Capture dynamics in collisions between fullerene ions and rare gas atoms

The collision energy dependence of capture in collisions between C-60(+) io ns and small rare gas atoms (He, Ne) is studied in detail and compared with the results of classical molecular dynamics simulations. Additional insigh t is obtained on the dynamics of the collisions by also studying the kineti c energy loss of the projectile ions. Two capture mechanisms are found for He collisions: penetration of a six-membered ring with no significant cage distortion and scattering from a C-2 unit followed by deflection inside the cage. Good agreement is found with the simulations. Ne capture appears to be mainly the product of collisions with ring-structures on the cage follow ed by bond-breaking and insertion via a window mechanism. The very low thre shold energy for Ne capture by fullerene ions (10 eV), reported previously, is attributed to the presence of highly excited, deformed fullerene ions i n the beam. A second, higher threshold is found which is in better agreemen t with other experiments reported in the literature. The simulations of the Ne collisions do not give such good agreement as the He simulations. We at tribute this to a too low value of the screening parameter used in the Ne-C potential. (C) 1998 Elsevier Science B.V. All rights reserved.