Nature463, 785-788 (11 February 2010) | doi:10.1038/nature08774; Received 21 October 2009; Accepted 17 December 2009
Direct mass measurements above uranium bridge the gap to the island of stability
M. Block1, D. Ackermann1, K. Blaum2, C. Droese3, M. Dworschak1, S. Eliseev2, T. Fleckenstein4, E. Haettner4, F. Herfurth1, F. P. Heßberger1, S. Hofmann1, J. Ketelaer5, J. Ketter2, H.-J. Kluge1,6, G. Marx3, M. Mazzocco7, Yu. N. Novikov1,8, W. R. Plaß1,4, A. Popeko9, S. Rahaman10,13, D. Rodríguez11, C. Scheidenberger1,4, L. Schweikhard3, P. G. Thirolf12, G. K. Vorobyev1 & C. Weber10,13
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt, Germany
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
The mass of an atom incorporates all its constituents and their interactions1. The difference between the mass of an atom and the sum of its building blocks (the binding energy) is a manifestation of Einstein’s famous relation E = mc2. The binding energy determines the energy available for nuclear reactions and decays (and thus the creation of elements by stellar nucleosynthesis), and holds the key to the fundamental question of how heavy the elements can be. Superheavy elements have been observed in challenging production experiments2, 3, 4, but our present knowledge of the binding energy of these nuclides is based only on the detection of their decay products. The reconstruction from extended decay chains introduces uncertainties that render the interpretation difficult. Here we report direct mass measurements of trans-uranium nuclides. Located at the farthest tip of the actinide species on the proton number–neutron number diagram, these nuclides represent the gateway to the predicted island of stability. In particular, we have determined the mass values of 252-254No (atomic number 102) with the Penning trap mass spectrometer SHIPTRAP5. The uncertainties are of the order of 10keV/c2 (representing a relative precision of 0.05p.p.m.), despite minute production rates of less than one atom per second. Our experiments advance direct mass measurements by ten atomic numbers with no loss in accuracy, and provide reliable anchor points en route to the island of stability.