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

High-spin states of T-z = 1 nuclei were studied with the reactions Ni-58(Si-28,3 alpha)Kr-74,Ni-58(Si-28,2 alpha)Sr-78, and Ni-58(Si-28,2p2n)Zr-82 at 130 MeV beam energy. The Gammasphere array in conjunction with the 4 pi charged-particle detector array Microball was used to detect gamma rays in coincidence with evaporated light charged particles. The known pi = +, alpha = 0 yrast bands were extended to I = 28 (h) over bar 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 Kr-74 and Sr-78 are governed by the shell gaps at large prolate deformation while Zr-82 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 T-z = 1 nuclei are in good agreement with predictions of the TRS model using conventional T = 1 like-nucleon pairing correlations.