564 Prof. L. Vegard on the Spectrum 



In a similar way, ~ measures the number of times the 



positively charged rays get neutralized per unit length 

 of path in unit time ; and if we assume that, a neutralization 



is alwa}"s accompanied by light-emission, j- a ^ so measures 



the number of times a positively charged ray is brought to 

 emit light through neutralization per unit length of path and 

 in unit time. 



Ki measures the probability that a neutralization shall result 

 in the emission of the particular spectral line considered. 



k is a constant, which depends on the apparatus and the 

 units of the light- intensity. 



If we put the magnetic field on, the luminosity produced 

 by neutralization becomes practically zero and we get : 



i 



ani 



r 



= 



kfc 2 - e L - 

 A, 



e~ H 







I 



= 



K 'L t 



4-/c« 



n 2 



•t 



1 



"L 3 





i;. 



K 2 



»2 



X 



c 







= 



\K 2 n 2 





+1) 



e 



1 



If the ray bundle at the section (A-B) is in a state of 

 statistical equilibrium, we have according to Wien : 



n 2 L 2 

 and I / ^ Kl \\ +* 



As we saw, (I/I TO ) bJ. came out nearly equal to e lL ' 2 , and 



TT > 



thus Tj^^r should be a small quantity f-or H a and EL. 

 -H 2 ^2 



If the probability that a "light impact" of the. neutral 



ray shall result in the emission of H^, say, is the same as the 



probability for a H^ emission resulting from neutralization, 



then k-i — k 2 and T - should be a fairly small quantity. 

 ^2 

 Now if "the mean free path" \ of successive "light 

 collisions " of the neutral ray is of the same order of 

 magnitude as the mean free path of the gas molecules 

 in the observation chamber, we find, as a matter of fact, 



that y~ is a small quantity. 



