Cross-singular dips in the NMR absorption line of polycrystals with isolated spin pairs

Cross-singular dips at the center of the spectra of polycrystals of Pake systems, i.e., systems containing well-isolated pair groupings, are obtained by numerical calculations of the NMR absorption line for a 10-spin ( I =1/2) model. The physical reason for such dips is the behavior of the flip-flop component of the interpair dipole-dipole interactions (“6/5 factor”). Cases of experimental manifestation of cross-singular dips are noted.