Nature 305, 43 - 45 (01 September 1983); doi:10.1038/305043a0

Hydrodynamic instabilities and photochemical reactions

J. C. Micheau¹, M. Gimenez², P. Borckmans² & G. Dewel²

¹Intéraction Moléculaire et Réactivité Chimique et Photochimique, ERA au CNRS No. 264, Université Paul Sabatier, 31062 Toulouse, France
²Service de Chimie-Physique II, Université Libre de Bruxelles, 1050 Bruxelles, Belgium

Although many photochemical structures obtained in irradiated solutions have been investigated recently¹⁻⁴, the origin of these patterns has remained unclear. Evidence has been presented which suggests that these structures are due to evaporative cooling. Using the Schlieren technique, photographs of prepatterns have been obtained before illumination and we show here that these prepatterns are associated with convective motions in the bulk. As a result, the hydrodynamic motions must be given proper consideration in the interpretation of spatio-temporal chemical patterns. The photochemical reaction also provides a useful way of visualizing slow convective motions.