What is Raman Spectroscopy?

Raman spectroscopy is a non-destructive chemical analysis technique which offers detailed information regarding chemical structure, phase and polymorphic crystallinity, and molecular interactions. It is ideal for sample identification and quantification processes.


Raman spectroscopy works by shining a monochromatic light source—usually a laser—onto a sample and detecting the scattered light. Most scattered light is at the same frequency as the excitation source and does not offer helpful information, this is known as either Rayleigh or elastic scattering.


A small amount of the scattered light shifts in energy from the laser frequency because of interactions between the incident electromagnetic waves and the vibrational energy levels of the molecules in the sample. Plotting the intensity of the shifted light against the frequency produces a Raman spectrum of the sample.


Raman spectra usually plot according to the laser frequency, meaning the Rayleigh band falls between 0 cm-1. On this scale, the band positions sit at the frequencies corresponding to the energy levels of varying functional group vibrations.


What Does Raman Spectroscopy Provide Information About?

Raman spectroscopy gives insight into the chemical structure and identity of a material as well as its phase and polymorphism, intrinsic stress/strain and contamination and impurity. Raman spectroscopy also employs both qualitative and quantitative applications. Spectra are specific and chemical identifications that carry out by using search algorithms against digital databases. Band areas are proportional to concentration, meaning Raman spectroscopy is amenable to straightforward quantitative analysis.


Benefits of Raman Spectroscopy

Raman spectrums usually depict a distinct chemical fingerprint for a specific molecule or material which can identify the material or distinguish it from others quickly. Alongside mapping (or imaging) Raman systems, image creation is based on the sample’s Raman spectrum. These images display distribution of individual chemical components, polymorphs and phases, and variation in crystallinity.


Uses of Raman Spectroscopy

The use of raman spectroscopy is often in in microscopic analysis, with a spatial resolution in the order of 0.5-1 µm using a Raman microscope. The Raman microscope combines a Raman spectrometer with a standard microscope.  It enables high magnification visualization of a sample and Raman analysis using a microscopic laser spot.


Raman spectroscopy is also useful for the analysis of micron size particles of volumes. It can also be used to analyze individual layers within a multilayered sample.  It then pinpoints contaminants and features under the surface of a transparent sample.


Raman spectroscopy is frequently used for the analysis of solids, powders, liquids, gels, inorganic/organic and biological materials, pure chemicals, mixtures and solutions.  In addition, it is used for metallic oxides and their corrosions.


Raman spectroscopy use is often in art and archeology to characterize pigments, ceramics and gemstones. It’s use is also in geology to identify minerals and their distribution, fluid inclusions and phase transitions. In addition, raman spectroscopy is useful for disease diagnoses, ensuring uniformity and component distribution in pharmaceuticals and monitoring chemical reactions.


Many lasers from Laser Quantum are suitable for Raman spectroscopy. To find out more, contact us today.