A magnetic switch for spin-catalyzed interconversion of nuclear spin isomers

The design of spin catalysis of the interconversion of ortho-hydrogen (o[H.sub.2]) and para-hydrogen (p[H.sub.2]) incarcerated in an endofullerene based on a reversible nitroxide/hydroxylamine system is demonstrated. The system is an example of a reversible magnetic spin catalysis switch that could increase the rate of interconversion of the nuclear spin isomers of [H.sub.2] by a factor of ~[10.sup.4].