Speaker
Description
Long-lived isotopes of the superheavy elements (SHE) with atomic numbers Z ≥ 104, can be produced in fusion reactions between heavy actinide targets and neutron-rich projectiles at only very low rates: from single atoms per minute (Z = 104) to single atoms per week (Z = 114). Since the thermochromatography on gold has proved a unique method for chemical detection of heaviest elements, the description of SHE – gold interactions has
recently been of prime concern. It has been shown experimentally that the adsorption energies of Cn (Z = 112) and Fl (Z = 114) atoms on gold surface are close and lower than those for their closest homologues Hg and Pb, respectively. This confirms the theoretical predictions concerning the electronic structure of the Cn and Fl atoms: due to strong relativistic stabilization of s and p1/2 shells, both Cn and Fl ground states are of closed-shell character.
Strong relativistic effects suggest dramatic dissimilarities in the chemical behavior of SHEs and their formal lighter homologues. The calculated adsorption energy for single atoms of nihonium on a gold surface [1] differs substantially from the experimentally measured adsorption energy on gold of its nearest homolog, thallium. This casts doubt on the usefulness of the experiments with Nh formal homologues for understanding its chemistry. Despite manifest deviations of the chemical properties of the SHEs from the trends observed in their lighter formal homologues in the respective groups of the periodic table, finding chemical pseudo-homologues appears a practically meaningful issue. Due to this unique feature of the 7th row of the Periodic Table, the electronic structure of a Nh atom can be interpreted as a Fl atom with a hole in its closed 7p1⁄2-subshell. This observation seems to render astatine a closer chemical “relative” of Nh in comparison to the formal homologue Tl. Thus, At might be a plausible chemical species for model experiments aiming at finding the optimum experimental conditions for further explorations of the Nh chemistry. The predicted adsorption energies for At & AtOH on gold are 157 kJ/mol and 117 kJ/mol, respectively [2]. This confirms the experimental observation on the formation of AtOH molecules in presence of trace amounts of water and oxygen in the carrier gas. The mechanism of AtOH formation in thermochromatographic experiments remains to be established. In our recent paper we proposed that the adsorbed At atoms act as precursors to the formation of AtOH molecules on gold surface.
References
[1] Rusakov A. A., Demidov Yu. A., Zaitsevskii A. V. Estimating the adsorption energy of element 113 on a gold surface // Cent. Eur. J. Phys., V. 11, P. 1537-1540 (2013).
[2] Demidov Yu. A. et al. Uncovering Chemical Homology of Superheavy Elements: A Close Look at Astatine // ChemRxiv, DOI:10.26434/chemrxiv-2024-6nl51 (2024).
| Section | Nuclear physics (Section 1) |
|---|
