Advances in the resolution and spectral range of space and ground-based spectrographs have highlighted the need for improved line wavelengths and energy levels. Accurate, laboratory-collected atomic data is therefore vital for the interpretation of astrophysical spectra. Data for the iron group elements is of particular importance, due to their large number of transitions and high abundance.
Nickel has the second highest cosmic abundance of the iron group elements. Its complex atomic structure produces a densely-populated spectrum in the infrared through to the vacuum ultraviolet and spectral lines of singly-ionised nickel (Ni II) are found in a wide variety of astrophysical spectra. Although progress has been made in producing high resolution data for other singly-ionised iron group elements, including Fe II ,V II, Co II and Cr II, the last large-scale analysis of Ni II dates back to 1970 [1].
An order of magnitude increase in the accuracy of Ni II atomic data is now needed for modern astrophysical applications. To achieve the required improvement in transition wavelengths and energy level structure of Ni II, high resolution spectra in the infrared, visible and vacuum ultraviolet have been recorded at Imperial College London and NIST (USA). Both Fourier transform and grating spectroscopy, with Ni-He and Ni-Ne hollow cathode light sources, have been employed. An extensive term analysis is currently underway at Imperial College and we report some preliminary results here.

[1] A. G. Shenstone, J Res Natl Bur Stand Sect A Phys Chem, 74A, 801–855 (1970)