On the ^1P° levels of Li^+

The line 4156 Å is not seen in the beam-foil spectrum of Li+. After a brief review of the Li+ spectrum intended to clarify confusion in the literature, evidence is assembled to support the view that this line has been incorrectly classified as 4 1P∘ → 3 1S. A calculation of Edlén and Löfstrand [ J. Phys. B3, 1380 ( 1970)] is revised to predict higher n1P∘ levels, and some identifications of lines observed in beam-foil spectroscopy are reported. The experimental estimate of the ionization potential of Li+ done by Herzberg and Moore [ Can. J. Phys.37, 1293 ( 1959)], which depended on the 4 1P∘ level, is revised to 610 077.8 ± 4.5 cm−1.