Raman spectra are unique fingerprints of solid, liquid or gaseous materials. These materials can consist of one or even more components. Raman spectra provide answers easily and quickly to the questions:
What is it? can be answered by comparing a sample spectrum with reference spectra or spectra libraries. Analyzing Raman intensities provide the answer to the question: How much?
Raman and infrared spectra complement each other
The Raman and infrared (IR) spectrum of the same material look partly similar. Although both spectroscopic techniques are based on different physical processes most Raman and infrared bands are observed at the same positions. Whether a band is observed and with which intensity depends on selection rules. The whole vibrational information of a material is provided by the knowledge of its Raman and the infrared spectrum.
Typically, a spectrum represents intensities depending on energy. The energy scale is expressed in frequencies, wavelengths, and electron volt. In vibrational spectroscopy the energy scale is preferably expressed in wavenumbers. One advantage of the wavenumbers is that they are directly proportional to energy:
Wavenumbers are easily converted into the more familiar wavelength scale by calculating the reciprocal. In semiconductor applications the energy scale is often expressed in electron volts instead of wavenumbers.
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