Superheavy elements - A probe for nuclear matter at the extremes

Abstract

The spherical shell stabilised superheavy elements (SHE) predicted at the extreme of high Z and A are a nuclear structure phenomenon. They owe their existence to shell effects, an energy contribution of quantum mechanical origin to the nuclear potential, without which they would not be bound. Experimental activities in this field, apart from attempts to directly synthesise new elements, have to investigate reaction mechanism studies and, in particular, they have to pursue nuclear structure investigations to study the development of single particle levels towards the expected gaps for the proton (at Z = 114, 120 or 126) and neutron (at N = 184) shell closures in the region of spherical SHE. A number of exciting results in terms of the synthesis of new elements have reached the border of that region. In particular the results obtained at the Flerov Laboratory of Nuclear Reactions (FLNR) for a rich number of decay patterns for 48Ca induced reactions on actinide targets have by now been confirmed for reactions on 238U, 244Pu and 248Cm at GSI, and on 242Pu at LBNL. In recent years the development of efficient experimental set-ups, including separators and advanced particle and photon detection arrangements, allowed for more detailed nuclear structure studies for nuclei at and beyond Z = 100. Among the most interesting features is the observation of K-isomeric states. The heaviest example for such a structure feature was found in 270Ds. In a recent experiment the knowledge on this nucleus and its decay products could be largely extended.