When you look through a piece of coloured glass at a scene, it is no surprise that the resulting colours are different than without it, but surprisingly this is also true when you look through a perfectly colourless material, and even more astonishingly, there are new colours created which weren't present in the original scene.

Chandrasekhara Venkata Raman was inspired to study how light moves through transparent materials after observing that the sea and glaciers are blue in colour, but was not content with the explanation that it was just because they were reflecting the blue sky. Through detailed experimentation, he discovered that some of the light travelling through a medium will be scattered and in the process change colour by giving some energy to, or taking some energy from the material. The change depends on the chemical composition of the material, and so when light of a fixed energy is sent through it, the resulting spectrum of colours give a "molecular fingerprint" which can be used to identify the material without having to physically touch or destroy part of it.

The new phenomenon was given his name and is known as Raman scattering, a discovery which won him the Nobel Prize for Physics in 1930, making him the first non-white recipient of a Nobel Prize in any science. The ability to simply shine a light on an unknown substance and non-destructively identify its molecular composition is incredibly useful and found application in a wide range of applications from unobtrusively monitoring chemical reactions, through forensic analysis to safely studying nuclear reactions and identifying different types of cancer. By combining Raman detection with microscopy, it is possible to read the molecular fingerprint of microscopic objects, including individual living cells and be able to identify the type of cell and if it is cancerous.

Want to learn more?

The study of how light interacts with matter is a core part of all physics degree programmes at Heriot-Watt (in particular the 3rd year course B29QS Quantum Theory and Spectroscopy and the 5th year course B21MT Soft Matter and Biophysics courses cover material relevant to Raman spectroscopy). Raman microscopy is also used extensively by several research groups at Heriot-Watt and opportunities to get hands-on with this technology are available in the form of summer internships and final year projects.