[ 497 ] 



LIII. On the High- Frequency Spectra {L-Series) of the 

 Elements Lutetium- Zinc. By Einar Friman, Dr. phil* 



[Plate XI.] 



IN a preceding paper f Dr. Siegbahn and the author have 

 given the results of an investigation of: the high-frequency 

 spectra (L-series") of the elements tantalum-uranium. In 

 this domain we found at least 11 line-groups. With the 

 vacuum spectrograph described in the previous paper (p. 494) 

 I have been able to continue these examinations down to 

 zinc (34 elements). Here I have reached a wave-length 

 of 12*346 . 10~ 8 cm. (La ] -line of zinc), while the greatest 

 wave-length measured by Moseley was 8*364. 10 -8 cm. (Ka- 

 line of aluminium). 



Most of the elements examined as compounds were finely 

 pulverized and rubbed on the anticathode, which was scratched 

 beforehand with a file, or still better with a knife. By this 

 method, also used in the investigation above-mentioned, a 

 small quantity of the substance (some mgr.) is enough for 

 an experiment. In some cases, however, the elements in 

 metallic form were soldered on the anticathode (Cd, Ag, Pd, 

 Zn) or pressed in tongs of copper soldered on it (In, Ru). 



With the elements lutetium-silver very sharp photo- 

 grammes X were obtained with a rocksalt crystal as reflector 

 and an exposure time of an hour. In the later experiments 

 a gypsum crystal was used. This also gave several rather 

 sharp lines, but the lines of weak intensity did not appear. 

 As window between the spectrograph and the X-ray tube 

 in the beginning a thin foil of aluminium (0*001 mm.) was 

 used. From tellurium it was replaced by a thin foil of gold- 

 beater's skin that very well transmits the soft rays (Moseley). 

 It lias a disadvantage, however, in also transmitting the lumi- 

 nescence light from the anticathode, which often was very 

 strong and blackened the plate. The spectral lines generally 

 were referred to the Kaj-line of copper, the wave-length of 

 which has been very carefully determined by Siegbahn and 

 Stenstrom §. The reflexion angles calculated have an 

 uncertainty of about 0*3 per cent. As grating-constant of 

 rocksalt the value 2*814 . 10" s cm., given by Moseley, was 



* Communicated bv the Author. 



t Phil. Ma^. vol. xxxii. p. 39 (1916). 



X Some of these photogrammes are reproduced in my doctor-dissertation, 

 Lunds Univ. Arsskr. N. F. Avd. ii. JBd. xii. Nr. 9 (1916). Here a 

 more detailed account of my investigations is given. 



§ Phys. Zcitschr. xvii. p.*48 (1916). 



