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Excited states of the proton-unbound nucleus $^{177}$Au have been populated following the $^{92}$Mo($^{88}$Sr,$ 2pn$) reaction in an experiment performed at the University of Jyv\"askyl\"a Accelerator Laboratory. Gamma rays detected in the JUROGAM spectrometer were correlated with the characteristic $\alpha$ decays of $^{177}$Au detected following a recoil implantation in the GREAT spectrometer. A large number of transitions ($\sim 60$ $\gamma$ rays) have been assigned unambiguously to $^{177}$Au and ordered into four collective band structures and other single-particle excitations.
Several intruder configurations formed by single-proton excitations across the $Z = 82$ shell gap have been established. These have been interpreted as $\pi i_{13/2}$, $\pi f_{7/2} \oplus h_{9/2}$ and $\pi h_{9/2}$ prolate configurations. It has been established that the $\pi i_{13/2}$ and $\pi f_{7/2} \oplus h_{9/2}$ bands have decay paths to both the positive-parity mixed (1/2$^{+} \oplus$ 3/2$^{+}$) ground state and the negative-parity 11/2$^-$ isomer, which is unusual in this mass region. Structures based on the coupling of the odd $\pi$ $h_{11/2}^{-1}$ proton hole to excitations of the $^{178}$Hg core have been established in the excitation level scheme. An oblate $\pi h_{11/2}^{-1}$ $\otimes$ $^{178}$Hg($2_{1}^{+}$) state and a prolate strongly coupled band based on the $\pi h_{11/2}^{-1}$ $\otimes$ $^{178}$Hg($0_{2}^{+}$) configuration have been identified. The decay paths from the strongly coupled band and the search for evidence of electric monopole decays are discussed.
