A new analysis procedure to extract fusion excitation function with large beam energy dispersions: application to the ⁶Li+¹²⁰Sn and ⁷Li+¹¹⁹Sn

¹ INFN, Laboratori Nazionali del Sud, via S. Sofia 62, I-95123
² School of Physics and Astronomy, University of Edinburgh, JCMB, Mayfield Road, Edinburgh EH9 3JZ, UK
³ Dipartimento di Fisica ed Astronomia, Universitá di Catania, via S. Sofia 64, I-95123 Catania, Italy
⁴ Instituto de Física, Universidade Federal Fluminense, Avenida Litoranea s/n, Gragoatá, Niterói, Rio de Janeiro 24210-340, Brazil
⁵ INFN, Sezione di Padova, Via F. Marzolo 8, 35131, Padova, Italy
⁶ TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3, Canada
⁷ Ruđer Bošković Institute Bijenička cesta 54, HR-10000 Zagreb, Croatia

^* e-mail: dipietro@lns.infn.it

Published online: 22 November 2017

Abstract

In the present paper it is described an analysis procedure suited for experiments where cross-sections strongly varying with energy are measured using beams having large energy dispersion. These cross-sections are typically the sub-barrier fusion excitation function of reactions induced by radioactive beams. The large beam energy dispersion, typical of these experiments, can lead to ambiguities in the association of the effective beam energy to the reaction product yields and consequently to an error in the determination of the excitation function. As a test case, the approach is applied to the experiments ⁶Li+¹²⁰Sn and ⁷Li+¹¹⁹Sn measured in the energy range 14 MeV ≤ E_c.m. ≤28 MeV. The complete fusion cross sections are deduced from activation measurements using the stacked target technique. The results of these experiments, that employ the two weakly-bound stable Li isotopes, show that the complete fusion cross sections above the barrier are suppressed of about 70% and 85% with respect to the Universal Fusion Function, used as a standard reference, in the ⁶Li and ⁷Li induced reactions respectively. Moreover, the excitation functions of the two systems at energies below the barrier, do not show significant differences, despite the two systems have different n-transfer Q_value.