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Direct mass measurements of neutron-deficient nuclides around the N = 50 shell closure below 100Sn were performed at the FRS Ion Catcher (FRS-IC) at GSI, Germany. The nuclei were produced by projectile fragmentation of 124Xe, separated in the fragment separator FRS and delivered to the FRS-IC. The masses of 14 ground states and two isomers were measured with relative mass uncertainties down to 1 × 10 − 7 using the multiple-reflection time-of-flight mass spectrometer of the FRS-IC, including the first direct mass measurements of 98Cd and 97Rh. A new Q EC = 5437 ± 67 keV was obtained for 98Cd, resulting in a summed Gamow-Teller (GT) strength for the five observed transitions (0 + ⟶ 1 +) as B (GT) = 2.94 − 0.28 + 0.32. Investigation of this result in state-of-the-art shell model approaches accounting for the first time experimentally observed spectrum of GT transitions points to a perfect agreement for N = 50 isotones. The excitation energy of the long-lived isomeric state in 94Rh was determined for the first time to be 293 ± 21 keV. This, together with the shell model calculations, allows the level ordering in 94Rh to be understood. [ABSTRACT FROM AUTHOR]

The ion-optical design of a multiple reflection time-of-flight mass spectrometer and isobar separator (MR-TOF-MS) is presented. The MR-TOF-MS has been developed for the research with exotic nuclides at accelerator facilities and has been designed to provide a mass resolving power (FWHM) exceeding 300,000 and a mass accuracy of down to 10 −7 . High-performance axially symmetric four-electrode gridless ion mirrors have been developed and optimized for the device. In addition, the MR-TOF-MS comprises several further novel ion-optical elements such as an isochronous post-analyzer reflector and an energy bunching and deceleration system for ion injection into an accumulation trap. The device has been built and commissioned and shows superb performance characteristics in accordance with the design criteria. [ABSTRACT FROM AUTHOR]