Rotational bands and signature inversion phenomena in πh _9/2⊗νi_13/2 and πi_13/2⊗ν i_13/2 structures in odd-odd ¹⁷⁶Ir

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 πh _9/2⊗νi _13/2 and πi _13/2⊗νi _13/2 bands exhibit an anomalous signature splitting. The signature inversion point is observed in the former at I _c = 18? which is consistent with expectations; this signature inversion spin in the πi _13/2⊗ νi _13/2 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.