Infrared light source

Beyond the complexities of the dispersive element, the equipment requirements of infrared instrumentation are quite simple. The optical path is normally under a purge of dry nitrogen at atmospheric pressure thus, no complicated vacuum pumps, chambers, or seals are needed. The infrared light source can be cooled by water. No high-voltage connections are required. A variety of detectors are avail-... 

Short- and long-term drift in the spectral output can be caused by several factors drift in the output of the infrared light source or of the electronics, aging of the beam splitter, and changes in the levels of contaminants (water, CO2, etc.) in the optical path. These problems are normally eliminated by rapid, routine calibration procedures. 

A Globar is a SiC infrared light source A rod of diameter 5 to 10 mm and length 20 to 50 mm, when heated to between 1000°C and 1700°C, emits infrared radiation with wavelengths between 4 and 15 /tm (overall wave-number range 6000 to 100 cm-1). 

Fig. 7.1. Layout of the infrared spectrometer showing the Michelson Interferometer Optical System. An FTIR spectrometer s optical system requires two mirrors, an infrared light source, an infrared detector and a beamsplitter. The beamsplitter reflects about 50% of an incident light beam and transmits the remaining 50%. One part of this split light beam travels to a moving interferometer mirror, while the other part travels to the interferometer s stationary mirror. Both beams are reflected back to the beamsplitter where they recombine. Half of the recombined light is transmitted to the detector and half is reflected to the infrared source.

The infrared light source generates wideband radiation by heating solid materials to incandescence using electric power. There are two commonly used IR sources the Nernst glower, which is composed of mainly oxides of rare-earth elements and the Globar, which is... 

The most frequently used source of infrared light for infrared spectrometers is so called the Nemst stick. This stick is about two to four centimeters long and one to three millimeters thick, and is made from zirconium oxide with additions of yttrium oxide and oxides of other metals. This mixture of oxides has a negative temperature coefficient of electrical resistance. This means that its electrical conductivity increases with an increase in temperature. At room temperature, the Nemst stick is a non-conductor. Thus, an auxiliary heating is necessary for ignition of the Nernst stick. Even if the Nernst stick is red-hot, it can be heated further by electricity. The normal operating temperature of this infrared light source is approximately 1900 K. 

Ceramic infrared light sources are used in some spectrometers. A ceramic stick is heated by a metallic conductor, made from platinum or a platinum alloy, and wound around the ceramic stick. The conductor is surrounded with a sintered layer of aluminum, thorium oxide, zirconium silicate or a similar material. The heating conductors made from chrome nickel or tungsten wire are preferably suitable for short-wave spectral analysis. 

The next important part of an infrared spectrometer is the sample chamber. The sample chamber is used for placing the cuvette that contains the sample or for placing any other accessory that contains the sample. The sample chamber is installed between the infrared light source and the monochromator. 

FTIR spectroscopy is a technique based on the molecular fingerprint produced when an electromagnetic energy (infrared light) source is impinged on a material... 

Light from an infrared light source is reflected by a mirror, passed through a mechanical chopper, which pulsates it, and then passes through one of the optieal filters in the filter carousel. 

AC = acclimation cylinder, IRLS = infrared light source, IRD = infrared detector. Scale refers to the two dimensional diagrams, only. In the two dimensional diagram (lower left) the acclimation cylinder has been inverted and placed as a cover for the opening in the lid. (From Forester et al., 1983). 

Kolhed M, Haberkorn M, Pustogov V, et al. (2002) Assessment of quantum cascade lasers as mid-infrared light sources for measurement of aqueous samples. Vibrational Spectroscopy 29 283-289. 

An infrared heat lamp should be used to warm the pregnant dam while recovering from surgery (see Note 9). The infrared light source, with shield, can be bought at a hardware store, and attached on an adjustable stand, if desired. 

The principle of optical spectroscopy involves the measurement of the amount of light (radiation) that is absorbed by the sample when the radiation interacts with the sample. The most basic method involves the determination of the fraction of the radiation that is actually transmitted through a sample. The aspects of the measurement, and their relationship to the actual absorption of radiation are illustrated in Fig. 56. In this example, 7o is the power of the incident radiation from the infrared light source, and I is the actual amount of radiation transmitted through the sample. The fundamental relationships are provided with Fig. 56, and these form the basis of a fundamental expression that is used to correlate the analytical spectrum with the amount(s) of material(s) present in a sample. This fundamental expression is a simple rendering of the Beer-Lambert-Bouguer law, which is used in one form or another in the quantitative determination of material composition. 

Materials sciences using synchrotron infrared light sources... 

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