Prompt dipole radiation in fusion reactions

Abstract

The prompt γ -ray emission is investigated in the 16 A MeV energy region by means of the 36,40Ar + 96,92Zr fusion reactions leading to a compound nucleus in the vicinity of 132Ce. The dynamical nature\ud of this radiation is confirmed. We show that the prompt γ radiation has an angular distribution pattern\ud consistent with a dipole oscillation along the symmetry axis of the dinuclear system. The data are\ud compared with calculations based on a collective bremsstrahlung analysis of the reaction dynamics

Dynamical Dipole mode in the40,48Ca +152,144Sm fusion reactions at 11 MeV/nucleon

“…Our data therefore suggest that the DD γ-emission time scale is confined at the beginning of the reaction, in agreement with our previous results [8] for evaporation events and with theoretical expectations [4]. By taking into account the an DD γ-ray angular distribution (a 2 = -1) for evaporation events and the response function of the experimental setup, the DD yield, integrated over energy and over angle, is (1.2 ± 0.2)*10 −3 .…”

“…It is interesting to note that E DD is lower than the centroid energy of the GDR built on the ground state of a nucleus of similar mass, E GDR = 14 MeV. This result confirms the high deformation of the emitting source at the moment of the DD γ emission, in agreement with expectations [2,3] and with our previous works [7,8].…”

“…The analysis demonstrated that the two reactions lead to the formation of a CN with the same average mass and charge at the same average excitation energy. Hence, as in our previous works [7,8], the only different parameter in the two reactions is the initial charge asymmetry. Therefore any difference in the γ-ray emission between the two reactions can be related to this quantity.…”

“…The existence of the DD mode has been probed in deep inelastic and fusion-evaporation heavy-ion collisions [5][6][7][8][9]. In these measurements, an excess of γ-rays was observed in the GDR energy region for a charge asymmetric reaction, with respect to that of a more charge symmetric one forming the same CN at identical conditions [6][7][8] or with respect to statistical model calculations [9].…”

“…In these measurements, an excess of γ-rays was observed in the GDR energy region for a charge asymmetric reaction, with respect to that of a more charge symmetric one forming the same CN at identical conditions [6][7][8] or with respect to statistical model calculations [9]. This γ excess was attributed to the decay of the predicted DD.…”