Wavelengths and Energy Levels of the Second Spectrum of Cerium (Ce ii)

The second spectrum of cerium (Ce ii) has been compiled in the wavelength region between 2500 Å and 24 000 Å. Of the 11 000 lines in the list, about 7500 are now classified as transitions between 192 odd levels and 288 even levels. The odd levels arise from 5 configurations (4f5d ², 4f5d6s, 4f6s ², 4f ²6p, and 4f ³) and the even levels from 7 configurations (4f ²6s, 4f ²5d, 4f5d6p, 4f6s6p, 5d ³, 5d ²6s, and 5d6s ²). The known levels extend up to only 52 000 cm^-1 although the ionization potential is known to be 35 000 cm^-1 higher.