1100 



Mr. D. Coster on the Spectra of X-rays 



diagrams were actually measured for the elements with 

 higher atomic numbers than xenon or krypton respectively. 

 The single exception is the line L/3 7 . Though there are 

 some indications that this line has been found for Ba and Cs, 

 its identification is not quite certain. An investigation of 

 the rare-earth metals, as yet unfinished, will possibly settle 

 the question. The lines « 1? a 2 > A and /3 2 of the K-series 

 have been measured by several authors for different elements 



& 



A 



tif 



Mr 



Ik- 

 Mr 

 Mr 

 Mr 



U 



Diagram III. — Krypton. 



r 



■a * i 

 -a. 4, 

 ■b 4, 



~6 3s 



r~rr 



I 



■a s, 



-6 3, 



» U ! II 



■ I I ! I I I ii 



Lil 



b %, 



J I ! Li 

 II 111 



^ H ll H 



-tf // 



in this region ; the line /3 3 , which lies at a very small wave- 

 length distance from /3 r , has been measured only for Eh, by 

 de Broglie, as stated above. The lines M7 and MS have only 

 been inserted in the xenon diagram for the sake of complete- 

 ness. They have only been found for the elements U, Th, 

 Bi, Pb, Au, and Pf* and they have not yet been studied 

 systematically. It will be very difficult to measure them in 

 this region, as even for Ba they should have wave-lengths of 

 about 13000 and 12000 X.TL respectively. The largest 

 wave-length hitherto measured with the aid of crystal re- 

 flexion is the line La for copper (13309 X.U.). 



* See Sten strom, Dissertation, Lund, 1919 ; Karcher, Phys. Rev. II. xv. 

 p. 285 (1920). These lines have been called Myi and My 2 by Karcher. 



