Probing the Shell Effects on Fission: The New Superheavy Nucleus 257Sg

par Pavol Mošať (GSI)

vendredi 14 nov. 2025, 14:30 → 17:00 Europe/Paris

The fission of heavy atomic nuclei is the main constraint on the existence of chemical elements with large atomic numbers. Nuclei with Z > 103 are stabilized against fission due to effects resulting from the nuclear shell structure and can thus exist for a time longer than 10⁻¹⁴ s. This is the time needed for an atomic shell to be established [1]. The so-called isotopic borders for particular superheavy elements can be studied in the neutron-deficient nuclei [2,3]. However, the present experimental technique (i.e., in-flight separation) is limited to study nuclei with half-lives of about 10⁻⁶ s.

Another approach suitable for studying sub-µs nuclei is via long-lived K-isomeric states [4,5]. Recently, at TASCA, the 60-ns isotope ²⁵²Rf was discovered via its K-isomeric state, which has a half-life long enough to survive the flight through the separator [3]. This result shows that the isotopic border of Rf isotopes is yet to be reached.

The next step is to explore the isotopic border of Sg isotopes. Recently, at TASCA, we studied the neutron-deficient isotopes ^257-259Sg, aiming to investigate their fission properties and to probe the location of the isotopic border.

In the talk, results from the experiment will be discused in detail.

References

[1]	A. Wapstra, Pure Appl. Chem. 63, 879 (1991).
[2]	J. Khuyagbaatar, et al.,  Phys. Rev. C 104, L031303 (2021).
[3]	J. Khuyagbaatar, P. Mosat, et al., Phys. Rev. Let. 134, 022501 (2025).
[4]	D. Ackermann, S. Antalic and F. P. Heßberger, Eur. Phys. J. Spec. Top. 233, 1017 (2024).
[5]	J. Khuyagbaatar, Eur. J. Phys. A 58, 243 (2022).

 

PMosat_SemIPHC_Nov25.pdf