Ground State Electromagnetic Moments of ${}^{37}$Ca

Abstract

The hyperfine coupling constants of neutron deficient ${}^{37}$Ca were deduced from the atomic hyperfine spectrum of the $4s{}^2{S}_{1/2}$ $\leftrightarrow$ $4p{}^2{P}_{3/2}$ transition in Ca II, measured using the collinear laser spectroscopy technique. The ground-state magnetic-dipole and spectroscopic electric-quadrupole moments were determined for the first time as $\mu =+0.7453(72){\mu }_N$ and $Q=-15(11)$ $e^2$fm${}^2$, respectively. The experimental values agree well with nuclear shell model calculations using the universal sd model-space Hamiltonians versions A and B (USDA/B) in the $sd$-model space with a 95\% probability of the canonical nucleon configuration. It is shown that the magnetic moment of ${}^{39}$Ca requires a larger non-$sd$-shell component than that of ${}^{37}$Ca for good agreement with the shell-model calculation, indicating a more robust closed sub-shell structure of ${}^{36}$Ca at the neutron number $N$ = 16 than ${}^{40}$Ca. The results are also compared to valence-space in-medium similarity renormalization group calculations based on chiral two- and three-nucleon interactions.