Abstract
The dynamical dipole mode was investigated in the mass region of the 192 Pb compound nucleus, by using the 40 Ca + 152 Sm and 48 Ca + 144 Sm reactions at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion-evaporation and fission events were studied simultaneously for thefirst time. Our results show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously, however, its yield is lower than that expected within BNV calculations.
Highlights
1 Introduction In N/Z asymmetric heavy-ion reactions, it is possible to excite a collective dipole oscillation that can develop along the symmetry axis of the dinuclear system [1,2,3]. This oscillation, called “dynamical dipole mode" (DD throughout the text), decays emitting prompt dipole γ-rays, in addition to those coming from the Giant Dipole Resonance (GDR) thermally excited in the hot compound nucleus (CN)
The fusion-evaporation residues were detected by four position sensitive Parallel Plate Avalanche Counters (PPACs) placed symmetrically around the beam direction at 70 cm from the target at θ = 7◦ and subtending 7◦ in θ
Down-scaled single events together with coincidence events between at least one fired BaF2 scintillator and a PPAC for evaporation events were collected during the experiment
Summary
In N/Z asymmetric heavy-ion reactions, it is possible to excite a collective dipole oscillation that can develop along the symmetry axis of the dinuclear system [1,2,3]. The DD radiation presents i) a lower centroid energy than that of a statistical GDR built in a spherical nucleus of similar mass due to the high deformation of the emitting source [2, 3] ii) an anisotropic angular distribution with respect to the beam axis because the oscillation is confined in the reaction plane [4] and iii) a γ yield that is predicted to depend on both the beam energy and the reaction dynamics [3].
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