Non-linear dynamics in photochemistry

Kinetic Analysis of Photochromic Systems under Continuous Irradiation. Application to Spiropyrans

“…The general kinetic scheme of the photochromic phenomenon involving an isomerization of a stable isomer A into an unstable one B can be schematized as where F is a dimensionless term referred to as the photokinetic factor. It is solely a function of Abs‘ (namely of [A] and [B] and thus of the progress of the reaction); it ranges from 2.3 to 0 for values of Abs‘ ranging from 0 to ∞. , Abs‘, ε‘ A , and ε‘ B are respectively the total absorbance of the solution and the molar extinction coefficients of A and B at the irradiation wavelength λ‘; l is the optical path; [A] and [B] are the concentrations of A and B, and they are related by the equation of conservation of matter: where [A] 0 is the initial concentration of the stable isomer A.…”