Results of decay studies of nuclei in the vicinity of ${}^{54}\mathrm{Zn}$, which is the most neutron-deficient isotope of zinc and undergoes ground-state two-proton radioactivity (2p), are presented. The measurements were performed with a gaseous time-projection chamber with optical readout, which allowed us to record tracks of protons emitted in the decays. A new method of data analysis was used to reconstruct energies and emission angles of low-energy protons that were stopped within the active volume of the chamber. Half-lives and branching ratios for $\beta$-delayed proton emission channels were determined for ${}^{56}\mathrm{Zn}, {}^{55}\mathrm{Zn}$, and ${}^{55}\mathrm{Cu}$. The $\beta$-delayed emission of two protons for ${}^{55}\mathrm{Zn}$ was observed for the first time. Five events of 2p radioactivity of ${}^{54}\mathrm{Zn}$ were detected and reconstructed. The distribution of the opening angle between momenta of the two protons is consistent with the findings published by Ascher et al. [Phys. Rev. Lett. 107, 102502 (2011)].

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• Beta decay
• Nuclear structure & decays
• Proton emission
• 39 ≤ A ≤ 58