91 



375 



observed, but that only two broad diffuse lines were visible (with their centres of 

 gravity lying at 3203,140 A and 3202,964 À), because if the electric forces present 

 in the luminous gas are of the same order of magnitude as in the case of the spark 

 discharge image of 4686 A, these forces must be expected to be strong enough to 

 destroy the details of the fine structure to a large degree. In the continuous discharge 

 spectrogram the strongest three components I, II, III correspond to the original 

 components (14 -* 03), (23 -^ 12) and (32-^21), and their intensities may according to 

 Faschkn be characterised by the numbers 7, 8, 4 respectively, in general agreement 

 with the values of n'„R'^ and n'.^R"' for these components given in table X. It must 

 be expected, however, that component I contains not only the light of the original 

 component (14 — 03) but also that of the original component (41 -* 12) (and perhaps 

 (32-^03)) and of the new components (05-^03) and (23-^03); that II represents, 

 besides (23^ 12), also (14 — 12) and perhaps (32-* 12), and finally that III represents, 

 besides (32-* 21), also the new component (23^21). The two other weak com- 

 ponents which Paschen observes in the continuous discharge image correspond to 

 the two only new components which could be expected to appear separately, uiz. 

 (41 -03) and (41 ^21). 



The helium lines (6 -> 3), (7 — 3), (8^3) and (9 3) have also been examined 

 by Paschen. For the first three of these it was found possible to detect three com- 

 ponents I, II, III which must be assumed to correspond to transitions to the final 

 states (03), (12) and (21) respectively and the positions of which coincide to a 

 high degree of approximation with those of the original components (n' — 4, 4 — 0,3), 

 (n'-^3, 3 —1,2) and {n' — 2,2 —2,1). In agreement with the present theory, the 

 intensity of I was smaller than that of II but a deal larger than that of III. The 

 energy differences between the different initial states were so small that separate 

 new components could not be observed, but the perturbing influence of electric 

 fields in the vacuum tube is no doubt considerable for these lines. 



Paschen has further examined the helium lines (6 — 4), (7 — 4), ... (12 — 4). 

 TIk' first of these lines, 6560 A, appeared only very weak in the spectrograms and 

 a fine structure could not be observed. An estimate for the intensities of the original 

 components of this line has been given in table X. All the other lines showed two 

 ditruse components the strongest of which in some spectrograms again showed a 

 resolution in two components. Fig. 12 contains a scheme of the theoretical and of 

 the observed fine structure of the line 5411,2 Å (7 — 4). For simplicity only the 

 original components are drawn, their intensities as estimated from table X being 

 indicated by the lengths of the lines. The arrows indicate the centres of gravity ol 

 the components observed by Paschen. The two small arrows on the right indicate 

 the positions of the centres of gravity of the two components in which, in one of 

 Paschen's spectrograms, the stronger component was resolved. It will be seen that 

 the observations are in agreement with the theory. The existence of separate new 

 components, on account of the small frequency dillerences between the different 

 possible initial states, could not be observed. .As it may be seen from Paschfn s 



48" 



