Actinide energies

An examination of the trivalent actinide energy level schemes reveals several possibilities for laser action. These are discussed in light of the general properties cited above. Only conventional broadband optical pump sources are considered. Obviously with selective laser excitation and cascade lasing schemes, stimulated emission from many more states should be possible, but these special situations are too numerous to be considered in detail here. 

Dolg M, Cao X. Accurate Relativistic Small-Core Pseudopotentials for Actinides. Energy Adjustment for Uranium and First Applications to Uranium Hydride. The Journal of Physical Chemistry A. 2009 113(45) 12573-12581. 

M. Dolg and X. Cao, Aeeurate relativistic small-core pseudopotentials for actinides. Energy-adjustment for uranium and first applications to uranium hydride. J. Phys. Chem. A, 113, 12573-12581 (2009). 

Molecular mechanics force fields are sometimes parameterized to describe lanthanides and actinides. This has been effective in describing the shape of the molecule, but does not go very far toward giving systematic energies. A few semiempirical methods have been parameterized for these elements, but they have not seen widespread use. 

Filling up the 4/ orbital is a feature of the lanthanides. The 4/ and 5d orbitals are of similar energy so that occasionally, as in La, Ce and Gd, one electron goes into 5d rather than 4f. Similarly, in the actinides, Ac to No, the 5/ subshell is filled in competition with 6d. 

Thorium, uranium, and plutonium are well known for their role as the basic fuels (or sources of fuel) for the release of nuclear energy (5). The importance of the remainder of the actinide group Hes at present, for the most part, in the realm of pure research, but a number of practical appHcations are also known (6). The actinides present a storage-life problem in nuclear waste disposal and consideration is being given to separation methods for their recovery prior to disposal (see Waste treati nt, hazardous waste Nuclear reactors, waste managet nt). 

The practical use of three actinide nucHdes, Pu, and as nuclear fuel is weU known (5,9). When a neutron of any energy strikes the nucleus of... 

The throwaway fuel cycle does not recover the energy values present ia the irradiated fuel. Instead, all of the long-Hved actinides are routed to the final waste repository along with the fission products. Whether or not this is a desirable alternative is determined largely by the scope of the evaluation study. For instance, when only the value of the recovered yellow cake and SWU equivalents are considered, the world market values for these commodities do not fully cover the cost of reprocessing (2). However, when costs attributable to the disposal of large quantities of actinides are considered, the classical fuel cycle has been the choice of virtually all countries except the United States. 

Thorium [7440-29-1], a naturally occurring radioactive element, atomic number 90, atomic mass 232.0381, is the second element of the actinide ( f) series (see Actinides AND transactinides Radioisotopes). Discovered in 1828 in a Norwegian mineral, thorium was first isolated in its oxide form. For the light actinide elements in the first half of the. series, there is a small energy difference between and 5/ 6d7 electronic configurations. Atomic spectra... 

J. Fuger and co-workers. The Actinide Aqueous Inorganic Complexes Part 12, International Atomic Energy Agency, Vienna, 1992. 

Uranium is the fourth element of the actinide (SJ series. In the actinide series the electrons are more effectively shielded by the Is and 7p electrons relative to the 4f electrons (shielded by 6s, 6p) in the lanthanide (4p series. Thus, there is a greater spatial extension of 5f orbitals for actinides than 4f orbitals for lanthanides. This results in a small energy difference between and 5/ 6d7s electronic configurations, and a wider range of oxidation states is... 

A critical assessment of the chemical thermodynamic properties of the actinides and their compounds is presently being prepared by an international team of scientists under the auspices of the International Atomic Energy Agency (Vienna). As a result of this effort, four publications (1, 2, 3, 5) have already become available and a further ten 6-T4), including the halides (8) and aqueous complexes with Tnorganic ligands (12),... 

Relatively few thermodynamic studies have been performed on compounds involving Th, U and Pu with noble metals. Most of the previous work has involved electrochemical cell determinations of free energies of formation, hence little has been published concerning the sublimation behavior of actinide intermetallics. 

Figure 2. Temperature dependence of free energy of formation,AG of actinide intermetallics.

Oetting, F. L. Rand, M. H. Ackermann, R. J. "The Chemical Thermodynamics of Actinide Elements and Their Compounds," International Atomic Energy Agency, Vienna, 1976. 

The spectrometer was a Physical Electronics Model 548 modified for emplacement in a glovebox so that actinide samples could be examined. Spectra were taken using AIK radiation (1486.6 eV). The overall energy resolution of tne spectrometer was 1.2 eV using an analyzer pass energy of 25 eV. The spectrometer control was interfaced to a Nicolet 1180 minicomputer providing automatic data acquisition and analysis capability. 

In what follows we briefly review some of the previous attempts to analyze the available spectra of plutonium (6). In addition, we estimate energy level parameters that identify at least the gross features characteristic of the spectra of plutonium in various valence states in the lower energy range where in most cases, several isolated absorption bands can be discerned. The method used was based on our interpretation of trivalent actinide and lanthanide spectra, and the generalized model referred to earlier in the discussion of free-ion spectra. 

The free energies of formation for the actinide compounds above are given by the following table ... 

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