Particular features of photochemical transformations of molecules initiated by continuous external impact

Abstract

Photochemical transformations induced by long-term continuous exposure to light have been studied. Using the developed theory and methods for calculating photochemical processes, computer experiments have been performed and their results have been analyzed for a large number of model systems and particular reactions. The excitation process has been considered in an explicit form, and the population of energy levels in excited states by absorption of light quanta has been taken into account. It has been shown that continuous optical excitation qualitatively changes the situation in comparison with pulsed excitation: the quantum yield is not zero even at very low quantum beat frequencies. For fast reactions, the kinetics of the process is exponential; in the case of slow reactions, concentration oscillations (on the order of 25% or more) arise, which are clearly manifested in the stationary state of the molecular system. The choice of the optimal photoirradiation time is an important factor in experimental design aimed to obtain a desired amount of the product. Molecular modeling makes it possible to a priori evaluate this quantity.