Stark-Einstein principle

The first law of photochemistry, named the Grotthus-Drapper Principle, states that for a photochemical reaction to occur, the first event must be the absorption of light by some component of the system. The second law of photochemistry, named the Stark-Einstein Principle, states that a molecule can only absorb one quantum of radiation. The absorbed energy in the resultant excited molecule may be dissipated by either photophysical or photochemical processes. It is the latter of these that eventually changes the chemical and mechanical properties of the substance (26,27). Thus, the reactions based on the absorption of radiation by the chemical components of modern papers are of prime importance in discoloration. 

With this mechanism, the quantum yield ( ) is approximately equal to one for acetone and hydrogen peoxide one excited benzophenone molecule results in the formation of one acetone molecule and one H2O2 molecule, and according to the Stark-Einstein principle, a molecule can only absorb one quantum of radiation. Therefore ... 

Only light that is absorbed can produce a chemical change, a principle embodied in the Grotthuss-Draper law of photochemistry. This is true whether radiant energy is converted to some other form and then stored or is used as a trigger. Another important principle of photochemistry is the Stark-Einstein law, which specifies that each absorbed photon activates only one molecule. Einstein further postulated that all of the... 

The second principle of photochemistry is called the photochemical equivalence law, or the Stark-Einstein law, which states the absorption of light occurs in the quantum unit of photon or one molecule absorbs one photon, and one or less molecule can be photolyzed accordingly. ... 

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