Radical pairs in irradiated single crystals of 1-methyl uracil

Abstract

Irradiated single crystals of 1-methyl uracil exhibit the presence of several types of radical pairs. Three of them have been identified. Each pair is composed of a hydrogen-abstraction and a hydrogen-addition radical. The calculations performed show that the postulation of a very strong exchange interaction is not necessary for the existence of the triplet state, if only the sufficiently large dipole-dipole interaction is present. On the basis of the experimental findings the mechanism of the radical formation has been discussed. The relevance of that mechanism for the damaging process of DNA has also been indicated.