Imaging Pattern Formation in Surface Reactions from Ultrahigh Vacuum up to Atmospheric Pressures

Rotermund, Harm Hinrich; Haas, G.A.; Franz, Rudolf; Tromp, R. M.; Ertl, G.

doi:10.1126/science.270.5236.608

Cited by 120 publications

(66 citation statements)

References 13 publications

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“…The 10 mm diameter sample was prepared by repeated cycles of Ar sputtering and O 2 treatment at 570 K, and subsequent annealing to 1000 K. Gas supplies for CO and O 2 , and pressure gauges, allow for controlled dosing of the reactants. Adsorbate concentration patterns on the surface of the sample are imaged using ellipsomicroscopy for surface imaging (EMSI) [23]. The light of another Ar laser is focused onto a spot of about 50 m diameter on the surface, causing a local temperature increase of up to 10 K. Using computercontrolled galvanometer mirrors, the focused laser beam can be positioned in 1 ms with a spatial precision of 5 m anywhere within the viewing field (1:5 1:3 mm 2 ).…”

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Gentle Dragging of Reaction Waves

et al. 2003

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Using a recently realized ''addressable catalyst surface'' [Science 294, 134 (2001)] we study the interaction of chemical reaction waves with prescribed spatiotemporal fields. In particular, we study how a traveling chemical pulse is ''dragged'' by a localized, moving temperature heterogeneity as a function of its intensity and speed. The acceleration and eventual ''detachment'' of the wave from the heterogeneity is also explored through simulation and stability analysis. DOI: 10.1103/PhysRevLett.90.018302 PACS numbers: 82.40.Bj, 05.45.-a, 82.40.Np, 82.45.Jn As the elements of spontaneous pattern formation are progressively understood through theory, experimentation, and scientific computation [1], ways to purposefully interact with the coherent structures (pulses and fronts) that constitute the building blocks of spatiotemporal patterns are becoming the focus of extensive research [2,3]. In particular, the stabilization and control of various patterns [3-9] through local, nonlocal, or global feedback, and pattern formation in media with designed heterogeneities [10 -12] are the source of novel insights for spatiotemporal dynamics.To explore such phenomena, we have recently constructed an ''addressable catalyst'': A focused laser beam, manipulated through computer-controlled mirrors and capable of ''writing'' spatiotemporal temperature heterogeneity patterns on a metal single crystal catalyst. The loop between this actuation and sensing (both resolved in space and time) through nonintrusive microscopies is then closed through the computer or the experimentalist herself/himself in real time. Our model system is the low-pressure catalytic oxidation of CO on Pt(110), a reaction exhibiting well-documented spatiotemporal patterns [13][14][15][16], and whose macroscopic modeling has reached an advanced level [17][18][19][20].In this Letter we study the interaction of reactive pulses with a single, spatially coherent but temporally mobile heterogeneity. In particular, we use a temperature heterogeneity, localized in space and steadily moving in time, to ''drag'' spontaneously isothermally forming reactive pulses and fronts with speeds differing from their natural speed. We examine the shapes acquired by these dragged waves and their limits of stability (that is, the range of dragging speeds for which they can exist). Through computer-aided analysis we examine the nature of the detachment instability, marking the loss of the ability of the heterogeneity to drag a pulse in 1D or 2D. Two possible paths to instability (depending on the linearized spectrum crossing) are detected. We explore the postdetachment transient dynamics and the interactions of a pulse with successive elements of a 1D periodic, constant speed array of identical heterogeneities. The theme of pulse dragging is currently also being explored in a variety of physically relevant Hamiltonian systems, or weakly perturbed dissipative variations thereof (targeted transfer of pulses in optical media or the motion/displacement of harmonic traps or optical l...

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Gentle Dragging of Reaction Waves

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“…For sample preparation, Ar-ion sputtering, oxygen treatment and annealing up to 900 K were used. Adsorbate concentration patterns on the sample surface were imaged using reflection-anisotropy microscopy (RAM; Rotermund et al 1995). A schematic experimental set-up is shown in figure 1.…”

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Control of spatiotemporal chaos in catalytic CO oxidation by laser-induced pacemakers

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Punckt

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et al. 2007

Phil. Trans. R. Soc. A.

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Control of spatiotemporal chaos is achieved in the catalytic oxidation of CO on Pt(110) by localized modification of the kinetic properties of the surface chemical reaction. In the experiment, a small temperature heterogeneity is created on the surface by a focused laser beam. This heterogeneity constitutes a pacemaker and starts to emit target waves. These waves slowly entrain the medium and suppress the spatiotemporal chaos that is present in the absence of control. We compare this experimental result with a numerical study of the Krischer-Eiswirth-Ertl model for CO oxidation on Pt(110). We confirm the experimental findings and identify regimes where complete and partial controls are possible.

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“…The 10 mm diameter sample was prepared by repeated cycles of Ar sputtering and O 2 treatment at 570 K, and subsequent annealing to 1000 K. Gas supplies for CO and O 2 , and pressure gauges, allow for controlled dosing of the reactants. Adsorbate concentration patterns on the surface of the sample are imaged using ellipsomicroscopy for surface imaging (EMSI) [28]. The light of another Ar-ion laser is focused onto a spot of about 50 m diameter on the surface causing a local temperature increase of up to 10 K. Using computer-controlled galvanometer mirrors, the focused laser beam can be positioned in 1 ms with a spatial precision of 5 m anywhere within the viewing field (1:5 1:3 mm).…”

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Wave Initiation through Spatiotemporally Controllable Perturbations

et al. 2003

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We study the initiation of pulses and fronts in a two-dimensional catalytic reaction-diffusion system: CO oxidation on Pt(110). Using a computer-controlled mobile focused laser beam, we impart various patterns (in space and time) of localized temperature ''kicks'' to the surface. We explore, and also rationalize through modeling, the cooperativity of such individually subcritical perturbations in both the excitable and the bistable regime.

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Imaging Pattern Formation in Surface Reactions from Ultrahigh Vacuum up to Atmospheric Pressures

Cited by 120 publications

References 13 publications

Gentle Dragging of Reaction Waves

Gentle Dragging of Reaction Waves

Control of spatiotemporal chaos in catalytic CO oxidation by laser-induced pacemakers

Wave Initiation through Spatiotemporally Controllable Perturbations

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