Physics Colloquium, Michael Block, GSI Helmholtzzentrum Fur Schwerionenforschung Darmstadt, Germany

Abstract:

Presently we know 118 elements in the Periodic table. The heaviest of these owe their existence to nuclear shell effects providing additional stability against spontaneous fission. Theoretical models even predict an island of stability of long-lived superheavy elements for Z ≈ 114 and N ≈ 184. Such elements feature atomic and nuclear properties that may differ drastically from lighter ones. Theoretical models predict, for example, an appreciable central depression in the deformed proton density distribution of very heavy nuclei. The atomic and chemical properties of the heaviest elements are also strongly influenced by relativity and quantum electrodynamics effects. However, the experimental investigation of the heaviest elements is challenging as they can only be produced artificially with accelerators in small quantities of few atoms that are often short-lived.

Nonetheless, pioneering experiments performed at the GSI Darmstadt, Germany have demonstrated that even Penning trap mass spectrometry and laser spectroscopy are feasible in very heavy elements with minute yield and rather unknown properties. In recent years we performed direct mass measurements of nobelium- and lawrencium isotopes with the Penning trap SHIPTRAP that allowed us to map nuclear shell effects for Z = 102,103 and N = 152. These activities have recently been complemented by laser spectroscopy experiments in which we get access to observables that reflect the nuclear size and shape. In my presentation I will present the status of both experimental activities and discuss select recent results.