Spectroscopy and electromagnetic waves

Polarisability of Matter

Electronic, Vibrational, and Rotational States of Molecules

Harmonic Oscillator Anharmonic Oscillator

Rotational states of a vibrational state

Gas phase IR spectrum with resolved rotational states

Stokes’ linesAnti-Stokes’ lines In Raman spectroscopy, a sample is exposed to a monochromatic light beam of high intensity and of an energy that does not cause absorption/fluorescence. RAMAN Spectroscopy

Stokes’ linesAnti-Stokes’ lines momentum 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 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. Rayleigh scattering

cyclohexene IR Raman

Change in Dipole Moment and Polarizability