Nuclear magnetic moment of the neutron-rich nucleus O21

Abstract

The ground-state magnetic dipole moment of the neutron-rich $^{21}\mathrm{O}$ isotope has been measured via $\ensuremath{\beta}$-ray-detected nuclear magnetic resonance ($\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{NMR}$) spectroscopy by using a spin-polarized secondary beam of $^{21}\mathrm{O}$ produced from the $^{22}\mathrm{Ne}$ primary beam. From the present measurement, the $g$ factor $|{g}_{\mathrm{exp}}(^{21}\mathrm{O}_{\mathrm{g}.\mathrm{s}.})|=0.6036(14)$ has been determined. Based on the comparison of this value with Schmidt values, we unambiguously confirm the $\ensuremath{\nu}{d}_{5/2}$ configuration with spin and parity assignments ${I}^{\ensuremath{\pi}}=5/{2}^{+}$ for the $^{21}\mathrm{O}$ ground state, suggested by previously reported studies. Consequently, the magnetic moment has been determined as ${\ensuremath{\mu}}_{\mathrm{exp}}(^{21}\mathrm{O}_{\mathrm{g}.\mathrm{s}.})=(\ensuremath{-})1.5090(35){\ensuremath{\mu}}_{N}$. The obtained experimental magnetic moment is in good agreement with the predictions of the shell-model calculations using the USD, YSOX, and SDPF-M interactions as well as random phase approximation (RPA) calculations. This observation indicates that the $^{21}\mathrm{O}$ nucleus in its ground state does not manifest any anomalous structure and is not influenced by the proximity of the drip line.