Charles Dubois Coryell
(photo courtesy of Endre Toth)

A short write-up about Jill's research:

Rutherford Backscattering Spectrometry in the Investigation of Film Thickness and Uniformity on Chemically Modified Electrodes

Jill S. Pinter, Kenneth L. Brown, Paul A. DeYoung, and Graham F. Peaslee, Departments of Physics and Chemistry, Hope College, Holland Michigan 49422-9000.

Abstract Rutherford Backscattering Spectrometry (RBS) is an analytical technique that is used to determine the structure and composition of materials by impinging an ion beam on a sample and detecting the backscattered ions. RBS was used to characterize the intrinsic properties of a thin organic film composed of the ruthenium complex, [(bpy)₂Ru(5-phenNH₂)]Cl₂ • H₂O, on a glassy carbon electrode. The film was placed on the electrode surface via electropolymerization, such that the thickness of the film depends on the number of cycles of electropolymerization. A 1.7 MV Pelletron tandem particle accelerator at the Hope College Ion Beam Analysis Laboratory (HIBAL) was used to produce a beam of He²⁺ ions at 4.533 MeV. The beam was focused on the glassy carbon portion of the electrode with beam spot ~1 mm in diameter. The backscattered ions were detected at 169.7° by a silicon surface-barrier detector with a solid angle of ~4 msr. The results show that the film has an unusual composition of two layers: an outer layer of uniform ruthenium concentration, and an inner layer that starts at the same uniform ruthenium concentration, but decreases linearly to the electrode surface. The total amount of ruthenium present in the films was found to increase linearly with the number of electropolymerization cycles, and the same trend is observed for film thickness as well. The thickness of the films was determined to range between 1000 to 2500 nm for 5 to 20 electropolymerization cycles, respectively.

A short write-up about Gregory's research:

Online and Offline Gas-phase Chemistry of the Lighter Homologues of Rutherfordium

Gregory K. Pang  Mentors: Dr. Ch. Düllmann and Prof. H. Nitsche

Abstract: The gas phase chemistry of the group 4 elements (Zr, Hf) complexed with fluorinated β-diketones, specifically hexafluroacetylacetone (hfa) and trifluoroacetylacetone (tfa) was investigated. Two sets of experiments were performed: In the offline regime with macroamounts of stable isotopes, and in the online regime with short-lived isotopes (⁸⁵Zr, ^{158/162/165/169}Hf) produced in heavy-ion induced fusion reactions. These experiments were designed as a model study to prepare a future experiment with Rutherfordium (Rf, Z = 104). The offline studies comprised thermosublimatography experiments in a temperature gradient tube to investigate the thermochemistry of the Zr/Hf – hfa system. In the online regime, attention was paid to parameters that will be important in an experiment on a one-atom-at-a-time scale (in the case of Rf), namely maximum speed and yield. A maximum yield of ~90% for the 3.24 min. isotope ¹⁶⁹Hf was reached showing that the system is feasible for a Rf experiment. Successful application of this chemical system to a Rutherfordium experiment would result in the first transactinide compound with organic ligands.

Liquid scintillation counting (LSC) currently accounts for 71% of mixed radioactive, organic waste.  Development of an aqueous-based scintillation cocktail is desirable to reduce the amount of mixed waste produced. 
Polymerization of styrene-in-water microemulsions was used to entrap LSC fluor molecules, 2,5-diphenyloxazole (PPO) and p-bis(o-methylstyryl)-benzene (bis-MSB), in polystyrene nanoparticles to create an aqueous suspension.   These nanosuspensions were characterized using quasi-elastic light scattering and transmission electron microscopy and optimized with respect to PPO concentration, surfactant molecule(s), and styrene purification.  The nanosuspensions were used successfully to count various aqueous samples, including biological samples of digested blood and tissue.  Optimized nanosuspensions yielded counting efficiencies for ¹⁴C-acetic acid of up to 46% compared to commercially available LSC cocktail.

There is a great potential for use of supercritical (SC) solvents (in particular, SC-CO₂) for the extraction of unstable isotopes from nuclear waste. The main concern when handling solvents and reaction vessels after extraction of this waste is their level of radioactivity. When using supercritical solvents such as CO₂, in which UO₂ is extremely soluble, the temperature and pressure of the solvent can be adjusted quite easily to change its density (drastically!). High SC-CO₂ density thermalizes radioactive decay products (radiation) so that they do not reach the vessel walls (or the outside)

Using the MuSR technique at TRIUMF, Vancouver, BC, the positive muon was injected into supercritical carbon dioxide at varying densities. Its intra- track spur formation (the degree to which the muon ionizes the solvent (CO₂) and those high-energy electrons travel, thus forming radiation of their own) was closely studied using a MuSR Spectrometer.

Better understanding of  "spur formation" in supercritical CO₂ allows us to tune its temperature and pressure to the ideal levels for the safe use in UO₂ extraction.