We have studied the dependence of electron impact induced ionization and fragmentation of C60 molecules in effusive molecular beams upon the initial thermal excitation in the temperature range of 1190–1875 K, corresponding to an average vibrational energy of 10–20 eV. This is the largest energy range of parent molecule thermal excitation ever reported for electron-impact mass-spectrometric studies. The normalized curves of electron energy (Ee) dependent ion currents of C+60 and C+58 were measured and analyzed for the temperatures (T0) of 1190, 1435, 1570, 1695, and 1875 K. Similar measurements were done for C+2n (n=26–28) fragments for T0=1190 and 1875 K. We have developed an expression for the dependence of C+58 fragment ion current i58(Ee,T0), formed via the decay process C+60→C+58+C2, on electron energy and initial temperature. Using this expression and the strong temperature dependence observed, we have proposed a simple experimental method for estimating the energy deposition function—the probability density of vibrational excitation ε by an ionizing electron of energy Ee. The effective (apparent) value of maximum deposited energy was found to be εm(Ee)=Ee−E*, where E*=30±5 eV. Possible interpretations for this surprisingly low value are discussed. Comparing the experimental i58(Ee,T0) curves with the calculated ones over the range of Ee=30–80 eV we find that for T0≤1600 K, good agreement is obtained assuming that the C60 initial internal excitation is determined by the source temperature alone. For the higher temperature range 1600 K≤T0≤1900 K, we had to use a modified calculation taking into account radiative cooling and ensemble evaporative cooling processes along the molecular beam flight path. As a result, we have obtained an accurate simulation of the complete family of i58(Ee,T0) curves over all the temperature range measured, using a single set of independently measured physical quantities, and without any adjustable parameter. Uniqueness and sensitivity were thoroughly checked and demonstrated. The good agreement between experiment and calculation basically confirms our description of the underlying process and provides an additional support for the values of the independent physical parameters used. We have used maximum energy deposition parameter of E*=31 eV, an activation energy of E0=4.3–4.5 eV for the neutral fragmentation channel C60→C58+C2 and E1=4.0 eV for the ion fragmentation channel C+60→C+58+C2, and pre-exponential factors of A0=A1=2.5×1013 s−1. These values are very close to former ones obtained by us from analysis of time-of-flight distributions and integrated flux decay measurements of hot C60 molecular beams. Correspondence with other results reported in the literature is discussed and a two-step dissociation mechanism is proposed.

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A method of generating effusive molecular beams of C60 with vibrational temperatures up to 2000 K is presented. Direct measurement of the thermal stability and fragmentation kinetics of C60 in the range of 1100–1970 K, on the milliseconds time scale, provides thermal rate constants k(T)=10–300 s−1 (for T=1720–1970 K, respectively) and activation energy of E0=4.0±0.3 eV.

The scattering dynamics of hyperthermal C60 from a carbonized nickel surface at impact energies E0=10–50 eV was studied by high resolution angular and energy distributions. The scattered energy scales linearly with E0 and kinetic energy losses vary with scattering angle from ∼85 to ∼40%. Nearly complete decoupling between normal and tangential energy losses was found. The tangential losses are described in terms of various models of rotational excitation and the involvement of translational slip is concluded.

Formation of negatively charged C 60Ϫ was observed in the near-grazing scattering of hyperthermal ͑10-50 eV͒ neutral C 60 0 from a carbon-covered ͑monolayer graphite͒ nickel surface. Under these conditions the normal energy component of the scattered particle ͑0.3-1.5 eV͒ is of the same order of magnitude as the attractive potential well. We have measured both energy and angle distributions of the scattered C 60Ϫ and studied the electron transfer process by comparing the energy and angular distributions of the scattered negatively charged and neutral C 60 as a function of primary energy. The shifts observed between the angular and energy distributions maxima of the neutral and negative ion could be analyzed and explained in terms of image charge effects on the outgoing trajectory ͑deflection͒ and exit energy ͑retardation͒ of the C 60Ϫ . The angular deflection analysis yield image charge barrier of 0.28Ϯ0.02 eV corresponding to a rather large ''ion formation'' critical distance of 12.9Ϯ0.9 Å. We believe that this is the first direct observation of image charge effects in molecule/cluster-surface scattering.