The charge transfer of the RNA base uracil by means of ${\mathrm{C}}^{q+}$ ions $(q=2–4)$ has been studied theoretically by means of ab initio quantum-chemistry molecular methods followed by a semiclassical dynamical treatment. The charge-transfer process appears to be highly anisotropic. The theoretical cross sections show different behavior with a strong influence of the electronic structure and charge of the ${\mathrm{C}}^{q+}$ projectile and can be correlated positively with previous experimental studies on the ionization and fragmentation processes in the ${\mathrm{C}}^{q+}$-Uracil collision.

The anisotropy effect in charge transfer induced by collision of ${\mathrm{C}}^{q+}$ ions $(q=2,4)$ on uracil has been studied theoretically using ab initio molecular methods followed by a semiclassical dynamical treatment. The process depends strongly on the orientation of the projectile in the ${\mathrm{C}}^{4+}+\text{uracil}$ reaction and is favored around the perpendicular direction. The effect is weaker in the ${\mathrm{C}}^{2+}+\text{uracil}$ collision system where cross-sections remain low.

The collisional system ${\mathrm{Si}}^{4+}+\mathrm{He}$ has been studied over a range of mean relative ion kinetic energy going from ${10}^{-2}$ to ${10}^2\mathrm{e}\mathrm{V}/\mathrm{a}\mathrm{m}\mathrm{u}.$ In the low-energy range, a time-dependent wave-packet approach is used both in the diabatic and the adiabatic representation using two different propagator techniques. The agreement between the two sets of results assess the accuracy of the present numerical approach. Above 2.5 eV/amu., a semiclassical eikonal calculation is performed, which includes the Coriolis couplings. Finally, the rate constant is calculated and compared with the other theoretical data as well as with the experimental value of [Fang and Kwong, Phys. Rev. A 59, 342 (1999)]. The present results confirm the order of magnitude of previous theoretical values.

Charge transfer in collisions of carbon ions on a thymine target has been studied theoretically in a wide collision range by means of ab initio quantum chemistry molecular methods. The process appears markedly anisotropic in the whole energy domain, significantly favoured in the perpendicular orientation. A specific decrease of the charge transfer cross sections at low collision energies may be pointed out and could induce an enhancement of the complementary fragmentation processes for collision energies down to about 10 eV, as observed for the low-electron fragmentation process. Such feature may be of important interest in ion-induced biomolecular radiation damage.