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

Abstract

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.