Population of a low-spin positive-parity band from high-spin intruder states in Au: The two-state mixing effect

The extremely neutron-deficient isotopes $^{177,179}$Au were studied by means of in-beam γ-ray spectroscopy. Specific tagging techniques, α-decay tagging in $^{177}$Au and isomer tagging in $^{179}$Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2${d}_{3/2}$ and 3${s}_{1/2}$ proton-hole configurations, from the 1${i}_{13/2}$ proton-intruder configuration was observed in $^{177}$Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state.