Characteristics of photolysis of provitamin D by long-wavelength radiation

An analysis is reported of the experimental results on laser photolysis of provitamin D, carried out by the ultraviolet spectroscopy method, and of numerical calculations of the kinetics of photolysis at different wavelengths. Cardinal changes in the kinetics of photolysis by long-wavelength radiation are attributed to a steep rise of the rate of irreversible photoreactions. The observed eifect is in conflict with the usual assumption that these photoreactions are of secondary importance and it means that an allowance for the irreversible photoreaction channel must be made in the generally accepted scheme.