Change of {sup 7}Be decay rate in exohedral and endohedral C{sub 60} fullerene compounds and its implications

The half-life of exohedral {sup 7}Be-C{sub 60} complex and that of {sup 7}Be implanted in a gold foil have been found to be about the same within {approx_equal}0.2%. Using a radiochemical technique, we also measured that the probability of formation of endohedral {sup 7}Be-C{sub 60} complex by nuclear implantation technique was (5.6 {+-} 0.45)%. We also find that the half-life of endohedral {sup 7}Be-C{sub 60} complex is shorter than that of exohedral complex by more than 1%. An analysis of these results using linear muffin-tin orbital method calculations indicates that most of the implanted {sup 7}Be ions in fullerene C{sub 60} stay at a distance of {approx_equal}5.3 A from the centers of nearest C{sub 60} molecules forming exohedral compounds and those who enter the fullerene cages go to the centers of the cages forming endohedral {sup 7}Be-C{sub 60} compounds.