Infrared radiation absorbent

Fourier-transform infrared (FTIR) spectroscopy Spectroscopy based on excitation of vibrational modes of chemical bonds in a molecule. The energy of the infrared radiation absorbed is expressed in inverse centimeters (cm ), which represents a frequency unit. For transition-metal complexes, the ligands -C N and -C=0 have characteristic absorption bands at unusually high frequencies, so that they are easily distinguished from other bonds. The position of these bonds depends on the distribution of electron density between the metal and the ligand an increase of charge density at the metal results in a shift of the bands to lower frequencies. 

Another experimental source for interaction dipoles is the measurement of pressure induced absorption . Strictly speaking this effect does not belong to the realm of Van der Waals complexes, because one measures here infrared radiation absorbed by unbound complexes. But since much can be learned about Van der Waals interactions from an interpretation of the data, we briefly review the work in this area. 

The amount of infrared radiation absorbed by the sample is proportional to the concentration of the sample and the cell path length. The Beer-Lambert law, shown in Eq. (7), illustrates the mathematical relationship ... 

Such soluble phthalocyanine compounds can be dissolved in polymer films and used as near infrared radiation absorbents of sunlight. Two interesting apphcation... 

Phthalocyanine compounds which absorb near-infrared radiation are available from Yamamoto Chemicals, a subsidiary of Mitsui Chemicals. Figure 17—4 shows the absorption spectra of a series of their products. Currently, they have 23 near infrared radiation-absorbing phthalocyanine compounds and eight absorbents composed of other materials. The absorption maxima of such phthalocyanine near-infra-red radiation absorbents are between 670 nm and 1000 nm. They may cost between one thousand and ten thousand dollars a kilogram Films of poly(vinyl chloride) and polyolefins containing phthalocyanine near-infrared absorbents are also commercially available. 

The most successful application of near infrared radiation absorbing phthalocyanine compounds is in material for recordable compact discs (CD-R). According to the international standard specification, recording materials for CD-R must have an absorption maximum around 780 nm, which wavelength permits both recording and read out. The thickness, refractive index, and extinction coefficient of the recording material are all optimized to increase the reflectance of the recording layer. 

Environmental scientists can monitor the pollutant gases in the air using an instrumental technique called infrared spectroscopy (see Chapter 18, page 241). It works quickly and accurately to monitor pollutants, including nitrogen dioxide, sulfur dioxide, carbon monoxide and carbon dioxide, as well as more than a hundred VOCs and low-level ozone. The scientists can use the characteristic wavelengths of infrared radiation absorbed by the molecules of the pollutants to identify them. They can also analyse the intensity of the absorptions to find the concentration of each pollutant present in a sample. Monitored over a period of time, the scientists provide useful information on the effectiveness of pollution control measures introduced locally and on a global level. 

Absorbance Absorbance units are used to measure the amount of infrared radiation absorbed by a sample. Absorbance is commonly used as the y-axis unit in infrared spectra. Absorbance is defined by Beer s Law and is linearly proportional to concentration. 

---