Answers are grounded in this paper and cite their sources.
Observations have been made in the range 1200–2000A of the arc spectra of B, In, Tl, Pb, and Bi. The analysis of B i and Bi i has been considerably extended with the aid of these observations, while new levels been found in In i, Tl i, and Pb i.
No takes yet. Share an insight, caveat, or question.
Harold E. Clearman (1952) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: