Determining (n,$\gamma$) and (n,2n) cross sections for radioactive isotopes using surrogate reactions

Direct measurements of neutron-reaction cross sections on unstable nuclei are extremely challenging due to the difficulties associated with radioactive targets and neutron beams. The surrogate reaction method, an indirect approach which uses a combination of reaction modeling and experimentally-measured decay probabilities, is being used to determine (n,$\gamma$) and (n,2n) cross sections for short-lived nuclei where the compound nucleus of interest can be created through light-ion reactions on stable or long-lived targets. The STARS/LiBerACE silicon and germanium detector arrays were used to detect light ions and $\gamma$-rays in coincidence. Techniques are being explored to take into account the differences in angular momentum in the surrogate and neutron-induced reactions. Results for gadolinium and yttrium isotopes will be presented and some of the challenges associated with this technique will be discussed.