Development of Online Chemistry for Rutherfordium (Element 104): Commissioning of a Gas Stopper and Extraction Chromatography of Rutherfordium Homologs (Zirconium and Hafnium)

Abstract

The chemical and physical properties of the heaviest elements are of particular interest because relativistic effects increase as proton number squared. Transactinides, elements where relativistic effects are expected to be the largest, do not exist naturally; they are produced via fusion-evaporation reactions. The products of these reactions must be degraded down to sub-eV energies for chemical studies. At the Cyclotron Institute at Texas A&M University, a device for the thermalization of fusion-evaporation reaction products, the Recoil Transfer Chamber (RTC), has been designed, fabricated, and characterized. The design of this device is based on a gas stopper previously used at the National Superconducting Cyclotron Laboratory. This device uses a combination of laminar gas flow and static electric field to effectively transport the thermalized ions to the appropriate chemistry experiment. The RTC’s efficiency was determined using products of the ^118Sn(^40Ar, 6n)^152Er reaction. An efficiency of 34 ± 5% was directly measured.

Additionally, extraction chromatographic systems for the future chemical characterization of Rf were optimized offline. Trace quantities of long-lived radioactive homologs of Rf, ^89Zr (t1/2 = 78.41 hr) and ^175Hf (t1/2 = 70 d), were used to mimic the “one-atom-at-a-time” nature of transactinide chemistry. The extraction behavior of Zr and Hf was studied in HCl, HNO3, and H2SO4 using TEVA (a trioctyl and tridecyl methyl ammonium-based resin) and UTEVA (a diamyl amylphosphonate-based resin). Batch uptake studies were performed to determine which systems could separate Zr and Hf. Both resins showed the most promise in an HCl media. A separation factor of 18 ± 8 in 8.4 M HCl was measured using TEVA, while a separation factor of greater than 9.4 in 5.6 M HCl was measured using UTEVA. Offline, both TEVA and UTEVA column studies in HCl had good intergroup separation and showed viability for future extraction chromatographic studies of Rf.