436 



BELL SYSTEM TECHNICAL JOURX.IL 



,ransilinn> from various l.xc-ls of Hr- .s-rnlu,nn. This is ihc sharp 

 (or second) subordimite scries, and us syiiilx.l is (2,/>) - (w.^). 1 he 

 other series consists of transitions from various levels of the rf-column; 

 it is the diffuse (or first) subordinate series, and its symbol is {2,p)- 

 (m4). ^'elUnv and red arrows signify these series, respectively, in 

 Fig. G. Of the two line-series terminating upon the (3,rf) level, only 

 one has been endowed with a name; this is the series (3,<f)-(m/), 

 known alternatively as the Berf-mann or xhi^ fundamental series (the 

 second name is a bad one) and symbolized by green arrows in Pig. /. 

 These series seem to be the only ones which impressed themselves 

 strongly enough up.^n the minds of spectroscopic experts to receive 

 names '' from them. Howe%er, many other series have been identihed, 

 and emphasized, especially since Bohr's manner of thinking took root 

 among the students of spectra; for instance, series terminating upon 

 (2,x) and (3,s), which are conspicuous in the spectrum d luliuni. an<i 

 such line-series as (3,./) - (m,/'), and (4,/)-(w,rf). 



Several rules about line-series, which are very promnuiu in accounts 

 spectra, become self-evident when the rules governing the stationary 

 states are mastered (of c.u.rs., this is only because the latter rules 

 are based upon the former). For instance, there is a rule that the 

 sharp and the diffuse series haNe the same limiting-frequency; and 

 there is a rule that the difference between this limiting-frequency 

 and the limiling-fre(|uency of the principal series is equal to the 

 frequency of the first line of the principal series. The reader may 

 derive these bv inspecting Fig. (i. , r . • i 



Such rules do not ai>i)lv to the spectra of hydrogen and of iomze<l- 

 helium which are profoundly different from the spectra of sodmm 

 and other elements; and it is perilous to attach such names as principal 

 or subordinate to the line-series of those fust elements. The stationary 

 stales of those elements are known by their energy-values, and the 

 series by the names of their discoverers or iiiieriireters. 



E 7. Further A nalysis of the SUiliomiry States of llydroiien a nd Ionized 

 Helium ; Fine Structure 



In our earlier analysis of the spectrum ..f iiydrogcn and the siHctrum 

 of ionized helium, we inferred from each of these spectra ., tarn, Is ol 

 stationary states, the energy-values of which follow one upon Uic 

 oilur in a verv regular [irocession governed hy a snniile luimcncal 

 law This makes it practically impossible i.. .liv l.lc up ''h'sc station- 

 ary stales into classes; all of the levels for each .,f ihe at..ms must 



"The reader will recognize, in the initials of those names, thr l.iuis x, /', ■/, /', 

 :in<l I iis<-<l to ilesiRnale the several .oliiMins "I le\cls. 



