Evolution from deep inelastic transfer to quasi-fission

Recoil techniques have been used to study the evolution of the features of four-charge transfer reactions in ¹⁴⁸Sm targets when the mass and energy of the projectile are varied. Beams of ⁶³Cu and ⁵⁶Fe were used, and their energies were chosen in order to be equal to 1.2B and 1.5B for both projectiles, B being the interaction barrier. The residual nuclei ^149gTb, ¹⁵⁰Dy and ¹⁵¹Dy were identified by their radioactive properties. This study has shown a continuous evolution of the characteristics of the c.m. angular distributions, especially the position of the maxima, from typical deep inelastic transfer to quasi-fission features, when the value of $\text{E}\text{B}$ decreases. For equal values of this ratio, no difference was observed between Fe and Cu induced reactions. The c.m, energies corresponding to the maximum cross section increases when the incident energy is increased, for a given projectile. At low incident energies (igE = 1.2B), the relative motion appears to be completely damped, and the distance of the two nuclei after separation is equal to about 5 fm. At higher incident energies, the c.m. energy is significantly higher. This may mean that the relative motion is not completely damped. Part of the effect may be explained by the differences in the angular momenta involved in the reaction.