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

The β-decay half-lives of 94 neutron-rich nuclei 144−151Cs, 146−154Ba, 148−156La, 150−158Ce, 153−160Pr, 156−162Nd, 159−163Pm, 160−166Sm, 161−168Eu, 165−170Gd, 166−172Tb, 169−173Dy, 172−175Ho, and two isomeric states 174mEr, 172mDy 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 58Ce, 59Pr, 60Nd, and 62Sm, and N=105 for 63Eu, 64Gd, 65Tb, and 66Dy. 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.