We have measured the oscillator strength of the Ni I line at 6300.34Å, which is known to be blended with the forbidden [O I] λ6300 line, used for determination of the oxygen abundance in cool stars. We give also wavelengths of the two isotopic line components of 58 Ni and 60 Ni derived from the asymmetric laboratory line profile. These two line components of Ni I have to be considered when calculating a line profile of the 6300Å feature observed in stellar and solar spectra. We also discuss the labelling of the energy levels involved in the Ni I line, as level mixing makes the theoretical predictions uncertain.

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Spectra of nickel, emitted from hollow cathode discharges, have been recorded in the region 1700-55000A (58 800-1800cm-'). Fourier transform spectrometers were used above 1800A, yielding very high accuracy and resolution. The number of classified NiI lines has increased from 1071 to 1996. 289 of the lines have been resolved in 2-4 isotope components. The term system derived from the observations comprises 286 energy levels. The term structure and the coupling conditions have been studied by means of ab initio and parametric theory.

Experimental branching fractions (BFs) of Mo II, ranging in wavelength from 1970 to 4370 Å, have been measured from intensity calibrated spectra recorded with the Lund UV Fourier transform spectrometer (FTS). Radiative lifetimes for 10 levels have been measured using the method of laser-induced fluorescence (LIF). Combining BFs with new as well as previously measured lifetimes, 16 in total, oscillator strengths of 91 lines were derived. Seven transitions are resonance lines involving the ground state. The BF results are compared with calculations made with the Cowan code and the f-values are compared with previously published data. Improved wavelengths from an ongoing term analysis are also reported.

New experimental branching fractions and transition probabilities are reported for 56 transitions in Fe II. The branching fractions are measured with a Fourier transform spectrometer and also with a highresolution grating spectrometer on an optically thin hollow cathode discharge. Highly accurate experimental radiative lifetimes from the recent literature provide the normalization required to convert our branching fractions into absolute transition probabilities. Results are compared with experimental and theoretical values in the literature. Our new transition probabilities will establish the absolute scale for relative absorption oscillator strengths of vacuum ultraviolet lines measured using a new high-sensitivity absorption experiment at the University of Wisconsin.

The indium spectrum emitted from a hollow cathode discharge has been recorded using a Fourier transform spectrometer. Accurate wavelengths have been determined for 54 In II lines, and improved In II energy levels have been derived. The hyperfine structure of 42 lines has been analysed, yielding hyperfine constants A and B for 23 In II levels. The spin-forbidden In I transition 5s25p 2P-5s5p2 4P has also been analysed and absolute wavelengths, hyperfine constants A and B and improved energy level values are reported.

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The quality of astronomical spectroscopic data now available is so high that interpretation and analysis are often limited by the uncertainties of the laboratory data base. In particular, the limit with which space–time variations in the fine structure constant α can be constrained using quasar spectra depends on the availability of more accurate laboratory rest wavelengths. We recently measured some transitions in magnesium by high‐resolution Fourier transform spectroscopy for this purpose, and we now report measurements on some ultraviolet resonance lines of Zn ii (2062 and 2026 Å), Cr ii (2066, 2062 and 2056 Å) and Ni ii (1751, 1741, 1709 and 1703 Å). Apart from the last line, which is very weak, the uncertainty of these measurements is 0.002 cm−1 (0.08 må) for the lines around 2000 Å and 0.004 cm−1 (0.12 må) for the lines around 1700 Å.