Optical materials used

A modern variation on the rapid scan spectrometer, which is under development, uses a laser-generated plasma as a high intensity broad-band IR source (65). This method has been used to probe the vc—o absorption of W(CO)6. Another technique TRISP (time-resolved IR spectral photography), which involves up-conversion of IR radiation to the visible, has also been used to probe transients (66). This method has the enormous advantage that efficient phototubes and photodiodes can be used as detectors. However, it is a technically challenging procedure with limitations on the frequency range which depend on the optical material used as an up-converter. 

Besides other intriguing properties, such as inherent planar chirality, metallocenes are of interest due to their considerable Lewis basicity. Their direct or conjugative attachment to a polymer chain should enhance the electron density along the main chain and therefore lower the HOMO-LUMO band gap. In addition, organometallic compounds and metallocene-based monomers and polymers represent interesting potential nonlinear optical materials, useful for frequency doubling, modulation, and switching, for three reasons ... 

Ruthenocene derivatives have also been studied as potential second-order nonlinear optical materials. Using the [Cp Ru]+ fragment, several aromatic systems have been synthesized and studied for this goal. The [Cp Ru]+ fragment was synthesized by treating [Cp Ru(OMe)]2 with triflic acid. Various aromatic... 

Table 3.2a Summary of the properties of some of the optical materials used in transmission infrared spectroscopy ...

Every solvent has its own absorption bands in the MIR region. For this reason, the most appropriate solvent for the given situation has to be chosen from a whole selection. Unfortunately this selection does not include water and alcohols, which exhibit broad and strong bands in their MIR spectra. Moreover, many optical materials used as MIR windows for liquid cells (e. g. alkali hahdes, such as KBr) are soluble in water and alcohol. The solvents with the largest absorption free areas in the MIR are carbon tetrachloride and carbon disulfide. Both solvents are quite toxic and must be handled carefuUy. A Hst of the most common MIR solvents is... 

Table 2.1 Summary of some optical materials used in transmission infrared spectroscopy. From Stuart, B., Modern Infrared Spectroscopy, ACOL Series, Wiley, Chichester, UK, 1996. University of Greenwich, and reproduced by permission of the University of...

The optical transmittance properties of materials used in the ultraviolet through to the infrared are shown in Figure 1. A similar transmittance plot for optical materials used in the infrared is shown in Figure 2. However, optical properties are only one of the factors to be considered, particularly in the... 

Figure 3 Reflectance characteristics of optical materials used for mirrors. (Adapted from the Oriel catalogue (1993), volume 2.)...

E. Fiber Optic Materials (Useful Working Ranges). 35... 

Fiber Optic Materials (Useful Wavelength and Frequency Regions Are Given)... 

Cells for holding samples, or windows within the spectrometer must be made of infrared transmitting material. Table 2.1 lists approximate low wavenumber transmission limits for some optical materials used in infrared spectroscopy. All the materials listed transmit in the mid-IR above the transmission limit except for polyethylene, which is used below 600 cm" only, as it has absorption bands at higher frequencies. The transmission limits are not sharply defined and depend somewhat on the thickness of the material used. For example, a typical cell for liquid samples which is made of NaCl... 

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