Photochemistry

Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to denote the events that occur in the presence of light, but it also includes the chemical reaction of light, which is known as photophysics.

Overview

Photochemistry involves the absorption of light by atoms or molecules, leading to a series of chemical reactions. The absorbed light is usually in the visible or ultraviolet part of the electromagnetic spectrum. A molecule, or small atomic particle, will absorb a quantity of light and jump to a high energy state. The energy absorbed can result in the breaking of chemical bonds, and the creation of new bonds. This process is responsible for the production of ozone in the Earth's stratosphere, and the process of photosynthesis in plants.

Laws of Photochemistry

The laws of photochemistry, first outlined by Theodor Grotthuss and Christian Ehrenberg, state that only the light absorbed by a molecule can be effective in producing a photochemical reaction and that for each photon of light absorbed by a chemical system, only one molecule is activated for a photochemical reaction.

Applications

Photochemistry has many practical applications, including photodynamic therapy, the use of light to kill cancer cells, and photolithography, the use of light to create patterns on a semiconductor surface.

See also

• Photobiology
• Photophysics
• Quantum mechanics
• Spectroscopy

References

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