Study of the break-up channel in [superscript 11]Li+[superscript 208]Pb collisions at energies around the Coulomb barrier

Abstract

We present a study of ¹¹Li+²⁰⁸Pb collisions at energies around the Coulomb barrier (<em>E_lab</em> = 24.3 and 29.8 MeV), measured at the post-accelerated beam facility, ISAC II, at TRIUMF (Vancouver, Canada). A remarkably large yield of ⁹Li has been observed, a result that is attributed to the weak binding of the ¹¹Li nucleus. The angular distribution of this ⁹Li yield, relative to the elastic one, has been analysed in terms of first-order semiclassical calculations as well as four-body and three-body Continuum-Discretized Coupled-Channels (CDCC) calculations, based on a three-body and di-neutron model of the ¹¹Li nucleus, respectively. The calculations reproduce well the trend of the data and support the existence of a large concentration of B(E1) strength at very low excitation energies. The connection of this large B(E1) with a possible low-lying dipole resonance is discussed.