520 Dr. N. Bohr on the Effect of 



by a corresponding loss of potential energy of the whole 

 system relative to the field. 



In order, therefore, to obtain the connexion with the 

 ordinary mechanics and at the same time to be in agreement 

 with experiment *, we are led to assume that the effect of a 

 magnetic field on the stationary states of the hydrogen atom 

 consists simply in a superposed rotation of frequency t round 

 the axis of the field, and that the radiation emitted by the trans- 

 ition between two stationary states is changed by the field so 

 as to have the polarization and frequencies of a Zeeman triplet. 

 It will be seen that this assumption is equivalent to supposing 

 that the energy of the hydrogen atom in its stationary states 

 is not altered by the presence of the field, but that the relation 

 (1) in case of vibrations perpendicular to the field is replaced 

 by the relation 



^-A^/^ + t) (24) 



The essential difference between these assumptions and those 

 employed in explaining the effect of an electric field will be 

 noticed f. 



From the analogy between the explanation of the hydrogen 

 spectrum and that of spectral series of other elements given 

 in the first section, we may naturally assume that similar 

 assumptions will hold for the stationary states of other atoms. 

 A possible explanation on this basis of the complex Zeeman 

 effect of double lines will be indicated in the next section. 



§ 4. Doable Spectral Lines. 



According to the considerations used in sections 1 and 2, 

 each series of lines in the spectrum of an element corresponds 

 to a series of stationary states of the atom, in which one of 

 the electrons moves outside the others. The configuration 

 of the inner electrons is assumed to be very nearly the same 

 in each series, while that of the outer electron changes from 



* See Fr. Croze, Journ. de Phi/s. iii. p. 882 (1013). 



t Note added during the proof. — In Phj/s. Zeitschr. of Feb. 15, 

 K. Herzfeld 1ms discussed in detail the different possibilities of the effect 

 of a magnetic field which might be expected on the theory of the 

 hydrogen spectrum proposed by the writer. His conclusions are equiva- 

 lent with those obtained above. In addition he considers the effect of 

 terms proportional to the square of the magnetic force and shows that 

 in a strong magnetic field these terms may be expected to have an 

 appreciable influence on the magnetic resolution of the hydrogen lines 

 corresponding to high numbers in the Balmer series. This is a con- 

 sequence of the large orbits of the electron in the stationary states 

 corresponding to high values of n. 



