Coupled EXAFS

Table 5.2 Summary of selected analytical methods for molecular environmental geochemistry. AAS Atomic absorption spectroscopy AFM Atomic force microscopy (also known as SFM) CT Computerized tomography EDS Energy dispersive spectrometry. EELS Electron energy loss spectroscopy EM Electron microscopy EPR Electron paramagnetic resonance (also known as ESR) ESR Electron spin resonance (also known as EPR) EXAFS Extended X-ray absorption fine structure FUR Fourier transform infrared FIR-TEM Fligh-resolution transmission electron microscopy ICP-AES Inductively-coupled plasma atomic emission spectrometry ICP-MS Inductively-coupled plasma mass spectrometry. Reproduced by permission of American Geophysical Union. O Day PA (1999) Molecular environmental geochemistry. Rev Geophysics 37 249-274. Copyright 1999 American Geophysical Union...

Abbreviations CCD, charge-coupled device DEXAFS, dispersive extended X-ray absorption fine structure EXAFS, extended X-ray absorption fine structure QEXAFS, quick extended X-ray absorption fine structure TPR, temperature-programmed reaction XRD, X-ray diffraction XAFS, X-ray absorption fine structure. 

Figure 2.3 shows ESR spectra measured at 6 K for the Si02-supported V complex (2) in the presence and absence of 02. The V-monomer complex (1) showed hyperfine signals attributed to d1 configuration of a V4+=0 complex, while a broad peak was also observed on the hyperfine signals for the supported V complex (2) (Figure 2.3b). The broad signal is attributed to dipole-dipole coupling between adjacent d1 species. The ESR and FT-IR data demonstrate that another V complex is located near a V complex to form a dimeric assembly in such a way that there is no direct V—V bonding is seen in the EXAFS data.

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