﻿1130 Prof. M. N. Saha on Temperature Ionization of 



normal, and we shall see later on that, as a rule, elements 

 belonging to the higher groups are more easily ionized than 

 elements of the preceding group, and the successive steps of 

 ionization follow each other in rather quick succession. 



First o£ all, let us consider the relative intensities of the 

 lines of alkalies and the alkaline earths in the sun and the 

 spot spectra. 



LP 



Alkalies. 



Intensity. 



Volts. Sun. Spot. 



Na 511 30 60 



K 432 6 15 



E 416 — 1 



Cs 381 — ? 



Alkaline Earths. 



-r p Intensity. 



Volts. Sun. Spot. 



Mg 765 30 30* 



Oa 608 20 25 



Sr 5, 1 3 



Ba 5-12 — — 



* Russell, loc. cit. p. 130 ; the intensity given against M~g is that due to the 

 2p-3s line ; the resonance line of Mg, \ — 2852, is beyond the range. 



The table shows that Ba is at least as highly ionized as 

 lib, though I 1 — 1 2 =96 volt. Sr is only slightly less ionized 

 than Rb, both in the sun and the spot. Calcium is less 

 ionized than potassium. When we compare the intensity of" 

 the lines of Ca and Na, we find that in the sun they are 

 almost equally ionized (calcium a bit more), but in the spot 

 the recombination between Ca + and (<?) is much less marked 

 than between Na + and e. 



Prof. Russell suggests that if the effect o£ radiation could 

 be taken into account, the theory would be more improved, 

 and the discrepancies could be explained. (See Russell, 

 The Astro. Journ., May 1922.) 



II. 



It cannot be denied that the theory is always to be re- 

 garded as incomplete until the effect of the general field of 

 radiation can be taken into account. But it is doubtful if 

 this alone will explain all the discrepancies. Another factor, 

 the consideration of which is presented below, seems to play a 

 rather important part. 



It is now well accepted that elements of the first group, 

 Li, Na, K, Rb, Cs, have only one electron in the outermost 

 ring, while metals of the second group, Mg, Ca, Ba, Sr, have 

 two electrons in the outer ring. Besides, these two electrons 

 are equally situated — in other word*, whenever a Ca-atom is 

 subjected to the action of any physical agency tending to 

 tear off the electrons, it will act equally on both of the 

 valency electrons. In the case of the alkalies, it will act on 



