Study of reactions with the weakly bound projectile ⁹Be with ⁸⁹Y

¹ Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India
² Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai - 400 005, India
³ Departamento de Física Aplicada, Universidad de Huelva, E-21071 Huelva, Spain

^a e-mail: chandani@barc.gov.in

Abstract

With the aim to investigate the influence of the breakup channel on different reaction channels, the elastic scattering and fusion of ⁹Be with the medium mass target ⁸⁹Y has been studied at near barrier energies. Optical model analysis of the elastic data has been carried out and a dispersion relation applied to the real and imaginary potentials to investigate their energy dependence from which the presence of breakup threshold anomaly has been observed. Complete fusion (CF) cross sections, obtained for ⁹Be+⁸⁹Y system, are found to be suppressed by (20 ± 5)% as compared to the coupled-channels calculations without breakup coupling. This observation has been further confirmed by comparing these cross sections with those for the ⁴He+⁹³Nb and ¹²C+⁸⁹Y systems, where fusion is induced by a tightly bound projectile and forms a nearby compound nucleus to that formed by ⁹Be+⁸⁹Y. Results from the breakup coupling done in continuum discretized coupled-channels calculations show that the elastic cross sections thus obtained, which also fit the experimental elastic cross sections, are enhanced compared to the uncoupled calculations which implies a reduction in absorption/fusion cross sections. These enhanced cross sections suggest that the dynamic polarization potential produced due to breakup coupling is repulsive in nature. Thus the effective (bare+polarization) potential around the barrier becomes less attractive leading to the absence of the normal threshold anomaly.