Laser-Induced Target Patterns in the Oscillatory CO Oxidation on Pt(110)

Abstract

The formation of target patterns in oscillatory CO oxidation on Pt(110) is studied using the controlled creation of temperature heterogeneities on the catalyst surface induced by a focused laser beam. Outward and, for the first time, inward traveling target waves are observed as well as target patterns that are spatially confined to the immediate vicinity of the temperature inhomogeneity. The experimental results are compared to theoretical studies of the complex Ginzburg-Landau equation with a nonuniform frequency distribution and to numerical simulations of the Krischer-Eiswirth-Ertl model for the catalytic CO oxidation on Pt(110). Both the complex Ginzburg-Landau equation and the kinetic model need to be extended by a global coupling term to obtain good agreement with the whole range of experimental observations.

Target patterns in two-dimensional heterogeneous oscillatory reaction–diffusion systems

“…By varying these parameters and the reaction conditions, it would be possible to create different pacemakers and maybe also observe the onset of desynchronization in this system. Also, experiments of the CO oxidation reaction on platinum have recently been performed [12]. By pointing a laser beam onto the surface, the temperature is locally increased and the desorption of CO is enhanced.…”

“…Eq. (9) is formally equivalent to a Schrödinger equation for a quantum particle in a potential (12) with width 2R and depth…”

“…According to Eq. (12), this means that a heterogeneity acts as a wave source or pacemaker, creating an extended target pattern if and only if…”

“…Most basic features of such patterns already were described by the beginning of the 1980s [3][4][5][6], but since then target patterns have received less attention than, e.g., rotating spiral waves. Recently, renewed interest in target patterns and pacemakers has yielded considerable progress in the understanding of these patterns [7][8][9][10][11][12][13].…”

Evidence of Negative-Index Refraction in Nonlinear Chemical Waves

“…The recent discovery of antispiral and antitarget waves in reaction-diffusion systems [1][2][3] has attracted much interest because of a unique characteristic: the wave's phase velocity is opposite to their group velocity [4,5]. A normal concentric or spiral wave in a reaction-diffusion system has outward propagation from its wave source, because its phase velocity and group velocity point to the same direction.…”