Photosynthetic water splitting (or oxygen evolution) is one of the most important reactions on the planet, since it is the source of nearly all the atmosphere's oxygen [â€¦] The mechanism of water oxidation is still not fully elucidated, but we know many details about this process.â€ś
Source : Wikipedia
After many decades of research, much of the fine-detail of the highly complex photosynthesis (PS) process is now understood. It's now known, for example, that four photons are required to initiate PS, and that it takes only a millisecond or so to split water to produce oxygen as a by-product. (For complex technical details, see the two Nature papers linked below.)
Several crucial steps, however, remain undescribed.
Current research suggests that the oxygen moves through stages which include a complex peroxide - but the exact details are still not known :
The onset of O2 evolution, as indicated by the shortening of the Mn1â€“Mn4 distance, occurs at around 1,200 ÎĽs, signifying the presence of a reduced intermediate, possibly a bound peroxide.â€ť
Source : Structural evidence for intermediates during O2 formation in photosystem IINature, May 2023
For further extensive technical details see : The electronâ€“proton bottleneck of photosynthetic oxygen evolutionNature, May 2023
The efficiency of photosynthesis (PS) is thought to be very close to 100% (exceptionally high for any complex system) which has led some researchers to suggest that quantum 'superposition' effects and/or may be in operation with respect to the way that photons are somehow channeled towards the most efficient pathways within the light-harvesting complexes. These theories have not yet been generally accepted.
Example research paper :
Photosynthetic organisms capture visible light in their light-harvesting complex and transfer the excitation energy to the reaction center which stores the energy from the photon in chemical bonds. This process occurs with nearly perfect efficiency.â€ś [â€¦] â€śThe high efficiency of this process is not yet understood today.â€ť
Source : Gain and loss in open quantum systems, Institute for Quantum Science and Engineering, Texas A&M University, and Max Planck Institute for the Physics of Complex Systems, 2017
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