File:Chemical investigations with light.jpg

English: Upper part of this picture show Raman spectrum of Acetone while bottom part show intensity trace of this spectrum.

A green diode laser at 532 nm was loosely focused on to a sample of acetone placed in a quartz cuvette. Scattered light from the acetone sample was collected at right angle from the incident light with a microscope objective and collected light was focused on to the input slit of a home made spectroscope with a second microscope objective. Scattered light, dispersed into its components colors was pictured using a canon DSLR camera with exposure time of ~ 4 minutes.

It can be seen in this picture that most of the scattered light is of the same color as the incident light (bright green halo on left side of the picture). However, along with the incident light, there are also some new discrete colors of light produced after interaction with the sample. These new colors are produced when some of the energy in the incident light is taken up by the vibrating molecular bonds in the sample, resulting in scattered light being shifted towards redder wavelengths (Stokes shift). Different molecular bond vibrations shift incident light by different amounts. This shift is usually measured in wavenumbers (cm-1) and can be used for the identification of chemical bonds present in a sample. Raman spectra are often used like a chemical fingerprints.