Isospin Structure of Pairing Collective Motion

The isospin degree of freedom of the pairing force is studied in the framework of the rotational ($\Delta \ne 0$) and vibrational ($\Delta =0\mathrm{}$) models. The magnitude $\Delta$ is the BCS gap parameter. The predictions of the two models concerning two-nucleon transfer reactions and energy levels are compared and contrasted. Some of the available experimental material around ${\mathrm{Ni}}^{56}$ is discussed in this framework. Further experiments are suggested which would help decide between the coupling schemes.