SELF-CONSISTENT DETERMINATION OF FULLERENE BINDING-ENERGIES BE (C-N(-C-2), N=58,...,44())

Using recently measured accurate relative partial ionization cross sec tion functions for production of the C-60 fragment ions C-58(+) throug h C-44(+) by electron impact ionization, we have determined the respec tive binding energies BE(C-n(+)-C-2), with n = 58,...,44, using a nove l self-consistent procedure. Appearance energies were determined from ionization efficiency curves. Binding energies were calculated from th e corresponding appearance energies with the help of the finite heat b ath theory. Then using these binding energies we calculated with trans ition state theory (TST), the corresponding breakdown curves, and comp ared these calculated ones with the ones derived from the measured cro ss sections. The good agreement between these breakdown curves proves the consistency of this multistep calculation scheme. As the only free parameter in this procedure is the binding energy C-58(+)-C-2, we stu died the influence of different transition states chosen in the determ ination of this binding energy via TST theory and iterative comparison with breakdown curve measurements, Based on this study we can conclud e that extremely loose transition states can be confidently excluded, and that somewhat looser transition states than those used earlier res ult in an upward change of the binding energy of less than 10% yieldin g an upper limit for the binding energy C-58(+)-C-2 of approximately 7 .6 eV. (C) 1996 American Institute of Physics.