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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 52 (1991), S. 84-89 
    ISSN: 1432-0649
    Keywords: 36.40 ; 42.65 ; 47.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coherent Stokes and anti-Stokes Raman scattering CSRS and CARS have been employed to study the spectroscopy of nitrogen molecules and clusters in the expansion of a supersonic jet. In the vibrational spectrum, at strong stagnation conditions, an intense redshifted peak is observed which can be assigned to the intramolecular vibrations in large N2 clusters having adopted the β-phase structure. Another weak feature is assigned to nitrogen clusters in the α-phase. In the rotational region of the spectrum only monomer features have been observed. The failing to observe librational motions is consistent with the finding that the nitrogen clusters are predominantly in the orientationally unordered β-phase. The low rotational temperature suggests supercooling of the β-phase.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5826-5834 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6276-6283 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ethylene clusters (C2H4)n are generated in a supersonic expansion with He and size selected by scattering from a helium beam. The clusters are dissociated upon absorption of a photon from a pulsed CO2 laser by exciting the ν7 mode of the monomer. During the collision about 30 meV of internal energy is transferred to the cluster so that the laser photons interact with internally hot clusters. The frequency and fluence dependences of the photodissociation cross sections are measured for (C2H4)n with n=2,3,4,5, and 6. Nearly all spectra exhibit structure which is most pronounced for the dimer. The overall width (FWHM) decreases from 31.2 cm−1 for the dimer to 12.2 cm−1 for the hexamer, while the maximum position is nearly the same (951.6 cm−1). The structure of the dimer spectrum is attributed to hot bands. The large linewidth corresponds to a short lifetime in the ps range.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 6579-6584 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Iron clusters have been produced by CO2-laser-induced decomposition of iron pentacarbonyl in a flow reactor. The absorption of CO2 laser photons was achieved by using SF6 as a sensitizer. By adding an oxidizing gas, N2O, or a hydrocarbon, C2H4, molecules which are also dissociated in the laser field, the iron clusters may react with several radicals. The as-synthesized species are extracted from the reaction zone by a conical nozzle and expanded into the source chamber of a cluster beam apparatus where they are analyzed with a time-of-flight mass spectrometer. In the experiment with N2O, we observe a magic peak at m=856 amu which can be readily assigned to the particularly stable Fe13O8 cluster. If C2H4 is added to the reactant gas, the mass spectrum reveals a magic peak at mass m=884 amu. Using deuterated ethylene, the magic peak shifts by 12 amu to larger masses, indicating that the magic cluster contains 12 hydrogen atoms. With the given restrictions, we readily derive the molecular formula Fe13C12H12. Chemical stability and symmetry considerations suggest that the detailed chemical formula of the magic cluster is Fe13(C2H2)6 and that its structure corresponds to a Fe13 icosahedron with six HC(Double Bond)CH or C(Double Bond)CH2 groups bound to six pairs of the 12 iron surface atoms. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 123 (1986), S. 99-101 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 144 (1988), S. 391-395 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 101 (1983), S. 126-130 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 180 (1991), S. 332-338 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 169 (1990), S. 198-203 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5302-5306 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon clusters have been generated by CO2-laser-induced decomposition of SiH4 in a flow reactor. By introducing a conical nozzle into the reaction zone, they are extracted into a molecular beam apparatus and analyzed with a time-of-flight mass spectrometer. The mass spectra show that the cluster source emits, besides small clusters, also nanosized species containing around 103 atoms. These clusters were deposited on silicon and sapphire targets at room temperature. The deposited films have been analyzed with a Raman spectrometer and with a field emission scanning electron microscope (FE-SEM). The Raman spectra reveal a broad amorphouslike band and a relatively sharp peak at 518.1 cm−1. Interpretation of the sharp Raman feature, based on the phonon confinement model, suggests the presence of silicon nanocrystallites in the deposited films with a particle size of about 3–3.6 nm in diameter. The FE-SEM micrographs show an agglomerate of spherical particles of 3–12 nm in diameter, with a pronounced maximum in the size distribution at around 3.5 nm. The various methods of characterization allow us to conclude that the size of the nanoclusters is largely preserved if they are deposited on the substrate. Therefore, the technique presented here might be an efficient means to produce silicon quantum dots of about 3 nm in diameter. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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