Spectroscopic notation is based on facts taken from molecular symmetry.

Figure 1(b) illustrates this transition with the corresponding spectroscopic notation.

In the following table, the same particle can be named with the spectroscopic notation or with its mass.

Spectroscopic notation provides various ways to specify atomic ionization states, as well as atomic and molecular orbitals.

The spectroscopic notation of molecules uses Greek letters to represent the modulus of the orbital angular momentum along the internuclear axis.

As is clear from dimensional analysis, for historical reasons the last equation uses spectroscopic notation in which represents a wavenumber obeying , and not an angular frequency given by .

Bound states can be described with the spectroscopic notation L (see term symbol), where S is the total spin quantum number, L the total orbital momentum quantum number and J the total angular momentum quantum number.

The azimuthal quantum number is the second of a set of quantum numbers which describe the unique quantum state of an electron (the others being the principal quantum number, following spectroscopic notation, the magnetic quantum number, and the spin quantum number).