AUTHOR=Xian W. , Rosenbusch M. , Phong V. H. , Wada M. , Schury P. , Hou D. , Takamine A. , Chen S. , Niwase T. , Hirayama Y. , Ishiyama H. , Iimura S. , Ito Y. , Kojima T. M. , Kimura S. , Liu J. , Lee J. , Michimasa S. , Miyatake H. , Moon J. Y. , Mukai M. , Nishimura S. , Naimi S. , Sonoda T. , Watanabe Y. X. , Wollnik H. , Yan S. 

TITLE=Atomic mass measurements of neutron-rich nuclides on the path to 78Ni with a β-TOF-equipped MRTOF device

JOURNAL=Frontiers in Physics

VOLUME=Volume 13 - 2025

YEAR=2025

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2025.1644477

DOI=10.3389/fphy.2025.1644477

ISSN=2296-424X

ABSTRACT=We report atomic mass measurements of the unstable nuclides 73−75Ni, 73−78Cu, and 74−78Zn, which have been accomplished using multi-reflection time-of-flight mass spectrometry combined with new technical developments to resolve challenges for exotic-isotope identification and selection. The isotopes were produced in-flight at the RIKEN’s Radioactive Ion Beam Facility and delivered to the combined gas cell and multi-reflection system installed downstream of the ZeroDegree spectrometer. The incoming high-energy beam was energy-degraded and subsequently stopped in a helium gas cell. The energy degrader thickness was optimized using a new method that employs signals from plastic scintillators located upstream and downstream of the helium-filled gas cell. Extracted isotopes of interest were mass-selected by the in-MRTOF deflector method, for which we discuss simultaneous selection of multiple isobar chains. The ions of interest were identified unambiguously using β-decay-correlated mass measurements for the first time, which is demonstrated for 78Zn. The new mass values are compared with literature values and recent measurements performed at JYFLTRAP and ISOLTRAP, where a generally good agreement is observed.