Stefan Wehner

  • Citations Per Year
Learn More
The rate of CO oxidation on Ir(111) surfaces exhibits bistability at T=500 K in a range of the CO fraction Y in the CO+O reactant gas flux. Measured CO2 rates as a function of the noise strength imposed on Y are well reproduced by parameter-free modeling. We present photoelectron emission microscopy measurements and 2D calculations of the spatiotemporal(More)
We use photoelectron emission microscopy (PEEM) measurements to study the spatiotemporal patterns obtained for the CO oxidation reaction on Ir(111) as a function of the noise strength we superpose on the CO and the oxygen fractions of the constant total reactant gas flux. The investigations are focused on the bistable regime this reaction displays including(More)
We study the effect of external noise on the catalytic oxidation of CO on an Iridium(111) single crystal under ultrahigh vacuum conditions. This reaction can be considered as a model of catalysis used in industry. In the absence of noise the reaction exhibits one or two stable stationary states, depending on control parameters such as temperature and(More)
We study experimentally and theoretically the influence of noise on the fractions of CO and oxygen in the constant gas flow directed at an Ir(111) surface during CO oxidation. Depending on the noise strength and the fraction Y of CO we observe in the deterministically bistable region a large variety of different types of behavior. These include bistable(More)
This review summarizes recent studies on the catalytic CO oxidation on Iridium(111) surfaces. This was investigated experimentally under ultrahigh vacuum (UHV) conditions using mass spectroscopy to detect gaseous products and photoelectron emission microscopy (PEEM) to visualize surface species. The underlying reaction–diffusion system based on the(More)
We study the effect of external noise on the catalytic oxidation of CO on an Iridium(111) single crystal under ultrahigh vacuum conditions. This reaction can be considered as a model of catalysis used in the industry. In the absence of noise, the reaction exhibits one or two stable stationary states, depending on the control parameters such as temperature(More)
In this work, we study a surface reaction on Pd(111) crystals under ultra-high-vacuum conditions that can be modeled by two coupled reaction-diffusion equations. In the bistable regime, the reaction exhibits travelling fronts that can be observed experimentally using photo electron emission microscopy. The spatial profile of the fronts reveals a(More)
In this article we consider the CO oxidation on Ir(111) surfaces under large external noise with large autocorrelation imposed on the composition of the feed gas, both in experiments and in theory. We report new experimental results that show how the fluctuations force the reaction rate to jump between two well defined states. The statistics of the reaction(More)
Two types of bacteria were placed on the top surface of carbon nanotube films and the composite film morphology was examined using scanning electron microscopy. The interaction of bacteria with the carbonaceous film was studied after drying and subsequent heating to 1000 °C. For gram-positive bacteria, subsequent shrinkage of the bacterial layer causes film(More)
Rate measurements of the reaction CO + O --> CO(2) on palladium(111) single crystal surfaces have been performed by means of mass spectroscopy under ultrahigh vacuum conditions. The total flux Phi of the impinging reactants CO and O(2) was held constant at 1 ML s(-1), whereas its CO fraction Y was varied between 0 (pure O(2)) and 1 (pure CO). The(More)