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Showing papers by "Fritz Haber Institute of the Max Planck Society published in 1988"



Journal ArticleDOI
TL;DR: Improvements in technique have produced electron micrographs of purple membrane that provide reproducibly measurable diffraction peaks extending to 2.8 A (1 A = 0.1 nm) and enabled the calculation of a directly phased projection map at 2.

138 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that at the metal-electrolyte interface an Au(100)−(1×1) surface can reconstruct already at room temperature into its hexagonal (5×20) form, when a negative potential is applied.

121 citations


Journal ArticleDOI
TL;DR: In this article, the integral LEED spots from a Pt(110) surface were found to continuously split and broaden during catalytic oxidation of carbon monoxide if the conditions were adjusted in a way that the 1×2 reconstruction of the surface was lifted by adsorbed CO.

104 citations


Journal ArticleDOI
TL;DR: Highly active, monomeric and dimeric Photosystem II complexes were purified from the thermophilic cyanobacterium Synechococcus sp.

101 citations


Journal ArticleDOI
TL;DR: In this article, the isothermal catalytic oxidation of CO on a Pt(110) surface in a gradientless flow reactor at low pressure ( −4 Torr) exhibits under properly chosen conditions (P co, P o 2, T ) sustained temporal oscillations of the reaction rate as monitored through the variation of the work function Δφ.

94 citations


Journal ArticleDOI
TL;DR: In this paper, a simple mechanism for the kinetic oscillations is presented in which two opposing processes, the facet formation on a CO-covered 1 × 1 surface and the removal of facets by a thermal reordering process are causing kinetic oscillation through periodic changes in the surface structure.

94 citations


Journal ArticleDOI
TL;DR: The great success of the concept of a resonance in interpreting these experimental spectral features as obtained with the various spectro- scopies provides, in turn, strong support for the actual existence of a CO 2 derived resonance in these adsorption systems.
Abstract: The electronic spectra of CO chemisorbed on transition metals and copper as obtained with photoelectron spectroscopies, surface Penning spectroscopy, inverse photoemission spectroscopy, and x-ray absorption spectroscopy are discussed in regard to inherent features pointing to the existence of a CO 2${\ensuremath{\pi}}^{\mathrm{*}}$--derived resonance in these adsorption systems. Since the various spectroscopies probe the CO-metal systems predominantly in the excited final state, the spectra of one and the same line, however, are also affected by differences in the dynamic relaxation processes and nonequilibrium final-state charge configurations which are specific to each particular experimental method. In order to arrive at a unified interpretation of some seemingly controversial features in the electronic spectra of chemisorbed CO, we have invoked the notion of the CO 2${\ensuremath{\pi}}^{\mathrm{*}}$--derived resonance. Our model includes both initial-state chemical (i.e., backdonation-induced bonding) effects and final-state dynamical screening (relaxation) effects. Assuming a very small fractional occupation of the CO 2${\ensuremath{\pi}}^{\mathrm{*}}$ resonance in the case of weak chemisorption systems (e.g., CO/Cu), and notably larger occupation in the case of strong chemisorption (e.g., CO/Ni), it is possible to give a unified interpretation of the experimental features such as the threshold energies, level shifts, line shapes, etc., observed with CO adsorbed on transition metals and copper. The great success of the concept of a resonance in interpreting these experimental spectral features as obtained with the various spectro- scopies, provides, in turn, strong support for the actual existence of a CO 2${\ensuremath{\pi}}^{\mathrm{*}}$-- derived resonance in these adsorption systems.

91 citations


Journal ArticleDOI
TL;DR: In this article, the presence of reactive species in the gas phase, which approximates the on-stream situation, may affect the carbonization of the low-temperature coke.

90 citations


Journal ArticleDOI
TL;DR: In this article, the structural arrangement of the methoxy species (CH 3 O−) on Cu{100} has been investigated by photoelectron diffraction from the O ls and C ls levels, data being collected in the scanned energy mode for emission along the surface normal.

