8 - Raman Recap

Question 1

What does IR spectroscopy detect?

Answer 1

Infrared spectroscopy:
- Detects vibrations involving changes in dipole moment
- Bending

Question 2

What does Raman spectroscopy detect?

Answer 2

• Detects vibrations involving change in polarisability (ease at which a molecule’s electron cloud is disturbed)
• Symmetric stretching

Question 3

What is inelastic scattering of incident radiation, and is this seen in IR or Raman?

Answer 3

• Raman
• Energy of scattered photon ≠ energy of incident photon
  (gain or loss of energy)
  (basically, the incident photon is the laser. the laser is shone on the sample and it is then scattered. the scattered light loses/gains energy, so it is the energy of the scattered light is not equal to the energy of the initial energy put into the sample)

Question 4

What are the two types of inelastic scattering?

Answer 4

Stokes scattering - loss of energy
Anti-stokes scattering - gain of energy

Question 5

How is Raman spectroscopy used in forensics?

Answer 5

• Differentiates similar drug compounds that have similar masses
• Distinguish between body fluids (blood, semen, saliva, urine) & sources (human/animal)
• Makes body art/tattoos more visible under IR light -> same with deep/sever bruising, knife/gunshot wounds & bite marks
  Analysis of:
• hair
• paint
• ink
• explosives
• fingerprints (dusted with IR fluorescent powder, viewed under IR light)