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SYSS: Structure Formation and Self-Organization in non-equilibrium Systems

SYSS 1: Structure Formation and Self-Organization in non-equilibrium Systems I

SYSS 1.9: Vortrag

Donnerstag, 30. März 2006, 11:45–12:00, BAR Sch\"o

Pattern formation in the CO + O reaction on Ir(111) surfaces under the influence of noise — •Stefan Wehner¹, Patrick Hofmann², Dieter Schmeisser², Helmut R. Brand³, and Jürgen Küppers^1,4 — ¹Experimentalphysik III, Universität Bayreuth, 95440 Bayreuth, Germany — ²Angewandte Physik II, Brandenburgische Technische Universität Cottbus, 03013 Cottbus, Germany — ³Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth, Germany — ⁴Max-Planck-Institut für Plasmaphysik (EURATOM Association), 85748 Garching, Germany

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. Quadrupol mass spectrometer measurements of the CO₂ rates as a function of the noise strength imposed on Y are well reproduced by parameter-free modeling.

We present Photoelectron emission microscopy (PEEM) measurements and 2D calculations of the spatio-temporal patterns of CO and O rich domains. The role of combined multiplicative and additive noise on Y for CO and O domain wall motion and island nucleation-growth-coalescence processes is analysed.

For small noise amplitudes few islands nucleate and grow up to some 100 µ m in diameter, before they merge with another island. With increasing noise amplitudes more islands nucleate. With large noise amplitudes bursts to and switching between the branches is observed. The domain wall velocity is found to be independent of the noise strength and island size.