Verification of detailed balance for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>γ</mml:mi></mml:math> absorption and emission in Dy isotopes

Abstract

The photoneutron cross sections of $^{162,163}\mathrm{Dy}$ have been measured for the first time in an energy region from the neutron threshold (${S}_{n}$) up to $\ensuremath{\approx}13\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. The $(\ensuremath{\gamma},n)$ reaction was induced with quasimonochromatic laser Compton-scattered $\ensuremath{\gamma}$ rays, produced at the NewSUBARU laboratory. The corresponding $\ensuremath{\gamma}$-ray strength functions ($\ensuremath{\gamma}\mathrm{SF}$) have been calculated from the photoneutron cross sections. The data are compared to reanalyzed $\ensuremath{\gamma}\mathrm{SFs}$ of $^{160\text{--}164}\mathrm{Dy}$, which are measured below ${S}_{n}$. The excellent agreement with the photoneutron data at ${S}_{n}$ confirms the principle of detailed balance. Thus, a complete $\ensuremath{\gamma}\mathrm{SF}$ is established covering in total the energy region of $1\ensuremath{\le}{E}_{\ensuremath{\gamma}}\ensuremath{\le}13$ MeV. These mid-shell well-deformed dysprosium isotopes all show scissors resonances with very similar structures. We find that our data predict the same integrated scissors strength as $(\ensuremath{\gamma},{\ensuremath{\gamma}}^{\ensuremath{'}})$ data when integrated over the same energy range, which shows that the scissors mode very likely is consistent with the generalized Brink hypothesis. Finally, using the $\ensuremath{\gamma}\mathrm{SFs}$ as input in the reaction code talys, we have deduced radiative neutron-capture cross sections and compared them to direct measurements. We find a very good agreement within the uncertainties, which gives further support to the experimentally determined $\ensuremath{\gamma}\mathrm{SFs}$.