43 Search Results

High-lying Rydberg and autoionizing (AI) states of thorium (Th) have been studied via resonance laser ionization spectroscopy at both TRIUMF Canada’s particle accelerator center and Oak Ridge National Lab (ORNL). Multiple Rydberg series converging to the ionization potential (IP) were observed via different stepwise laser excitation schemes and were assigned to be the 6d²7s (⁴F_3/2) np, nd, and nf series. Analysis of these series enabled the determination of the IP to be 50 868.735(54) cm⁻¹, which improved the precision by two orders of magnitude over the current adopted NIST value of 50 867(2) cm⁻¹. Additionally, four AI Rydberg series weremore » identified and assigned to nf and nd series converging to the 6d²7s ⁴F_5/2 and 6d7s^{2 2}D_3/2 metastable states of Th⁺. In conclusion, the measured energies of the Rydberg and AI Rydberg states are reported, and observed perturbations within the series are discussed.« less

Reaction of 4 equiv. of [Li(TMEDA)]₂[1,2-S₂C₆H₄] with [ThCl₄(DME)₂] or [UCl₄(THF)₃] in THF results in formation of [Li(THF)₂]₄[An(1,2-S₂C₆H₄)₄] (An = Th, 1; An = U, 2), whereas reaction of 4 equiv. of [Li(TMEDA)]₂[1,2-S₂C₆H₄] with UCl₄ in Et₂O results in formation of [Li(TMEDA)]₄[U(1,2-S₂C₆H₄)₄] (3). Complexes 1–3 represent the first reported benzenedithiolate complexes of the actinides. Here, they were characterized by NMR spectroscopy and X-ray crystallography. In the solid state, complexes 1–3 exhibit triangular dodecahedral geometries about their actinide centers. Additionally, their Li⁺ cations are bound by two sulfur atoms of adjacent [1,2-S₂C₆H₄]²⁻ ligands, in addition to two solvent donor atoms. In solution,more » complexes 2 and 3 exhibit spectral data consistent with S₄ symmetry (and non-exchanging Li⁺ sites), whereas complex 1 exhibits spectral properties consistent with labile Li⁺ cations.« less

Advances in battery technology have been impeded by the voltage constraints of electrolytes. Here, in this study, we present a high-energy all-solid-state battery design featuring >5 V operation and an ultrahigh areal capacity of 35.3 mAh cm⁻²; these attributes were enabled by a highly conductive and ultrahigh-voltage stable fluoride solid electrolyte, LiCl–4Li₂TiF₆ (1.7 × 10⁻⁵ S cm⁻¹ at 30 °C). LiCl–4Li₂TiF₆ shields high-voltage spinel oxide cathodes, achieving 106 mAh g⁻¹ at 2C with 75.2% retention over 500 cycles for LiNi_0.5Mn_1.5O₄, sharply contrasting with the conventional LiNbO₃ counterpart, which decomposes and fails to prevent detrimental interfacial degradation. The efficacy of LiCl–4Li₂TiF₆more » is validated across various systems, including LiCoMnO₄, LiFe_0.5Mn_1.5O₄ and pouch-type LiNi_0.5Mn_1.5O₄||Li (or Ag–C) all-solid-state batteries, and further demonstrated by operability down to 2.3 V with 258 mAh g⁻¹ and ultrathick 1.8-mm electrodes. This shielding layer with >5 V stability introduces a transformative design paradigm by revisiting the previously forbidden high-voltage cathodes.« less

Rationale: Mass spectrometric measurement of the ²³⁰Th/²³⁴U ratio to calculate the purification age of enriched uranium is typically conducted via a combination of ion counters and faraday detectors, thus requiring an inter-detector calibration scheme. Here, our aim is to understand whether the pursuit of a simplified measurement scheme involving only faraday detectors is feasible. Methods: We investigate the possibility of determining U-Th model ages for two enriched uranium standards (NBL U630 and U850) by direct measurement of the ²³⁰Th/²³⁴U ratio (without chromatographic separation or isotope dilution) on a ThermoFisher Scientific Neoma MC-ICP-MS utilizing both solution and laser ablation (LA)-based samplingmore » techniques and an all-faraday detector configuration. Results: For the solution mode analyses conducted on aliquots containing sub μg/mL total U, we produce composite average ²³⁰Th/²³⁴U model dates of May 19, 1988 (± 351 days), and March 26, 1961 (± 2.5 years) using the directly measured ²³⁰Th/²³⁴U ratios for the NBL U630 and U850 uranium standards, which have certified purification dates of June 6, 1988 (± 190 days), and December 31, 1957 (± 36.5 days), respectively. The ages produced by LA-based sampling of dried residues of the same standards deposited onto cotton TexWipes are less accurate and of poorer precision (June 23, 2004 ± 8.7 years for U630 and December 21, 1965 ± 7.9 years for U850) but still yield meaningful information in regards to the purification date. Conclusions: We believe that further refinement of the all faraday detector measurement approach to include development of a more robust Th/U relative sensitivity factor determination, signal cutoff selection, and data processing protocols will allow for this approach to be confidently applied to enriched uranium materials with unknown purification histories. Potential advantages of the method include the reduced sample handling and infrastructure requirements as well as the ability to simultaneously generate a broad picture of the uranium isotopic composition in tandem with the U-Th age determination.« less

