Searching for the origin of the rare-earth peak with precision mass measurements across Ce-Eu isotopic chains

A nuclear mass survey of rare-earth isotopes has been conducted with the Canadian Penning Trap mass spectrometer using the most neutron-rich nuclei thus far extracted from the CARIBU facility. We present a collection of 12 nuclear masses determined with a precision of <= 10 keV/c(2) for Z = 58-63 nuclei near N = 100. Independently, a detailed study exploring the role of nuclear masses in the formation of the r-process rare-earth abundance peak has been performed. Employing a Markov chain Monte Carlo (MCMC) technique, mass predictions of lanthanide isotopes have been made which uniquely reproduce the observed solar abundances near A = 164 under three distinct astrophysical outflow conditions. We demonstrate that the mass surface trends thus far mapped out by our measurements are most consistent with MCMC mass predictions given an r process that forms the rare-earth peak during an extended (n, gamma) reversible arrow (gamma, n) equilibrium.

Automated summary

The article describes a nuclear mass survey of rare-earth isotopes conducted with the Canadian Penning Trap mass spectrometer, focusing on the role of mass in the formation of the r-process rare-earth abundance peak, and using MCMC technique for mass predictions. The results demonstrate that the mass surface trends are most consistent with MCMC mass predictions.