Fluoresce

Fluoresce is a term used in physics and chemistry to describe the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore less energy, than the absorbed radiation. The most striking examples of fluorescence occur when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, and the emitted light is in the visible region.

Mechanism of Fluorescence

Fluorescence involves the elevation of electron energy levels by quanta of ultraviolet light, followed by the progressive falling back of the electrons into their original energy levels, with resultant emission of light quanta having frequencies in the visible range. The energy difference between the absorbed and emitted photons ends up as molecular rotations, vibrations or heat. Sometimes the absorbed photon is converted to a phonon which is a quantum of vibrational energy.

Applications of Fluorescence

Fluorescence has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, and optical brighteners, fluorescence resonance energy transfer, fluorescence lifetime imaging, fluorescent probe, and biochemistry (as in the biotech industry).

Fluorescence in Nature

Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An example is the orange fluorescent protein from the jellyfish Aequorea victoria. Many substances not ordinarily classed as fluorescent (e.g., sugar, alum) are found to emit light when heated (thermoluminescence).

See Also

• Phosphorescence
• Bioluminescence
• Chemiluminescence

References

Fluoresce Resources
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