482 



Dr. Megh Nad Saha on Ionization 



In the case of strontium and barium, owing to their com- 

 paratively low ionization potential, ionization at 6000° is 

 practically complete at 10 -3 atmosphere, and the heights 

 shown by the lines of the unionized atoms of these elements 

 are still lower. Compare the Tables IV., V"., YI. 



The results of the flash-spectrum observations are thus 

 seen to be very satisfactorily accounted for on the basis of 

 our theory. 



Laboratory experiments also, as far as they go, are in 

 qualitative agreement with our theory. It is well known 

 that in the flame, the flames due to the ionized atom either 

 do not occur at all, or even if they do occur they are ex- 

 tremely faint compared with the lines of the unionized atom. 

 As the temperature is increased, the " enhanced lines " begin 

 to strengthen, until at the temperature of the arc they are 

 comparable in intensity to the lines of the normal atom. 



We give below the results of King * on the relative 

 intensity of the u enhanced " and ordinary lines of the 





Table YIL 









Temp. 











Photo- 



Chromo- 



Actual ... 



1923 



2273 



2623 



Arc. 



sphere. 



sphere. 



Element. Approx.... 



2000 



2500 



3000 



4000 



7500 



6000 



Line. 





Intensity. 









Ca 4227 (g) ... 



300 



500 



1000 



500 



20 



25 



Ca+ ... 3968(H)... 



18 



25 



50 



350 



700 



80 



3933(E)... 



20 



30 



60 



400 



1000 



100 



Proportion of ionized 



1-4. 10~ 3 



7.10- 2 



1 



26 



75 



93 



atoms in per cents. 











(P=10 _1 ) 



(P = 10~ 3 > 



Sr 4607 



300 



400 



600 



600 



1 



2 



Sr+ ... 4216 ... 1 



4078 ...J 



6 



15 



30 



400 



5 



40 



12 



25 



40 



400 



8 



40 



Proportion of Sr+ 



4.10" 3 



2.10- 1 



2-5 



45 



84 



97 



in per cents. 











(P=10 -1 ) 



(p=Kr 3 > 



Ba 5536 



400 



500 



1000 



1000 



o 



1 



4934 ...1 

 4554 ...] 



50 



60 



70 



700 



7 



12 



70 



80 



100 



1000 



8 



20 



Proportion of Ba+ 



2.10" 2 



7.10- 1 



5 



68 



91 



98 



in per cents. 









i 



(P=10 _1 ) 



(P=10 _3 > 



N.B. — The intensity scale 

 chromosphere is different from 



under the headings photosphere and 

 the scale in King's furnace spectra. 



* King, ' The Astrophysical Journal/ vol. xlviii. p. 13. 



