Dissipative Solitons in Reaction Diffusion Systems Mechanisms, D
Dissipative solitons are local excitations of nonlinear continuous systems which emerge due to a flux of energy or matter. Although they are continuous entities, dissipative solitons in reaction diffusion systems behave like particles: They are generated
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Experimental Observations
An experiment is a device to make Nature speak intelligibly. After that one has only to listen. George Wald [2.1]
Abstract Starting points for getting acquainted with the phenomena of dissipative solitons are chemical reaction diffusion systems and a planar semiconductor-gasdischarge system. These systems exhibit dissipative solitons in the form of selforganized localized concentration spots and current density filaments, respectively. The chapter discusses the experiments and concentrates on the phenomena being directly related to the particle-like characteristics of dissipative solitons in spatially extended systems. These are the dynamics of single dissipative solitons, their mutual interaction by scattering and formation of bound states, as well as generation and annihilation processes. Due to the focus of the book, only continuously driven experiments are considered.
2.1 Chemical Systems 2.1.1 Overview Since the first successful experimental realization of Turing patterns in a reactiondiffusion system in the beginning of the 1990s, which was undertaken by de Kepper and coworkers in the chlorite-iodate-malonic-acid (CIMA) system [2.2], the number of systems showing stationary patterns has increased significantly and the focus of research has changed to the control of spatio-temporal structure formation [2.3,2.4]. Nearly at the same time another important experimental observation was reported, namely the self-organization of localized concentration spots in a surface reaction [2.5]. These dissipative solitons propagate in a lateral extended system and interact A.W. Liehr, Dissipative Solitons in Reaction Diffusion Systems, Springer Series in Synergetics 70, DOI 10.1007/978-3-642-31251-9 2, © Springer-Verlag Berlin Heidelberg 2013
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2 Experimental Observations
Fig. 2.1 Propagating and interacting dissipative solitons observed as concentration peaks of atomic oxygen adsorbed on the (110) face of a platinum crystal under steady-state conditions of catalytic CO oxidation. Regions with increased oxygen concentration appear dark. (a) Two PEEM images recorded with a time interval of 3.0 s from a 130 70 m2 -region of the crystal, (b) sequence of seven PEEM images recorded with a time interval of 1.1 s from a 10 30 m2 slice showing the merging and splitting of two interacting dissipative solitons. Parameters: pO2 D 35 mPa, pCO D 10 mPa, T D 485 K, texp D 20 ms (Reprinted figure with permissions from [2.5])
in a characteristic way with each other (Sect. 2.1.2). However, although the majority of papers on structure formation in chemical systems consider spatially extended systems, reports on dissipative solitons in these systems are rarely found. The reason is twofold: In the case of the dissipative solitons observed in the ferrocyanideiodate-sulphite reaction [2.6] some experimental details were not obvious and it took more than a decade to reproduce the original observations (Sect. 2.1.5). In the majority of other systems an external stabilization is either needed in the form
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