Neutron–proton pairing competition in N = Z nuclei: Metastable state decays in the proton dripline nuclei NB-82(41) and Tc-86(43)

The low-lying structures of the self-conjugate (N = Z) nuclei Nb-82(41)41 andTc-86(43)43 have been investigated using isomeric-decay spectroscopy following the projectile fragmentation of a Ag-107 beam. These represent the heaviest odd–odd N = Z nuclei in which internal decays have been identified to date. The resulting level schemes shed light on the shape evolution along the N = Z line between the doubly-magic systems Ni-56(28) and Sn-100(50) and support a preference for T = 1 states in Tz = 0 odd–odd nuclei at low excitation energies associated with a T = 1 neutron–proton pairing gap. Comparison with Projected Shell Model calculations suggests that the decay in Nb-82 may be interpreted as an isospin-changing K isomer.