Globar, infrared source

The Wien displacement law for blackbody radiators states that the product of temperature in kelvin and the wavelength of maximum emission is a constant k k - T - Calculate the wavelength of maximum emission for a Globar infrared source operated at 18(X) K. Use the data In Figure 6-22 for the Nernst glower for the evaluation of the constant. 

Figure 3. Broadband spectrum of a conventional 2000 Globar IR source (short dashed line), and the spectrum of the NSLS synchrotron source (solid line) limited by an experimental throughput of 4.4><1 O 4 mm2sr. This is the etendue for a 1 pm by 1 pm sample measured with an infrared microscope. The measured, background limited Noise Equivalent Power (NEP) of a Mercury Cadmium Telluride (MCT) (long dashed line) detector is shown. This detector is operated at liquid nitrogen temperatures.

The most common mid-infrared source used in FT-IR spectrometers is a resis-tively heated silicon carbide rod, commercially known as a Globar. The typical... 

The advantages of using infrared lasers are that (i) their intensities are much higher than those of a conventional infrared source such as a globar, and (ii) they are better suited for high-resolution measurements. However, they have a drawback that the tunable wavenumber region is generally narrow. 

The main sources of infrared radiation used in spectrophotometers are (1) a nichrome wire wound on a ceramic support, (2) the Nernst glower, which is a filament containing zirconium, thorium and cerium oxides held together by a binder, (3) the Globar, a bonded silicon carbide rod. These are heated electrically to temperatures within the range 1200- 2000 °C when they will glow and produce the infrared radiation approximating to that of a black body. 

Fourier transform infrared (FTIR) spectroscopy has been extensively developed over the past decade and provides a number of advantages. The main part of FTIR spectrophotometer is the Michelson interferometer. Radiation containing all IR wavelengths (e.g., 4000-400 cm 1) is emitted by source of infrared radiation (Globar) and is split into two beams. One beam is of fixed length, and the other is of variable length (movable mirror). 

Evacuation is not necessary in this region and sources are much less of a problem than they are in the far-infrared. A heated black body emits strongly in the near- and mid-infrared and a Nemst filament, consisting of a mixture of rare earth oxides, or a silicon carbide Globar, emulate a black body quite well. 

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). 

The continuum sources for IR radiation are normally heated inert solids. A Globar source is a silicon carbide rod infrared radiation is emitted when the Globar is heated to about 1500°C by the passage of electricity. Table 25-1 gives the wavelength range of these sources. 

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... 

Sources of infrared emission have included the Globar, which is constructed of silicon carbide. There is also the Nernst filament, which is a mixture of oxides of zirconium, yttrium and erbium. However, a Nernst filament only conducts electricity- at elevated temperatures. ... 

As with dispersive instmments, FT-IR spectrometers use a Nernst or Globar source, for the mid-infrared region. If the far-infrared region is to be examined, then a high-pressure mercury arc lamp can be used. For the near-infrared region, tungsten lamps are used as sources. 

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