﻿850 Mr. J. H. Van Vleck on the normal Helium Atom 



The writer has not been able to find any theoretical basis for 

 these empirical rules, and they appear rather hard to reconcile 

 with the Bohr Analogy Principle, but it should be remembered 

 that the type of dynamical system to which they are applied 

 is somewhat different from that met with in the hydrogen 

 atom, where (with neglect of relativity correction) the action 

 integral can only be an integral multiple of h *. Also the 

 atomic models to which these empirical rules appear applic- 

 able are those whose physical properties seem to be in best 

 agreement with experiment. This is especially true as 

 regards the semicircular model of the hydrogen molecule, 

 while the case of the helium atom will be discussed on 

 later pages. The moment of inertia of the semicircular 

 model of the hydrogen molecule agrees well with the value 

 found from band spectra, while its zero angular momentum 

 about the axis of symmetry is in accordance with specific 

 heat theory, the diamagnetism of hydrogen, and the behaviour 

 of the many-lined hydrogen spectrum in a magnetic field f. 

 No other model has been proposed which possesses these 

 properties. 



Modification of Law of Force between Negative Electrons. 



In the absence of any thoroughly satisfactory attempt at 

 reformulating the quantum conditions, we must consider as 

 an alternative the modification of the law of force between 

 negative electrons at atomic distances. Any alteration of 

 the law of force between negative electrons and positive 

 nuclei (such, for instance, as would result from a highly 

 aspherical nucleus) would probably invalidate the Bohr 

 theory of the hydrogen atom and contradict the experimental 

 evidence of Rutherford on the validity of the inverse square 

 law, but his work yields no information on the forces 

 between two negative electrons {. On the other hand, 

 A. H. Compton concludes that the spiral tracts of beta 

 particles indicate that the field of an electron does not have the 



* Of. remark by Bohr : " Diese Storungen (i. e., mutual action between 

 electrons) geben namlich fur die beiden Partikeln des Heliumatoms zur 

 Bewegungen Anlass, deren Charakter sich als iiberaus verwickelt erweist, 

 und zwar so, dass die stationaren Zustande nicht festgesetzt werden 

 konnen in direkter Anlehnung an die Metlioden die fur bedingt 

 periodische Systeme eutwickelt worden sind " (Zeits.fiir Physik, Band 2, 

 Heft 5, p. 465). 



t Cf. Langmuir, Science, vol. lii. p. 434, Physical Review, vol. xvii. 

 p. 339. 



X In a very recent paper (Proc. Roy. Soc, Feb. 19:32), Orowther and 



Schonland, however, conclude that some modification of law of force at 



very small distances, either between two negative electrons or an 



lectron and a nucleus, appears to be demanded by their experiments on 



e he scattering of beta ^articles. ■ 



