Complex Patterns in a Periodically Forced Surface Reaction

Effects of time-periodic, spatially uniform forcing on oscillatory chemical turbulence are studied in experiments with catalytic CO oxidation on a platinum(110) single-crystal surface. A variety of complex spatiotemporal reaction−diffusion patterns is investigated under variation of the forcing amplitude and frequency. Near harmonic resonance with the forcing, intermittent turbulence characterized by the presence of localized turbulent bubbles on a homogeneously oscillating background and disordered cellular structures are observed. In the parameter region where the system exhibits 2:1 subharmonic resonance, irregular oscillatory stripes and cluster patterns are found. For such resonant patterns, a frequency demodulation technique is used to reconstruct phase and amplitude variables from the experimental data.