Anomalous p-shell isoscalar magnetic moments: Remeasurement of 9C and the influence of isospin nonconservation

Abstract

We have remeasured the ground state $g$ factor of ${}^{9}\mathrm{C}$ using the technique of nuclear magnetic resonance on beta-emitting nuclei (\ensuremath{\beta}-NMR) on spin-polarized ${}^{9}\mathrm{C}$ nuclei produced by the fragmentation of a ${}^{20}\mathrm{Ne}$ beam at 80 MeV/nucleon in a Nb target. Our new value of 1.396(3)${\ensuremath{\mu}}_{N}$ is consistent with the previously measured value of the ground state magnetic moment of this nuclide. The results of shell model calculations employing isospin-nonconserving (INC) terms in the nuclear Hamiltonian are shown to better reproduce the quenched magnetic dipole moment of ${}^{9}\mathrm{C}$ and the previously described anomalous isoscalar spin expectation value 〈\ensuremath{\sigma}〉 for the ${}^{9}{\mathrm{L}\mathrm{i}\ensuremath{-}}^{9}\mathrm{C}$ mirror system.