Infra-red Spectroscopy

InfraRed spectroscopy is a key technique in chemical analysis: interaction of molecular dipoles’ rotations and vibrations with light in the wavenumber region 400-4000 cm^-1, allows to recognize individual functional groups so structural information is inferred for novel compounds or chemical species are identified within materials.

Fourier Transform InfraRed (FTIR) spectroscopy allows fast high-resolution acquisition of infrared spectra by exploiting the use of an interferometer to control the spectral composition of the probe beam of infrared light. The spectrum is finally obtained via inverse Fourier transform of the integrated power reaching the detector at the various optical path differences within the range of the movable interferometer arm. The technique is inherently calibrated owing to a simultaneous counting of interference fringes from a He-Ne laser shed through the interferometer.

Attenuated Total internal Reflection (ATR) is a measurement scheme which can be profitably applied to infrared spectroscopy with a great simplification of sample preparation (particularly for powder samples) and providing a surface characterization flavor to infrared spectroscopy applied to solid samples. In ATR, absorption is measured as the effect of energy subtraction to the evanescent wave extending into the material placed into close contact at the flat face of a high- refractive index prism where internal reflection occurs.

Widely used for chemical analysis, the technique can as well provide structural information for crystalline materials via measurement of optical phonons bands or provide a means to characterize shallow impurity or defect states in semiconductors.