The abundance of elements heavier than iron produced via the astrophysical rapid-neutron-capture process depends sensitively on the atomic mass of the involved nuclei as well as the behavior of a few special types of nuclear isomers called “astromers.” High-precision mass measurements of ${}^{119}\mathrm{Cd}$ and ${}^{119}\mathrm{Ag}$ and their respective isomeric states have been performed with the phase-imaging ion cyclotron resonance (PI-ICR) method with a precision of $\delta m/m\approx {10}^{-8}$ using the Canadian Penning trap. The ground-state mass excess, as well as the excitation energy, agrees with recent Penning trap measurements from JYFLTRAP. Network calculations using these new measurements have revealed that, contrary to previous expectations, ${}^{119m}\mathrm{Ag}$ behaves as an astromer, which significantly affects the population of ${}^{119}\mathrm{Ag}$.

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• Isomer decays
• r process
• 90 ≤ A ≤ 149
• Penning traps
• Radioactive beams