45 



KASHA: No, other people used electrons. Lewis and Lipkin used light. 



BURTON: Who are the other people who used electrons? 



KASHA: Goldstein (16), I believe. It is very old work. 



BURTON: They irradiated dyes in glasses with electrons? 



KASHA: They irradiated molecular cystals of , not dyes, but somewhat 

 simpler molecules. All of these people have found that induced colors are de- 

 stroyed upon warming, and it turned out that the induced color is spectroscopi- 

 cally identical with the ion which you would produce from the substance electro- 

 chemically. So that the identification of the positive ion which may be made was 

 complete and the only missing point was the electron, that is, its condition in 

 the rigid system. 



ALLEN: Was the observed spectrum of positive ions? 



KASHA: Both are found actually, but in general the spectrum one finds is 

 that of the positive ion. This involves details which I think will be brought out 

 tomorrow. 



LINSCHITZ: After ionization, due to high-energy radiation, a positively 

 charged radical ion might lose a proton in an ordinary acidbase type ionization. 

 Whether or not the residual radical has a charge would have a bearing only on the 

 rate of recombination of the radical with the solvated electron that has been 

 knocked out. So that in this instance it is relevant to what you might call the 

 lifetime of the solvated charge. 



BURTON: This is a crystal system? 



LINSCHITZ: The systems in which these processes have been studied so 

 far are glasses. In general such solvents are polar and vacancies exist in which 

 electrons can be trapped. Let's leave out the mechanism of trapping the elec- 

 tron. When you do trap the electron you are bound to leave a positive ion, and 

 under such circumstances it will have a characteristic color as will the trapped 

 electron. 



KASHA: It is found that which solvent is used is rather crucial. In other 

 words, if it is a hydroxy lie solvent, then these photo-oxidations, as they are 

 called, proceed readily, but if it is a purely hydro-carbon solvent -- both of 

 these experiments are rigid glass solutions at very low temperatures -- the 

 purely hydrocarbon solvent does not show this phenomenon. That is, it does not 

 apparently provide a site for the electron, and frequently photo-oxidation does 

 not take place. 



ONSAGER: With carotenoids as solvents? 



LINSCHITZ: Do you mean as the trapping agent? 



ONSAGER: Yes. It would also be a good source, because I believe they 

 should be more readily ionized. 



KASHA: It has been tried with nitrogen compounds like diphenylamine. Di- 

 phenylamine in a hydrocarbon solvent does not lose its electron readily, while 

 diphenylamine in hydroxylic solvents does. 



