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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 114 (1992), S. 3207-3210 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    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 90 (1989), S. 2027-2034 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Angular distributions of Rh atoms desorbed by energetic ion bombardment of an oxygen covered Rh{111} surface are measured accurately using a multiphoton resonance ionization (MPRI) detection technique. The results, in conjunction with molecular dynamics calculations of the ion impact event show that these distributions reflect the near-surface crystal structure. The molecular dynamics calculations were performed using a many-body embedded-atom potential to describe the dynamics of the Rh atoms and a pair-wise additive potential to describe the oxygen–Rh interactions. Several oxygen overlayer structures were considered for molecular dynamics modeling of the desorption process, including p(2×2) overlayers with a coverage of 0.25 monolayer (ML), and p(2×1) overlayers with a coverage of 0.50 ML, both of which are consistent with low energy electron diffraction (LEED) data. Three different adsorption sites were tested: threefold symmetric sites over second layer Rh atoms, threefold symmetric sites over third layer Rh atoms, and atop sites. The calculated azimuthal angular distributions of desorbed Rh atoms for each of these cases are unique, matching the experimental data best in the case of a p(2×1) overlayer with oxygen atoms adsorbed in threefold symmetric sites over third layer Rh atoms. The calculated Rh atom desorption yield (ejected atoms per incident ion) is sensitive to the oxygen coverage in the range 0.25–0.50 ML. These calculations are important in developing a surface bonding site and coverage consistent with LEED and our experiments. The peak in energy distribution of ejected Rh atoms from the oxygen covered surface is at a lower energy value than that of the clean metal. This indicates that collisional energy loss processes contribute to determining the peak position as well as the well known binding energy effect.
    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 89 (1988), S. 2539-2543 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The surface structure of single crystal metals in reflected in the angular distributions of neutral atoms desorbed during keV Ar ion bombardment. Results are presented here of a study of desorption from a stepped surface, Rh{331}. Recently, classical dynamics simulations of the desorption process were shown to give excellent agreement with ejection data from Rh{111}, and the same model potential has been used to simulate desorption from Rh{331}. The agreement with experiment remains excellent despite the different coordination of the surface atoms on Rh{111} and Rh{331}. The azimuthal ejection distributions are strongly affected by the steps.
    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 83 (1985), S. 1392-1403 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical description of near-resonant charge-exchange processes occurring in gas–surface collisions is presented. The diatomics in molecules method is used for the electronic description of a surface consisting of five atoms. The gas–surface interaction potentials and couplings are obtained with the polyatomics in molecules approach. Trajectories for the "nuclear'' variables and transition probabilities are calculated with the common eikonal formalism. Preliminary results are presented for Na scattering from a W(110) surface. The initial kinetic energy of the sodium atom is varied between 5 and 60 eV and its trajectory is restricted to be perpendicular to the surface and striking the center W atom. The results show a noticeable probability (≤20%) for electron transfer to the surface.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6226-6232 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The energy-resolved angular distributions of Rh atoms ejected from Rh {001} by bombardment with 5.0 keV Ar+ ions have been measured for the ground state (a 4F9/2) and the two lowest lying excited state (a 4F7/2,a 4F5/2). Simultaneous measurements on these electronic states provide us an opportunity to examine the influence of electronic interactions on desorbed particles. The experimental results show that there is a sequential variation in the angular distributions as the excitation energy increases. These variations are attributed to the interaction between the substrate electrons and the excited state atom as it is being ejected from the surface. Since the measurements are performed using multiphoton ionization via a single intermediate state, the population partition among the three lowest states is obtained as well. The excitation probabilities of the a 4F7/2 and a 4F5/2 states are compared with those predicted from the expression exp(−A/av⊥) and with a recently proposed model involving interatomic collisions above the surface. Results suggest that atoms excited via this mechanism make a significant contribution to the population of atoms ejected with low ejection velocities for the first-excited a 4F7/2 state (0.19 eV), as reported previously. Moreover, we suggest that an even higher proportion of atoms in the a 4F5/2 state are produced via this mechanism.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8557-8557 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 46 (1995), S. 373-396 
    ISSN: 0066-426X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 5999-6007 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report on a molecular dynamics simulation of cluster emission during sputtering of metals using a new many-body potential developed by DePristo and co-workers. For the specific case of silver as a sample target material, it is shown that this potential allows a much more realistic description of small clusters than the EAM potential used in our previous work. While this has a relatively large effect on the relative abundance of clusters within the total flux of sputtered material, other cluster properties like kinetic energy distributions and internal excitation are found to be less affected. By comparison with corresponding experimental data, we conclude that the formation of sputtered silver clusters can now be almost quantitatively modeled by the simulation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5997-6008 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time dependent Monte Carlo (TDMC) simulations are performed on a diamond lattice to determine the effect of surface properties/conditions on the growth of diamond thin films on flat and stepped diamond {001}(2×1):H surfaces under chemical vapor deposition conditions. The gas–surface interface consists of reactions of incoming gas-phase species, such as H2 molecules and H and CH3 radicals with surface radical, π-bond and step edge sites on the diamond {001}(2×1):H surface. The rates and probabilities of adsorption, abstraction, desorption, and incorporation reactions, as well as the reverse reactions, are explicitly calculated either via molecular dynamics or transition state theory methods, or taken from experimental measurements. The TDMC method allows all these reactions to occur simultaneously, though probabilistically, at each time step. The microscopic and macroscopic characteristics of the growing film are observed as functions of time. Diamond films of 10∼100 layers are grown in the simulation and the observed growth rate (∼0.5μm/h at 1200 K) is in agreement with experimental results. The contributions to the activation energy of growth by specific processes such as H abstraction, CH3 adsorption and CH2 incorporation into the trough sites have been determined. The contributions to the activation energies by specific processes are not linearly additive, and the CH3 adsorption at step edges leads to enhanced growth at the edges. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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