5 Conclusion

Extensive radiative calculations for Ni II are presented which are expected to be applicable to a variety of astrophysical problems such as the calculation of improved opacities, non-LTE models, and spectroscopic interpretation of Ni II spectra. The present calculations include a large number of target terms and therefore exhibit resonance structures absent from previous calculations. Also presented are oscillator strengths for $23\,738$ dipole allowed transitions among the terms in Ni II.

The current f-values and the level radiative lifetimes derived from them agree rather well with available experimental measurements. In contrast, there are significant differences with respect to previous calculations by Kurucz and coworkers using semiempirical methods. These differences reach factors of two to four for transitions commonly used in Ni II abundance determinations in the ISM. Thus, previous estimates of nickel depletion in the ISM may be overestimated. The present data is also expected to have important effects on the Ni II opacities.

All radiative data reported here will be included in TOPbase at CDS (Cunto et al. 1993). These data can also be accessed electronically via Internet by request to the authors.

Acknowledgements

I like to thank Dr. J.A. Fedchal and Dr. J.E. Lawler for providing me with their experimental measurements prior to publication. I also like to thank Prof. A.K. Pradhan and Prof. David G. Hummer for useful comments and reading of the manuscript. The computations were carried out on the CRAY J94 at the NASA Center for Computational Sciences and the CRAY T3E at the High Performance Computing and Communications Program at NASA/GSFC.