QUADRUPOLE-ECHO TECHNIQUES IN MULTIPLE-QUANTUM-FILTERED NMR-SPECTROSCOPY OF HETEROGENEOUS SYSTEMS

Multiple-quantum-filtered quadrupole-echo pulse sequences for spin I = 1 and I = 3/2 are suggested. A general condition for obtaining simult aneously Zeeman and quadrupolar echo is formulated. A theoretical anal ysis of the various pulse sequences was performed on the basis of seco nd-order perturbation approximation of the Liouville equation for the density matrix. The extent of refocusing as a function of the ratio of the residual quadrupolar interaction and the relaxation rates was cal culated. Experimental results are presented for H-2 and Na-23 in carti lage as an example of a heterogeneous system with residual quadrupolar interaction. The difference between relaxation times measured by the multiple-quantum-filtered echo techniques and those measured by conven tional multiple-quantum-filtered NMR spectroscopy is a simple diagnost ic of anisotropic motion that leads to a residual quadrupolar interact ion. The results of the echo experiments are compared with the relaxat ion times computed on the basis of lineshape analysis of double-quantu m-filtered spectra of a heterogeneous system. (C) 1995 Academic Press, Inc.