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

## TL;DR

This paper reports the first measurement of the ground-state electromagnetic moments of $^{37}$Ca using collinear laser spectroscopy, and compares the results with shell model and ab initio calculations to understand nuclear structure.

## Contribution

It provides the first experimental determination of the magnetic dipole and electric quadrupole moments of $^{37}$Ca and compares these with theoretical models.

## Key findings

- Experimental moments agree with shell model calculations.
- $^{36}$Ca shows a more robust closed-shell structure than $^{40}$Ca.
- Magnetic moment of $^{39}$Ca suggests larger non-$sd$-shell components.

## Abstract

The hyperfine coupling constants of neutron deficient $^{37}$Ca were deduced from the atomic hyperfine spectrum of the $4s~^2S_{1/2}$ $\leftrightarrow$ $4p~^2P_{3/2}$ 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.