93 



POLLARD: Have you looked at the measurements of Ruthemann and Lang 

 (22)? 



FANO: No. 



POLLARD: They are rather remarkable. Not many people know about 

 them. What they did was to take electrons of about 50,000 volts energy and they 

 fired them to go through collodion, beryllium, aluminum and aluminum oxide 

 films a few Angstroms thick, and then they bent them in a magnetic field and 

 measured what energy they lost. What they found was that they got a sharp max- 

 imum. Not too sharp, 15 to 25 volts, but very little below this. It goes smooth- 

 ly down and you are perfectly right. The experiments indicate that 5- volt veloc- 

 ities are relatively infrequent. So that it is actually apparently experimentally 

 all right, and collodion is not too far from a biological kind of material. 



BURTON: Of course, this comment applies to electrons of about 50, 000 

 volts. 



POLLARD: That is right. 



BURTON: In radiation chemistry a large fraction of the total effect is pro- 

 duced not by electrons of 50, 000 volts but by electrons of considerably lower 

 voltage. So we must ask: what about electrons around 150 volts? 



FANO: I would tend to be surprised on general grounds if it turned out that 

 a mechanism such as was discussed before was quantitatively important in the 

 action of ionizing radiation. Vice versa, it is perfectly obvious that such mech- 

 anisms are the most important things in normal biological events where high 

 energies are simply not available and the processes of life depend on visible 

 light. So for these things, it is obviously quite important. 



BURTON: In what I propose to say I may be extremely naive. But since I 

 admit it is naive, correct me. You know the Penning ionization gauge, in which 

 a gas at about 10~3 to 10-5 mm is present. A glow discharge can be caused to 

 pass through by the application of a crossed magnetic field. For such an ioniza- 

 tion gauge comparison of the current and the number of molecules that go 

 through indicates that all the molecules are ionized. I think that such a conclu- 

 sion is certainly correct within a factor of 2. At the same time, there is a very 

 bright glow. I have a feeling, derived from this calculation, that there is a 

 very high probability of production of the excited states which give this glow. 



Such a glow is seen with methane, benzene, and presumably with other 

 gases. 



FANO: It is probably due to transitions between highly excited states. 



BURTON: In the hydrogen discharge tube? 



FANO: Yes. I mean the transitions cannot be among the low lying levels. 

 Even in benzene the resonance transition does not radiate in the visible. 



BURTON: You mean the glow itself is an evidence of the fact that it is not 

 the low excited states that are being excited but the high excited states? 



FANO: Yes. 



KASHA: There is one thing that I disagree with, though, and that is Dr. 



