Iron oxides reflectance spectra

The sunblocks zinc oxide, titanium dioxide, and iron oxide are inorganic chemicals that are not absorbed into the skin. These substances consist of opaque particles that reflect both visible and ultraviolet light. In addition, zinc oxide blocks virtually the entire UVA and UVB spectrum and thus offers overall protection. The particulate nature of these sunblocks enhances their effectiveness at reflecting sunlight. The smaller the particle size, the greater the surface area available for reflection, and the more effective the sun protection offered by the formulation. 

If over the region of interest, the scattering coefficient hardly varies with wavelength, the shapes of the remission spectrum and the absorption spectrum should be very similar. The relationship between the remission function and the reflectance spectrum is shown in Figure 7.2 left, and the Kubelka-Munk functions of the different iron oxides are illustrated in Figure 7.2, right. 

Baldia (9) describes the particulate recovered from Seip 36 as bast fibers that are reddish in color and she reports that the fibers contain a significant amount of iron as determined by EDS. Not only does the infrared spectrum of the Seip 36 particulate show cellulose, it also contains absorbances in the region of 567 cm-1 and 470 cm-1 that reflect its iron oxide content (Figure 12). Seip 5, another material noted by Baldia (9) as charred bast with red deposits displays an infrared spectrum with the bands of cellulose and bands around 590 cm-1 and 463 cm-1 that can be attributed to iron oxide. 

Both catalysts exhibit a broader iron 3d band than that of elemental iron. A large fraction of the total valence band intensity arises from these iron 3d states (cross section of Fe3d 4.5 x 10" compared to O 2p with 5 x lO " ). This reflects the presence of covalently bonded iron compounds in the mixed surface of the catalysts. The broad feature at 5.5 eV in the top spectrum arises largely from oxygen, since a similar structure with low intensity at the Fermi edge was found for iron foil exposed to 8 L oxygen at room temperature. The shoulder around 10 eV, indicative of iron oxides, was not observed in the chemisorption experiment. 

Fe[ ] = iron in complexes and metals by screening the s-elecuons). The isomeric shift decreases linearly with increasing s-electron density, i.e. an increasing s-electron density causes a shift of the resonance line toward negative velocity values. According to this the isomeric shifts of compounds with different oxidation states of the element in question fall into regions characteristic for these states, as is shown for iron in Fig. 2. The contribution of the temperature shift to the total line shift is generally small in relation to the isomeric shift. The temperature shift reflects the properties of the vibrational spectrum of the crystals. 

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