13 



Type of 

 Element Compound 



Carbon Saturated 



Unsaturated 

 Highly chlorinated 



Nitrogen Amines, nitrates, etc. 



Nitrogen in ring 



Oxygen -O- 



o= 



Chlorine All 



ALLEN: We would like to know the energy distribution of primary events. 

 I made some attempt to look this up a couple of years ago, and had to go back 

 to the C.T.R. Wilson cloud chamber pictures of 1923. I wonder if anything has 

 appeared since. 



PLATZMAN: Dr. Fano has tried to find the energy distribution of the sec- 

 ondary events. I am sure that he will agree with me when I say that this is one 

 of the things of which we are most in need. 



FANO: It is a difficult problem. 



PLATZMAN: This would be a very fine experimental project for the sub- 

 committee to stimulate, because the work could be done, and physicists are in- 

 terested in it. The same holds for the theory. 



FANO: We would have liked to have done it, but our initial attempts indicat- 

 ed that the problem was much more difficult then we originally believed. 



POLLARD: This is actually really quite important in radiobiology because 

 we are now turning up effects in which there is a threshold energy. For in- 

 stance, if a deuteron beam passes through a virus, it looks as though a certain 

 energy has to be released in the virus to inactivate it. There is some evidence 

 in the case of Flexner's toxin that this is so and possibly also in the case of 

 respiratory enzymes. Unless you know the number and energy of the secondary 

 electrons produced, you cannot compute this thing numerically. There is an 

 important third datum, so to speak, you have to have. 



Then there is the opposite extreme of this: when you get highly sensitive 

 conditions of a molecule, which can happen, you need to know the number of 

 excitations, because then the photon sensitivity may become high. If there is 

 a high proportion of excitation to ionization, it may produce a notable effect, 

 which will not be quite different because it will not necessarily require the 

 ionizing radiation to pass through the molecule, since the photon travels over a 

 corresponding distance and it may be further away, while the ion is localized. 



TOBIAS: Has anyone in Jesse's group worked on water vapor? 



PLATZMAN: No, although he is considering it. The only modern measure- 

 ment of ionization in water vapor is that by Appleyard (27). It is not easy to do 

 and I don't think it is terribly important; as a matter of fact, it might even be 

 a misfortune if somebody measured W very accurately because then immediately 

 most biologists would assume that liquid water would behave the same. 



