High-spin level structure in 184Au has been reinvestigated using the multidetector array of GASP via the 159Tbs29Si,4n gd184Au reaction at a beam energy of 140 MeV. The ground-state band and the excited πi13/2⊗vi13/2 2-qp band have been extended up to lower and higher spin states. An upbend has been observed in the excited band at hω～0.25 MeV and is interpreted as resulting from a pair of πh9/2 alignment. This lowfrequency (πh9/2)2 alignment is supported by the measured B(M1)/B(E2) ratios and alignment properties in neighboring odd-A nuclei. The linking transitions between the two bands and to the ground state have been established leading to a firm spin-and-parity assignment for the πi13/2⊗vi13/2 band in 184Au. This result provides strong evidence for the low-spin signature inversion in the πi13/2⊗vi13/2 bands of odd-odd nuclei in the A,180 mass region.

High-spin states in 183Au have been studied experimentally using the 159Tb(29Si, 5n)183Au reaction at a beam energy of 140 MeV. Three- or higherfold γ-ray coincidences have been measured using the detector array of GASP. The level scheme of 183Auwas revised and extended.Arotational band proposed as the unfavored signature branch of the πi13/2 band has been observed for 183Au. Interaction properties between the two negative-signature bands of the πh9/2-π7/2 system have been discussed for the light odd-A Au nuclei.

Abstract. High-spin states in 176Ir have been investigated via the 149Sm (31P, 4nγ) 176Ir reaction through excitation functions, X-γ and γ-γ coincidence measurements. Four rotational bands have been identified for the first time and their configurations are suggested on the basis of the existing knowledge of band structures in odd-odd nuclei as well as the measured in-band B(M1)/B(E2) ratios. Among the four bands observed, the πh9/2⊗νi13/2 and πi13/2⊗νi13/2 bands exhibit an anomalous signature splitting. The signature inversion point is observed in the former at Ic=18 which is consistent with expectations; this signature inversion spin in the πi13/2⊗νi13/2 band may be larger than 25. The combined effects of Coriolis and p-n residual interactions involved in such an inversion phenomenon have been discussed qualitatively.

High spin states in 178Ir have been studied via the 152Sm (31P,5nγ) 178Ir reaction through excitation functions, X-γ and γ-γ-t coincidence measurements. According to the band structure characteristics and the measured intraband B(M1)/B(E2) ratios, two rotational bands are identified and assigned to be associated with the πh9/2⊗νi13/2 and πh11/2⊗νi13/2 configurations, respectively. Both bands show the signature inversion feature.

High-spin states in the odd-odd 172Re have been investigated via the 149Sm(27Al, 4nγ)172Re reaction through excitation functions, x-γ and γ-γ coincidence measurements. A level scheme consisting of three rotational bands has been identified for the first time extending the high-spin studies of A～160 odd-odd nuclei to the currently lightest rhenium isotope. The three bands have been assigned to be built on the πh11/2⊗νi13/2, πh9/2⊗νi13/2, and p1/2−[541]⊗ν1/2−[521] configurations according to their rotational properties in quasiparticle alignments, signature splitting, in-band B(M1)/B(E2) ratios, level spacing systematics, band crossing frequencies, as well as the existing knowledge in neighboring nuclei. Low-spin signature inversion has been confirmed in the first two bands due to the observation of signature crossing at high-spin states. The general features of inversion phenomenon in the semidecoupled bands are presented and discussed with reference to theoretical calculations of two quasiparticle plus rotor model including p-n interactions.