High-spin band crossings in $N=Z$ nuclei have been suggested to contain information on $T=0\mathrm{}$ neutron-proton pairing correlations. Several experiments that produced high angular momentum states in the $N=Z$ nuclei ${}_{34}^{68}\mathrm{Se}$ and ${}_{36}^{72}\mathrm{Kr}$ have been carried out. Levels in these neutron deficient nuclei were populated through heavy-ion fusion reactions and their subsequent $\gamma$ decay was measured with Gammasphere. The combination of these data allowed the level sequence in yrast and near yrast bands to be firmly established, extended to higher spin, and has resolved some previously published discrepancies. The yrast sequence in ${}^{68}\mathrm{Se}$ was extended to spin $J=26\mathrm{}$ and a new band crossing observed. In ${}^{72}\mathrm{Kr},$ the ground state band was found to fork into three bands, each of which has irregularities in its moment of inertia. Differential Doppler shift measurements indicate that the two high-spin bands have very different shapes. Similar, sharp band crossings were established in both nuclei. A comparison of these data with recent measurements of $N=Z+2\mathrm{}$ nuclei ${}^{70}\mathrm{Se}$ and ${}^{74}\mathrm{Kr}$ allowed the issue of “delayed alignments” to be addressed in detail. No clear-cut evidence for any delay was found.

• Received 13 March 2003

DOI:https://doi.org/10.1103/PhysRevC.67.064318