Study of Radiation Widths and Neutron Strength Functions of Dy Isotopes

Abstract

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 \ifmmode\pm\else\textpm\fi{} 0.15, 2.3 \ifmmode\pm\else\textpm\fi{} 0.5, 1.7 \ifmmode\pm\else\textpm\fi{} 0.2, and 1.2 \ifmmode\pm\else\textpm\fi{} 0.5, all in units of ${10}^{\ensuremath{-}4}$. The corresponding average total radiation widths of Dy isotopes are found to be 114 \ifmmode\pm\else\textpm\fi{} 10, 155 \ifmmode\pm\else\textpm\fi{} 15, 109 \ifmmode\pm\else\textpm\fi{} 8, and 55 \ifmmode\pm\else\textpm\fi{} 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.