Alignment delays in the N = Z nuclei Kr-72, Sr-76, and Zr-80 - art. no. 132501

The ground state rotational bands of the N = Z nuclei Kr-72, Sr-76, and Zr- 80 have been extended into the angular momentum region where rotation align ment of particles is normally expected. By measuring the moments of inertia of these bands we have observed a consistent increase in the rotational fr equency required to start pair breaking, when compared to neighboring nucle i. Kr-72 shows the most marked effect. It has been widely suggested that th ese "delayed alignments" arise from np-pairing correlations. However, align ment frequencies are very sensitive to shape degrees of freedom and normal pairing, so the new experimental observations are still open to interpretat ion.