Systematics of even-even Tz= 1 nuclei in the A= 80 region: High-spin rotational bands in 74Kr, 78Sr, and 82Zr

High-spin states of Tz=1 nuclei were studied with the reactions 58Ni(28Si,3α)74Kr, 58Ni(28Si,2α)78Sr, and 58Ni(28Si,2p2n)82Zr at 130 MeV beam energy. The Gammasphere array in conjunction with the 4π charged-particle detector array Microball was used to detect γ rays in coincidence with evaporated light charged particles. The known π=+, α=0 yrast bands were extended to I=28ℎ at 20 MeV excitation energy. For all three nuclei, a number of positive- and negative-parity sidebands were established; altogether 15 new rotational bands were found. The data are discussed using the pairing-and-deformation self-consistent total Routhian surface (TRS) model: High-spin structures of 74Kr and 78Sr are governed by the shell gaps at large prolate deformation while 82Zr seems to exhibit shape coexistence. Nearly identical bands were established which may be explained as arising from the fp orbits acting as spectators at very elongated shapes. The experimental data in these Tz=1 nuclei are in good agreement with predictions of the TRS model using conventional T=1 like-nucleon pairing correlations. copyright 1997 The American Physical Society