The Theory of Spectra and Atomic Constitution: Three Essays

by Niels Bohr

) correspond to the variable term in the "sharp series," the lines of which are emitted by transitions from these states to the first state in the second row. The states in the second row (

) correspond to the variable term in the "principal series" which is emitted by transitions from these states to the first state in the

row. The

states correspond to the variable term in the "diffuse series," which like the sharp series is emitted by transitions to the first state in the

row, and finally the