Sources of IR Radiation
The commonly employed IR source is generally an electrically heated inert solid that emits a continuum of radiation like a black body. The best sources available and commonly employed in the IR spectrophotometers are Nernst or Glower filament lamp Globar Ni-Cr (Nichrome) wire Carbon dioxide LASER.

Nernst Glower: It is a cylindrical rod made up of a mixture of zirconium, yttrium and erbium oxides (diameter of 1 _2 mm and length of about 20 mm). It is electrically connected through platinum wire and heated by the passage of an electrical current to a temperature of about 1200 to 2200 K.
Globar: It is a silicon carbide rod (diameter of 5 mm and length of about 50 mm) which is electrically heated to about 1500 K. The electrical contacts have a risk of arcing therefore water cooling of the contacts is used. The spectral output is comparable with the Nernst glower, except at short wavelengths (less than 5 m) where its output becomes larger.
Incandescent nichrome wire: It is a tightly wound coil of nichrome (Ni-Cr) wire, electrically heated to 1100 K. It produces a lower intensity of radiation than the Nernst or Globar sources, but has a longer working life.
Carbon dioxide lasers: The tuneable carbon dioxide lasers produce closely spaced
discrete lines in a limited range of IR radiation (900 to 1100 cm_1). Though the tuneable laser has limited range but it provides a much larger intensity of all the lines in the range. The laser can be tuned to any of these lines and can be used for the quantitative determination of different species like, ammonia, benzene and nitrogen dioxide etc.
In addition, some IR sources like, mercury arc and tungsten filament lamp are also used.