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  • 1
    Electronic Resource
    Electronic Resource
    Arteether, a new antimalarial drug: synthesis and antimalarial properties (1988)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 31 (1988), S. 645-650 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00398a026
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  • 2
    Electronic Resource
    Electronic Resource
    CO product distribution from metastable levels of HCO X˜ 2A' prepared by stimulated emission pumping (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 5095-5098 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational and rotational distributions have been measured for the CO produced following dissociation of HCO prepared in metastable ground-state levels by stimulated emission pumping. The metastable levels are characterized by high vibrational excitation in the HC–O stretching coordinate. The CO (v=2) rotational distribution following dumping of population on the QR0(5) transition to the (0, 7, 0) level is rotationally cold and its distribution is in very good agreement with the theoretical prediction by Dixon. The linewidths for stimulated emission pumping transitions to the (0, 7, 0) and (0, 8, 0) levels are 1.0 and 1.6 cm−1, respectively. Since it is possible to prepare a wide variety of metastable HCO levels whose wave functions sample different regions of the HCO potential energy surface, measurement of the dissociation dynamics of HCO so prepared should provide a detailed picture of the potential surface at energies from 0–10 000 cm−1 above the dissociation limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464966
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  • 3
    Electronic Resource
    Electronic Resource
    Unimolecular dissociation of hydrogen peroxide from single rovibrational states near threshold (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 889-898 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared-optical double resonance excitation of hydrogen peroxide using the ν3+ν5 and ν2 + ν5 combination bands as intermediate levels prepares reactant molecules in single rotational states near the OO dissociation threshold. The band origins of the ΔvOH = 4 vibrational overtone transitions originating from these combination bands provide information on the anharmonicities between the OH stretch and the OO stretch and OOH bend, respectively. At low resolution the vibrational overtone transitions are clearly parallel bands of a near prolate symmetric top and can be assigned to zeroth-order J and K quantum numbers. At 0.1 cm−1 resolution the individual features in the vibrational overtone spectra appear as clumps of sharp lines centered at the frequencies of the zeroth-order symmetric top transitions. The number of components within a clump appears to be less than the total number of available vibrational states. The narrowest feature observed has a linewidth of 0.12 cm−1 and sets a lower bound of ∼35 ps on the lifetime of the dissociating molecule. As J increases from 1 to 21, the clumps of lines coalesce into a smooth Lorentzian envelope. The overall clump width decreases with J, reaching an asymptotic value of 0.67 cm−1 at J(approximately-equal-to)17. A model incorporating a J dependent density of bath levels that couple to the zeroth-order bright state predicts the observed changes in the vibrational overtone transitions with J. The rotationally resolved vibrational overtone spectra provide information on the time scale for the conservation of K of the dissociating molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459979
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  • 4
    Electronic Resource
    Electronic Resource
    Broad vibrational overtone linewidths in the 7νOH band of rotationally selected NH2OH (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 9194-9196 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared–optical double-resonance spectroscopy of the 7νOH vibrational overtone level of NH2OH reveals 14 cm−1 wide spectral features. The product state distribution of the OH fragment subsequent to overtone excitation indicates that the 7νOH level of NH2OH is ∼128 cm−1 above the N–O bond dissociation energy. Comparison to HOOH overtone spectra at a similar excess energy suggests that the broad NH2OH linewidths result from vibrational state mixing at the 7νOH level and not from inhomogeneous structure or lifetime broadening of the dissociating molecules. The observation of 14 cm−1 overtone linewidths for a molecule the size of NH2OH suggests that the broad vibrational overtone transition linewidths in larger polyatomics may contain a substantial homogeneous component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459210
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  • 5
    Electronic Resource
    Electronic Resource
    Product energy partitioning in the unimolecular decomposition of vibrationally and rotationally state-selected hydrogen peroxide (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5129-5136 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared-optical double resonance prepares HOOH molecules in single rotational levels of the 6νOH, 5νOH+νOOH, 5νOH+νOO, and 4νOH+νOH' vibrational states which range from 3 to 2287 cm−1 of excess energy above the unimolecular dissociation threshold. Laser-induced fluorescence probes the nascent OH rotational state distributions from the decomposition of rovibrationally selected reactants. The nascent rotational state distributions reveal that both OH spin–orbit states can be populated by the decomposition of a single molecule and hence that electronic angular momentum is not conserved throughout the dissociation process. The product state distributions from reactants excited to the 6νOH and 4νOH+νOH' vibrational levels are generally in good agreement with the predictions of phase-space theory provided electronic angular momentum is treated statistically. Reactants decomposing from single rotational states in the 5νOH+νOOH combination level (and to a lesser extent the 5νOH+νOO level) show product state distributions which are systematically colder than phase-space theory predictions. This observation indicates that energy redistribution in vibrationally excited HOOH is not complete on the time scale of unimolecular decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462894
