Attempting to Close the Loop on the Oslo Technique at 198Au: Constraining the Nuclear Spin Distribution

From simultaneous R-matrix analysis of new and previous neutron total- and capture-cross-section data, we obtained total radiation widths, Γγ, for 77 197Au + n resonances. Γγ distributions calculated according to the nuclear statistical model using published Oslo nuclear level density and photon strength functions for 198Au are too narrow and too close together for the two s-wave spins compared to our new data. The calculation can be brought into agreement with the data by substantial modifications to the spin distribution in 198Au as a function of excitation energy. As far as we know, the spin distribution currently is otherwise poorly constrained. The modified spin distribution changes the shapes of the NLD and PSF extracted using the Oslo technique and so could have broad implications.