Speaker
Description
Decay properties of two new astatine isotopes, $^{188}$At and $^{190}$At, were studied in the Accelerator Laboratory of University of Jyv\"askyl\"a, Finland. The nuclei were produced in fusion-evaporation reactions, and those were subsequently separated from the primary beam using the gas-filled recoil separator RITU (Recoil Ion Transfer Unit). Decay spectroscopy studies resulted with a proton emission from $^{188}$At, presenting the observation of the heaviest known proton-emitting nucleus to date. The proton is suggested to be emitted from a prolate deformed (2$^-$) state, with a dominant $s_{1/2}$ proton component in the wavefunction. The interpretation was based on the non-adiabatic quasiparticle model which was expanded to treat nuclei in the beyond-lead region. The one-proton separation energy deviates from the systematics, and a possible source for this effect will be discussed in this presentation. The $\alpha$-decay properties for the second lightest known astatine isotope, $^{190}$At, were measured and compared to the systematics. In addition, the possible presence of proton emission from this nucleus is discussed. In this presentation, the experimental details and the results of already published $^{188}$At [1] and $^{190}$At [2] isotopes will be presented.
[1] H. Kokkonen, K. Auranen et al., Nat Commun 16, 4985 (2025)
[2] H. Kokkonen, K. Auranen et al., Phys. Rev. C 107 064312 (2023)