5f structure

As the result of increasing sophistication of the experiments, a large range of oxidation states of the actinide elements is known, which are summarized in table 14.4 of Katz et al. (1986) which is reproduced here. These are well understood on the basis of the actinide concept, fitting in well with the expected stability of the III oxidation state of the middle element (element 96 with the half-filled 5f structure) and the last element (element 103 with the filled 5f structure). 

The intense peak at -0.65 eV in UBeis is as yet not totally understood, but it may be related to a surface state of 5f-6d nature. It reaches a maximum intensity at Av = 104 eV, or 3 eV lower than the remaining 5f structure, consistent with our previous assumptions. 

The isolation in poor yield of 2,5,5-triphenyl-4(5f )-oxazolone (82) by reaction of benzilic acid with benzonitrile in concentrated sulfuric acid was claimed by Japp and Findlay. Cornforth, however, suggested that the reactions of this product, m.p. 136°, could be accounted for more satisfactorily by the isomeric 5(4i ) structure 83. 

Prediction of the energy level structure for Pu2+ (5f ) is of particular interest since no spectra for this valence state of Pu have been reported. On the basis of what is known of the spectra of Am2+ (26), Cf2" (27), and Es2+ (28), there appears to be evidence for a very small crystal-field splitting of the free-ion levels. Such evidence encourages use of a free-ion calculation in this particular case. The parameter values selected are indicated in Table V. Based on the systematics given by Brewer (19), the first f- d transition should occur near 11000 cm-, so the f- -f transitions at higher energies would be expected to be at least partially obscured. A... 

Fournier JM, (1985) Actinide Solids. 5f Dependence of Physical Properties. 59160 1-56 Fournier JM, Manes L (1985) Magnetic Properties of Actinide Solids. 59160 127-196 Fraga S, Valdemoro C (1968) Quantum Chemical Studies on the Submolecular Structure of the Nucleic Acids. 4 1-62 Frasinski LJ, see Codling K (1996) 85 1-26... 

Thienamycin (Fig. 5.5E) is a broad-spectrum /3-lactam antibiotic with high /3-lactamase resistance. Unfortunately, it is chemically unstable, although the TV-formimidoyl derivative, imipenem, overcomes this defect. Imipenem (Fig. 5.5E) is stable to most/3-lactamases but it readily hydrolysed by kidney dehydropeptidase and is administered with a dehydropeptidase inhibitor, cilastatin. Meropenem, which has yet to be marketed, is more stable than imipenem to this enzyme and may thus be administered without cilastatin. Its chemical structure is depicted in Fig. 5.5F. 

The physical significance of Eq. (53) is clear. At an isolated resonance the excitation and dissociation processes decouple, all memory of the two excitation pathways is lost by the time the molecule falls apart, and the associated phase vanishes. The structure described by Eq. (53) was observed in the channel phase for the dissociation of HI in the vicinity of the (isolated) 5sg resonance. The simplest model depicting this class of problems is shown schematically in Fig. 5d, corresponding to an isolated predissociation resonance. Figures 5e and 5f extend the sketches of Figs. 5c and 5d, respectively, to account qualitatively for overlapping resonances. 

All nitrogen fluorides are very reactive, often dangerous species, generally powerful oxidizers. Such compounds as NF3 (5F = +143) and N2F4 would virtually never be encountered in an organic synthesis laboratory, and no NMR data have even been reported for the latter compound. NF3 has a pyramidal structure, with F—N—F bond angles of -102°. 

Crystal Chemical Studies of the 5f Series of Elements. I. New Structure... 

Extremely high cistactic structures are obtained by catalysts systems based on 4f and 5f block elements of Periodic Table (lanthanides and actinides). Some of these catalysts systems are particularly interesting for saving energy in the polymerization process. 

Figures 5e and 5f show OCT images of two flax seeds (GMF) 5 minutes after being soaked in water. Multiple grouping of water transport channels with formation of lens-shaped water-bearing structures can be clearly distinguished.

Transverse relaxation of musculature is relatively fast compared with many other tissues. Measurements in our volunteers resulted in T2 values of approximately 40 ms, when mono-exponential fits were applied on signal intensities from images recorded with variable TE. More sophisticated approaches for relaxometry revealed a multi-exponential decay of musculature with several T2 values." Normal muscle tissue usually shows lower signal intensity than fat or free water as shown in Fig. 5c. Fatty structures inside the musculature, but also water in the intermuscular septa (Fig. 5f) appear with bright signal in T2-weighted images. 

Unlike the lanthanides, the actinides U, Np, Pu, and Am have a tendency to form linear actinyl dioxo cations with formula MeO and/or Me02. All these ions are paramagnetic except UO and they all have a non-spherical distribution of their unpaired electronic spins. Hence their electronic relaxation rates are expected to be very fast and their relaxivities, quite low. However, two ions, namely NpO and PuOl", stand out because of their unusual relaxation properties. This chapter will be essentially devoted to these ions that are both 5/. Some comments will be included later about UOi (5/°) and NpOi (5/ ). One should note here that there is some confusion in the literature about the nomenclature of the actinyl cations. The yl ending of plutonyl is often used indiscriminately for PuO and PuOl and the name neptunyl is applied to both NpO and NpOi. For instance, SciFinder Scholar" makes no difference between yl compounds in different oxidation states. Here, the names neptunyl and plutonyl designate two ions of the same 5f electronic structure but of different electric charge and... 

Table Oscillator strengths for 5f-6g fine-structure transitions in Ar II. Jfi coupling...

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