The twelve 4ƒ12 (3H6)6s6p levels of neutral erbium are reported and interpreted in the JIJII coupling scheme. Intensity relations of the lines connecting 10 of them to the ground level are discussed. The values of G1(6s6p) = 3373 cm-1 and ζp = 1870 cm-1 for the interaction parameters are obtained directly from these levels.
NISSAN SPECTOR, "4ƒ12 (3H6)6s6p Levels of Neutral Erbium (Er I)," J. Opt. Soc. Am. 57, 308-311 (1967)