112 



LINSCHITZ: I should like to comment on this. The actual time required to 

 bleed the energy away from a given site is clearly very sensitive to the degree of 

 coupling of the original site with the rest of the system. Suppose that a given 

 bond or group is initially excited electronically. This may occur, for example, 

 in a single carbonyl group of a ketone, or the benzene ring in an aromatic com- 

 pound, in which the electronic excitation is well localized. Upon internal con- 

 version, this energy is changed to vibration which initially is also localized. 

 Bonds immediately adjacent, and strongly coupled, to this site will be violently 

 strained, and if such bonds, directly in the path of energy degradation, happen 

 to be much weaker than those in which the vibrational energy is first released, 

 the chance of rupture may be quite high. Bond breakage caused by such a specif- 

 ic process, in which the necessary energy is initially locally available, is hard- 

 ly comparable to the corresponding thermal event. In this connection I would 

 like to cite once again the early work on monolayers of stearic acid anilide, in 

 which electronic excitation of the aromatic component of the molecule led to 

 hydrolysis of the peptide link, with quantum yields of 0.2 or possibly even high- 

 er. Very little is known of the systematics of such energy migration and degra- 

 tion, and more experiments on model compounds would be most useful. 



FANO: Maybe it might be a good thing to avoid the confusion that is arising 

 now by refraining from referring to vibrational energy as heat. 



PLATZMAN: The difficulty is that, practically, there are no other words. 

 I think that what Dr. Pollard said is very important and without question it is 

 right; that is, you always do get some "heat", "prepartitioned", and, therefore, 

 "local heating" undoubtedly modifies the action of everything we have been talk- 

 ing about the past two days. It isn't either/or. It is always both and you cannot 

 have one without the other. 



FANO: It is not heat. 



PLATZMAN: I agree. But can you find another word to describe it? 



FANO: Call it excitation of vibration. 



PLATZMAN: This is a diffuse but highly non-equilibrium vibrational ex- 

 citation of (part of) a large polyatomic system. I have a good deal of respect for 

 the word "heat". But we don't have a word for the other, and "heat" is not a 

 bad approximation until we do have, provided that it is properly understood as 

 Dr. Pollard stated it. 



POLLARD: I should like to state a little different point on the monolayers. 

 Smith, in our group, has been doing some work on catalase. It is not yet com- 

 plete and I do feel that in deference to him we should not say too much about it. 

 But briefly it is this: He slipped lucite in and out of a trough that had a mono- 

 layer of catalase on it. This, of course, gave a monolayer on the lucite. Then 

 he exposed it to the action of X rays and water as pure as he could get. To his 

 surprise very high amounts of radiation were necessary before any inactivation 

 could be observed. Perhaps 100, 000 r produced no effect. He now has an ef- 

 fect. After something like 350,000 r the effect is of the order of 50 per cent. 



If the experiment is right, the interest in it is that the lifetime of whatever 

 is produced in the action turns out to be probably less than 10~4 seconds. By 

 this means one can get some sort of estimate. This isn't the final word. It was 

 not especially compressed film. No particular monolayer technique was used. 

 It was just an ordinary film of catalase on a Langmuir trough and dipping was 

 done twice, I believe. 



