Phosphorescence

Definition

Phosphorescence is the phenomenon where certain materials emit light after being energized and continue to glow for an extended period even after the energy source has been removed. This occurs due to the delayed re-emission of absorbed photons.

5 Must Know Facts For Your Next Test

1. Phosphorescence involves electronic transitions between different energy states, particularly from excited singlet states to metastable triplet states.
2. The delay in emission is due to the forbidden nature of the transition from the triplet state back to the ground state, making it much slower than fluorescence.
3. Common examples include glow-in-the-dark materials and certain types of rocks and minerals.
4. Phosphorescent materials can be used in safety signs, watches, and other applications requiring long-lasting illumination without continuous energy input.
5. The intensity and duration of phosphorescence depend on factors such as temperature, type of material, and previous exposure to light.

Review Questions

• What distinguishes phosphorescence from fluorescence?
• Why do phosphorescent materials continue to emit light after the excitation source is removed?
• In what applications might you find phosphorescent materials?

Related terms

Fluorescence:

Emission of light by a substance that has absorbed light or other electromagnetic radiation; it ceases almost immediately when the excitation source is removed.

Triplet State: An excited state of a molecule with two unpaired electrons having parallel spins, contributing to longer-lived luminescence like phosphorescence.

Electron Excitation: $Process$ where an electron absorbs energy and moves to a higher energy level within an atom or molecule.