Lines occurring as satellites on the long-wavelength side of the 3d10 –3d94p resonance lines of Ni-like ions have been investigated with a low-inductance vacuum spark and a 10.7-m spectrograph for the elements Y, Zr, Nb, and Mo. The lines are interpreted as 3d104s–3d94s4p and 3d10 4p–3d9 4p2 transitions in the Cu-like ions Y XI, Zr XII, Nb XIII, and Mo XIV and 3d104s2–3d,94s24p transitions in the Zn-like ions Y X, Zr XI, Nb XII, and Mo XIII. The spectra of the Cu-like ions were interpreted by generalized least-squares fits for the energy levels of the sequence of four ions. Thirty-nine levels of 3d94s4p were interpreted simultaneously with a root-mean-square deviation of 122 cm−1; forty-four levels of 3d94p2 were interpreted in the same way with a root-mean-square deviation of 200 cm−1. Line identifications and energy levels were obtained for the 3d107p configuration of the Cu-like ions Y XI-Mo XIV.
Jean-François Wyart, Joseph Reader, and Aleksandr Ryabtsev, "3d-4p Transitions in the zinclike and copperlike ions Y X, XI; Zr XI, XII; Nb XII, XIII; and Mo XIII, XIV," J. Opt. Soc. Am. 71, 692-698 (1981)