60 . YOS, BADE AND JEHLE 



some very special effects in ordinary van der Waals forces, if the matrix ele- 

 ments of the dipole moment correspond to charge separations which are com- 

 parable with the distance of separation of the macromolecules. 



Professor Jehle: With respect to the first part of your remarks I should 

 like to say that ultraviolet electronic transitions naturally play a very impor- 

 tant role in the specificity of London forces. If, in addition, there should be low 

 frequency electronic transitions, this would be interesting, presumably they 

 would have strong polarizabilities. And it will be important to know whether 

 or not there are excited electronic states (which usually have strong polariza- 

 bilities) which are in thermal reach. 



With regard to the second part of your remarks, referring to the Casimir 

 corrections, it is to be expected that these are negligible in the case of compact 

 macromolecules of about 50 Angstrom diameter — because the range of their 

 specific interaction might be of the order of at most a few times that diameter, 

 which is small compared with the vacuum wavelength of the highest frequency 

 electronic transitions. 



I agree with Dr. Kirkwood's last remark. As we have pointed out, the pro- 

 cedure of taking only dipole terms in the expansion is just a very handy, use- 

 ful approximation which greatly simplifies the problem. 



As to the preceding questions relative to the magnitude of the polarizabili- 

 ties, we felt that the reasonable approach to this problem of the relevance of 

 the specificity of the London force is to answer first of all the question, "For 

 what kinds of oscillator polarizabilities and for which molecular structures and 

 for what kinds of detunings, is the discriminating effect of the London interaction 

 strong enough, at a given separation R, to understand biological specificities on 

 the basis of London force." 



