Interacting-boson-fermion-fermion model description of ${}_{}{}^{140}{}_{}{}^{}\mathrm{La}_{83}^{}{}_{}{}^{}$ and comparison with levels populated by beta decay and neutron capture

We have studied the levels of ${}_{}{}^{140}{}_{}{}^{}\mathrm{La}$ populated in the beta decay of ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ba}$ by gamma-ray spectroscopy, which included Compton-suppression gamma-ray spectra of ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ba}$ sources that were continuously eluted of the ${}_{}{}^{140}{}_{}{}^{}\mathrm{La}$ daughter activity using ion-exchange chromatographic techniques. The study of the gamma-ray deexcitation of the low-energy levels was completed by a measurement of the low-energy gamma-ray spectrum following thermal neutron capture on ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$. Also, we have performed calculations using the interacting-boson-fermion-fermion model. When we compare the model predictions with the levels and their properties, which we have determined, we find better agreement than has been obtained using quasiparticle-vibrational models.