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-d8 were analyzed quantitatively. Model calculations show that the spin-selective recombination of radicals gives rise to the electron polarization and, with regard to the electron-nuclear 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 radicals at a magnetic field of 7 T, fitting the theoretical results to the experimental data gives the electron relaxation time T1e = 1.0 ± 0.2 μs and the cross-relaxation time Tx = 92 ± 18 μs.