2019 Impact factor 2.176
Hadrons and Nuclei
Eur. Phys. J. A 16, 423-435 (2003)
DOI: 10.1140/epja/i2002-10114-9

Pre-equilibrium dipole strength in charge asymmetric peripheral heavy-ion reactions

D. Pierroutsakou1, M. Di Toro2, 3, F. Amorini2, 3, V. Baran3, 4, A. Boiano1, A. De Rosa1, 5, A. D'Onofrio6, 1, G. Inglima1, 5, M. La Commara1, 5, A. Ordine1, N. Pellegriti2, 3, F. Rizzo2, 3, V. Roca1, 5, M. Romoli1, M. Sandoli1, 5, M. Trotta1, 5 and S. Tudisco2, 3

1  INFN, Sezione di Napoli, Napoli, Italy
2  Università di Catania, Dipartimento di Fisica, Catania, Italy
3  INFN, Laboratorio Nazionale del Sud, Catania, Italy
4  NIPNE-HH and Bucharest University, Romania
5  Università di Napoli "Federico II", Dipartimento di Scienze Fisiche, Napoli, Italy
6  Seconda Università di Napoli, Dipartimento di Scienze Ambientali, Napoli, Italy

pierroutsakou@na.infn.it

(Received: 26 September 2002 / Revised version: 11 November 2002 / Published online: 6 March 2003)

Abstract
We report on the results obtained from the study of the $\chem{^{32}S}$ + 64 Ni and $\chem{^{32}S}$ + $\chem{^{58}Ni}$ peripheral reactions at incident energies $E_{\rm lab} = 288$ MeV and $E_{\rm lab} = 320$ MeV, respectively. High-energy $\gamma $ -rays were detected in an array of 8 seven-pack BaF 2 clusters. Coincidence with complex fragments detected in 12 three-stage telescopes ensured the selection of peripheral reaction events. All of the relevant reaction parameters were kept constant with the exception of the different initial dipole moment caused by the different entrance channel charge asymmetry. While for quasi-elastic events no N/Z effect was observed in the differential $\gamma $-ray multiplicities of the two reactions, for deep-inelastic events a larger dipole $\gamma $-ray emission occurs during the more N/Z asymmetric reaction. A theoretical interpretation based on a collective Bremsstrahlung analysis of the reaction dynamics is presented.

PACS
25.70.-z - Low and intermediate energy heavy-ion reactions.
24.30.Cz - Giant resonances.
23.20.-g - Electromagnetic transitions.
25.70.Lm - Strongly damped collisions.

© Società Italiana di Fisica, Springer-Verlag 2003