Measurement of fusion excitation function for7Li+64Ni near the barrier

Md Moin Shaikh,R G Pillay,S Saha,S Rajbanshi,Subinit Roy,V Nanal,A Shrivastava,A Mukherjee,S Pal,M K Pradhan,P Basu,V Greco,M La Cognata,C Spitaleri,F Rizzo,S Pirrone

doi:10.1051/epjconf/201611708020

Abstract

Total fusion (TF) excitation function has been measured for the system 7 Li + 64 Ni at the energies near the Coulomb barrier of the system. The evaporation residue (ER) cross sections have been estimated through the online detection of characteristic γ-rays of the ERs. The summed ER cross sections yielding the experimental TF cross section have been compared with the theoretical one dimensional barrier penetration model (1DBPM) prediction. The measured and the model cross sections are very close to each other at above barrier energies. However, an enhancement of the experimental TF cross section with respect to the 1DBPM prediction is observed at below barrier energies. Coupled channels (CC) calculation with inelastic excitations alone could not explain the enhancement. The origin of the enhancement is identified as due to the enhanced population of the αxn channels. A complete understanding of the effect of direct reaction channels like, breakup or transfer followed by breakup on fusion of weakly bound systems at near barrier energies is of primary importance [1, 2]. In case of fusion of weakly bound stable projectiles like, 6 Li (Sα =1 .47 MeV), 7 Li (Sα =

Highlights

2.47 MeV) and 9Be (Sn =1.67 MeV), two principal observations are: the suppression of complete fusion (CF) cross section with respect to one dimensional barrier penetration model (1DBPM) prediction at the above barrier energies and the enhancement of fusion cross section at below barrier energies [3,4,5,6,7,8,9,10,11,12]
The observable cross section is known as total fusion (TF) cross section [10,13,14,15]
Very recently our group has reported the extraction of CF excitation function from the measured TF excitation function for the system 6Li+ 64Ni where the target has six additional neutrons over the N = 28 closed sub-shell [12]

Summary

Introduction

2.47 MeV) and 9Be (Sn =1.67 MeV), two principal observations are: the suppression of complete fusion (CF) cross section with respect to one dimensional barrier penetration model (1DBPM) prediction at the above barrier energies and the enhancement of fusion cross section at below barrier energies [3,4,5,6,7,8,9,10,11,12]. Though the measurements of fusion cross sections for these projectiles show consistent behavior of suppression at above barrier energies for heavy mass targets, the evolution of the behavior as the target mass decreases needs to be clearly understood. The problem in the collision with lower medium target is to experimentally distinguish the CF cross sections from other reaction processes producing the same residues.

Results

Conclusion