96 



Jesse, of course, measures both of them if they are both there. Our rough cal- 

 culation indicated that the total number of triplet metastables is of the order of 

 magnitude of several per cent of the total number of metastables. Most of the 

 metastables come from higher singlet excitations following radiation. Although 

 it is quite true that very slow electrons can excite triplet states, there are so 

 few of them with just the right energy and the excitation curve is so narrow that, 

 so to speak, they just hop right through. 



Of course, this is for the case of helium. I will not predict it to be a general 

 result. 



MAGEE: I think helium is a most unrepresentative case. 



PLATZMAN: I would be the last person in the world to say that helium is 

 typical, but with regard to the total number of triplets formed, relative to ions, 

 I doubt whether it is greatly different from other substances. But even our 

 crude calculation taught us that it is dangerous to guess about these matters. 



MAGEE: I think the molecular case is much more favorable for the forma- 

 tion of triplet states. There are more triplet than singlet states and they lie 

 lower, and so you will always have one triplet state or another you can excite. 

 In fact, for several volts below the lowest singlet excitation you will be able to 

 excite the lowest triplet state. I don't see how the helium calculation applies to 

 molecules. 



KASHA: I agree with what Dr. Magee said. All you have to do is get into 

 any triplet state at all. 



PLATZMAN: But the number of triplets formed directly will, I believe, be 

 small, because the excitation curve is so narrow. 



BURTON: However, if the exciting electrons have energy less than that re- 

 quired to excite the higher state, they then can excite only the low states. This 

 fact is of major importance for secondary electrons. 



KASHA: Can't they have 12 volts, 10 volts, 20 volts? Anywhere in that 

 range will excite the lowest triplet state that Dr. Linschitz was talking about. 



MAGEE: Even lower. Three, four or five volts. 



PLATZMAN: They have to have just about the right energy. That is the 

 trouble. 



MAGEE: I think you are over-estimating the sharpness of the resonance. 



PLATZMAN: I didn't estimate it. That is one thing that is known. I used 

 the actual cross sections. 



KASHA: I should like to spend a few minutes discussing a problem which is 

 always pictured as an extremely difficult one to consider: that of the potential 

 surfaces of a complex molecule in its various vibration and electronic states. 



One rapidly gets into hyper-geometrical space in such a discussion. How- 

 ever, by limiting the number of space parameters to three, namely two inter- 

 acting normal vibrations of the molecule, and third, the potential energy, a 

 rather illuminating picture can be drawn. I shall limit my remarks here to a 

 mere summary, for this discussion will be published shortly in full in another 



