Cq+-induced excitation and fragmentation of uracil:: effects of the projectile electronic structure

Ionization and fragmentation of the RNA base uracil (C4H4N2O2) by means of Cq+ ions (q = 1-6) has been studied for ion kinetic energies ranging from ;2 to 120 keV. Whereas for Cq+ (q = 1, 3, 4, 5, 6) very similar fragmentation yields are observed which increase with the projectile velocity v, C2+ ions not only induce a fundamentally different fragmentation pattern but also lead to a decrease of fragmentation with ion velocity v. At low velocities, even almost complete fragmentation is observed. Our findings can be explained by differences in the electronic structures of the Cq+ ions as well as by employing the electronic stopping model previously applied to ion-fullerene interactions.