Direct high-precision mass spectrometry of superheavy elements with SHIPTRAP

Direct mass measurements in the region of the heaviest elements were performed with the Penning-trap mass spectrometer SHIPTRAP at GSI Darmstadt. Utilizing the phase-imaging ion-cyclotron-resonance mass-spectrometry technique, the atomic masses of No251 (Z=102), Lr254 (Z=103), and Rf257 (Z=104) available at rates down to one detected ion per day were determined directly for the first time. The ground-state masses of No254 and Lr255,256 were improved by more than one order of magnitude. Relative statistical uncertainties as low as δm/m≈10-9 were achieved. Mass resolving powers of 11 000 000 allowed resolving long-lived low-lying isomeric states from their respective ground states in No251,254 and Lr254,255. This provided an unambiguous determination of the binding energies for odd-A and odd-odd nuclides previously determined only indirectly from decay spectroscopy.