Chapter
1:
Fluorescence Theory
Chapter
2:
Advantages of Fluorescence
Chapter
3:
Instrumentation
Chapter
4:
Variables of Fluorescence
Chapter
5:
Calibration and Standards
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An
Introduction to
Fluorescence
Measurements
Chapter 1
- Fluorescence Theory
Two excellent textbooks covering the
details of fluorescence spectroscopy are: Principles of Fluorescence
Spectroscopy by Joseph R. Lakowicz[1] and Practical Fluorescence
by George G. Guilbault.[2] In these books, Lakowicz and Guilbault describe
a number of different fluorescence phenomena. For the instruments manufactured
by Turner Designs, the fluorescence normally observed in solution is
known as Stokes fluorescence.
Stokes fluorescence is the reemission
of longer wavelength (lower frequency) photons (energy) by a molecule
that has absorbed photons of shorter wavelengths (higher frequency).
Both absorption and radiation (emission) of energy are unique characteristics
of a particular molecule (structure) during the fluorescence process.
Light is absorbed by molecules in about 10-15 seconds which
causes electrons to become excited to a higher electronic state. The
electrons remain in the excited state for about 10-8 seconds
then, assuming all of the excess energy is not lost by collisions with
other molecules, the electron returns to the ground state. Energy is
emitted during the electrons' return to their ground state. Emitted
light is always a longer wavelength than the absorbed light due to limited
energy loss by the molecule prior to emission.[3]
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Figure 1 shows a representative
excitation (absorbance) and emission spectrum.[4]
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Continue...
to Chapter 2
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