Triplet radical interaction. Direct measurement of triplet polarization transfer by Fourier transform electron paramagnetic resonance

An FT-EPR (Fourier transform electron paramagnetic resonance) method for th e direct measurement of the electron spin polarization generated in stable radicals through photoexcited tripler and radical interaction is presented. This method depends on the ability to calculate numerically the filling fa ctor of the irradiated volume in the EPR cavity. By this experimental metho d the polarization at different times after the laser pulse can be determin ed. This enables us to differentiate between the different processes genera ting the polarization in the radical, which are the ESPT (electron spin pol arization transfer), when the tripler meeting the radical is still polarize d, and the RTPM (radical triplet pair mechanism). for thermal triplets. The different time evolutions of the two mechanisms allow the spin-lattice rel axation time (T-1) of the triplet in liquid solution to be determined. Expe rimental verifications were made with galvinoxyl-porphyrin systems in tolue ne at different temperatures.