94 β -Decay Half-Lives of Neutron-Rich Cs 55 to Ho 67: Experimental Feedback and Evaluation of the r -Process Rare-Earth Peak Formation
J. Wu et al. -- 7 pags., 6 figs. ; The β-decay half-lives of 94 neutron-rich nuclei Cs144-151, Ba146-154, La148-156, Ce150-158, Pr153-160, Nd156-162, Pm159-163, Sm160-166, Eu161-168, Gd165-170, Tb166-172, Dy169-173, Ho172-175, and two isomeric states Er174m, Dy172m were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β-decay half-lives are observed at neutron-number N=97 for Ce58, Pr59, Nd60, and Sm62, and N=105 for Eu63, Gd64, Tb65, and Dy66. Features in the data mirror the interplay between pairing effects and microscopic structure. r-process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system. ; This work was carried out at the RIBF operated by RIKEN Nishina Center, RIKEN and RCNP, Osaka University. We also acknowledge the EUROBALL Owners Committee for the loan of germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors. Part of the WAS3ABi was supported by the Rare Isotope Science Project which is funded by the Ministry of Education, Science, and Technology (MEST) and National Research Foundation (NRF) of Korea (2013M7A1A1075764). This work was partially supported by KAKENHI (Grants No. 25247045), the RIKEN Foreign Research Program, the Spanish Ministerio de Ciencia e Innovacin (ContractsNo. FPA 2009-13377-C02 and No. FPA2011-29854-C04), the UK Science and Technology Facilities Council, the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, Contract No. DE-AC02-06CH11357, under the auspices of the NNSA of the U.S. DOE at Los Alamos National Laboratory under Contract No. DE AC52-06NA25396, the NASA Grant No. NNX10AH78G, the National Research Foundation Grant funded by the Korean Government (Grants No. NRF-2009-0093817, No. NRF-2015R1D1A1A01056918, No. NRF-2016 R1A5A1013277, and No. NRF-2013R1A1A2063017), and the Hungarian Scientific Research Fund OTKA Contract No. K100835. ; Peer Reviewed