XANES spectra coordination

Figure 2. Effect of coordination geometry on V XANES spectrum V naphthenate (----), (---). ...

Thus we can directly deduce the XANES spectrum of the product state from the measured transient signal and the reactant state XAS, if we knowXO Alternatively, we can derive fit), if we know the exact shape of the product state XAS, P(E,t). The details are given in ref. 14. The resulting spectrum for the [Ruln(bpy )(bpy)2]2+ species is shown in Fig. 4a (trace P). It contains an energetic shift of all features by 1.2 eV, together with the photoinduced appearance of the A feature, as expected. The A-B splitting (4 eV) and the B /A intensity ratio (ca. 2.3) is indeed close to the values observed for [Ru"(NH3)6]3+ complex [18,20], which has the same valency and a similar coordination symmetry (Oh versus D3) as the bipyridine complex. 

At energies above the edge, core electrons are excited to continuum states, and the spectrum becomes dominated by scattering phenomena, similarly as in EXAFS. Flence, in a qualitative sense, the shape of the XANES spectrum depends straightforwardly on the states that are available to the excited electron. These depend on several factors, such as the coordination of the atom (octahedral, tetrahedral, etc.), its mode of bonding, oxidation state, the density of states in the electron band, etc., which give XANES its great chemical sensitivity. 

Fig. n. X -ray absorption spectra of K3Fe(CN)j and K FefCN) (panel b) and their derivative (panel c). In panel a the calculated XANES of Fe(CN)g clusters are plotted. The solid line is obtained using the coordinates of diffraction experiments for the KjFefCN) crystal. The dasshed line is obtained using the coordinates of diffraction experiments for the K FefCN) crystal. The dashed-dotted line Ls the XANES spectrum using the coordinates of an alternative structure suggested by diffraction experiments... 

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