The general reaction of photosynthetic photolysis can be given in terms of photons as: The chemical nature of "A" depends on the type of organism.
Chlorophylls absorb light in the violet-blue and red parts of the spectrum, while accessory pigments capture other wavelengths as well.
Each absorbed photon causes the formation of an exciton (an electron excited to a higher energy state) in the pigment molecule.
The electron-deficient reaction center of photosystem II (P680*) is the strongest biological oxidizing agent yet discovered, which allows it to break apart molecules as stable as water.
Two water molecules are complexed by the manganese cluster, which then undergoes a series of four electron removals (oxidations) to replenish the reaction center of photosystem II.
At the end of this cycle, free oxygen (O2) is generated and the hydrogen of the water molecules has been converted to four protons released into the thylakoid lumen (Dolai's S-state diagrams).
They are passed down another electron transport chain and finally combine with the coenzyme NADP+ and protons outside the thylakoids to form NADPH.
[8][9][10][11][12] This approach has been further investigated by Gregory Scholes and his team at the University of Toronto, which in early 2010 published research results that indicate that some marine algae make use of quantum-coherent electronic energy transfer (EET) to enhance the efficiency of their energy harnessing.
Photoacids are a convenient source to induce pH jumps in ultrafast laser spectroscopy experiments.
The two most important photodissociation reactions in the troposphere are firstly: which generates an excited oxygen atom which can react with water to give the hydroxyl radical: The hydroxyl radical is central to atmospheric chemistry as it initiates the oxidation of hydrocarbons in the atmosphere and so acts as a detergent.
[17] In addition, photolysis is the process by which CFCs are broken down in the upper atmosphere to form ozone-destroying chlorine free radicals.
Examples of photodissociation in the interstellar medium are (hν is the energy of a single photon of frequency ν): Currently, orbiting satellites detect an average of about one gamma-ray burst (GRB) per day.
The absorption of radiation in the atmosphere would cause photodissociation of nitrogen, generating nitric oxide that would act as a catalyst to destroy ozone.
[22] The atmospheric photodissociation would yield (incomplete) According to a 2004 study, a GRB at a distance of about a kiloparsec could destroy up to half of Earth's ozone layer; the direct UV irradiation from the burst combined with additional solar UV radiation passing through the diminished ozone layer could then have potentially significant impacts on the food chain and potentially trigger a mass extinction.
There are strong indications that long gamma-ray bursts preferentially or exclusively occur in regions of low metallicity.
Thus, depending on their local rate and beaming properties, the possibility for a nearby event to have had a large impact on Earth at some point in geological time may still be significant.
However, after absorption of multiple infrared photons a molecule may gain internal energy to overcome its barrier for dissociation.