| T.Grahn, A. Dewald, O. Möller, R. Julin, C. W. Beausang, S. Christen, I. G. Darby, S. Eeckhaudt, P. T. Greenlees, A. Görgen, K. Helariutta, J. Jolie, P. Jones, S. Juutinen, H. Kettunen, T. Kröll, R. Krücken, Y. Le Coz, M. Leino, A.-P. Leppänen, P. Maierbeck, D. A. Meyer, B. Melon, P. Nieminen, M. Nyman, R. D. Page, J. Pakarinen, P. Petkov, P. Rahkila, B. Saha, M. Sandzelius, J. Saren, C. Scholey, and J. Uusitalo |
A long standing prediction of nuclear models is the emergence of a region of long lived or even stable super heavy elements (SHE) beyond the actinides. These nuclei owe their enhanced stability to closed shells in the structure of both protons and neutrons. However, theoretical approaches to date disagree with each other and it is left to experiment to explore the shores of the “Island of Stability”.
The bulk of experimental effort so far has been focused on direct creation of SHE in heavy ion fusion reactions, leading to the production of elements up to Z=118. Recently, detailed spectroscopic studies of nuclei beyond fermium (Z=100) aimed at untangling the underlying single-particle structure of SHE have become possible. Here we report on an in-depth study of the heaviest nucleus studied in this manner to date, the nobelium isotope 254No with 102 protons and 152 neutrons. We find three excited structures, two of which are isomeric. One of these structures is firmly assigned to a two-proton excitation. These states are highly significant as their location is sensitive to single particle levels above the predicted Z=114 shell gap and thus provide a microscopic benchmark for nuclear models aimed at the understanding of SHE. |
