Understanding the Low-Energy Enhancement of the ${\hat{I}}^3$-ray Strength Function of ${}^{56}$Fe

Abstract

A model-independent technique was used to determine the ${\hat{I}}^3$-ray Strength Function (${\hat{I}}^3$SF) of ${}^{56}$Fe down to ${\hat{I}}^3$-ray energies less than 1 MeV for the first time with GRETINA using the $(p,p^{\prime })$ reaction at 16 MeV. No difference was observed in the energy dependence of the ${\hat{I}}^3$SF built on $2^{+}$ and $4^{+}$ final states, supporting the Brink hypothesis. In addition, angular distribution and polarization measurements were performed. The angular distributions are consistent with dipole radiation. The polarization results show a small bias towards magnetic character in the region of the enhancement.