39 



tions, impurities, etc. 



BURTON: Dr. Platzman, perhaps I should not say this but you still have a 

 time in there of the order of 10~10 second and you have a figure for the therma- 

 lized electron-parent ion separation of 10 to 50 A. Isn't another very important 

 competing process, that really can occur very well, the recombination with the 

 parent H20 + ion? 



PLATZMAN: No, I don't think so. 



ONSAGER: That can be analyzed. I think it might occur. It isn't too prob- 

 able. The chance of escape is simply the Boltzmann factor for the electron at 

 whatever distance it slows down to thermal velocities. 



LINSCHITZ: We have tried actually to measure the lifetime of the presumed 

 blue color in irradiated water, using pulsed X rays. The radiation was passed 

 transversely through a water cell 1 cm in diameter and 15 cm long, while we 

 looked down the tube with a monochromator and photocell. The X rays were 

 taken from a Westinghouse "Micronex" outfit, at about 150 kv, with a pulse du- 

 ration of about one microsecond. The dose-rate was something like 105 r per 

 second and with an oscilloscope we could measure the absorption up to within 

 10"5 seconds of the pulse. In no region of the visible spectrum could we see any 

 absorption that might correspond to electrons in water. 



PLATZMAN: Of course, the absorption would be continous throughout the 

 visible region, and would disappear in a time much shorter than lO -5 ' second. 



LINSCHITZ: It might be that again the total intensity was not quite enough. 

 I think we were just on the ragged edge. 



PLATZMAN: Tritium water provides another possibility for finding this ab- 

 sorption. 



POLLARD: I should like to speak before everybody else does. This is a 

 group which we might say is dedicated to the subject of water. I should like to 

 point out that your remarks are really a little broader in their implication. I 

 should also like to point out that a whole lot of biology does not involve water. 

 There is very little water inside a virus. The method of inactivation of the virus 

 by water-borne agents is clearly different from that which is observed in the 

 absence of water, or where water is kept to a minimum, and follows the line 

 which is more normally accepted biologically. There is every reason to believe 

 that there is a side of radiobiology which is not concerned with water at all but 

 which is concerned with radiation mechanisms involving protein and nucleic acid, 

 two quite interesting substances. What about your remarks? Suppose you did not 

 consider this as something with a molecular weight of 18? What would happen if 

 you considered this in a micro-crystal or a micro-molecule of protein or of nu- 

 cleic acid? To what extent would several of the factors you discussed matter? 



For instance, let's take the question of the force between the positive ion and 

 the electron. Has the infrared dielectric constant been taken as 5. 5 or is it less? 



PLATZMAN: We know this only for relatively few substances. The value for 

 H 2 0, namely about 5, is extraordinarily great. 



POLLARD: Yes, and it is likely to be considerably less. In that case, the 

 tendency in the solid would be toward recombination. 



