Low-energy electric dipole response in 120 Sn

Abstract

The electric dipole strength distribution in 120Sn has been extracted from proton inelastic scattering experiments at Ep=295 MeV and at forward angles including 0°. It differs from the results of a Sn120(γ,γ′) experiment and peaks at an excitation energy of 8.3 MeV. The total strength corresponds to 2.3(2)% of the energy-weighted sum rule and is more than three times larger than what is observed with the (γ,γ′) reaction. This implies a strong fragmentation of the E1 strength and/or small ground state branching ratios of the excited 1− states.