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 wi th the 4 pi charged-particle detector array Microball was used to dete ct gamma rays in coincidence with evaporated light charged particles. The known pi = +, alpha = 0 yrast bands were extended to I = 28 (h) ov er bar at 20 MeV excitation energy. For all three nuclei, a number of positive- and negative-parity sidebands were established; altogether 1 5 new rotational bands were found. The data are discussed using the pa iring-and-deformation self-consistent total Routhian surface (TRS) mod el: 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 c oexistence. Nearly identical bands were established which may be expla ined as arising from the fp orbits acting as spectators at very elonga ted shapes. The experimental data in these T-z = 1 nuclei are in good agreement with predictions of the TRS model using conventional T = 1 l ike-nucleon pairing correlations.