I know that energy transfers through the LHs to reach to the reaction center. But I want to know how this process can occur based on the quantum physics? In each step how does energy transfer (by using electrons and their excitations)?
Really this process is an ongoing research in the field of condensed matter, However some details has been revealed in green sulfur bacteria. Briefly between antenna (receptors of photon) and reaction center the FMO complex mediated the energy transfer. FMO complex contains three monomer each comprises of 7 chlorophyll (pigment) . Actually the energy transfer has been known as Exciton Energy Transfer (EET), where the absorbed photon results in an excited electron in monomer called Exciton, then this exciton energy transfers due to "quantum coherence" and exciton transfer chain, therefore exciton enters through 1,6 pigment and exit to reaction center through 3,4 pigments.(these numbers used to label each pigment in monomer). transferred energy by exciton, thereafter absorbs by the energy cycles in bacteria (or plants). The remaining part of energy transfer will take place in Calvin cycle where the absorbed energy consumes to split the water molecule to O2and CO2. the latter molecule results in carbohydrates with chemical energy. So the main part of the physics pertains to coherence and decoherence through the interaction with environments. This means that energy transfer is not exciton to exciton i.e. random walking, rather EET obeys the quantum walker, where energy diffuses through the system via the superposition of right and left directions with probable position at the border of system (reaction center).
The energy transfer between the antenna pigment molecules takes place through one more mechanism called Forster's Resonance Energy Transfer (FRET). It can take place between identical as well as different pigments exhibiting overlap integral. It also depends on the distance between 2 pigment molecules as well as on their orientation.
Please read the paper in New Journal of Physics 12 (2010) (Http://www.njp.org). More relevant for physics in quantum coherence.
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