Fluorescence
and Fluorescence Excitation Spectroscopy
The
powerful technique of fluorescence excitation significantly enhances the
capabilities of conventional fluorescence spectroscopy, which offers insights
into chemical composition of the examined specimens. In a conventional
fluorescence measurement the excitation wavelength is fixed and the detection
wavelength varies, while in a fluorescence excitation measurement the detection
wavelength is fixed and the excitation wavelength is varied across a region of
interest. This very important capability makes it possible to produce an
excitation/emission matrix that fully characterises the sample in a
matter of minutes. This is in contrast, with fluorescence at a single
excitation wavelength or with wide band excitation (such as in a fluorescence
microscope) which provides only partial information. Importantly, the
fluorescence excitation spectra contain information that is complementary
to the fluorescence spectra. This facility is of importance in many biological
applications, where the objective is frequently to make a fine distinction
between two parts of a specimen with broad and very similar fluorescence
curves. Applications of fluorescence excitation are as diverse as those
of fluorescence and specimens can be examined rapidly and non-destructively.