Abstract
The distribution of hexamethylbenzene (HMB) molecules among the cavities of a Na-Y zeolite has been investigated by both xenon-129 and multiple-quantum NMR. For samples prepared at 523 K, xenon NMR shows that HMB molecules are dispersed nonuniformly, entering and remaining in the first available zeolite cavities. After further heat treatment at 573 K, the xenon spectrum collapses to one single line characteristic of a macroscopically uniform molecular distribution; multiple-quantum NMR “counting” indicates spin clusters of about 16 hydrogens, consistent with one HMB (18 hydrogens) per cavity.