NICKEL Ni Z = 28

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).

Ionization energies
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

Table 1. Equivalent widths of NiI

  4470(86)   4714(98)  

Group V III V Ib

A0 P      
A2     0.02  
A7     0.08  
F0     0.13 0.085(II)
F2       0.112
F4     0.12  
F5     0.155 0.16
F6     0.17  
F8     0.17 0.26
G0 0.088   0.11  
G1     0.23  
G2 0.085   0.21  
S 0.069      
G5 0.107   0.26  
G8 0.117(IV)      
K0     0.31  
K2   0.105 0.34  

Table 2. Equivalent widths of NiI

  5435(70)     5587(70)    

Group V III Ib V III Ib

F5 0.022   0.022      
F8     0.051      
G0     0.125 0.126    
G2 0.041   0.128     0.135
S       0.049    
G5     0.128     0.162
G8     0.151,0.214     0.245
K0   0.110     0.095  
K2     0.173   0.120 0.251
K3     0.190     0.323
K5     0.192     0.380
M0   0.125     0.125  
M2     0.196      
M2.5   0.132     0.132  

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.

Figure 36

Absorption lines of NiII

Table 3. Equivalent widths of NiII

  4067(11)   4362(9)  

Group V I V Ib

B5 0.014 0.22    
B7 0.022      
B9 0.051      
B9.5 0.029,0.036   0.005  
A0   0.l00(Ia)    
A1     0.016,0.038(IV)  
A2     0.024 0.043(Ia)
A3       0.072(Ia)
F2       0.190
F5     0.015 0.055
F8       0.072
S     0.021  

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).

Figure 37

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.