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.

The soarch for the πi13/2⊗νi13/2 band in 178Ir has been conducted through the 152Sm (31P, 5nγ)178Ir reaction and thc excitation functions，x-γ and γ-γ-t coincidence mcasurements. Five rotational bands have been nowly identified The low-spin signaturc inversion in the πi13/2⊗νi13/2 band has been confirmed by the observations of linking transitions and signaturc crossing at I=25.5h. The inversion phenonJenon in πh11/2⊗νi13/2, rcho/2⊗νi13/2 and πi13/2⊗νi13/2 structulcs in 178Ir provides a unique testing ground for diffbrent theorctical interpretations.

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 180Ir have been investigated by means of in-beam g-ray spectroscopy techniques with the 154Sm (31P,5nγ)180Ir reaction. Excitation functions, x-γ and γ-γ-t coincidences, DCO (directional correlation of grays deexciting oriented states) ratios, and intraband B(M1)/B(E2) ratios were measured. Five rotational bands have been identified and their configurations are proposed on the basis of B(M1)/B(E2) ratios and by comparing the band properties with known bands in neighboring odd-mass and even-mass nuclei. The neutron AB crossing is observed at hωc=0.26(1) MeV for the π1/2-[541]⊗v1/2-[521] and π1/2-[541]⊗v5/2-[512] bands, respectively. Staggering of levels as a function of the number of neutron pairs is revealed in the π1/2-[541]⊗v1/2-[521] doubly decoupled bands of 178-186Ir. The gradual alignment gains at low rotational frequencies are observed in the two strongly coupled bands. Band crossings and alignments in 180Ir are discussed with reference to the total Routhian surface and cranked shell model calculations performed for the neighboring odd-mass nuclei.

An in-beam γ-ray spectroscopy experiment for 142Pm has been performed via the 128Te (19F, 5n) reaction at beam energies of 75 MeV through 95 MeV. Excitation functions and γ-γ coincidences have been measured. Detailed analysis of γ-γ coincidence relationships leads to a revised high-spin level scheme for 142Pm. The πh11/2 vh11/2−1 multiplet in this nucleus has been identified and the discussion is based on a systematic of corresponding states in neighboring odd-odd nuclei. The previously known 67-μs isomer and associated decay grays have been placed into the new level scheme. This long-lived isomer is proposed to be a four-hole state with predominantly the （πg7/2−2-1d5/2-2vh11/2-1) 13-configuration.