On the coordinate of a singular point of time correlation functions for the system of nuclear magnetic moments of a crystal

Abstract

The hypothesis concerning the existence of singular points on the imaginary time axis for a correlation function of a system with the dipole-dipole interaction of nuclear spins of a crystal is verified. Within the framework of the self-consistent fluctuating field theory taking into account the principal corrections related to the correlation of local fields, a result for this coordinate is obtained in terms of the ratios of lattice sums. Experimental values of this coordinate are calculated from the wings of the nuclear magnetic resonance absorption spectrum of a BaF2 crystal for the magnetic field directions along the three crystallographic axes. Good agreement of the theoretical and experimental results justifies this hypothesis.