31 



ONSAGER: It would require the dielectric relaxation time. 



PLATZMAN: Yes, a minimum of that. 



ONSAGER: It might be a little slower perhaps. 



PLATZMAN: You see, the electron is moving. 



ONSAGER: On the other hand, you have the mobility of the hydrogen ion, 

 and that conforms about to the dielectric relaxation time anyway. 



PLATZMAN: Well, it is probably of that order of magnitude. At least, it 

 is much longer than the moderation time. It makes a delay in the chemical ef- 

 fect. A very pronounced delay. 



BURTON: If this is inappropriate at this time just tell me. What about the 

 process of the electron being captured by a hydrogen ion in the water? Have 

 you thought about that? 



PLATZMAN: No. Not yet. The studies which I have been describing are 

 far from complete. 



ONSAGER: As a matter of fact, this reaction goes even in ammonia. The 

 reaction of the capture of electrons. 



PLATZMAN: I was going to come to that in just a moment. I still have not 

 suggested how the prior orientation of the dipoles will contribute the required 

 energy. Ordinarily, if a charge is inserted into the dielectric, and the dipoles 

 orient, the energy goes into heat: it is dispersed and lost. 



First, however, I should like to take just a moment to explain to you how 

 one can probably account for the properties of the "free" electrons in liquid 

 ammonia^. This is a familiar system in inorganic chemistry. It is known that 

 if alkali metals are dissolved in liquid ammonia, the solution develops an in- 

 tense blue color and has a number of other striking properties. The interpre- 

 tation is essentially this. Consider liquid water or ammonia. First of all, for 

 the moment, ignore completely the possibility of chemical reaction. Take a 

 charge and insert it at some position in the dielectric and see what happens. 

 Obviously, the dipoles in the neighborhood will rotate. If we then remove the 

 charge very quickly there will be left a region in which the electric potential has 

 the shape of a potential well. It is easy to show that such an arrangement of 

 dipoles will bind an electron in a number of quantized orbits. If the energy of 

 the first excited state is calculated, the difference between it and the ground- 

 state energy is that of the transition responsible for the blue color. This checks 

 very well with experiment. In ammonia solvative capture is the only thing that 

 can happen, because all possible chemical reactions of the electron absorb en- 

 ergy; therefore, the electrons are chemically stable. The difference between 

 water and ammonia is simply that a chemical reaction of the electron, with neg- 

 ative AF, is possible in water. Solutions of these electrons in ammonia are 

 therefore very stable if the ammonia is pure. Usually, however, it is found that 

 they decompose over a period of weeks. 



2. The discussion in this paragraph is based on an unpublished paper by 

 the speaker. R. L.P. 



