TIME EVOLUTION OF PROTON MAGNETIZATION IN THE SPIN-ROTATING FRAME OF AN ENSEMBLE OF INTERACTING PAIRS OF METHYL-GROUPS - A STUDY OF THE MAGNETIC-FLUX EFFECT

The effect of an external magnetic field on a pair of interacting meth yl gr,,ups in a solid lattice is considered. Because of the consequent appearance of a gauge potential in the fetal Hamiltonian of the syste m, its time-reversal invariance is broken, leading to the splitting of otherwise degenerate E levels. Since transitions between these states influence the time evolution of the Zeeman polarization in the rotati ng frame, calculations are presented from which the spectra for a part icular energy-level scheme are obtained in the case of a fictitious cr ystal and a polycrystalline sample. It ij shown that the appearance of spectral features at frequencies other than integer multiples of the rf frequency omega(1) can be taken as evidence of transitions between magnetic-flux-split E states. The polycrystalline spectrum is compared to the experimental spectrum of two solids with qualitative agreement if the effective charge on the protons is 0.15 and 0.10, respectively , of the elementary charge.