Spectrum and term system of neutral nickel, Ni I

Spectra of nickel, emitted from hollow cathode discharges, have been recorded in the region 1700-55 000 Å (58 800-1800 cm−1). Fourier transform spectrometers were used above 1800 Å, yielding very high accuracy and resolution. The number of classified Ni I 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.