Mass and half-life measurements of neutron-deficient iodine isotopes

Neutron-deficient iodine isotopes, 116I and 114I, were produced at relativistic energies by in-flight fragmentation at the Fragment Separator (FRS) at GSI. The FRS Ion Catcher was used to thermalize the ions and to perform highly accurate mass measurements with a Multiple-Reflection Time-of-Flight Mass-Spectrometer (MR-TOF-MS). The masses of both isotopes were measured directly for the first time. The half-life of the 114I was measured by storing the ions in an RF quadrupole for different storage times and counting the remaining nuclei with the MR-TOF-MS. The measured half-life was used to assign the ground state to the measured 114I ions. Predictions on the possible α-decay branch for 114I are presented based on the reduced uncertainties obtained for the Qα-value. Systematic studies of the mass surface were performed with the newly obtained masses, showing better agreement with the expected trend in this mass region.peerReviewe

New developments for isochronous mass measurements of short-lived nuclei

The combination of the in-flight separator FRS and the storage-ring ESR at GSI offers unique possibilities for high accuracy mass and lifetime measurements of bare and few-electron fragments. Operating the ESR in the isochronous mode allows for measurements of revolution frequencies of stored ions without cooling. Isochronous Mass Spectrometry (IMS) can be applied to fragments with half-lives as short as several tens of microseconds. Newly developed magnetic rigidity tagging increases the resolving power of IMS to about 500000. IMS can be used to measure masses of nuclei with rates even lower than one ion per day, a property also needed for the purpose of the ILIMA project at the future facility FAIR. © 2007 American Institute of Physics

Discovery and investigation of heavy neutron-rich isotopes with time-resolved Schottky spectrometry in the element range from thallium to actinium

238U projectile fragments have been created at the entrance of the fragment separator FRS, spatially separated in flight within 0.45 μs and injected into the storage-cooler ring ESR at 7.9 Tm corresponding to about 70% light velocity. Accurate new mass values and lifetime information of the stored exotic nuclei in the element range from platinum to uranium have been obtained with single-particle Schottky spectrometry. In this experiment the new isotopes of 236Ac, 224At, 221Po, 222Po, and 213Tl were discovered. The isotopes were unambiguously identified and their masses measured. In addition, the time-correlated data have provided information on the lifetime of the new nuclides. The discovery of isotopes along with accurate mass measurement has been achieved for the first time at the FRS-ESR facility. The results will contribute to the knowledge of the decay products from the r-process nuclei and enable a crucial test of the predictive power of modern nuclear mass and half-life models

New results on mass measurements of stored neutron-rich nuclides in the element range from Pt to U with the FRS-ESR facility at 360-400MeV/u

Masses of 238U projectile fragments have been measured with time-resolved Schottky Mass Spectrometry (SMS) at the FRS-ESR facility at GSI. The exotic nuclei were created in the production target at the entrance of the fragment separator FRS, spatially separated in flight and injected into the storage-cooler ring ESR at about 70% light velocity. This means the ions were mainly bare or carried only a few electrons, e.g., the population of Li-like ions was below 1% for Pt fragments. Accurate newmass values of 33 neutron-rich, stored exotic nuclei in the element range from platinum to uranium have been obtained for the first time. In total more than 150 nuclides including references with well-known masses have been covered in this large-area SMS measurement. A novel data analysis has been applied which reduces the systematic errors by taking into account the velocity profile of the cooler electrons and the residual ion-optical dispersion in this part of the storage ring. The experiment, the data analysis, and the mass values are presented. The experimental data are compared with theoretical predictions demonstrating systematic deviations of up to 1500 keV from modern mass models