Spectra of actinides

Absorption and Fluorescence Spectra. The absorption spectra of actinide and lanthanide ions in aqueous solution and in crystalline form contain narrow bands in the visible, near-ultraviolet, and near-infrared regions of the spectmm (13,14,17,24). Much evidence indicates that these bands arise from electronic transitions within the and bf shells in which the Af and hf configurations are preserved in the upper and lower states for a particular ion. 

The electronic spectra of actinide compounds arise from three types of electronic transition ... 

In view of the magnitude of crystal-field effects it is not surprising that the spectra of actinide ions are sensitive to the latter s environment and, in contrast to the lanthanides, may change drastically from one compound to another. Unfortunately, because of the complexity of the spectra and the low symmetry of many of the complexes, spectra are not easily used as a means of deducing stereochemistry except when used as fingerprints for comparison with spectra of previously characterized compounds. However, the dependence on ligand concentration of the positions and intensities, especially of the charge-transfer bands, can profitably be used to estimate stability constants. 

The Structure and Bonding of 4/ and 5/ Series Organometallic Compounds Table 7. PMR spectra of actinide allyls... 

One has to be very cautious in interpreting, e.g., valence band spectra of actinides generally a direct comparison of valence band spectra with the density of states as derived from band ground state calculations is not appropriate. 

In this part, the photoelectron spectra of actinide elemental metals are reviewed. The organization of this part is the following ... 

Common features of the 4 f core level spectra of actinide dioxides are the symmetry of the main lines and the appearance of a satellite at about 7 eV in their high binding energy side (Fig. 30). Similar satellites have also been found for UF4, for which compound the intensity is even higher than for the dioxides. It is perhaps interesting to report some analysis of these features, on the basis of final state models. 

Fig. 30. 4 f core levels spectra of actinide dioxides measured by XPS, from Xh02 to Cf02 (from Ref. 15)... 

Photoelectron spectroscopy has long be considered as to be able to provide a photographic picture of the one-electron density of state of solids. In reality, the spectra of actinide solids (as of other narrow band solids) need very often more than this naive interpretation. In the case of 5 f response, final state effects are found to provide useful information even in the case of metals, as illustrated in this chapter. The general conclusion that the photoelectron spectroscopic response depends on many-electron excited final states as much as it depends on the initial states, when narrow bands are involved, must be emphasized. This points to the necessity both of better final state models and of band calculations giving reliable pictures of conduction bands. 

Absorption and Fluorescence Spectra. The absorption spectra of actinide and lanthanide ions in aqueous solution and in crystalline form contain narrow bands in the visible, near-ultraviolet, and near-infrared regions of the spectrum. 

Low-Temperature Absorption Spectra of Actinide Cyclopentadienides, W.T. Camall, P.R. Fields, and R.G. Pappalardo. In Progress in Coordination Chemistry. Proceedings of the 11th International Conference on Coordination Chemistry, Haifa and Jerusalem, September 1968. M. Cais (Ed.), Elsevier, Amsterdam, 1969, p. 411. 

A Systematic View of Transition Intensities in the Spectra of Actinides and Lanthanides in Condensed Phases, W.T. Camall, H. Crosswhite, and K. Rajnak. In Rare Earth Spectroscopy, B.J. Trzebiatowska, J. Legendziewicz, and W. Stick (Eds.), World Publishing Company, Singapore, 1985, pp. 267-297. 

Actinides have particular spectroscopic properties which are characterized primarily by the /- /transitions within the partially filled 5/shell and thus by a number of relatively weak, sharp absorption bands. The optical spectra of actinides are characteristic for their oxidation states, and to a lesser degree dependent upon the chemical environment of the ion. Thus spectroscopic investigation provides information on the oxidation state of an actinide element and also serves to characterize the chemical... 

Table 103 should be compared with that giving the charges associated with the lanthanide ions (p. 423). The comparison suggests that the 5f are more easily removed than the 4f electrons. However, j0rgensen (1959) concluded from the spectra of actinide ions that there are only 5f electrons outside the radon shell of the ions with a charge greater than+3. He holds there is no necessary connexion between the presence of f electrons and the dominant +3 charge number. This is very relevant in view of other... 

J. Blaise and J.-F. Wyart, Energy Levels and Atomic Spectra of Actinides, in International Tables of Selected Constants 20, CNRS, Paris, 1992. 

BLAAVYA] Blaise, J., Wyart, J. F., Selected constants Energy levels and atomic spectra of actinides, Delplanque, M., Dayet, J., Gasgnier, N., Pepin, L, Eds., International Tables of Selected Constants, No. 20, Tables Internationales des Constantes, Paris, (1992). Cited on pages 92, 527, 618. 

Ryan, J.L., 1972, Absorption spectra of actinide compounds, in MTP International Review of Science, Vol. 7, ed. K.W. Bagnall (Butterworths, London) ch. 9. 

Actinide spectra reflect the characteristic features of the 5/ orbitals which can be considered as both containing the optically active electrons and belonging to the core of filled shells. The electronic transition spectra of actinide ions in solution are dominated by the structure of the / levels and transitions within the / shell. Free-atom spectra provide more information about the interactions between the 5/ and the valence electrons. The emission spectra of the free actinide atoms have an enormous number of lines. In the uranium spectrum, about 100,000 lines have been measured, from which about 2500 lines have been assigned. 

The 5/ to 6d bands are orbitally allowed and therefore more intense than those of the / to / transitions. They are also usually broader and often observed in the ultraviolet region. The metal to ligand charge-transfer bands are also fully allowed transitions that are broad and occur commonly in the ultraviolet region. When these bands trail into the visible region, they produce the intense colors associated with many of the actinide compounds. Metal-ligand frequencies are also observed in the infrared and Raman spectra of actinide compounds. 

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