The outside knows the difference inside: trapping helium by immediate reduction of the orifice size of an open-cage fullerene and the effect of encapsulated helium and hydrogen upon the NMR of a proton directly attached to the outside

A methodology to entrap He inside an open-cage fullerene by immediate reduction of the size of an orifice was developed, and the effects of encapsulated He and H(2) on the chemical shift of a proton directly attached to the outer fullerene sphere were revealed.