Nuclear spin isomers of guest molecules in H 2 @C 60 , H 2 O@C 60 and other endofullerenes

Spectroscopic studies of recently synthesized endofullerenes, in which H 2 , H 2 O and other atoms and small molecules are trapped in cages of carbon atoms, have shown that although the trapped molecules interact relatively weakly with the internal environment they are nevertheless susceptible to appropriately applied external perturbations. These properties have been exploited to isolate and study samples of H 2 in C 60 and other fullerenes that are highly enriched in the para spin isomer. Several strategies for spin-isomer enrichment, potential extensions to other endofullerenes and possible applications of these materials are discussed.