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XXXVI. Preliminary Note on the Stark Effect of the 4686 

 Spectrum Line. Bij E. J. Evans, D.Sc. (Lecturer in 

 Physics, Manchester University), and 0. Croxson, B.Sc* 



[Plate V.] 



THE effect of an electric field on spectrum lines which 

 was discovered by Stark f is obviously closely connected 

 with the structure of the atom, and it was with the object of 

 further testing existing theories as to the origin of the 4686 

 spectrum line that this research was undertaken. The Stark 

 effect in the case of hydrogen was examined from the 

 theoretical standpoint by Warburg J, and also by Bohr §, 

 who based their work on the view put forward by Sir E. 

 Rutherford that the hydrogen atom consisted of a single 

 electron revolving round a positive nucleus. Bohr deduced 

 that in an electric field each of the hydrogen lines of the 

 Baliner series should consist of two components polarized 

 parallel to the field, and showed that Stark's results for the 

 separation of the two strong outer components polarized 

 parallel to the field for the first five lines of the Balmer series 

 agreed approximately with the values calculated from his 

 theory. Further, in the case of an electron of charge e 

 revolving round a nucleus charge N<? in an electric field of 

 strength E, he deduced the following expression for the 

 frequency difference Av between the two outer components 



^=A^-w-»i 2 ), .... a) 



where h and m are Planck's constant and mass of electron, 

 and n 2 and n x are the numbers representing the position of 

 the spectrum line in a series of the type 



'-**[■;?-;?]' 



where K is the By d berg constant. 



Stark's experiments had shown that the effect of an 

 electric field was far more complicated than the deductions 

 from the simple theory mentioned above, and this complexity 

 was emphasized in connexion with theories on the structure 

 of the atom. Recently, however, Bohr's theory has been 



* Communicated by Sir E. Rutherford, F.R.S. 



t Electrische Spektralanalyse Chemischer Atome, by J.Stark (Leipzig 1 , 

 S. Hirzel, 1914). 



X Warburg, VerhandL d. Beutsch. Pht/s. Ges. xv. p. 1259 (1913). 

 § Bohr, Phil. Mag. xxvii. p. 506 (1914) ; xxx. p. 404 (1915). 



