Chapter 12: Raman Spectroscopy

Question 1

What is the source for excitation in RAMAN?

Answer 1

Lasers

Question 1

What does LASER stand for?

Answer 1

Light amplification by stimulated emission of radiation

Question 2

What can RAMAN probe?

Answer 2

Liquids, solids, and gasses.

Question 3

What is Rayleigh scattering?

Answer 3

It’s an elastic process where energy is released at the same frequency as the incident of radiation.

Question 4

What is RAMAN scattering?

Answer 4

It’s an inelastic process where the energy is released at either a lower or higher frequency than the incident of radiation.

Question 5

Stoke Shifted Peaks

Answer 5

Low intensity, longer wavelength (-)

Question 6

Anit-stoke Shifted Peaks

Answer 6

Low intensity, shorter wavelength (+)

Question 7

What are some advantages of RAMAN over IR?

Answer 7

-Non-destructive to samples
-Higher temperature studies possible
-Can easily examine low wavenumber regions (100 cm^-1)
-Better microscopy; using light so can focus more tightly
-Easy sample prep (can literally use water as solvent). Can also probe through glass/plastic containers.

Question 8

Why would you want to use a short wavelength? Why would you want to use a long wavelength?

Answer 8

-We would want to use a short wavelength because scattering depends on 4th power of frequency.
However…
-We would want long wavelengths to minimize the chance of inducing fluorescence.

Question 9

What type of lasers are used in RAMAN?

Answer 9

-Argon ion
-Frequency doubled argon ion
-diode
-Nd:YAG
-Neon-copper laser

Question 10

What are lasers characterized by?

Answer 10

1) Pump source
2) Lasing Medium
3) Cavity/Resonator 2 mirrors, 1 leaky