Fluorolog-3 v. 2.2 (10 Sep 2002)
Optimizing Data Acquisition
4-16
Selecting the appropriate bandpass
The bandpass (wavelength spread) affects the resolution of your spectra. If the bandpass is
too broad, narrow peaks separated by a small change in wavelength may be unresolved. For
example, for two 2-nm peaks 5 nm apart, and a bandpass of 10 nm, one broad peak, instead
of two well-defined ones, will be visible.
By adjusting the slit widths, you can control the intensity and bandpass of the light. The slits
of the excitation spectrometer determine the amount of light that will pass through the exci-
tation spectrometer to the sample. The emission spectrometer slits control the amount of
fluorescence recorded by the signal detector.
Bandpass can be calculated using the following formula:
bandpass (nm) = slit width (mm) × dispersion (nm/mm)
The dispersion of the Fluorolog
®
-3 spectrofluorometer system depends upon the type of
monochromator and the groove spacing of the gratings. For example, a Fluorolog
®
-3 with a
single-grating monochromator and 1200 groove/mm gratings has a dispersion of 4.0
nm/mm, while a Fluorolog
®
-3 with a double-grating monochromator and 1200 groove/mm
gratings has a dispersion value of 2.0 nm/mm. Below is a table listing various monochroma-
tors, installed gratings, and their respective dispersions.
Monochromator Grating
groove-density
(grooves/mm)
Dispersion of the monochromator
1200 2.1
600 4.2
Double
300 8.4
1200 4.2
600 8.4
Single
300 16.8
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