For each value of \(n_2\), we have an absorption line. All possible values of \(n_2\) generates an absorption series.
With many \(n_1=1\) plots corresponding to different allowable energy states, we have a number of absorption series that depict such plausible energy states.
Which is confusing because of the one added level of indirection. For example,
\(n_1=1\) for \(n=1\)
\(n_1=1\) for \(n=2\)
and
\(n_1=1\) for \(n=3\)
where the lowest energy level of a particle of two constituent basic particles is different (higher) than the lowest energy of a particle with three constituent basic particles.
What happened to \(n_i=n_{oi}=i\)?
This expression considers the lowest (first, \(n_1=1\)) energy level in a set of all particle sizes (all \(n\)).
Energy transitions occur for a particle given its number of constituent basic particle size \(n\) with a particular first/lowest energy state. The lowest energy level \(n_1\), given \(n\) is an absorption series given all values of \(n_2\). Across all possible values of \(n_1\) as particle \(n\) size changes, we have different absorption series.
And the question was, why is it an absorption line? Which leads to the question, are there fine gaps in the background emission spectrum?
Note: In the plot above \(n_1=1\) is indicative of the lowest energy level of a particular \(n\). Given all values of \(n_2\), \(n_1=1\) for a particular \(n\) generates a absorption series. When \(n\) is higher \(n_1=1\) is lower, with less energy. Different \(n\), generates different spectra series.
