30 J. FRANCK 



more energy. It certainly is not the most economiccal way to do the process. He did 

 not deny electron transfer and he certainly believes in semiconductors. 



If you want to do this efficiently with chlorophyll molecules, as Dr. Ilabino- 

 witch pointed out, you also have to do some moving around and you cannot do 

 this in 10~i2 second. If you have lots of energy, if you use gamma rays, then you 

 can most likely- do it. With 30 electron volts per ion pair, you can do it that 

 fast. If you have 800 or 900 cal., you have plenty to work with. 



Rabinowitch : This ring V seems to be the key chemically, or maybe it is a sort 

 of general self-hypnosis we are indulging in, feeling that there must be something 

 in this ring which would explain the participation of chlorophyll in photosyn- 

 thesis. Anyhow, it seems also to be significant for the infrared absorption spectrum 

 of chlorophyll. All the changes and variations of chlorophyll which have been re- 

 vealed b}' the visible absorption spectrum also must find their counterpart in the 

 changes in the infrared spectrum. Dr. Holt is going to say something about the 

 infrared spectrum as a means to understanding this structure of chlorophyll and 

 particularly what happens in this one ring. 



