differ by a unit. A great many lines are, however, known for which the change of

is 0, and a few for which it is 2. In the simpler spectra, such lines are faint, except when produced under the influence of a strong magnetic field; but in the more complex spectra they are often numerous and strong.

“The inner quantum number (

) differs from one component of a multiple term to another, and also in the various series and systems, according to the following scheme.

SeriesSingletsDoubletsTripletsQuartetsQuintetsSextetsSeptets
1sj = 0112233
2p11,20,1,21,2,31,2,32,3,42,3,4
3d22,31,2,31,2,3,40,1,2,3,41,2,3,4,51,2,3,4,5
4f33,42,3,42,3,4,51,2,3,4,51,2,3,4,5,60,1,2,3,4,5,6
5g44,53,4,53,4,5,62,3,4,5,62,3,4,5,6,71,2,3,4,5,6,7

“Combinations occur only between terms for which