Resonance Spectra of Iodine Vapour. 

 Table. 



475 



A. 



B. 



6810 



C. 



6850 



a. 



b. 



_j_ 



d. 



e. 













6726 



6625 



6660 



84 =» 



1«3 



85 



90 



40 



74-4 



(3558 



65-16 



6578 



79 



82 



35 



73 





6460 



6490 



81-5 = T 



86 



88 



32 



0395 



6373 



6102 



82 



87 



88 



30 



71-8 



71 



70-4 



6y-8 



69-3 



68-5 



67 8 



671 



66-2 



65 6 



65-3 



63-7 



63 - 5 



644 



62 



6313 



6296 



6323 



77-5 



77 



79 



29 



6235-5 



6217-5 



6240 



76 



78-5 



83 



27 



6159-5 



6140 



6161 



75 



77-5 



79 



22-5 



6084-5 



6063-5 



6084-5 



73-5 



76-5 



76-5 



21 



60U9-5 



5985 



6009-5 



72 



77 5 



75 



21 



5936 



5910 



5936 



72 



75 



73-5 



24-5 



5864 



5840-5 



5864 



68-5 



69-5 



72 



26 



5792 



5769-5 



57905 



66-5 



71 



73 5 



235 



5723-5 



5698 



5723-5 



68-5 



715 



67 



21 



5657 



5630 



5658-5 



64 



68 



65 



25-5 



5588-5 







635 







28-5 



5524-5 







64-4 









5461 



53966 







59-1 









5337-5 















or perhaps a little less, but as I have pointed out in a previous 

 paper, the measured wave-length of a line may be slightly 

 in error resulting from absorption, i. e. one side of the 

 emission-line may be removed by a neighbouring absorption- 

 line, its centre o£ gravity appearing shifted. This may 

 perhaps be the cause of the irregularities observed. If the 

 spacing were accurately constant the wave-lengths of the 

 lines of the series could be represented by the following 

 formula : X = \ + mk, in which \ is the wave-length of the 

 exciting line, m is a natural number, 1, 2, 3, etc., and k is 

 the common difference. The value of k is obtained by taking 

 the difference between the wave-length of the exciting lino 

 and that of any other line and dividing it by that particular 

 value of m which fixes the position of the line in question in 

 the series. This arrangement was adopted in a previous 

 paper treating of the resonance spectra of sodium by Wood 

 and Hackett (Astro-Phys. Journ. vol. xxx. No. 5, 1909), 

 since it prevents the double discrepancy which arises when 

 the other arrangement is used. The values of k obtained in 

 this way for the series excited by the green mercury line are 

 given in column e,. which should be compared with column a. 

 In the case of sodium vapour this increase in the value of 

 h with increasing wave-length was observed in many cases, 

 though the increment was not as marked as in the case of 

 iodine. 



