Measurement of $2s$ and $3s$ electron-spin densities in iron metal and ${\mathrm{Fe}}_2$${\mathrm{O}}_3$

The $2s$ and $3s$ electron-spin densities at the nuclear site of the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ nucleus in iron metal and ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ were measured by a new technique combining the Mössbauer effect with electron spectroscopy. The ratios of wave functions at the nucleus $\frac{{\left|{\Psi }_{\mathrm{ns}}^{\uparrow }\mathrm{}\right(0\left)\right|}^2}{{\left|{\Psi }_{\mathrm{ns}}^{\downarrow }\mathrm{}\right(0\left)\right|}^2}$ for $2s$ and $3s$ electrons were measured for iron metal and ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$, and were found to agree in sign and order of magnitude with theoretical calculations of the core-polarization contributions to the magnetic hyperfine interactions.