The Optics Laboratory
Group of Hans Hallen, Physics Department, North Carolina State University

 

Raman Spectroscopy

Green light comes in from the left. Some of the energy of one photon is absorbed by the molecule, changing its color to yellow. (That is an exaggeration, for most materials it would still look almost the same shade of green.) The purple arrow shows the change in the molecule, as the vibration amplitude (red arrow) gets larger.

 

IR Spectroscopy

Purple light comes in from the left. All the energy of one photon is absorbed by the molecule, annihilating the photon. The purple arrow shows the change in the molecule, as the vibration amplitude (red arrow) gets larger.

Apparatus for Raman

This schematic drawing of one of our Raman set-ups illustrates a typical system. Laser light is coupled into an optical fiber, which carries the light to the sample. Scattered light is collected and collimated by a lens, and passes through the notch filter before being focussed onto the entrance of the spectrometer. The light is dispersed by the grating, and is detected by the cooled CCD camera.

This Raman spectrum, of a potassium titanyl phosphate, has many vibration modes that are Raman active. Each peak corresponds to a different vibration in the material. The energy of the vibration increases to the right. Note the background on the left side of the plot. This is due to elastic (mainly Rayleigh ) scattering from defects in the crystal, and is known as the Rayleigh tail.

  •  More info is in the papers.

    NC State University | Physics | Optics Home
    Copyright ©2000-2017, Hallen Laboratory, NCSU, Raleigh, NC. www.physics.ncsu.edu/optics
    Comments or questions?
    Hans_Hallen@ncsu.edu