This element was discovered by A. Cronstadt in Stockholm, Sweden in 1751. The name alludes to the mineral called by German miners Kupfernikel (false copper).
NiI 7.6 eV, NiII 18.2 eV, NiIII 35.2 eV, NiIV 54.9 eV, NiV 75.4 eV, NiVI 107.8 eV, NiVII 132.7 eV.
Absorption lines of NiI
NiI (see for example 4714) appears in A-type stars and grows monotonically toward later types. The luminosity effect is positive (see also the line at 5435).
In the infrared one of the most intense lines is 7555(187). In the sun, W(7555) = 0.107.
Emission lines of NiI
Lines of M.30 and 33 are seen in emission in T Tau stars Joy 1945) and in at least one supernova (Arnett et al. 1989). Jennings et al. (1993) also observed [NiI] at 11.3 µm in the supernova 1987A.
Absorption lines of NiII
NiII is seen from late B-type on and disappears in G-type stars. A positive luminosity effect exists.
Emission lines of NiII
Lines of [Ni II] appear in emission in one VV Cep star (Rossi et al. 1992), in the luminous blue variable eta Car (Thackeray 1953) and in the supernova 1987A (Arnett et al. 1989) Lines of [NiII] are also seen in one typical B[e] star (Swings 1973).
Absorption lines of NiI V and NiV
NiIV and NiV have been found by Dean and Bruhweiler (1985) in the spectra of some O-type stars.
Forbidden lines of higher ionization stages
Lines of NiXII (4231), XIII, XV(6701, 8024) and XVI (3601) with ionization energies between 318 and 455 eV are seen in the spectrum of the solar corona (Zirin 1988) and in at least one nova (Joy and Swings 1945).
Behavior in non-normal stars
Ni seems to be weak in Ap stars of the Hg-Mn subgroup (Takada-Hidai 1991).
Sneden et al. (1991) found that Ni behaves in a manner similar to that of Fe in metal-weak disk and halo stars. Wheeler et al. (1989) found the same behavior for globular cluster stars. Ni can thus be regarded as a typical representative of the metals.
Ni has five stable isotopes, Ni 58, 60, 61, 62 and 64, which in the solar system occur with 68%, 26%, 1%, 4% and 1% abundances respectively. Besides these isotopes there also exist four unstable isotopes, the longest lived, Ni59, having a half life of 8 × 104 years.
Ni 58, 61 and 62 can be produced by explosive nucleosynthesis and by nuclear statistical equilibrium. Ni61 is produced by these processes and by carbon burning. Ni62 is produced by explosive nucleosynthesis, by statistical equilibrium and by oxygen burning. Ni60 is produced only by the statistical equilibrium process and Ni64 only by explosive nucleosynthesis.
Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.