What is Raman: Definition and 108 Discussions

Raman spectroscopy (); (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. 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. 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. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy typically yields similar yet complementary information.
Typically, a sample is illuminated with a laser beam. Electromagnetic radiation from the illuminated spot is collected with a lens and sent through a monochromator. Elastic scattered radiation at the wavelength corresponding to the laser line (Rayleigh scattering) is filtered out by either a notch filter, edge pass filter, or a band pass filter, while the rest of the collected light is dispersed onto a detector.
Spontaneous Raman scattering is typically very weak; as a result, for many years the main difficulty in collecting Raman spectra was separating the weak inelastically scattered light from the intense Rayleigh scattered laser light (referred to as "laser rejection"). Historically, Raman spectrometers used holographic gratings and multiple dispersion stages to achieve a high degree of laser rejection. In the past, photomultipliers were the detectors of choice for dispersive Raman setups, which resulted in long acquisition times. However, modern instrumentation almost universally employs notch or edge filters for laser rejection. Dispersive single-stage spectrographs (axial transmissive (AT) or Czerny–Turner (CT) monochromators) paired with CCD detectors are most common although Fourier transform (FT) spectrometers are also common for use with NIR lasers.
The name "Raman spectroscopy" typically refers to vibrational Raman using laser wavelengths which are not absorbed by the sample. There are many other variations of Raman spectroscopy including surface-enhanced Raman, resonance Raman, tip-enhanced Raman, polarized Raman, stimulated Raman, transmission Raman, spatially-offset Raman, and hyper Raman.

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  1. TthePhysicist

    A Looking for a paper describing the Raman effect

    Hi, I am looking for this paper in the study of Raman effect which has the following reference: Bir, G. L. & Pikus, G. E. 1961 Soviet Phys.-Solid State, 2, 2039. Can someone tell where I can find it? Thank you a lot for your help, TthePhysicist
  2. tanaygupta2000

    Raman spectroscopy problem

    I know that for the vibrational Raman spectrum, the energy levels are given by- E(n) = ℏω(n+1/2) - χℏω(n+1/2)^2 But I'm not getting what does it meant by the Raman lines are observed at given values of wavelengths and the fundamental vibrational frequency. I equated the E(0) with the energy...
  3. Lotto

    B What do these wavenumbers correspond to in Raman spectroscopy?

    I don't know whether it is an energy of a photon emitted by a deexciting molecule, or if it is an energy of laser's photons. Here is an example of such spectrum: For example, that value of wavenumber ##3000\, \mathrm {cm^{-1}}## is an energy of an emitted photon or a photon from laser? And that...
  4. T

    I How does a process of a Raman transition break quantum entanglement?

    I'm reading this article about quantum entanglement, and the author writes about a process in a Raman transition which would break the entanglement, and I'm interested about how it breaks the entanglement. So the passage which I'm interested in begins with: "The answer is to do an operation...
  5. ure227922

    A Question about stimulated Raman emission

    I have read a paper states that "Stimulated Raman emission relies on damping of the phonon field that is much greater than for that of the optical Stokes field". But I cannot understand this, since all the materials I read do not state this. Can anyone explain it intuitively?
  6. Salmone

    I Trying to Understand the 1928 article by Raman on Nature

    I have two doubts about the article Raman published in 1928 on Nature when he discovered Raman effect, precisely about these two sentences he wrote: 1. What does it mean the modified scattering corresponds to their fluctuations in Compton effect? I think he's talking about the radiation...
  7. Ebi Rogha

    I Rayleigh scattering VS Raman scattering

    What is the application of each of them?
  8. linqy

    How to estimate the interaction time of Raman scattering?

    Maybe we could use (1) uncertainty principle $\Delta E \Delta t = \hbar$ and get $\Delta E$ from the spetrum. Or (2) forced vibration model, then get the damping factor $\gamma$, and get $Delta t = frac{1}{\gamma}$
  9. C

    DIY Raman spectrometry?

