ON THE SUPERCONDUCTIVITY APPROXIMATION FOR THE NUCLEAR PAIRING INTERACTION

An alternative formulation of the method developed by Nogami to eliminate the effect of the number fluctuation in the superconductivity approximation for the nuclear pairing interaction is given. The excited states of nonzero seniority are also discussed, where the effects of blocking and number fluctuation should be taken into account simultaneously. This can be done readily by our method. The excitation energies are obtained with good accuracy, as is shown by comparing our results with exact ones for the model of Ni isotopes obtained by Kerman, Lawson, and Macfarlane.