Charge-pickup processes in relativistic heavy-ion reactions

We have measured a complete isotope distribution of projectile-like nuclear-charge pickup products, formed by bombarding a ¹⁷Al target with 790A MeV ¹²⁹Xe ions. The shape of the cross-section distribution indicates a dominant influence of evaporation processes during the formation of the final cesium fragments observed, thus masking to a large extent the primary processes involved in the charge exchange. We can show, however, that an intranuclear-cascade-plus-evaporation calculation can reproduce the observed yields, and that the effect of Δ-formation during the first stage of the reaction is visible even in the inclusive cross sections. The same model can explain the strong increase in total charge-pickup cross sections with increasing projectile mass noted previously by other authors. It is therefore not necessary to invoke coherent processes to explain this increase as has been suggested previously.