﻿Magnetic Rotation Spectra of Sodium Vapour. 513 



A series in the magnetic spectrum coincides with the 

 series formed by the shorter \ member of each pair. The 

 wave-lengths and differences are given in the following- 

 table :— 



A. X differences. X. X differences. 



5165-85 oq.o! 77 ^ 38-82 



.126-54 



39-31 



0±20'04 QO.OQ 4Q70-8n 



508731 5*2a 2»*64 38 ' 21 



5048-49 o88i J894-58 38 ' 06 



I am quite at a loss as to how the series formed by the other 

 members of the doublets is originated. It appears to coincide 

 with the series excited by helium 5014, as will be seen by 

 reference to the chart. It appeared at first as if the exciting 

 line might lie between two adjacent fluorescent linos, and in 

 that way excite a double series ; but cadmium 5086 is slightly 

 on the short A, side of the magnetic line 5087*3, while the 

 wave-length of the other line of this pair is 5002, i. e. on the 

 long A. side. 



This is the only case recorded where a spectrum of doublets 

 is excited by monochromatic stimulation, though I am of 

 the opinion that the copper line 5152 behaves in the same 

 way. 



What is still more remarkable is the fact that if the exci- 

 tation is at a different point we no longer get doublets. The 

 lithium line at 4971 takes hold of one of the more refrangible 

 components of one of the doublets, but only a single series of 

 lines appears in the fluorescence spectrum (see chart, PL XV.). 

 The other series, i. e. the less refrangible components, cau be 

 separately excited by stimulation with the helium line 5014 

 (see chart). If we are dealing with anything in the nature 

 of electron doublets, we should expect both the lithium and 

 helium radiations to excite a fluorescence showing double lines. 



If we try to explain the phenomena by assuming two chains 

 of electrons fastened together at the point 5086, we must 

 account for the fact that the 5086 vibrator excites the other 

 chain when it is acted upon by light of its own frequency, but 

 not when it is vibrated by the lithium radiation acting at a 

 different point on the chain. I have adopted this hypothesis 

 of electron chains merely to aid in describing the physical 

 phenomena, and not with much hope that it will explain 

 anything. 



It seems much more likely that the different lines represent 

 vibrations of different frequencies of the same system. We 

 must not try to make the molecule too much like a piano. 



Phil. Mag. S. 6. Vol. 12. No. 71. Nov. 1906. 2 L 



