Strong projectile dependence of C60fragmentation by MeV-energy heavy ions

Experimental results are presented for ionization and fragmentation of C 60 bombarded by various projectile ions of H + , Li 1,2+ , B 1,2+ , O 2+ , Si 1,2+ , Ag 2+ and Au 3+ with velocities 0.9 v 0 -3 v 0 ( v 0 : Bohr velocity). Mass distributions of light fragment ions C n + ( n = 1-12) are found to change drastically depending on the projectile species or atomic number Z p . The result indicates that multifragmentation of C 60 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 C 60 , energy deposition to C 60 is calculated, and internal energy and ionization degree of C 60 after collisions are estimated. It is concluded that the final fragment pattern is governed by the internal energy.