Excitation of 6Li above the breakup threshold in the 6Li + 208Pb system around the Coulomb barrier
Abstract.The excitation energy above the breakup threshold of the $\alpha + d/^6$Li system, after the interaction of 6Li nuclei with a 208Pb target, was deduced from the invariant mass of the $\alpha + d$ system. Data were collected with a large-solid-angle detector set-up at four beam energies around the Coulomb barrier. The excitation of the 6Li nucleus above the breakup threshold (1.47 MeV) has a quite similar behavior at each measured beam energy and angle; it is peaked at $\sim 1$ MeV above the threshold and shows an exponential decay on the high energy side, which is a clear signature of a direct breakup process. The experimental excitation energies are reproduced both in shape and absolute value by 1) fully quantum-mechanical Coupled-Channel calculations with coupling to discretized-continuum 6Li excitations, 2) semi-classical Coupled-Channel approach, where the relative motion is treated along a classical trajectory.