176 PENETRATION PHENOMENA IN LIQUID WATER 



however, we have a process corresponding to only the "glancing" collisions of 

 the theory of stopping. This suggests that a fruitful experiment might be a com- 

 parison of the spectroscopic ultraviolet oscillator strengths of liquid and vapor 

 water. To be of maximal value such a comparison would have to be extended 

 to as short a wave length as possible — perhaps even down to 200 A. Such 

 oscillator strengths would in any case represent information of the greatest 

 radiobiological value. 



Platzman (Communicated) : 



The spectroscopic information on water which Appleyard requests would 

 certainly be of the greatest interest. Indeed, the corresponding information for 

 any substance would be invaluable for the understanding of its stopping power. 

 Such information is, however, not available. Nor is it likely to be readily forth- 

 coming; it requires investigation in one of the most difficult of wave-length re- 

 gions, and, moreover, demands absolute intensity determinations. But this 

 statement should not be taken to imply that the experimental problem is hope- 

 less. In fact, an attractive preliminary approach would be simply the comparison 

 of the continuous absorption spectra of liquid and vapor water in the accessible 

 Schumann ultraviolet. 



Lind; 



It is evident, I think, from the papers and the discussion today that more 

 information on the effects of ionizing radiation in liquids, both aqueous and 

 non-aqueous, is very much needed before we will be able to think in a general 

 way about the effects of ionizing radiations in the non-gaseous state. 



