What is the principle of FTIR?

Answer 1

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.

Answer 2

The principle of Fourier-transform infrared spectroscopy (FTIR) involves measuring the absorption of infrared radiation by a sample as a function of wavelength. This absorption produces a unique fingerprint spectrum that can be used to identify and analyze the chemical composition of the sample. FTIR spectroscopy operates by interfering the infrared radiation with itself in the frequency domain using a Michelson interferometer, allowing for rapid and sensitive measurements.