Raman Spectroscopy is founded on the Raman effect – the inelastic scattering of light.  Whenever a transparent medium has radiation pass through it, it will scatter photons in all directions.  Most of these scattered photons will have the same wavelength as the incident radiation, but a small fraction will have a different wavelength.  These shifts in wavelength are caused by a change in vibrational energy of the medium.  The Raman spectrum is merely a plot of intensity of scattered photons.  In stimulated Raman, the sample receive the normal laser light source, and an additional beam of photons at the wavelength that the sample scatters to – which “stimulates” the Raman effect.  Traditional Raman spectroscopy was performed with laser systems that had picosecond resolution.  At the CCBD we are able to improve on that resolution by three orders of magnitude to a sub 50 femtosecond resolution.  This allows us to pursue knowledge about short-lived intermediate in fundamental chemical processes.