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

Kinetic Energy Release Distributions (KERDs) have been measured for the C2 evaporation from a series of fullerenes including C80+ and its endohedral compounds, Sc3N@C80+ and Ti2@C80+. We have employed Finite Heat Bath Theory (FHBT) to analyze the measured KERDs and to deduce the C2 binding energies. We re-evaluated previously measured binding energies for C82+, La@C82+, and Tb@C82+ 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 C82+, to La@C82+ & Tb@C82+. The KERDs for all three ions, C80+, Sc3N@C80+, and Ti2@C80+ are nearly overlapping and the C2 binding energies are equal within experimental error. The binding energy deduced for C80+ is surprisingly high. C82+ on the other hand has nearly the same stability as C78+. These results indicate that C80 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. [Copyright &y& Elsevier]