DETERMINATION OF PARAMETERS OF EXCITED STATES OF DNA and RNA BASES BY LASER UV PHOTOLYSIS

Abstract

Abstract— The mechanism of photodecomposition of nucleic acid bases in a neutral aqueous solution upon two‐step excitation of high‐lying electronic states by a powerful laser UV radiation is discussed. Experimental dependences of photodecomposition efficiency versus UV radiation intensity are measured both under picosecond and nanosecond laser UV irradiations. By comparison of experimental dependences with a theoretical model, we obtain some characteristics of excited states, such as lifetime t 1 of the first electronic excited state S 1 intersystem crossing yield φ, photosensitivity from an intermediate excited state and others for all five nucleic acid bases.