What is Raman fluorescence?
The fluorescence interference in Raman spectroscopy may result from the compound analysed or from fluorescent impurities in the sample. It is an absorption process that causes molecules to be excited to a higher electronic state, which requires high-energy photons.
What is the basic principle of Raman spectroscopy?
The Raman Spectroscopy Principle When light interacts with molecules in a gas, liquid, or solid, the vast majority of the photons are dispersed or scattered at the same energy as the incident photons. This is described as elastic scattering, or Rayleigh scattering.
What is Raman spectroscopy in simple words?
Raman Spectroscopy is a non-destructive chemical analysis technique which provides detailed information about chemical structure, phase and polymorphy, crystallinity and molecular interactions. It is based upon the interaction of light with the chemical bonds within a material.
What is Raman microscopy used for?
Raman is used for microscopic analysis Raman spectroscopy can be used for microscopic analysis, with a spatial resolution in the order of 0.5-1 µm. Such analysis is possible using a Raman microscope.
What is the difference between Raman and fluorescence?
Fluorescence occurs due to real electronic transitions. On the other hand, Raman scattering occurs as a result of virtual electronic-vibrational transitions . More generally, we can say that fluorescence is an absorption or re-emission process and Raman scattering is an inelastic scattering process.
What is the difference between scattering and fluorescence?
The fundamental difference between light scattering and fluores- cence is that fluorescence occurs from a relatively long-lived (10 8–10 9 s) excited electronic state, whereas light scattering occurs via emission of a photon from a short-lived (< 10 15 s) excited “virtual” state.
What are the types of Raman spectroscopy?
- Mass Spectrum.
- Nuclear Magnetic Resonance Spectroscopy.
- Fourier Transform Infrared Spectroscopy.
- Infrared Spectroscopy.
- Surface Enhanced Raman Spectroscopy.
Which radiation is used in Raman spectroscopy?
Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering. A source of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range is used, although X-rays can also be used.
Why is it called Raman spectroscopy?
The name “Raman spectroscopy” typically refers to vibrational Raman using laser wavelengths which are not absorbed by the sample.
What is the advantage of Raman spectroscopy?
Advantages of raman spectroscopy Direct scanning of sample can save time and chemical used for analysis. Real time diagnosis of material. No sample preparation required. Can be analyse sample multiple time without destruction and same can be used for other test analysis.
How is Raman spectroscopy different from fluorescence spectroscopy?
The main difference between Raman scattering and fluorescence is the excited state lifetime. Fluorescence excited states are longer-lived than the ‘virtual’ states associated with Raman scattering. In fluorescence, absorption of light excites an electron to a higher energy state.
How can we reduce fluorescence in Raman?
One method to avoid fluorescence emission is to select the laser excitation wavelength. For most examples, the choice of a near IR (NIR) or UV laser wavelength can avoid exciting fluorescence. In the first case, the laser photon does not have enough energy to excite molecular fluorescence.
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.
Which light is used in Raman spectroscopy?
As Raman spectroscopy requires monochromatic light as an excitation source, it is best to use single longitudinal mode (narrow bandwidth) lasers for this application. Most often used wavelengths are: 405 nm, 488 nm, 532 nm, 633 nm, 785 nm, 830 nm, 1030 nm, 1064 nm.
What are the two types of Raman scattering?
Raman scattering occurs in two ways. If the emitted radiation is of lower frequency than the incident radiation, then it is called Stokes scattering. If it is of higher frequency, then it is called anti-Stokes scattering.
Why is Raman spectroscopy used?
Raman spectroscopy can differentiate chemical structures, even if they contain the same atoms in different arrangements. Analyse your sample multiple times without damage. If you can use an optical microscope to focus onto the analysis region, you can use a Raman microscope to collect its Raman spectrum.
What is intensity of Raman line?
Resonance at Free Exciton States. The Raman intensity as a function of the incident photon energy has a Lorentzian line shape in the range of a single intermediate state. It is centered at the resonance frequency and has a width determined by the lifetime of the intermediate state.
What is the limitation of Raman spectroscopy?
Disadvatantages of Raman Spectroscopy can not be used for metals or alloys. the Raman effect is very weak. The detection needs a sensitive and highly optimized instrumentation. fluorescence of impurities or of the sample itself can hide the Raman spectrum.
What is difference between IR and Raman spectroscopy?
Raman spectroscopy depends on a change in polarizability of a molecule, whereas IR spectroscopy depends on a change in the dipole moment. Raman spectroscopy measures relative frequencies at which a sample scatters radiation, unlike IR spectroscopy which measures absolute frequencies at which a sample absorbs radiation.
What is the difference between fluorescence and Raman scattering?