Raman Spectroscopy Flashcards
What is Raman Spectroscopy?
Raman Spectroscpry involes the scattering light by molecules.
Scattering is the collision between a molecule and a photon of light in which enegry and momentum are transferred between the two collision partners.
Raman Spectroscopy is a vibrational technquie which gives infomation about bond vibrations similar to infrared.
Basic Theory
Ground state atoms are excitcted to virtual states. Virtual states exist though quantum mechanical probabilities.
Rayleigh scattering has the same freqneyc as incidnet light.
Stokes line
When the energ of the scattered radiation is less than the indicident radiation.
Anti-Stokes line
when the energy of the scattered ration is more then the incident radation
Resonance Raman
If a photon enegry used approaches the energy of an electronic absorption peak the virtual state becomes a real state.
Surface-Enhanced Raman Spectroscopy
Molecules adsorbed to certain surfaces can experience enhancement when comparared to the same molecule in solution.
Surfaces are usally of metals sliver, gold, and copper.
Surface enehancement combined with resonance raman can increase the detection limit
Selection Rule
It requires a change in polarizability for a molecule to be Raman active.
Raman is a complimentary technique to infrared spectroscopy.
Raman Spectroscopy Source
The source is always a laser since it has an high intesnsity and we are dealing with an exetremely low % of scattered light. and it is at a 90 degree angle from the source
Advantages and Applications of Raman Spectroscopy
Water is not Raman active, so samples in water can be analyzed.
Raman spectroscory has been applied widely for the study of biological systems.
Vibrational enegry of metal-ligand bonds can be studyed with Raman spectoscopy.
The laser beam can be used as soruce can be prescelsy focuse
Disadvantages of Raman Spectroscopy
Weak signal
interference from fluoresnece
