This notation is cool as it gives the spin quantum number, which is important e.g. when talking about hyperfine structure.
But it is a bit crap that the spin is not given simply as but rather mixes up both the azimuthal quantum number and spin. What is the reason?
Spectroscopic notation by Andre K (2014)
Source. Articles by others on the same topic
The spin quantum number is a fundamental quantum number that describes the intrinsic angular momentum (or "spin") of a particle, particularly in the context of quantum mechanics and atomic physics. It is denoted by the letter \( s \) or sometimes by \( m_s \) when referring to its projection along a specific axis (usually the z-axis). Key characteristics of the spin quantum number include: 1. **Values**: The spin quantum number can take on half-integer or integer values.