Contact Magnetic-Dipole Hyperfine Structure in3dN4s2Atoms

The experimental value of $\frac{a\left(s\right)\mathrm{}}{\gamma }$, where $a\left(s\right)\mathrm{}$ is the contact part of the magnetic-dipole hyperfine interaction and $\gamma =\frac{{\mu }_I}{I}$, is considered as a function of the number $N$ of $3d$ electrons present. The effects of intermediate coupling and configuration interaction (including core polarization) are allowed for wherever possible in the extraction of $a\left(s\right)\mathrm{}$ from the available experimental data. The resulting curve, which should more accurately describe the variation of the contact hfs with $N$, is considerably smoother than when these refinements are omitted. New experimental results for ${\mathrm{Ni}}^{61}$ are included.