Introduction

La fluorescence and phosphorescence They are two optical phenomena that are often confused. Both have to do with the emission of light after a material has been excited by an external energy source. However, there are a number of key differences that it is worth knowing to really understand what distinguishes each phenomenon.

Fluorescence

Fluorescence it is a process by which a material emits light when excited by an external energy source, such as visible light or ultraviolet radiation. When the energy source is removed, the material stops emitting light. This phenomenon is commonly observed in substances such as fluorescent marker ink, lead-free dyes used in medicine and biology, or fluorite crystals that emit light under ultraviolet light.

Underlying mechanisms

Fluorescence occurs because the atoms of the excited material absorb energy from the external source and jump to a higher energy level. But these atoms cannot remain at this level for too long, as they tend to return to their low energy state, releasing the absorbed energy. The release occurs in the form of visible light of wavelength longer than the wavelength of the light originally absorbed.

Phosphorescence

Phosphorescence, on the other hand, is a phenomenon in which light emission continues after external stimulation has ceased, albeit gradually. In other words, a phosphorescent material continues to emit light after being exposed to a light or radiation source, but unlike fluorescence, the emission does not stop abruptly but rather fades out little by little.

Underlying mechanisms

The mechanism underlying phosphorescence is different from that of fluorescence. Instead of jumping to a higher energy level and quickly returning to its original state, the atoms of the phosphorescent material stay at an intermediate energy level longer before releasing the absorbed energy as light.

Conclusion

In summary, fluorescence and phosphorescence are two phenomena related to the emission of light by materials excited by an external energy source. Fluorescence has an immediate and abrupt light emission and ceases once the external source is removed. Phosphorescence, on the other hand, has a longer, more gradual emission even after the external energy source is gone.

References:

• Valiente, J. et al. (2017). Fluorescence and phosphorescence: fundamentals and applications. Journal of Physics and Chemistry, vol. 4, pp. 142-156.
• Gupta, V. (2019). Fluorescence and Phosphorescence. New York: Springer.

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