Americium

Schulz, W.W.; Penneman, R. A.

doi:10.1007/978-94-009-3155-8_1

Cited by 10 publications

(4 citation statements)

References 193 publications

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“…Absorption spectra for these americium glasses show unequivocally that the americium in the glass posses an oxidation of three. This solid state absorption spectrum matches well with solution spectra reported for Am (111) ions in different solution media [2,3], in the solid state [4] and the free ion energy levels for the Am3+ ion [5]. The major absorption maxima in the absorption spectrum were at 509, 784, and 834 nm (see Table I), with the main absorption being at 509 nm (well-established absorption for trivalent americium).…”

Section: Absorption Spectrasupporting

confidence: 86%

Fundamental Chemistry and Materials Science of Americium in Selected Immobilization Glasses

Haire

Stump

1996

MRS Proc.

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We have pursued some of the fundamental chemistry and materials science of americium in three glass matrices, two being high-temperature (850° and 1400°C melting points) silicate-based glasses and the third a sol-gel glass. Optical spectroscopy was the principal investigating tool in the studies. One aspect of this work was to determine the oxidation state exhibited by americium in these matrices, as well as factors that control and/or may alter this state. We have noted a correlation between the oxidation state of the f-elements in the two high-temperature glasses with their high-temperature oxide chemistries. One exception was americium: although americium dioxide is the stable oxide encountered in air, when this dioxide was incorporated into the high-temperature glasses, only trivalent americium was found in the products. When trivalent americium was used to prepare the sol-gel glasses at ambient temperature, and after these products were heated in air to 800°C, again only trivalent americium was observed. Potential explanations for the unexpected behavior of americium is offered in the context of its basic chemistry. Experimental spectra, spectroscopie assignments and other pertinent data obtained in the studies are discussed.

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Section: Absorption Spectrasupporting

confidence: 86%

Fundamental Chemistry and Materials Science of Americium in Selected Immobilization Glasses

Haire

Stump

1996

MRS Proc.

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“…The results summarized in Figure predict that uranyl(VI), neptunyl(VI), and plutonyl(VI) should exhibit substantial thermodynamic stability. These three actinyls are indeed well established as stable species in solution and solid state, as well as in gas phase. − The next three actinyls, americyl(VI), curyl(VI), and berkelyl(VI), are predicted to be marginally stable. Among these latter three, only Am(VI) has been definitively identified and it is metastable toward reduction in aqueous solution.…”

Section: Results and Discussionmentioning

confidence: 95%

“…The trend for An(III)–O is typical for a nearly constant (ionic and/or covalent) bond strength, with a gradual decrease in An(III)–O distance across the An series corresponding to the actinide contraction. In contrast, the entirely different trend for An(VI) is reminiscent of other actinide materials, − including the actinide metallic elements, where the bonding increases across the series to ca. Pu and then decreases for Am and later An as the 5f orbitals become increasingly spatially contracted, lower in energy, and generally less amenable to participation in bond formation with ligands such as oxygen.…”

Section: Results and Discussionmentioning

confidence: 97%

“…The actinyl dication, especially for An = U, has played a critical role in understanding binding in the actinides. , Hexavalent actinyl cations (AnO 2 2+ ) for An = U–Am are observed in solution and play an important role in the chemistry of the specific actinide. − Studies of the actinyl(VI) dications as gas phase actinyl ions and actinyl cation–cation interactions were previously reported. The question exists as to how far across the actinide period does actinyl behavior hold, especially given the different oxidation states that are present in the actinides.…”

Section: Introductionmentioning

confidence: 99%

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A Computational Assessment of Actinide Dioxide Cations AnO₂²⁺for An = U to Lr: The Limited Stability Range of the Hexavalent Actinyl Moiety, [O═An═O]²⁺

et al. 2020

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The isolated gas-phase actinide dioxide dications, AnO 2 2+ , were evaluated by DFT and coupled cluster CCSD(T) calculations for 12 actinides, An = U−Lr. CASSCF calculations were used to define the orbitals for the CCSD(T) calculations. The characteristic linear [OAnO] 2+ hexavalent actinyl(VI) was found to be the lowest energy structure for An = U, Np, and Pu, which also form stable actinyl(VI) species in solution and possibly for Am when spin−orbit effects are included. For Am, there is a divalent [An II (O 2 )] 2+ structure where the dioxygen is an end-on physisorbed η 1 -3 O 2 2 kcal/mol above the actinyl when spin−orbit effects are included which lower the energy of the actinyl structure. For An = Cm, Bk, and Lr, the lowest energy structure is trivalentwhere the dioxygen is a side-on superoxide, η 2 -O 2 − . For Cm, the actinyl is close in energy to the ground state when spin−orbit effects are included. For An = Cf, Es, Fm, Md, and No, the lowest energy structure is divalent [An II (O 2 )] 2+ where the dioxygen is an end-on physisorbed η 1 -3 O 2 . The relative energies suggest that curyl(VI) and berkelyl(VI), like well-known americyl(VI), might be stabilized by coordinating ligands in condensed phases. The results further indicate that for californyl and beyond, the actinyl(VI) moieties will probably be elusive even using strong donor ligands. The prevalence of low oxidation states (OSs) An(II) and An(III) for transplutonium actinides reflects stabilization of the 5f orbitals and validates established trends, including the remarkably high stability of divalent No. Bond distances and other parameters suggest maximum bond covalency around plutonyl(VI), with a particularly substantial decrease in bond strength between americyl(VI) and curyl(VI).

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Dictionary of Inorganic Compounds

Macintyre¹,

Daniel²,

Stirling³

1992

Dictionary of Inorganic Compounds

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Americium

Cited by 10 publications

References 193 publications

Fundamental Chemistry and Materials Science of Americium in Selected Immobilization Glasses

Fundamental Chemistry and Materials Science of Americium in Selected Immobilization Glasses

A Computational Assessment of Actinide Dioxide Cations AnO₂²⁺for An = U to Lr: The Limited Stability Range of the Hexavalent Actinyl Moiety, [O═An═O]²⁺

Dictionary of Inorganic Compounds

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Americium

Cited by 10 publications

References 193 publications

Fundamental Chemistry and Materials Science of Americium in Selected Immobilization Glasses

Fundamental Chemistry and Materials Science of Americium in Selected Immobilization Glasses

A Computational Assessment of Actinide Dioxide Cations AnO22+for An = U to Lr: The Limited Stability Range of the Hexavalent Actinyl Moiety, [O═An═O]2+

Dictionary of Inorganic Compounds

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A Computational Assessment of Actinide Dioxide Cations AnO₂²⁺for An = U to Lr: The Limited Stability Range of the Hexavalent Actinyl Moiety, [O═An═O]²⁺