From the prediction of atomic and molecular properties to the understanding of the development of our universe, exotic radionuclides are nowadays of great interest in several research domains. Whereas these exotic elements are recently discovered transactinides, or long-lived lanthanides, the study of their chemical and nuclear properties represents a unique challenge. Transactinide elements can only be produced artificially in heavy-ion induced nuclear fusion reactions. The typically low production rates and short half-lives of these elements require rapid and selective chemical setups. This entails that a complete and unambiguous chemical characterization of a transactinide can only be achieved by studying – literally – one atom at a time [1, 2].

Different but no less challenging is the determination of nuclear properties, such as half-lives, of exotic lanthanides. Certain long-lived lanthanides (e.g., ¹⁴⁶Sm, ¹⁵⁴Dy, ¹⁴⁸Gd, ¹⁵⁷Tb) play a fundamental role in astrophysics and nuclear physics. For many of these studies, an accurate knowledge on the nuclear properties of the above-mentioned radionuclides is required. However, the currently available data for the half-life of ¹⁴⁶Sm, ^148,150Gd, ¹⁵⁴Dy, and ^157,158Tb are inconsistent, or affected by high uncertainty [3-5]. Reasons for these shortcomings in the nuclear databases are in many cases the limited availability of the isotopes of interest, often accompanied by difficulties in the preparation of samples with a high chemical purity. To overcome these limitations, the initiative “Exotic Radionuclides from Accelerator Waste for Science and Technology – ERAWAST”, was launched in 2006 at Paul Scherrer Institute (PSI) [6, 7]. This long-term project aims to reprocess irradiated materials from the PSI accelerator-facilities, in order to obtain exotic radionuclides for scientific purposes. Detailed information can be found at the website: psi.ch/en/lrc/erawast. Among the several applications of ERAWAST, special focus is given to the improvement of the existent nuclear databases by re-determining the half-life of exotic radionuclides.

Here, the latest results on the chemical experiments with the transactinide dubnium (Z = 105) [8] in collaboration with the Japan Atomic Energy Agency (JAEA), together with the current developments related to the ERAWAST project, will be presented.

[1] Matthias Schädel, Dawn Shaughnessy, Eds. The chemistry of superheavy elements. Springer Science & Business Media, 2013.

[2] Andreas Türler, Valeria Pershina, Chemical Reviews, 2013, 113, 1237-1312.

[3] Georges Audi et al., Chinese Physics C, 2017, 41, 030001-030138.

[4] David Brown et al., Nuclear Data Sheets, 2018, 148, 1-142.

[5] Zsolt Sóti, Joseph Magill, Raymond Dreher, EPJ Nuclear Sciences & Technologies, 2019, 5, 6-17.

[6] Dorothea Schumann, Jörg Neuhausen. Journal of Physics G: Nuclear and Particle Physics, 2007, 35, 014046-014052.

[7] Dorothea Schumann et al., Radiochimca Acta, 2013, 101, 501-508.

[8] Nadine M. Chiera et al., Angewandte Chemie, 2021, DOI: 10.1002/ange.202102808