A particle rotor model with a quasi-neutron coupled with a triaxially deformed rotor is applied to study signature splitting for bands with intruder orbital ν7/2^+ [633] and non-intruder orbital ν5/2^-[512] in ^173W. Excellent agreement with the observed energy spectra has been achieved for both bands. Signature splitting for band ν7/2^+ [633], and band ν5/2^-[512] before the onset of signature inversion, is satisfactorily reproduced by introducing the γ degree of freedom. The phase and

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... e of signature splitting in band ν5/2^-[512] is attributed to strong competition between 2f_7/2 and 1h_9/2 components. However, the explanation of signature inversion in band ν5/2^-[512] self-consistently is beyond the present one quasi-neutron coupled with a triaxially deformed rotor.