have been extended down to 0.5 kcal/mol by the use of a 10% H2/Ar seeded beam. The data are interpreted with a microscopic two-step model that assumes ionization near the turning point in the excited state, a centrifugal barrier criterion for ionic complex formation, and statistical partitioning of flux among the possible ionic products, i.e., phase-space theory. A full statistical calculation underestimates the amount of rearrangement ionization He*+H2→HeH++H+e− by a factor of 2, but one which excludes antiparallel coupling of orbital and rotational angular momenta in the H+2 channel is in better accord with the data. A substantial isotope effect favoring HeD+ over HeH+ in the HD reactions by a factor of 1.9±0.2 is well represented by the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456049
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