# What is the difference between the following terms: Incandescence, luminescence, fluorescence, phosphorescence, chemiluminescence and bioluminescence? [closed]

What are the differences between incandescence, luminescence, fluorescence, phosphorescence, chemiluminescence, bioluminescence?

## closed as off-topic by Todd Minehardt, Jannis Andreska, Klaus-Dieter Warzecha, M.A.R., JanNov 16 '16 at 19:14

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That was a 'catchy' question ;)

First a broad division into : Incandescence and Luminescence.

Incandescence is the emission of light from a body that is heated until it glows.

Luminescence is the emission of light by a substance for any reason other than rise in its temperature.

Now the following come under Luminescence:

If the cause of the excitation is due to photons striking atoms, the associated emission of light is called photoluminescence. If it is due to electrons, then the emission of light is referred to as electroluminescence.

If the luminescence results from a chemical reaction, it is chemiluminescence. A form of chemiluminescence, where the emission of light is due to a chemical reaction occurring in vivo, then it's called bioluminescence.

If the luminescence persists significantly (according to my Oxford Science dictionary, a period of time greater than 10 nanoseconds would be "significant") after the exciting cause has been removed, it is called phosphorescence. If it fails to persist for longer than 10 nanoseconds, then it's called fluorescence.

EDIT- @KlausWarzecha answered the Fluorescence-Phosphorescence conundrum better in his answer here : What happens to electrons in metal complexes after excitation by visible light?

There are however cases, in which the initially formed excited singlet state species first relaxes to its lowest vibrational mode and the emits a photon to reach the ground state.

$$\ce{S_1 -> S_0 + h\nu_{f}}$$

This deactivation via radiation is known as fluorescence. Fluorescence lifetimes are typically rather short (in the ns range) and the emitted photon has a lower energy than the absorbed one.

and on phosphorescence,

In other cases, the excited singlet state undergoes a change in the spin multiplicity (Intersystem crossing) to a triplet state.

$$\ce{S_1 ->[ISC] T_1}$$

These excited triplet states are usually much longer-lived. When they eventually deactivate via emission of a photon, this process is known as phosphorescence.

$$\ce{T_1 -> S_0 + h\nu_{p}}$$

Note that the way I 'defined' fluorescence and phosphorescence has been greatly oversimplified (and possibly wrong), but it should suffice for your purpose. ;)