608 Dr. Mamie Siegbahn on 









N. 



CI . 







17 



K ., 







19 



Ca. 







20 



Sc . 







21 



Cr. 







24 



Fe. 







26 



Co.. 







27 



Ni. 







28 



Cu. 







29 



The 



fine 



strut 



ture of 



A. 10 



-u cm. 



K a v 



K&. 



4718-70 



— 



373386 



344737 



335 1-86 



3087-89' 



302526 



2774-54 



2285-17 



2081-44 



1932-39 



1753-97 



1785-24 



1617-58 



1654-67 



— 



15o7'36 



1389-53 



•tare of the lines in the K-group. 



In an exceedingly interesting paper Sommerfekl * has 

 shown that the a-doublet of the K-group is to be ascribed to 

 the double character of the second electron ring of the Bohr- 

 Rutherford atom. in reality there are two possible ways 

 of distributing the two quanta assigned to the second ring, 

 which either gives a circular or an elliptical orbit with 

 definite excentricity, the mass of the electron being taken as 

 a constant. The replacing of the electron from the one or the 

 other of these orbits, to the first ring, then gives the a line 

 in two ways. When the variable mass of the electron is 

 taken into consideration there will come out two somewhat 

 different frequencies. As this difference can be theoretically 

 deduced it gives a very good opportunity to empirically 

 prove this hypothesis. 



The theoretical value given by Sommerfeld in his above- 

 mentioned paper is : 



. . . (1) 



where Av H is the analogous frequency- difference by 

 hydrogen in the optical spectrum, N is the atomic number,, 

 and a a constant : 



2_7re 2 

 ch 



The best value of Av a determined from the spectrum of 

 He by Paschenf in his beautiful research on the fine 

 structure of some He-lines is : 



* Sommerfeld, Ann. d. Phys. li. (1916). 

 t Paschen, Ann. d, Phys. 1. (1916). 



