Dipole strength in 78 Se below the neutron separation energy from a combined analysis of 77 Se(n, γ) and 78 Se(γ , γ') experiments

The dipole strength function and the nuclear level density of the compound nucleus 78Se were studied in a combined analysis of a cold neutron capture experiment on 77Se performed at the research reactor in Budapest and a photon-scattering experiment on 78Se performed at the electron linear accelerator ELBE with bremsstrahlung produced at a kinetic electron energy of 11.5 MeV. In the combined analysis we developed the extreme statistical code γ DEX for the simulation of radiative cascade deexcitations occurring in neutron capture and photon scattering. Comparisons of experimental and simulated neutron capture spectra allow us to estimate a temperature of T = 900 keV for the level density according to the constant-temperature model for 78Se. Using γ DEX, we were also able to estimate ground-state branching ratios and intensities of inelastic transitions for states in 78Se excited via photon scattering. In this way, we derived the photoabsorption cross section from 4 MeV up to the neutron separation energy from the measured photon-scattering data. The results obtained match the photoabsorption cross section derived from (γ , n) measurements and show an enhancement of dipole strength around 9 MeV.