DIRECT MASS MEASUREMENTS OF UNSTABLE RARE-EARTH ISOTOPES WITH THE ISOLTRAP MASS-SPECTROMETER

Direct mass measurements of neutron deficient rare earth isotopes in t he vicinity of Gd-146 were performed for the first time with the Penni ng trap mass spectrometer ISOLTRAP at ISOLDE/CERN. Since ISOL-faciliti es deliver these isotopes with a large amount of isobaric contaminatio n, these measurements became possible only after the installation of a new cooler trap which acts as an isobar separator. To date more than 40 isotopes of the elements Pr, Nd, Pm, Sm, Eu, Dy, and Ho have been m easured with a typical accuracy of delta m approximate to 14 keV. Some of these isotopes provide an important anchor for many other isotopes linked by known Q-values.