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 lines 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 

 /3 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, 1917. The equation v = i> (N - 3.5)2 where v is Rydberg's fundamental 

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

 considerable accuracy. The nuclear charge is obtained by Q = 2e(N - 3.5). 



SMITHSONIAN TABLES. 



