The 4d 9 -4d 8 4f transitions in Rh I-like ions from Cs XI to Ce XIV have been identified. Two lines, the 4d 10 5s 2 S-4d 9 5s4f 2 P transitions, in Cs IX to La XI have also been identified. In the La IX spectrum the 4d 10 4f 2 F and 4d 10 8p 2 P levels have also been established. Predictions for the corresponding transitions in Xe VIII and Xe X are also given.

The lanthanum spectrum was photographed in the 80-1240 Ð region on a variety of vacuum spectrographs using triggered spark sources. The analysis of nine-times ionized lanthanum (La X) has led to revision of four previously identi¢ed levels of the 5s5d con¢guration and established one new level 1 S 0 of the 5s6s con¢guration, four levels of the 5s4f con¢guration, and nine out of twelve levels of the 5p4f con¢guration. The least squares ¢tted parametric (LSF) and Hartree-Fock (HF) calculations interpret the observed spectrum adequately. Fifty eight lines are now classi¢ed in La X, out of which forty ¢ve are new lines.

The spectrum of Cesium was recorded in the 300–1240 Å wavelength region on a 3 m normal incidence spectrograph using a triggered spark source. On the basis of these observations seventh spectrum of cesium (Cs VII) was investigated. Fortythree out of the possible fortyfive odd parity levels belonging to the 5s2np (n = 5,6), 5p3, 5s5p5d, 5s5p6s and 5s2nf (n = 4,5) configurations, and twenty eight out of the possible thirtyfive even parity levels belonging to the 5s5p2, 5s25d, 5s26s and 5s5p4f configurations were established. From the previous analyses, one level was rejected, two misprinted level values corrected and ten other levels were confirmed. One hundred and eightyfour (184) lines were classified in Cs VII spectrum out of which one hundred and sixty-nine (169) lines are new. Least squares fitted (LSF) and Hartree–Fock (HFR) calculations were carried out to interpret the spectrum adequately.

The spectrum of three times ionized iridium, Ir IV, was investigated in the 650-2045 Å wavelength region. The analysis has led to the determination of the 5d 6 , 5d 5 6s and 5d 5 6p configurations. Twenty-nine of 34 theoretically possible 5d 6 levels, 44 of 74 possible 5d 5 6s levels and 150 of 214 possible 5d 5 6p levels have been established. The levels are based on 1348 classified spectral lines. The level structure and transition probabilities were calculated using the orthogonal operators technique. The energy parameters have been determined by the least squares fit to the observed levels. Calculated energy values and LS-compositions obtained from the fitted parameter values are given. The level optimization procedure and the determination of uncertainties of the obtained energy level values are discussed.

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