Delayed emission of electrons from C60 following energetic impact against graphite |
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Authors: | Chahan Yeretzian Robert L Whetten |
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Institution: | 1. Department of Chemistry and Biochemistry, University of California, 90024-1569, Los Angeles, CA, USA
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Abstract: | The yield of C 60 + ions reflected from the surface of graphite is found to be a bimodal function of the energy of impact. Below 140 eV (6 km/s), the yield decreases with energy and the scattering time-of-flight peak is sharp. Above 170 eV, the yield increases, but the peak is broad and asymmetric, corresponding to delayed electron emission from an impact-heated, neutralized cluster. There is also evidence for fragmentation to C58 and C56. The emission process may be analogous to that reported for scattered C 60 ? . Application of statistical rate theory to either observation (C 60 ± ) gives an estimated 25–30 percent transfer of impact energy into cluster internal modes. The decreasing yield at highest energies (>400 eV) may result from adhesion processes (C60-surface bonding) that could also account for the absence of delayed electron emission in C60-silicon collisions. |
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