34 



long wavelengths. You can kick electrons out into the vapor phase with a very 

 modest amount of energy. 



BURTON: The trapped electrons? 



ONSAGER: Yes, and I think there are absorption spectra here in the infra- 

 red. 



PLATZMAN: That is correct. The theory I mentioned agrees with this. 



KASHA: Does it account for the broadness of the bands? 



PLATZMAN: I don't yet know. 



ONSAGER: As regards the picture itself, I think there is one point that is 

 not brought out. You might have intended to bring it out and forgot about it. It 

 is that the hole the electron makes for itself is pretty big. As regards the size 

 of the hole, opinions have been varied. DeWall spent last year with us. I be- 

 lieve he looked into the question rather critically and he thought that 70 cubic 

 centimeters per mole was about right at low concentrations. It is certainly at 

 least 40. On the other hand, not nearly as big as suggested by Ogg many years 

 ago, although Ogg does have credit for some perfectly good experiments (12). 



PLATZMAN: Let us now proceed with the "life-history" of the secondary 

 electron. Since the dissociative attachment is impossible for a free electron, 

 it must wander around until it becomes hydrated. We can assume that in this 

 state it is very similar in properties to the blue electrons of ammonia, because 

 the dipolar and dielectric properties of water and ammonia are very similar. 

 Now, if dissociative attachment to one of the water molecules about which the 

 electron is spread occurs, there is made available the increase in energy with 

 respect to the polarized dielectric corresponding to the electron "collapsing" 

 about an OH radical. This provides the necessary 2 or 3 ev. In another sense, 

 the electron moving in the field of the dipoles has a great deal of kinetic ener- 

 gy; when it is attached to the radical it does not have to have that and regains 

 the entire potential energy at or near the bottom of the potential well. This is 

 one of the major points that I should like to make this afternoon. 



MAGEE: Have you essentially completed your picture? Could you summa- 

 rize and give us a complete picture, especially of where these things happen? 



PLATZMAN: Let me review it briefly. I will start back at the point where 

 we found that the 10-volt electron takes about 10"13 second to be thermalized. 

 In this time it goes about 10^ A, and, on the average, its actual final separation 

 from the positive ion is about 50 A, both of these being minimum estimates -- 

 this, however, neglecting the factor of the electric field of the positive ion, which 

 which would reduce them. Having attained thermal energy, the electron finds it 

 impossible to carry out the chemical reaction which is written in all the articles 

 on radiation chemistry, just because of the disparity between the time the actual 

 reaction takes and the time which would be required for it to utilize the hydra- 

 tion energy which makes it possible. For this reason the electron becomes hy- 

 drated. One must, of course, be very cautious about using the word "hydrated" 

 because it means so many different things to different people. I mean here that 

 the electron polarizes the dielectric and is bound in a stable quantum state to it. 

 Then, finally, the chemical reaction can proceed as I have suggested, and the 

 OH" ion and H atom are formed. In between there is the time for the hydration 

 to take place, which must, as Dr. Onsager said, be a minimum of the relaxation 



