Structural changes at large angular momentum in neutron-rich $^{121,123}$Cd
Résumé
Prompt γ rays of isotopically identified neutron-rich isotopes of Cd, produced in transfer- and fusion-fission
induced by the 238U beam at 6.2 MeV/u on a 9Be target, were measured using the EXOGAM γ -ray detector
array and the magnetic spectrometer VAMOS++. New results for the level scheme of 121,123Cd, extending to
relatively large angular momentum are reported. The energy levels above 2-MeV excitation energy, are found to
differ from those observed in lighter isotopes of Cd indicating a change in structure in these more neutron-rich
nuclei. These states are not explained by large-scale shell model calculations, that explain well the structure of
the underlying Sn isotopes and the neighboring even-A Cd isotopes. The present data, especially for the odd-A
nuclei, point to a deficiency in the matrix elements related to the p-n residual interaction and provide a new
domain for testing widely used shell model interactions employed for understanding the evolution of structure in
neutron-rich nuclei.