Efficiency of two-stage photolysis of DNA bases by high-power ultraviolet laser radiation

A theoretical and experimental investigation was made of the efficiency of two-stage photolysis of DNA bases in aqueous solutions as a result of the successive absorption of two ultraviolet quanta via intermediate first singlet and first triplet excited states. It is shown that when ultraviolet laser pulses of 30 psec duration are used, the photolysis efficiency is eight times higher than that when pulses of 20 nsec duration are used.