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The Science of Raman Spectrometer Design

The Raman spectrometer, such as CRAIC Technologies™ Lightblades-R™, measures the intensity of electromagnetic energy wavelength by wavelength from a sample that scatters laser light of specific wavelength.  This type of scattering is called Raman scattering and is the basis of this type of spectroscopy.

How the Raman Spectrometer Works

UV-visible-NIR spectrophotometer

Raman spectroscopy is a technique to study the vibrational characteristics of molecules.  Raman microspectroscopy is Raman spectroscopy of microscopic samples.

Monochromatic light, usually from a laser, is used to illuminate a sample.  Inelastic or Raman scattering occurs when a photon interacts with functional groups of the sample molecules and is wavelength shifted either up or down.  The majority of energy shifted photons are to a lower energy state that corresponds to the vibrational energy mode of the functional group that caused the shift in the first place. 

The Raman spectrometer is for measuring the intensity of light relative to Raman shift from the wavelength of the exciting laser, a value usually expressed in wavenumbers. Scattered light is collected from the sample and enters the device through the aperture (yellow line) and is separated into its component wavelengths by a holographic grating. The separated light is then focused onto a CCD array detector where the intensity of each wavelength is then measured by a pixel of the array. The CCD is then read-off to a computer and the result is a spectrum which displays the intensity scattered light as a function of wavenumbers from the exciting laser line.

   

In a Raman microspectrometer, such as those made by CRAIC Technologies™, the Lightblades-R™ Raman spectrometer is integrated with a specially designed microscope. This integration allows for spectroscopy of microscopic sample areas.

Raman spectrum of graphene