Experimental and theoretical study of ionization and fragmentation ofC60by fast-proton impact

Abstract

We have studied the ionization and fragmentation of ${\mathrm{C}}_{60}$ in collisions with protons and deuterons at impact energies of 50–300 keV. The time-of-flight spectra of all fragment ions were measured in coincidence with one of the emitted electrons. The cross sections of multiple ionization as well as relative yields of even-mass fullerene-type ions of various charges are deduced from experimental spectra. A theoretical model based on a statistical approach is developed for the explanation of the experimental data. The model describes the $p+{\mathrm{C}}_{60}$ collision as proceeding in three steps: (i) energy deposition by the projectile, (ii) emission of prompt electrons, and (iii) ${\mathrm{C}}_2$ evaporation and delayed electron emission. The observed distribution of fragment fullerenes indicates that the delayed electron emission is an essential part of the process and that it occurs before the equilibration is achieved.