Actinide complexes containing the simplest borohydrides (BH₄)^1- and (MeBH₃)^1- can exhibit remarkably highly volatility, which creates unique hazards and handling challenges, especially when making measurements on solid samples under vacuum. Here we describe efforts to prepare new actinide borohydride complexes with attenuated volatility by adding bulkier benzyl (Bn) and cyclohexyl (Cy) substituents to boron. Reactions of ThCl₄, UI₃(thf)₄, and NdI₃ with the mixed alkali metal salt Li/K(BnBH₃)(thf)_n yielded Th(BnBH₃)₄(thf)₂, U(BnBH₃)₄(thf)₂, and K[Nd(BnBH₃)₄], respectively. Notable amongst these, the reaction with UI₃(thf)₄ proceeds via oxidation of U(III) to U(IV) despite the presence of reducing borohydride ligands. Similarly, reactions of the same metalmore » halides with four equivalents of Li(CyBH₃)(Et₂O)_n yielded Th(CyBH₃)₄, U(CyBH₃)₄(thf)₂, and [Li(Et₂O)₃][Nd(CyBH₃)₄]. Single crystal X-ray diffraction studies of the M(BnBH₃)₄(thf)₂ complexes with M = Th and U confirmed their formulations. Furthermore, the complexes have approximate D_2d point group symmetry and adopt bicapped hexagonal antiprismatic coordination geometries with axial thf ligands and κ³-BnBH₃ ligands bound in the equatorial plane. K[Nd(BnBH₃)₄] and [Li(Et₂O)₃][Nd(CyBH₃)₄], which were prepared for comparison to U(III) complexes that were unsuccessfully targeted, were also structurally characterized to reveal complex anions with tetrahedral arrangements of trihydroborate ligands bound to Nd(III). Crystals obtained for Th(CyBH₃)₄ and U(CyBH₃)₄(thf)₂ were not suitable for XRD studies, but ¹H and ¹¹B NMR spectra were consistent with their formulations. Collectively, these complexes represent rare examples of structurally characterized f-element trihydroborate complexes with carbon substituents other than methyl.« less

Porous metal–organic frameworks (MOFs) have emerged as highly promising adsorbents for capturing radioiodine, a predominant fission product released during nuclear fuel reprocessing. However, systematic investigations into the correlation between MOF structure and iodine uptake capacity remain scarce. Here, we present a novel approach to enhance the iodine adsorption capacity of MOFs by optimizing linker functionalization. Using ligand-functionalized thorium-based MOFs as a structural platform, we demonstrate that ortho-amino-substitution near the node of the dicarboxylate linker significantly increases iodine adsorption capacity compared to meta-amino-substitution, where the amino groups are directed away from the node. Specifically, ortho-substituted Th-UiO-68-3,3”-(NH₂)₂ exhibits higher iodine uptake capacitiesmore » than the meta-substituted Th-UiO-68-2,2”-(NH₂)₂ via both vapor diffusion-based (2.042 vs. 1.087 g/g) and solution-based (0.841 vs. 0.784 g/g) processes. Notably, the I₂ vapor adsorption capacity (2.042 g/g) of Th-UiO-68-3,3”-(NH₂)₂ represents the second highest among all reported Th-MOFs. Pair distribution function (PDF) studies reveal that the superior iodine uptake performance of ortho-functionalized MOFs can be attributed to the reduced steric hindrance of the amino groups compared with the meta-substituted variants. Finally, this research highlights how positional isomerism and its subtle alterations can significantly influence host–guest interactions, extending beyond simple structural considerations.« less

