Triplet state quenching by photoinduced radicals in the sensitized ethanol photolysis

UV irradiation of a rigid solution of 2-amino-pyrimidine in ethanol at 77 degrees K results in a sensitized production of ethyl radicals. The radicals are formed via a biphotonic process. The increase of the radical yield with irradiation time is directly correlated to a decrease of the number of triplet state molecules as detected by ESR. A kinetic model of the biphotonic process is presented and verified by experimental results. It supports the hypothesis of a catalytically enhanced radiationless decay process of the triplet states due to an interaction between the radicals and the triplet state molecules.