Kinetics of a monomolecular photoreaction in a strongly light-absorbing solid solution exemplified by the forward reaction of the optically switchable o-thiobenzoquinone methide⇌benzo[b]thiete system

The kinetics of the photobleaching process o-thiobenzoquinone methide (1) → benzo[b]thiete (2), i.e. the forward reaction of the optically switchable 1⇌2 system, in a solid argon layer has been investigated experimentally by measuring the time-dependent photon flux density (photon irradiance) of the transmitted photolysis light. A kinetic model is presented which simultaneously accounts for both the anisotropy of the light absorption and variation of the photon flux density in the layer with position and time. Good agreement between theory and experiment is achieved.