fotolisis

Fotolisis, or photolysis in English, is the chemical decomposition of a substance caused by light. It occurs when a molecule absorbs photons with enough energy to break chemical bonds or to initiate other chemical transformations. In many cases the absorbed energy promotes the molecule to an electronically excited state, from which bond rupture or rearrangement may occur. Photolysis is a fundamental process in photochemistry and often involves direct bond cleavage driven by light.

The rate and outcome of photolysis depend on the light spectrum, the molecule’s light absorption properties, and the quantum yield, which describes the efficiency of converting absorbed photons into chemical change. Only photons with sufficient energy and appropriate wavelengths can trigger photolysis for a given species; many molecules require ultraviolet or visible light.

Photolysis occurs in both gas phase and solutions. In the atmosphere, photolysis of nitrogen dioxide, ozone, formaldehyde, and other species drives the production and destruction of radicals such as hydroxyl and ozone, influencing air quality and climate. In solution, photolytic reactions are used to decompose pollutants and in organic synthesis, where light triggers bond cleavage or rearrangements.

Applications and implications: photolysis influences environmental chemistry, atmospheric processes, and industrial photochemistry. It underpins solar-driven reactions, solar energy conversion, and various remediation strategies. See also photochemistry, photodissociation, photocatalysis.