Fotokeemilisi

Fotokeemilisi is a term used to describe phenomena and processes that are driven by light-induced chemical reactions. In practical terms, fotokeemilisi refer to reactions and transformations that require photons to proceed or to proceed more readily than they would under heat alone. The term is often used in Finnish-language contexts to discuss photochemical processes in gases, liquids, and solids.

Core concepts include the absorption of photons by a chemical species, which promotes molecules to excited electronic states. This excitation can enable bond cleavage, new bond formation, electron transfer, or energy transfer to other species. The outcome depends on factors such as the light wavelength and intensity, the chemical environment, and the presence of sensitizers or catalysts. Photochemical reactions can proceed via direct photolysis, photosensitized processes, or photocatalysis, and may involve radical intermediates, isomerizations, or charge-transfer steps. Quantum yield and photostability are common measures used to quantify efficiency.

Applications of fotokeemilisi span several fields. In environmental chemistry, photochemical reactions contribute to the degradation of pollutants and to atmospheric chemistry, including the formation and breakdown of reactive species. In materials science, photochemical processes enable photocuring, photoinduced polymerization, and photolithography. In energy research, photochemical steps underpin certain solar conversion and photoelectrochemical strategies.

Measurement and study typically employ spectroscopy, actinometry for light dose, and time-resolved methods to capture short-lived excited states. Understanding fotokeemilisi helps explain how light interacts with matter to drive chemical change, with implications for synthesis, aging, and environmental impact.