Direct determination of ground-state transition widths of low-lying dipole states in 140Ce with the self-absorption technique

Abstract The technique of self absorption has been applied for the first time to study the decay pattern of low-lying dipole states of 140 Ce. In particular, ground-state transition widths Γ 0 and branching ratios Γ 0 Γ to the ground state have been investigated in the energy domain of the pygmy dipole resonance. Relative self-absorption measurements allow for a model-independent determination of Γ 0 . Without the need to perform a full spectroscopy of all decay channels, also the branching ratio to the ground state can be determined. The experiment on 140 Ce was conducted at the bremsstrahlung facility of the superconducting Darmstadt electron linear accelerator S-DALINAC. In total, the self-absorption and, thus, Γ 0 were determined for 104 excited states of 140 Ce. The obtained results are presented and discussed with respect to simulations of γ cascades using the DICEBOX code.