First observation of very neutron-deficient 122Ce

Excited states have been identified in the very neutron-deficient 122Ce nucleus. This is the first observation of this nucleus and its excited states. The ground-state rotational band has been observed up to spin 14 ℏ. The band has been assigned to 122Ce by detecting gamma rays in coincidence with evaporated charged particles and neutrons. The E(21+) value suggests a rather large ground-state deformation of β2=0.35, in good agreement with Hartree-Fock-Bogoliubov (HFB) mean-field calculations. The aligned angular momentum of the band has been studied and is compared with those of the neighboring even-even cerium isotopes, and to Woods-Saxon cranking calculations. The non-observation of the π(h11/2)2 alignment until at least 0.4 MeV/ℏ is consistent with the extracted value of β2.