Terms in this set (9)
Light scattering is of the same wavelength as the incident light - Elastic. No change or transfer if energy, relaxes to the same state.
Stokes Raman Scattering
Excitation of the molecule (lowering energy of the photon). Relaxes to a higher energy state. Transfer of energy to the molecule. Inelastic.
De-excitation of the molecule (emission of higher energy photon). Relaxes to a ground state. Energy transfer from the molecule. Inelastic.
Easier to analyse than IR, instant and portable.
It is non-destructive.
No sample prep required.
Sample can be in many different states.
No problems with water
Minimal problem testing through glass.
Why is detector at 90 degrees from laser?
So its not on same path as the laser excitation.
The ability to form instantaneous dipoles.
[In a vibrating molecule, the polarisability will oscillate].
Why are stokes lines more intense than anti-stokes?
More atoms are present in the ground state.
"mobile" delocalised pie electrons.
Rule of Mutual Exclusion
In molecules such as CO2, all modes are accounted for.
Raman modes are not visible in IR and vice versa.