Cross section for the neutron radiative capture on Lu-173 nuclei

We report the measurement of a neutron radiative cross section on a target with a high gamma activity, at the Los Alamos DANCE detector (Detector for Advanced Neutron Capture Experiments) for the first time. The (n, gamma) reaction properties of the unstable Lu-173 isotope were studied. Two experimental campaigns were needed to determine the Lu-173(n, gamma) cross section. They were performed at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source facility. To this end, two targets were produced from an Hf sample using successively proton irradiation and chemical separations. They were composed of Lu-173, (174) Lu, and Lu-175 isotopes. The two measurements were conducted at two-year intervals, taking advantage of the difference of the isotopic decay lifetimes in order to identify resonances from the Lu-173(n, gamma) and Lu-174(n, gamma) reactions. Just over one hundred new resonances were observed, the majority of which come from the Lu-173(n, gamma) reaction. Only a few of them were assigned to the Lu-174(n, gamma) reaction. As regards the Lu-173(n, gamma) reaction, the radiative neutron capture cross section was determined over the energy range from thermal neutron up to 200 eV. The parameters of resonances in the resolved resonance region were extracted with the SAMMY code while calculations with TALYS determined the capture cross section in the unresolved resonances region. At the keV region, we performed standard TALYS calculations as well as other microscopic investigations by substituting the standard TALYS photon strength function by another one from QRPA models.