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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7995-8012 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the desorption of Na atoms from large Na clusters deposited on dielectric surfaces. High-resolution translational energy distributions of the desorbing atoms are determined by three independent methods, two-photon laser-induced fluorescence, as well as single-photon and resonance-enhanced two-photon ionization techniques. Upon variation of surface temperature and for different substrates (mica vs lithium fluoride) clear non-Maxwellian time-of-flight distributions are observed with a cos2 θ angular dependence and most probable kinetic energies below that expected of atoms desorbing from a surface at thermal equilibrium. The half-width of the time-of-flight distribution decreases with increasing surface temperature. A quantitative description of the energy and angular distributions is presented in terms of a model which assumes that following the initial surface plasmon excitation neutral atoms are scattered by surface vibrations. Recent experiments providing time constants for the decay of the optical excitations in the clusters support this model. The excellent agreement between experiment and theory indicates the importance of both absorption of the laser photons via direct excitation of surface plasmons as well as energy transfer with the substrate during the desorption process. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 65 (1997), S. 375-377 
    ISSN: 1432-0630
    Keywords: PACS: 61.14.Hg; 61.65.+d; 68.55.Ce; 68.55.Jk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 3 (CH2)9]SH) have been adsorbed on Au(111) single crystals both via vacuum deposition and from an ethanolic solution. The epitaxial structure of the ultrathin organic films has been identified at room temperature via low-energy electron diffraction to be c(4 $\sqrt{3}$ ×2 $\sqrt{3}$ )R30° for the solution grown film and rectangular c(23× $\sqrt{3}$ ) for the vacuum deposited film. These structures correspond to molecules adsorbed on the surface with their carbon chains flat on the surface (vacuum deposited) and nearly perpendicular (solution grown). It is demonstrated that this orientation can be changed reversibly in vacuum via either annealing the films or exposing them to additional gas.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0649
    Keywords: PACS: 32.30.Jc; 32.80.Wr; 42.65.-k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 3 PJ) oxygen atoms are detected in a high pressure surface wave discharge driven at 2.45 GHz via two-photon resonant degenerate four-wave mixing spectroscopy (TP-DFWM) in the forward folded BOX configuration. The nonlinear optical signal provides a direct measure of the relative oxygen atom concentration with high spatial resolution inside the discharge up to pressures of 1 bar and without distortions due to linear absorption or saturation effects. The axial distribution of oxygen atom concentration is observed to depend sensitively on total pressure and gas flux. For total gas pressures up to 600 mbar both in case of a mixture of 10% O2/He and 10% O2/Ar the concentration of oxygen atoms increases linearly with pressure. At higher pressures an increase with larger slope is observed for 10% O2/Ar, while the concentration remains constant for 10% O2/He. This is interpreted by an increase of the three-body recombination rate in O2/He mixtures.
    Type of Medium: Electronic Resource
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