Benchmarking electromagnetic observables in angular-momentum projected Hartree-Fock

We benchmark electromagnetic transitions and moments (electric quadrupole and magnetic dipole) in angular-momentum projected-after-variation Hartree-Fock calculations against full configuration-interaction diagonalization results in a shell model basis. For such a simple approximation we find reasonably good agreement, including for many odd-$A$ and odd-odd nuclides. As previous work on excitation spectra found, results are frequently improved in cases with shape coexistence. Here we considered select cases from the $sd$- and $pf$-valences spaces. While electric quadrupole moments and transitions are, as one might expect, frequently (though not always) well reproduced, especially in even-even nuclides, magnetic dipole moments and transitions are overall better than expected. This continues the benchmarking of projected Hartree-Fock as a simple yet effective alternative to full configuration-interaction as well as an underlying foundation for many other many-body methods.