Plasma has been proposed as an alternative strategy to treat organic contaminants in brines. Chemical degradation in these systems is expected to be partially driven by halogen oxidants, which have been detected in halide-containing solutions exposed to plasma. In this study, we characterized specific mechanisms involving the formation and reactions of halogen oxidants during plasma treatment. Here, we first demonstrated that addition of halides accelerated the degradation of a probe compound known to react quickly with halogen oxidants (i.e., para-hydroxybenzoate) but did not affect the degradation of a less reactive probe compound (i.e., benzoate). This effect was attributed to themore » degradation of para-hydroxybenzoate by hypohalous acids, which were produced via a mechanism involving halogen radicals as intermediates. We applied this mechanistic insight to investigate the impact of constituents in brines on reactions driven by halogen oxidants during plasma treatment. Bromide, which is expected to occur alongside chloride in brines, was required to enable halogen oxidant formation, consistent with the generation of halogen radicals from the oxidation of halides by hydroxyl radical. Other constituents typically present in brines (i.e., carbonates, organic matter) slowed the degradation of organic compounds, consistent with their ability to scavenge species involved during plasma treatment.« less

Magmatic gas exsolving during late-stage cooling of shallow magmas has been considered an important facilitator of low-pressure alteration and metal transport. However, the chemical properties of such gas, particularly its metal transport mechanisms and capacity, remain elusive. Trace elements in minerals produced by gas-mediated surface reaction or precipitation from gas capture details of gas composition and reaction pathways. However, interpretation of mineral trace element contents is dependent on understanding crystallographic controls on gas/mineral partitioning. Here, this work investigates the structural accommodation of As, Mn, Ga, Ge, Fe, and Ti in vapor-deposited topaz of vesicular topaz rhyolite from the Thomas Range,more » Utah, through single-crystal synchrotron microbeam X-ray techniques on picogram quantities of those trace elements. X-ray absorption near edge structure (XANES) data indicates that these elements are incorporated into topaz as As⁵⁺, Fe³⁺, Mn³⁺, Ti⁴⁺, Ga³⁺, and Ge⁴⁺. Extended X-ray absorption fine structure (EXAFS) analysis for these trace elements, compared to EXAFS of structural Al and Si, reveals that As⁵⁺ and Ge⁴⁺ are incorporated directly into the tetrahedral site of the topaz structure, with the octahedral site accommodating Mn³⁺, Fe³⁺, Ga³⁺, and Ti⁴⁺. For As⁵⁺ and Fe³⁺, the structural impact of substitution extends to at least second neighbors (other elements were only resolvable to first neighbors). Further interpretation of the EXAFS results suggests that the substitution of Ti⁴⁺ results in increased distortion of the octahedral site, while the other trace elements induce more uniform expansion correlating in magnitude to their ionic radius. Comparison of quantified X-ray fluorescence (XRF) data for two topaz crystals from this rhyolite reveals variable trace element concentrations for As⁵⁺, Fe³⁺, Ga³⁺, and Ti⁴⁺, reflective of a source gas undersaturated in these trace elements changing in concentration over the period of topaz deposition. The identical Ge⁴⁺ content of the two topaz crystals suggests that Ge⁴⁺ in the gas was buffered by the growth of another Ge⁴⁺-bearing phase, such as quartz. The very low Mn³⁺ content in the topaz crystals does not reflect the abundance of Mn³⁺ in the gas (saturation of Mn is evidenced by coexisting bixbyite). Instead, it suggests a strong Jahn-Teller inhibitory effect to the substitution of Mn³⁺ for Al³⁺ in the distorted octahedral site of topaz. It is proposed that exsolution of an HF-enriched gas from cooling rhyolitic magma led to local scouring of Al, Si, and trace metals from the magma. Once topaz crystals nucleated, self-catalyzed reactions that recycle HF led to continued growth of topaz.« less

Positively charged metal–ammonia complexes are known to host peripheral, diffuse electrons around their molecular skeleton. The resulting neutral species form materials known as expanded or liquid metals. Alkali, alkaline earth, and transition metals have been investigated previously in experimental and theoretical studies of both the gas and condensed phase. This work is the first ab initio exploration of an f-block metal–ammonia complex. The ground and excited states are calculated for Th0–3+ complexes with ammonia, crown ethers, and aza-crown ethers. For Th3+ complexes, the one valence electron Th populates the metal’s 6d or 7f orbitals. For Th0–2+, the additional electrons prefermore » occupation of the outer s- and p-type orbitals of the complex, except Th(NH3)10, which uniquely places all four electrons in outer orbitals of the complex. Although thorium coordinates up to ten ammonia ligands, octa-coordinated complexes are more stable. Crown ether complexes have a similar electronic spectrum to ammonia complexes, but excitations of electrons in the outer orbitals of the complex are higher in energy. Aza-crown ethers disfavor the orbitals perpendicular to the crowns, attributed to the N-H bonds pointing along the plane of the crowns.« less