The quadrupole-quadrupole interaction and the inverted pairing

We present evidence that excitations induced by the quadrupole-quadrupole interaction are equivalent to an inverted surace-delta interaction whose largest multipole-pairing component is attractive and has maximum spin. This technical recognition led one to isolate the systemʹs intrinsic energies from the rest in the laboratory frame, trace the origin of the recently introduced optimum pair description of rotation and derive approximate but accurate analytical expressions of various band energies.