EVIDENCE FOR RARE-GAS ENDOHEDRAL FULLERENE FORMATION FROM GAMMA-RECOIL FROM HPLC STUDIES

In this paper, we present the first direct evidence for the formation of endohedral fullerenes from prompt gamma emission of neutron irradia ted Xe held interstitially in the C-60 lattice. Following neutron acti vation, solutions of the irradiated solid were analyzed by high-pressu re liquid chromatography and gamma spectroscopy which showed Xe radioi sotopes to be present in fractions that eluted at longer times relativ e to untreated C-60. The observation of Xe radioisotopes at these arti cular times was attributed to elution of compounds based on Xe@C-60. A dditional support for this conclusion was obtained from isotopic ratio s measured by gamma spectroscopy. The present results provide convinci ng evidence in support of the gamma recoil mechanism for trapping radi onuclides in fullerene cages which had previously been inferred from i ndirect evidence.