83 citations


Journal ArticleDOI
TL;DR: In this paper, a comparison between EPR and thermogravimetric measurements showed a good linear correlation between the number of radicals and the amount of coke formed at high temperature.

Journal ArticleDOI
TL;DR: Sare et al. as mentioned in this paper used three different techniques X-ray photoemission (XPS), near-edge Xray absorption spectroscopy (NEXAFS) and diffuse LEED to study the adsorption and reaction of CO, on Ni(ll0).

Journal ArticleDOI
TL;DR: In this paper, high-temperature coke develops under formation of alkylaromatics and subsequently small polyaromatic and/or polyphenylene molecules over dealuminated hydrogen mordenites.

Journal ArticleDOI
01 May 1988
TL;DR: In this article, the growth and dissolution of oxide layers on silicon has been studied under illumination and in the dark by analyzing current transients at different voltages in solutions of NH4F of various concentrations at pH values between 1 and 4.5.
Abstract: The growth and dissolution of oxide layers on silicon has been studied under illumination and in the dark by analyzing current transients at different voltages in solutions of NH4F of various concentrations at pH values between 1 and 4.5. When the oxidation rate of the silicon at high enough anodic bias and, for n-type specimens, high enough illumination intensity exceeds the rate of oxide dissolution in the fluoride, the film grows until it has reached a thickness where the dissolution is rate-determining for the net process. At higher voltages the current begins to oscillate. The data give some insight into the composition of the oxide layers and their electronic and ionic properties.

Journal ArticleDOI
TL;DR: In this paper, the behavior of electrodes coated with electronically insulating but permeable films is reviewed, focusing on films with ion-exchange properties, and the structure of the metal-film interphase, the film-solution interphase with its membrane equilibria, and transport processes across the films including the role of migration.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed thermal desorption spectra in terms of the Polanyi-Wigner equation and showed that lateral interactions between the adsorbates may lead to coverage (0) dependent preexponential factors.

Journal ArticleDOI
TL;DR: Using Fourier transform IR reflection-absorption spectroscopy, this paper detected the metal-carbon stretching mode of the "on-top" species in the adsorption system Pt{111}-CO.

Journal ArticleDOI
TL;DR: In this paper, photoemission spectra from potassium adsorbed on an Al{111} surface show a K $4s$-derived state just below the Fermi level, which is first observed just prior to the onset of ordering in the overlayer.
Abstract: Photoemission spectra from potassium adsorbed on an Al{111} surface show a K $4s$-derived state just below the Fermi level, ${E}_{F}$, which is first observed just prior to the onset of ordering in the overlayer. The feature disperses upwards with increasing ${\mathbf{k}}_{\ensuremath{\parallel}}$ and crosses ${E}_{F}$ before reaching the Brillouin-zone boundary. Its coverage dependence is indicative of a transition from strongly ionic to metallic bonding.

Journal ArticleDOI
01 Jan 1988-Zeolites
TL;DR: In this article, a mixture of solid alkaline chlorides MeCl (Me = Li, Na, K, Rb, Cs) and NH 4 -ZSM-5 or H-ZSM -5 react at elevated temperatures to evolve gaseous hydrogen chloride and form the respective cationic form of ZSM.

Journal ArticleDOI
TL;DR: In this paper, a reconstruction of the surface Cu layer on oxygen adsorption is presented, which implies a marked surface relaxation, and the distance in the nearest-neighbour O-Cu shell on the surface is considerably larger than the Cu-Cu separation in bulk copper and close to the corresponding value for Cu2O.

Journal ArticleDOI
01 Nov 1988
TL;DR: A survey of the various ways in which information on the structure of electrode surfaces and their influence on the electrochemical behavior, especially on adsorption reactions, can be found in this article.
Abstract: A survey is given of the various ways in which information on the structure of electrode surfaces and their influence on the electrochemical behavior, especially on adsorption reactions, can be obtained. The techniques now at hand include a wide variety of spectroscopic methods, which are applicable in-situ, such as reflectance spectroscopy over a broad range of photon energy, second harmonic generation, various X-ray diffraction techniques and, most recently, scanning tunneling microscopy, which highlights the possibility of acquiring atomic-scale resolution. In addition, the emersion of electrodes and their subsequent transfer into a vacuum chamber for detailed surface-structural studies, e.g., by electron diffraction methods, is now widely used in electrochemistry, since it has been shown that electrodes can, in fact, be emersed with their electric double layer apparently intact. The combined venture incorporating all these techniques should lead to a truly microscopic description of electrochemical processes. The way in which structural information, even on an atomic scale, can be derived, is illustrated here by a few selected examples.