    Hello everyone Do you think that 1. It is feasible to make your own functioning Raman spectrometer i.e. https://hackaday.io/project/1279-ramanpi-raman-spectrometer/details or https://www.physicsforums.com/threads/simple-homemade-raman-spectrometer-microscope.996397/ 2. Raman spectrometry is a...
  10. C

    Optical Simple homemade Raman spectrometer / microscope

    Hello everyone, I am attempting to make a Raman spectrometer which can double as a microscope. It uses a 532nm laser for excitation, an infinity-corrected microscope objective to collimate the light, a 200 lines/mm diffraction grating, and a confocal lens pinhole setup. A 5 megapixel camera ...
  11. sbrothy

    Apropos Raspberry PI DIY Mass Spec using Raman Scattering

    https://hackaday.io/project/1279-ramanpi-raman-spectrometer It's a pretty nifty gadget this Raspberry thingy. A computer the size of a pack of cigs. :) And a mass spectrometer... I'm not sure what such a device costs but I'm sure it pretty frigging expensive!
  12. N

    Searching for Raman Prism: Is It Real?

    I have been unable to find any material pertaining to Raman prism. Does such a thing even exist?
  13. D

    How to build a Raman detector?

    if you filter completely the relaigh scattering, could a solar panel detect a raman signal?
  14. marielescobal

    Calculation of bond length using Raman spectra

    Hi, I really need your help. Suppose I have a Raman spectra of a hydroxyapatite, how do I calculate the bond length from the spectra? I've been trying to understand the concept of Badger's rule but I really cannot understand. Please help.
  15. marielescobal

    A Raman and X-ray Photoelectron Spectroscopy

    Summary: How can I know the effects of ions on my coating using Raman and XPS? Hi! So I'm working on my thesis regarding surface morphology of Zn doped HAp coating. Now, my goal is to know the effects of Zn ions on the surface morphology of my coating using raman and xps. Jowever, I do not...
  16. D

    I What optical filter to use for Raman spectroscopy?

    Raman spectroscopy involves Illuminating a target with a laser Beam. This produces Raleigh scattering. Does The releigh scattering have the same frequency as the laser beam? So use an optical filter to block the same frequency as the laser?
  17. D

    I Can Raman spectroscopy identify every substance?

    Can raman spectroscopy identify any substance or are there certain Substances raman spectroscopy cannot identify?
  18. phzrosmary

    A Raman spectroscopy and the phonon confined in the Brillouin zone

    Hello everyone, I need some confirmation on something: As far as I understood, the raman spectroscopy measures the inelastic scattering of a photon in a medium through the absorption or the emission of a phonon in the medium. The energy and the momentum is conserved...
  19. G

    Problems with Raman Spectroscopy

    Hello, Recently I had a problem in the analysis of a raw material called Propranolol HCl, when performing Raman identification for the specific batch the obtained spectrum does not generate signal and, consequently, identity of the material. By testing other techniques like infrared and NMR, I...
  20. A

    The effect of instrumental broadening on FWHM in Raman peaks

    I would like to know how to extract the instrumental broadening effect in Raman spectrometer using solid angle of the objectives, slit width or spectrometer length. I am calculation the FWHM in Raman peaks and I would like to know the effect of instrumental broadening on Raman line width and how...
  21. fluidistic

    How are Maxwell equations satisfied in Raman scattering?

    I had learned that at the interface between 2 regions such as vacuum and a material, if there's an incident light from a region to another, the boundary conditions on the ##\vec E## and ##\vec B## fields at the interface are such that for them to hold at all times, the frequency of the incident...
  22. N

    Why Raman spectroscope doesn't use 532nm laser ?.

