THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



-^ 



OCTOBER 1920. 







XLVI. On the Scattering of Light by Un symmetrical Atoms 

 and Molecules. By Sir J. J. Thomson, O.M., P.R.S.* 



"Y\ T HEN the arrangement of the electrons in an atom 

 H is quite symmetrical, the displacement of an electron 

 due to an external force will always be in the direction 

 of that force and the ratio of the displacement to the 

 force will be independent of the direction of the force. 

 These are the conditions postulated in the investigations 

 hitherto given of the scattering of light by small particles, 

 and we know that when they are fulfilled and the incident 

 light is plane polarized the intensity of the scattered light 

 vanishes along the direction of the electric force in the 

 incident light. When the incident light is not polarized, 

 the scattered light when observed in a direction. at right 

 angles to the incident light is completely polarized. 



These results, however, will not hold when the atom 

 is unsymmetrical and the displacement of an electron is 

 not necessarily in the direction of the disturbing force. 

 We shall see that under these conditions the intensity 

 of the scattered light does not vanish in any direction : 

 it, however, varies with the direction, and experiments on 

 the law of variation such as those made by Lord Eayleigh 

 give valuable information about the structure of the atom. 



Suppose that OA, OB, OC are three directions in an 

 atom, at right angles to each other such that the electrons 



* Communicated by the Author. 

 Phil. Mag. S. 6. Vol. 40. No. 238. Oct. 1920. 2 D 



