Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 2000-2004  (7)
  • 1990-1994  (30)
  • 1985-1989  (22)
  • 1965-1969  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Desorption of CO from Ru(001) induced by near-infrared femtosecond laser pulses (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9888-9897 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Irradiation of a Ru(001) surface covered with CO using intense femtosecond laser pulses (800 nm, 130 fs) leads to desorption of CO with a nonlinear dependence of the yield on the absorbed fluence (100–380 J/m2). Two-pulse correlation measurements reveal a response time of 20 ps (FWHM). The lack of an isotope effect together with the strong rise of the phonon temperature (2500 K) and the specific electronic structure of the adsorbate–substrate system strongly indicate that coupling to phonons is dominant. The experimental findings can be well reproduced within a friction-coupled heat bath model. Yet, pronounced dynamical cooling in desorption, found in the fluence-dependence of the translational energy, and in a non-Arrhenius behavior of the desorption probability reflect pronounced deviations from thermal equilibrium during desorption taking place on such a short time scale. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481626
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The interaction of cesium with oxygen (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2411-2422 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ultraviolet photoelectron spectroscopy (UPS) and electron spectroscopy by deexcitation of metastable noble gas atoms (MDS) were used to follow the continuous oxidation of Cs films. While UPS has a finite information depth, MDS probes only the properties of the outermost atomic layer. Small doses of O2 cause the formation of a "monolayer'' of Cs11O3 in which the O2− ions are incorporated below the surface, while the surface itself consists merely of metallic Cs atoms. Further uptake of oxygen leads to a continuous transformation of the subsurface layer into Cs2O2, while a small concentration of adsorbed O atoms builds up on the surface which act as nucleation centers for subsurface oxidation. Finally, the surface layer is completely oxidized into CsO2 which then retards further oxygen penetration into the bulk. The chemical state of the surface can be directly correlated with the associated change of the work function. A monolayer of Cs adsorbed on a Cu(110) surface exhibits quite different properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452089
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Kinetic oscillations in the catalytic CO oxidation on Pt(100): Computer simulations (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5328-5336 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The previously observed phenomena of temporal and spatial self-organization during the catalytic oxidation of CO on a Pt(100) surface were computer simulated by use of the cellular automaton technique. The underlying model is footed on the knowledge about the individual reaction steps (adsorption, desorption, surface structural transformation, etc.), which in turn formed the basis of a previous theoretical treatment in terms of the formulation and solution of a set of coupled differential equations. The present result nicely show the formation and propagation of two-dimensional patterns, and they reproduce qualitatively well all the experimental observations. The development of macroscopic patterns even with an a priori perfectly homogeneous surface is a particularly interesting effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451676
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Rotational state distributions of NO molecules after interaction with germanium surfaces (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 4800-4807 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational state distributions of NO molecules scattered at clean and oxidized Ge surfaces were determined by means of laser induced fluorescence (LIF). For low incident kinetic energies (Ekin(approximately-less-than)200 meV) scattering is dominated by trapping/desorption and the molecules coming off the surface are translationally accommodated to the surface temperature. The rotational state populations can in this case be approximated by a Boltzmann distribution. The rotational temperature Trot equals the surface temperature Ts, however only up to about 250 K. Further increase of Ts leads to a leveling off of Trot until a limiting value Trot,lim(approximate)400 K is reached. (Rotational cooling in desorption.) At higher kinetic energies direct-inelastic scattering dominates, and for Ekin=820 meV a pronounced non-Boltzmann distribution (rotational rainbow) is observed. The observed effects are qualitatively interpreted in terms of current theoretical models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449006
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Adsorption geometry of hydrogen on Fe(110) (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 1959-1968 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: From an analysis of the low-energy electron diffraction (LEED) intensities we have determined the adsorption geometry of the two ordered H adlayers formed at T〈270 K on Fe (110): a (2×1) and a (3×1) structure, with ideal coverages of θ= 1/2 and θ= (2)/(3) . Calculations were performed for different adsorption sites and structural models, taking the Fe–H bond length and the first Fe–Fe interlayer spacing as variable parameters. An R factor analysis was used for quantitative comparison with the experimental data. In both structures the H atoms are adsorbed on highly coordinated (i.e., quasithreefold) sites: The R factors of only the superlattice beams (RZanazzi–Jona=0.26, RPendry=0.55 in the (2×1) and RZJ=0.4, RP=0.58 in the (3×1) structure) are significantly lower than those from models with a long bridge adsorption site (RZJ=0.37, RP=0.66 and RZJ=0.6, RP=0.74). The on top site and the short bridge site can clearly be ruled out. For both structures the minima occur at the same Fe–H interlayer spacing of 0.9±0.1 A(ring), equivalent to an Fe–H distance of 1.75±0.05 A(ring) or rH=0.47±0.05 A(ring). From the R factor minimum of all beams(RZJ=0.23, RP=0.46) the first Fe–Fe interlayer spacing is found to be equal to its bulk value, like on the clean surface. In the (2×1) structure the only possible arrangement of the Had atoms consists of dense packed rows in [001] direction which are separated by a row of unoccupied sites, respectively, due to a delocalization of the H atoms over two neighboring threefold sites, short-range fluctuations can be envisaged. Their influence upon I/V curves and relative intensities of different superlattice beams was analyzed. As a result this effect could be excluded, large domains are required, in which only one type of threefold sites is occupied. For the (3×1) structure a model is favored in which the lateral distribution of the adatoms differs from a previous suggestion. It is shown that this model is more plausible in view of the H–H interactions. The higher density of threefold sites also has implications for the discussion of the 2D phase diagram of H/Fe (110), especially on the requirement of trio interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449334
