Simulation of Thermochromatographic Processes by the Monte Carlo Method

Zvára, I.

doi:10.1524/ract.1985.38.2.95

Cited by 132 publications

(152 citation statements)

References 5 publications

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“…The minimum value for the number of events D, which are detected in COMPACT I at this limit, is 0.76 out of 2, i.e., 38%. To convert this into a limit for −H ads Au (Fl), the deposition pattern for both observed Fl isotopes along the entire COMPACT array was simulated for various values of −H ads Au (Fl) using MCS 41 . All simulations with −H ads Au (Fl) ≥48 kJ·mol -1 resulted in distributions where at least 38% of all events decayed in COMPACT I.…”

Section: Discussionmentioning

confidence: 99%

Superheavy Element Flerovium (Element 114) Is a Volatile Metal

et al. 2014

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Superheavy Element Flerovium (Element 114) Is a Volatile MetalAccess to the published version may require subscription. Superheavy Element Flerovium (Element 114) is a Volatile MetalAlexander Yakushev †, , Jacklyn M. ABSTRACT: The electron shell structure of superheavy elements, i.e., elements with atomic number Z ≥ 104, is influenced by strong relativistic effects caused by the high Z. Early atomic calculations on element 112 (copernicium, Cn) and element 114 (flerovium, Fl) having closed and quasiclosed electron shell configurations of 6d 10 7s 2 and 6d 10 7s 2 7p 1/2 , respectively, predicted them to be noble gas-like due to very strong relativistic effects on the 7s and 7p 1/2 valence orbitals. Recent fully relativistic calculations studying Cn and Fl in different environments suggest them to be less reactive compared to their lighter homologs in the groups, but still exhibiting a metallic character. Experimental gassolid chromatography studies on Cn have, indeed, revealed a metal-metal bond formation with Au. In contrast to this, for Fl, the formation of a weak bond upon physisorption on a Au surface was inferred from first experiments. Here, we report on a gas-solid chromatography study of the adsorption of Fl on a Au surface. Fl was produced in the nuclear fusion reaction 244 Pu( 48 Ca, 3-4n) 288,289 Fl and was isolated in-flight from the primary 48 Ca beam in a physical recoil separator. The adsorption behavior of Fl, its nuclear α-decay product Cn, their lighter homologs in groups 14 and 12, i.e., Pb and Hg, and the noble gas Rn were studied simultaneously by isothermal gas chromatography and thermochromatography. Two Fl atoms were detected. They adsorbed on a Au surface at room temperature in the first, isothermal part, but not as readily as Pb and Hg. The observed adsorption behavior of Fl points to a higher inertness compared to its nearest homolog in the group, Pb. However, the measured lower limit for the adsorption enthalpy of Fl on a Au surface points to the formation of a metal-metal bond of Fl with Au. Fl is the least reactive element in the group, but still a metal.

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Section: Discussionmentioning

confidence: 99%

Superheavy Element Flerovium (Element 114) Is a Volatile Metal

et al. 2014

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“…Because nuclides with very different half-lives were used -a parameter which can strongly influence thermochromatographic results [97,188] -it was almost impossible to precisely determine relative volatilities in the pioneering experiments. Recently, isothermal gas-chromatographic experiments established a higher volatility of Rf chlorides as compared with Hf chlorides [183,185,189].…”

Section: Gas-phase Chemistrymentioning

confidence: 99%

“…In Monte Carlo simulations of the chromatographic process adsorption enthalpies (∆H 0 a (T)) for single molecules on the column quartz surface are obtained by searching a best fit to the experimental data and varying ∆H a as the free parameter [99,188]. A compilation ( [133] and Fig.…”

Section: Gas-phase Chemistrymentioning

confidence: 99%

“…8 as (normalized) relative yields together with data from tracer experiments and with Monte Carlo simulations using a microscopic model [188] to determine standard adsorption enthalpies. This result shows that Bh behaves like a member of group 7 of the PTE and forms a volatile oxide chloride, presumably BhO 3 Cl, which is less volatile than the compounds of the lighter homologs.…”

Section: Bohrium (Bh Element 107)mentioning

confidence: 99%

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Chemistry of superheavy elements

Schädel

2012

Radiochimica Acta

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Summary. The chemistry of superheavy elements -or transactinides from their position in the Periodic Table -is summarized. After giving an overview over historical developments, nuclear aspects about synthesis of neutron-rich isotopes of these elements, produced in hot-fusion reactions, and their nuclear decay properties are briefly mentioned. Specific requirements to cope with the one-atom-at-a-time situation in automated chemical separations and recent developments in aqueous-phase and gas-phase chemistry are presented. Exciting, current developments, first applications, and future prospects of chemical separations behind physical recoil separators ("pre-separator") are discussed in detail. The status of our current knowledge about the chemistry of rutherfordium (Rf, element 104), dubnium (Db, element 105), seaborgium (Sg, element 106), bohrium (Bh, element 107), hassium (Hs, element 108), copernicium (Cn, element 112), and element 114 is discussed from an experimental point of view. Recent results are emphasized and compared with empirical extrapolations and with fully-relativistic theoretical calculations, especially also under the aspect of the architecture of the Periodic Table.

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“…Using a Monte Carlo procedure [73] simulating the migration of a volatile species along the column with the adsorption enthalpy −ΔH a on the column surface as the only free parameter yielded the dashed curves in Fig. 11 when −ΔH a = 62 kJ/mol was used.…”

Section: Thermochromatographymentioning

confidence: 99%

Gas chemical investigation of hafnium and zirconium complexes with hexafluoroacetylacetone using preseparated short-lived radioisotopes

Düllmann

Gregorich²,

Pang

et al. 2009

Radiochimica Acta

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Zirconium / Hafnium / Hexafluoroacetylacetonates / Thermochromatography / Isothermal gas chromatogaphy / Physical preseparation Summary. 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 −ΔH a = (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 165 Hf , 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.

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Simulation of Thermochromatographic Processes by the Monte Carlo Method

Cited by 132 publications

References 5 publications

Superheavy Element Flerovium (Element 114) Is a Volatile Metal

Superheavy Element Flerovium (Element 114) Is a Volatile Metal

Chemistry of superheavy elements

Gas chemical investigation of hafnium and zirconium complexes with hexafluoroacetylacetone using preseparated short-lived radioisotopes

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