Chemiluminescence

Chemiluminescence is light emitted by a chemical reaction when reaction products or intermediates enter electronically excited states, without light serving as the excitation source.

Excited state: A higher-energy state of an atom or molecule than its ground state. Chemiluminescent reactions produce excited states that emit light as they relax.
Chemical energy: Energy stored in chemical substances and released or absorbed during chemical reactions. Its conversion provides the energy that drives chemiluminescent emission.
Luminol: A chemical compound that emits blue light when oxidized under suitable conditions. Luminol's emission makes it useful for detecting trace blood and illustrating chemiluminescence.
Photoluminescence: Light emission from a material after it absorbs photons. It requires optical excitation, unlike chemiluminescence.
Chemical kinetics: The study of reaction rates and the steps by which chemical reactions proceed. Reaction pathways and rates determine how quickly chemiluminescent emission appears and fades.
Electronic state: A quantum-mechanical state describing the energy and arrangement of electrons in an atom or molecule. Emission depends on the energy difference between electronic states.
Forensic chemistry: The application of chemical analysis to evidence used in legal investigations. Luminol-based chemiluminescence can reveal traces of blood at crime scenes.
Electroluminescence: Light emission caused by an electric field or electric current acting on a material. Electrical excitation distinguishes it from reaction-driven chemiluminescence.
Quantum yield: The number of emitted photons per absorbed photon or, in chemical emission, per initiating event. It quantifies how efficiently reaction events produce emitted photons.
Photon: A quantum of electromagnetic radiation that carries energy and momentum. Each emitted unit of chemiluminescent light is a photon.

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