multiplicity (spin multiplicity)

https://doi.org/10.1351/goldbook.M04062
The number of possible orientations, calculated as \(2\ S+1\), of the spin @A00353@ corresponding to a given total spin quantum number (\(S\)), for the same spatial electronic wavefunction. A state of singlet multiplicity has \(S=0\) and \(2\ S+1=1\). A @D01853@ has \(S=\frac{1}{2}\), \(2\ S+1=2\), etc. Note that when \(S>L\) (the total orbital @A00353@ possible) there are only \(2\ L+1\) orientations of total @A00353@ possible.
Source:
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2255 [Terms] [Paper]