Superheavy Nuclei XVII: 1640 ≤ A < 1650 Systems

Superheavy nuclei and their associated stability continue to be active experimental and theoretical areas of research. Calculations in the superheavy mass region require the selection of an appropriate nuclear interaction. Although this interaction is usually based on the extrapolation of a known nuclear interaction, any approach becomes more uncertain as calculations proceed beyond mass regions that have been explored experimentally. In view of these uncertainties, calculations can only provide qualitative results. These extrapolations and the associated model results become more uncertain as the system mass increases.

Previous calculations explored the 570 ≤ A < 1640 mass region. This paper extends these calculations into the 1640 ≤ A < 1650 region. The single-particle level spectrum is generated using a Woods-Saxon potential with parameters optimized to permit extrapolation into the A ≥ 1600 superheavy region utilizing the Rost-1600 interaction that was based on existing nuclear systems as well as nuclear matter calculations. This interaction is essentially the Rost interaction that includes a 15% uncertainty in the potential strength. Calculated single-particle energies are also derived by incorporating the unmodified pairing interaction of Blomqvist and Wahlborn to investigate the bounding characteristics of A ≥ 1600 superheavy nuclear systems.

The stability of 1640 ≤ A < 1650 systems are determined by evaluating the various decay modes (i.e., alpha decay, beta decay, positron decay, electron capture, and spontaneous fission). Based on previous calculations, stability in the 1640 ≤ A < 1650 mass region is expected to be dominated by alpha decay and beta decay.

Given uncertainties in the model interaction, it is not practical to determine absolute values for the half-lives and Q-values. However, the model does permit establishing the relative stability of nuclear systems and to highlight possible islands of stability. Using the Rost-1600 interaction, 49 even-even nuclear systems are predicted in the 1640 ≤ A < 1650 mass region. For this mass region, the model predicts a new island of stability in the vicinity of the Z = 444 – 450. Model calculations suggest that the most stable 1640 ≤ A < 1650 system occurs at (Z, A) = (444, 1642).