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  • 1
    Electronic Resource
    Electronic Resource
    CO2-laser induced photodissociation studies of size-selected small benzene clusters (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5826-5834 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The infrared photodissociation of size-selected, small benzene clusters has been investigated in the region of the ν18 CH in-plane bend using a pulsed CO2 laser. By scattering the cluster beam with a secondary Ne beam and observing off-axis the effect of the laser irradiation with a rotatable mass spectrometer, cluster-specific spectroscopy is performed. The dependence of IR absorption and subsequent dissociation of (C6H6)n clusters has been investigated as a function of laser frequency and laser fluence for n=2, 3, and 4. The absorption profiles are structureless and show only little variation with cluster size. If, instead of He, Ne is used as carrier gas, the absorption profiles are distinctively narrower. This effect is attributed to a lower internal temperature achieved with Ne. In contrast to the benzene dimer and tetramer, the fluence dependence for the trimer dissociation is stronger than linear suggesting that more than one photon is needed to dissociate this cluster. In a computational approach, the structures of the benzene dimer, trimer, and tetramer have been calculated employing an energy minimization program. For the trimer a cyclic ring structure is determined. The computational results are in perfect agreement with the experimental findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458403
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  • 2
    Electronic Resource
    Electronic Resource
    The excited states of barrelene: An absorption and magnetic circular dichroism study in the gas phase (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4153-4157 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The absorption and magnetic circular dichroism (MCD) spectra of barrelene in the gas phase have been investigated in the wavelength region of 2600–1500 A(ring). The 3s, 3p, and 3d Rydberg transitions have been identified and assigned. A strong valence band is observed at 1780 A(ring) and is assigned as a 1A'1→1A‘2 transition in accordance with theoretical predictions. The vibrational structure and the intensity distribution of the vibrational progressions indicate that only minor conformational changes occur in the excited electronic states of barrelene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453822
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  • 3
    Electronic Resource
    Electronic Resource
    The structures of small methyl fluoride clusters from infrared dissociation experiments (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3021-3028 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular beam depletion spectroscopy has been employed to study the dissociation of small methyl fluoride clusters upon excitation of the ν3 C–F stretch vibration at 1048.6 cm−1. Size selection has been achieved by dispersing the (CH3F)n cluster beam by a secondary rare gas beam. For the methyl fluoride dimer only very weak dissociation signals could be observed. The corresponding spectrum features a single, 13.4 cm−1 broad absorption line. This observation is explained with a symmetric dimer structure, in which both monomer units reside at equivalent positions, and an inefficient coupling of the molecular vibration to the intermolecular bond. For the trimer and tetramer very strong dissociation yields are observed. Whereas the trimer shows a complicated spectrum which is attributed to its nonsymmetric structure, the tetramer spectrum is again characterized by a single peak. In order to obtain supplementary information, dissociation spectra have also been measured for small methyl fluoride clusters residing inside or on the surface of large Arx host clusters. These matrixlike spectra are consistent with the free gas-phase cluster data. Finally, in a computational approach, the structures of the methyl fluoride dimer, trimer, and tetramer have been determined by total energy minimization. The theoretical results are in perfect agreement with the experimental findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463043
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  • 4
    Electronic Resource
    Electronic Resource
    Wavelength dependence of the photochemistry of O2 on Pd(111) and the role of hot electron cascades (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 682-694 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photochemistry of O2 adsorbed on Pd(111) has been studied as a function of the energy of the exciting photons in the range of hν=3.9–6.4 eV. The obtained data are reproduced by a proposed kinetic model considering photostimulated desorption and dissociation, whereby the latter gives rise to additional displacement processes. This modeling yields rate constants and, hence, cross sections for the respective processes. It is found that the cross sections for all processes rise exponentially with photon energy. This result motivates a study of the distribution of hot electrons generated by laser irradiation, and its decay via electron-hole pair scattering events resulting in a broad secondary electron distribution. The energetic and spatial distribution of these electrons is calculated. The probability for these electrons to tunnel into an adsorbate affinity level is modeled and compared to the observed photo cross sections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465741
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