Verification of detailed balance for γ absorption and emission in Dy isotopes

The photoneutron cross sections of 162,163Dy have been measured for the first time in an energy region from the neutron threshold (Sₙ) up to ≈130.16em0exMeV. The (γ,n) reaction was induced with quasimonochromatic laser Compton-scattered γ rays, produced at the NewSUBARU laboratory. The corresponding γ-ray strength functions (γSF) have been calculated from the photoneutron cross sections. The data are compared to reanalyzed γSFs of ¹⁶⁰⁻⁻¹⁶⁴Dy, which are measured below Sₙ. The excellent agreement with the photoneutron data at Sₙ confirms the principle of detailed balance. Thus, a complete γSF is established covering in total the energy region of 1≤E_γ≤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 (γ,γ^') 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 γSFs 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 γSFs.