Understanding the strong force and its consequences for nuclear structure is one of the major goals of contemporary nuclear physical research.
This is being best performed at the limits of existence, i.e. in the regions of extreme neutron-to-proton ratios and with superheavy elements (SHE). The experimental investigation of SHE, i.e., nuclei with atomic numbers Z≥ 104, addresses fundamental physical and chemical questions. SHE owe their existence solely to nuclear shell stabilization effects. Beyond the closed spherical shells at Z=82 and N=126, theoretical calculations suggest the next shell closures at Z=114, 120, or 126, and N=172 or, more frequently, N=184. On the way to this long-sought "island of stability of superheavy elements", deformed shell closures have been identified at N=152, Z=108 and N=162. Over the past decades, intense research at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, six new elements with Z=107-112 were discovered, and more recently, element 114 was observed.The location in N and Z of the next spherical shell closure, however, is still open. Therefore, experiments on the synthesis of new elements with Z>118 are currently being prepared, supported by studies of nuclear reaction mechanisms.
Obtaining a fundamental understanding of the nuclear structure through decay spectroscopic studies of excited, especially of isomeric states will assist in pin-pointing the location of proton- and neutron shell-closures. Highly accurate mass measurements with Penning traps complement the broad research program, which will yet be expanded to laser spectroscopic measurements in the near future.