14 



cule. The process is photon free, due to the direct electrodynamic 

 coupling of the two molecules. 



Transfer of £* through electrodynamic coupling can occur not 

 only between identical molecules, but also between molecules of 

 different substances. The situation for such a transfer will be the 

 most favorable if there is a wide overlap between the fluorescent 

 spectrum of molecule A with the absorption spectrum of molecule 

 B, which has to take £* over. Apart from the "overlap integral," 

 the lifetime of A* and the wavelength influence the result. The 

 distance through which such energy transmission can take place 

 depends on these factors. 



Such an energy transfer in biological systems has actually been 

 shown to exist. Arnold and Oppenheimer found that the energy 

 of the light absorbed in green algae by phycocyanin is transmitted | 

 through such electrodynamic coupling to the chlorophyll with a | 

 high efficiency. The chlorophyll, in its turn, transmits it to thej 

 rest of the photosynthetic apparatus which builds carbohydrate •■ 

 with it, transforming E* into (E). A similar energy transfer has 

 also been found by Duysens from carotenoids to chlorophyll b in 

 blue and red alga and from chlorophyll b to a in the green alga 

 Chlorella. 



ENERGY BANDS. THE "CONTINUUM THEORY'^ 



If a physical system has a great regularity in the arrangement of 

 its atoms (as is the case in crystals, or might be the case in pro- 

 teins), then the atoms disturb one another's orbitals, the energy 

 levels of which may fuse into a common, practically continuous 

 energy band. If such a band is filled, that is, contains the maximal 

 number of electrons allowed {2n\i n is the number of atoms ) , then 

 no energy can be transported by its electrons. If, however, the band 

 is not filled, then its electrons can be accelerated in a definite 

 direction and can transport energy. This is how metals conduct 

 electricity. 



If a substance has completely filled bands and above them 



