INVESTIGATION INTO THE STRUCTURE OF MOLECULAR-CRYSTALS BY MEANS OF MULTIPULSE NUCLEAR-QUADRUPOLE RESONANCE

Cross polarization is studied in 14 polycrystalline compounds during m ultipulse spin-locking for quadrupolar Cl-35 nuclei in zero external m agnetic field. It is shown that the time of cross relaxation of Cl-35 magnetization in proton-containing polycrystals, T-1e, is much shorter than the time of spin-lattice relaxation in the laboratory frame of r eference. It is reliably established that the drastic reduction of T-1 e is associated with spin energy exchange between the Zeeman reservoir of Cl-35 nuclei and dipolar reservoir of protons. The rate of spin di ffusion is controlled by heteronuclear dipole-dipole interactions whic h, in turn, depend on the structure of the crystal and its constituent molecules. Dependences of T-1e on the parameters of an MW-4 pulse seq uence are studied. The possibility of determining the relative positio ns of molecular fragments in organic crystals is demonstrated. It is p roposed that this method be used as a supplement to other radiofrequen cy spectroscopic means of analyzing the structure of molecules in crys tals.