Abstract
Volatile metal complexes of the group 4 elements Zr and Hf with hexafluoroacetylacetonate (hfa) have been studied using short-lived radioisotopes of the metals. The new technique of physical preseparation has been employed where reaction products from heavy-ion induced fusion reactions are isolated in a physical recoil separator – the Berkeley Gas-filled Separator in our work – and made available for chemistry experiments. Formation and decomposition of M(hfa)4 (M=Zr, Hf) has been observed and the interaction strength with a fluorinated ethylene propylene (FEP) Teflon surface has been studied. From the results of isothermal chromatography experiments, an adsorption enthalpy of -ΔHa=(57±3) kJ/mol was deduced. In optimization experiments, the time for formation of the complex and its transport to a counting setup installed outside of the irradiation cave was minimized and values of roughly one minute have been reached. The half-life of 165Hf, for which conflicting values appear in the literature, was measured to be (73.9±0.8) s. Provided that samples suitable for α-spectroscopy can be prepared, the investigation of rutherfordium (Rf), the transactinide member of group 4, appears possible. In the future, based on the studies presented here, it appears possible to investigate short-lived single atoms produced with low rates ( e.g. , transactinide isotopes) in completely new chemical systems, e.g. , as metal complexes with organic ligands as used here or as organometallic compounds.
Highlights
1.1 Gas phase chemistry with transactinidesGas phase chemical methods have proven powerful for the investigation of the heaviest elements, called the transactinides (TAN, Z ≥ 104)
Different experiment series were conducted mainly i) to investigate the formation of volatile species in the chosen chemical system and to find the optimum experimental parameters for the reactions to be as fast as possible, ii) to study the thermal stability of the formed volatile species with the goal of determining the chemical species through comparison with data available from the study of macroamounts, and iii) to study their interaction with fluorinated ethylene propylene (FEP) Teflon and quartz in gas chromatography experiments
The technique can be expected to be applicable to transactinides
Summary
1.1 Gas phase chemistry with transactinidesGas phase chemical methods have proven powerful for the investigation of the heaviest elements, called the transactinides (TAN, Z ≥ 104). Element 112 was transported in its volatile elemental state [3] Inherent to both of these approaches are harsh conditions as far as chemistry is concerned: either high temperatures are needed to release the species from the aerosol particles used in the gas-jet; or a plasma is present, which is formed by the intense heavyion beam that is passing through the gas volume where the EVRs are thermalized. These conditions prevented studies of more complex molecules like organometallic compounds or volatile metal complexes which are generally rather thermally unstable
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