IR absorption edge

The complexity of the situation is depicted in Fig. 16.7, where the reflectance of KBr at 10 K is plotted as a function of incident photon energy over a wide range from the IR to the UV. The salient features are an IR absorption edge at 0.03 eV, an absorption peak at about 2 eV, and a number of absorption peaks in the UV part of the spectrum around 7 eV. 

It is worth noting here that the information embedded in this graph, between the IR absorption edge and the UV spectrum, is the same information that appears in Fig. 14.13/) over the same range. 

Infrared Absorption. Attempts to determine the nature of carbon-hydrogen bonding by means of a Beckman IR-5 infrared spectrophotometer were not successful, probably because of the near opacity of the anthraxolite and excessive scatter caused by inadequate grinding. Highly graphitized carbons are commonly opaque to Infrared radiation because the absorption edge of electronic excitation occurs in the infrared range. 

No mixed valence transitions in One or more mixed valence One or more mixed valence Absorption edge in the IR,... 

Figure 16.13 Infrared absorption edges of select ceramic crystals. Note the correlation between the IR edge and the melting points of the solids.

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