But today when I try to read some papers working with Alkaline atom, I couldn't figure out how they plot the Rubidium energy level. From my undergraduate study, I thought the diagram of Rubidium atom should be something like this, the outer layer electron is on the energy level of $5S$:

The spin up and spin down electrons occupied the energy levels from ground state go upward. But I really cannot figure out the diagrams below:

and

and

So my questions are:

• How could the 6S and 7S energy levels be occupied?
• What does the subscript $S_{1/2}$ and $P_{3/2}$ means? Does this means spin? But electron should only have spin number $\pm 1$, right?
• What is the F quantum number? It is not the F from the "spdf" orbital notation, right?
• Can anyone draw a diagram of ${ }^{87} \mathbf{R b}$ with all energy levels and the relationship between different quantum numbers?

Thanks for any help!