Journal ArticleDOI
TL;DR: The structural differences between both the complexes of higher plants and cyanobacteria are discussed with special emphasis on their association with the antenna apparatus in the photosynthetic membranes.
Abstract: A photosystem II core complex was purified with high yield from spinach by solubilization with beta-dodecylmaltoside. The complex consisted of polypeptides with molecular mass 47, 43, 34, 31, 9 and 4 kDa and some minor components, as detected by silver-staining of polyacrylamide gels. There was no indication for the chlorophyll-a/b-binding, light-harvesting complex polypeptides. The core complex revealed electron-transfer activity (1,5-diphenylcarbazide----2,6-dichloroindophenol) of about 30 mumol reduced 2,6-dichloroindophenol/mg chlorophyll/h. The structural integrity was analyzed by electron microscopy. The detergent-solubilized protein complex has the shape of a triangular disk with a maximum diameter of 13 nm and a maximum height of 6.8 nm. The shape of this core complex differs considerably from that of cyanobacterial photosystem II membrane fragments, which are elongated particles. The structural differences between both the complexes of higher plants and cyanobacteria are discussed with special emphasis on their association with the antenna apparatus in the photosynthetic membranes.

Journal ArticleDOI
TL;DR: In this paper, the effects of the number of active sites and the pore volume of the zeolites on the initial rate of coke formation and the final coke level are studied.

Journal ArticleDOI
TL;DR: In this paper, a surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G molecules adsorbed at aggregated Ag colloids shows an absolute cross section of σSERRStotal = 2.3 × 10−16 cm2, which is nearly equal to the absorption cross-section of the same dye in solution.

Journal ArticleDOI
TL;DR: The structure of the ATP-synthase, F0F1, from spinach chloroplasts and beef heart mitochondria has been investigated by electron microscopy with negatively stained specimens.
Abstract: The structure of the ATP-synthase, F0F1, from spinach chloroplasts and beef heart mitochondria has been investigated by electron microscopy with negatively stained specimens. The detergent-solubilized ATP-synthase forms string-like structures in which the F0 parts are aggregated. In most cases, the F1 parts are arranged at alternating sides along the string. The F0 part has an approximate cylindrical shape with heights of 8.3 and 8.9 nm and diameters of 6.2 and 6.4 nm for the chloroplast and mitochondrial enzyme, respectively. The F1 parts are disk-like structures with a diameter of about 11.5 nm and a height of about 8.5 nm. The F1 parts are attached to the strings, composed of F0 parts, in most cases, with their smallest dimension parallel to the strings. The stalk connecting F0 and F1 has a length of 3.7 nm and 4.3 nm and a diameter of 2.7 nm and 4.3 nm for the chloroplast and mitochondrial enzyme, respectively.



Journal ArticleDOI
TL;DR: The structure of the hydrophilic part of the ATP synthase from chloroplasts (CF1) has been investigated by electron microscopy of negatively stained samples and shows that all projections are of a hexagonal or flattened hexagonal type.

Journal ArticleDOI
TL;DR: In this paper, solid-state ion exchange of protons of acidic and non-acidic OH groups for alkaline earth cations in mordenite-type zeolites was investigated by means of TGA, temperature-programmed evolution of gases, IR and in-situ IR/GC measurements.

Journal ArticleDOI
TL;DR: In this article, in-situ IR spectroscopy using dealkylation/disproportionation of ethylbenzene as a model reaction was used to investigate coke formation over a series of dealuminated mordenites.