[en] The work of the High Flux Isotope Reactor and the Transuranium Processing Plant in the US transplutonium element program is described

[en] It is noted that the energies and intensities of transitions observed in the optical spectra of lanthanide (Ln) and actinide (An) compounds can typically be measured with a high degree of accuracy. The observed transitions can then be directly represented as upper state energy levels where the structure is induced by the environment. A discussion is presented of the systematic theoretical interpretation of these transitions both in terms of energy level structure and transition probability. Particularly for the trivalent lanthanides and actinides, the detail to which the interpretation can be carried is unique in the periodic table. The electronic structure of organometallic lanthanides and actinides is emphasized in the discussion. It is made clear that this type of ligand does not present any unique interpretive problems. The basic framework of the interpretation is not dependent upon the specific ionic environment. On the other hand, organometallic compounds represent a particularly interesting group in which to study excited state relaxation

[en] In recent years sufficient new spectra of actinides in their numerous valence states have been measured to encourage a broader scale analysis effort than was attempted in the past. Theoretical modelling in terms of effective operators has also undergone development. Well established electronic structure parameters for the trivalent actinides are being used as a basis for estimating parameters in other valence states and relationships to atomic spectra are being extended. Recent contributions to our understanding of the spectra of 4+ actinides have been particularly revealing and supportive of a developing general effort to progress beyond a preoccupation with modelling structure to consideration of the much broader area of structure-bonding relationships. We summarize here both the developments in modelling electronic structure and the interpretation of apparent trends in bonding. 60 refs., 9 figs., 1 tab

[en] Work on spectra and electronic structure of Es³⁺ is reviewed. Laser-excited fluorescence spectroscopy was used to study Es³⁺-doped LaCl₃ crystals; fluorescence transitions and lifetimes were determined. A complete ground-state splitting diagram was also constructed for Es³⁺: LaCl₃. Some data on excited states of Fm³⁺ are also included. 12 figures

[en] The optical spectra of actinide ions in the compound AnCl₃ and doped into single crystal LaCl₃ were interpreted in terms of transitions within 5f^N configurations. Energy-level calculations were carried out using an effective operator Hamiltonian, the parameters of which were determined by fitting experimental data. Atomic and crystal-field matrices were diagonalized simultaneously assuming an approximate D_3h site symmetry. The spectroscopic data were taken from the literature but in most cases supplemented by unpublished measurements in absorption and in fluorescence. Spectroscopic data for each ion were analyzed independently, then the model parameters were intercompared and in many cases adjusted such that in the final fitting process the principal interactions showed uniform trends in parameter values with increasing atomic number. Consistent with analyses of the spectra of lanthanide ions in both LaCl₃ and LaF₃, abrupt changes in magnitude of certain crystal-field parameters were found near the center of the 5f^N-series. This resulted in two groups of parameter values, but with consistent trends for both halves of the series, and generally very good agreement between observed and computed energies. A new energy level chart based on computed crystal-field level energies for each trivalent actinide ion has been prepared. in addition, the parameters of the atomic part of each 5f^N Hamiltonian were used to calculate the matrix elements of U^(λ) for selected transitions. The values were tabulated to facilitate calculation of intensity-related parameters for 5f^N-transitions using the Judd-Ofelt theory. 44 refs., 10 figs., 3 tabs

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[en] The challenging opportunity to develop insights into both atomic structure and the effects of bonding in compounds makes the study of actinide spectroscopy a particularly fruitful and exciting area of scientific endeavor. It is also the interpretation of f-element spectra that has stimulated the development of the most sophisticated theoretical modeling attempted for any elements in the periodic table. The unique nature of the spectra and the wealth of fine detail revealed make possible sensitive tests of both physical models and the results of Hartree-Fock type ab initio calculations. This paper focuses on the unique character of heavy actinide spectroscopy. It discusses how it differs from that of the lighter member of the series and what are the special properties that are manifested. Following the introduction, the paper covers the following: (1) the role of systematic studies and the relationships of heavy-actinide spectroscopy to ongoing spectroscopic investigations of the lighter members of the series; (2) atomic (free-ion) spectra which covers the present status of spectroscopic studies with transplutonium elements, and future needs and directions in atomic spectroscopy; (3) the spectra of actinide compounds which covers the present status and future directions of spectroscopic studies with compounds of the transplutonium elements; and other spectroscopies. 1 figure, 2 tables

[en] This report provides a summary of theoretical and experimental studies of actinide spectra in condensed phases. Much of the work was accomplished at Argonne National Laboratory, but references to related investigations by others are included. Spectroscopic studies of the trivlent actinides are emphasized, as is the use of energy level parameters, evaluated from experimental data, to investigate systematic trends in electronic structure and other properties. Some reference is made to correlations with atomic spectra, as well as with spectra of the (II), (IV), and higher valence states. 207 refs., 39 figs., 38 tabs

[en] Two types of correlations with experimental results are reported. For even-f-electron systems, a center of gravity was computed based on the energies of the observed states, and calculated optimized sets of atomic energy level parameters. For odd-electron systems complete crystal field calculations were performed in which parameters of both the atomic and crystal-field parts of the interaction were adjusted to experimental data. The result is a set of eigenvectors for all the ionic states in each configuration. Spectroscopic results for all lanthanides doped into LaF₃ (In³⁺:LaF₃) except Pm³⁺ and Eu³⁺ are reported. 89 references, 29 tables