Raman spectrometer
500 - 4 500 cm-1 Ekspla

Coherent anti-Stokes Raman spectroscopy, also called Coherent anti- Stokes Raman scattering spectroscopy (CARS), is a form of spectroscopy used primarily in chemistry, physics and related fields. It is sensitive to the same vibrational signatures of molecules as seen in Raman spectroscopy, typically the nuclear vibrations of chemical bonds. Unlike Raman spectroscopy, CARS employs multiple photons to address the molecular vibrations, and produces a signal in which the emitted waves are coherent with one another. As a result, CARS is orders of magnitude stronger than spontaneous Raman emission. CARS is a third-order nonlinear optical process involving three laser beams: a pump beam of frequency ωpump, a Stokes beam of frequency ωStokes and a probe beam at frequency ωprobe. These beams interact with the sample and generate a coherent optical signal at the anti-Stokes frequency
ωCARS=ωpump-ωStokes+ωprobe.
The CARS signal ωCARS is resonantly enhanced when the difference between the pump ωpump and Stokes ωStokes frequencies matches a vibrational transition ωvib of the molecule.