Study on the systematics of two-neutron high spin states in fp shell nuclei by means of the (α,2He) reaction

The (α,2He)-reaction was studied at 56-57 MeV incident energy at the target nuclei sup(58,60,62,64)Ni. In a laboratory angular range from 150-37.50 the angular distributions of the absolute differential cross section were taken up. The measurements were performed with the position resolving 2He detector developed in Bonn. By means of DWBA calculations for the first time in all final nuclei states with the configurations (fsub(5/2), gsub(9/2))7-(gsub(9/2))82+, and (gsub(9/2), dsub(5/2))6+ could be identified; these were except the Jsup(π)=7- states in 60Ni hitherto not known. The two-neutron binding energies of these states were under inclusion of further states known from literature compared with shell model calculations according to the weak coupling method of Bansal and French. By a set of 4 parameters both the two-neutron binding energies of the (fsub(5/2), gsub(9/2))7- and (gsub(9/2))2sub(8+) states and the one-particle binding energies of the f-sub(5/2) and g+sub(5/2) one-neutron states over a large number of nuclei could very well be reproduced. For calculations on the states with the configuration (gsub(9/2), dsub(5/2))6+ the present data set is not yet sufficient. The found agreement of the calculations with the experimental data shows that two-neutron high spin states in the fp shell nuclei can be correctly described by this simple picture. (orig.)