1. Raman Spectroscopy Chapter 18 CHM 411 Spring 2013 Suroviec

2. I. Introduction • Radiation when passed through a transparent medium is scattered.

3. II. Theory • Acquired by irradiating the sample with a laser of visible/Near IR radiation

4. B. Mechanism • In Raman excitation is normally carried out by radiation well away from absorption peaks to avoid fluorescence • The most likely is Rayleigh scattering • This process is NOT QUANTIZED – therefore depending on the frequency of the radiation from the laser source, the energy of the molecule can assume any virtual state between the ground state and the first electronic state

5. B. Mechanism • For a given bond the energy shifts in Raman should be identical to the energies of its IR absorption bands only if the vib modes are both IR and Raman active • IR: requires change in dipole moment • Scattering: momentary distortion of the electrons distributed around a bond, followed by reemission of the radiation as the bond returns to ground

6. C. Instrumentation

7. D. Applications • Inorganic Species • Organic species 3. Biological Applications