Energy partition in collisions of C60+ ions with diamond (111) and graphite (0001) surfaces

Velocity distributions and fragmentation of C60 molecules after collision with type IAa diamond (111) and graphite (0001) surfaces are studied for primary energies up to 500 eV at a scattering angle of 140 degree using time-of-flight mass spectrometry. The absolute scattering yield is much lower for diamond due to polishing induced surface corrugation. However, the final velocity distribution of C60+ and its rate of metastable fragmentation after collision are similar for scattering off the two targets, and is interpreted by their similar lateral atomic structure. At a particular impact energy, the final internal energy of C60+, as monitored by the rate of metastable fragmentation, increases with final kinetic energy, but the energy transferred to the target decreases. These results are understood when considering the collision as a two-step mechanism, in which the impact energy is transformed into thermal and deformational energy of the target and C60. This latter energy is subsequently transformed to final kinetic and further thermal energy