Evolution of Nucleus-Nucleus Collision Mechanisms from the Barrier to Beyond the Fermi Energy

Abstract

Systematic measurements of linear-momentum-transfer distributions have been performed for $^{6}\mathrm{Li}$-, $^{12}\mathrm{C}$-, and $^{14}\mathrm{N}$-induced reactions on $^{238}\mathrm{U}$ at energies up to $\frac{E}{A}=45$ MeV. The data establish a limitation in linear momentum transfer at 200 MeV/c per projectile nucleon, which occurs near a beam energy of $\frac{E}{A}\ensuremath{\approx}35$ MeV. This limitation is interpreted in terms of precompound particle emission, and calculations based on this concept reproduce the global energy dependence of the data.