506 Tables 611 (continued) and 615 



NORMAL SERIES RELATIONS IN ATOMIC SPECTRA (concluded) 



Series of terms arise from configurations in which one electron, keeping the same 

 value of l, has successively higher values of n, the total quantum number. A configuration 

 such as 3d4S4p theoretically belongs therefore to three different series in which either 

 the d, the s, or the p electron takes higher total quantum numbers. In practice this com- 

 plication is rare as there is almost always one electron which is more easily detached 

 than the others, and is therefore the one to take the higher quantum numbers and give the 

 series. An electron whose total quantum number is higher than those of the electrons 

 discussed in the last section may always be regarded as the most easily detached, as may 

 also one belonging to a group which is not represented in the configurations giving the 

 low terms of the spectrum. 



The limiting configuration (i.e., the one obtained by the removal of the electron which 

 takes successively higher values of n to give the series) usually gives multiple terms. 

 Each separate level of these terms is the limit of certain sets of the individual levels of the 

 multiple terms converging to the limit. The configuration of the limit is to be represented 

 as above, followed in parentheses by the notation for the particular type of term which 

 is the limit for the series under consideration, than by the " running " electron, then by 

 the notation for the term (or particular level) given by the whole configuration. For 

 instance the s 2 p 3 configuration of O II gives 4 S°, 2 D° and 2 P° terms. If we add to this one 

 np electron to get terms of O I the 4 S° term gives 5 P and 3 P, the 2 D° gives 3 P, 3 D, 3 F, *P, 

 *D, a F and the 2 P° gives 3 S, 3 P, 3 D, 1 S, 'P, U D terms. Thus, theoretically, the s 2 p 3 np con- 

 figuration gives three 3 P terms, two 3 D terms, two J P terms and two *D terms. For dis- 

 tinguishing between them it is most convenient to use the notation suggested above. The 

 three P terms would be written sV( 4 S°)np 3 P, s 2 p 3 ( 2 D°)np 3 P, and s 2 p 3 ( 2 P°)np 3 P. 



The notation here described may be considerably simplified for many of the simpler 

 spectra. The abbreviations employed should in all cases be clearly explained by the 

 author. 



TABLE 615. — Comparison of Notations 



Among the earlier systems of notation which are frequently met with are the following : 



Even terms S P' D F' G 



Odd terms S' P D' F G' 



As regards the total quantum numbers Fowler usually designates the lowest members 

 of the series by is, ip, 2d, si and Paschen-Gotze by is, 2p, 3d, etc. 



The current notation uses Bohr's values which differ from element to element : thus the 

 lowest term in Li is 2 2 S, in Na 3 2 S, in K 4 2 S, in Rb 5 2 S, and in Cs 6 2 S. 



Smithsonian Tables 



