Ground-state two-proton ($2p$) radioactivity is a rare decay mode found in a few very proton-rich isotopes. The $2p$ decay lifetime and properties of emitted protons carry invaluable information on nuclear structure in the presence of a low-lying proton continuum. The recently measured $2p$ decay of ${}^{67}\mathrm{Kr}$ turned out to be unexpectedly fast. Since ${}^{67}\mathrm{Kr}$ is expected to be a deformed system, we investigate the impact of deformation effects on the $2p$ radioactivity. We apply the recently developed Gamow coupled-channel framework, which allows for a precise description of three-body systems in the presence of rotational and vibrational couplings. This is the first application of a three-body approach to a two-nucleon decay from a deformed nucleus. We show that deformation couplings significantly increase the $2p$ decay width of ${}^{67}\mathrm{Kr}$; this finding explains the puzzling experimental data. The calculated angular proton-proton correlations reflect a competition between $1p$ and $2p$ decay modes in this nucleus.

• Received 20 March 2018
• Revised 20 April 2018

DOI:https://doi.org/10.1103/PhysRevLett.120.212502