129Xe magic-angle spinning spectra of xenon in zeolite NaA. Direct observation of mixed clusters of co-adsorbed species.

We present the first demonstration that the individual 129Xe resonances corresponding to Xen (n = 1-8) clusters inside the alpha-cages of zeolite NaA can be narrowed under magic-angle spinning (MAS). Under these high-resolution conditions we also observe upon addition of Kr the individual peaks corresponding to mixed clusters, XenKrm, inside the alpha-cages, which will allow the first direct determination of the distribution of co-adsorbates in a microporous solid. Under MAS the chemical shifts of the Xen clusters are shown to be highly sensitive to "disorder" in the zeolite and provides new, quantitative information about the presence of alpha-cages of several types.