Spectroscopy and electromagnetic waves

1
Spectroscopy and electromagnetic waves
2
Polarisability of Matter
3
Electronic, Vibrational, and Rotational States of
Molecules
4
Anharmonic Oscillator
Harmonic Oscillator
5
Rotational states of a vibrational state
6
Gas phase IR spectrum with resolved rotational
states
7
RAMAN Spectroscopy
In Raman spectroscopy, a sample is exposed to a
monochromatic light beam of high intensity and of
an energy that does not cause absorption/fluoresce
nce.
Stokes lines
Anti-Stokes lines
8
The incoming light beam undergoes Rayleigh
scattering due to elastic collisions between the
photons and the molecules. The photons are
scattered in all directions without losing energy
and represent about 10-4 times the intensity of
the incoming light. A small percentage of the
photons (10-8 times the intensity of the incoming
light) undergo inelastic scattering and their
energy is changed by the amount of vibrational
and rotational energy they gave to or gained from
the interacting molecules.
Stokes lines
Anti-Stokes lines
momentum
Rayleigh scattering
9
cyclohexene
IR
Raman
10
Change in Dipole Moment and Polarizability