What is Raman spectroscopy: Definition and 39 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. Nijiro

    I Two-photon Stimulated Raman Transitions

    Hello everyone! I don't know much about quantum physics. I'm an amator, but I want to expand and deepen my knowledge in quantum. So, I decided on the Quantum Gravity Gradiometer to be the subject of my supervised personal initiative work. But I'm currently stuck with many things among which are...
  2. tanaygupta2000

    Raman Spectroscopy: Understanding Stokes and Anti-Stokes Lines

    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. 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?
  5. D

    I Can Raman spectroscopy identify every substance?

    Can raman spectroscopy identify any substance or are there certain Substances raman spectroscopy cannot identify?
  6. 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...
  7. 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...
  8. 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...
  9. R

    I What Causes Huge Raman Shifts in Water?

    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...
  10. 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...
  11. 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...
  12. 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...
  13. 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...
  14. 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?
  15. 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...
  16. 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...
  17. K

    Maximizing Vibrational State in Raman Spectroscopy: Techniques and Pricing

    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...
  18. H

    The axes in Raman spectroscopy

    What are the axes(horizontal & vertical axes) in a Raman spectrum?
  19. Q

    IR and Raman Spectroscopy With Vibrational Modes

    Homework Statement The question states to identify which graph is associated with which molecule, which are CF4 and CF2Cl2. The graphs are measurements of infrared spectra, one has one peak while the other has two. It then asks to determine which symmetry labels are associated with each peak...
  20. S

    Polarized Raman Spectroscopy: Understanding the Magic Angle

    Dear friends I have a question regarding to polarized Raman spectroscopy. When we are talking about parallel and perpendicular electric field of the laser, is the magic angle 90° or 54.7°? I'd be grateful if you could answer me as soon as possible. Best wishes Kasra
  21. W

    Resonance raman spectroscopy for analysing metallobiosite

    Homework Statement The question relates to carbonic anhydrase with Zinc at the biosite. (1ca2 on protein data bank). Q: Why can you not study the water bound to the zinc when the molecule is in an aqueous solution? Homework Equations n/a The Attempt at a Solution I've had a...
  22. B

    Raman spectroscopy help (simple)

    Homework Statement The Raman spectrum of ethene, obtained using 488.0nm radiation from a laser, shows an intense line at 540.0nm. Calculate the wavenumber for this vibration I know that you get stokes, anti-stokes and rayleigh scattering. Not sure how to calculate the wavenumber though ...
  23. B

    What Is the Real Mechanism Behind Raman Spectroscopy?

    Hello, I am currently in an analytical chemistry course where I am required to write a report on Raman Spectroscopy. The typical description of Raman Spectroscopy is the excitation of an electron to a "virtual" state, whereupon it can relax to a non zero vibrational level in its ground...
  24. L

    Raman spectroscopy: data analysis: convolution

    hey guys, i hope you can help. my task is to analyse data of raman spectroscopy. therefor i have to deconvolute it. that means the data must have been convoluted somewhere. is it true that the raw data which i receive is convoluted already? or is it common to convolute the data "active"...
  25. W

    Fluorescence and Raman spectroscopy

    I'm currently working on a lab that is exploring the Raman effect. One of the suggested exercises was to record the raman spectrum (from a mercury lamp through CCl4) around the rayleigh peaks at 435.8 nm and 404.7 nm. For the former, my results were fairly consistent with what I expected in that...
  26. M

    Raman Spectroscopy: Understanding Intensity & Wave Number Peaks

    Tell me what do the peaks in the graph show which is b/w Intensity and wave number in raman spectroscopy ? Are the peaks due to transition from a grnd state to an exicted state or vice versa , low energy are stokes and high energy are the anti stokes one
  27. I

    Density of states and Raman spectroscopy

    Hello everyone Lately I am taking some problem with my thesys, I am not an expert in theoretical physics but not bad as experimetal. I want to calculate the contribution of the w(q) away from zone O ob Brillouin to fit my experimental data to the theory and to know if the quantum theory work...
  28. P

    Raman Spectroscopy Exposure Time

    When you are setting up a spectral acquisition with a raman microscope, what does the exposure time mean? I would expect this to mean the amount of time the sample is exposed to the laser, but it doesn't seem like that can be true if it takes around 20 minutes to acquire the spectrum with a 2...
  29. C

    Protein Dynamics By Raman Spectroscopy

    Can one monitor dynamics of a specific protein domain (helix, strand etc) by Raman Sp? If one labels a specific residue with an isotope, like in NMR, can one use that to monitor the dynamics of the region that encompasses this residue?
  30. mccoy1

    Discover the Best Book on Raman Spectroscopy - Expert Recommendations

    Please can anyone suggest a good book on raman spectroscopy. cheers.
  31. S

    Raman Spectroscopy: Stokes and Anti-Stokes Wavelengths

    Hi, For someone my question could be very simple but I couldn't find a well explain paper that explain this to me. In a Raman spectrometer the stokes and anti-stokes wavelength will always be grater than the laser wavelength used?. I have this confusion because I saw that Raman...
  32. C

    Raman Spectroscopy graph question

    What are some simple graphs that can be created (in Matlab) relating to Raman Spectroscopy or just basic equations that can somehow be related to it? So far all I've done is graph E=E_0 cos (wt + 1/2 αt^2). And any suggestions of things I should read up on about the topic and understand...
  33. N

    Raman spectroscopy amide I processing

    Hello Group! I'm working on analyzing Raman spectra of proteins. I'm particularly interested in learning more about the signal processing of the amide I band. If anyone has any experience with Peakfit program or Origin, Savitsky-Golay smoothing, or amide I deconvolution for secondary...
  34. C

    Raman Spectroscopy, A Few Questions

    Using a PMT/Monochromator, we have Surface Enchanced Raman Vials we are using to analyze samples. One thing I am trying to figure out: The so called finger print region is 500-3000 wavenumbers after the wavelength of the laser you are using. In our case, we are currently using a 200mW 532nm...
  35. C

    Raman Spectroscopy: Freshman Physics Major Summer Research

    I'm a freshman physics major and I'm doing summer research on Raman Spectroscopy. I've read up on it a bit but I was wondering if there are any resources that would help me better understand or at least get a general idea of what this is.
  36. E

    Why is my protein Raman spectrum changing dramatically with each measurement?

    Raman spectroscopy of protein please help Hey any Raman experts out there? Im doing Raman spectroscopy of a protein called c-reactive protein (in aquous solution) using 532nm 10mW and the protein placed in a nmr tube. I can nicely get a spectrum of benzene and cyclohexane, but when I am doing...
  37. N

    Why does signal yield increase with shorter wavelength in Raman spectroscopy?

    I read in a journal article that in raman spectroscopy "it is well known that signal yield increases with shorter wavelength". Can anyone please explain why? I would've thought longer wavelengths = shorter frequencies = higher susceptibilities?
  38. P

    Raman spectroscopy is Single molecule identification

    Raman spectroscopy is "Single molecule identification" Hi , I heard that the speciality of Raman spectroscopy is "Single molecule identification", it'd be really great if somebody can tell me HOW! because its surely going to be a question in my exam! Thanks in advance.
  39. P

    Raman Spectroscopy: Unique Features & Benefits

    raman spectroscopy! Hi, can anybody please tell what is the speciality of Raman spectroscopy and how it differs from other techniques?? does it have any uniqueness? more info is welcomed! thanks in advance.