TRACKS IN TI AND ZR FROM MEV C-60(+) IMPACTS

Damage tracks recently have been observed by transmission electron mic roscopy (TEM) in crystalline targets of Ti and Zr that have been bomba rded by 18 MeV C-60(+) ions. Although enhanced damage has been seen in Ti from MeV/amu Pb and U ion bombardment, the track diameters from C- 60 irradiation are much larger, i.e., 200 Angstrom vs 50 Angstrom. In this note I show that the phenomenon is somewhat different in the case of large molecular ions than for energetic single ions - even though the amount of energy deposition is similar in the two cases. The model presented here not only explains the new observations quantitatively but also provides a way to estimate how the damage might change for ot her cluster energies and species.