Many organic compounds fluoresce, which is to say they emit light (usually visible but not always) when their electrons are excited by electromagnetic radiation of a lower wavelength. The amount of fluorescence energy emitted is only a small fraction of the energy input, typically only about 3% of excitation, and is more diffuse, scattering light in all directions. These conditions require a powerful spectrometer with high-sensitivity and long integration times to capture fluorescence data.

Fluorescence Spectroscopy, also called fluorometry or spectrofluorometry, is a very powerful tool. However, one important concern when applying this measurement technique is the possibility for stray excitation light to enter the spectrometer. Avantes offers several ways to mitigate this stray excitation light. One might employ a narrow bandwidth AvaLight-LED source to limit excitation wavelengths to those not part of the emission spectrum, or choose an AvaLight-Hal high-output broadband light source along with a bandpass or low-pass filter. A more mechanical solution might be to ensure the light can’t enter the fiber leading into the spectrometer with the use of a cuvette holder (use the CUV-UV/VIS-FL or the CUV-DA) to ensure the excitation path is perpendicular to the optical path for fluorescence measurements. Finally, it is possible to use the rate of fluorescence decay to separate the excitation-emission from the fluorescence measurement using a pulsed light source such as the AvaLight-XE Xenon flash and triggering options onboard the spectrometer.