610 Dr. Mamie Siegbahn on 



N. A\ . 10-" Av. 



Fe 26 355 116 



Mn 25. 455 *126 



Cr 24 4-87 113 



The weakness of the lines makes an accurate measurement 

 very difficult. 



4. The Formula' of t Ik 1 Ka scries. 



Moseley, in his first paper on the X-ray spectra, suggested 

 the following formula to represent the K a. series : 



R = (N-l) 2 [j 8 -J] (1) 



where Xi is the Rydberg constant and N the atomic number of 

 the element. The theoretical basis which Moseley gave this 

 equation can no longer be maintained. The great import- 

 ance of this formula lies in the fact that Moseley introduced 

 the atomic numbers which have shown themselves to be so 

 fundamental for the X-ray spectra. 



The extension of the measurements has shown that 

 there are systematical deviations from this simple formula. 

 To find a better representation of the numerical results 

 Sommerfeld * suggested, in his first paper on this subject, the 

 formula 



v_(N-l-6)» (N-;W>) 2 



K~ P 2 2 • • • • W 



where the two terms, which constitute the spectral lines in the 

 Bohr theory, have their respective nucleus charges, N — 1*6 

 and N — 3*5. The values of these charges were determined 

 from the empirical data. With correction for the variability 

 of the electron-mass Sommerfeld deduced the formula 



R = S[\A- J(N-3-5)»-yi-«»(N=l-6)»], . (3) 

 * 2 = 5-3. 10" 5 . 



A considerable improvement was" made by Debye t> who 

 succeeded in giving a quantitative explanation of the 

 effective nucleus charges. His formula was 



g = I [4 v /l^« 2 (N^S 2 ) 2 .+ 2y / l- J(N-2) 2 



* Sommerfeld, loc. eit. 



t Debye, Phys. Zs. 1917, p. 276. 



