Table of Contents
What is meant by coherent anti Stokes Raman scattering?
Coherent anti-Stokes Raman scattering (CARS) is a nonlinear four-wave mixing process that is used to enhance the weak (spontaneous) Raman signal. In the CARS process a pump laser beam (at frequency pump) and a Stokes laser beam (at Stokes) interact, producing an anti-Stokes signal at frequency CARS = 2 pump – Stokes.
How does coherent anti-Stokes Raman spectroscopy work?
This technique involves the phenomenon of wave mixing, takes advantage of the high intensity of stimulated Raman scattering, and has the applicability of conventional Raman spectroscopy.
What do you mean by Stokes and anti-Stokes scattering?
The key difference between stokes and anti-stokes lines is that stokes lines have a longer wavelength than the wavelength of exciting radiation that is responsible for the fluorescence or Raman effect, whereas Anti-stokes lines occur in fluorescence or Raman spectra when atoms or molecules are already in an excited …
Is Raman effect coherent scattering?
Raman effect is a molecular scattering phenomenon that generates weak signal. The advanced Raman spectrum has overcome this limitation and is commonly used for detecting fresh plants containing lower analyte concentrations because of the unique Raman scattering properties in water (Kwak et al., 2017).
What are Rayleigh Stokes and anti Stokes lines?
The laser line undergoes an elastic scattering known as Rayleigh scatter and a complete spectrum has a peak at the laser line that is far more intense than the Raman scatter. Note that the anti-Stokes lines are lower in intensity and higher in energy than the Stokes lines.
What are the applications of Raman effect?
Most common applications of Raman spectroscopy
- Compound distribution in tablets.
- Blend uniformity.
- High throughput screening.
- API concentration.
- Powder content and purity.
- Raw material verification.
- Polymorphic forms.
- Crystallinity.
How does Raman scattering work?
Raman is a light scattering technique, whereby a molecule scatters incident light from a high intensity laser light source. Most of the scattered light is at the same wavelength (or color) as the laser source and does not provide useful information – this is called Rayleigh Scatter.
What is Raman scanner?
“With the Raman scanner, a hand-held device weighing less than 250g, it is now possible to scan a surface non-intrusively and in real time to detect super microscopic traces of a wide variety of molecules from pathogens and drugs to explosive chemicals,” says lead researcher Prem Bisht, a professor of physics at IIT …
What are Rayleigh Stokes and anti-Stokes lines?
Why anti-Stokes lines are more intense than Stokes lines?
Nevertheless, Stokes lines are more intense in comparison with the anti-Stokes counterparts, because the vibrational ground state is more populated than excited states.
Which of the following is ideal source for Raman experiment?
Lasers. Raman spectroscopy requires a light source such as a laser. The resolution of the spectrum relies on the bandwidth of the laser source used.