Empirical rule for the pair break mechanism in three-quasiparticle rotational bands

An empirical rule on the basis of odd–even mass difference is suggested for the breaking of a proton pair or a neutron pair in odd-A nuclei to form a lower lying 3-quasiparticle state. If Δ_p is smaller than Δ_n , the proton pair breaks; on the other hand, if Δ_n is smaller than Δ_p , the neutron pair breaks down and forms a lower lying 3-quasiparticle state in an odd-A nuclide. This rule appears not only purely based on the proton paring/neutron pairing energy balancing condition but also on particular excitation energy, which is ≥1 MeV in the case of the rare-earth region. The extension of this rule to the configuration dependent pairing energies available in the literature is discussed as well as its applications for deciding on the breaking of proton/neutron pairs at higher excitation energies.