KINETICS OF A MONOMOLECULAR PHOTOREACTION IN A STRONGLY LIGHT-ABSORBING SOLID-SOLUTION EXEMPLIFIED BY THE FORWARD REACTION OF THE OPTICALLYSWITCHABLE O-THIOBENZOQUINONE METHIDE-REVERSIBLE-ARROW-BENZO[B]THIETESYSTEM

The kinetics of the photobleaching process o-thiobenzoquinone methide (1) --> benzo[b]thiete (2), i.e. the forward reaction of the optically switchable 1 reversible arrow 2 system, in a solid argon layer has be en 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 th e anisotropy of the light absorption and variation of the photon flux density in the layer with position and time. Good agreement between th eory and experiment is achieved.