How will you explain Raman scattering by classical and quantum mechanical theories?
The classical theory of the Raman effect is based upon polarizability of molecules, which reflects how easy an electron cloud of a molecule can be distorted by an electric field (light). The technique is based on molecular deformations in electric field E determined by molecular polarizability α.
What is Raman scattering in physics?
Raman scattering or the Raman effect (/ˈrɑːmən/) is the inelastic scattering of photons by matter, meaning that there is both an exchange of energy and a change in the light’s direction. Rayleigh scattering usually has an intensity in the range 0.1% to 0.01% relative to that of a radiation source.
What is Raman effect what are its characteristics how quantum theory qualitatively explained Raman effect?
Raman scattering or the Raman effect is the inelastic scattering of aphoton by molecules which are excited to higher vibrational or rotational energy levels. In a gas, Raman scattering can occur with a change in energy of a molecule due to a transition to another (usually higher)energy level.
How does Raman scattering work?
Raman is a light scattering technique, whereby a molecule scatters incident light from a high intensity laser light source. However a small amount of light (typically 0.0000001%) is scattered at different wavelengths (or colors), which depend on the chemical structure of the analyte – this is called Raman Scatter.
What are Stokes and anti-Stokes lines in Raman spectrum?
Stokes lines are of longer wavelength than that of the exciting radiation responsible for the fluorescence or Raman effect. Anti-Stokes lines are found in fluorescence and in Raman spectra when the atoms or molecules of the material are already in an excited state (as when at high temperature).
Why is Raman spectroscopy regarded as a scattering phenomenon?
RAMAN SPECTROSCOPY. The Raman effect involves scattering of light by molecules of gases, liquids, or solids. If the frequency of the scattered light is higher than the incident light (shorter wavelength), the light has gained energy from the vibrational or rotational quanta. This is called anti-Stokes scattering.
What causes Raman scattering?
Raman effect takes place when light enters in a molecule and interacts with the electron density of the chemical bond causing electromagnetic field in the molecule leading to vibrational and deformation of frequency shift. The incident photon excites the electron into a virtual state.
Why does Raman scattering occur?
Raman effect, change in the wavelength of light that occurs when a light beam is deflected by molecules. On some occasions, however, the molecule takes up energy from or gives up energy to the photons, which are thereby scattered with diminished or increased energy, hence with lower or higher frequency.
What is Raman scattering used for?
Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified. Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering.
What is Raman scattering of light?
Raman scattering is an optical process where incoming excitation light interacting with a sample produces scattered light that is lessened in energy by the vibrational modes of the chemical bonds of the specimen.
Why is Raman scattering weak?
This occurs because only molecules that are vibrationally excited prior to irradiation can give rise to the anti-Stokes line. Hence, in Raman spectroscopy, only the more intense Stokes line is normally measured – Raman scattering is a relatively weak process. The number of photons Raman scattered is quite small.
What is Rayleigh’s law of scattering?
(Also called Rayleigh scattering.) According to this law, first derived in 1871 by Lord Rayleigh using simple dimensional arguments, scattering in all directions by an object is inversely proportional to the fourth power of the wavelength of the illumination.
What does Raman scattering mean?
Raman scattering or the Raman effect /ˈrɑːmən/ is the inelastic scattering of a photon by molecules which are excited to higher energy levels.
What is the difference between Rayleigh and Raman scattering?
Rayleigh scattering is a form of an elastic scattering of light or any other electromagnetic radiation whereas Raman scattering is a form of inelastic scattering of light or any other electromagnetic radiation. Therefore, the main difference between Rayleigh and Raman scattering is their elastic and inelastic nature , respectively.
Why do we use Raman spectroscopy?
Raman spectroscopy is a technique commonly used to identify molecules in the field of Chemistry by their vibrational, rotational and other low-frequency modes. It takes the help of spectroscopy, the interaction of matter with electromagnetic radiation, to show its results.
What is the importance of Raman spectroscopy?
Raman spectroscopy is used in chemistry to identify molecules and study chemical bonding and intramolecular bonds . Because vibrational frequencies are specific to a molecule’s chemical bonds and symmetry (the fingerprint region of organic molecules is in the wavenumber range 500-1500 cm−1), Raman provides a fingerprint to identify molecules.