Experimental study of the excitation mechanisms in Heq+-fullerene collisions

In a recent study on Oq+ (1 ≤ q ≤ 7) collisions with C60, we presented fragmentation patterns dominated by electron capture processes. We now investigate the remaining important interaction mechanisms: electronic excitation due to ion-electron interactions and vibrational excitation due to ion-nucleus interactions as well as the possible electronic-vibrational coupling. Using Heq+ (q = 1, 2) projectiles we observed a decrease of evaporation peaks (ascribed to vibrational excitation) with increasing collision energy (2 keV * q ≤ Ekin ≤ 100 keV * q) and an increase of small fragments Cn+ as well as parent ions C60q+ (attributed to electronic excitation). The additional potential energy carried by He2+ (with respect to He+) was found to cause an extra fragmentation and ionization respectively in the low and high projectile energy regimes. (orig.)