Neutron Resonance Parameters of the Erbium Isotopes

Neutron resonance parameters, $s$-wave strength functions, level densities, and radius parameters for ${\mathrm{Er}}^{162}$, ${\mathrm{Er}}^{164}$, ${\mathrm{Er}}^{166}$, ${\mathrm{Er}}^{167}$, and ${\mathrm{Er}}^{168}$ have been determined from total neutron cross-section measurements. Average cross-section measurements for ${\mathrm{Er}}^{162}$, ${\mathrm{Er}}^{164}$, and ${\mathrm{Er}}^{167}$ have been analyzed to determine neutron strength functions in the keV region, and the results are compared to those derived from the low-energy resonance-parameter data. A spin cutoff factor $\sigma$ of 2.5±0.8 is derived from a comparison of the level densities of ${\mathrm{Er}}^{162}$, ${\mathrm{Er}}^{164}$, and ${\mathrm{Er}}^{167}$. The thermal-neutron total cross sections were measured for ${\mathrm{Er}}^{168}$ and ${\mathrm{Er}}^{164}$, and the paramagnetic scattering cross section for ${\mathrm{Er}}^{168}$ was determined to be 26.1±2.5 b.