principle of FTIR

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principle of FTIR ..

Answer / pratima bhandarkar

The principle of FTIR is based on the fact that bonds and
groups of bonds vibrate at characteristic frequencies. A
molecule that is exposed to infrared rays absorbs infrared
energy at frequencies which are characteristic to that
molecule. In a molecule, the differences of charges in the
electric fields of its atoms produce the dipole moment of
the molecule. Molecules with a dipole moment allow infrared
photons to interact with the molecule causing excitation to
higher vibrational states. Diatomic molecules do not have a
dipole moment since the electric fields of their atoms are
equal. During FTIR analysis, a spot on the specimen is
subjected to a modulated IR beam. The specimen's
transmittance and reflectance of the infrared rays at
different frequencies is translated into an IR absorption
plot consisting of reverse peaks. The resulting FTIR
spectral pattern is then analyzed and matched with known
signatures of identified materials in the FTIR library.