Table 499. 

 X-RAY ABSORPTION SPECTRA AND ATOMIC NUMBERS- 



393 



A marked increase in the absorption of X-rays by a chemical element occurs at frequencies 

 close to those of the X-rays characteristic of that element. The absorption coefficient is much 

 greater on the short wave-length side. In the K series the a Unes are much stronger than the 

 corresponding /3 and 7 lines, but the wave-lengths of the a lines are greater. There is a marked 

 increase in the absorption at wave-lengths considerably shorter than the a lines and near the 

 /3 lines. Bragg came to the conclusion that the critical absorption frequency lay at or above 

 the 7 of the K series. The 7 line has a frequency about i per cent higher than the corresponding 

 ^ line. For the L series there are 3 characteristic marked absorption changes (de Broglie). 



The critical absorption wave-lengths of the following table are due to Blake and Duane, 

 Phys. Rev. 10, 697, 191 7. The equation v = Po{N - 3.5)^ where v is Rydberg's fundamental 

 frequency (109,675 x the velocity of hght) and N the atomic number, represents the data with 

 considerable accuracy. The nuclear charge is obtained by^=2e(iV-3.s). 



Smithsonian Tables. 



