[Proc. Rot. Soc. Vjctoria 34 (N.S.), Pt. II., 1922]. 



Art. XX. — High Frequency Spectra — K Series of Platinum. 

 By J. STANLEY ROGERS, B.A., B.Se. 



(Communicated by Professor T. H. Laby, M.A., Sc.D., F.Inst.P.) 

 (With Text Figs. 1a, 1b, and 2.) 

 [Read 8th December, 1921.] 



Introduction. 



The purpose of this paper is to describe a precise method of 

 :measuring the wave lengths of the high frequency spectrum of 

 platinum. 



The method employed is one in which a rotating crystal spec- 

 trometer is used, and the platinum lines, together with those of 

 tungsten, are recorded on the same film. The wave lengths of 

 the platinum lines are deduced by inter- and extra-polation from 

 the tungsten lines, the wave lengths of which are known with 

 great accuracy, having been measured recently with great pre- 

 •cision by Siegbahn,^ and by Duane and Stenstrom.^ 



The investigation of the K lines of platinum, in common with 

 those of other heavy elements, is beset with certain difficulties, 

 which have prevented the spectra of these elements being deter- 

 mined. 



In order to excite efficiently the K spectrum of an element of 

 high atomic number, it is necessary to use the substance as target 

 in an X-ray tube. A very high potential difference must then 

 ibe applied to the tube, since a minimum pressure of 78,000. volt 

 is required to obtain the K series of platinum. Under such high 

 pressures there is always the risk that the tube will fail. Again, 

 a very high vacuum must be present in the tube. In the case 

 of a gas-filled tube this became a source of considerable diffi- 

 culty, for, even when the requisite vacuum is obtained, the tube 

 "becomes very uncertain in operation, and, under the very 

 "best conditions, only a small current can be passed 

 through the tube. In consequence, the X-rays produced possess 



1. Phil. Mag. XXXVIII., Nov.. 1919. 



2. Proc. Nat. Acad. Sci., VI., 1920, p. 477. 



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