Strong projectile dependence of C-60 fragmentation 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,Li-2+, B-1,B-2+, O2+, Si- 1,Si-2+, Ag2+ and Au3+ With velocities 0.9 upsilon(0)-3 upsilon(0) (upsilon (0): Bohr velocity). Mass distributions of light fragment ions C-n(+) (n = 1-12) are found to change drastically depending on the projectile species o r 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 ionizatio n is apr to occur and lighter fragment ions are produced predominantly. Ass uming the multifragmentation caused by penetration of the projectile throug h C-60, energy deposition to C-60 is calculated, and internal energy and io nization degree of C-60 after collisions are estimated. It is concluded tha t the final fragment pattern is governed by the internal energy.