Fractional electron count

We can, therefore, understand the origin of the four-atom structural trend from tetrahedron rhombus -> linear chain -> square as a function of the electron count for the case of a = The presence of three-membered rings in a given geometry skews the eigenspectrum asymmetrically downwards. Hence, the close-packed structures, the tetrahedron and the rhombus, are stabilized for fractional electron occupancies less than one-half but destabilized for fractional electron counts more than one half On the other hand, the open structures, the square and the linear chain, have symmetric... 

In fact, since the bridging ligand is symmetrically located between two identical metal fragments, it is also counted symmetrically, and is counted LX/2, i.e. 1.5 electrons, for each metal. Fractional electron counts are sometimes found in bimetallic complexes in which a single electron is delocalized over two metals (see Chap. 3.1.6). Also, these are usually, two bridging LX ligands as shown below, so that the metal electron counts are no longer fractional. 

Another means for two metal centers to avoid a fractional electron count is to have an odd number of charge for the bimetallic complex in which the two metals are bridged by a single LX bridging ligand. 

Figure 1.19. Electron counting to demonstrate fractional charges on one-dimensional chains. (Reprinted with permission from ref 22)...

DFT). As a consequence of the fractional oxidation-state situation corresponding to an 18 -I- 5 valence electron count, we can expect a potential to adopt unusual metal configurations through electron-transfer-dependent intramolecular coordination, accompanied by intermolecular reactivity enhancement toward small molecule activation. 

Efficiency. Efficiency of a device can be reported in terms of an internal quantum efficiency (photons generated/electrons injected). The external quantum efficiency often reported is lower, since this counts only those photons that escape the device. Typically only a fraction of photons escape, due to refraction and waveguiding of light at the glass interface (65). The external efficiency can be increased through the use of shaped substrates (60). 

The basic approach with the axoneme-based analysis is to combine tubulin and axonema fractions and then to quench the reaction with glutaraldehyde. Samples of sufficient axoneme concentration are then added directly onto Formvar-coated sample grids for staining and electron microscopy. In some cases where the axoneme count is too low, samples may be sedimented onto grids by the method of Gould and Borisy (1977). With the methodology perfected by Borisy and Bergen (1982) samples can be taken as frequently as every 20 seconds, and the... 

In a typical EEL spectrum, the count rate Ia (area under the excitation edge after background subtraction, for element A) is a product of the incident electron current density, J0, the number of atoms Na of element A per unit area, and oa> the total ionization cross-section per atom for the excitation of the appropriate inner-shell by the incident electrons. However, to preserve good energy resolution, an aperture is placed after the specimen which limits scattering to angles less than P and hence only a fraction of the core loss signal Ia(P) is measured. Moreover, in most... 

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