Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 202

The absorption, reflection, or emission of light in the near UV to near IR (~250–3000 nm) is also a source of structural information. In UV/Vis spectroscopy, one thus measures the absorption of light by a material caused by a number of factors: electronic transitions of transition metal d electrons, intervalence charge transfer (IVCT) and anion–cation charge transfer, electronic transitions between the conduction and valence bands, vibrational overtones, electronic transitions between f‐orbitals, defects, and electron holes [26]. The technique is primarily used to investigate the causes of color in glasses through the oxidation and coordination environment of coloring transition metal elements such as Ni within glasses (Chapter 6.2). In general, specific absorption bands are observed that are characteristic of the transition metal, its oxidation state, and coordination. The samples are usually polished glass chips (mm) or slabs (mm–cm). In addition, sample thickness may need to be adjusted for specific experimental conditions.

Figure 12 The different oxygen species identified from the XPS O 1s spectrum of a lead silicate glass. BO peak is constrained to a linewidth of 1.22 eV and fitted with two peaks in the NBO envelope, one due to NBOs and the other to the presence of free oxygen. Glass made and spectrum obtained by Ryan Sawyer, University Western Ontario.