Time-Resolved Mass Spectrometric Studies of Fullerenes and Endohedral Fullerenes

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Abstract
The energetics and dynamics of C2 evaporations from fullerene radical cations Cn •+ were studied with and without ion trapping techniques. Electron space charge trapping was applied in electron ionization experiments. RF trapping in a Paul type ion source was applied for Laser MPI. Appearance energies, kinetic energy releases and metastable fractions were determined. the experimental data were modeled by finite heat bath theory (FHBT) and by RRKM/QET. Evaporation (binding) energies as well as conventional and intrinsic kinetic shifts were deduced. Our results support the following conclusions: (a) C60 sits on the leading edge of a magic shell, with C58 only slightly less stable and C62 considerably less stable than C60; (b) Dissociative decay is able to compete with radiative decay of C60 •+ only at internal energies in excess of 37.6 eV (Tb>2300 K); (c) a Ne endohedral atom has a slightly stabilizing effect on the C60 •+ cage whereas La is strongly stabilizing the C82 •+ cage; (d) C2 loss is a true evaporation in the sense of having a loose transition state with no reverse activation energy; (e) the C2 evaporations are statistical in nature and theories such RRKM/QET and FHBT are in excellent agreement with experimental observations.