Ionization Potential of Boron, and the Isotopic and Fine Structure of 2s2p^2 2D

The nf2F series (n = 4–11) of B i is found from combinations with 3d2D and 2s2p2 2D, and the series limit is derived by means of a Ritz formula, yielding an ionization potential of 66 928.10±0.1 cm−1. The same value applies to both 10B and 11B because the isotope shift of the ground state is shown to be zero. From the resolved structure of the transition 2s2p2 2D–4f2F at 8212 Å, we derive for 2s2p2 2D a fine-structure interval of −0.31 cm−1 and an isotope shift of −0.58 cm−1, corresponding to a specific mass shift of −0.67 cm−1.