Spectra and energy levels of ions in the zinc isoelectronic sequence from Rb viii to Mo xiii

Spectra of the zinclike ions Rb v i i i, Sr i x, Y x, Zr x i, Nb x i i, and Mo x i i i were excited with sparks and laser-produced plasmas and observed with normal- and grazing-incidence vacuum spectrographs. Almost all levels of the 4$s^2$, 4s4p, 4$p^2$, 4s4d, 4s5s, 4s5p, 4p5s, and 4s5d configurations were established in these ions. Several 4s4f ${}^3$F–4s5g ${}^3$G transitions of Nb x i i and Mo x i i i were also identified. The observed energy levels were interpreted by means of least-squares parametric fits and Hartree-Fock calculations. The ionization energies were determined as 132.79(25) eV for Rb v i i i, 158.33(25) eV for Sr i x, 185.77(37) eV for Y x, 214.86(37) eV for Zr x i, 246.11(37) eV for Nb xii, and 279.09(50) eV for Mo x i i i.