Photodissociation

Photodissociation is the breaking of a chemical bond after a molecule absorbs a photon. The absorbed energy drives the molecule into fragments, sometimes through electronically excited states.

Photochemistry: The study of chemical reactions initiated by light. Photodissociation is a light-driven chemical reaction within this broader field.
Atmospheric photochemistry: Chemical reactions in the atmosphere initiated or driven by sunlight. Photodissociation supplies reactive atoms and radicals that drive many atmospheric reaction cycles.
Photon: A quantum of electromagnetic radiation that carries energy and momentum. A photodissociation event begins when a molecule absorbs a photon.
Oxygen photodissociation: The breakup of molecular oxygen into oxygen atoms after ultraviolet photon absorption. Its products provide oxygen atoms that participate in ozone formation.
Franck–Condon principle: The principle that electronic transitions occur faster than nuclei can move, leaving molecular geometry nearly unchanged during absorption. It explains why photon absorption often places a molecule in a vibrationally excited state.
Ozone–oxygen cycle: The linked formation and photochemical destruction of ozone and molecular oxygen in the atmosphere. Ultraviolet photodissociation of oxygen and ozone sustains this cycle.
Molecular electronic state: A quantum state describing the electronic energy and arrangement of a molecule. Absorption commonly transfers the molecule from its ground state to an excited electronic state.
Ozone photodissociation: The breakup of ozone into oxygen-containing fragments after absorbing light. Its wavelength-dependent channels shape atmospheric ozone chemistry.
Potential energy surface: A representation of a molecule's energy as a function of its nuclear coordinates. The excited-state surface determines whether fragments separate or the molecule returns to its original form.
Stratospheric ozone depletion: The reduction of stratospheric ozone caused by chemical reactions, especially those involving chlorine and bromine radicals. Light-driven release of halogen radicals from compounds helps initiate ozone-destroying chemistry.

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