Neutron–proton pairing competition in N=ZN=Z nuclei: Metastable state decays in the proton dripline nuclei 8241Nb and 8643Tc

The low-lying structures of the self-conjugate (N=ZN=Z) nuclei 8241Nb41 and 8643Tc43 have been investigated using isomeric-decay spectroscopy following the projectile fragmentation of a 107Ag beam. These represent the heaviest odd–odd N=ZN=Z nuclei in which internal decays have been identified to date. The resulting level schemes shed light on the shape evolution along the N=ZN=Z line between the doubly-magic systems 5628Ni and 10050Sn and support a preference for T=1T=1 states in Tz=0Tz=0 odd–odd nuclei at low excitation energies associated with a T=1T=1 neutron–proton pairing gap. Comparison with Projected Shell Model calculations suggests that the decay in 82Nb may be interpreted as an isospin-changing K isomer.