N/Zequilibration in damped collisions induced byE/A=8.5 MeVNi58andNi64onU238

Nuclide distributions have been measured for damped collision products formed in the reaction of E/A=8.5 MeV ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ ions with ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. The data demonstrate that in these very asymmetric systems the evolution of the nucleon-exchange process as a function of energy loss depends strongly on the N/Z value of the projectile and the corresponding gradient in the potential-energy surface. Comparison of the data with transport model calculations shows qualitative agreement with the N and Z centroids, variances, and correlation coefficients. However, absolute discrepancies exist which suggest the need for improvement in the model.