SOME CONTEMPORARY ADVANCES IN PHYSICS— X 121 



S. Interpretation of Multiplets 



Heretofore in the Third Part of this article I ha\e repeated the 

 procedure adopted in the First Part, simplifying the actual facts by 

 writing as though the Stationary States of each atom were arranged 

 in sequences of individual terms, each sequence being distinguished 

 by a particular value of the Azimuthal Quantum Number. Here as 

 there, it finally becomes necessary to concede the complexity of the 

 facts, and recognize that the sequences in question are sequences not 

 of individual terms, but of groups of terms. Thus for instance the 

 sodium atom possesses a ^-sequence, not of individual terms but of 

 pairs of terms — a pair 2pi and 2p2, then a pair Spi and 3p2, then a 

 multitude of other pairs. For another instance, the mercury atom 

 exhibits a ^-sequence not of individual terms but of triads of terms — 

 a triad 2pi and 2p2 and 2p3, then a triad 2pi and Sp2 and 3p3, and 

 then a procession of other triads. These sequences are collected 

 into systems : an 5-sequence and a ^-sequence and a c^-sequence and 

 several more constitute a system. There are singlet systems and 

 doublet systems and triplet systems and systems of still higher multi- 

 plicity; and each kind of system is distinguished by a certain manner 

 of grouping of the terms which form its various sequences. Note- 

 worthy and peculiar laws govern these groupings; in a doublet system, 

 for instance, the 5-sequence consists of individual terms, but all the 

 others consist of pairs of terms; in a quartet system, the 5-sequence 

 is made up of single terms, the ^-sequence of triads of terms, the 

 remaining sequences of groups of four terms each. From the First 

 Part of this article I reprint a Table showing how the terms are grouped 

 in systems of all multiplicities from the singlet to the octet. The 

 numbers opposite the name of each system and under the letters of 

 the various sequences show how many terms belong to each group 

 in the various sequences of that system. 



TABLE I 



Name of System s p d f f f" 



Singlet 



Doublet 



Triplet 



Quartet 



Quintet 



Sextet 



Septet 



Octet 



