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sample and sample heating with resultant black-body radiation. One serious problem associated with
Raman spectroscopy is the fluorescence that can accompany the Raman scattering, and can be as much
as six to eight orders of magnitude stronger then the Raman light. Often, when trying to examine
Raman scattering, fluorescence is the only phenomenon observed. The fluorescence can come from a
variety of sources. It can be caused by trace impurities, coatings on polymers, additives etc., that
provide so much background fluorescence that the Raman spectrum of the major component cannot be
discerned. The use of near infrared excitation can help solve this problem. It has been found, that the
use of light having a wavelength around 1 mµ to irradiate the sample virtually eliminates the fluorescent
problem.

Figure 2.14
Infrared and Raman Spectra of Some
Gasoline's of Different Octane Ratings
Courtesy of Nicolet Inc.

However, other problems remain such as photochemical changes in the sample and black-body
radiation produced by local heating. These problems must be carefully distinguished from fluorescence,
as the experimental