Nuclear mass measurements map the structure of atomic nuclei and accreting neutron stars

Abstract

We present mass excesses (ME) of neutron-rich isotopes of Ar through Fe, obtained via time of flight $B\ensuremath{\rho}$ 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.