54 



about 10 ev and its de Broglie wave length is about the size of a water molecule, 

 but before the electron drops to thermal energy, its de Broglie wave length cov- 

 ers several molecules. Actually the electron is colliding with several mole- 

 cules at once, and so a condensed gas model with a constant mean free path 

 doesn't have any particular meaning. 



FANO: With regard to the Bailey-Duncanson work, the cross section of the 

 gas phase water molecule, is going to be much larger than geometrical because 

 of the dipole, and that shortens the mean free path. 



MAGEE: You think the cross section of the gas phase is much bigger than 

 it would be in the liquid? Is that the idea? 



FANO: Yes. 



MAGEE: Of course, there are any number of reasons one cannot believe a 

 calculation such as Samuel and I made. However, the result came as a sur- 

 prise to me, so I began looking around for other evidence which bears in one 

 way or another on this result. I would not believe such a calculation on its own 

 merits. In fact, I don't know how to make a calculation I would believe. I think 

 I would agree with Dr. Platzman that you can only calculate the order of magni- 

 tude. He obtained 50 A which, incidentally, was a confirmation of capture, be- 

 cause at that point the electron had already been thermalized, but the coulomb 

 field was over twice as great as kT and the electron in about 10" 12 of a second 

 would get back due to the influence of the field. 



PLATZMAN: It is only fair to say, however, that we disagree on that. 



MAGEE: All right. 



PLATZMAN: Dr. Magee has made a definite theory based on a certain 

 model, and we should understand two things: first, how his theory develops 

 from the model, and, secondly, the foundation of the model, keeping the two 

 separate. 



MAGEE: I should like to emphasize that this calculation is of interest as a 

 classical limit. One calculates limits to get ideas, and of course, may come 

 out with the correct order of magnitude. 



BURTON: What is important in this model is the fraction of energy trans- 

 ferred on each collision. That is very important. 



MAGEE: There is another factor, the main free path between collisions, 

 and that is the thing which could get the electron to large distances. If there is 

 a big main free path, the electron will get away. 



ONSAGER: May I ask a question? What radial distribution do you and 

 Samuel compute for the thermalized electrons? 



MAGEE: Our calculation is not that elegant. We only calculated for an 

 electron which had an average value of r2. It is a very crude calculation, but 

 it does indicate the classical result. It is the one line of evidence which first 

 led us to believe that there was a possibility that the parent ion could do captur- 

 ing, due to the fact that there are very strong inelastic collisions and excitation 

 of thermal motions. I would certainly not say that this calculation would indi- 

 cate that this process is the actual one which happens. As I said before, at first 

 I am trying to put together a picture as furnished from a number of lines of evi- 



