Zeeman Effect in the Arc Spectrum of Nickel

Measurements of the Zeeman patterns for 113 lines between $\lambda 5500$ and $\lambda 3000$ are presented, from which $g$-factors for 61 terms are calculated. The $g$-sum rule holds for configuration $d^{9}s$ and for $d^{8}s\left({}_{}{}^2{}_{}{}^{}F\right)·4p$, but not for $d^9·4p$ or $d^{8}s\left({}_{}{}^4{}_{}{}^{}F\right)·5s$. It does hold for $d^9·4p$ and the quintet terms of $d^{8}s\left({}_{}{}^4{}_{}{}^{}F\right)·4p$ taken together, indicating that these groups interact. It is surmised that $d^{8}s\left({}_{}{}^4{}_{}{}^{}F\right)·5s$ is perturbed by $d^9·4d$. The theory of two-electron systems fits $d^{9}s$ very well. It works fairly well with $d^8{s}^2$, but breaks down when applied to $d^9·4p$, probably because of increased importance of the magnetic interactions which are neglected in the theory.