Strong projectile dependence of C₆₀fragmentation by MeV-energy heavy ions

Abstract

Experimental results are presented for ionization and fragmentation of C60 bombarded by various projectile ions of H+, Li1,2+, B1,2+, O2+, Si1,2+, Ag2+ and Au3+ with velocities 0.9v0-3v0 (v0: Bohr velocity). Mass distributions of light fragment ions Cn+ (n = 1-12) are found to change drastically depending on the projectile species or atomic number Zp. The result indicates that multifragmentation of C60 takes place at small impact parameters where the projectile nuclear charge is less screened. It is found that for heavy projectiles multiple ionization is apt to occur and lighter fragment ions are produced predominantly. Assuming the multifragmentation caused by penetration of the projectile through C60, energy deposition to C60 is calculated, and internal energy and ionization degree of C60 after collisions are estimated. It is concluded that the final fragment pattern is governed by the internal energy.