Photon strength function and level density in neutron rich Fe isotopes*

In nuclei away from stability, there is a lack of information on nuclear level densities and gamma-ray strength functions. In some stable isotopes, for example, in the Fe-Cd region, an unexpected increase in the gamma-decay probability has been observed. This leads to an up-bend in the gamma-ray strength function (gSF) below ~4 MeV, which has a significant influence on extracted neutron-capture rates. It is unknown how the gSF behaves for neutron-rich nuclei. Furthermore, the nuclear level density (NLD) and gSF are critical components in constraining neutron-capture rates through the indirect beta-Oslo method. Neutron-capture rates are a crucial for models of the r-process, which is presumed responsible for creating over half the isotopes heavier than iron, and measurements are outside the current realm of capability for experimental facilities. At the NSCL, we populated excited states via beta-decay for the neutron-rich nucleus Fe-64, a candidate for the up-bend in the gamma-ray strength function. Gamma rays were recorded with the Summing Na(I) (SuN) segmented total absorption spectrometer, which allows us to simultaneously extract the NLD and gSF. Results will be presented for the $gamma$SF and level density of Fe-64.