Ground-state electromagnetic moments of ${}^{37}\mathrm{Ca}$

The hyperfine coupling constants of neutron deficient ${}^{37}\mathrm{Ca}$ 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 $\mu =+0.7453\left(72\right){\mu }_N$ and $Q=-15\left(11\right)e^2{\mathrm{fm}}^2$, 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 ${}^{39}\mathrm{Ca}$ requires a larger non-$sd$-shell component than that of ${}^{37}\mathrm{Ca}$ for good agreement with the shell-model calculation, indicating a more robust closed subshell structure of ${}^{36}\mathrm{Ca}$ at the neutron number $N=16$ than ${}^{40}\mathrm{Ca}$. The results are also compared to valence-space in-medium similarity renormalization group calculations based on chiral two- and three-nucleon interactions.

Figure 1

Hyperfine spectra and residuals of (a) ${}^{37}\mathrm{Ca}$ and (b) ${}^{39}\mathrm{Ca}$. The solid circles are the data and the solid line is the best fit of a Voigt profile.

Figure 2

Comparison between experimental values (solid circles) and shell-model calculations with USDB-EM1 (bars) for (a) magnetic moments and (b) isoscalar and isovector magnetic moment.