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  • 6
    Electronic Resource
    Electronic Resource
    Rotationally resolved vibrational overtone spectroscopy of hydrogen peroxide at chemically significant energies (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8620-8633 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An infrared–optical double resonance scheme simplifies the room temperature 6νOH vibrational overtone spectrum of hydrogen peroxide and prepares highly excited reactant molecules in single rotational states for unimolecular reaction studies. First, an optical parametric oscillator excites the OH asymmetric stretch (ν5) and selects a single or small subset of rotational states. A visible dye laser pulse then promotes molecules from vOH=1 to vOH=6 where they subsequently dissociate to produce two OH fragments. A third laser detects the dissociation products via laser induced fluorescence. The rotationally resolved vibrational overtone spectra of hydrogen peroxide generated by scanning the visible dye laser frequency are assignable to a parallel band of a near prolate symmetric top. Linewidths of the individual rovibrational features range from 1–3 cm−1 but show no systematic dependence upon the rotational quantum numbers and are attributed predominantly to anharmonic coupling of the zeroth-order bright state to dark background states. The assignability of the double-resonance vibrational overtone spectra to J and K quantum numbers implies that K is conserved for at least a time determined by the linewidth of a single zeroth-order rovibrational feature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459249
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  • 7
    Electronic Resource
    Electronic Resource
    Vibrational overtone spectroscopy of the 4νOH+νOH' combination level of HOOH via sequential local mode–local mode excitation (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5659-5667 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Sequential pumping of the local OH stretch vibrations in hydrogen peroxide using infrared-optical double resonance permits spectroscopic access to the 4νOH+νOH' combination level. Analysis of the rotationally resolved vibrational overtone spectra generated by this technique determines approximate rotational constants for this level and a value of 17 051.8±3.4 cm−1 for the O–O bond dissociation energy. The linewidths of individual zeroth-order rotational transitions increase sharply with increasing K and change from smooth Lorentzian profiles to clumps of individual lines. The K dependence of the clump widths suggests that an a-axis Coriolis interaction is the primary coupling mechanism between the zeroth-order bright state and dark bath states. As a function of increasing J, each clump coalesces into a smooth Lorentzian profile. We interpret this J dependence in terms of a model that includes rotationally induced vibrational coupling among zeroth-order dark states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462665
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  • 8
    Electronic Resource
    Electronic Resource
    A new technique for state-to-state studies of unimolecular reactions (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4448-4450 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A double-resonance technique which combines infrared excitation of a fundamental vibration of a light atom oscillator with vibrational overtone excitation of that same oscillator selectively prepares molecules in individual quasibound vibrational–rotational states at energies above their dissociation threshold. A third laser probes individual states of the product fragments via laser induced fluorescence. We present our initial results applying this technique to study the 6νOH vibrational overtone spectroscopy and unimolecular dissociation dynamics of hydrogen peroxide (HOOH). The double-resonance approach simplifies the congested vibrational overtone spectrum of HOOH, and the linewidth of resolved features places a lower limit on the lifetime of approximately 7 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454782
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  • 9
    Electronic Resource
    Electronic Resource
    Photoluminescence properties of a GaN0.015As0.985/GaAs single quantum well under short pulse excitation (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 958-960 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Under short pulse laser excitation, we have observed an extra high-energy photoluminescence (PL) emission from GaNAs/GaAs single quantum wells (QWs). It dominates the PL spectra under high excitation and/or at high temperature. By measuring the PL dependence on both temperature and excitation power and by analyzing the time-resolved PL results, we have attributed the PL peak to the recombination of delocalized excitons in QWs. Furthermore, a competition process between localized and delocalized excitons is observed in the temperature-dependent PL spectra under the short pulse excitation. This competition is believed to be responsible for the temperature-induced S-shaped PL shift often observed in the disordered alloy semiconductor system under continuous-wave excitation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1390484
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  • 10
    Electronic Resource
    Electronic Resource
    Interband luminescence and absorption of GaNAs/GaAs single-quantum-well structures (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2862-2864 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the interband electron transitions in a GaNAs/GaAs single quantum well (QW) by photoluminescence and absorption spectra. The experimental results show that the dominant photoluminescence at low temperature and high excitation intensity originates from transitions within the GaNAs layer. The interband transition energy for QWs with different well widths can be well fitted if a type-II band line up of GaNAs/GaAs QWs is assumed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126498
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