Study of Radiation Widths and Neutron Strength Functions of Dy Isotopes

Neutron transmission measurements have been carried out for ${\mathrm{Dy}}^{161}$, ${\mathrm{Dy}}^{162}$, ${\mathrm{Dy}}^{163}$, and ${\mathrm{Dy}}^{164}$, employing the fast-chopper facility of the Brookhaven Graphite Research Reactor. The $s$-wave neutron strength functions ($S^0$), resonance parameters, average level spacings, and potential-scattering radii have been determined. The values of the neutron strength functions of ${\mathrm{Dy}}^{161}$, ${\mathrm{Dy}}^{162}$, ${\mathrm{Dy}}^{163}$, and ${\mathrm{Dy}}^{164}$ are 1.85 ± 0.15, 2.3 ± 0.5, 1.7 ± 0.2, and 1.2 ± 0.5, all in units of ${10}^{-4\mathrm{}}$. The corresponding average total radiation widths of Dy isotopes are found to be 114 ± 10, 155 ± 15, 109 ± 8, and 55 ± 3 meV. A correlation between total radiation width and $S^0$ seems to be evident. Furthermore, examination of the present and previous results for the rare-earth isotopes indicates that there is a systematic trend of decrease of $S^0$ with increasing mass number for the even-even target nuclei. Absorption-resonance integrals and thermal cross sections are computed from the resonance parameters and are compared with direct measurements of other experiments.