Incomplete fusion in 12C+160Gd collisions

Abstract

The mechanism of the production of fast α-particles in 12C induced reactions was studied over a wide range of bombarding energies (7.5–16.7 MeV/A) by measuring α-γ coincidences. Absolute cross sections for 160Gd(12C, αxn)168−xEr and 160Gd(12C, 2αxn)164−xDy reactions, as well as inclusive α-particle production cross sections, have been determined. Depending on the bombarding energy, a fraction of 0.2–0.4 of the singles α-particles can be explained as resulting from incomplete fusion reactions (12C, α) and (12C, 2α) which correspond to a capture of “8Be” and “4He”, respectively. The remaining fragments of the projectile have, on the average, the beam-velocity energies and their angular distributions are forward peaked. Distributions of side-feeding to the yrast bands in the target-residue nuclei indicate that low partial waves are strongly hindered in the incomplete fusion reactions. The energy dependence of the cross sections for (12C, α) and (12C, 2α) incomplete fusion as well as for (12C, 3α) projectile breakup is given. A generalized concept of critical angular momentum which explains a competition between complete fusion, incomplete fusion and breakup reactions is proposed.