Mass measurements of neutron-rich isotopes near N=20 by in-trap decay with the ISOLTRAP spectrometer

The masses of $^{34}$Si, $^{33,34}$Mg, and $^{34}$Al have been measured with the ISOLTRAP Penning-trap spectrometer at ISOLDE/CERN. The results are in agreement with previous mass measurements and uncertainties have been decreased. The mass of $^{34}$Al was determined in two configurations, one following direct production by the ISOLDE facility, favoring the 4− state, expected to be the ground state, second by in-trap decay of $^{34}$Mg, followed by recoil-ion trapping, favoring the production of the isomeric 1+ state. A position-sensitive detector was used to clean the ToF-ICR resonance. In addition, the mass of the refractory doubly magic $^{34}$Si nucleus was directly measured, using the in-trap decay of $^{34}$Mg, following two sequential recoil-ion captures. The approach, challenges and conclusions are discussed.