The main difference between the fluorescence and the phosphorescence is that fluorescence occurs and cease quickly whereas phosphorescence takes longer time to glow and cease slowly after the removal of the source.
Fluorescence Vs. Phosphorescence
When an atom or a molecule absorbs energy, it becomes excited that is high energy and unstable state. As we know, every atom or molecule wants to be stable so, it emits energy in the form of radiations or photons to return to its ground state that makes the item glow which is known as photoluminescence. There are two types of photoluminescence, i.e. Fluorescence and Phosphorescence. In both these types, the energy of the emitted photons is lower than the absorbed photons and emission has a longer wavelength than the incident light. But, they differ in the duration of the process. Fluorescence occurs much more rapidly than phosphorescence. It occurs speedily and ceases quickly after the removal of the source. On the other hand, during phosphorescence emission of radiations takes time to start and it remains for some time even after the removal of the source. So, the time period between emission and absorption of energy is short in fluorescence but comparatively long in phosphorescence. In fluorescence, absorption process changes the transition from ground to singlet excited state without changing the direction of spin. On the flip side, during the phosphorescence absorption process involves the transition from ground to triplet excited state and also changes the direction of the spin. Gemstone fluoresce, including talc, gypsum, vitamins, chlorophyll extract, and jellyfish, etc. are the examples of fluorescence whereas, Glow of toys, and clock dials, etc. after switching off the light in the room are the examples of phosphorescence.
What is Fluorescence?
Fluorescence takes place when electrons travel from their low energy ground state to a high energy excited state. These electrons keep their spin the same as in the ground state, but when they emit energy when they return to the ground state. This energy has a longer wavelength than the absorbed one. We can see a glowing light if this longer wavelength lies within the visible spectrum. The time interval between the absorption and emission of energy is very short, and it suddenly ceases emission on the removal of the source of excitation.
What is Phosphorescence?
Phosphorescence is like fluorescence, but, it changes the spin when the electron moves into the excited state. Electrons spin in a specific direction based on the magnetic momentum. When a compound displays phosphorescence, its electron has been provided with enough additional energy to change the direction of the spin. This change in a spin causes the emission to live for a long time because it takes a longer time for the electron to release all of its energy.
- A type of photoluminescence in which energy absorption by atom or molecule is followed by a quick release of energy is known as fluorescence whereas, a type of photoluminescence in which energy absorption by atom or molecule is followed by slow release of energy is known as phosphorescence.
- During fluorescence, the emission of energy or light suddenly ceases on the removal of the source of excitation, on the other hand, the emission of energy or light remains for some time in phosphorescence even after the removal of the source of excitation.
- The excited atom has a short lifetime in fluorescence before its transition to low energy state conversely, the excited atom has a long lifetime in phosphorescence before its transition to low energy state.
- The time interval between the absorption and emission of radiations is very short in fluorescence on the flip side; the time interval between the absorption and emission of radiations in phosphorescence is comparatively long.
- Absorption process during fluorescence changes the transition from ground to singlet excited state while in phosphorescence absorption process involves the transition from ground to triplet excited state.
- The direction of spin does not change during fluorescence; on the other hand, phosphorescence changes the direction of spin.
- During fluorescence, the emission has a longer wavelength than the incident light whereas, in phosphorescence emission has longer wavelength then fluorescence.
- A fluorescent material provides an immediate flash or afterglow on excitation on the other side; a phosphorescent material appears to glow in the dark.
- Gemstone fluoresce, including talc, gypsum, vitamins, chlorophyll extract, and jellyfish, etc. are the examples of fluorescence while, the glow of toys, and clock dials after switching off the light in the room and signboard illuminating on the night, etc. are the examples of phosphorescence.
Above discussion summarizes that fluorescence and phosphorescence are the two types of photoluminescence. Fluorescence does not change the spin of electrons and occur and cease rapidly whereas, phosphorescence changes the spin of electrons and takes time to occur and stop.