the Absorption of X-Rays. 187 



The designation /c a /c u below stands for the relative values 

 of the atomic absorption coefficients, which have been cor- 

 rected for scattering*. The correction, however, is of no 

 significance in heavier elements, and in elements of higher 

 atomic number than 23 fc a /C\i * s therefore assumed to be 

 equal to tf a /c u « 



As pointed out above, according to the theory on 



scattering of J. J. Thomson, every one of the outer electrons 



must have an equal influence. If we approve of the common 



view that the hydrogen atom consists of a nucleus combined 



only with one electron, we can readily find the value of the 



scattering effect (q) excited by one single electron. Without 



any noteworthy error we may assume that in the formula (5) 



k 

 Y^~ may be put equal to zero for H. Thus the absorption 



of the hydrogen atom would entirely be determined by the 

 scattering effect produced by the electron combined with 

 the nucleus. In the case of the four different compositions 

 of radiation used in my experiments, the absorption co- 

 efficient depending on an outer electron in relation to the 

 atomic coefficient of copper will thenee give the following 

 values : — 



I. II. III. IV. 



q = 0-067 0*090 0-136 0*195 



Supposing the number of the outer electrons (p) to 

 be known, the correction for scattering, after what ha& 

 been said above, will simply be pq. 



If Li is regarded as being built up of 3, Be of 4, and B 

 of 5 electrons, then the corrected values (/e a /cu) f° r these 

 elements will be obtained by deducting 3q, Aq, hq respec- 

 tively from the observed values. These values are, as seen 

 from Table VIII., fairly constant, except for Be Iv . An 

 experimental error might be responsible for this differ- 

 ence — a circumstance which is easily accounted for, partly 

 by the difficulty in accurately determining absorption in 

 case of the slightly absorbing lightest elements, partly by 

 the above-mentioned difficulty in keeping radiation un- 

 changed when using the hardest rays. 



As for C, the simplest thing would evidently be to regard 

 all of the 6 electrons to be arranged as outer electrons ; 

 but if the values found of tc G/0 are corrected by 6q, we get: 



I. II. III. IV. 



*c/Cu- 6 ? = °' 186 0>183 °' 080 -0-069, 



* Corap. Glocker, Phys. Z. xix. p. 68 (1918). 



