0+ states in Ni-isotopes described by the broken-pair approximation and the generator coordinate method

Two distinct methods, the Broken-Pair Approximation (BPA) and the Generator Coordinate Method (GCM), have been compared for the 0⁺ states of Ni-isotopes. The states are obtained in terms of valence neutrons occupying 2p 3 2, 1f 5 2, 2p 1 2 and 1g 9 2 single particle (sp) levels outside the assumed N = Z = 28 inert core using (a) the pairing force and (b) the renormalized non-local separable Tabakin interaction. The ground state properties are discussed. The resulting wavefunctions havebeen used to calculate the angular distribution, total cross-section and the related quantities for the two-nucleon transfer reactions. The analysis of the results points toward the requirements for the applicability of these methods.