Raman Spectroscopy

Learn the fundamentals of Raman spectroscopy and how you can apply this technology to your research, analytical and QA/QC activities. Find basic Raman tutorials, advanced Raman webinars on sample applications, and a helpful instrument guide to build your confidence in Raman spectral analysis.

Overview

In Raman spectroscopy, an unknown sample of material is illuminated with monochromatic (single wavelength or single frequency) laser light, which can be absorbed, transmitted, reflected, or scattered by the sample. Light scattered from the sample is due to either elastic collisions of the light with the sample's molecules (Rayleigh scatter) or inelastic collisions (Raman scatter). Whereas Rayleigh scattered light has the same frequency (wavelength) of the incident laser light, Raman scattered light returns from the sample at different frequencies corresponding to the vibrational frequencies of the bonds of the molecules in the sample.


Raman Tutorials

Here you will find video tutorials from our very own Professor, Mike Bradley.

Examine the roots of Raman Spectroscopy. Starting with energy levels, we walk through excitation, scattering and interferences.

Raman Basics

6 minutes

Go behind the scenes and discover the inner workings of Raman. Three standard Raman events are explained; Rayleigh Scatter, Stokes, and Anti-Stokes.

  • Virtual state (1:20)
  • Rayleigh scatter (1:45)
  • Stokes photon (2:10)
  • Molecule energy equation (3:10)
  • Anti-Stokes photon (3:30)

Fluorescence

6:45 minutes

Understand fluorescence and learn how to avoid it’s interference with the Raman spectrum.

  • Ground electronic state (1:00)
  • Vibrational energy states (1:45)
  • Absorption of electronic energy (2:25)
  • Fluorescence emitted photon (3:00)
  • Critical facts of fluorescence (3:50)
  • Obtain a Raman spectrum in the presence of fluorescence (5:45)

Stokes and Anti-Stokes

8:35 minutes

Learn the reasons the Stokes side of the spectrum is most commonly used. You may think it is wise to use the anti-Stoke side of the spectrum to avoid fluorescence, but you never get something for nothing and the price you pay is intensity.

  • Drawing out Stokes and Anti-Stokes (1:00)
  • Plotting the spectrum (2:00)
  • Rayleigh scatter (3:00)
  • The Boltzmann Distribution (4:25)
  • Anti-Stoke intensity (5:20)
  • Why Stoke spectroscopy is most common (7:00)

A discussion of why we offer multiple lasers and how FT-Raman helps avoid fluorescence.

Multiple Lasers

8:00 minutes

Learn how to achieve a virtual state to avoid fluorescence and obtain an accurate Raman scatter. Find the balance in a laser to avoid fluorescence while still gaining efficiency.

  • High energy lasers (1:15)
  • Fluorescence photon (2:00)
  • Obtaining a virtual state and avoiding fluorescence (2:20)
  • Lasers offered (3:30)
  • Laser efficiency trade-off (5:00)
  • Interchangeable lasers differentiation (6:40)

FT-Raman

6:00 minutes

Learn how to avoid fluorescence and obtain an efficient Raman scatter.

  • Raman module that fits in sample compartment (1:40)
  • 2 traditional detectors used in Raman systems (3:30)
  • Avoiding fluorescence (4:00)

Examine the fundamentals of Raman – including dipoles versus polarizabilities.

Polarizability Ellipsoids

7:00 minutes

Understand the theoretical basis of what causes a molecule to scatter light. Dive into an explanation using Benzene. Learn more about polarizability - the ability to cause a change within the electron cloud.

  • Explanation using Benzene (0:45)
  • Fundamental rule of IR (1:00)
  • Polarizability (2:25)
  • What is Alpha (4:00)
  • What allows the molecule to express a Raman scatter signal? (4:50)
  • Induced dipoles caused by polarizability change (5:30)

Learn how using a polarized laser and analyzer can tell you even more about the molecule.

Polarization

7:00 minutes

Learn about the ability of the Raman spectrometer to be sensitive to the polarization of the light and the polarization of the scatter. 

  • What is polarization (0:30)
  • Classic molecule example (1:00)
  • Normal modes (1:30)
  • TD symmetry (2:30)
  • IVV & IVH (3:00)
  • Polarization sensitivity (3:55)
  • Polarization for the alignment of molecules (5:40)
  • Overview of polarization (6:20)

Referenced recorded webinar below.

Combining what we’ve learned so far, we can now build a Raman spectrometer!

Instrumentation

11:00 minutes

Let’s get down to the instrument and how we do Raman spectroscopy.

  • The laser and it’s advantages (1:00)
  • The sample (2:40)
  • The polarizer (3:20)
  • The Raman scatter - Rayleigh and Raman light (4:00)
  • The lens (4:20)
  • The analyzer – 2nd polarizing element (4:50)
  • The filter to eliminate the Rayleigh light (5:20)
  • The diffraction element to spread the light (5:45)
  • The PMT & CCD detectors (6:40)
  • Spectral resolution (7:50)
  • Raman popularity (9:30)

Raman Detectors

8:10 minutes

Learn what type of detectors are used in the Raman spectrometer and how they are alike, how they differ, and how do you decide which detector to use.

  • Historical detectors: Photographic plate & Photo Multiplier Tube (0:30)
  • CCD: Charge Coupled Device (2:50)
  • EMCCD: Electron Multiplier Charge Coupled Device (4:30)
  • 600 or more spectra per second with the Thermo Scientific™ DXR™xi Imaging Microscope (6:00)
  • Which detector is right for you (6:50)

Sampling Modes

5:15 minutes

See how we present the sample to the Raman Spectrometer.

  • 90° sampling (0:25)
  • 180° sampling (1:30)
  • Raman advantage: little sample preparation (2:55)
  • Thermo Scientific™ DXR™ SmartRaman (4:15)

 


Advanced Application Topics

Now see how you can use Raman spectral analysis by watching webinars on specific Raman applications.

Want more great application content like the ones featured above? Check out our full library of Raman webinars, covering a variety of sample types such as: 

  • Carbons Nanomaterials
  • Forensics
  • Life Sciences
  • Minerals, Geology, and Gems
  • Pharmaceuticals
  • Polymers

Raman Webinar Library 

 


Raman Product Guide

Learn more about the instruments we have to offer when you click the links. Request to talk with an expert or schedule a demonstration any time.

Request advice

DXR2xi Raman Imaging Microscope
Highly usable, ultra-fast chemical imaging that speeds scientific investigations across a broad range of disciplines making it ideal for multiuser research facilities.  

DXR2 Raman Microscope
Versatile research-grade microscope offering a superior combination of performance and ease of use. Offers high spatial resolution mapping and point-and-shoot Raman for the most demanding analytical tasks.

DXR2 SmartRaman Spectrometer
Built for dedicated bulk sample analysis and designed for busy multi-purpose analytical labs. Provides reproducible and accurate results in a dependable, low-maintenance platform.

iXR Raman Spectrometer
Multimodal analysis for integration with other analytical tools. Performance comparable to laboratory research grade Raman spectrometers, and it is suitable for demanding research, product development, and manufacturing needs.

 


Raman Resources


Learn about Raman handheld instruments

Spectroscopy, Elemental & Isotope Analysis Resource Library

Access a targeted collection of application notes, case studies, videos, webinars and white papers covering a range of applications for Fourier Transform infrared spectroscopy, Near-infrared spectroscopy, Raman spectroscopy, Nuclear Magnetic Resonance, Ultraviolet-Visible (UV-Vis) spectrophotometry, X-Ray Fluorescence, and more.

Share