Recent results on multiple ionization and fragmentation of negatively charged fullerene ions by electron impact |
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Authors: | D Hathiramani P Scheier E Salzborn |
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Institution: | (1) Institut für Kernphysik, University of Giessen, Giessen, D-35392, Germany;(2) Institut für Ionenphysik, University of Innsbruck, Innsbruck, A-6020, Austria |
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Abstract: | Employing the dynamic crossed-beams technique, the absolute cross sections of the electron-impact multiple ionization and fragmentation of mass-selected negatively charged fullerene ions C m ? → C m?n 2+ (m=60, 70, 84; q=1, 2, 3; n=0, 2, 4) were measured. The electron energy varied from the respective threshold up to 1 keV. A scaling law was observed for the cross-section magnitude as a function of the fullerene size m and the charge state q of product ions. The data indicate that different mechanisms account for the detachment of an extra electron from the negatively charged fullerene and the formation of a positively charged ion, respectively. Moreover, the multiple ionization of a fullerene anion is found to be a sequential process. A novel ionization mechanism is proposed which might be expected to be valid for all negatively charged molecular or cluster ions able to shield the attached electron from the incident electron. |
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