Nonlinear dynamics, multiple steady states, and oscillations in photochemistry

Light is often considered as a type of chemical reagent. As a result, there is a natural tendency to infer that the rate equations describing the dynamics of photochemical systems should not differ significantly from their light-free counterparts. There are, however, two important differences between chemical and photochemical systems. The first one is that photochemical systems are nonisolated closed systems that are maintained away from their thermodynamic equilibrium by the photon flux. The second difference lies in the rather peculiar nature of the interaction between light and the physical medium in which the photoreaction takes place