Effects of intruder states in ¹⁷⁹Ir

High-spin states of the odd-A ¹⁷⁹Ir have been studied via heavy-ion fusion reaction. Bands built on five different Nilsson states (πh_9/2, πi_13/2, πd_5/2, πh_11/2, and πf_7/2) have been established, among which the πf_7/2 (1/2^-[530]) band is identified for the first time in Ir isotopes. Experimental aligned angular momenta, band-crossing frequencies, and relative transition rates are analyzed and compared with the cranked shell model and the particle-rotor model calculations. Effects of intruder states, particularly πh_9/2 and πi_13/2, have been discussed on three aspects: deformation driving, shape evolution, and quasiparticle alignment. It is found that the πi_13/2 orbital has a strong, positive-β₂ driving effect on the shape of Ir nuclei, while the driving force of the πh_9/2 orbital is minimized when the Fermi level reaches the shell. The total Routhian surface calculations suggest that the πh_11/2 and πd_5/2 configurations in ¹⁷⁹Ir possess relatively large β₂ deformation (∼0.26), which is consistent with the particle-rotor calculations. The possible contribution of the πh_9/2 crossing to the gradual alignment gains observed in the πh_11/2 and πd_5/2 bands is discussed from the influence of deformation and interaction strength.