Nuclear dipole response of ⁵⁶Fe using photon scattering

We recently performed a nuclear resonance fluorescence experiment in ⁵⁶Fe with 100% linearly polarized photons for incident beam energies below the neutron separation energy at the High-Intensity Gamma-ray Source (HIγS) facility at Triangle Universities Nuclear Laboratory (TUNL). From the observed dipole states and their decay pattern and transition strengths, we will deduce the gamma-strength function of ⁵⁶Fe [1]. With the upgrade of the high-efficiency clover detector array and the increased γ-ray flux at HIγS, we also aim to study the low-energy primary γ-ray transitions induced by incident photon beams using coincidence mode. In this talk, we will give an overview of the experiment and present the preliminary results on the dipole strength distribution in ⁵⁶Fe below the neutron separation energy, as well as the comparison with literature data [2] and theoretical calculations based on the quasi-particle phonon model [3].

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

[1] A.P. Tonchev et al., Phys. Rev. Lee. 104 072501 (2010).

[2] T. Shizuma, et al., Phys. Rev. C 87, 024301 (2013).

[3] N. Tsoneva and H. Lenske, Physics of Atomic Nuclei 79, 885 (2016).