Prompt dipole -ray emission in fusionlike heavy-ion reactionsD. Pierroutsakou1, A. Boiano1, A. De Rosa1, 2, M. Di Pietro1, G. Inglima1, 2, M. La Commara1, 2, Ruhan Ming3, 4, B. Martin1, 2, R. Mordente1, A. Ordine1, F. Rizzo5, 6, V. Roca1, 2, M. Romoli1, M. Sandoli1, 2, F. Soramel7, 8, L. Stroe9, M. Trotta1, 2 and E. Vardaci1, 2
1 INFN, Sezione di Napoli, Napoli, Italy
2 Università di Napoli "Federico II", Dipartimento di Scienze Fisiche, Napoli, Italy
3 China Institute of Atomic Energy, Beijing, PRC
4 INFN, Laboratori Nazionali di Legnaro, Padova, Italy
5 Università di Catania, Dipartimento di Fisica, Catania, Italy
6 INFN, Laboratorio Nazionale del Sud, Catania, Italy
7 Università di Udine, Dipartimento di Fisica, Udine, Italy
8 INFN, Sezione di Udine, Udine, Italy
9 NIPNE, Bucharest, Romania
(Received: 21 October 2002 / Revised version: 23 November 2002 / Published online: 1 April 2003)
The 32S + 100Mo and 36S + 96Mo fusionlike reactions were studied at incident energy of MeV and 320 MeV, respectively, with the aim of probing the influence of the entrance channel charge asymmetry on the dipole -ray emission. The excitation energy and spin distribution of the compound nucleus created in these reactions were identical, the only difference being associated with the unequal charge asymmetry of the two entrance channels. High-energy -rays were detected in an array of 9 seven-pack BaF 2 clusters. Coincidence with fusionlike residues detected in four PPAC ensured the selection of central reaction events. By studying the differential -ray multiplicity associated with the two reactions it was shown that the dipole strength excited in the compound nucleus increases with the entrance channel charge asymmetry. From the linearized spectra, the increase of the GDR -ray intensity was found to be for the more charge asymmetric system. The results are discussed and compared with those of previous data obtained at different incident energies.
25.70.-z - Low and intermediate energy heavy-ion reactions.
24.30.Cz - Giant resonances.
23.20.-g - Electromagnetic transitions.
25.70.Gh - Compound nucleus.
© Società Italiana di Fisica, Springer-Verlag 2003