A: Experiment Tutorials
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Fluorescence
A fluorescence measurement is a type of relative irradiance measurement in which the energy given off
by materials excited by light at shorter wavelengths is measured. Advantages of fluorescence include
High sensitivity, high speed (intensity changes on the order of picoseconds), and safety (nondestructive to
sample and no hazardous by-products). A typical fluorescence set-up is shown below. Note that the fibers
for the lamp and the spectrometer must be at a 90° angle to each other (or a CVD-DIFFUSE must be
used).
Fluorescence can be measured in the following modes:
• Scope mode: Scope mode is the preferred mode for configuring your acquisition parameters. The
signal graphed in Scope mode is the raw voltage coming out of the A/D converter. This spectral
view mode provides complete control of signal processing functions before taking absorbance,
transmission, reflection, and relative irradiance measurements. This mode reflects the intensity of
the light source, the reflectivity of the grating and mirrors in the spectrometer, the response of the
detector, and the spectral characteristics of the sample.
• Relative Irradiance mode: Relative Irradiance mode is the preferred mode for fluorescence
experiments. Relative irradiance spectra are a measure of the intensity of a light source relative to
a reference emission source. To perform a fluorescence experiment in Relative Irradiance mode,
first do a radiometric calibration using a blackbody of known color temperature. See
Relative
Irradiance for the experiment procedure.
See the following figures for examples of graphs of relative irradiance in a fluorescence measurement.
