Oral Contribution

(Webpage)

 Title :

Modern Ruterford experiment : Tunneling of the most neutron rich nucleus ⁸He

 Abstract :

Nearly a hundred years ago the scattering of alpha particles (⁴He) from gold atoms by Rutherford led to the discovery of the atomic nucleus. Today exotic nuclear species with weak binding, unusual neutron/proton asymmetry and extended spatial distributions (halos), can be created and studied in the laboratory using short-lived radioactive ion beams [1]. Fusion reactions around the Coulomb barrier are not only a unique laboratory for probing the various aspects of multidimensional quantum tunnelling [2], but are also relevant to the synthesis of Super Heavy Elements and reactions of astrophysical interest.

In this talk, a modern variation of the Rutherford experiment where exotic ⁸He nuclei interact with a gold target was presented. The induced radioactivity, either from gold isotopes produced after the transfer of neutron(s) or from thallium isotopes resulting from fusion of the projectile and target, probes facets of the tunnelling of exotic nuclear matter. Employing a novel technique [3], precise measurements of the excitation functions involving 8He show that for this neutron-rich nucleus, neutron transfer modifies the tunnelling process in a different way to “normal” stable nuclei. A systematic isotopic comparison within the Helium chain show that the tunnelling of ⁸He is unusually similar to ⁶He, but as expected different from the stable tightly bound ⁴He [4]. These results shed light on the complex quantum phenomena of tunnelling of composite objects [5], that is of fundamental interest in fields ranging from molecular processes to transport in superconductors.