    Most of the commercial Raman spectrometer uses 785nm or IR laser as excitation source. Though we could use visible lasers like 532 nm in this place, which can reduce the overall cost of the device by 1. Using less power laser( since intensity of raman signal is inversly propotional to the 4th...
  23. Wrichik Basu

    I Experimental Demonstration of the Raman - Nath Effect

    I want to design an experiment to demonstrate Raman - Nath effect. Due to limited resources at my hand (my school doesn't have too much resources), my condition is somewhat like Raman, and hence I want to do the original experiment that Raman and Nath conducted in IISc Bangalore back in the...
  24. A

    Infrared spectroscopy

    I do attach a plot (pdf and Matlab) of a recorded spectrum where I do not manage to find the gas specie overlapping CO2 Could you help me? Best Alain
  25. R

    I Raman Spectroscopy question

    Hi, The following is the typical raman spectra of water. In their normal form, water molecules maintain a simple configuration: an oxygen atom is in the center and two hydrogen atoms are on the two sides symmetrically. Under ambient conditions, water molecules within liquid water give rise to...
  26. D

    Stimulated Raman in linear regime

    In the course of another thread I was lend to think about the Raman effect. I also read about the stimulated Raman effect and found that it is usually described as a third order nonlinear effect where a power of two of E is assumed to drive the nuclear vibration. I don't quite see why this is...
  27. P

    A Detection limits for Raman spectroscopy

    This may be a completely terrible question, but does someone have an idea on the detection capabilities for raman spectroscopy of a bulk sample like human tissue (hair, blood, skin, anything)? I thought it might be fun to see if it were possible to use raman to identify exposures to chemicals...
  28. luanadcf

    Controlling Raman spectrometer Horiba T64000 with labview

    Hello! How are you? I am working in the photonics Lab in my university and I was wondering if has anyone ever tried to controll the horiba spectrometer T64000 with Labview. I know there is a way to do that with activx container. I was just wondering if that works. If it does, do you have any...
  29. JeremyC

    IR and Raman spectroscopy question

    Homework Statement Sulfur hexafluoride is a centrosymmetric molecule with four infrared inactive vibrational modes: 346 cm-1 , 524 cm-1 , 643 cm-1 and 775 cm-1 The Raman spectrum of a liquid sample of SF6 (held at elevated pressures) was measured with a laser that has a centre frequency of...
  30. chobo

    I Understanding r^t & a: Seeking Clarification on Raman Spectra

    Hi all, I am studying in Raman spectra and I don't know that what's means r^t a r =1. r^t is r transpose, r^t=(x,y,z). And a is diagonalized polarizability tensor. Whats means that is equal 1? Just normailzation? Help me,and so sorry my english is too bad...
  31. Y

    A Raman Spectroscopy vs. Inelastic Electron Tunneling

    I am a first year graduate student in physics and am becoming familiarized with Raman spectroscopy to study structure of materials based off of their vibrational states. In some personal study outside of this, I came across the idea of inelastic electron tunneling spectroscopy (IETS) and was...
  32. Y

    Use Raman microscope to measure quantum yield

    We have a Renishaw inVia confocal Raman microscope. Currently I am using it to study photoluminescence. I have a very thin film with certain thickness (e.g. 60nm and 120nm). It turns out that they (60nm and 120nm) have different emission spectra. Here comes the question: Can I divide the...
  33. fricke

    Raman Spectroscopy: Why Peaks of Stokes Higher than Anti-Stokes?

    Why do peaks of Stokes higher than peaks of anti-Stokes in graph of absorbance unit against wave number?
  34. I

    Raman Spectroscopy Processing Software

    I am looking for a program that allows me to process my Raman data. What i want to do is to do integrations under certain intervalls, but also baseline corrections, noise reductions and so on. I have been coding a little bit on Matlab, but gave up once i realized I had no idea how to fix the...
  35. N

    Raman Shifts of Metals: A Guide for PhD Students

    hello, I'm a Phd student my Phd subject is about surface enhanced spectroscopy (SERS). i need a reference for the Raman Shifts of metals (ex: Gold (colloid or film), titan tungesten..). Plz if anyone can help me. thank you in advance Nicolas
  36. Y

    Emission spectrum changes with microscope objective?

