Penning-trap mass measurements of neutron-deficient Rb and Sr isotopes

The Penning-trap mass spectrometer ISOLTRAP installed at the on-line mass separator ISOLDE 2 at CERN has been used for mass determination of 75-87Rb and 78-83,87Sr. Ions are captured in a Penning trap and their cyclotron frequency ωc =(q/m)B in the trapping field B is measured. Ratios of these frequencies lead to the determination of the atomic mass of these isotopes. A resolving power of typically m/Δm=106 and an accuracy y of δm∼10 keV is obtained. The mass of 78Sr is measured for the first time, in most cases, the mass values of the other isotopes are significantly improved. The experimental masses are compared with theoretical predictions. (orig.)