Oxygen, chemical potential reduction

In Figure 1.8(b) the spectroscopic consequences of the heating in various chemical potentials of oxygen can be seen directly. The reduction causes a donor state band to... 

The essence of natural photosynthesis is the use of photochemical energy to split water and reduce CO2. Molecular oxygen is evolved in the reaction, although it appears at an earlier stage in the sequence of reactions than the reduction of carbon dioxide. Photochemical processes produce compounds of high chemical potential, which can drive a multistep synthetic sequence from CO2 to carbohydrate in a cyclic way. Reaction (16) is quite endoergic and thus thermodynamically very improbable in the dark (AG° = 522 kJ per mole of CO2 converted). Production of one molecule of oxygen and concomitant conversion of one molecule of carbon dioxide require the transfer of four electrons ... 

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