Abstract
The technique of self absorption has been applied for the first time to study the decay pattern of low-lying dipole states of 140Ce. In particular, ground-state transition widths Γ0 and branching ratios Γ0Γ 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 Γ0. 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 140Ce was conducted at the bremsstrahlung facility of the superconducting Darmstadt electron linear accelerator S-DALINAC. In total, the self-absorption and, thus, Γ0 were determined for 104 excited states of 140Ce. The obtained results are presented and discussed with respect to simulations of γ cascades using the DICEBOX code.
Highlights
Atomic nuclei represent enormously complex quantum objects
The self absorption was determined for 104 dipole excited states of 140Ce in the energy range between 3.5 MeV and
A pioneering self-absorption experiment was applied to determine the ground-state transition width 0 of states contributing to the Pygmy Dipole Resonance (PDR) directly in a model-independent way
Summary
Atomic nuclei represent enormously complex quantum objects. Their quantum states can correspond to collective modes, to noncollective single-particle excitations or to mixtures of both. Universities National Laboratory (TUNL) in Durham, NC, USA gave experimental insight in mean decay properties of dipole excited states in the energy region of the PDR [12,19,20,21,22,23]. All of these measurements demonstrate that the decay via intermediate states cannot be neglected, the data do not answer the question how individual states behave. Afterwards, the results are discussed and compared to simulations exploiting the DICEBOX code [26]
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