On the structure of 70, 72As

Abstract

The structure of the doubly odd nuclei 70, 72As has been investigated by the (p, nγ) reaction on 70, 72Ge. From the energies and intensities of observed γ-transitions and from their coincidence relations the level schemes were constructed. The half-lives of several excited states were measured. Spin and parity assignments are based upon the analysis of the excitation functions and upon angular distributions of the γ-rays. The level schemes obtained are compared with the predictions of a quasiproton-quasineutron model with exact number projection. This model describes the differences between the spectra of 70, 72, 74, 76As and gives a good description for the properties of the states in 70, 72As. Values for the proton and neutron occupation probabilities have been derived. We conclude that it is not necessary to assume deformation for the lowest states and that the Schiffer force is successful in most cases as an effective proton-neutron interaction. Some exceptions are discussed.