Determining C2 binding energies from KERDs for C80+ and C82+ fullerenes and their endohedrals

Abstract Kinetic Energy Release Distributions (KERDs) have been measured for the C 2 evaporation from a series of fullerenes including C 80 + and its endohedral compounds, Sc 3 N@C 80 + and Ti 2 @C 80 + . We have employed Finite Heat Bath Theory (FHBT) to analyze the measured KERDs and to deduce the C 2 binding energies. We re-evaluated previously measured binding energies for C 82 + , La@C 82 + , and Tb@C 82 + in the light of recent findings that fragmentation of fullerene ions proceeds via a very loose transition state. This procedure demonstrates a substantial increase in the binding energy on going from C 82 + , to La@C 82 + & Tb@C 82 + . The KERDs for all three ions, C 80 + , Sc 3 N@C 80 + , and Ti 2 @C 80 + are nearly overlapping and the C 2 binding energies are equal within experimental error. The binding energy deduced for C 80 + is surprisingly high. C 82 + on the other hand has nearly the same stability as C 78 + . These results indicate that C 80 is a magic number. The results will be discussed in the light of proposed structures for the various compounds and the reliability of data deduced from KERDs.