Raman spectroscopy is the study of inelastically scattered light. When photons strike a crystal, they can be scattered either elastically or inelastically. The process by which light is scattered elastically is known as Raleigh scattering and does not change the energy of the outgoing beam. However, if the incoming photons scatter inelastically in a solid, the outgoing photons (Raman signal) will be shifted in energy from the original incoming photons. These shifts in energy of the original incoming photons are quantized (phonons, quanta of lattice vibrations, are produced and make up the difference in energy) and can tell us something about the material being studied. Data are collected by a charge-coupled device (CCD) cooled by liquid nitrogen and attached to a very high resolution spectrometer. This results in a plot of intensity vs. energy, where peaks correspond directly to discrete phonon modes in the crystal. This method of study is non-destructive and therefore very useful in the identification and characterization of materials.
There are many good references on the theory of Raman scattering. A nice online tutorial by Kaiser Optical Systems, Inc. will give those interested more information about the nuts and bolts of Raman Spectroscopy.
Currently there are multiple independent projects as well as collaborations in the McNeil group. We study a wide range of materials in various conditions.
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