INEPT experiments involving quadrupolar nuclei in solids

Coherence transfer from quadrupolar Al-27 (I = 5/2) nuclei to P-31 (I = 1/2) via INEPT experiments is investigated. Al-27 --> P-31 INEPT experiments on a (CH3)(3)P-AICl(3) complex in zeolite NaX are performed, and the results demonstrate that the P-31 INEPT signals strongly depend on whether or not the Al-27 pulses are applied synchronously with the rotor period, and on the length of the Al-27 pulses. A density-matrix calculation involving the use of the spin operators for spin 3/2 and 1/2 nuclei has been performed to help understand the evolution behavior of the density matrix under the influence of the quadrupolar interaction, the dipolar and J-couplings, and the pulse lengths applied to the quadrupolar nuclei. The theoretical predictions obtained from these calculations are consistent with the INEPT experimental observations, (C) 1998 Academic Press.