Identification of Natural Tourmaline and Similar Gems by Diffuse Reflection Fourier Transform Middle Infrared Spectrum

By using the infrared reflection spectrum analysis technique, natural tourmaline and imitation tourmaline, similar tourmalines were investigated. The results show that the main absorption peaks of natural tourmaline are seven peaks at 1314cm-1, 1118cm-1, 1039cm-1, 999cm-1, 601cm-1, 513cm-1, 454 cm-1. The main absorption peaks of composite tourmaline and imitation tourmaline are different from natural tourmaline. The results are useful for identifying them.

Contribution of Spectrometric Methods to the Study of the Constituents of Chromating Layers

The amorphous constituents of a chromating layer may be defined by the simultaneous use of diffuse reflection spectrometry in the ultraviolet and visible, and of Fourier transform infrared spectrometry. The PO4 group is characterized in the infrared reflection spectrum by bands located near 1070, 1030, and 900 cm−1 for chromium phosphate. The CrO4 group induces bands at 960, 860, and 820 cm−1 for zinc chromate and at about 980, 950, and 860 cm−1 for chromium chromates. The ligandmetal charge transfer bands (LMCT) characteristic of the chromates are situated in the region 3.35 to 4.20 eV. The study of the thermal behavior of chromium phosphate CrPO4 and zinc chromate ZnCrO4 shows that these compounds are stable up to 300°C. Complex chromates of Cr(III) may be observed in the range 150 to 300°C. These analytical data show the contribution of these methods which, used in the reflection mode, are demonstrably the best suited to the analysis of chromating layers on coated steel, of which the primary constituents are chromium phosphate and complex Cr(III) chromates. These results allow the interpretation of the thermal behavior of chromating layers.

Infrared and Raman spectra of liquid and crystalline silicon tetrafluoride

The Raman and infrared spectra of liquid and crystalline SiF4 have been recorded. The assignment of some of the Raman bands of the crystal to longitudinal modes has been confirmed by the infrared reflection spectrum. These indicate that the crystal structure is not centrosymmetric. In other respects the spectra are also more complicated than is expected on the basis of the previously reported Td3 structure. Possible explanations are discussed.