105 



BURTON: There is something we must be very careful about, and that is 

 an exaggerated emphasis on ionization. In this case we say the ion lasts a 

 short time. However, we must never forget that there is simultaneously pro- 

 duced, at similar concentration, some molecules in lower excited states. 

 These lower excited states have not been ruled out as not making a contribution. 

 We want to bear in mind that we may yet have to modify the theory of the radi- 

 ation chemistry of water very drastically to include such lower excited states. 



The question is whether these lower excited states may enter into some- 

 thing new and may give an entirely different type of reaction. My feeling is 

 that it is better to think of the energy distributed among the free radicals as 

 kinetic energy of the free radicals and to think separtely about the residual en- 

 ergy in the water molecule which does not happen to dissociate. 



You remember we have mentioned here the possibility that at these high 

 densities of excitation there may be interaction between excited molecules. 

 Two excited molecules may come together. You see, Dr. Allen was very care- 

 ful when he outlined his presentation of the radiation chemistry of water (Z). 

 He spoke of the forward reaction as opposed to the radical reaction. He did 

 not say that the forward reaction was not a radical reaction. He said this is 

 all we observe. We must remember that there may be something in addition 

 to radical reaction. 



KAMEN: In talking about ions and radical pairs we are speaking only about 

 water, and I want to emphasize that the present discussions cover only the case 

 of water. 



ZIRKLE: While we are still on water, did I understand you to say that 

 peroxide is not of great importance? 



KAMEN: I was saying that the concentration in which the peroxide is pro- 

 duced would not be important as compared with the radicals. Peroxide should 

 not initiate a chain reaction in the concentration we encounter in clusters. It is 

 going to be the OH that does. 



FANO: I should like to ask a question at this point. If you have an excited 

 water molecule which dissociates, would anybody care to make a statement as 

 to the likely method? How far are the two radicals projected before they start 

 diffusing? Would they go less than the molecular diameter or much more? If 

 two parts break off like this how far do they go before the momentum is dis- 

 sipated? 



KAMEN: How big a molecule do you want? 



FANO: H 2 0. 



PLATZMAN: About two molecular diameters. 



FANO: That is, more than 1 and less than 10. 



MAGEE: It has been demonstrated by tracer experiments (3) that H atoms 

 which have a kinetic energy of 1-2 ev can escape 100 per cent of the time from 

 the point of formation. 



BURTON: But the H atom is a special case. 



PLATZMAN: Water has an especially open structure, so that H atoms can 



