La réaction de Belousov-Zhabotinsky donne spontanément naissance en couche mince à des structures ayant la forme de cibles. On présente les résultats d'une étude expérimentale statistique de ce type de structure conduite en milieu oscillant. Aucune des approches théoriques existantes ne rend convenablement compte des observations réalisées, même du seul point de vue qualitatif. L'origine de la rupture de symétrie du milieu ne peut donc pas encore être élucidée. Un approfondissement de la théorie et un renouvellement des voies de l'expérience demeurent nécessaires

The oscillatory Belousov–Zhabotinsky reaction is perturbed inhomogeneously by illumination with a focused laser beam for a given time interval and a quantity of heat is thus produced in a small region. The perturbation initiates a trigger wave for larger laser power. As the heat diffuses away from the initial location, the character of waves generated in succeeding cycles of the oscillatory reaction changes in a continuous manner to phase diffusion waves, predicted some years ago and observed for the first time. We measured transmission profiles with a Reticon system and calculate velocity profiles from the measurements. Phase shifts induced by the perturbation depend on the phase of the unperturbed oscillatory system at the instant of the imposition of the perturbation. For small perturbations, phase diffusion waves are induced initially. If the perturbation produces phase shifts exceeding 2π, then more than one trigger wave is generated within the first cycle of oscillation following the perturbation. A simple chemical model of oscillating reactions is used to calculate the major effects seen in the experiment.

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