Nuclear properties across the chart of nuclides are key to improving and validating our understanding of the strong interaction in nuclear physics. We present high-precision mass measurements of neutron-rich Fe isotopes performed at the TITAN facility. The multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS), achieving a resolving power greater than $600000$ for the first time, enabled the measurement of ${}^{63–70}\mathrm{Fe}$, including first-time high-precision direct measurements ($\delta m/m\approx {10}^{-7}$) of ${}^{68–70}\mathrm{Fe}$, as well as the discovery of a long-lived isomeric state in ${}^{69}\mathrm{Fe}$. These measurements are accompanied by both mean-field and ab initio calculations using the most recent realizations which enable theoretical assignment of the spin-parities of the ${}^{69}\mathrm{Fe}$ ground and isomeric states. Together with mean-field calculations of quadrupole deformation parameters for the Fe isotope chain, these results benchmark a maximum of deformation in the $N=40$ island of inversion in Fe and shed light on trends in level densities indicated in the newly refined mass surface.

• Received 19 July 2021
• Revised 24 December 2021
• Accepted 16 March 2022

DOI:https://doi.org/10.1103/PhysRevC.105.L041301