We present mass excesses (ME) of neutron-rich isotopes of Ar through Fe, obtained via time of flight $B\rho$ mass spectrometry at the National Superconducting Cyclotron Laboratory. Our new results have significantly reduced systematic uncertainties relative to a prior analysis, enabling the first determination of ME for ${}^{58,59}\mathrm{Ti},{}^{62}\mathrm{V},{}^{65}\mathrm{Cr},{}^{67,68}\mathrm{Mn}$, and ${}^{69,70}\mathrm{Fe}$. Our results show the $N=34$ subshell weaken at Sc and vanish at Ti, along with the absence of an $N=40$ subshell at Mn. This leads to a cooler accreted neutron star crust, highlighting the connection between the structure of nuclei and neutron stars.

• Received 3 February 2020
• Accepted 21 April 2020

DOI:https://doi.org/10.1103/PhysRevC.101.052801