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 the 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 factor of the irradiated volume in the EPR cavity. By this experimental method the polarization at different times after the laser pulse can be determined. This enables us to differentiate between the different processes generating the polarization in the radical, which are the ESPT (electron spin polarization transfer), when the tripler meeting the radical is still polarized, and the RTPM (radical triplet pair mechanism). for thermal triplets. The different time evolutions of the two mechanisms allow the spin-lattice relaxation time (T-1) of the triplet in liquid solution to be determined. Experimental verifications were made with galvinoxyl-porphyrin systems in toluene at different temperatures.