Valence nucleon populations in the Ni isotopes

Measurements of neutron-adding, neutron-removing, and proton-adding reactions were carried out for the four stable even Ni isotopes. Particular attention was paid to obtaining precise values of the cross sections at the peaks of the angular distributions. Tests with sum rules for the neutron data indicate that the results are self-consistent at the level of a few tenths of a nucleon. Data on proton-adding reactions were also obtained and analyzed with a slightly different method—while these data are also consistent, the ambiguities are larger. The occupancies of the neutron orbits derived from the data, the proton vacancies, and the energy centroids of the neutron, neutron-hole, and proton single-particle excitations are obtained. The data also provide some estimate about the closure of the 0f7/2 shell. The results are compared to shell-model calculations and may serve as a reference point for future exploration. The understanding of nuclear structure in terms of the shell model has been remarkably successful in describing many of the observed features of nuclei. Nucleon transfer reactions have been essential in relating these models to experimentally measurable quantities, and specifically single-particle overlaps. The energies of single-particle states based on most stable nuclei have been mapped out by measurements of nucleonadding and nucleon-removing transfer reactions. The present paper gives a test case of the consistency of the procedures used in extracting such information from transfer reactions, using measurements based on the stable Ni isotopes, and elaborates