Nuclear transparency and the onset of strong absorption regime in the 12C+24Mg system

The elastic scattering of 12C+24Mg has been studied by means of a phase-shift analysis of 21 angular distributions ranging from Elab=16MeV up to Elab=40MeV. A tri-dimensional plot of the reflection coefficient of the S-matrix as a function of the angular momentum and the energy shows a well defined region of energy which separates two regimes: strong absorption for higher energies and the so called "anomalous transparency regime", recently observed in this system at low energies. The Argand diagrams of the S-matrix in angular momentum space also present very contrasting behaviours in the two regions with very rapidly varying phases in the low energy region, which we associate with a parity dependent term in the S-matrix directly related to significant coupling to the elastic transfer of a 12C nucleus.