Eur. Phys. J. A (2019) 55: 22
https://doi.org/10.1140/epja/i2019-12695-4

Regular Article - Experimental Physics

Isospin influence on fragments production in ⁷⁸Kr + ⁴⁰Ca and ⁸⁶Kr + ⁴⁸Ca collisions at 10 MeV/nucleon

¹ INFN, Sezione di Catania, I-95123, Catania, Italy
² Dipartimento di Fisica e Astronomia, Università di Catania, I-95123, Catania, Italy
³ INFN, Sezione di Napoli, I-80126, Napoli, Italy
⁴ Dipartimento di Fisica “Ettore Pancini”, Università di Napoli Federico II, I-80126, Napoli, Italy
⁵ Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università di Messina, I-98166, Messina, Italy
⁶ INFN, Laboratori Nazionali del Sud, I-95123, Catania, Italy
⁷ Joint Institute for Nuclear Research, 141980, Dubna, Russia
⁸ Institute of Nuclear Physics, 702132, Tashkent, Uzbekistan
⁹ Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, CNRS-IN2P3, UMR7178, F-67037, Strasbourg, France
¹⁰ Institut de Physique Nucleaire, IN2P3-CNRS, Université Paris-Sud, F-91406, Orsay Cedex, France
¹¹ Centro Siciliano Fisica Nucleare e Struttura della Materia, I-95123, Catania, Italy
¹² Università degli Studi di Enna, “Kore”, I-94100, Enna, Italy
¹³ Heavy Ion Laboratory, University of Warsaw, Warsaw, Poland

^* e-mail: sara.pirrone@ct.infn.it

Received: 25 July 2018
Accepted: 18 January 2019
Published online: 20 February 2019

Abstract

In heavy ion collisions at low energy (E/A < 10–15 MeV/nucleon) the N/Z ratio in the entrance channel is closely related to the isospin degree of freedom and can influence the reaction mechanisms and consequently the production of the fragments in the exit channel. We analyse the fragment production cross sections in the reactions ⁸⁶Kr + ⁴⁸Ca and ⁷⁸Kr + ⁴⁰Ca , at the laboratory energy of 10 MeV/nucleon. The experiment was conducted at the INFN Laboratori Nazionali del Sud in Catania, by using the detector CHIMERA. For the two reactions, elastic scattering measurements are performed to extract the normalization factor used to evaluate the absolute cross sections. Velocity and energy spectra, mass and charge distributions, as well as dynamic features of reaction products, are studied. The study of the characteristics of mass and charge distributions, energy and velocity spectra of the reaction products shows mainly a relaxed component, related to fusion reaction followed by evaporation or binary decay. Nevertheless signals ascribable to a non equilibrated component are present. Structure effects are evident in the staggered shape of emitted fragments cross sections and are more pronounced in the neutron poor system. The analysis highlights clear differences for the two systems in the contributions arising from different reaction mechanisms. Besides, a study of the overall influence from the entrance channel energy is performed. Comparisons to DNS (DiNuclear System) and GEMINI++ models are reported. The data analysis indicates a slightly higher fusion-evaporation cross section and a strongly pronounced probability of fission-like processes for the neutron poor system with respect to the neutron rich one. The neutron enrichment seems thus to limit the formation of the composite system and to inhibit the fission decay channel.