Kinetics of nuclear polarization in the geminate recombination of biradicals

Abstract

The singlet-triplet evolution of alkyl-acyl biradicals under S-T 0 mixing within submicrosecond time range has been studied by the method of flash CIDNP 1H during the photolysis of cyclic aliphatic ketones. The maximum of nuclear polarization has been detected 160 ns after exciting laser pulse. The invariance of the CIDNP time-dependence curve relative to the isotopic substitution of ketone in the α-position at the polymethylene chain length of 10 and 11 has been demonstrated. The nuclear polarization evolution has been calculated both in terms of formal kinetics and using the kinematic approximation in the theory of geminate recombination for the two-position biradical model.