Hello, steemians today I would like to address a topic that for many will be somewhat simple and even basic but that for others will be of great interest and it is about fluorescence and phosphorescence.

There is a lot of confusion on some occasions when talking about one or the other, but that is going to end. I will explain what is the difference (and similar, in addition to the word itself) between these two phenomena and also make clear how they can shine in the way they do.

Source
CC BY 2.0

Let's start by making clear each one.

Fluorescence.

It is basically a phenomenon by which some substances have the ability to absorb photons with a certain energy, and then release these photons with less energy. This process is almost immediate, the light is received and immediately emitted in millionths of a second, therefore we can say that the fluorescence lasts as long as the stimulus, because when it ceases, the fluorescence phenomenon also stops.

Source
CC BY-SA 4.0

We can describe this phenomenon in the following way:

The electrons of an atom or a molecule are orbiting at different levels, and each level has a certain energy. Then when the light or X-rays reach electrons that are at low energy levels, they are excited, and they "switch" to an orbit of higher energy. However, the electron remains unstable in this orbit of higher energy and must return to its corresponding orbit. When it does, it releases the energy is absorbed. This energy is partially translated, in fluorescent substances, into emitted light. The rest of the energy is translated into vibrations of the molecule, that is, heat.

Source
Public Domain

Phosphorescence.

This phenomenon is almost equal to that of fluorescence, in which various electrons are stimulated by light, moving into an orbit of higher energy, and when they return to their resting state, they release part of this energy in the form of light. But on the contrary of fluorescence, this phenomenon occurs with a small delay, even when the stimulating source is no longer present.

Source
Public Domain

It should be noted that in the case of this phenomenon, the substance usually continues to emit light for a longer period even if we eliminate the stimulus since the release of energy occurs very slowly. We can say then, that phosphorescent substances have the ability to store electromagnetic energy, even for a period not too long.

So what do both phenomena have in common?

Both phosphorescence and fluorescence have the same process by which they emit light. Both compounds have a molecular structure that gives them the ability to absorb a certain wavelength of light.

However, the situations of light absorption are not stable, and the atoms of the molecules tend to recover their original state, returning the excited electron to its lower energy orbital, releasing, in turn, part of the energy absorbed in the form of radiation with a wavelength different from the ultraviolet absorber, in this case in the range of visible light and, from there, we can see how they shine.

Basically, its similarity lies in the process of light absorption.

What makes them different between them.?

The main difference between these two phenomena is based on the ability to store energy. That is the difference between both phenomena. The fluorescence absorbs the energy of the ultraviolet light and, immediately, emits the luminous radiation.

Source
Public Domain

This is how fluorescent lamps work, for example. The electric discharge when turned on causes an ultraviolet light to be emitted, but there is a layer of phosphorus that absorbs that light and re-emits it at a wavelength that we can see and that illuminates the room.

In the case of phosphorescence, it begins the same, absorbing the ultraviolet radiation, but stores the energy, slowing down the subsequent emission, being able to emit that luminous radiation little by little during minutes or hours after having ceased the initial source of excitatory radiation.

There is a similar phenomenon, which occurs in nature. It is known as bioluminescence, only in this case the energy that excites the electrons, come from the energy released in a chemical reaction, not by absorption of ultraviolet energy.

---

References.

• https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Spectroscopy/Electronic_Spectroscopy/Fluorescence_and_Phosphorescence
• https://www.britannica.com/science/fluorescence
• http://www.chemistryandlight.eu/index.php/fluorescence/
• https://www.majordifferences.com/2016/11/7-differences-between-fluorescence-and-Phosphorescence.html#.WqLmWGpubIU
• http://www.chemistryandlight.eu/index.php/phosphorescence/
• https://www.britannica.com/science/phosphorescence
• http://www.chemistryviews.org/details/education/10468955/What_are_Fluorescence_and_Phosphorescence.html

---

SteemSTEM

SteemSTEM is a community-driven project that now runs on Steemit for more than a year. We seek to build a community of science lovers on Steemit and to promote well written/informative Science Technology Engineering and Mathematics (STEM) postings in order to make Steemit a place for fascinating STEM content.

So if you want to read more scientific articles of good quality, visit the hashtag #steemstem and ScienceON.

Disclaimer:
[1] All the content exposed in this post is a compilation of different sources besides my knowledge in the subject.
[2] All the images used are correctly labeled for reuse.