Impact-parameter-dependent multifragmentation ofC60in charge-changing collisions with2‐MeVC+ions

Abstract

Multifragmentation of C{sub 60} was investigated for 2 MeV C{sup +} projectile ions by means of a time-of-flight triple coincidence technique. Fragment ions and secondary electrons were measured simultaneously in coincident with charge-selected outgoing projectile particles scattered into forward angles smaller than 1.0 mrad. Fragment ion distributions were found to change remarkably with respect to the scattering angle {theta}. Relationships between {theta} and the impact parameter b measured from the center of C{sub 60} were calculated classically. We found evidently that small-size fragment ions are produced only from cage-penetration collisions, while intact parent ions and their daughter ions are created in collisions nearby but outside a C{sub 60}. Furthermore, charge state distributions of prefragmented C{sub 60}{sup r+} ions and correlated fragment ion pairs were both found to be essentially independent of {theta} when plotted for individual C{sub m}{sup +} ions of fixed size. These results indicate that the production of a size-fixed specific ion may be restricted to a certain impact parameter region in which equivalent electronic energies are deposited irrespectively of {theta}. This was confirmed also from our calculation of the energy deposition as a function of b carried out using the local density approximation.