Spectroscopy and Raman Scattering Exam Notes

Exam Questions Overview
  • The content includes exam questions from a workshop at Kingston University London, focusing on spectroscopy and Raman scattering.
Key Topics

  • Raman Scattering vs. Rayleigh Scattering

    • Raman Scattering:

    • Involves inelastic scattering of photons, resulting in a shift in wavelength.

    • Provides information about vibrational modes of molecules.

    • Can be particularly useful for identifying molecular structures.

    • Rayleigh Scattering:

    • Involves elastic scattering where the wavelength does not change.

    • Predominantly responsible for the blue color of the sky as shorter wavelengths are scattered more.

    • Does not provide detailed molecular information.

Exam Question Example: June 2020
  • Question 10
    1. (a) Explain a relevant difference between Raman scattering and Rayleigh scattering. (5 marks)
    2. (b) Explain the difference between transmission of light and scattering of light in spectroscopy, giving an example of a technique that requires light transmission for analytical information. (5 marks)
    3. (c) Desirable properties of the Raman excitation source in a Raman spectrometer vs. excitation sources in fluorescence, considering their positions relevant to the detector. (10 marks)
Spectroscopic Techniques

  • Light Transmission vs. Scattering

    • Transmission of Light:

    • Light passing through a sample, with absorption or transmission studied.

    • Example technique: UV-Vis spectroscopy.

    • Scattering of Light:

    • Light interacting with particles, changing direction and/or energy.

Raman Spectroscopy
  • Raman Spectrometer Excitation Source Properties:
    • High intensity and monochromatic light.
    • Compatibility with the sample's characteristics.
    • Differences with fluorescence sources (e.g., wavelength selection, interaction with the detector).
Molecular Analysis with Spectroscopy
  • Example Question: May 2023
    • Consideration of S-Ketamine and R-Ketamine in a Mixture
    1. (a) Can their fluorescence distinguish between them? (5 marks)
    2. (b) Can their Raman spectra distinguish between them? (5 marks)
Instrumentation in Spectroscopy
  • Question about Instrument Verification
    • Analyzing a given instrument (e.g., as shown in Figure 5) to determine if it is a Raman spectrophotometer, focusing on its components such as:
    • Concave diffraction grating
    • Exit and entrance slits
    • Detector arrangement (Detectors 1 and 2, mirrors, lenses)
Laboratory Experience
  • MicroRaman Lab Visit
    • Hands-on exposure to microRaman technology, providing practical knowledge of instruments and techniques used in spectroscopy.