    I am using a Renishaw inVia confocal microscope to study emission spectrum of molecules. The excitation wavelength of laser that I use is 532nm. However, I met with a very basic problem. When I use the same material (say plain silicon), and use different objectives (20X, 50X, 100X), then I will...
  37. M

    Why do I plot certain Raman against the wavenumber

    I am currently writing my Bachelorthesis about Raman spectroscopy. For measurement with a 785 nm Laser I plot the Intensity against the Raman shift. But for measurements involving a 532 nm, I had so select the program (Spectrasuite) so display them against the "normal" wavenumber. Why is that...
  38. T

    Raman Scattering and Laser

    Why do we need the presence of an intense radiation in Inverse Raman Effect and Multi Photon Absorption?
  39. R

    Difference between X-ray Diffraction techniques and Raman spectroscopy

    Hi everyone, I'm little bit confuse about non destructive techniques such as XRD (X-ray Diffraction) and Raman spectroscopy, I know that both techniques can determine the crystal structure of the certain materials, and also, I know that XRD is working with the principle of emission of x-ray...
  40. H

    Why is raman effect weaker than Rayleigh

    Hello! I apologise, if I put this problem into the wrong topic. I know that when the light is shined on the molecule it can get polarized. And because of that you can get Rayleigh and Raman scaterring. Also I know that only one photon over million or billion will scater as Raman. The...
  41. K

    Raman Spectroscopy

    I have read about it, and interested. Here's some questions not obvious in the references I read. For the strokes where the laser final result is higher than the ground state or more accurately described by Wikipedia "If the final vibrational state of the molecule is more energetic than the...
  42. E

    Raman Amplification: Understanding its Role in Optical Fibers

    Hello I understood what is the meaning of Raman scattering whether spontaneous or stimulated but I did not understand its importance in the optical fiber The amplification role is to compensate the loss on the fiber of the signal but how did we do it in the fiber !? Thank you
  43. M

    Polarizability if a molecule in raman scattering

    Hello. I'm reviewing background information on Raman scattering and I've noticed that the polarizability scales with v+1 for Stokes transitions and v for anti-Stokes. Why is this and what assumptions are used in the derivation? An explanation or pointing me to a good reference would be...
  44. B

    Is my material Nanocrystalline or Amorphous? (XRD and Raman)

    Hi! How can I tell, based on my Raman and X-Ray Diffraction studies, if a thin film is nanocrystalline or amorphous? The maximum thickness of my films is about 200nm, the XRay diffractograms showed nothing but the substrate (is it because of the thickness?), and my Raman spectra showed some...
  45. H

    The axes in Raman spectroscopy

    What are the axes(horizontal & vertical axes) in a Raman spectrum?
  46. Y

    Relation between RAMAN Intensity and Energy of the photon

    Hi all, What is the relation between RAMAN Intensity and Energy of the photon and/or bond stregth and/or bond energy? Is there any equation or sth explain it easily? If you can explain it in a simple way, I will appreciate. Thanks
  47. O

    Stimulated Raman Scattering Spectroscopy

    Has anyone read or seen any articles that might highlight the techniques of Stimulated Raman Scattering Spectroscopy? Or just any knowledge on the process they would be able to share? I am having a tough time getting a hold on the process and if anyone has any useful information or articles that...
  48. S

    Photon conservation in Raman amplification

    Part 1: Homework Statement Use two coupled-wave equations for the Raman amplification process depicted to the right to show that for every photon at Stokes frequency omega_s created (destroyed) one photon in the laser pump field omega_L is destroyed (created). I have the coupled-wave...
  49. P

    Trouble taking Raman spectra in solution.

    Hello everyone! I´m new to the forum and to start participating and being part of it I have the following problem and question: I began using a dispersive Raman system and I got spectra of Rhodamine B and heparin sodium (and anticoagulant and glycosaminoglycan) in solid form and the spectra...
  50. D

    Utilizing Raman Signal in Optoelectronic Device Fabrication - Expert Insights

    Hi Does anyone know how Raman signal can be used in optoelectronic device fabrication?