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 + epsilon 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, Pb-208(126) and Ba-138(82), 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 less than or equal to 0.72, whereas for spherical clusters the on-set is delayed x = 0.76 greater than or equal to 0.72 and x = 0.79 greater than or equal to 0.72 for Ba-138 and Pb-201, respectively. An outlook, what remains to be studied in the future, ends the article. (C) 2003 Academie des sciences. Published by Editions scientifiques et medicales Elsevier SAS. All rights reserved.