Homogeneous broadenings in 2D solid-state NMR of half-integer quadrupolar nuclei

The question of the homogeneous broadening that occurs in 2D solid-state NMR experiments is examined. This homogeneous broadening is mathematically introduced in a simple way, versus the irreversible decay rates related to the coherences that are involved during t(1) and t(2). We give the pulse sequences and coherence transfer pathways that are used to measure these decay rates. On AIPO(4) berlinite, we have measured the Al-27 echo-type relaxation times of the central and satellite transitions on IQ levels, so that of coherences that are situated on 2Q. 3Q, and 5Q levels. We compare the broadenings that can be deduced from these relaxation times to those directly observed on the isotropic projection of berlinite with multiple-quantum magic-angle spinning (MAS), or satelite-transition MAS. We show that the choice of the high-resolution method, should be done according to the spin value and the corresponding homogeneous broadening. (c) 2006 Elsevier Inc. All rights reserved.