Relativistic Azimuthal Quantum Number Analog

33) and (6.34) suggest that adding il2 to the operator on the left-hand side of the equations simplifies the eigenvalue as —hl2) then drops out. We therefore define the operator k, 

The quantum number k will turn out to play an analogous role in the Dirac theory of atoms that is played by I in the nonrelativistic theory (i.e., being associated with a constant of the motion). In the 1930s, Swirles introduced a special notation to assign the quantum numbers of different quantum mechanical states Yj(r) to the familiar spectroscopic notation for the states of hydrogen-like atoms such as s=sharp, p=principal, d=diffuse (see Table 6.1 for an overview). 

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