Disputas: Fereshteh Samadani

Prøveforelesning

Bedømmelseskomité

Professor Christian Ekberg, Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden
Cand. Scient Dag Øistein Eriksen, d.o.eriksen@kjemi.uio.no
Professor Per Hoff, Kjemisk institutt, UiO, per.hoff@kjemi.uio.no

Leder av disputas:  Professor Carl Henrik Gørbitz

Veileder:  Jon Petter Omtvedt og Tor Bjørnstad

Sammendrag

A model experiment for the chemical study of the superheavy (SHE) element number 108, hassium, was developed and tested in a pilot experiment using its lighter homologue, osmium. The automated liquid-liquid extraction system SISAK was used to study the distribution of OsO4 between dilute solutions of NaOH and toluene as a model for hassium. The acidic constants of Os (VIII) acid were determined from the study. These experiments were performed with the short-lived osmium nuclides at the Oslo Cyclotron Laboratory (OCL) and Helmholtzzentrum für Schwerionenforschung GmbH (GSI).
The relativistic effects cause the SHEs (Z ≥ 104) to behave differently from what is expected by extrapolations from classical rules of Periodic Table. SHEs are all manmade elements produced in extremely low rates, on the order of a few atoms per hour or even day, and their half-lives are only a few minutes or seconds, or even shorter. Only a few laboratories in the world, equipped with huge and expensive heavy ion accelerators, are able to produce such exotic elements. Accordingly, performing any experiment with these elements will not be straightforward. To develop such experiments, model experiments using homologues (chemical elements which are expected to behave in a similar way) of the SHEs are performed. Such experiments can be performed much easier and cheaper. In an eventual experiment with the SHEs, the results from the experiments on the homologues are compared.
The study of hassium's chemical behaviour is of interest to evaluate the theoretical models describing the chemical behaviour of elements. The experiments showed that the proposed setup in this work is suitable for performing a real hassium experiment. However, hassium nuclides are currently produced in the rates of about 1 atom per day. Thus the experiment has to be run for weeks to gain any meaningful result.

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