Probing the N=104 Midshell Region for the R Process Via Precision Mass Spectrometry of Neutron-Rich Rare-Earth Isotopes with the JYFLTRAP Double Penning Trap

We have performed high-precision mass measurements of neutron-rich rare-earth Tb, Dy and Ho isotopes using the Phase-Imaging Ion-Cyclotron-Resonance technique at the JYFLTRAP double Penning trap. We report on the first experimentally determined mass values for ^169Tb, ^170Dy and ^171Dy, as well as the first high-precision mass measurements of ^169Dy and ^169-171Ho. For ^170Ho, the two long-lived ground and isomeric states were resolved and their mass measured, yielding an isomer excitation energy of E_exc=150.8(54) keV. In addition, we have performed independent crosschecks of previous Penning-trap values obtained for ^167, 168Tb and ^167, 168Dy. We have extended the systematics of two-neutron separation energies to the neutron midshell at N=104 in all of the studied isotopic chains. Our updated and new mass measurements provide better mass-related constraints for the neutron-capture reaction rates relevant to the astrophysical rapid neutron capture (r) process. The r-process abundances calculated with the new mass values seem to produce a steeper minimum at A=170 and differ by around 15-30% from the abundances computed with the Atomic Mass Evaluation 2020 values.