instrumental techniques applied to mineralogy and geochemistry

More documents

Recommendations

Info

X-ray Absorption Spectroscopy in Mineralogy and in the Earth and Environmental Sciences 47 FIGURE 4. Single and multiple-scattering processes in x-ray absorption. Often these features are diagnostic of coordination and are of use for geochemistry. For example, the toxic chromate anion is tetrahedral and as a result has a large absorption feature just below the absorption edge (the so-called pre-edge) that is not present in the more benign Cr(III). As a result, the presence of this feature is diagnostic for the more toxic form of chromium. It is important to note that XANES is sensitive not only to the oxidation state, but also to the bonding geometry. The symmetry of the absorbing site strongly affects the pre-edge transition and, thus, XANES is capable of discriminating species of similar formal oxidation state but different coordination. FIGURE 5. Cr K-edge XANES of Cr 3+ and Cr 6+ in octahedral and tetrahedral environments.
48 Jesús Chaboy FIGURE 6. Ti K-edge XANES spectra of reference compounds in which Ti ion shows the same oxidation state but different coordination. The more distant region of the X-ray absorption spectrum is termed the extended X- ray absorption fine structure (EXAFS) region. EXAFS spectra are best described as a series of periodic sine waves that decay in intensity as the incident energy increases from the absorption edge. These sine waves result from the interaction of the elected photoelectron with the surrounding atomic environment. As such, their amplitude and phase depend on the local structure of excited atom and, consequently, the EXAFS provides direct, local structural information about the atomic neighborhood of the element being probed. The information content consists of the identity of neighbouring atoms, their distance from the excited atom, the number of atoms in the shell, and the degree of disorder in the particular atomic shell. These distances and coordination numbers are diagnostic of a specific mineral or adsorbate-mineral interaction; consequently, the data are useful to identify and quantify major mineral phases, adsorption complexes, and crystallinity. Although the EXAFS formula (see Fig. 3) provides a complete description of the EXAFS oscillations, it is not a particularly convenient form for visualizing the information content of an EXAFS spectrum. Fourier transformation can be used to decompose a frequency-space signal into its different constituent frequencies. This is illustrated for crystalline and amorphous Germanium in Fig. 7. The Fourier transform
Page 2 and 3: SEMINARIOS DE LA SOCIEDAD ESPAÑOLA
Page 4 and 5: FOREWORD On the occasion of the Spa
Page 6 and 7: INDEX Electron back-scattered diffr
Page 8 and 9: 8 Elisabetta Mariani et al Introduc
Page 10 and 11: 10 Elisabetta Mariani et al success
Page 12 and 13: 12 Elisabetta Mariani et al number
Page 14 and 15: 14 Elisabetta Mariani et al FIGURE
Page 16 and 17: 16 Elisabetta Mariani et al FIGURE
Page 18 and 19: 18 Elisabetta Mariani et al In-situ
Page 20 and 21: TEM in Geology. Basics and applicat
Page 42 and 43: X-ray Absorption Spectroscopy in Mi
Page 56 and 57: Raman, Conventional Infrared and Sy
Page 82 and 83: 84 Clemente Recio Isotope Terminolo
Page 84 and 85: 86 Clemente Recio collector gas sou
Page 86 and 87: 88 Clemente Recio Something similar
Page 88 and 89: 90 Clemente Recio beers. Some brand
Page 90 and 91: 92 Clemente Recio The source of the
Page 92 and 93: 94 Clemente Recio By using GC-C-IRM
Page 94 and 95: 96 Clemente Recio about 25% of tota
Page 96 and 97:
98 Clemente Recio such as blood and
Page 98 and 99:
100 Clemente Recio relatively simpl
Page 100 and 101:
102 Clemente Recio following admini
Page 102 and 103:
104 Clemente Recio and high N in dr
Page 104 and 105:
106 Clemente Recio although 15 N d
Page 106 and 107:
108 Clemente Recio spectrometers th
Page 108 and 109:
110 Clemente Recio O’Brien, D.M.
Page 110 and 111:
112 Kjell Bilström time in old geo
Page 112 and 113:
114 Kjell Bilström ratios ( 204 Pb
Page 114 and 115:
116 Kjell Bilström Certain samples
Page 116 and 117:
118 Kjell Bilström Molybdenite is
Page 118 and 119:
120 Kjell Bilström analyzed with r
Page 120 and 121:
122 Kjell Bilström radiogenic sign
Page 122 and 123:
124 Kjell Bilström plants inherits
Page 124 and 125:
126 Kjell Bilström in some cases a
Page 126 and 127:
128 Kjell Bilström Besides, minera
Page 128 and 129:
130 Kjell Bilström References Bear
Page 130 and 131:
Analytical techniques applied to fl
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
show all

instrumental techniques applied to mineralogy and geochemistry

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?