Hello. I think excited states of Argon atom is described by j,l coupling written as (2s+1)[K]J. However, when I read some papers describing cross section data for Argon atom, data are quoted with strange notation, Paschen notation. I tried to study the Paschen notation and found that its form is like nl# (ex: 2p10). n and l here are principal and orbital quantum number for an excited electron. Okay, that's easy. However, I really can't exactly figure out what subscript number # means! I just guess that this number is just a label of each state associated with particular n and l. However...which state is labeled 10? which state is 9? which state is 8?? Could you tell me what labeling order is used in the Paschen notation? I would be very happy if you give me a detailed description of the notation or any good material well describing the notation.