Temperature dependence of electron spin-lattice relaxation of methyl radicals in glassy organic matrices:Relation to environmental dynamics and radical decay

Abstract

The electron spin-lattice relaxation of trapped methyl radicals in methanol , 2−methyltetrahydrofuran, and 3−methylhexane glasses has been directly studied as a function of temperature from 5-100 K by the saturation recovery method. The relaxation rate remains fast at low temperatures and shows a large component linear in temperature. This is interpreted in terms of the recently developed model of tunneling relaxation involving modulation of the electron nuclear dipolar interaction by tunneling of nuclei in the radical’s environment [J.Phys.Chem.81,456 (1977)]. Deuteration experiments show that CH3 and [J.Phys.Chem.81,456 (1977)]. Deuteration experiments show that CH3 and CD3 have the same relaxation rate while it is decreased by about four−fold by deuterating the matrix. There also appears to be a correlation between the spin-lattice relaxation rate and the decay of methyl radicals in these matrices.