On the production of superheavy elements

Since the discovery of Deformed Superheavy Nuclei (1983–85) a bridge connects the island of SHE to known isotopes of lighter elements. What we know experimentally and theoretically on the nuclear structure of SHE is reported in a first section. The making of the elements, with an analysis of production cross sections, and the macroscopic limitation to Z=112+ε is presented in a second section. The break-down of fusion cross sections in the ‘Coulomb Falls’ within a range of about 10 elements is introduced as the universal limiting phenomenon. How the nuclear structure of the collision partners modifies the on-set of this limitation is presented in Section 3. Reactions induced by deformed nuclei are pushed by side collisions to higher excitation energies (4n- and 5n-channels), whereas reactions driven by the cluster-like, closed-shell nuclei, ²⁰⁸₁₂₆Pb and ¹³⁸₈₂Ba, are kept at low excitation energies (1n- and 2n-channels). The on-set of production limitation for deformed collision partners is moved to smaller effective fissilities x=0.68⩽0.72, whereas for spherical clusters the on-set is delayed x=0.76⩾0.72 and x=0.79⩾0.72 for ¹³⁸Ba and ²⁰⁸Pb, respectively. An outlook, what remains to be studied in the future, ends the article. To cite this article: P. Armbruster, C. R. Physique 4 (2003).