Physical and Theoretical Chemistry

Photochemistry

The study of chemical reactions, isomerizations and physical behavior that may occur under the influence of visible and/or ultraviolet light is known as Photochemistry. Photochemistry is the underlying mechanism for all of photobiology. When a molecule absorbs a photon of light, its electronic constitution changes, and it reacts differently with other molecules. The energy that is absorbed from light can effect in photochemical changes in the absorbing molecule, or in an adjacent molecule (e.g., photosensitization). The energy can also be set off as heat, or as lower energy light, i.e., fluorescence or phosphorescence, in order to    give back the molecule to its ground state. Each type of molecule has a different preference for which of these different mechanisms it utilizes to get rid of absorbed photon energy, e.g., some prefer fluorescence over chemistry.