Laser photosynthesis of previtamin D: new effects of high-intensity picosecond irradiation

An investigation was made of the influence of the intensity of picosecond (?p ? 23 ps) laser pulses on the kinetics of the photosynthesis of previtamin D3. An increase of the intensity from 1012 to 1014 W m-2 resulted in significant changes in the photosynthesis kinetics: the photoreaction rate fell and so did the efficiency of the cis?trans isomerisation of previtamin D. An analysis showed that two-step absorption made only a small contribution to these effects and that they were mainly associated with the excitation of nonequilibrium conformers of the previtamin molecule.