The total angular momentum is the vector sum of the spin angular momentum S and orbital angular momentum L,
(1)
It is quantized by two quantum numbers j and as
(2)
(3)
Here, j is the first total angular momentum quantum number, which takes half-integer values given by
(4)
with l the azimuthal quantum number. Similarly, is the second total angular momentum quantum number, which takes half-integer values given by , ..., j.
Azimuthal Quantum Number, Orbital Angular Momentum, Spin Angular Momentum, Total Angular Momentum Quantum Numbers