185 



Results. Starting from tlie value of 20,45 Volts for the lowest 

 excitation potential of heiinni, two rather pronounced excitation 

 potentials were found for neon at 17,35 and 19,15 Volts, 22,2 Volts 

 was found for the ionization-potential of neon; for argon two excita- 

 tion potentials were found at 12,25 and J 3,7 Volts, a less distinct 

 one at 14,7 Volts; the ionization-potential at 16,0 Volts. 



With the very complicated structure of the optical spectrum of 

 neon the occurrence of discrete fairly pronounced excitation potentials 

 seems surprising at first sight. If, however, the serial scheme of 

 neon drawn up by Paschf-n ') (tig. 8) is plotted in a scheme in the 

 way given by Bohr, it is directly seen that the values found are 

 in very good harmony with the optical measurement. The term 



£2 VOLTi 



Fig. 8. 



corresponding with the normal state and denoted by me as 0,5^ 

 has been added in the scheme, the value of this term has been 

 calculated from the ionization-potential. This term 0.5 s is first of 

 all followed by a group of four terms of the type of J. 5 .9; these 

 lie close together witliin a region which, expressed in Volts, is 

 smaller than 0,2 Volt., and can, therefore, not be separated in 

 measurements with colliding electrons. Then follows a group of2p 

 terms, the greater part of which lies again within 0.1 Volt. After 

 this come, about 1 Volt higher, the 3(/ terms. The other terms 

 succeed each other at distances of at most some hundredths of Volts, 



1) F. Paschen, Ann. d. Phys. 60, 405, 1919. 



12^ 



