SOME CONTEMrOR.IRV .■IPr.lXCliS /.V I'llVSlCS-lll 



293 



potentials as corrcs[K)n(linjj to elevations of certain decp-K ini; clci - 

 Irons to transient-sojourn orl)iis. 



Some assistance in identifying the e\cilation-|)<)teniials of the iivjiit 

 atoms can he obtained by plotting the recognized excitation-potentials 

 of the heavier atoms, and also the fre(|ucncies of the ra\s excited; 

 plotting curves representing them as functions of atomic number; 

 and extra[M)laling the cur\es into the range of low atomic numbers. 

 Ihe l)est procetlure is to plot the square roots of the excitation-po- 

 tentials and the emission-frequencies, as then the curves are luarK 

 straight lines (Moseley's law). Some of iIhm' lines are shown in 



'it^rt-^ 



K^'' 



riTTfr 



i»— ' 

 in 60 — 

 c-l 

 S« 50 



Zr-iO, r~- 



-i — r- 



,1^' 



Ft— 



Tl- 

 U-IO 



c— 



F=. 



•''^■'\ \M: 







S i 



iiuuil*j« i 





Fig. 10 — Ciir\cs representing square roots of emission-frequencies of heavier atoms 

 as functions of atomic numlxjr. (Physical Revidv.) 



Hg. 10 itrom Kurih;. Since the atomic numbers are laid off (contrary 

 to usage) along the axis of ordinates, the lowest-lying line represents 

 the highest recognized emission-fretjuencies (the A'/3 and Ky fre- 

 quencies, which actually are slightly different, but are not indicated 

 separately upon the graph). The next line, marked Ka, represents 

 another particular emission-frequency. Excitation is the same for 

 every ray of this group, and consists in extracting one of the deepest- 

 lying or K electrons of the atom; and the excitation-jxjtential for the 