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Reaction fronts in the oxidation of hydrogen on Pt(111): Scanning tunneling microscopy experiments and reaction–diffusion modeling (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 5759-5773 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Traveling reaction fronts in the oxidation of hydrogen on a Pt(111) surface were investigated by means of scanning tunneling microscopy (STM). The fronts were observed during dosing of the oxygen covered surface with hydrogen at temperatures below 170 K. The fronts represented 10 to 100 nm wide OH-covered regions, separating unreacted O atoms from the reaction product H2O. O atoms were transformed into H2O by the motion of the OH zone. Small scale STM data showed the processes within the fronts on the atomic scale. Experiments on larger scale revealed the velocity and the width of the fronts as a function of temperature. A simple reaction–diffusion model has been constructed, which contains two reaction steps and the surface diffusion of water molecules, and qualitatively reproduces the experimental observations. A lower bound for the front velocity was also derived analytically. For a quantitative comparison between experiment and theory the rate constants of the two reaction steps and the diffusion coefficient of H2O were determined by STM and low energy electron diffraction experiments. With these parameters, the front velocities predicted by the model are approximately one order of magnitude smaller than those determined by STM. The predicted front widths are, depending on the temperature, between two and three orders of magnitude larger than the experimental values. We conclude that these deviations result from the inability of the reaction–diffusion system to describe the complex chemical processes and structure changes within the fronts. The atomically resolved STM data indicate attractive interactions between the particles that in particular affect the diffusion of the H2O molecules. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1453964
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The oxidation of CO on RuO2(110) at room temperature (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 10058-10062 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: RuO2(110) surfaces were prepared by exposing Ru(0001) to 107 L of O2 at 700 K. Postexposure of O2 at 300 K resulted in an additional oxygen species (O-cus) adsorbed on coordinatively unsaturated Ru atoms (Ru-cus). The surface was then exposed to CO at 300 K and studied by thermal desorption spectroscopy (TDS) and high-resolution electron energy loss spectroscopy (HREELS). It is demonstrated that CO is oxidized at 300 K through reaction with both the O-cus as well as with surface O-atoms held in bridge positions (O-bridge). Although—at room temperature—CO adsorbs intermediately on the Ru-cus atoms, it is stable only at the Ru atoms underneath the O-bridge after the latter has been reacted off. At room temperature only surface oxygen takes part in the CO oxidation and the oxygen-depleted surface can be restored by O2 exposure, so that under steady-state flow conditions an oxygen-deficient surface will exist whose stoichiometry will be determined by the ratio of partial pressures. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1350817
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    LEED structure analysis of the clean and (2×1)H covered Pd(110) surface (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6191-6198 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: From an analysis of the low-energy electron diffraction (LEED) intensities we have determined the oscillatory distortion of the topmost interlayer spacings of the clean and the (2×1)H covered Pd(110) surface as well as the exact adsorption geometry in this latter structure, which is formed at T〈180 K at a coverage of θH≤1.0. An R-factor analysis was used for quantitative comparison with the experimental data. The oscillatory distortion of the clean surface— d12=−5.1±1.5%, d23=+2.9±1.5%, d34 at its bulk value of 1.37 A(ring) (with R factors RP=0.22 , RZJ=0.14 )— is found to be reduced by the H adlayer to d12=−2.2±1.5%, d23=+2.9±1.5%, and d34=bulk value. The H atoms are adsorbed on quasi-threefold sites with equal distances of 2.0±0.1 A(ring) to the two nearest Pd neighbors in the topmost and the closest Pd atom in the second layer, leading to an effective radius of the H atom of rH=0.6±0.1 A(ring). The long-bridge adsorption site, (octahedral) subsurface sites, or a hydrogen induced reconstruction via a lateral displacement of topmost Pd atoms by more than ±0.1 A(ring) can clearly be ruled out. These structural data, which are in good agreement with those of ordered Had structures on Ni(110) and Fe(110), characterize the (2×1)H structure on Pd(110) as being a typical adsorbate structure. There is no indication of either direct occupation of distinct subsurface or of near surface adsorption sites in this structure, nor does it open up channels for surface penetration, e.g., by a strong distortion of the topmost Pd substrate layers. In contrast to Ni(110) and Rh(110) the island growth of the (2×1)H structure on Pd(110) indicates predominantly attractive, indirect adatom–adatom interaction which, however, are of distinctly different nature than those causing island formation in the Pd–hydride phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453495
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Kinetic oscillations in the catalytic CO oxidation on Pt(100): Periodic perturbations (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 742-749 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Periodic modulations of oxygen pressure or temperature were applied in the catalytic oxidation of CO on a Pt(100) surface under isothermal, low pressure conditions. Transitions from aperiodic autonomous oscillations to regular phase-locked behavior could be observed. Computer simulations using a stochastic cellular automaton model yielded qualitatively similar results. The spatial distribution in both experiment and simulation varies essentially in phase over the whole surface area under the influence of the periodic perturbation, while wave propagation in the autonomous system causes more irregular overall behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453572
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Kinetic oscillations in the catalytic CO oxidation on Pt(100): Experiments (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 3519-3534 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Under properly chosen conditions the rate of catalytic CO oxidation at a clean and well-defined Pt(100) surface exhibits sustained temporal oscillations which are also reflected by periodic changes of the work function (Δcursive-phi). These oscillations are associated with periodic changes of the surface structure between the CO-covered (θCO =0.5) 1×1–c(2×2) phase and an oxygen adlayer, respectively the reconstructed hex phase, as demonstrated by LEED. Laterally resolved experiments revealed that the surface phase transformations propagate in the form of trigger waves across the whole surface area. On the basis of detailed experiments and of literature data on the adsorptive properties of the two surface modifications of Pt(100) a microscopic picture on the mechanism of the observed phenomena is developed which also underlies a recently performed theoretical treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450238
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...