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 ²⁵¹No ($Z=102$), ²⁵⁴Lr ($Z=103$), and ²⁵⁷Rf ($Z=104$) available at rates down to one detected ion per day were determined directly for the first time. The ground-state masses of ²⁵⁴No and 255,256Lr 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 251,254No and 254,255Lr. This provided an unambiguous determination of the binding energies for odd-A and odd-odd nuclides previously determined only indirectly from decay spectroscopy.