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Raman spectroscopy is Single molecule identification

  1. Jan 29, 2006 #1
    Raman spectroscopy is "Single molecule identification"

    Hi , I heard that the speciality of Raman spectroscopy is "Single molecule identification", it'd be really great if somebody can tell me HOW! because its surely going to be a question in my exam!!
    Thanks in advance.
  2. jcsd
  3. Jan 30, 2006 #2
    Raman scattering excites low energy vibrational and rotational modes which are very target specific. I guess that's how the molecules are indentified. Someone else can probably give you more info because I only have limited knowledge on X-ray Raman scattering and it seems you're asking about Raman scattering around the laser region.
  4. Jan 30, 2006 #3
    Thnks inha,,you are right, I was looking in laser excitations.
  5. Jan 30, 2006 #4

    Claude Bile

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    What do you mean by single-molecule identification. Do you mean that a sample can be identified with only a single-molecule present?

  6. Jan 30, 2006 #5
    That is what I want to know,i think it is not same as you said but it is connected with the Surface enhanced Raman spectroscopy(I think).
    It might be identifying a given unknown sample using info about its symmetry !!!!!!
  7. Jan 30, 2006 #6


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    Yes, SMD (single molecule detection) is done using SERS. The reason you need SERS is scattering cross-section. With regular Raman scattering, the cross-section is typically of order 10^{-30] cm^2. With SERS, you get as much as about 10^{-15} cm^2 (or thereabouts).
  8. Jan 30, 2006 #7
    Ok , Thanks Gokul!
    I dodn't get what scattering cross section has to do with molecule identification, more info please! (or any web site?)
  9. Jan 31, 2006 #8
    With a small scattering cross section the experiment would take ages or fail totally as the relevant information would get buried into the background.
  10. Jan 31, 2006 #9

    Claude Bile

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    Exactly, larger scattering cross-section = more scattered photons = greater signal-to-noise ratio.

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