Mass Measurements of Neutron-Deficient Lanthanides around the Neutron Shell Closure N=82 at TITAN

by Marilena Lykiardopoulou (University of British Columbia / TRIUMF)

Wednesday 19 Jun 2019, 14:15 → 15:00 Europe/Zurich

Neutron-deficient lanthanides are a subject of interest from many perspectives. Not only can they provide information about the neutron shell closure at N=82, but they can also indicate where the proton drip-line lies in this region. In addition, since some lanthanides are anchors of alpha decay chains, they can give valuable information about the progenitors and intermediate nuclei. 

To this end, the masses of neutron-deficient lanthanides, with atomic numbers 150-157, were measured at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN). TITAN specializes in high-precision mass measurements and in-trap decay spectroscopy, which recently was equipped with a Multi-Reflection Time of Flight mass spectrometer (TITAN MR-ToF) that can be used either as an isobaric separator or a mass spectrometer. For this experiment, radioactive ion beam from the TRIUMF’s Isotope Separator and Accelerator (ISAC) was used to trap and measure neutron deficient lanthanides in TITAN’s Multi-Reflection Time of Flight mass spectrometer. Mass-selective re-trapping was used for the first time with radioactive beam and resulted in suppression of the background by four orders of magnitude. This allowed the measurement of the masses of neutron-deficient lanthanides with atomic numbers 150-157. From the nuclides measured, the masses of 150Yb, 153Yb, 150Tm were measured for the first time, while the uncertainties of the masses of 151Yb, 152Yb and 151Tm were improved. The impact of these mass measurements to the evolution of the neutron shell closure at N=82 as well as ongoing upgrades at the TITAN beamline will be discussed.