Tunneling Resonances in Proton Spin-Lattice Relaxation

Abstract

Two sharp peaks have been observed in the magnetic field dependence of the proton spin-lattice relaxation rate of $\gamma$-irradiated 4-methyl 2,6-ditertiarybutylphenol at liquidhelium temperatures. The peaks are attributed to resonances between the frequencies of tunneling rotation of the 4-methyl groups and the Larmor frequency of the unpaired electron spins associated with free radicals. One peak is assigned to the tunneling resonance of the methyl groups of the free radicals and the other to undamaged molecules.