Constraining the calculation of 234,236,238U(n,γ) cross sections with measurements of the γ-ray spectra at the DANCE facility

The cross section for neutron capture in the continuum region has been difficult to calculate accurately. Previous results for U-238 show that including an M1 scissors-mode contribution to the photon strength function resulted in very good agreement between calculation and measurement. This paper extends that analysis to U-234,U-236 by using gamma-ray spectra measured with the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center to constrain the photon strength function used to calculate the capture cross section. Calculations using a strong scissors-mode contribution reproduced the measured gamma-ray spectra and were in excellent agreement with the reported cross sections for all three isotopes.