CROSS-RELAXATION MECHANISM FOR THE FORMATION OF NUCLEAR-POLARIZATION - A QUANTITATIVE TIME-RESOLVED CIDNP STUDY

The kinetics of the nuclear polarization formed during the photolysis of acetone in isopropanol-d(8) were analyzed quantitatively. Model cal culations show that the spin-selective recombination of radicals gives rise to the electron polarization and, with regard to the electron-nu clear cross-relaxation, are adequate to describe the formation of the net nuclear polarization of the reaction products even if the solution contains only one type of radical. For the 2-hydroxy-2-propyl radical s at a magnetic field of 7 T, fitting the theoretical results to the e xperimental data gives the electron relaxation time T-1(e) = 1.0 +/- 0 .2 mu s and the cross-relaxation time T-x = 92 +/- 18 mu s.