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intensity of raman band

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Adeena Qadeer

This document discusses Raman spectroscopy measurements of intensity and depolarization ratio. It explains that Raman spectroscopy measures molecular vibrations when light excites a sample's molecules. The Raman scattered light has parallel and perpendicular components relative to the incident light polarization. The depolarization ratio is the intensity ratio between the perpendicular and parallel components, indicating whether a vibration is symmetric. Factors like molecular symmetry and normal vibrational modes affect this ratio. A ratio below 0.75 indicates a totally symmetric vibration while 0.75 represents a non-symmetric vibration. The depolarization ratio helps interpret vibrations observed in Raman signals.

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Intensity of Raman band and Raman Depolarization Ratio Ghada Bint E Sajid M.Sc final
Why we use raman spectroscopy? Use to determine molecular motion especially the vibrational one
What exactly is being measured? When light hits a sample,it is excited and is force to vibrate and move.It is these vibrations which we are measuring.
. The Raman scattered light consists of the parallel component and the perpendicular component
Perpendicular component Some fraction of the Raman scattered light has a polarization direction that is perpendicular to that of the incident light. This component is called the perpendicular component.
Parallel component The component of the Raman scattered light whose polarization direction is parallel to that of the incident light is called the parallel component
. .
. Polarizibility Ease of distortion of a bond Polarization Property of beam of radiation and describes the plane in which the radiation vibrates
Depolarization ratio Intensity ratio between the perpendicular component and the parallel component of the Raman scattered light.
. For completely plane polarized light,intensity of perpendicular component is equal to zero and hence the degree of depolarization is also zero.
. for completely unpolarized (i.e. ordinary) light,intensity of parallel and perpendicular component is equal and depolarization ratio is equal to 1
. Experimently,the depolarization ratio may be obtained by inserting a polarizer between a sample and the monochromator
Factors Symmetry of the molecule and Normal vibrational mode, in other words, the point group of the molecule
. Depolarization ratio of a totally symmetric vibrational mode is less than 0.75, and that of the other modes equals 0.75.
Polzaried band A Raman band whose depolarization ratio is less than 0.75.vibration is totally symmetric.
Depolarized band A band with a 0.75 depolarization ratio is called a depolarized band.vibration is not symmetric.
. The depolarization ratio can be useful in interpreting the actual vibration responsible for a raman signal.
Intensity of raman band The Raman scattering intensity is mainly affected by the: Light source intensity (directly proportional) Wavelength of the source (l-4dependency) Concentration of the sample or number of molecules (directly proportional) Scattering properties of the sample (sample specific)
Refrences Charly D. Allemand, "Depolarization Ratio Measurements in Raman Spectrometry", Applied Spectroscopy 24(3), 1970, pp. 348353 Jump up ^ D. A. Long (Apr 8, 1953). "Intensities in Raman Spectra. I. A Bond Polarizability Theory". Proceedings of the Royal Society of London. Series A C N Banwell Wikipedia,the free encyclopedia
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intensity of raman band

  • 1. Intensity of Raman band and Raman Depolarization Ratio Ghada Bint E Sajid M.Sc final
  • 2. Why we use raman spectroscopy? Use to determine molecular motion especially the vibrational one
  • 3. What exactly is being measured? When light hits a sample,it is excited and is force to vibrate and move.It is these vibrations which we are measuring.
  • 4. . The Raman scattered light consists of the parallel component and the perpendicular component
  • 5. Perpendicular component Some fraction of the Raman scattered light has a polarization direction that is perpendicular to that of the incident light. This component is called the perpendicular component.
  • 6. Parallel component The component of the Raman scattered light whose polarization direction is parallel to that of the incident light is called the parallel component
  • 7. . .
  • 8. . Polarizibility Ease of distortion of a bond Polarization Property of beam of radiation and describes the plane in which the radiation vibrates
  • 9. Depolarization ratio Intensity ratio between the perpendicular component and the parallel component of the Raman scattered light.
  • 10. . For completely plane polarized light,intensity of perpendicular component is equal to zero and hence the degree of depolarization is also zero.
  • 11. . for completely unpolarized (i.e. ordinary) light,intensity of parallel and perpendicular component is equal and depolarization ratio is equal to 1
  • 12. . Experimently,the depolarization ratio may be obtained by inserting a polarizer between a sample and the monochromator
  • 13. Factors Symmetry of the molecule and Normal vibrational mode, in other words, the point group of the molecule
  • 14. . Depolarization ratio of a totally symmetric vibrational mode is less than 0.75, and that of the other modes equals 0.75.
  • 15. Polzaried band A Raman band whose depolarization ratio is less than 0.75.vibration is totally symmetric.
  • 16. Depolarized band A band with a 0.75 depolarization ratio is called a depolarized band.vibration is not symmetric.
  • 17. . The depolarization ratio can be useful in interpreting the actual vibration responsible for a raman signal.
  • 18. Intensity of raman band The Raman scattering intensity is mainly affected by the: Light source intensity (directly proportional) Wavelength of the source (l-4dependency) Concentration of the sample or number of molecules (directly proportional) Scattering properties of the sample (sample specific)
  • 19. Refrences Charly D. Allemand, "Depolarization Ratio Measurements in Raman Spectrometry", Applied Spectroscopy 24(3), 1970, pp. 348353 Jump up ^ D. A. Long (Apr 8, 1953). "Intensities in Raman Spectra. I. A Bond Polarizability Theory". Proceedings of the Royal Society of London. Series A C N Banwell Wikipedia,the free encyclopedia