Multifragmentation ofC60by fastLi0atoms andLi1–3+ions in electron loss and capture collisions

Abstract

Fragmentation and ionization of ${\mathrm{C}}_{60}$ are studied for electron capture and loss collisions of fast ${\mathrm{Li}}^{q+}$ $(q=0--3)$ projectiles at a velocity $v=3.38$ a.u. Production cross sections are measured for all observed ions by a time-of-flight method in coincidence with outgoing projectile charge states k. Multifragmentation as well as multiple ionization are observed strongly even for the neutral projectiles. Total production cross sections, summed over all observed ions, are found to be the same order of magnitude for $q<~2,$ indicating that the fragmentation is induced in close collisions, i.e., by penetration of the incident particles through the ${\mathrm{C}}_{60}$ cage. Also, it is found that the total fragmentation cross sections as a function of k show nearly the same shape as the equilibrium charge state distributions (CSD) measured for other condensed materials. This certainly implies that a memory for the initial charge state q is nearly lost while penetrating the cage, and the final CSD is approximately equilibrated.