An Introduction to Raman Microspectroscopy

CRAIC Technologies is the worlds leading developer of UV-visible-NIR range scientific instruments for microanalysis. These include the QDI series UV-visible-NIR microspectrophotometer instruments designed to help you non-destructively measure the optical properties of microscopic samples. CRAIC's UVM series microscopes cover the UV, visible and NIR range and help you analyze with sub-micron resolutions far beyond the visible range. CRAIC Technologies also has the CTR series Raman microspectrometer for non-destructive analysis of microscopic samples. And don't forget that CRAIC proudly backs our microspectrometer and microscope products with unmatched service and support.

Image Credit: Shutterstock/Forance


When photons interact with matter, such as when light is focused onto a sample in a microscope, it can either be reflected, absorbed or it can be scattered. We are interested in this last for the purposes of this tutorial.

The Raman Effect

Raman spectroscopy is the study of the interaction between light and matter in which the light that is inelastically scattered: a process called the Raman effect.

In a Raman spectroscopy experiment, photons of a single wavelength (in the visible range this would be light of a single color) are focused onto a sample. Most commonly a laser is used as it is a powerful monochromatic source. The photons interact with the molecules and are either reflected, absorbed or scattered. With Raman spectroscopy, we study the scattered photons.

Photons interacting with molecules most commonly scatter elastically. This is called Rayleigh scattering. Rayleigh scattered photons have the same wavelength as the incident light. However, approximately 1 out of a million photons are inelastically effect first described by Sir Chandrasekhara Raman in 1922.

With Raman scattering, the incident photon interacts with matter and its wavelength is either shifted lower or higher (red or blue shifted, respectively). Red shifted photons are the most common, having been subject to a "Stokes shift". What has happened is that the photon has interacted with the electron cloud of the functional groups bonds, exciting an electron into a virtual state. The electron then relaxes into an excited vibrational or rotational state (Figure 1). This causes the photon to lose some of its energy and is detected as Stokes Raman scattering. This loss of energy is directly related to the functional group, the structure of the molecule to which it is attached, the types of atoms in that molecule and its environment.

CRAIC Apollo Micro Raman Spectrometer

Figure 1. CRAIC Apollo Micro Raman Spectrometer

Of course, not every molecule or functional group exhibits Raman scattering. Factors such as the polarization state of the molecule (which determines the Raman scattering intensity) must be considered. The greater the change in polarizability of the functional group, the greater the intensity of the Raman scattering effect. This means that some vibrational or rotational transitions, which exhibit low polarizability, and will not be Raman active. They will not appear in a Raman spectra.

Resonance Raman Microspectroscopy

It should be noted that Raman scattering is a very weak effect as most photons are Rayleigh scattered. However, the intensity of the effect can be dramatically increased with resonance Raman microspectroscopy. In resonance Raman microspectroscopy, the wavelength of the exciting laser light coincides with the absorbance maximum of the molecule or functional group. Therefore, the photon can excite an electron to near an electronic excited state rather than a virtual excited state. This results in an increase in the Raman scattering intensity by a factor up to a million. This transition is therefore dominant in the spectra: the Raman spectra is of the molecule whose absorbance corresponds to the wavelength of the laser.

This information has been sourced, reviewed and adapted from materials provided by CRAIC Technologies.

For more information on this source, please visit CRAIC Technologies.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    CRAIC Technologies. (2022, August 01). An Introduction to Raman Microspectroscopy. AZoNano. Retrieved on May 21, 2024 from

  • MLA

    CRAIC Technologies. "An Introduction to Raman Microspectroscopy". AZoNano. 21 May 2024. <>.

  • Chicago

    CRAIC Technologies. "An Introduction to Raman Microspectroscopy". AZoNano. (accessed May 21, 2024).

  • Harvard

    CRAIC Technologies. 2022. An Introduction to Raman Microspectroscopy. AZoNano, viewed 21 May 2024,

Ask A Question

Do you have a question you'd like to ask regarding this article?

Leave your feedback
Your comment type

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.