Core Polarization inCr53

Theoretical and experimental values for the contribution of core polarization to the hyperfine structure of excited states of ${\mathrm{Cr}}^{53}$ are compared. A theory is developed for extracting the core contributions to the magnetic field from the measured hyperfine constants. It is necessary to take account of configuration interaction with an actual configuration of unpaired $s$ electrons. A value of -525 000 G is deduced for the magnetic field at the nucleus produced by core polarization. The minus sign indicates that this field is antiparallel to the net spin of the atom. This is compared with theory and with the results of other experiments. Corrections due to relativity, the second-order Zeeman effect, and the breakdown of $\mathrm{LS}$ coupling are considered.