210 Mr Thomson, Note on the nature of the carriers of Anode Rays 



A note on the nature of the carriers of the Anode Rays. By 

 G. P. Thomson, M.A., Fellow of Corpus Christi College. 



[Received 3 August 1920.] 



The importance of positive rays as an instrument of research 

 is now thoroughly established, and the success of the recent in- 

 vestigations of Dr Aston on isotopes makes it the more to be 

 regretted that so far, with the exception of mercury, no metal has 

 with certainty been identified in the photograph of the mass spectra 

 of positive rays; and this in spite of a considerable number of 

 attempts. In these circumstances the work of Gehrcke and 

 Reichenheim* on anode rays suggested the possibility that these 

 might fill the gap. From a rough measurement of ejm Gehrcke 

 and Reichenheim showed that the anode rays probably consist of 

 positively charged atoms of metal. They did not however photo- 

 graph the particles and their method of determining ejm made use 

 of magnetic deflection only, and so involved the assumption that 

 the velocity was constant and known. It was therefore not capable 

 of giving more than a rough approximation and could not lead to 

 separation of any isotopes which may exist. In the experiments 

 described below, which are of a preliminary nature, I have tried 

 to improve on their method in these points. 



Anode rays are formed when a mixture of various metallic 

 chlorides and iodides with graphite is used as the anode in a dis- 

 charge tube under reduced pressure. They are visible as a slightly 

 diverging pencil of light starting from the surface of the anode and 

 very roughly normal to it. In order to investigate the value of ejm 

 for the particles which cause this light I placed in the path of the 

 beam, and 2 or 3 cm. from the anode, an insulated aluminium plate 

 pierced with a hole in which was fastened the end of a fine tube 

 of -3 mm. bore. The parallel beam of rays thus produced was 

 analysed by coincident electrostatic and magnetic fields in the 

 usual manner for positive raysf , and the deflected particles allowed 

 to strike on a photographic plate. With exposures of about 

 20 minutes well-marked results have been obtained, the particles 

 affecting the photographic plate in the same manner as positive 

 rays. 



Using a paste composed of a mixture of KI, LiCl and graphite, 

 short paraboHc arcs appeared whose magnetic displacements were 



* Verh. d. Phys. GeselL, 8, p. 559; 9, pp. 76, 200, 376; 10, p. 217. 

 t Bays of Positive Electricity, J. J. Thomson, p. 20. 



