Question

This may be a silly question, but I have not yet found an answer and I don't really know how to word my searches. I have been looking at the NIST Atomic Spectra Database (and also atomic physics papers) and I see configurations of excited states that have terms in parenthesis in them and I don't know what it means. For example, I might see a configuration for N II

2s2p^2(4^P)3p

and the term is listed as 3^S^o.

What would the 4P term in the middle of the configuration mean? When would you write a configuration like this?

Answer 1

The term in parenthesis in the excited state configuration represents the spectroscopic term symbol, providing information about the angular momentum and spin. These symbols are used to characterize energy levels in atomic physics.

Step-by-step explanation:

The term in parenthesis in the excited state configuration represents the spectroscopic term symbol, which provides information about the total angular momentum and spin of the electrons in the configuration. In the example you provided (N II 2s2p^2(4^P)3p), the term 4P indicates that the configuration has a total angular momentum of 4 and spin 0.

These term symbols are used in atomic physics to characterize the energy levels of atoms and ions. They are derived from the Russell-Saunders coupling, which combines the angular momentum of individual electrons.

In general, excited state configurations with term symbols in parenthesis are used when there are degenerate energy levels within the same set of quantum numbers (n, l).